Mechanical Engineering Topics

Abel Flashpoint Apparatus
A petroleum-testing apparatus for determining the flash point.
Abhesive
A substance which prevents two materials sticking together, e.g., teflon on frying pans.
Ablating Material
A material designed to provide thermal protection to a body in a fluid stream through loss of mass.
Abney Level
Hand-held instrument in which angles of steep sights are measured while simultaneously viewing a spirit-level bubble.
Abraded
Pertaining to a surface that has been worn by surface rubbing.
Abrasion
A process where hard particles are forced against and moved along a solid surface.
Abrasion Resistance
The ability of a material to resist surface wear.
Abrasive
A very hard, brittle, heat-resistant substance that is used to grind the edges or rough surfaces of an object.
Abrasive Erosion
Erosive wear caused by the relative motion of solid particles which are entrained in a fluid, moving nearly parallel to a solid surface.
Abrasive Machining
Various grinding, honing, lapping and polishing operations that utilize abrasive particles to impart new shapes, improve finishes and part stock by removing metal or other material.
Abrasive Paper
A paper upon which sand or hard grit has been glued.
Abrasive Wear
A mechanism of wear due to the presence in one or both surfaces of hard particles.
Abrasive Wheel
A grinding wheel composed of an abrasive grit and bonding agent.
Absorbent Filter
A filter medium that holds contaminant by mechanical means.
Absorption Refrigerator
Refrigerator that creates low temperatures by using the cooling effect formed when a refrigerant is absorbed by chemical substance.
Abuse Test
Testing a component or system to the extreme conditions that it will experience in real world operation.
Abut
The action of two gear teeth making contact.
Abutment
A part which stops the motion of another part from proceeding any farther.
Abutting Edge
The side or edge of a panel which joins another panel.
Accelerance
For a point excitation of a mechanical system this is the complex ratio of acceleration to applied force.
Accelerated Life Test
A component test over a shortened timescale that has been designed to represent complete life history.
Accelerator Pedal
A pedal that when pressed is connected to the engine and demands more torque.
Acceptance Test
An examination of a part or its assembly to determine if it meets a prescribed standard.
Access
A way of reaching something that is usually hidden or covered.
Accumulator
A device by which energy or power can be stored.
Acid Cleaning
The process of cleaning components with dilute acid followed by a wash or inhibitor to stop further corrosion.
Acoustic Emission
A measure of integrity of a material determined by sound emission when a material is stressed.
Acoustic Filter Elements
There are a number of different types of acoustic filter elements that are used in many different applications.
Acoustic Streaming
Unidirectional flow currents in a fluid that are due to the presence of sound waves.
Acrylic
Synthetic resin made from acrylic acid or a derivative thereof; acrylics possess the property of transparency and offer flame resistance.
Action
Refers to an effective motion or mechanism as for example the breech action of a gun.
Activated Carbon
Also known as Activated Charcoal.
Activator
Substance that enhances the ability of a flux to remove oxides and other contaminants from surfaces being joined.
Active Iron
The amount of iron in the stator and rotor of a motor.
Actuating System
A mechanical system that supplies and transmits energy for the operation of other mechanisms or systems.
Actuator
A device which controls or operates another device.
Adapter
Any device or contrivance used or designed primarily to fit or adjust one thing to another.
Addendum
That portion of a gear tooth that extends from the pitch circle to the outside diameter.
Adhere
To stick or be glued to something.
Adherence Index
Measure of the adherence of porcelain enamel and ceramic coatings to sheet metal.
Adhesion
The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking action.
Adhesive
A substance capable of holding material together by surface attachment.
Adhesive Tape
A tape with a sticky substance on one side.
Adhesive Wear
Often referred to as galling, scuffing, scoring, or seizing.
Admittance
The ratio of current to voltage, the reciprocal of impedance.
Adsorbent Filter
A filter medium primarily intended to hold soluble and insoluble contaminants on its surface by molecular adhesion.
Aerodynamics
Lists all Aerodynamics topics in the Encyclopaedia
Age Hardening
Usually follows rapid cooling from solution heat treatment temperatures or cold working.
Ageing
A change in the properties of certain metals and alloys that occurs at ambient or moderately elevated temperatures after hot working, heat treatment, or a cold working operation.
Agglomerate
The clustering together of a few or many particles into a larger solid mass.
Aggravated Test
A test in which one or more conditions are set at a more stressful level that the test item will encounter in the field, in order to reduce test time or assure a margin of safety.
Air Bearing
A bearing which uses an air cushion to separate its rotating surfaces.
Air Bleeder
A device for removal of air from fluid line.
Air Breather
A device permitting air movement between atmosphere and the component in/on which it is installed.
Air Entrainment
The incorporation of air in the form of bubbles as a dispersed phase in the bulk liquid.
Air Hammer
A hammer that is powered by compressed air.
Air Lock
An intermediate enclosed chamber of a vacuum or pressure system through which an object may be passed without materially changing the vacuum or pressure of the system.
Air Motor
A device which converts compressed gas into mechanical force and motion.
Air Purge
The removal of undesired matter by replacement with air.
Air Set Cement
A cement that sets through loss of water.
Air Spring
A simple mass on an air spring.
Air Tank
A container which holds air under pressure, normally created by a compressor.
Air Valve
Valve that is used to control the flow of air.
Airflow
A flow or stream of air.
Airflow Resistance
The quotient of the air pressure difference across a specimen divided by the volume velocity of airflow through the specimen. The pressure difference and the volume velocity may be either steady or alternating.
Airfoil
A structure designed to obtain a useful reaction on itself in its motion through the air.
Alclad
Alclad is a trademark of Alcoa used as a generic term to describe corrosion resistant aluminium sheet formed from high-purity aluminium surface layers metallurgically bonded to high strength aluminium alloy core material.
Align
To adjust or set to a line or centre.
Alignment
A condition whereby the axes of machine components are either coincident, parallel or perpendicular, according to design requirements, during operation.
Alignment Pin
A pin or stud used to align one part with another.
Allowance
The prescribed difference in dimensions of mating parts to provide a certain class of fit.
Alloy
A metal produced by mixing other metals.
Alloying Elements
Chemical elements added for improving the properties of the finished materials.
Alpakka
A nickel silver made from 65% copper, 22% zinc, 13% nickel.

Alpha Iron
The body-centered cubic (BCC) form of pure iron, stable below 910°C.
Aluminium
Basis for a number of alloys.
Aluminium Brazing
Aluminium with a thin outer high silicon coating may be brazed.
Amalgam
An alloy that contains mercury.
Ambient Environment
The conditions characterizing the air or other medium that surrounds materiel.
American Society For Testing Material
An open forum for the development of high-quality, market relevant international standards used around the globe.
American Welding Society
The mission of the American Welding Society is to advance the science, technology and application of welding and allied joining and cutting processes, including brazing, soldering and thermal spraying.
American Wire Gauge
A numbering system for standard wire diameters, often abbreviated as AWG.
Amorphous
Non-crystalline, without long-range order.
Anchor
A weighty grappling hook used for holding a ship fast.
Anchorage
A secure fixing.
Ancillaries
Name given to components such as alternator, power steering pump and air conditioning compressor driven by the engine.
Angle Iron
An iron or steel structural member that has been cast, rolled, or folded so that its cross section is L-shaped.
Angle Plate
A precision holding fixture made of cast iron, steel, or granite.
Angular Acceleration
The rate of change of angular velocity.
Angularity
The angle between two shaft centrelines. This angle is the same at any point along either centreline. It is normally specified in rise/run.
Aniline Number
Lowest temperature at which equal parts of aniline and a sample of oil are completely miscible.
Anisotropic
Unequal physical properties along different axes.
Annealing
Heating to and holding at a suitable temperature and then cooling at a suitable rate, for such purposes as reducing hardness.
Annealing Twin
A twin formed in a crystal during recrystallization.
Anodize
To coat a metal with a protective film by electrolysis.
Anti Lock Brake System
A system that can modulate the brake pressure under hard braking conditions to avoid a brake locking and resultant skidding.
Anti-Friction Bearing
An anti-friction bearing is a bearing utilizing rolling elements between the stationary and rotating assemblies.
Antinode
Point of maximum displacement.
Anvil
A heavy iron or steel block upon which metal is forged or hammered.
A-Pillar
The first, or most forward, roof support pillar located on either side of the windshield.
Apparent Elastic Limit
Arbitrary approximation of the elastic limit of materials that do not have a significant straight line portion on a stress strain diagram.
Apparent Mass
Force per unit acceleration.
Appold Dynamometer
This is a friction based dynamometer with a water cooled drum and automatically corrects any variations of load due to changes in the coefficient of friction.
Aquaplaning
When water stands on a road or race track it may not be dispersed effectively from the tyre contact area with the road.
Arbor
A shaft or spindle for holding cutting tools; most usually on a milling machine.
Arbor Press
A hand-operated machine tool designed for applying high pressure for the purpose of pressing together or removing parts.
Arc Brazing
A brazing process wherein the heat is obtained from an electric arc formed between the base metal and an electrode.
Arc Cutting
A group of cutting processes in which the cutting of metals is accomplished by melting with the heat of an arc between the electrode and the base metal.
Arc Furnace
An electric furnace, in which heat is produced by an arc between two electrodes.
Arc Oxygen Cutting
An oxygen-cutting process used to sever metals by a chemical reaction of oxygen with a base metal at elevated temperatures.
Arc Welding
A group of welding processes in which fusion is obtained by heating with an electric arc or arcs, with or without the use of filler metal.
Arko Metal
A brass made with 80% copper and 20% zinc.
As Welded
The condition of weld metal, welded joints, and weldments after welding and prior to any subsequent thermal, mechanical, or chemical treatments.
Asbestos
This description covers a number of fibrous silicate minerals such as calcium magnesium silicate.
As-Cast Condition
Casting without subsequent heat treatment.
Ashpan
A container beneath the furnace, catching ash and clinker that falls through the firebars.
ASME
Abbreviation of American Society of Mechanical Engineers.
Aspect Ratio
For a graphics device it is the ratio of the screen dimensions, normally defined as vertical screen dimension divided by horizontal screen dimension.
Asphalt
A black sticky semi-solid material mainly bitumen with minerals, occurs naturally, but made artificially and used in the construction of roads and buildings.
ASTM
Abbreviation of American Society For Testing Material.
Asymmetrical Support
A rotor support system that does not provide uniform restraint in all radial directions.
Atomize
To break up a liquid into extremely fine particles.
Attitude Angle
The angle between the steady state preload through the bearing centreline, and a line drawn between the bearing centre and the shaft centreline.
Automatic Gearbox
A gearbox where the ratio between input and output shafts is changed automatically based on load, throttle application, engine speed and road speed.
Automatic Stop
A device which may be attached to any of several parts of a machine tool to stop the operation of the machine at any predetermined point.
Automobile
A self-powered vehicle that travels on land typically with three or four wheels and with 2 to 9 seats.
Auxiliary Firing
The addition of extra fuel into the exhaust gases of a turbine to provide an increase in heat output.
AWG
American wire gauge, a numbering system for standard wire diameters.
AWS
Abbreviation of American Welding Society.
Axial
In the same direction as the shaft centreline.
Axial Compressor
Rotating airfoil based compressor in which the working fluid principally flows parallel to the axis of rotation.
Axial Load
A load applied along or parallel to and concentric with the primary axis.
Axial Load Bearing
A bearing in which the load acts in the direction of the axis of rotation.
Axial Strain
The strain in the direction that the load is applied, or on the same axis as the applied load.
Axial Thrust
The load applied along or parallel to and concentric with the primary axis.
Axis
The line, real or imaginary, passing through the centre of an object about which it could rotate; a point of reference.
Axis of a Weld
A line through the length of a weld, perpendicular to a cross section at its centre of gravity.
Axis of Freedom
An axis about which an object is free to rotate.
Axle
An axle is a shaft on which a part rotates.
Back Draft
Reverse taper which would prevent removal of a pattern from a mould or a core from a corebox.
Back Gears
Gears fitted to a machine to increase the number of spindle speeds obtainable with a cone or step pulley belt drive.
Back Weld
A weld deposited at the back of a single groove weld.
Back Work Ratio
The fraction of the gas turbine work used to drive the compressor.
Backhand Welding
A welding technique in which the flame is directed towards the completed weld.
Backing Strip
A piece of material used to retain molten metal at the root of the weld.
Backing Weld
A weld bead applied to the root of a single groove joint to assure complete root penetration.
Backlash
The lost motion or looseness (play) between the faces of meshing gears or threads.
Backstep
A sequence in which weld bead increments are deposited in a direction opposite to the direction of progress.
Baffle Plate
A metal plate that acts as a baffle.
Bainite
An austenitic transformation product found in some steels and cast irons.
Balance Pipe
A pipe connecting two points of a system to even out pressure fluctuations.
Balanced Construction
A method of constructing manufactured wood products so that moisture content changes will be uniformly distributed and therefore will not cause warping.
Balancing
A procedure for adjusting the mass distribution of a rotor so that vibration of journals, or the forces on the bearings at once-per-revolution, are reduced or controlled.
Ball Bearing
A bearing designed to reduce rotational friction and support radial and axial loads.
Ball Burnishing
The smoothing of surfaces by means of tumbling parts in the presence of hardened steel balls, without abrasives.
Ball Check Valve
A fitting with a small ball that seals against a seat preventing flow in one direction and allowing flow in the other direction.
Ball Joint
A flexible joint consisting of a ball in a socket - locks the two parts in translation, but allows all degrees of rotation.
Ball Peen Hammer
A hammer with two ends on the head, one that is round and the other flat.
Ball Pien Hammer
A hammer with two ends on the head, one that is round and the other flat.
Ball Valve
A valve using a spherical closure element which is rotated through 90° to open and close the valve.
Ballscrew
A threaded shaft and nut assembly supported by angular contact bearings, normally found on machine tools.
Ballscrew Lead
The linear distance a carriage will travel for one revolution of the ball screw.
Bandsaw
A power saw, the blade of which is a continuous, narrow, steel band having teeth on one edge and passing over two large pulley wheels.
Bandwidth
The bandwidth of a filter is the separation between the lower and upper frequencies at which the amplitude of a sinusoidal signal is attenuated by a factor of 2.
Bar Clamp
A tool with a stationary head and a sliding foot for clamping purposes.
Bar Stock
Metal bars of various lengths, made in flat, hexagon, octagon, round, and square shapes from which parts are machined.
Barrell Burnishing
The smoothing of surfaces by means of tumbling a part in rotating barrels in the presence of metallic or ceramic shot, without abrasives.
Barrier
A physical structure which blocks or impedes something.
Base Metal
The metal to be welded or cut. In alloys, it is the metal present in the largest proportion.
Base Oil
A liquid having a suitable boiling range and viscosity for use in lubricating oils.
Baseplate
The surface to which the feet of a machine are attached.
Bastard
Threads, parts, tools, and sizes that are not standard.
bbl
Abbreviation of barrel. A unit of capacity in the oil industry.
BDC
Abbreviation of bottom dead centre.
Beam
A rigid structural element.
Bearing
Primarily two types, rolling element and sleeve or plain bearing.
Bearing Life
Defined as the length of time, or the number of revolutions, until a fatigue spall of a specific size develops.
Bearing Misalignment
A misalignment that results when the bearings supporting a shaft are not aligned with each other.
Bearing Nomenclature
Codes specific to the bearing manufacturer that describe the material, clearance, construction and other factors.
Bed
One of the principal parts of a machine tool, having accurately machined ways or bearing surfaces for supporting and aligning other parts of the machine.
Beeswax
Produced by bees to make their honeycombs.
Bell Crank
A lever that can be used to change the direction of a linear motion.
Bell Mouth
The flaring or tapering of a machined hole, usually made at the entrance end because of misalignment or spring of the cutting tool.
Bellows
Corrugated cylindrical container which moves as pressures change, or provides a seal during movement of parts.
Bellows Seal
A type of mechanical seal which utilizes bellows for providing secondary sealing and spring-type loading.
Belt Drive
A belt used to transmit power between two shafts.
Belt Noise
There are many different mechanisms by which drive belts generate noise.
Belville Washer
Often used on smaller angular contact arrangements to provide a preload.
Bench Grinder
A small grinding machine for shaping and sharpening the cutting edges of tools.
Bench Work
Work done primarily at a bench with hand tools.
Bend Radius
The inside radius of a bent section.
Bend Test
Various tests which are used to ascertain the toughness and ductility of a metal product, in which the material is bent around its axis and or around an outside radius.
Bending Moments
Internal forces on a structural element that cause the element to bend and thus create internal compression on one side of the element and internal tension on the other.
Bending Strength
A property of a solid that indicates its ability to withstand bending.
Bending Stress
Stress on the cross-sectional area of a beam due to the bending moment of the beam under load.
Bevel
Any surface that is not at right angles to another surface. Also, the name given a tool used for measuring, laying out, or checking the accuracy of work machined at an angle or bevel.
Bevel Angle
The angle formed between the prepared edge of a member and a plane perpendicular to the surface of the member.
Bevel Gear
Conical shaped gears, the angle between the input and output shaft is anything except 0 or 180°.
BHN
Abbreviation of Brinell Hardness Number.
BHP
Abbreviation of Brake Horse Power, the useful power available at the flywheel of an engine.
Billet
Rectangular or square bar of raw material.
Bimetallic Strip
Two metals with different thermal expansion coefficients are bonded together and wound into a spiral.
Birmingham Sheet Metal Gauge
This is a numbering system for sheet metal gauge (thickness).
Biscuit Joint
An oval shapped disk that when inserted in a slot with glue swells to form a tight bond. A special tool is required to cut the slot.
Black Annealing
Box annealing or pot annealing ferrous alloy sheet, strip or wire.
Black Box
A unit whose output is a specified function of the input, but for which the method of converting input to output is not necessarily specified.
Black Light
Electromagnetic radiation not visible to the human eye.
Black Oils
Lubricants containing asphaltic materials, which impart extra adhesiveness, used for open gears and steel cables.
Blacksmith Hammer
A special hammer for hitting and shaping heated iron.
Blacksmithing
The ancient art of forging and working metal, especially iron.
Blacksmiths Vice
A vice with a long leg that transfers some of the forces into the floor.
Blade
An arm of a propeller or a rotating wing.
Blade Clearance
Gap between blade and casing on a gas turbine.
