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 Hardness: Resistance to abrasive wear.
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 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.
Absolute Pressure: Pressure measured from a starting point of 0 in perfect vacuum.
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.
AC Induction Motors: These are generally used for constant speed applications where a fixed frequency power source such as 60 Hz or 400 Hz is available.
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.
Acid Embrittlement: A form of hydrogen embrittlement that may be induced in some metals by an acid.
Ackermann Angle: The toe-out or toe-in of a vehicle with Ackermann steering when the wheels are positioned straight ahead.
Ackermann Steering: A double-pivoting steering system.
Acme Thread: A screw thread having a 29 degree included angle. Used largely for feed and adjusting screws on machine tools.
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 Pack: Name given to all of the soft absorptive parts used to reduce noise in a vehicle.
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
Afterburner: Thrust augmentation feature of a gas turbine engine.
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 Brake: Used to reduce the speed of an aeroplane.
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 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.
Aircraft: Any structure, machine, or contrivance, especially a vehicle, designed to be supported by the 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.
Airframe: The structure of an aircraft, without power plant and systems.
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.
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.
Alpha Rockwell Hardness: Index of the resistance of a plastic to surface penetration by a specified indenter under specified load applied with a Rockwell hardness tester.
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 Standard Pipe Thread: A type of screw or thread, commonly used on pipe fittings to assure a tight seal.
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.
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.
API Gravity: An arbitrary scale adopted by the American Petroleum Institute to designate the specific gravity of mineral oils.
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 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: Fo 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.
Autogyro: An aeroplane that flies by virtue of the lift generated by freewheeling rotating wings set windmill fashion above the fuselage.
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.
BA Threads: Clearance and tapping drill sizes for BA threads.
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.
Ballistics: Ignoring the curvature of the Earth, frictional losses and that g is constant it is possible to calculate the trajectory of a projectile that is fired with a given initial velocity and elevation.
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.
Barrel: A unit of capacity in the oil industry.
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 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.
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.
Brinell Hardness Test: A test for determining the hardness of a material by forcing a hard steel or carbide ball of specified diameter into it under a specified load.
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 Association Threads: A British system of threads with 47.5� included angle with rounded roots and crest. Even numbers are the preferred sizes.
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.
Brittle Crack Propagation: A very sudden propagation of a crack with the absorption of no energy except that stored elastically in the body.
Brittle Fracture: Separation of a solid with little or no macroscopic plastic deformation.
Brittleness: The tendency of a material to fracture without first undergoing significant plastic deformation.
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.
Brush DC Motors: The Brush DC motors use commutators and carbon brushes to apply current through the windings as the motor rotates.
Brushless DC Motors: The BLDC motor uses electronic commutation to control the current through the windings.
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.
Burgess 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 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.
Cam: A device for converting regular rotary motion to irregular rotary or reciprocating motion.
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.
Capacitor Start Motor: A type of single-phase, ac induction motor in which a starting winding and a capacitor are placed in series to start the motor.
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.
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: An alloy of iron and carbon (2.5%). Distinguished from steel by large amounts of graphite.
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.
C_D: 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.'
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.
Cetane Number: A percentage indicating the ignition quality of diesel fuels.
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.
Chasing Threads: The process of cutting threads in a lathe or screw machine.
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.
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.
C_L: 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.
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 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 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.
Combination Square: A drafting and layout tool combining a square, level, protractor, and centre head.
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).
Compound Wound Motors and Generators: Machines that have a series field in addition to a shunt field.
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.
Cone Pulley: A one-piece stepped pulley having two or more diameters.
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.
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.
Corrosion: Deteriorative loss of a metal as a result of dissolution environmental reactions.
Corrosion Inhibitor: A lubricant additive for protecting surfaces against chemical attack from contaminants in the lubricant.
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.
C_P: 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.
Crack: A fracture type discontinuity characterized by a sharp tip and high ratio of length and width to opening displacement.
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 Cooling Rate: The minimum rate of continuous cooling just sufficient to prevent undesired transformations.
Critical Damping: The smallest value of damping required for a displaced system to return to its equilibrium position without overshooting or oscillating about that position.
Critical Point: The temperature or pressure at which a change in crystal structure, phase or physical properties occurs.
Critical Resolved Shear Stress: The shear stress, resolved within a slip plane and direction, which is required to initiate slip.
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.