Blade Passing Frequency
A potential vibration frequency on any bladed machine (turbine, axial compressor, fan, etc.). It is represented by the number of blades times shaft-rotating frequency.
Blank
A piece of metal cut or formed to regular or irregular shape for subsequent processing by forming, bending or drawing.
Blank Carburizing
Simulating the carburizing operation without introducing carbon.
Blast Furnace
A vertical shaft type furnace used for reducing iron ore to pig iron when cast or hot metal for further melting. This product is used in an open hearth or basic oxygen furnaces for production of steel.
Bleeder
A defect wherein a casting lacks completeness due to molten metal draining or leaking out of some part of the mould cavity after pouring has stopped.
Blind Hole
A hole made in a workpiece that does not pass through it.
Blind Reference Oil
A reference oil, the identity of which is unknown by the test facility.
Blister
A defect in metal, on or near the surface, resulting from the expansion of gas in a subsurface zone.
Block Brazing
A brazing process in which bonding is produced by the heat obtained from heated blocks applied to the parts to be joined.
Bloom
Generally a rolled product from an ingot generally greater than 36 square inches in area, this is the first operation in the production of bars or structurals.
Blow By
Passage of unburned fuel and combustion gases past the piston rings of internal combustion engines, resulting in fuel dilution and contamination of the crankcase oil.
Blow Down Cock
A valve mounted low-down on the boiler, often around the foundation ring, which is used to periodically vent water from the boiler.
Blow Holes
Voids or holes in a casting that may occur due to entrapped air or shrinkage during solidification of heavy sections.
Blowby
The combustion products and unburned air-and-fuel mixture that blows past the piston rings and enters the crankcase.
Blowhole
A defect in a casting caused by trapped steam or gas.
Blueprint
A pen or ink line drawing reproduced (printed) on sensitised paper by direct exposure.
BMEP
Brake Mean Effective Pressure, the average effective cylinder pressure that does useful work calculated from the brake horse power.
Bobbiere Metal
A brass made with 66% copper and 34% zinc.
Body Force
An external force acting throughout the mass of a body.
Body Hammer
A hammer with a large flat pounding surface for removing dents.
Boiler
A device for generating steam for power, processing, or heating purposes or for producing hot water for heating purposes or hot water supply.
Boiler Dome
A raised location on the top of the main boiler drum, providing a high point from which to collect dry steam, reducing the risk of priming.
Bolt Bound
The situation whereby a part cannot be moved in the desired direction because of mounting hole restrictions.
Bolted Joint
A joint formed between two or more pieces of material with the application of a nut and bolt.
Bookmatch
Successive layers of veneer are arranged side by side to resemble a mirror image of each other.
Boring
Enlarging a hole that already has been drilled or cored.
Boss
A projection or an enlarged section of a casting through which a hole may be machined.
Bossing Mallet
A hammer with a pear-shaped wooden head used for shaping and stretching metal over a sandbag or wooden block.
Boundary Lubrication
Occurs when the load-bearing surfaces come into contact.
Bourdon Tube
Thin-walled tube of elastic metal flattened and bent into circular shape, which tends to straighten as pressure inside is increased.
Box Annealing
Annealing a metal or alloy in a sealed container under conditions that minimize oxidation.
Box Wrench
American name for a ring spanner.
Boxing
The operation of continuing a fillet weld around a corner of a member as an extension of the principal weld.
Brace
A structural part designed to support, strengthen or stiffen a structure to resist loads.
Brake Graunch
The name given to the noise made by the brakes when they are just slipping when starting (or stopping) from rest. The brake graunch is mainly exhibited on the vehicles fitted with automatic transmission, but can also occur on manual vehicles e.g., on a steep hill. It is caused by brake pad stick-slip when static and dynamic friction is very similar. The term 'creep/groan' is also used to describe the brake graunch.
Brake Horse Power
This is the useful power available at the flywheel of an engine.
Brake Judder
Brake judder is the phenomenon where with medium to heavy braking from high speed, severe vibration is felt throughout the whole vehicle. It is often attributed to a mode of vibration in which the front suspension executes a predominantly fore and aft vibration with the two road wheels in-phase with each other. Excitation is often provided by the oscillatory forcing generated when applying the brakes to a brake disk that has disk thickness variation.
Brake Pipes
Pipes used to carry hydraulic brake fluid under pressure.
Brake Squeal
High frequency continuous tone when brakes are applied, this may be a single or multiple tones. The sound is generated by vibration on the surface of the disc itself.
Brakes
A device used to reduce the speed of a vehicle or object.
Braking Torque
The torque required to bring a motor down to a standstill.
Brale
A diamond penetrator of specified sphero-conical shape used with a Rockwell hardness tester for hard metals.
Brass
Brass is an alloy of copper and zinc, but often other elements such as aluminium, iron, manganese, tin and lead are added.
Brass Hammer
A hammer with a brass head.
Braze Welding
A method of welding by using a filler metal that liquefies above 450°C and below the solid state of the base metals.
Brazing
Joining metals by flowing a thin layer, capillary thickness, of nonferrous filler metal into the space between them.
Break Elongation
The elongation of the specimen to the break point.
Breakaway Torque
The torque necessary to put into reverse rotation a bolt that has not been tightened.
Breakdown Maintenance
Maintenance performed after a machine has failed to return it to an operating state.
Breakdown Torque
The maximum torque a motor will develop at rated voltage without a relatively abrupt drop or loss in speed.
Breaking Load
Load which causes fracture in a tensile, compression, flexure or torsion test.
Breaking Stress
Also known as the ultimate tensile strength. This is the maximum stress that can be applied to a material.
Breakloose Torque
The torque required to effect reverse rotation when a pre-stressed threaded assembly is loosened.
Brick
A shaped and burnt block of clay.
Bricklayer Hammer
A special hammer for chipping cement blocks and bricks.
Bright Dip
For high-purity aluminium an acid/copper solution is used to produce a bright clean surface.
Brinelling
A form of mechanical damage in which metal is displaced or upset without attrition.
Bristol Metal
A brass made with 75.5% copper and 24.5% zinc.
British Standard Brass
A specialist thread form based upon the Whitworth thread and consisting of 26 threads per inch whatever the thread diameter.
British Standard Fine
A thread form based upon the British Standard Whitworth form but with a finer thread.
British Standard Pipe
A family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends.
British Standard Whitworth
A symmetrical V thread with an angle between the threads measured in the axial plane of 55°. 1/6 of the V, i.e. the point is truncated with arcs blended tangentially into the flanks.
Broach
A long, tapered cutting tool with serration′s which, when forced through a hole or across a surface, cuts a desired shape or size.
Bronze
Bronze is an alloy of copper and tin. However, the name is now applied to other alloys that do not contain tin.
Brunel, Isambard Kingdom
Creator of the Great Western Railway, bridge builder and revolutionary naval architect.
BSB
Abbreviation of British Standard Brass.
BSF
A thread form based upon the British Standard Whitworth form but with a finer thread.
BSFC
Brake Specific Fuel Consumption, the ratio of the engine fuel consumption to the engine power output.
BSP
Abbreviation of British Standard Pipe.
BSW
Abbreviation of British Standard Whitworth
Buckle
To bend under compression.
Buckling
Distortion cuased by too much or uneven load.
Buckling Load
The limit of force beyond which a structure will buckle.
Buff
To polish to a smooth finish of high luster with a cloth or fabric wheel to which a compound has been added.
Bulge
A local distortion or swelling outward caused by internal pressure on a tube wall or boiler shell due to overheating.
Bulk Modulus
The bulk modulus of a gas is a measure of its compressibility (elastic property).
Bump Steer
A generally undesirable condition in which a wheel steers slightly as its suspension compresses or extends.
Bumping Hammer
An hammer used with a dolly for restoring a panel′s shape.
Buoyant Force
The upward force exerted by a fluid on a submerged or floating object.
Burgers Vector
A vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.
Burnishing
The process of finishing a metal surface by contact with another harder metal to improve it. To make smooth or glossy by or as if by rubbing; polish.
Burn-on Sand
Sand adhering to the surface of the casting that is extremely difficult to remove.
Burn-Out
Firing a mould at a high temperature to remove pattern material residue.
Burr
The sharp edge left on metal after cutting or punching.
Burst Disc
A diaphragm designed to burst at a predetermined pressure differential.
Burst Pressure
That pressure at which rupture of a stressed element or pressure-containing vessel takes place.
Bushing
A sleeve or a lining for a bearing or a drill jig to guard against wear.
Butt Hinge
One leaf attaches to the door′s edge, the other to its jamb.
Butt Joint
To place materials end-to-end or end-to-edge without overlapping.
Butt Welding
Joining two edges or ends by placing one against the other and welding them.
Butterfly Valve
Used for isolating or regulating flow where the closing mechanism takes the form of a disk.
Bypass Valve
A small bore valve fitted in parallel to a larger main valve.
CAD
Abbreviation of Computer Aided Design.
CAE
Abbreviation of Computer Aided Engineering.
Cage
The bearing cage is a device used to seperate the rolling elements of a bearing.
Cage Pocket
A section of a bearing cage that retains the ball.
Calibration
When recording or analysing any signal it is necessary to calibrate the system with a known signal.
Caliper
A measuring instrument used to measure the distance between two points or the inside or outside dimensions of an object.
Canal
An artificial channel of water used by boats and originally designed for the transportation of goods.
Candidate Oil
An oil that is intended to have the performance characteristics necessary to satisfy a specification and is to be tested against that specification.
Cantilever Beam
A beam that is held in an encastre at one end whilst the other end is unsupported.
Carbon Deposit
Carbon is routinely left as a black deposit on engine parts, such as pistons, rings, and valves, by the combustion of fuel.
Carbonitriding
Introducing carbon and nitrogen into a solid ferrous alloy by holding above the temperature at which austenite begins to form during heating.
Carbonizing Flame
An oxyacetylene flame in which there is an excess of acetylene.
Carborundum
More commonly known as Silicon Carbide, used extensively as a grinding compound and in abrasive wheels.
Carburizing
Introducing carbon into a solid ferrous alloy.
Cardan Joint
A flexible coupling between the input shaft and the output shaft allow power to be transmitted between the shafts at an angle.
Cardboard
A stiff form of paper most commonly used to manufacture packaging.
Cartridge Brass
A brass made with 75.5% copper and 24.5% zinc.
Cascamite
A waterproof resin based glue.
Case
In a ferrous alloy, the outer portion that has been made harder than the inner portion.
Case Hardening
Hardening a ferrous alloy so that the outer portion, or case, is made substantially harder than the inner portion, or core.
Cast Iron Gears
All types of cast iron, from gray to ductile, reduce noise because of the inherent damping properties of the metal.
Casting
A generic term referring to a process where a fluid material is made to flow into a shaped mold cavity where it solidifies.
Casting Yield
The weight of casting or castings divided by the total weight of metal poured into the mould
Catenary
A chain suspended from two points forms this curve.
Cavitation
A condition which can occur in liquid handling machinery where a system pressure decrease in the suction line and pump inlet lowers fluid pressure and vaporization occurs.
CD
Abbreviation for drag coefficient, a dimensionless value that allows the comparison of drag incurred by different sized and different shaped bodies.
Cement
A substance that can be used to build together aggregates of sand or stone into a cohesive structure. May be a single compound or a mixture. May be hydraulic set, air set or chemical set.
Cementite
A compound of iron and carbon.
Centistoke
A cgs unit of kinematic viscosity.
Centre of Mass
The balance point of an object. The location in an object that has the same translational motion as the object if it were shrunk to a point.
Centre Punch
A pointed hand tool made of hardened steel and shaped somewhat like a pencil.
Centres
Headstock and tailstock centres used to retain and centre the workpiece in a lathe.
Centrifugal Fan
A mechanical device for moving air or gases.
Centrifugal Force
A fictitious force arising in a rotating reference system.
Centrifuge Casting
A casting technique in which the mould is spun and the molten metal is poured in the centre.
Centripetal
An adjective meaning 'centre-fleeing.'
Ceramic Bearing
Ceramic balls have a higher stiffness, hardness and can operate at a higher temperature.
Ceramic Bearings
Fully ceramic bearings where all parts are made from ceramic and hybrid ceramic bearings where only the balls are ceramic.
Cermet
A composite material consisting of a combination of ceramic and metallic materials.
Cetane Index
A calculated value, derived from fuel density and volatility, giving a reasonably close approximation to cetane number.
CFM
Cubic foot per minute, a British imperial unit of flow rate.
ch
Metric horsepower.
Chain Drive
Power transmission by means of an endless chain running around chain wheels or sprocket wheels.
Chamfer
Beveled corner.
Channel
A frequency interval or frequency band assigned for communications.
Chaplet
A small metal insert or spacer used in moulds to provide core support during the casting process.
Charpy Test
An impact test in which a V-notched, keyhole-notched, or U-notched specimen, supported at both ends horizontally, is struck behind the notch by a striker mounted at the lower end of a pendulum.
Chatter
The vibrations caused between the work and the cutting tool which leave distinctive tool marks on the finished surface that are objectionable.
Chatter Marks
Marks at regular intervals on a workpiece due to machine tool vibration.
Check Valve
A valve that permits the passage of a liquid or gas in one direction only. It stops, or checks, reverse flow.
Chemical Set Cement
A cement that sets through reaction or precipitation.
Cheval Vapeur
Metric horsepower.
Chevron Packing
A type of packing used in packing boxes consisting of a nest of "V" cross-section rings.
Chip
A piece of semiconductor substrate on which active and/or passive circuit elements have been fabricated. Small piece of material removed from a workpiece by a cutting tool or grinding wheel.
Chipping
The process of cutting metal with a cold chisel and hammer.
Chipping Hammer
A hammer used to remove the slag from weld seams.
Chordal Thermocouple
A thermocouple installed in furnace tubes, designed to measure the effectiveness of water treatment within the boiler.
Chuck
A device on a machine tool to hold the workpiece or a cutting tool.
Cinnabar
Mercuric Sulphide, the ore of mercury. Occuring as red crystals.
Circlip
A clip that fits in a groove on a shaft and locates the shaft axially in one direction.
CL
Abbreviation for lift coefficient, a dimensionless value that allows the comparison of lift incurred by different sized and different shaped bodies.
Clack Valve
A non-return valve where the feedwater enters the boiler drum.
Cladding
An outer layer.
Clamp
A fastening device which secures something within its jaws without constant human pressure.
Clamping Force
The compressive force which a fastener exerts on the joint.
Clapper
Clapper The hinged closure element of a swing check valve.
Class of Fit
It is important that mechanical parts with tolerances that allow for certain types of operation of the two parts. There are a number of systems that classify the dimensional tolerances between parts for different applications.
Classical Mechanics
Lists all Classical Mechanics topics in the Encyclopaedia
Claw Hammer
A hammer with a forked end on the head which is used for removing nails.
Clay Filtration
A refining process using fuller′s earth, bauxite or other mineral to absorb minute solids from lubricating oil, as well as remove traces of water, acids, and polar compounds.
Clearance
The distance or angle by which one object or surface clears another.
Clearance Bearing
A journal bearing in which the radius of the bearing surface is greater than the radius of the journal surface.
Clearance Fit
A fit that always enables clearance between the hole and shaft of a coupling.
Clearance Volume
The volume of air or liquid remaining in the cylinder of an air compressor or a pump when the piston is nearest to the cylinder head.
Cleavage
Transcrystalline fracture along specific crystallographic planes.
Climb Milling
A method of milling in which the work table moves in the same direction as the direction of rotation of the milling centre.
Clinker
Coagulated slag or metal impurities that melt from the coal as it becomes coke.
Cloud Point
The temperature at which waxy crystals in an oil or fuel form a cloudy appearance.
Club Hammer
A hammer with a short handle but a large, heavy head.
Clutch
Coupling that connects or disconnects driving and driven parts of a driving mechanism.
Coefficient of Friction
The number obtained by dividing the friction force resisting motion between two bodies by the normal force pressing the bodies together.
Cog
A tooth in the rim of a wheel or a gear tooth in a gear wheel.
Cogeneration
A term used to describe the combination of different thermodynamic cycles for the purpose of increasing all-over cycle efficiency.
Cogging
Non-uniform angular velocity.
Cohesive Strength
Theoretical stress that causes fracture in tensile test if material exhibits no plastic deformation.
Coking
The undesirable accumulation of carbon deposits in the internal combustion engine or in a refinery plant.
Cold Alignment
The machine condition in which alignment procedures are normally performed, ie cold.
Cold Drawing
This is a process for finishing a hot rolled rod or bar at room temperature by pulling it through the hole of a die of the same shape but smaller in size.
Cold Junction
The reference junction of a thermocouple which is kept at a constant temperature.
Cold Metal Spraying
Involves injecting microscopic powdered particles of metal or other solids into a supersonic jet of rapidly expanding gas and shooting them at the surface.
Cold Rolling
The cold working of hot rolled material by passing it between power driven rolls.
Cold Treatment
A heat treat process which converts unstable retained Austenite into stable untempered Martensite.
Cold Working
The plastic deformation of a metal at a temperature below that at which it re-crystallizes.
Collapsible Core
A metal insert made in two or more pieces to permit withdrawal from an undercut mould surface.
Collet
A precision work holding chuck which centres finished round stock automatically when tightened.
Colour Temperature
The colour of a piece of steel may be used as a guide to it's temperature. These are particulalrly useful when hardening or tempering steel.
Columbium
A name sometimes given to Niobium, a platinum-gray, ductile metal with brilliant luster that is used in alloys, especially stainless steels.
Combined Steam Gas Plant
A gas turbine combined with a steam plant in order to utilize the waste heat and so improve overall efficiency.
Compliance
The displacement caused by a unit force applied to a spring or structural component. It is the reciprocal of stiffness (Units m/N).
Compounded Oil
A petroleum oil to which has been added other chemical substances.
Compressed Air
Air at any pressure greater than atmospheric pressure.
Compressed Air Dryer
A devise that removes moisture from compressed air.
Compressibility
The change in volume of a unit volume of a fluid when subjected to a unit change of pressure.
Compression
A pressing force that squeezes a material together.
Compression Ignition
Ignition of a fuel charge by the heat of the air in a cylinder, generated by compression of the air, as in the diesel engine.
Compression Ratio
In an engine, the ratio of the cylinder volume at BDC (Bottom Dead Centre) to cylinder volume at TDC (Top Dead Centre).
Compressive Deformation
Extent to which a material deforms under a crushing load.
Compressive Strength
For metals, the compressive strength is the same as the tensile yield strength.
Compressive Stress
Stress on the cross-sectional area of a body normal to the compression force acting on the body
Compressor
A mechanical device that increases the pressure of a gas by reducing its volume.
Computer Aided Design
Usually applied to that part of CAE which has to do with the drawing or physical layout steps of engineering design.
Computer Aided Engineering
A technique for using computers to help with all phases of engineering design work.
Concentrated Force
A force considered to act along a single line in space.
Concentric
Having a common centre.
Cone Clutch
The friction surfaces are on inner and outer cone surfaces.
Conjugate Tooth Pairs
Two gear teeth are conjugate if theyproduce uniform motion as they roll together.
Connection
A connection restrains degrees of freedom of one member with respect to another.
Constant Linear Velocity
A disc rotating at varying numbers of revolutions per second to maintain a constant relative velocity between pickup and track across the disc radius.
Constrained-Layer Damper
A layer of damping material between the structure′s surface and an additional elastic layer.
Contact Ratio
The contact ratio is the average numberof pairs of teeth in contact between two gears.
Contaminant
Any foreign or unwanted substance that can have a negative effect on system operation, life or reliability.
Continuity Equation
An equation which states that a fluid flowing through a pipe flows at a rate which is inversely proportional to the cross-sectional area of the pipe.
Continuous Casting
A casting technique in which an ingot, billet, tube, or other shape is continuously solidified while it is being poured, so that its length is not determined by mould dimensions.
Continuous System
A continuous system is one that is considered to have an infinite number of possible independent displacements.
Continuously Variable Transmission
A drive system where a belt running on pairs of cones allows the ratio between the input and output shafts to be varied continuously between the maximum and minimum ratios.
Contraction
A reduction in size.
Controlled Atmosphere Brazing
This process uses a non-corrosive powdered flux and an inert gas atmosphere.
Coolant
A fluid used to remove heat.
Cooling Fan
The size, specification and location of a cooling fan will depend upon the amount of heat that has to be dissipated from the object that has to be cooled.
Cope
The top half of a horizontally parted mould.
Copper Faced Hammer
A hammer with a round head made of copper or brass.
Coulisse
Of or using runners or slides as a guiding mechanism.
Coulomb Damping
Coulomb damping is the dissipation of energy that occurs when a particle in a vibrating system is resisted by a force whose magnitude is constant independent of displacement and velocity, and whose direction is opposite to the direction of the velocity of the particle.
Counter Weight
A weight added to a body so as to reduce a calculated unbalance at a desired place.
Countersink
To counter bore a hole such that the head of a screw may sit flush with the surface.
Couple
Two equal forces acting on a body in opposite directions and located at a specific distance apart produce a turning effect on the body.
Coupling
Mechanical fixture for joining two shafts.
Cover Glass
A clear glass used in goggles, hand shields, and helmets to protect the filter glass from spattering material.
CP
Abbreviation for pressure coefficient, a dimensionless value which acts as a means of indicating the local pressure at some point of interest around a body, and which is independent of velocity.
Creep
The time-dependent permanent deformation that occurs under stress.
Creep Limit
Also known as Creep Strength.
Creep Rate
Time rate of deformation of a material subject to stress at a constant temperature.
Creep Recovery
Rate of decrease in deformation that occurs when load is removed after prolonged application in a creep test.
Creep Rupture Strength
Stress required to cause fracture in a creep test within a specified time.
Creep Strength
Maximum stress required to cause a specified amount of creep in a specified time.
Creep Test
Method for determining creep or stress relaxation behaviour.
Crinolines
The framework of hoops used to support cladding over a boiler.
Critical Speeds
Any rotating shaft will have lateral (or flexural) and torsional natural frequencies. If the shaft is subjected to a force at any of these frequencies, the amplitude of vibration will be particularly large.
Cross Section
A view showing an internal structure as it would be revealed by cutting through the piece in any plane.
Crown
A contour on a sheet or roll where the thickness or diameter increases from edge to centre.
Cruise Control
Control system used to maintain the vehicle speed without the invention of a driver.
Crush Resistance
Load required to produce fracture in a glass sphere subjected to crush loading.
Crushing Load
Maximum compressive force applied during a compression or crushing test.
cSt
Abbreviation of Centistoke, a unit of kinematic viscosity.
Cup Fracture
Fracture, frequently seen in tensile test pieces of a ductile material, in which the surface of failure on one portion shows a central flat area of failure in tension, with an exterior extended rim of failure in shear.
Cure
To irreversibly polymerize a thermosetting plastic by subjecting it to a time-temperature profile.
Curie Temperature
The temperature above which a ferromagnetic or ferrimagnetic material becomes paramagnetic.
Cutting Fluid
A liquid used to cool and lubricate the cutting to improve the work surface finish.
Cutting Speed
The surface speed of the workpiece in a lathe or a rotating cutter.
Cutting Tool
A hardened piece of metal that is machined and ground so that it has the shape and cutting edges appropriate for the operation for which it is to be used.
Cutting Torch
A device used in gas cutting for controlling the gases used for preheating and the oxygen used for cutting the metal.
CVT
Abbreviation of Continuously Variable Transmission.
Cyanoacrylate
More commonly known as Super Glue or Instant Glue.
Cylinder Head
The detachable part of the top of the cylinder block that seals the cylinder and forms the top of the combustion chamber.
Damping Pad
Material applied to add damping to another material to reduce structural vibrations. This layer may be constrained or unconstrained.
Dashpot
A damping device, usually consisting of a cylinder and a piston in which relative motion of either displaces a fluid such as air or oil, resulting in friction.
Dead Centre
A centre that does not rotate.
Deburr
To remove sharp edges.
Decalescence
A decrease in temperature that occurs while heating metal through a range in which change in structure occurs.
Decarburization
The loss of carbon from the surface of a ferrous alloy.
Deep Drawing
Forming a deeply recessed part by forcing sheet metal to undergo plastic flow between dies.
Deep Etching
Severe etching of a metallic surface for examination.
Defect Structure
Relating to the kinds and concentrations of vacancies and interstitials in a ceramic compound.
Deformation Energy
Energy required to deform a material a specified amount.
Degas
Removing air from a liquid, usually by ultrasonic or vacuum methods.
Degrease
To remove oil and grease from the surface of a part.
Degrees of Freedom
The number of degrees-of-freedom of a mechanical system is equal to the minimum number of independent co-ordinates required to define completely the positions of all parts of the system at any instant of time.
Dehydrator
A separator that removes water from the system fluid.
Delivery Stroke
The stroke of a pump during which the fluid in the pump is forced out of the cylinder.
Delta Iron
An allotropic form of iron stable above 1400°C.
Dent
A sharply defined surface impression on the metal which may be caused by a blow from another object.
Depth Filter
A filter medium that retains contaminants primarily within tortuous passages.
Depth Filter Media
Porous materials which primarily retain contaminants within a tortuous path, performing the actual process of filtration.
Depth Gauge
A tool used in measuring the depth of holes or recesses.
Depth Micrometer
A micrometer in which the spindle projects through a flat accurately machined bar.
Depth of Cut
Distance between the bottom of the cut and the uncut surface of the workpiece, measured in a direction at right angles to the machined surface of the workpiece.
Design Limit
The operational limit of a product, beyond which it not required to function properly.
Detergent Additive
In lubrication technology, a surface active additive that helps to keep solid particles suspended in an oil.
Dial Indicator Gauge
Used to measure shaft runout or deviation from a nominal position.
Diaphragm
Flexible material usually made of thin metal, rubber or plastic.
Diaphragm Valve
A bi-directional valve which is operated by applying an external force to a flexible element or diaphragm.
Die Casting
Casting process wherein molten metal is forced under high pressure into the cavity of a metal mould.
Die Lines
Lines of markings caused on drawn or extruded products by minor imperfections in the surface of the die.
Die Stock
The frame and two handles which hold the dies used for cutting external screw threads.
Diesel Particulate Filter
A device which physically captures diesel particulates preventing their discharge from the tailpipe.
Differential
Geared device between the driven wheels to allow varying rotational speeds of the wheels around corners.
Differential Pressure Valve
A valve whose primary function is to limit differential pressure.
Dip Brazing
A brazing process in which bonding is produced by heating in a molten chemical or metal bath.
Dipstick
The metal rod that passes into the oil sump it is used to determine the quantity of oil in the engine.
Direct Chill Casting
A continuous method of making ingots or billets for sheet or extrusion by pouring the metal into a short mould.
Direct Quenching
Quenching carburized parts directly from the carburizing operation.
Disc Clutch
A disc on the end of the input shaft with a friction surface and a disc on the end of the output shaft.
Dispersant
An additive that reduces deposits on oil-wetted surfaces primarily through suspension of particles.
Disposable Filter
A filter element intended to be discarded and replaced after one service cycle.
Distributed Load
An external force which acts over a region of length, surface, or area: essentially any external force which is not a concentrated force.
Diverter Valve
A valve which can change the direction of the flow of a medium to two or more different directions.
Dividing Head
A machine tool holding fixture which positions the work for accurately space holes, slots, flutes and gear teeth and for making geometric shapes
Dodd Bars
A secondary alignment method. Consists of two bars that are similar in configuration to reverse dial indicator bars.
Doppler Sonar
An acoustic instrument that measures the change in the acoustic frequency of the scattered sound or echo from that of the transmitted pulse. The magnitude and direction of the shift in frequency is related to the relative motion of the sensor and the scatterer.
Double Glazing
Two layers of glazing used to improve thermal and acoustic radiation.
Double Helical Gear
The double helical gear gives a much smoother still operation than the spur or helical gear and reduces the noise levels further.
Double Row Bearing
A bearing having two rows of rolling elements.
Dovetail Joint
A joint where the fingers are shaped like a doves tail, used to join pieces at 90 degrees.
Dovetail Saw
A saw designed for cutting dovetail joints and other wood joints.
Dowel
A pin fitted or keyed in two adjacent parts to accurately align the parts when assembling them.
Down Feed
A seldom used method of feeding work into milling cutters.
Downcomer
Large external pipes in many water-tube boilers, carrying unheated cold water from the steam drum down to the water drum as part of the circulation path.
Downforce
The opposite of aerodynamic lift, sometimes referred to as negative lift. The force caused by the air over the wings to push the car into the ground, increasing grip and cornering speeds.
Draft Angle
A mandrel′s taper or angle for ease of part removal.
Drain Cock
A tap provided for the purpose of draining off liquids from a tank or reservoir.
Drawing
A deformation technique used to fabricate metal wire and tubing.
Drawn Product
A product formed by pulling material through a die.
Dressing
The act of removing the glaze and dulled abrasives from the face of a grinding wheel to make it clean and sharp.
Drill Jig
A jig that holds parts of a structure and by means of bushings, guides the drill so that the holes are properly located.
Drive Fit
One of several classes of fits in which parts are assembled by pressing or forcing one part into another.
Driveline
An assembly of one or more driveshafts with provisions for axial movement, which transmits torque and/or rotary motion at a fixed or varying angular relationship from one shaft to another.
Driveshaft
An assembly of one or two universal joints connected to a solid or tubular shaft member used to transmit rotational power.
Dropping Point
The temperature at which a grease changes from a semi-solid to a liquid state under test conditions.
Drum Type Armature
An efficient, popular type of armature designed so that the entire length of the winding is cutting the field at all times. Most wound armatures are of this type.
Dry Friction Damping
Coulomb damping is the dissipation of energy that occurs when a particle in a vibrating system is resisted by a force whose magnitude is constant independent of displacement and velocity, and whose direction is opposite to the direction of the velocity of the particle.
Dry Strength
Strength of an adhesive joint determined immediately after drying or after a period of conditioning in a specified atmosphere.
Dual Voting
Concept where two independent inputs are required before action, usually machine shutdown, is taken.
Duct
A pipe or closed conduit made of sheet metal, fibreglass board, or other suitable material used for conducting air to and from an air handling unit.
Duct Acoustics
Ducts with acoustic waves propagating through them exist in many forms.
Ducted Fan
A fan enclosed in a duct.
Ductile Fracture
A mode of fracture that is attended by extensive gross plastic deformation.
Ductility
A measure of a material′s ability to undergo appreciable plastic deformation before fracture.
Duplex Filter
An assembly of two filters with valving for selection of either or both filters.
Durability
Lists all Durability topics in the Encyclopaedia
Dust
An air suspension or particles of any solid material, usually with particle size less than 100 microns.
Dwell
In an engine, the time allowed for current to build in the primary circuit of the ignition coil for each spark generation.
Dye Penetrant
Penetrant with dye added to make it more readily visible under normal lighting conditions.
Dynamic Creep
Creep that occurs under fluctuating load or temperature.
Dynamic Equilibrium
Equilibrium which includes inertial forces.
Dynamic Friction
Resistance to relative movement of two bodies that are already in motion.
Dynamic Load
A load imposed by dynamic action, as distinguished from a static load.
Dynamic Modulus
Ratio of stress to strain under vibratory conditions.
Dynamometer
A device for determining the power of an engine.
E85
Refers to a fuel blend of 85 percent ethanol and 15 percent gasoline.
Earing
Wavy projections formed at the open end of a cup or shell in the course of deep drawing because of difference in directional properties.
Eccentric
A circle not having a geometric centre.
Eccentricity
The variation of the outer diameter of a shaft surface when referenced to the true geometric centreline of the shaft.
Eccentricity of Loading
Distance between the actual line of action of compressive or tensile loads and the line of action that would produce a uniform stress over the cross section of the specimen.
Eccentricity Ratio
The vector difference between the bearing centreline and the average steady-state journal centreline.
Edge Dislocation
A linear crystalline defect associated with the lattice distortion produced in the vicinity of the end of an extra half-plane of atoms within a crystal.
Efficiency
A measure of how well a machine changes energy into useful energy.
Elastic Hysteresis
Difference between strain energy required to generate a given stress in a material and elastic energy at that stress.
Elastic Limit
The maximum load that a body can experience and still return to its original shape.
Elastic Strain
Dimensional changes accompanying stress where the original dimensions are restored upon release of the stress.
Elasticity
A material is elastic if it returns to it's original shape after being deformed.
Elastomer
A polymeric material that may experience large and reversible elastic deformations.
Electric Motor Bearings
The bearings that support the armature and allow it to rotate relative to the stator.
Electric Motors
There are a number of different types of electric motor: AC Induction Motors, Brush Direct Current Motors, Brushless Direct Current Motors and Stepper Motors.
Electrobrightening
Improving the specular reflectivity of a metal surface by electrochemical dissolution.
Electroform
To form shaped objects by electro-deposition on a mould.
Electromagnetism
Lists all Electromagnetism topics in the Encyclopaedia
Electromechanical
Converting electrical input into mechanical action.
Electron Beam Welding
A technique for joining materials in which components to be welded are heated by a concentrated beam of high-velocity electrons in a vacuum.
Electropolishing
A process that produces a bright, shiny surface on a metal using an electrolytic cell under conditions that projections on the surface are dissolved faster than the smoother areas.
Electrorefining
A method for purifying a metal using electrolysis.
Elongation
Increase in length which occurs before a metal is fractured, when subjected to stress.
Emery
A natural abrasive used for grinding or polishing.
Emery Cloth
Fabric backed abrasive paper.
Empirical Law
A law strictly based on experiment, which may lack theoretical foundation.
Encastre
A term which describes the constraints imposed on a structure where it joins its foundations.
End Float
Movement of one shaft along its centreline due to the freedom of movement permitted by a journal bearing or a sleeve bearing.
Energy Density
Characteristic parameter of a battery/electrical power source indicating the amount of electrical energy stored per unit weight or volume.
Energy Efficiency
Ratio of energy output of a conversion process or of a system to its energy input.
Engine Efficiency
For thermal engines this is the relationship between the total energy contained in the fuel, and the amount of energy used to perform useful work.
Engineering
A profession in which a knowledge of math and natural science is applied to develop ways to utilize the materials and forces of nature for the benefit of all human beings.
Engineering and Physical Sciences Research Council
EPSRC funds research and postgraduate training in engineering and the physical sciences at universities and other organisations throughout the UK.
Engineering Ceramics
Technical ceramics for structural applications.
Engineering Design
Lists all Engineering Design topics in the Encyclopaedia
Engineering Units
Units that are decided upon by an individual user or by agreement among users.
Engines
Lists all Engines topics in the Encyclopaedia
Entrained Air
A mechanical mixture of air bubbles having a tendency to separate from the liquid phase.
Environmental Tests
A set of tests used to establish that a piece of equipment can withstand a lifetime of exposure to the environment it will have to survive.
Eolipile
Device which propels itself by shooting steam from one or more orifices.
Epoxy Glue
A two-part resin/hardener glue that is extremely strong.
EPSRC
Engineering and Physical Sciences Research Council
Errors
No measurement is exact, they all contain some degree of errors.
Etching
Chemical surface corrosion.
Ethanol E85
Refers to a fuel blend of 85 percent ethanol and 15 percent gasoline.

Ethyne
Also known as Acetylene, used for welding as the flame temperature is roughly 3300°C when burnt with oxygen.
E-Type Thermocouple
Chromel-constantan thermocouple with a temperature range of 0 to 800°C.
Eutectic
An isothermal reversible reaction or an alloy having a structure or composition indicated by the eutectic point.
Exhaust
An exhaust system of an internal combustion engine performs a number of functions.
Exhaust Injector
A feedwater injector that economizes on steam consumption by using waste steam, such as engine exhaust.
Exhaust Silencer
Acoustic filter elements used to reduce sound pressure levels in an exhaust system.
Exhaust Tailpipe
The final pipe that the exhaust gas passes through before mixing with the atmosphere.
Explosion Proof Enclosure
A totally enclosed enclosure, which is constructed to withstand an explosion of a specified gas, vapor or dust which, may occur within it.
Explosive Decompression
A very rapid reduction of air pressure inside a cabin, coming to a new static condition of balance with the external pressure.
External Force
A surface force or body force acting on an object.
Extreme Pressure Additive
Lubricant additive that prevents sliding metal surfaces from seizing under conditions of extreme pressure.
Extreme Pressure Lubricants
Lubricants that impart to rubbing surfaces the ability to carry appreciably greater loads than would be possible with ordinary lubricants without excessive wear or damage.
Extruded
A material that has been shaped by forcing through a die.
Extrusion
A forming technique whereby a material is forced, by compression, through a die orifice.
Face
To machine a flat surface as in the end of a shaft in the lathe.
Face Milling
Milling a large flat surface with a milling cutter that operates in a plane that is at right angles to its axis.
Face of Weld
The exposed surface of the weld.
Faceplate
A large circular plate with slots and holes for mounting the workpiece to be machined. It is attached to the headstock of a lathe.
Facing
The process of making a flat or smooth surface on the end of a piece of material.
Facing Sand
The sand used to surround the pattern that produces the surface in contact with the molten metal.
Famous Scientists & Engineers
Lists all the Famous Scientists & Engineers in the Encyclopaedia
Fans
There are several simple relationships between fan capacity, pressure, speed, and power, which are referred to as the fan laws.
Fast Fourier Transform
An algorithm, or digital calculation routine, that efficiently calculates the discrete Fourier transform from the sampled time waveform.
Faying Surface
That surface of a member that is in contact with another member to which it is joined.
Feed Pipe
A pipe supplying liquid or gas.
Feed Pump
A pump supplying liquid or gas.
Feeler Gauges
A set of steel fingers of different thicknesses that can be used to set the gap between two objects.
FEM
Finite element method is a numerical method which is used to calculate displacements or stresses in structures or components subjected to external and internal loads.
Fender Washer
An oversize washer used to spread the load further on soft or thin materials.
Ferrous Metal
A metal alloy in which iron is the major ingredient.
FFT
An abbreviation of Fast Fourier Transform, an algorithm, or digital calculation routine, that efficiently calculates the discrete Fourier transform from the sampled time waveform.
Fibre Grease
A grease with a distinctly fibrous structure, noticeable when the grease is pulled apart.
Fibre Stress
Stress through a point in a part in which stress distribution is not uniform.
Fibre Washer
Used in many different applications for electrical or thermal insulation, to distribute the load or to add some complaince to the bolted structure.
Fiddleback
Describes wood, usually maple or mahogany but can be any wood, with Curl or Tiger grain material with fine grain used in the manufacture of violins, hence the name.
Field-Tube
A form of single-ended thimble water tube with an internal tube to encourage circulation.
File
A hand tool used to shape material by abrasion.
Filler
An inert foreign substance added to a matrix to improve or modify its properties.
Fillet
A curved surface connecting two surfaces that form an angle.
Film Brazing
A process in which bonding is produced by heating with a molten nonferrous filler metal poured over the joint until the brazing temperature is attained.
Filter
Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiation of certain frequencies while passing others.
Filter Capacity
The amount of contaminants a filter will hold before an excessive pressure drop is caused.
Filter Efficiency
Method of expressing a filter's ability to trap and retain contaminants of a given size.
Filter Element
The porous device which performs the actual process of filtration.
Filter Glass
A coloured glass used in goggles, helmets, and shields to exclude harmful light rays.
Filter Head
An end closure for the filter case or bowl that contains one or more ports.
Filter Housing
A ported enclosure that directs the flow of fluid through the filter element.
Filter Life Test
A type of filter capacity test in which a clogging contaminant is added to the influent of a filter.
Filtration
The physical or mechanical process of separating insoluble particulate matter from a fluid.
Filtration Ratio
The ratio of the number of particles greater than a given size in the influent fluid to the number of particles greater than the same size in the effluent fluid.
Fin Stock
Coiled Sheet or foil in specific alloys, tempers and thickness ranges suitable for manufacture fins for heat exchanger applications.
Finger Joint
Long tapered fingers used to join material lenghtwise.
Finish Feed
Feeding in small increments for finishing the part.
Finish Machining
Machining a surface to give it the desired finish.
Finishing
Any of many different processes employed for surface, edge and corner preparation, as well as conditioning, cleaning and coating. In machining, usually constitutes a final operation.
Finishing Hammer
A pounding device used for detail work in shaping a panel after it has been brought approximately into the right shape.
Finite Element Method
A numerical method which is used to calculate displacements or stresses in structures or components subjected to external and internal loads.
Fire Tube Boiler
A boiler where the primary heating surface is tubes with hot gas flowing inside and water outside.
Firebar
Replaceable cast-iron bars that form the base of the furnace and support the fire.
Firing
A high-temperature heat treatment that increases the density and strength of a ceramic piece.
Firing Order
The order in which combustion is initiated in an internal combustion engine.
First Class Lever
The fulcrum is situated between the load and the applied force.
Fit
The desired positive or negative clearance between the surfaces of two machined parts.
Fixed Connection
In two dimensions, a fixed connection between two members restrains all three degrees of freedom of the connected member with respect to one another.
Fixed Displacement Pump
A pump in which the displacement per cycle cannot be varied.
Fixed Machine
The machine whose position is not changed during shaft alignment.
Fixings and Fasteners
Lists all Fixings and Fasteners topics in the Encyclopaedia
Flame Annealing
Annealing in which the heat is applied directly by a flame.
Flame Hardening
Quench hardening in which the heat is applied directly by a flame.
Flame Softening
A method for softening steel by heating with a gas flame followed by slow cooling.
Flange
A relatively thin rim around a part.
Flashing
A thin edge of material formed at the parting line of a casting or forging where it is forced out between the edges of the form or die.
Flat Belt Drive
A belt used to transmit power between two shafts.
Flat Sheet
Sheet with sheared, slit or sawed edges, which has been flattened or leveled.
Flatness
For rolled products, a distortion of the surface of sheet such as a bulge or a wave, usually transverse to the direction of rolling.
Flexural Modulus of Elasticity
Alternate term for modulus in bending.
Flexural Strength
A property of a solid that indicates its ability to withstand bending.
Flexure Mode
Flexure modes are associated with thin slender beams.
Flitch
A section of timber cut lengthwise from the trunk of the tree
Float Valve
A valve which automatically opens or closes as the level of a liquid changes.
Flow Control Valve
A device used to control the flow of fluid contained in a pipe line.
Flow Lines
Texture showing the direction of metal flow during hot or cold working.
Flow Rate
Volume per unit of time.
Flow Stress
The shear stress required to cause plastic deformation of solid metals.
Flue
A large fire tube, either used as the main heating surface in a flued boiler, or used as enlarged firetubes in a locomotive-style boiler where these contain the superheater elements.
Fluid Dynamics
Lists all Fluid Dynamics topics in the Encyclopaedia
Fluid Film Bearing
A bearing which supports the shaft on a thin film of oil.
Fluid Friction
Friction due to the viscosity of fluids.
Fluid Power
Energy transmitted and controlled through use of a pressurized fluid.
Fluid Pump
A device for moving fluids.
Fluid Velocity
The measured speed at which a fluid moves through the inside of a tube.
Flute
The groove in a cutting tool which provides a cutting edge and a space for the chips to escape and permits the cutting fluids to reach the cutting edges.
Flux Dip Brazing
The component is immersed in a molten salt which acts as a flux as well as a heat source for melting the clad layer.
Fly Cutter
A single-point cutter mounted on a bar in a fly cutter holder or a fly cutter arbour used for special applications for which a milling cutter is not available.
Flywheel
The wheel on the end of the crankshaft that gives the crankshaft momentum to carry the pistons through the compression stroke.
Foam Inhibitor
An additive which causes foam to dissipate more rapidly.
Food Grade Lubricants
Lubricants acceptable for use in meat, poultry and other food processing equipment, applications and plants.
Foot Brake
Vehicle brake applied with the foot.
Force Feed Lubrication
A system of lubrication in which the lubricant is supplied to the bearing surface under pressure.
Force Fit
A fitting which one part is forced of pressed into another to form a single unit.
Forge
The blacksmith′s workshop. Also meaning to forge a workpiece.
Forge Welding
A group of welding processes in which fusion is produced by heating in a forge or furnace and applying pressure or blows.
Forging
Mechanical forming of a metal or alloy by heating and hammering.
Formability
The relative ease with which a metal can be shaped through plastic deformation.
Formed Cutters
Milling cutters which will produce shaped surfaces with a single cut.
Foundation Ring
The base of the firebox, where the inner and outer shells are joined.
Foundation Stiffness
A term used to refer to the stiffness of a machine support or the region of contact between a structure and its surroundings.
Four High Mill
Common rolling mill for reducing the thickness of aluminum sheet consisting of two large diameter work rolls which are supported by even larger back-up rolls.
Fracture Testing
Breaking a specimen and examining the fractured surface with the unaided eye or with a low-power microscope to determine such things as composition, grain size, case depth, soundness, or presence of defects.
Fracture Toughness
Critical value of the stress intensity factor for which crack extensions occurs.
Free Bend Test
A method of testing weld specimens without the use of a guide.
Free Cut
An additional cut with a machine tool with no advancement of depth.
Free Ferrite
Ferrite that is structurally separate and distinct.
Free Fit
A class of fit intended for use where accuracy is not essential or where large temperature variations are likely to be encountered, or both conditions.
Free-Layer Damper
A treatment to control the vibration of a structural by bonding a layer of damping material to the structure′s surface.
Fretting
Action that results in surface damage, especially in a corrosive environment, when there is relative motion between solid surfaces in contact under pressure.
Friction
The resistance to motion which is called into play when it is attempted to slide one surface over another, with which it is in contact.
Friction Clutch
A shaft coupling used where it is necessary to provide a connection that can be readily engaged or disengaged while one of the shafts is in motion.
Friction Gear
Device for the transmission of rotational power that relies on friction between the drive devices to transmit the forces.
Friction Gouges
A series of relatively short surface scratches variable in form and severity.
Friction Torque
Torque caused by the frictional force that occurs when two objects in contact move.
Froude Number
A dimensionless number used in the study of fluid flow problems with models.
F Temper
As Fabricated Temper - applies to products of rolling or forming where there is no special control over the thermal or work hardening conditions.
Fuel Cell
A device that converts the chemical energy obtained from a redox reaction directly into electrical energy.
Fulcrum
The support on which a lever turns.
Full Flow Filter
A filter that, under specified conditions, filters all influent flow.
Full Hard Temper
In non-heat treatable alloys, it is the hardest temper obtainable by hard cold rolling.
Fullering
The process of hammering grooves in hot iron to spread it out thinner.
Funicular
A funicular shape is one similar to that taken by a suspended chain or string subjected to a particular loading.
Furnace Brazing
A process in which bonding is produced by the furnace heat and a nonferrous filler metal having a melting point above 427°C.
Fusible Plug
A threaded metal cylinder with a hole that is sealed with a metal of low melting point that flows away if a pre-determined, high temperature is reached.
Fusion
The combining of light nuclei to form a heavier nucleus. Also, the complete mixing of two materials along an edge.
Galling
A severe form of adhesive wear which occurs during sliding contact of one surface relative to another.
Galloway Tubes
Tapered thermic syphon water-tubes inserted in the furnace of a Lancashire boiler.
Galvanize
To coat a metal surface with zinc using various processes.
Gamma Iron
The face-centered cubic form of pure iron, stable from 910 to 1400°C.
Gang Milling
A milling setup where a number of cutters are arranged on an arbor so that several surfaces can be machined at one time.
Gas
Matter with no definite shape or volume.
Gas Bearing
A journal or thrust bearing lubricated with gas.
Gas Metal Arc Welding
An arc welding process that produces coalescence of metals by heating them with an arc between a continuous filler metal electrode and the work pieces.
Gas Pedal
A pedal that when pressed is connected to the engine and demands more torque.
Gas Pocket
A weld cavity caused by the trapping of gases released by the metal when cooling.
Gas Welding
A process in which the welding heat is obtained from a gas flame.
Gasket
A thin layer of material placed between two surfaces or joints to make a tight seal.
Gate Valve
A straight through pattern valve in which closure element is a wedge situated between two fixed seating surfaces, with means to move it in or out of the flow stream in a direction perpendicular to the pipeline axis.
Gauge
Commonly used to describe the thickness of sheet material.
Gauge Blocks
Steel blocks machined to extremely accurate dimensions.
Gauge Glass
Part of the water level gauge, which normally consists of a vertical glass tube connected top and bottom to the boiler backplate.
G Clamp
A screw-activated clamping device in the shape of the letter G.
G-Code Programming
Programs written to operate NC machines with control systems that comply with the ANSI/EIA RS-274-D-1980 Standard.
Gear Design
Fundamental parameters used in describing gears.
Gear Noise
Gear noise such as whine are generated by meshing gears due to the vibration caused by failure of the rolling action between the mating teeth.
Gear Oil
A high-quality oil with good oxidation stability, load-carrying capacity, rust protection, and resistance to foaming.
Gear Pump
Uses the meshing of gears to pump fluid by displacement.
Gearbox
A mechanical device that provides a torque-speed conversion between an input and output shaft.
Gears
Wheels with teeth around the circumference that mesh to transfer rotation between the two at the ratio of the radius of the pitch circle.
Geometric Scattering
Acoustic scattering in which the wavelength of the sound used is much smaller than the size of object causing the scattering.
Glass Ceramic
A fine-grained crystalline material that was formed as a glass and subsequently devitrified (crystallized).
Glass Transition Temperature
The temperature at which, upon cooling, a noncrystalline ceramic or polymer transforms from a supercooled liquid into a rigid glass.
Glasspaper
An abrasive paper used to smooth the rough edges of freshly sawn wood.
Glider
A highly efficient engineless aeroplane. Capable of flying for long periods in gently rising air currents.
Globe Valve
A valve whose closure element is a flat disc or conical plug sealing on a seat which is usually parallel to the flow axis.
Glue
Cement or adhesive that is used to fix two or more parts together.
Goggles
A device with coloured lenses which protect the eyes from harmful radiation during welding and cutting operations.
Goldschmidt Process
The method of obtaining liquid metal by reduction of the oxide with aluminium powder.
Gouge
A deep scratch.
Governor
A mechanical or electronic device for controlling or limiting the rotational speed of an engine or shaft.
Grade
Grade is used to define an angle, grade of sandpaper, amongst others..
Graduation Mark
The marks that define the scale intervals on a measuring instrument are known as graduation marks.
Grain
An individual crystal in a poly-crystalline metal or alloy.
Grain Coarsening
A heat treatment that produces excessively large austenitic grains.
Grain Size
For metals, a measure of the areas or volumes of grains in a polycrystalline material, usually expressed as an average when the individual sizes are fairly uniform.
Grease
A lubricant composed of an oil or oils thickened with a soap, soaps or other thickener to a semisolid or solid consistency.
Grinding Ratio
Measure of the grinding performance defined as the volume of metal removed divided by the volume of grinding wheel worn away in the operation.
Gross Vehicle Weight
The maximum loaded weight, including the vehicle itself, passengers, and cargo, for which a vehicle is designed and as specified by the manufacturer.
Gudgeon Pin
Also known as Piston Pin, a pin that rests in two bored holes in the piston and passes through the eye of the connecting rod, to join the two together flexibly.
Guy Rope
Cables attached to a tripod or tower to increase stability.
Guyan Reduction (Static Condensation)
A Finite Element reduction technique which is used in the dynamic solution of very large problems having a large number of degrees of freedom where we often desire only a small percentage of the frequency and mode shapes.
GVW
Abbreviation of Gross Vehicle Weight.
Hacksaw
A metal blade of hardened steel having small, close teeth on one edge, held under tension in a U-shaped frame.
Half Male Centre
A dead center that has a portion of the 60 degree cone cut away.
Half Nut
A lever-operated mechanism that resembles a split nut that can be closed on the lead screw of a lathe when threads are being cut.
Hammer
A hand tool with a metal head and a handle. It is used to force one item against or through another.
Hammer Welding
A forge welding process.
Handbrake
Vehicle brake that is applied by hand to hold the vehicle when stationary.
Handwheel
Any adjusting or feeding mechanism shaped like a wheel and operated by hand.
Hard Facing
A particular form of surfacing in which a coating or cladding is applied to a surface for the main purpose of reducing wear.
Hard Surfacing
The application of a hard, wear-resistant alloy to the surface of a softer metal.
Hardenability
In a ferrous alloy, the property that determines the depth and distribution of hardness induced by quenching.
Hardening
Increasing the hardness by suitable treatment, usually involving heating and cooling.
HAWT
Abbreviation of Horizontal Axis Wind Turbine.
Headstock
The fixed or stationary end of a lathe or similar machine tool.
Heat Check
A pattern of parallel surface cracks that are formed by alternate rapid heating and cooling of the extreme surface metal.
Heat Treatment
Heating and cooling a solid metal or alloy in such a way as to obtain desired conditions or properties.
Helical Gear
The helical gear gives a much smoother operation than the spur gear and reduces the noise levels. However, it is more difficult to manufacture.
Helical Spring
A coiled spring.
Helicopter
An aircraft that produces lift using airfoils that are driven and rotate about a vertical axis.
Helix
A path formed as a point advances uniformly around a cylinder, as the thread on a screw or the flutes on a drill.
Hermetic
Sealing of an object so it is airtight.
HgS
Mercuric Sulphide, the ore of mercury. Occuring as red crystals.
Hidden Lines
Broken lines used to signify lines that normally wouldn't be seen in a drawing.
High Impact Characteristics
Product and/or process characteristics that, when outside of the specification tolerance, severely affect subsequent manufacturing operations or customer satisfaction.
Hinge
A type of mechanical bearing formed between two parts allowing one to be rotated relative to the other e.g. door hinges.
Hob
A cylindrical cutting tool shaped like a worm thread and used in industry to cut gears.
Hobbing
The operation of cutting gears with a hob.
Hogging
The upwards bending in a beam, usually over its piers, that is the counterbalance to sagging in other sections of the beam.
Honing
The process of finishing ground surfaces to a high degree of accuracy and smoothness.
Hookes Joint
A universal joint arrangement designed to cancel out the vibrations caused when the joint angle between the two driveshafts is varied while power is applied.
Hookes Law
A Law stating that, in a linear system, the restoring force is proportional to the displacement of the body, acting in a direction as to restore equilibrium.
Hoop Stress
Circumferential stress in a cylindrically shaped part as a result of internal or external pressure.
Horizontal Axis Wind Turbine
A wind turbine where the axis of rotation is horizontal and a conventional propeller that absorbs the wind power.
Horsepower
Mechanical engineering unit of power.
Hot Bolting
This term is used for the completion of maintenance work on a bolted joint when the joint is under load.
Hot Isostatic Pressing
A process that subjects a component to both elevated temperature and isostatic gas pressure.
Hot Pressing
A method used to increase the density of a material.
Hot Rolled
Hot rolled products are those products that are rolled to finish at temperatures above the re-crystallisation temperature.
Hot Short
A condition which occurs when a metal is heated to that point, prior to melting, where all strength is lost but the shape is still maintained.
Hot Working
Any metal forming operation that is performed above a metal recrystallization temperature.
Housing
An enclosure for electrical or mechanical parts.
hp
Mechanical engineering unit of power.
Hunting
Erratic variation of rotational speed.
Hybrid Bearing
A bearing that consists of metal rings and ceramic balls.
Hydraulic Fluid
Fluid serving as the power transmission medium in a hydraulic system.
Hydraulic Motor
A device which converts hydraulic fluid power into mechanical force and motion by transfer of flow under pressure.
Hydraulic Pump
A device which converts mechanical force and motion into hydraulic fluid power by means of producing flow.
Hydraulic Set Cement
A cement that sets through reaction with water.
Hydraulic System
A system designed to transmit power through a liquid medium permitting multiplication of force.
Hydraulically-Assisted Clutch
A clutch operated by hydraulic pressure.
Hydraulics
Engineering science pertaining to liquid pressure and flow.
Hydro Turbine
A rotary engine whose energy is generated from moving water.
Hydrodynamic Bearing
A bearing which supports the shaft on a thin film of oil, the fluid-film layer is generated by journal rotation.
Hydrodynamic Lubrication
A lubrication film completely separates two load-bearing surfaces.
Hydroelectricity
Production of electricity by water power.
Hydroforming
A manufacturing process that involves pumping fluid into a die, so that the pressure will expand a tubular blank to take the form of the die.
Hydrogen Brazing
A method of furnace brazing in a hydrogen atmosphere.
Hydronic System
A re-circulating water system used for heating and/or comfort cooling.
Hydrostatic Bearing
A bearing which supports the shaft on a thin film of oil, the fluid-film layer is generated by externally applied pressure.
Hydrostatic Lubrication
A system of lubrication in which the lubricant is supplied under sufficient external pressure to separate the opposing surfaces by a fluid film.
Hypereutectic Alloy
Any binary alloy whose composition lies to the right of the eutectic on an equilibrium diagram, and which contains some eutectic structure.
Hypersonic
A range of speed that is five times or more the speed of sound in air.
Hypervelocity
A range of speed that is about 12 times or more the speed of sound in air.
Hypoeutectic Alloy
Any binary alloy whose composition lies to the left of the eutectic on an equilibrium diagram, and which contains some eutectic structure.
Hypoid Gear Lubricant
A gear lubricant having extreme pressure characteristics for use with a hypoid type of gear as in the differential of an automobile.
Hypoid Gears
Gears in which the pinion axis intersects the plane of the ring gear at a point below the ring-gear axle and above the outer edge of the ring gear, or above the ring-gear axle and below the outer edge of the ring gear.
Hysteresis
If the input varies from an initial point to a final point and then retraces its value back to the initial point, then the two paths of the output should be identical. If there is hysteresis in the system then the output paths will not coincide.
Hysteresis Damping
Hysteresis damping produces a force which is in phase with the velocity and proportional to the displacement, resulting in a linear equation of motion.
Hz
An abbreviation of hertz. The SI unit of frequency.
ID
Abbreviation of Inner Diameter.
Idler Gear
An idler gear may be used between two gears so that the direction of rotation on the two shafts is in the same direction.
Ignition Quality
The ability of a fuel to ignite when it is injected into the compressed-air charge in a diesel cylinder quantified by the cetane number.
Imbalance
Unequal radial weight distribution on a rotor system.
IMEP
During the cycle of an engine useful work is only done on the power stroke.
Impact Energy
A measure of the energy absorbed during the fracture of a specimen of standard dimensions and geometry when subjected to very rapid loading
Impact Test
A test to determine the behavior of materials when subjected to high rates of loading, usually in bending, tension or torsion.
Impeller
A device that imparts motion to a fluid.
Implosion
A violent inward collapse.
Independent Chuck
A chuck in which each jaw may be moved independently of the others.
Indicator Diagram
A plot of pressure vs. volume.
Induction Brazing
Bonding is produced by the heat obtained from the resistance of the work to the flow of induced electric current and by using a nonferrous filler metal.
Induction Hardening
Quench hardening in which the heat is generated by electrical induction.
Inert Gas
A gas which does not normally combine chemically with other elements.
Inerter
A two-terminal device in which the forces applied at the terminals are equal, opposite, and proportional to relative acceleration between the nodes.
Influent
The fluid entering a component.
Ingot
A steel casting that is cast into a mould which when solidified will be rolled in a blooming mill to plates and slabs for sheets.
Injection Moulding
A manufacturing process in which molten plastic is injected at high pressure into a mould.
Injector
A feedwater pump without moving parts that uses steam pressure and the Bernoulli effect to force feedwater into the boiler, even against its pressure.
In-Line Filter
A filter assembly in which the inlet, outlet and filter element axes are in a straight line and fitted in the supply or return pipe.
Inner Diameter
Dimension that defines the inside diameter of a cavity or hole.
Inside Caliper
An instrument used to measure the inside dimension of an object.
Instant Glue
More formally known as Cyanoacrylate.
Intercooler
A device which cools a gas between the compressive steps of a multiple stage compressor.
Interfacial Tension
The energy per unit area present at the boundary of two immiscible liquids.
Interference Fit
A fit between a hole and a shaft where there is always some interference between the two.
Interleaving
The placing of a sheet of paper between two adjacent layers of metal to facilitate handling and shearing of rectangular sheets, or to prevent sticking or scratching.
Intermittent Duty
A system that is not required to operate continuously.
Internal Force
Forces which hold an object together when external forces or other loads are applied.
Interpoles
Small auxiliary poles, placed between main field poles, whose magnetic field opposes the armature field and cancels armature reaction.
Interrupted Quenching
Quenching in which the metal object being quenched is removed from the quenching medium while the object is at a temperature substantially higher than that of the quenching medium.
Investment Casting
Also known as lost wax and precision casting, it is based on the use of a mould that is only used once.
Iris
The pigmented fibrovascular tissue known as a stroma. It is the most forward portion of the eye and the only one seen on superficial inspection.
Iron Foundry
A place where iron castings are made.
Ironing
Thinning the walls of deep drawn articles by reducing the clearance between punch and die.
Isolation
The prevention of unwanted interaction or leakage between components.
Isometric Diagram
A diagram showing the outline of a ship, aircraft, or equipment and the location of equipment and cable runs.
Isotensoid Structure
A filamentary structure in which the filaments are uniformly stressed throughout for the design loading condition.
Izod Test
A pendulum type of single-blow impact test in which the specimen, usually notched, is fixed at one end and broken by a falling pendulum.
j
j is used in engineering and physics to represent i the imaginary number.
Jack Shaft
A shaft used as a spacer between two points.
Jackbolt
A bolt or screw attached to the baseplate or foundation that is used to move or position the machine that is being moved.
Jackscrew
A bolt or screw attached to the baseplate or foundation that is used to move or position the machine that is being moved.
Jarno
A standard taper having 0.600 inch taper per foot used on some machine tools.
Jewellers Screwdriver
A small precision screwdriver.
Joint
Interface between two parts.
Joist
Horizontal wood framing member set from wall to wall to support the boards of a floor or ceiling.
Jominy Test
The Jominy test is used for determining end-quench hardenability.
Journal Bearing
A machine part in which a rotating shaft revolves or slides.
Junction
A connection between two or more parts.
Kapok
Used as an insulating or flotation material it comes from the seed hairs of the kapok tree (Ceiba Pentranda).
Kelvin Wedge
For waves in the wake of a boat (gravity waves). In this case the wedge semi-angle is independent of the speed of the body.
Kerf
The space from which metal has been removed by a cutting process.
Key
An element used to connect a rotating machine element to a shaft.
Keyed Joint
A joint in which one structural member is keyed or notched into an adjoining member as in timber construction.
Killed Steel
Steel treated with a strong deoxidizing agent.
Kiln
A furnace in which ceramics are fired.
kilopond
Another name for kilogram force.
Kinematics
A branch of mechanics dealing with the motion of rigid bodies without reference to their masses or the forces acting on the bodies.
Kink Test
Method for determining ductility of metal wire.
kip
Abbreviation of kilo pounds force.
kJ
An abbreviation of kilojoule, one thousand joules. The SI unit of energy is the joule.
Klinger Gauge Glass
A form of gauge glass where the water level is visible through a flat glass window in a strong metal frame, rather than a cylindrical tube.
Knot Strength
Tenacity of a fibre in which an overhand knot is tied.
Knurl
A decorative gripping surface of straight-line or diagonal design made by uniformly serrated rolls called knurls.
Knurling
The process of finishing a part by scoring or pressing patterns on the surface of the work.
kp
Abbreviation of kilopond, another name for kilogram force.
ksi
Abbreviation for kilo pounds per square inch.
l
The abbreviation of litre, a derived SI unit of volume.
Laminated
Made of thin layers.
Laminated Core
A core built up from thin sheets of metal insulated from each other.
Laminated Shim
A Shim made up of thin metal sheets soldered together but so that each layer can be easily peeled off.
Land
That surface on the periphery of a rotary cutting tool, such as a milling cutter, drill, tap, or reamer, which joins the face of the flute or tooth to make up the basic cutting edge.
Lap
A tool made of soft metal and charged with fine abrasives for precision finishing of metal surfaces.
Lap Joint
A joint between two overlapping members.
Lap Winding
An armature winding in which opposite ends of each coil are connected to adjoining segments of the commutator so that the windings overlap.
Lapping
A surface finishing operation used to achieve a fine polish and close tolerances.
Latch
A device that fastens one thing to another, but is subject to ready release so that the things may be separated.
Latten
Elizabethan term for brass, probably of Dutch origin.
Lead Hole
A starting hole for large drills to serve as a guide.
Lead Screw
A device for translating rotary motion into linear motion.
Lead
The lead of a helical gear tooth is the axial advance resulting from one full revolution of the helix on the cylinder.
Leaf Springs
Either a simple beam used as a spring or laminations of steel.
Lever
One of the basic tools that date from prehistoric times.
Lift
The lifting force on a flying object.
Lift Coefficient
A dimensionless value that allows the comparison of lift incurred by different sized and different shaped bodies. A positive lift coefficient represents lift, whilst a negative lift coefficient represents downforce.
Lifting Body
An aircraft that uses the shape of its body to generate lift instead of using wings.
Light Metal
One of the low-density metals, such as aluminum, magnesium, titanium, beryllium, or their alloys.
Lignum Vitae
A very hard wood.
Line of Action
The line of action of a force is the infinite line defined by extending along the direction of the force from the point where the force acts.
Linear Actuator
An actuator that creates motion in a straight line.
Linear Motion
Motion in a straight line.
Lip Seal
An elastomeric or metallic seal that prevents leakage in dynamic and static applications by a scraping or wiping action at a controlled interference between itself and the mating surface.
Liquidus
In a constitution or equilibrium diagram, the locus of points representing the temperatures at which the various compositions in the system begin to freeze on cooling or to finish melting on heating.
Live Centre
A centre that revolves with the work.
Load
The weight supported by a structure.
Load Bearing
Supporting a superimposed weight or force.
Load Carrying Capability
The maximum recommended payload that does not degrade the listed specifications for a mechanical stage.
Load-Deflection Diagram
Plot of load versus corresponding deflection.
Local Stress Relieving
Stress relieving heat treatment of a specific portion of a structure.
Locked Rotor Current
Steady state current taken from the line with the rotor at standstill.
Locked Rotor Torque
The minimum torque that a motor will develop at rest for all angular positions of the rotor.
Locking Pliers
A type of pliers with locking jaws that can be used as pliers, wrench, clamp, or small vice.
Logic Diagram
Representing the logical elements and their interconnections without necessarily expressing construction or engineering details.
Long Nose Pliers
Pliers with half round and tapered jaws.
Lost Foam Casting
A casting method using foamed plastic cores, giving the surface of the castings the appearance of styrofoam.
Lost Motion
Motion between a driving part and a driven part which does not move the driven part.
Lost Wax
Also known as investment or precision casting, it is based on the use of a mould that is only used once.
Lubricant
Any material interposed between two surfaces that reduces the friction or wear, or both, between them.
Lubricating Oil
A liquid lubricant, usually comprising several ingredients, including a major portion of base oil and minor portions of various additives.
Lubrication
Substance employed to reduce wear of one or both surfaces in close proximity and moving relative to each another.
Lubricator
A device which adds controlled or metered amounts of lubricant into a pneumatic system.
Luder Bands
Elongated surface markings or depressions in sheet metal caused by discontinuous yielding.
Machinability
The relative ease of machining a metal.
Machine
Any mechanical or electrical device that performs a task for people.
Machine Tool
A power-driven machine designed to bore, cut, drill, or grind metal or other materials.
Machinery Train
Three or more machines that must be aligned to one another.
Machinery Vibration
The vibration of rotating machinery may infer certain defects.
Macrostructure
The structure of metals as revealed by examination of the etched surface of a polished specimen at a magnification not exceeding ten diameters.
Magnetic Bearing
A bearing that separates comparative rotating surfaces through the use of a magnetic field.
Magnetic Gears
Non-contact gears that offer a number of advantages over standard gear sets.
Magnetic Particle Inspection
A nondestructive method of inspection for determining the existence and extent of possible defects in ferromagnetic materials.
Magnetic Seal
A seal that uses magnetic material, instead of springs or bellows, to provide the closing force.
Magnetic Separator
A separator that uses a magnetic field to attract and hold ferromagnetic particles.
Malleable
Capable of being extended or shaped by hammering or rolling.
Mandrel
A precision-made tapered shaft to support work for machining between centres.
Manhole
An oval access door into the boiler shell, used for maintenance and cleaning.
Manifold
A pipe/volume with a number of inlet and outlet pipes.
Manometer
A U-shaped glass tube, partly filled with a liquid, water or mercury, employed to measure pressure.
Marble
A granular metamorphosed limestone that is often polished and used for decoration.
Mass
The SI unit of mass is the kilogram.
Material
A physical substance used as an input to production or manufacturing.
Materials
Lists all Materials topics in the Encyclopaedia
Mathematical Model
A mathematical representation of a process or physical object.
Mean Stress
Algebraic difference between maximum and minimum stress in one cycle of fluctuating loading, as in a fatigue test.
Measurement
The collection of quantitative data.
Mechanical Engineer
An engineer who applies the principles of mechanics and energy to the design of machines and devices.
Mechanical Engineering Books
Lists all Mechanical Engineering Books in the Encyclopaedia
Mechanical Engineering Calculations
Lists all Mechanical Engineering Calculations in the Encyclopaedia
Mechanical Engineering Conversions
Lists all Mechanical Engineering Conversions in the Encyclopaedia
Mechanical Engineering Weblinks
Lists all Mechanical Engineering Weblinks in the Encyclopaedia
Mechanical Filter
A device to remove dirt and other impurities from air, oil, or water.
Mechanical Impedance
The mechanical properties of a machine system (mass, stiffness, damping) that determine the response to periodic forcing functions.
Mechanical Properties
The properties of a material that reveal its elastic and inelastic behaviour where force is applied.
Mechanical Seal
A device which works to join together systems or mechanisms in order to prevent leakage, contain pressure or exclude contamination.
Mechanism
Rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission.
Mechanisms
Lists all Mechanisms topics in the Encyclopaedia
Mechatronics
The introduction of electronic controls into mechanical components.
Membrane
A thin sheet or layer.
Membrane Structure
A shell structure, that does not take wall bending or compression loads.
Mesh
To engage as the teeth between two gears.
Metal
A metal is a substance that conducts heat and electricity, is shiny and reflects many colors of light, and can be hammered into sheets or drawn into wire.
Metal Alloy
Metal blended with some other metallic or non-metallic substance to give it special qualities.
Metal Inert Gas Welding
Filler rod as a consumable electrode, and the rod is automatically fed.
Metallurgy
The science and technology of metals and alloys.
Metalworking Lubricant
A liquid used to cool and lubricate the cutting to improve the work surface finish.
Metric Horsepower
Also known as Cheval Vapeur.
Metrology
The science of dimensional measurement; sometimes includes the science of weighing.
Micrometer
An instrument used to measure the size of a body.
MIG Welding
Abbreviation of Metal Inert Gas Welding.
mil
One thousandth (0.001) of an inch.
Mill
A milling machine. Also, the act of performing an operation on the milling machine.
Mill Edge
The edge of strip, sheet or plate in the as rolled state.
Mineral Wool
Also known as rock wool.
Minimum Bend Radius
Minimum radius to which a sheet or wire can be bent to a specified angle without failure.
Mitre Joint
Pieces are cut on an angle to make a joint.
Mixed Lubrication
A combination of hydrodynamic and boundary lubrication.
Mobility
The ratio of the carrier velocity to the applied electric field.
Model
A copy of an object that is n times smaller than the fullsize object.
Model Engineering
Lists all Model Engineering topics in the Encyclopaedia
Modulating Valve
A valve which can be positioned anywhere between fully on and fully off to proportion the rate of flow in response to a modulating controller.
Module
The measurement that architects use to determine the proportions of a structure, for example, the diameter of a column.
Modulus in Bending
Ratio of maximum fibre stress to maximum strain, within elastic limit of stress-strain diagram obtained in flexure test.
Modulus of Elasticity
The modulus of elasticity is the slope of the stress-strain diagram in the linear region.
Modulus of Elasticity in Shear
Another name for Shear Modulus.
Modulus of Rigidity
Another name for Shear Modulus.
Modulus of Rupture
Breaking strength in a non-ductile solid as measured by bending.
Modulus of Strain Hardening
Rate of change of true stress as a function of true strain in a material undergoing plastic deformation.
Mohs
A hardness scale developed by F. Mohs in 1812 where the hardness of a material is compared with that of a mineral.
Mole Grips
A type of pliers with locking jaws that can be used as pliers, wrench, clamp, or small vice.
Moments of Inertia
Principal axes for bodies of uniform density.
Monel
Strong and corrosion resistant. Applications include: turbine blades, propellers, pump fittings, ...
Monocoque
A type of construction in which all or most of the stresses are carried by the skin.
Morse Taper
A self-holding standard taper largely used on small cutting tools.
Mortise
A cavity or hole cut to allow a tennon to pass through to make a joint.
Motive Power
A natural agent, as water, steam, wind, electricity, etc., used to impart motion to machinery; a motor; a mover.
Motor
A mechanism doing work by means of a ready source of energy, such as electric current, compressed air, or oil under pressure.
mpg
Abbreviation of mile per gallon.
MTBF
The average time between failures for a continuously operating system.
MTTF
The measured operating time of a system or component divided by the number of failures that occurred during that time.
Mud Drum
A water drum, particularly one mounted low on the boiler whose function is primarily to trap mud from circulation.
Mudhole
A small manhole, too small for access but used for washing out the boiler, either as an inlet for a water hose or as a drain to remove mud.
Muffler
An acoustic filter element used to reduce sound pressure levels inside a duct.
Multiple Disc Clutch
Multiple plates on input and output shafts are brought together to transmit torque. The multiple plates increases the frictional area.
Muntz Metal
Stonger than normal brass and used for castings and hot worked items. 60 % Copper 40 % Zinc

Music Wire
Another name for piano wire, a high quality steel wire used for making springs.
Nail Hammer
A hammer designed to hit the head of nails and usually has a claw device which allows for the removal of nails.
Nameplate Rating
The full-load continuous rating of a generator or other electrical equipment under specified conditions as designated by the manufacturer, and written on the nameplate.
Natural Frequency
The frequency of free vibration of a system.
Naturally Aspirated
An engine that draws air in without the assistance of a supercharger or turbocharger.
Naval Brass
A brass made with 60% copper 40% zinc with 1% tin added for extra corrosion resistance.
NCAP
The U.S. government “crash testing” program.
Nd2Fe14B
Chemical formula for Neodymium Iron Boron.
NdFeB
Abbreviation of Neodymium Iron Boron.
Necking
Reduction of the cross-sectional area of a material in a localized area caused by uniaxial tension.
Needle Nose Pliers
Pliers with half round and tapered jaws. Also known as Long Nose Pliers.
Needle Roller Bearing
A special bearing which has a small OD when compared to its ID.
Needle Valve
A form of globe valve that contains a sharp pointed, needle like plug that is driven into the and out of a cone shaped seat to accurately control a relatively small rate of flow of a fluid.
Neut Number
Abbreviation for Neutralization Number.
Neutral Flame
A gas flame in which the oxygen and acetylene volumes are balanced and both gases are completely burned.
Neutral Plane
Plane through a beam where compression and tension stresses are zero.
Neutralization Number
The specific quanity of reagent required to neutralize the acidity or alkalinity of a lube sample.
New Car Assessment Program
The U.S. government “crash testing” program.
Nickel Silver
Copper nickel zinc alloy.

NIMEP
The ratio of net work per cycle to cylinder volume displaced per cycle.
Nimonic
An alloy consisting of roughly 80% nickel and 20% chromium with additives such as titanium and aluminium.
Nitrating
A case hardening process in which ammonia or some other form of nitrogen is introduced to the surface of certain alloys.
Nitrous Oxide
Also known as laughing gas, an anaesthetic.
Node
A point or line on a vibrating structure that remains stationary.
Nominal Size
A designated size that may be different from the actual size.
Nominal Stress
Stress calculated on the basis of the net cross section of a specimen without taking into account the effect of geometric discontinuities such as holes, grooves, fillets, etc.
Nonbearing
Not carrying a load.
Non-Contact Bearing
A bearing in which no solid contact occurs between relatively moving surfaces.
Non-Destructive Testing
A method in which the part is stimulated and its response measured quantitatively or semiquantitatively.
Nonferrous
Metals which contain no iron. Aluminum, brass, bronze, copper, lead, nickel, and titanium are nonferrous.
Normal Stress
Stress acting perpendicular to an imaginary plane cutting through an object.
Normalizing
Heating a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.
NVH
Commonly used abbreviation for Noise, Vibration and Harshness
Octane Number
A rating of the 'knock' characteristics of motor fuels.
OD
Abbreviation of Outside Diameter.
OEM
Abbreviation of Original Equipment Manufacturer.
Off Centre
Not centred; offset, eccentric, or inaccurate.
Oil
An oil is any substance that is in a viscous liquid state at ambient temperatures or slightly warmer, and is both hydrophobic and lipophilic.
Oil Canning
A dished distortion in a flat or nearly flat surface.
Oil Detergent
Designed to chemically neutralize acidic contaminants in the oil before they become insoluble and fall out of the oil, forming a sludge.
Oil Groove
A channel or channels in a bearing to improve oil flow through the bearing.
Oil Hardening
A process of hardening a ferrous alloy of suitable composition by heating within or above the transformation range and quenching in oil.
Oil Mist
A means of lubricating by injecting oil into an air stream producing a finely atomized spray.
Oil Mist Lubrication
A method of lubricant delivery in which oil is piped throughout the machine to desired locations and dispensed with a spray nozzle.
Oil Seal
Device used to prevent oil leakage past a certain area.
Oil Whirl/Whip
An unstable free vibration whereby a fluid-film bearing has insufficient unit loading.
Oilstones
Moulded abrasives in various shapes used to hand-sharpen cutting tools.
Oldham Coupling
A double slider connection used to connect shafts which have only lateral misalignment.
Olive Oil
Obtained from the fruit of Olea Europaea.
Operating Pressure
Pressure at which a system is operating.
Operating Stress
Stress imposed on a part in service.
Optical Alignment
A secondary alignment method for determining on-line and off-line changes in alignment conditions.
Orifice
Accurate size opening for controlling fluid flow.
Original Equipment Manufacturer
Products supplied by the company which first created the product.
Overhung Load
The load exerted perpendicular to the shaft when a sprocket, pulley or gear is mounted on the shaft.
Overrun
Often used to describe the condition where rotating machinery is in a coast down condition.
Overspeed Protection
A system that operates at a given machine speed to reduce the chance of damage which may occur at a higher speed.
Overstressing
Application of high fluctuating loads at the beginning of a fatigue test and lower loads toward the end.
Oxidizing Flame
An oxyacetylene flame in which there is an excess of oxygen.
Oxyacetylene Welding
A welding process in which the required temperature is attained by flames obtained from the combustion of acetylene with oxygen.
Oxygen Cutting
A process of cutting ferrous metals by means of the chemical action of oxygen on elements in the base metal at elevated temperatures.
P
The abbreviation of poise, the CGS derived unit of dynamic viscosity of a fluid.
Packing
A material used to seal a joint against leakage or to displace one part relative to another.
Panel Hammer
A special hammer for metalworking.
Paper
Made by pressing a pulp of rags, straw and wood into thin sheets.
Paper Glue
Many different forms of paper glue, the most common being the solid stick form.
Paris Bronze
A term given to brass containing 88% copper, 10% zinc and 2% lead used to produce trinkets and souvenirs.
Parting
When used in lathe or screw-machine operations, this process separates a completed part from chuck-held or collet-fed stock by means of a very narrow, flat-end cutting, or parting, tool.
Passivation
The process of rendering a metal surface chemically inactive, either by electrochemical polarization or by contact with a passivating agent.
Passivator
A type of corrosion inhibitor that appreciably changes the potential of a metal to a more positive value.
Peak Torque
Maximum amount of torque an engine can produce.
Pedestal Bearing
A bearing that is supported on a column or pedestal rather than on the main body of the machine.
Peel Strength
Strength of an adhesive bond obtained by stress applied in a peeling mode.
Peen Hammer
A body hammer with a pein of triangular section with a fairly sharply shaped end.
Peening
The mechanical working of metals by means of hammer blows.
Peierls Stress
The stress required to move a dislocation.
Pein Hammer
A body hammer with a pein of triangular section with a fairly sharply shaped end.
penetrant inspection
A method of nondestructive testing for determining the existence and extent of discontinuities that are open to the surface in the part being inspected.
Pewter
Tin-base white metal containing antimony and copper: 1 to 8% Sb and 0.25 to 3% Cu.
Phase Diagram
Graphical representation of the temperature and composition limits of phase fields in an alloy or ceramic system.
Phase Transformation
Changes that can occur within a given material system.
Phonon
A single quantum of vibrational or elastic energy.
Pick Hammer
A hammer with a round head for conventional planishing and a small pick-shaped head for working away in sharp or tight corners.
Pickling
The chemical removal of surface oxides and other contaminants from a material by immersion in an aqueous acid solution.
Piezoelectric
Any material which provides a conversion between mechanical and electrical energy.
Pilot Hole
A starting hole for large drills to serve as a guide.
Pin Connection
In two dimensions, a pin connection restrains two translation degrees of freedom but does not restrain rotation.
Pinion
The smaller of two mating or meshing gears. Can be either the driving or the driven gear.
Pipe
A hollow cylinder following certain dimension rules.
Pitch
Pitch is the distance between the teeth on a gear.
Pitch Circle
The effective working circle of a gear which would be obtained if a pair of gears were replacedwith disks that transmitted the same motion in the same package space through contact friction.
Pitting
Localized corrosion of a metal surface, confined to a point or small area, that takes the form of cavities.
Plain Bearing
A relatively simple and inexpensive bearing typically made of two parts. A rotary plain bearing can be just a shaft running through a hole.
Plain Cutter
A milling cutter with cutting teeth on the periphery only.
Planing
Machining operation that creates flat surfaces.
Plaster of Paris
Partly dehydrated gypsum.
Plastic Deformation
Deformation that is permanent or nonrecoverable after release of the applied load.
Plastic Flow
Alternate name for Plastic Deformation.
Plastic Strain
Alternate name for Plastic Deformation.
Plastic Strain Ratio
Ratio of the true width strain to the true thickness strain.
Plasticity
The inverse of elasticity. A material that tends to stay in the shape or size to which it is deformed has high plasticity.
Plasticity Number
Index of the compressibility of rubber at elevated temperatures.
Plasticizer
A low molecular weight polymer additive that enhances flexibility and workability and reduces stiffness and brittleness.
Pleated Filter
A filter element whose medium consists of a series of uniform folds and has the geometric form of a cylinder, cone, disc, plate, etc.
Plenum
Air compartment connected to a duct or ducts.
Pliers
A gripping tool with two hinged arms and serrated jaws.
Plumb
Exactly vertical.
Plunger
The long piston of a single-acting pump, such as a fuel-injection pump.
Pneumatic
Operated by air pressure.
Point Mobility
The velocity at a point per unit force at the same point and same direction.
Poissons Ratio
Ratio of strain in the lateral direction to strain in the axial direction.
Pole Piece
The shaped magnetic material upon which the stator windings of motors and generators are mounted or wound.
Polymorphism
Different crystal structures at different temperatures or pressures for a single compound.
Pop Valve
A spring loaded safety valve that opens automatically when pressure exceeds the limits for which the valve is set.
Porcelain
Made from china clay, a clay consisting mainly of kaolinite.
Pore Size Distribution
The ratio of the number of effective holes of a given size to the total number of effective holes per unit area expressed as a percent and as a function of hole size.
Porosity
The presence of gas pockets within a solid material.
Porous Bearing
Made from porous material, such as compressed metal powders, the pores acting either as reservoirs for holding or passages for supplied lubricant.
Port
An opening hole, or passage.
Positive Displacement Pump
A pump that moves a measured quantity of fluid with each stroke of a piston or each revolution of vanes or gears.
Pour Point
Low-temperature flow indicator and is 3°C above the temperature to which a normally liquid petroleum product maintains fluidity.
Pour Point Depressant
An additive which retards the adverse effects of wax crystallization, and lowers the pour point.
Pour Stability
The ability of a pour depressed oil to maintain its original pour point when subjected to long-term storage at low temperature approximating winter conditions.
Power Curve
Graphical representation of the changing relationship between speed and revolutions per minute (RPM).
Power Density
Characteristic parameter of a battery/electrical power source indicating its electrical power per unit weight or volume.
Power Spectral Density
A method of scaling the amplitude axis of spectra of random rather than deterministic signals.
Power to Weight Ratio
The power produced by a machine divided by the weight of the machine.
Prandtl Number
A dimensionless group often used in heat exchange calculations.
Precession
A modern term, derived from the precession of the equinoxes and meaning a motion around a cone of the rotation axis of a spinning body.
Precision Casting
Also known as investment or lost wax casting, it is based on the use of a mould that is only used once.
Prepreg
A continuous fibre reinforcement pre-impregnated with a polymer resin which is then partially cured.
Pressure
Defined as the force exerted per unit area.
Pressure Welding
Any welding process or method in which pressure is used to complete the weld.
Pressurized
Containing air, or other gas, at a pressure higher than ambient.
Pre-Stressed Concrete
A method of construction whereby compression forces are applied to concrete elements with the goal of counteracting the tension that would otherwise occur due to loads.
Prick Punch
A solid punch with a sharp point, used to mark centres or other locations on metal.
Profile
The gear tooth profile is the line which defines the tooth shape in a cross-section of the gear perpendicular tothe plane of rotation.
Projectile Motion
A type of motion that occurs near the surface of the Earth when the only force acting on the object is that of gravity.
Prony
Unit of power.
Proof Stress
Stress that will cause a specified permanent deformation.
Proportional Limit
The point on a stress-strain curve at which the straight line proportionality between stress and strain ceases.
Propulsion
Process by which something can be moved by producing a reaction with a force of thrust.
PS
Metric horsepower
psi
An abbreviation of pounds per square inch, a British imperial unit of pressure. 1.0 psi = 6894.757 Pa
psia
Gauge pressure plus local atmospheric pressure.
psid
Difference between two pressures.
psig
Difference between the measuring point and the local pressure.
psisg
psi sealed gauge; difference between a chamber of air sealed at atmospheric pressure and the pressure at the measuring point.
psivg
psi vented gauge; difference between the measuring point and the local pressure.
PTFE
Abbreviation of Polytetrafluoroethylene, a thermoplastic polymer used for non-stick coatings and bearings.
Pump
Electrical source of the energy required to vary the capacitance of a parametric amplifier.
Pump Down
The act of using a compressor or a pump to reduce the pressure in a container or a system.
Pusher Seal
A mechanical seal in which the secondary seal is pushed along the shaft or sleeve to compensate for misalignment and face wear.
PV Diagram
A plot of pressure vs. volume.
Pyrometer
A device for measuring the high temperatures in a furnace.
Q
The quality factor defines the sharpness of resonance.
Quart
A unit of volume.
Quarter Wave Tube
A resonator used most commonly on automotive air intake systems to reduce resonance.
Quasi Static
Refers to forces or displacements which vary slowly with time.
Quench Hardening
Hardening a ferrous alloy by austenitizing and then cooling rapidly enough so that some or all of the austenite transforms to martensite.
Quenching
Rapid cooling.
Quenching Oil
A high-quality, oxidation-resistant petroleum oil used to cool metal parts during their manufacture, and is often preferred to water because the oil′s slower heat transfer lessens the possibility of cracking or warping of the metal.
Quick Disconnect Coupling
A coupling which can quickly join or separate a fluid line without the use of tools or special devices.
Quill Shaft
A shaft with splines. A male spline on one shaft fits with a female spline on a second shaft and allows the transmission of torque.
RAC Horsepower Rating
An obsolete engine horsepower rating system that was used as a designation as to the power of an engine.
Rack and Pinion
A pair of gears which convert rotational motion into linear motion.
Racking
The distortion of a rectangular shape to a skewed parallelogram.
Radial
A direction perpendicular to the centreline of a shaft.
Radial Force Variation
Radial Force Variation is a dynamic force generated at the wheel due to tyre non-uniformity.
Radial Position
The average location, relative to the radial bearing centreline, of the shaft′s dynamic motion.
Radiated Noise
The dissemination of sound energy as acoustic waves from a source (e.g. a vibrating panel, running engine etc.).
Random Vibration
A vibration whose instantaneous magnitude is not specified for any given instant of time.
Random Wound Stator
The stator windings are wound onto a bobbin without a defined structure to the windings.
Rankine Vortex
An idealized vortex in unbounded fluid with uniform vorticity inside a circular patch and zero vorticity outside.
Rankine-Hugoniot Shock Relations
These are solutions for a steady, normal shock in the frame moving with the shock front.
Rasp
A sort of blowing noise emitted often from the exhaust pipes of internal combustion engines, usually, it is dominated by a mixture of 4E, 6E and 8E engine orders on 4 cylinder engines.
Ratchet
A mechanism that only allows rotary motion in one direction.
Rate of Strain Hardening
Alternative name for Modulus of Strain Hardening.
Rated Flow
The maximum flow that the power supply system is capable of maintaining at a specific operating pressure.
Rated Pressure
The qualified operating pressure which is recommended for a component or a system by the manufacturer.
Rayleigh′s Method
A method used for calculating approximate natural frequencies for a vibrating system assuming a deflected shape and balancing kinetic and strain energies.
Reaction
A reaction is a force exerted by a support on an object: sometimes called support reaction.
Reactive Absorber
A sound absorber, such as the Helmholtz resonator which involves the effects of mass and compliance as well as resistance.
Real Modes
In a real mode, all points on the structure reach a maximum or a minimum value at the same time and all pass through equilibrium at the same time.
Receptance
Displacement per unit force.
Reciprocating
Having a back-and-forth or up-and-down linear motion, such as an engine piston.
Reciprocating Air Compressor
Air compressor in which the compressing element is a piston having a reciprocating motion in a cylinder.
Recrystallization
The formation of a new set of strain-free grains within a previously cold-worked material; normally an annealing heat treatment is necessary.
Recrystallization Annealing
Annealing cold worked metal to produce a new grain structure without phase change.
Recrystallization Temperature
The approximate minimum temperature at which complete recrystallization of a cold worked metal occurs within a specified time.
Reduction of Area
Measure of the ductility of metals obtained in a tensile test.
Reference Oil
An oil of known performance characteristics, used as a basis for comparison.
Refractory
A metal or ceramic that may be exposed to extremely high temperatures without deteriorating rapidly or without melting.
Reinforced Concrete
Steel bars embedded in concrete and designed to take the tension that occurs on account of loads.
Reinforcing
Where a structure such as a girder or a concrete slab has been strengthened or stiffened by extra material or by the addition of trusses.
Relief Valve
A valve held closed by a spring and forced open when the pressure in the system rises above the desired limit.
Renewable Energy
Energy obtained from sources that are essentially inexhaustible, unlike fossil fuels.
Repeatability
The consistency (or variation) of readings and results between consecutive sets of measurements.
Reservoir
A container for storage of liquid in a fluid power system.
Residual Elongation
Measure of ductility of plastics.
Residual Stress
Internal stress in a material often resulting from thermal or mechanical straining.
Resistance Brazing
Bonding is produced by the heat obtained from resistance to the flow of electric current in a circuit of which the workpiece is a part.
Resistance Welding
A welding process in which the work pieces are heated by the passage of an electric current through the contact; this includes spot welding, seam or line welding, and percussion welding; flash and butt welding are sometimes considered as resistance welding processes.
Revolutions per Minute
Unit to describe the rate of rotation of a body.
Revolutions per Second
Unit to describe the rate of rotation of a body.
Reyn
British unit of dynamic viscosity.
Reynolds Number
This is a non-dimensional number (consistent units) which describes whether fluid flow is laminar, turbulent, or transitional between the two.
Rigid
An idealized concept meaning something which does not deform under loading.
Rigid Connection
In two dimensions, a fixed connection between two members restrains all three degrees of freedom of the connected member with respect to one another.
Rigid Joint
Prevents adjacent parts from moving or rotating past one another.
Ring Grooves
Grooves cut in the piston barrel to hold the piston rings.
Ripping Hammer
A hammer which looks like a claw hammer, but the claw is straight.
Riveting Hammer
A hammer with a special head for securing rivets.
Rivets
A permanent fixing used to join plates. The unheaded end is forged or flattened.
Rocker Arm
A lever that transmits the action of the cam, usually by means of a push rod, to the stem of the intake or exhaust valve, sometimes also to the starting-air valve and fuel valve.
Rocket Sled
A sled that runs on a rail or rails and is accelerated to high velocities by a rocket engine.
Rocking Grate
An advanced form of firebar.
Roller Bearing
A bearing in which the relatively moving parts are separated by rollers.
Roller Joint
Allows adjacent parts to move controllably past one another.
Roller Support
In two dimensions, a roller support restrains one translation degree of freedom.
Rolling Drag
Another name for Rolling Resistance.
Rolling Friction
Another name for Rolling Resistance.
Rolling Resistance
The resistance that occurs when a round object such as a ball or tire rolls on a flat surface.
Rotary Pump
A pump that moves fluid by positive displacement, using a system of rotating vanes, gears, or lobes.
Rotating Field
The magnetic field in a multiphase ac motor that is the result of field windings being energized by out-of-phase currents.
Rotating Seal
When the spring loaded or moveable portion of the seal rotates with the shaft.
Rotation
Motion of an object where the path of every point is a circle or circular arc.
Rotational Play
Looseness, usually in a coupling, where a rotor can rotate a given distance before the rotational play is out and the coupled shaft begins to rotate also.
Rotor
A rotating part.
Rough Machining
Removing excess material with a machine tool thus shaping it in preparation for finish machining.
Roughing
The fast removal of stock to reduce a workpiece to approximate dimensions. leaving only enough material to finish the part to specifications.
rpm
Abbreviation of revolutions per minute.
rps
Abbreviation of revolutions per second.
Rubber Mallet
A hammer with a rubber head.
Rubbing Bearing
A bearing in which the relatively moving parts slide without deliberate lubrication.
Running Fit
A class of fit intended for use on machinery with moderate speeds, where accurate location and minimum play are desired.
Runout
A change in dial indicator position at the surface of the rotor during one rotation of the rotor, used to measure out-of-roundness or indicate a bent shaft.
Rupture
Failure that is accompanied by significant plastic deformation.
Rupture Strength
Nominal stress developed in a material at rupture.
Rust
A corrosion product consisting of hydrated oxides of iron. This term is only applied to ferrous alloys.
Sacrificial Anode
Coupling of a more active metal to a structure resulting in a galvanic current flow through the corroding electrolyte.
SAE Steel
Steel manufactured under the specifications by the Society of Automotive Engineers.
Safety Valve
An automatic valve used to release excess pressure within the boiler.
Sag
Deflection due to gravity acting on a cantilevered or otherwise supported object.
Sagging
The tendency of a beam to bend downwards, when acted on by a load, including its own weight.
Sand Casting
The formation of shapes by pouring molten metal into a cavity shaped in sand.
Sand Scratches
The marks left in metal or in the old finish by abrasives.
Sandblasting
A process of blowing sand by compressed air with considerable force through a hose against an object.
Sanding
The process of using an abbrasive paper to remove material, create a shape or to smooth and surface.
Sandpaper
An abrasive paper used to smooth the rough edges of freshly sawn wood.
Scarf Joint
A joint that is formed by cutting opposing tapered ends on each member which are then fitted together.
Scoring
Distress marks on sliding metallic surfaces in the form of long, distinct scratches in the direction of motion.
Scraper
A hardened steel hand tool used to scrape surfaces very smooth by removing minute amounts of metal.
Screw Pump
Compressor constructed of two mated revolving screws.
Scribe
A steel rod 8 to 12 inches long and about 3/16 inches in diameter. It has a long, slender, hardened steel point on one or both ends.
Scuffing
Abnormal wear due to localized welding and fracture. It can be prevented through the use of antiwear, extreme-pressure and friction modifier additives.
Scuffing Particles
Large twisted and discolored metallic particles resulting from adhesive wear due to complete lubricant film breakdown.
Scum Valve
A blow-down valve mounted at the water-level of a boiler, used to blow-down lighter oily or foamy deposits within a boiler that float on the water-level.
Seal
A device designed to prevent the movement of fluid from one area to another, or to exclude contaminants.
Seal Assembly
Assembly that includes sealing surfaces, provision for initial loading and a mechanism that accommodates the radial and axial movement necessary for installation and operation.
Seal Chamber
The area between the seal chamber bore and a shaft in which a mechanical seal is installed.
Seal Face
Either of the two surfaces in a mechanical seal assembly forming the primary seal.
Second Class Lever
The load is situated between the fulcrum and the applied force.
Secondary Alignment
The act of measuring off-line to on-line machinery movement.
Seizure
Welding between surfaces in relative motion that results in immobilization of the parts.
Self-Aligning Bearing
A roller-element bearing with one spherical raceway that automatically provides compensation for shaft or housing deflection or misalignment.
Servo Motor
An ac or dc motor used in servo systems to move a load to a desired position or at a desired speed.
Servo System
An automatic feedback control system that compares a required condition with an actual condition and uses the difference to drive a control device to achieve the required condition.
sg
Abbreviation of specific gravity.
Shaft
On which something rotates.
Shaft Seal
Device used to prevent leakage between shaft and housing.
Shake Table Test
A laboratory test for vibration tolerance, in which the device to be tested is placed on a vibrator.
Shaker
An electromagnetic device capable of imparting known vibratory acceleration to a given object.
Shank
That part of a tool or similar object which connects the principal operating part to the handle, socket, or chuck by which it is held or moved.
Shear
A force that causes parts of a material to slide past one another in opposite directions.
Shear Modulus
The shear modulus is related to the Young's modulus and Poisson′'s ratio.
Shear Strength
Maximum shear stress that can be sustained by a material before rupture.
Shear Stress
Stress in the cross-sectional plane of a material that is in the same plane as the shearing force acting on it.
Shim
A thin sheet of metal or other material which is inserted between two machine parts to obtain their correct relative location.
Shim Machine
The machine whose position is changed during shaft alignment.
Shock Absorber
A unit that adds damping to the relative motion of two parts.
Shore Durometer
Durometer is typically used as a measure of hardness in polymers, elastomers and rubbers.
Shot Blasting
Cleaning surface of metal by air blast, using metal shot as an abrasive.
Shot Peening
Similar to sandblasting, except that it operates by the mechanism of plasticity rather than abrasion.
Shrinking Hammer
A special hammer with faces shaped to allow for correction of locally stretched sheet metal.
Shunt
The transient response of the body to changes in the engine mean torque transmitted to the road wheel by the driveshafts.
SiC
Silicon Carbide, used extensively as a grinding compound and in abrasive wheels.
Silencer
An acoustic filter element used to reduce sound pressure levels inside a duct.
Sintering
Heating a mass of fine particles for a prolonged time below the melting point, usually to cause agglomeration.
Skin Friction
This is drag due to the surface texture and area.
Sledge Hammer
A large, heavy hammer usually with a long handle.
Sleeve Bearing
A journal bearing, usually a full journal bearing.
Slide Bearing
A bearing used or positioning a slide or for axial alignment of a long rotating shaft.
Slide Hammer
A tool with a long round shaft on which a hammer weight slides.
Slip Rings
Devices for making electric connections between stationary and rotating contacts.
Smokebox
An enclosed space at the extremity of a fire-tube boiler, where the exhaust gases from the tubes are combined together and pass to the flue or chimney.
S-N Diagram
Plot of stress (S) against the number of cycles (N) required to cause failure of similar specimens in a fatigue test.
Snipe Nose Pliers
Pliers with half round and tapered jaws. Also known as Long Nose Pliers.
Snug Torque
The torque required to pull plates together so that direct contact occurs. Often used in angle control tightening.
Snugging
The process of pulling parts of a joint together, most of the input turn during this process is absorbed in the joint with little tension being given to the bolt.
Socket Wrench
A tool with socket end or a drive tool combined with a socket.
Soft Foot
A term used to describe any condition where tightening or loosening the bolts of the machine feet distorts the machine frame.
Soft Solder
Solder composed of 50% Tin and 50% Lead
Solder
A low melting point alloy that can wet copper, conduct current, and mechanically join conductors.
Soldering
Process of joining metallic surfaces with solder without melting the base material.
Solenoid
An electromagnetic device that changes electrical energy into mechanical motion.
Solution Heat Treatment
Heating an alloy to a suitable temperature, holding at that temperature long enough to allow one or more constituents to enter into solid solution, and then cooling rapidly enough to hold the constituents in solution.
Solvus
The curve on a phase equilibrium diagram that defines the limits of solid solubility.
Spacer Washer
A sheet of metal or other material placed between two surfaces to reduce clearance or to provide a better surface for a fastener.
Spall
Small chips or fragments which are sometimes given off by electrodes during the welding operation.
Specific Fan Power
The energy efficiency of fan air movement systems.
Speculum
A copper-tin alloy with 33 to 45% of tin that has very high optical reflectivity when polished.

Spinodal Structure
A fine homogeneous mixture of two phases that form by growth of composition waves in a solid solution during suitable heat treatment.
Spiral Gear
When the helical gears are not aligned so the axles are parallel they are known as spiral gears.
Spirit Level
A tool for testing if a surface is level using a glass tube containing an air bubble.
Splash Lubrication
A system of lubrication in which parts of a mechanism dip into and splash the lubricant onto themselves and or other parts of the mechanism.
Splice
A joint formed by the connecting of two or more parts.
Spring Rate
Force per unit distance of compression or extension of a spring.
Springback
Degree to which a material returns to its original shape after deformation.
Springs
The physics of simple springs - helical and beam forms.
Sprues
The channels cut into a mould to allow material to flow in. Also, the name given to the parts formed by the channels when the parts are removed.
Spur Gear
A gear having teeth parallel to the axis of the shaft on which it is mounted.
Square Surface
A surface at a right angle with another surface.
Squirrel Cage Windings
A type of rotor winding in which heavy conductors are embedded in the rotor body.
St
Abbreviation of stokes, the CGS unit of kinematic viscosity.
Stall Torque
The maximum torque without burning out the motor.
Standard Temperature and Pressure
Often abbreviated as stp or STP it is a temperature of 0°C and a pressure of 101325Nm-2.
Standard Wire Gauge
A numbering system for standard wire diameters, often abbreviated as SWG.
Static Seal
A seal between two surfaces which have no relative motion.
Static Stiffness
A measurement of the rigidity of a structure to a constant force, defined as the deflection per unit force of input.
Statically Determinate
A statically determinate structure is one where there is only one distribution of internal forces and reactions which satisfies equilibrium.
Statically Indeterminate
A statically indeterminate structure is one where there is more than one distribution of internal forces and/or reactions which satisfies equilibrium.
Stationary Seal
A mechanical seal in which the flexible members do not rotate with the shaft.
Stator
The stationary part of a rotating electrical machine.
Steam Drum
A cylindrical vessel mounted at a high point of a water-tube boiler.
Steam Quality
The percentage by weight of vapour in a steam and water mixture.
Steering Offset
The distance from the point where the steering axis intersects the ground to the longitudinal line that runs through the centre of the tyre′s contact patch.
Step Bearing
A plane surface bearing that supports the lower end of a vertical shaft.
Step Stressing
stresses in a series of pre-selected increments.
Sthene
The unit of force in the metre-tonne-second system.
Stiction
Stiction can be defined as a form of friction which is resistance to the start of movement.
Stiffness
Stiffness is the ratio of change of force (or torque) to the corresponding change in translation (or rotational) deflection of an elastic element.
Stokes
The CGS unit of kinematic viscosity. Abbreviated as St. 1St=1x10-4m2s-1.
Straight-Cut Gear
A gear with teeth cut around the perimeter that are inline with the shaft on which it rotates.
Strain Point
Temperature at which internal stress in glass is substantially relieved in about 1 hour.
Strain Rate
Time rate of elongation.
Strainer
A coarse filter element.
Strength Reduction Ratio
Alternate term for fatigue notch factor.
Stress
Defined as the force per unit area of cross-section.
Stress Amplitude
One-half the range of fluctuating stress developed in a specimen in a fatigue test.
Stress Concentration
A condition in which a stress distribution has high localized stresses; usually induced by an abrupt change in the shape of the part (eg holes, corners, necks).
Stress Intensity Factor
A scale factor to define the magnitude of the crack-tip stress field.
Stress Raisers
Changes in contour or discontinuities in a structure that cause local increases in stress.
Stress Ratio
Ratio of minimum stress to maximum stress in one cycle of loading in a fatigue test.
Stress Relaxation
Rate of reduction of stress in a material due to creep.
Stress Resultant
A system of forces which is statically equivalent to a stress distribution over an area.
Stress Rupture Strength
Alternative name for Creep Rupture Strength.
Stressed Member
A component that is an integral part of the whole structure.
Stress-Rupture Test
A tension test performed at constant temperature, the load being held at such a level as to cause rupture.
Stress-Strain Diagram
Graph of stress as a function of strain.
Stress-Strain Ratio
Stress divided by strain at any load or deflection, below the elastic limit of a material it is equal to tangent modulus of elasticity.
Stribeck Curve
This relates friction between load-bearing surfaces as a function of relative oil film thickness and lubrication regime.
Stringer
Horizontal timber supporting other members of the frame in a wood or brick structure.
Stringer Inclusion
An impurity, metallic or non-metallic, which is trapped in the ingot and elongated subsequently in the direction of working.
Stroke
The distance a piston travels up or down inside the cylinder.
Structural Engineer
An engineer who investigates the behaviour and design of all kinds of structures.
Structural Model
An idealization for analysis purposes of a real or conceived structure.
Strut
Slender structural element that resists compressive forces acting lengthwise.
Stud
A fastener which is threaded at both ends with an unthreaded shank in between.
Stuffing Box
The annular chamber provided around a valve stem in a sealing system into which deformable packing is introduced.
Submersible Pump
A pump that operates only when totally submersed in the fluid which is being pumped.
Subsynchronous
Component of a vibration signal that has a frequency less than shaft rotation frequency.
Suction Filter
A pump intake-line filter in which the fluid is below atmospheric pressure.
Suction Valve
An automatic non-return valve, which opens when the boiler is at less than atmospheric pressure.
Super Glue
More formally known as Cyanoacrylate.
Super Heated Steam
Steam heated above its saturation temperature.
Support
A support contributes to keeping a structure in place by restraining one or more degrees of freedom.
Surface Filter Media
Porous materials which primarily retain contaminants on the influent face, performing the actual process of filtration.
Surface Filtration
Filtration which primarily retains contaminant on the influent surface.
Surface Finishing
A range of industrial processes that alter the surface of a manufactured item to achieve a certain property.
Surface Force
A force applied to the surface of an object.
Surface Gauge
A gauge used to check the accuracy, of plane surfaces, to scribe lines at desired distances from a given surface and to check the height of a point or points on a piece of work from a given surface.
Surface Roughness
At a microscopic scale, no surface appears perfectly smooth.
Surface Tension
Small droplets or bubbles of one fluid immersed in another fluid have a spherical shape because of the interfacial tension, or surface tension, between the two fluids.
Surge
A momentary rise of pressure in a circuit.
SUS
Abbreviation of Saybolt Universal Seconds which is another name for Saybolt Universal Viscosity.
SUV
Abbreviation of Saybolt Universal Viscosity.
Swamp Cooler
Evaporative type cooler in which air is drawn through porous mats soaked with water.
Swarf
The cuttings, and grinding fines that result from metal working operations.
SWG
A numbering system for standard wire diameters.
Swing Check Valve
A check valve in which the closure element is a hinged clapper which swings or rotates about a supporting shaft.
Synchronous Belt Drive
Also known as a Toothed Belt Drive.
Synchronous Rotation
The Moon about the same amount of time to rotate on its axis as it does to complete an orbit of the Earth, thus always presenting the same side to Earth.
Synchronous Speed
The speed at which the rotating field in an ac motor revolves.
System Efficiency
The overall efficiency of the system.
Systems Engineering
Lists all Systems Engineering topics in the Encyclopaedia
Tack Hammer
A special hammer with a magnetic head for inserting small nails or tacks.
Tack Weld
A weld made to hold parts in proper alignment until the final welds are made.
Tandem Mill
Arrangement of rolling mills, in direct line, allowing the metal to pass from one set of rolls to the next for the reduction of steel.
Tang
The flat on the shank of a cutting tool, such as a drill, reamer or end mill, that fits a slot in -the spindle of a machine to keep the tool from slipping.
Tap Wrench
A bar with a hole and clamping device or T-bar design to hold a tap used to make internal threads.
Taper Roller Bearing
A bearing composing of a cone of rollers and a matching cup for the rollers to sit within.
Tappet
A tappet is an arm, collar or cam within a machine which imparts intermittent motion.
TDC
Abbreviation of top dead centre.
Tear Resistance
The ability of a thin film, paper or textile to resist tearing.
Tee Joint
A joint between two members located approximately at right angles to each other in the form of a T.
Telescoping Gauge
A T-shaped gage used to measure the diameter or width of holes.
Telodynamic Transmission
The system of transmitting power over long distances by means of pulleys and wire ropes.
Temper Colours
The colours which appear on the surface of steel heated at low temperature in an oxidizing atmosphere.
Temperature Control
Temperature operated thermostatic device which automatically opens or closes a circuit.
Temperature Range
The minimum to maximum temperature over which a piece of equipment will operate.
Tenacity
The tensile stress expressed as force per unit linear density of an unstrained specimen.
Tenon
A projection made by cutting away the wood around it to insert into a mortise to make a joint.
Tensile Fracture
A fracture caused by tensional stress.
Tensile Strength
The ultimate strength of a material prior to fracture when subjected to an increasing tension load.
Tensile Stress
Stress acting on the cross-sectional area of a body normal to the tension force acting on the body.
Tension
A stretching force that pulls on a material.
Tension Set
Extent to which vulcanized rubber is permanently deformed after being stretched a specified amount for a short time.
Test Oil
Any oil subjected to evaluation in an established procedure.
Test Parameter
A specified component, property, or condition of a test procedure.
Thermal Growth
Movement of the machine parts associated with a change in machinery temperature between the static and operating conditions.
Thermit Crucible
The vessel in which the thermit reaction takes place.
Thermit Mixture
A mixture of metal oxide and finely divided aluminum with the addition of alloying metals as required.
Thermit Mould
A mould formed around the parts to be welded to receive the molten metal.
Thermit Welding
A group of welding processes in which fusion is produced by heating with superheated liquid metal and slag resulting from a chemical reaction between a metal oxide and aluminum, with or without the application of pressure.
Thermite Process
The method of obtaining liquid metal by reduction of the oxide with aluminium powder.
Thermodynamics
The study of energy transfers and transformations.
Thermostatic Control
Device which operates system or part of system based on temperature change.
Thermostatic Valve
Valve controlled by temperature change response elements.
Thin Film Lubrication
A condition of lubrication in which the film thickness of the lubricant is such that the friction between the surfaces is determined by the properties of the surfaces as well as by the viscosity of the lubricant.
Thin Rod
The moment of inertia of a thin rod.
Third Class Lever
The force is applied between the load and the fulcrum.
Thou
An abbreviation of thousandths of an inch. A unit of length used by engineers.
Thread Rolling
Chipless, cold-forming material-displacement process where a rolling head is pressed into the workpiece to create threads.
Three Body Abrasion
A particulate wear process by which particles are pressed between two sliding surfaces.
Three Phase Electricity
Multiple phase power supply or load that uses at least three wires where a different voltage phase from a common generator is carried between each pair of wires.
Throttle Pedal
A pedal that when pressed is connected to the engine and demands more torque.
Through Hole
Hole or cavity cut in a solid shape that connects with other holes or extends all the way through the workpiece.
Thrust
The force exerted in any direction by a fluid jet.
Thrust Bearing
A bearing designed to only take axial or thrust load.
Thrust Washer
A washer that is used to reduce the rotational friction of a shaft with under axial load.
TIG Welding
Abbreviation of Tungsten Inert Gas Welding.
Timber
A hard substance which forms the branches and trunks of trees and which can be used as a building material, for making things, or as a fuel.
Time for Rupture
Time required to rupture specimen under constant stress and temperature in a creep test.
Timken Roller Bearing
A type of taper roller bearing.
Tinners Hammer
A hammer used to shape tin plates.
Tinning
The process of applying a thin coat of solder to materials prior to their being soldered.
TIR
Abbreviation of Total Indicated Runout.
Toe-In
Setting the front wheels to toe in will mean that when driven the wheels will tend to be aligned.
Toe-Out
Setting the front wheels of a front wheel drive car to toe out will mean that when driven the wheels will tend to be aligned.
Tommy Bar
A rod which is inserted into the holes of a box spanner.
Ton Force
1 ton-force = 9964.02 N
tonf in-2
Abbreviation of Tons per Square Inch.
Tongue and Groove
A joinery method where a board has a protruding tongue on one edge and a groove on the other, the tongue of one board fits into the groove of the next.
Toolbox
A box design to protect and allow a set of tools to be carried around.
Tools
Lists all Tools topics in the Encyclopaedia
Torch Brazing
Bonding is produced by heating with a gas flame and by using a nonferrous filler metal having a melting point above 427°C.
Torque
The torque or turning moment acting on a body is defined as the product of the magnitude of the force and the perpendicular distance of the line of action of the force from the axis about which the body is being rotated.
Torque Steer
A tendency for a car to turn in a particular direction when power is applied.
Torque to Power
Calculate power in PS given a torque in Nm at a given speed.
Torsion
An action that twists a material.
Torsion Bar
A type of spring that twists as it is compressed or stretched.
Torsion Test
Method for determining behavior of materials subjected to twisting loads.
Torsional Deformation
Angular displacement of specimen caused by a specified torque in torsion test.
Torsional Modulus of Elasticity
Modulus of elasticity of material subjected to twist loading.
Torsional Strain
Strain corresponding to a specified torque in the torsion test.
Torsional Strength
Measure of the ability of a material to withstand a twisting load.
Torsional Stress
Shear stress developed in a material subjected to a specified torque in torsion test.
Transfer Pump
A pump employed to move a fluid from one location to another.
Transition Fit
A fit between a hole and a shaft where both clearance and interference may occur in the coupling.
Traverse
One movement across the surface of the work being machined.
Tribology
The technology of interacting surfaces in relative motion and concerned with the design, friction, lubrication, and wear of contacting surfaces that move relative to one another.
True Strain
The ratio of the change in dimension, resulting from a given load, to the magnitude of the dimension immediately prior to applying the load.
True Stress
The load applied to a material divided by the cross sectional area over which it acts.
Trunnion Bearing
A bearing used as a pivot to swivel or turn an assembly.
Truss
Structural framework of triangular units for supporting loads over long spans.
TSFC
Abbreviation of Thrust Specific Fuel Consumption.
Tsi
Abbreviation of Tons per Square Inch.
Tube Sheet
The portion of a heat exchanger or boiler in to which the tubes are rolled or secured.
Tubercle
A protective crust of corrosion products which builds up over a pit caused by the loss of metal due to corrosion.
Tuberculation
A corrosion process that produces hard knob-like mounds of corrosive products on metal surfaces, increasing friction and reducing flow in a water distribution system.
Tumbler Gears
A pair of small lever-mounted gears on a lathe used to engage or to change the direction of the lead screw.
Tumbling
Cleaning articles by rotating them in a cylinder with cleaning materials.
Tuned Mass Damper
Another name for a Dynamic Vibration Absorber.
Tungsten Carbide
Strong alloy often used in grinding and polishing.
Tungsten Inert Gas Welding
Filler rod is fed by hand, independent of the non-consumable tungsten electrode. Argon is used to shield the weld from oxygen in the air.
Turbine
A type of engine.
Turbulent Flow Sampler
A sampler that contains a flow path in which turbulence is induced in the main stream by abruptly changing the direction of the fluid.
Turn
One complete loop of a conductor about a core.
Turner Gauge
A device used to measure the actual scale-thickness in boiler tubes.
Turning
A workpiece is held in a chuck, mounted on a face plate or secured between centres and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face.
Tuyere
A nozzle or vent in the firepot of a forge. The air from the bellows or blower is forced through the tuyere.
Twin
Two portions of a crystal with a definite orientation relationship.
Two Position Valve
A valve which is either fully on or fully off with no positions between.
Two-Way Valve
Valve with one inlet port and one outlet port.
Tyre
The rubber part of the wheel which contacts the ground.
Tyre Bead
That portion of the tire that bears against the rim flange.
Tyre Gauge
An instrument for determining the pressure in a tube or tyre.
Ultimate Elongation
Alternate term for elongation of material at rupture under tensile loading.
Ultimate Load
The absolute maximum magnitude of load which a structure can sustain, limited only by ultimate failure.
Ultimate Strength
Maximum stress at point of rupture.
Ultrasonic Cleaning
An effective cleaning process for small items and fine detail where the item is immersed in a bath of cleaning fluid that is excited at ultrasonic frequenices.
Ultrasonic Machining
Material-removal operation in which an abrasive slurry flows between a tool, vibrating at a high frequency, and a workpiece.
Ultrasonic Testing
A method of non destructive testing of steel bars, plates or parts with high frequency sound waves produced with electronic equipment.
Unbalanced Seal
A mechanical seal arrangement wherein the full hydraulic pressure of the seal chamber acts to close the seal faces.
UNC
UNF tapping sizes, pitch and OD.
Under-Cooling
Cooling a material below the temperature of an equilibrium phase change fast enough to not allow the occurrence of the transformation.
Understeer
A handling condition in which the slip angle of the front tyres is greater than the slip angle of the rears.
UNF
UNF tapping sizes, pitch and OD.
Unit Cell
The smallest repetitive volume that comprises the complete pattern of a crystal.
Units
Lists all Units topics in the Encyclopaedia
Universal Joint
A mechanical device which transmits torque and/or rotary motion between two shafts that are not in a straight line.
Universal Milling Machine
A milling machine with a worktable that can be swiveled for milling helical work.
Used Oil
Any oil that has been in a piece of equipment, whether operated or not.
Vacancy
An unfilled lattice site in a crystal structure.
Vacuum Brazing
Components are heated in a high vacuum, completely free of oxygen.
Vacuum Dehydration
A method which involves drying or freeing of moisture through a vacuum process.
Vacuum Pump
Device used for creating vacuums.
Vacuum Separator
A separator that utilizes sub-atmospheric pressure to remove certain gases and liquids from another liquid because of their difference in vapour pressure.
Valence
The charge on an ion based on the number of electrons transferred or shared within a specific structure.
Valve
In electronics, a valve is a device consisting of two or more metal plates enclosed in an evacuated glass bulb.
Vane Compressor
Sliding-vane compressors use an eccentrically-mounted cylinder to drive centrally-mounted vanes inside a housing of decreasing radius, providing internal compression.
Vapour Lock
A condition where liquid flow is impeded by vapour trapped in a liquid line.
Variable Displacement Pump
A pump in which the displacement per cycle can be varied.
Variable Rate Spring
A spring that does not offer uniform resistance to compression.
Varnish
A resin in solution.
VAWT
Abbreviation of Vertical Axis Wind Turbine.
V Belt Drive
A belt used to transmit power between two shafts.
Vee Joint
Tongue and groove boards with their top corners beveled so when the two boards come together a V is formed.
Vehicle Noise
The noise produced by a land based vehicle that is radiated to the surrounding environment (exterior noise) or that is observed by the occupants of the vehicle (interior noise).
Velocity Head
The difference between dynamic pressure and static pressure.
Velocity Transducer
An electrical/mechanical transducer whose output is directly proportional to the velocity of the measured unit.
Vena Contracta
Point where the flow becomes parallel.
Veneer
A thin layer, sheet or facing.
Vent
An opening in a vessel or other enclosed space for the removal of gas or vapour.
Ventral
Pertaining to the belly, or the underside of a vehicle.
Venturi
A short constriction in a tube between two longer tapered portions that are usually of unequal length but terminate with the same diameter.
Vernier
An auxiliary scale, invented by Pierre Vernier, which enables the reading of the smallest divisions of a graduated scale.
Vernier Caliper
The vernier caliper provides the three basic functions of inner, outer and depth gauge.
Vertical Axis Wind Turbine
Two basic types are drag based and lift based.
Vibration Finishing
A surface finish achieved using a machine that vibrates a volume of abrasive material within which the item to be finished sits.
Vibratory Bowl Feeder
Hopper or conveyor mechanism utilizing a vibratory motion.
Vice
A device for holding material securely whilst being cut, filed or machined in some way.
View
A drawing of a side of an object.
Virgin Metal
Primary metal obtained directly from ores rather than recycled scrap.
Viscoelasticity
A type of deformation exhibiting the mechanical characteristics of viscous flow and elastic deformation.
Viscous
Possessing viscosity. Frequently used to imply high viscosity.
Viscous Damping
Viscous damping is the dissipation of energy that occurs when a particle in a vibrating system is resisted by a force proportional to the velocity of the particle.
Viscous Flow
The flow of fluid through a duct under conditions such that the mean free path is very small in comparison with the smallest dimension of a transverse section of the duct.
Viscous Fluid
A fluid whose molecular viscosity is sufficiently large to make the viscous forces a significant part of the total force field in the fluid.
Viscous Stresses
The components of the stress tensor when the pressure, i.e., the mean of the three normal stresses, has been subtracted out from each of the normal stresses.
Vitreous Enamel
An opaque or transparent glaze, generally coloured, which adheres to a suitable metallic surface when applied in a liquid state.
Volumetric Efficiency
Ratio of the volume discharged from a pump to the piston displacement of the pump.
Volute Casing
Spiral shaped casing surrounding the pump or fan impeller that converts velocity energy to pressure energy.
Vortex
Any flow possessing vorticity.
Wall Plug
A piece of plastic, wood or fibre that is inserted into a drilled hole in masonry to allow a woodscrew to be fitted.
Warm Working
Plastically deforming metal above room temperature but below the temperature at which the material undergoes recrystallization.
Warp
The yarns running lengthwise and parallel to the selvage in a woven fabric.
Washer
Used to distribute load under a nut or bolt locking surface.
Washout Plug
A small mudhole used for washing out the boiler.
Waste Gate
A valve used to limit the boost developed in a turbocharger.
Waste Water
The used water and solids from industrial processes that flow to a treatment plant.
Water Glycol Fluid
A fluid whose major constituents are water and one or more glycols.
Water Hardening
High carbon grades of tool steel, straight carbon steels and low alloy steels that are hardened by quenching in water during the heat treating operation.
Water Lubricant
Water used as a lubricant.
Water Tube
A boiler tube through which the fluid under pressure flows.
Water Tube Boiler
A boiler whose primary heating surface is composed of many small tubes, filled with water.
Water Wall
A furnace or other wall within a boiler enclosure that is composed of numerous closely set water tubes.
Waterline
The line of the water′s edge when the ship is afloat.
Waterwheel
A wheel with paddles designed to extract power from flowing water.
Waveband
A series of wavelengths forming a group.
Way
Longitudinal surface that guides the reciprocal movement of a machine part.
Wear
The loss of material from a surface, generally occurring between two surfaces in relative motion, and resulting from mechanical or chemical action or a combination of both.
Wear Debris
Particles that are detached from machine surfaces as a result of wear and corrosion.
Wear Inhibitor
An additive which protects the rubbing surfaces against wear, particularly from scuffing, if the hydrodynamic film is ruptured.
Wear Pattern
A pattern of wear visible at the point where two parts touch.
Weft
The yarns running perpendicular to the warp in a woven fabric.
Weight to Power Ratio
The weight of a machine divided by the output power of the machine.
Weld
Join two pieces of metal together by heating until fusion of material with or without filler metal.
Weld Bead
A weld deposit resulting from a pass.
Weld Gauge
A device designed for checking the shape and size of welds.
Weld Metal
That portion of a weld that has been melted during welding.
Weld Symbol
A picture used to indicate the desired type of weld.
Weldability
The capacity of a material to form a strong bond of adherence under pressure or when solidifying from a liquid.
Welder Certification
Certification in writing that a welder has produced welds meeting prescribed standards.
Welder Performance Qualification
The demonstration of a welders ability to produce welds meeting prescribed standards.
Welding
The process of joining two pieces of metal together by hammering, pressure or fusion.
Welding Pressure
The pressure exerted during the welding operation on the parts being welded.
Welding Rod
Filler metal in wire or rod form, used in gas welding and brazing processes and in those arc welding processes in which the electrode does not provide the filler metal.
Welding Tip
The tip of a gas torch especially adapted to welding.
Welding Torch
A device used in gas welding and torch brazing for mixing and controlling the flow of gases.
Welding Transformer
A device for providing current of the desired voltage.
Weldment
An assembly whose component parts are formed by welding.
Wet Strength
Breaking strength of paper saturated with water.
Wheel
The Mesopotamians are credited with the invention of the wheel.
Wheel Dresser
A tool or device for dressing or truing a grinding wheel.
Wheelbase
The distance between the centres of the front and rear wheel axles as viewed from the side of the car.
Whirl
Whirling is defined as the rotation of the plane made by the bent shaft and the line of centres of the bearing.
Whittle, Frank
Inventor of the turbojet and turbofans.
Wicking
The vertical absorption of a liquid into a porous material by capillary forces.
Wide Open Throttle
The throttle of an internal combustion engine is fully open and so demanding maximum power at any given engine speed.
Winch
A machine, the essential part of which consists of a drum driven by hand or powered through gearing, and used to receive a rope which is wound upon it.
Wind Power
Windmills are used in a number of different applications for generating electrical power to pumping water.
Wind Tunnel
A tunnel with a large fan that is used by engineers to test the effects of high winds on a structure.
Windlass
A wheel and axle that allows a load on a cord to be wound up on the axle with a small force applied to the rim of the wheel.
Wire
A metal strand, normally pliable.
Wire Brush
A brush with metal bristles used to remove loose material from metal surfaces.
Witness Mark
A punch mark or scratch used to position or locate some part in its proper spot.
Wobble
An angular error between the actual axis of rotation and the theoretical axis of rotation.
Wood
A hard substance which forms the branches and trunks of trees and which can be used as a building material, for making things, or as a fuel.
Wooden Mallet
A hammer with a wooden head.
Work Hardening
Increase dislocation density in metals through straining a material with an applied stress.
Working Drawing
A drawing. blueprint, or sketch of a part, structure, or machine.
Working Pressure
The pressure at which a system is designed to operate.
Working Stress
The allowable stress considered to be safe in the design of part. It is the ultimate stress of the material divided by a safety factor.
Worm
The threaded cylinder or shaft designed to mesh with a worm gear.
Worm Gear
A gear with helical teeth made to conform with the thread of the mating worm.
WOT
Abbreviation of Wide Open Throttle.
Wrench
A tool used to turn a nut and bolt.
Wrist Pin
Also known as a piston pin, a pin that rests in two bored holes in the piston and passes through the eye of the connecting rod, to join the two together flexibly.
Wrought Alloy
An alloy that is suitable for mechanical forming below melting-point temperatures.
Wrought Iron
The purest commercial form of iron, nearly free of carbon.
Yaw Error
Positioning error resulting from a yaw motion.
Yield Point Elongation
In materials that exhibit a yield point this is the difference between the elongation of the specimen at the start and at the finish of discontinuous yielding.
Yield Strain
A material deformed beyond its yield strain, no longer exhibits linear elastic behaviour.
Yield Strength
Indication of maximum stress that can be developed in a material without causing plastic deformation.
Yield Strength Elongation
Strain corresponding to yield strength of material.
Zinc Plating
The application of a zinc coating by galvanizing or electrogalvanizing.
Zinc Vapour Deposition
A process in which zinc vapour is deposited in a vacuum.

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