Cycle Counting: Cycle counting is used to summarize lengthy, irregular load-versus-time histories by providing the number of times cycles of various amplitudes occur.
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.
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.
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.
Dendrite: A crystal that has a tree-like branching pattern.
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.
Dial Indicator Gauge: Used to measure shaft runout or deviation from a nominal position.
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
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.
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.
Ealstic Strain: Dimensional changes accompanying stress where the original dimensions are restored upon release of the stress.
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.
Elasticity: A material is elastic if it returns to it's original shape after being deformed.
Electric Motor Efficiency: The efficiency of a motor is the ratio of electrical power input to mechanical power output.
Electric Motor Load: Any device driven by a motor.
Electric Motor Noise: There are numerous applications of electric motors and the type of noise produced by each may be very specific to the installation and type of motor.
Electric Motor Reaction: The force created by generator armature current that tends to oppose the normal rotation of the armature.
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.
Electrical Engineer: An engineer concerned with electrical devices and systems and with the use of electrical energy.
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.
Embrittlement: Reduction in ductility due to physical or chemical changes.
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.
Endurance Limit: In fatigue testing, the number of cycles which may be withstood without failure at a particular level of stress.
Energy Density: Characteristic parameter of a battery/electrical power source indicating the amount of electrical energy stored per unit weight or volume.
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 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.
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.
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 Noise: The exhaust system of an internal combustion engine has a number of functions, one of which is to reduce the noise of the waste gases as they are expelled from the engine to the atmosphere.
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.
Extensometer: A test apparatus for indicating the deformation of metal while it is subjected to stress.
External Force: A surface force or body force acting on an object.
External Thread: A screw thread which is formed on an external cylinder,e.g. bolts, screws, studs.
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.
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.
Failure: The event, or inoperable state, in which any item or part of an item does not, or would not, perform as previously specified.
Failure Mode and Effects Analysis: A procedure by which each potential failure mode of a system is analyzed to determine the effects on the system and classify each potential failure mode according to its severity.
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.
Fatigue: An important mode of failure of engineering components subjected to dynamic stresses.
Fatigue Chunks: Thick three-dimensional particles exceeding 50 microns indicating severe wear.
Fatigue Life: Number of cycles of fluctuating stress and strain of a specified nature that a material will sustain before failure occurs.
Fatigue Limit: In fatigue testing, the number of cycles which may be withstood without failure at a particular level of stress.
Fatigue Notch Factor: Ratio of fatigue strength of a specimen with no stress concentration to fatigue strength of a specimen with a notch or other stress raisers.
Fatigue Ratio: Ratio of fatigue strength or fatigue limit to tensile strength.
Fatigue Resistance: The ability of a material to withstand repeated and varying loads.
Fatigue Strength: Magnitude of fluctuating stress required to cause failure in a fatigue test specimen after a specified number of cycles of loading.
Fatigue Strength Reduction Factor: An alternate term for fatigue notch factor.
Fatigue Test: A method for determining the behaviour of materials under fluctuating loads.
Faying Surface: That surface of a member that is in contact with another member to which it is joined.
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.
Female Thread: An internal screw thread designed to mate with a component having male threads of the same size and type.
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.
File Hardness: Hardness as determined by the use of a file.
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 Machining: Machining a surface to give it the desired finish.
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.
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 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 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.
FMEA: A procedure by which each potential failure mode of a system is analyzed to determine the effects on the system and classify each potential failure mode according to its severity.
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 Stress: True stress generated in a material at fracture.
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.
Fretting Corrosion: Can take place when two metals are held in contact and subjected to repeated small sliding, relative motions.
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 Gouges: A series of relatively short surface scratches variable in form and severity.
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.
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.
Generator: A machine that converts mechanical energy to electrical energy by applying the principle of magnetic induction.
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.
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.
Hardness: Resistance of metal to plastic deformation usually by indentation.
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 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.
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.
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.
Induction Motor: The rotor is energized by transformer action from the stator.
Inert Gas: A gas which does not normally combine chemically with other elements.
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.
Insulator: A material that does not allow the passage of electric charge or is a poor conductor of thermal energy.
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.
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.
Internal Thread: A screw thread which is formed in a hole, such as the thread in a nut.
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.
Intumescent Mat: Ceramic fibre mat which irreversibly expands after exposed to high temperature.
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.
ISO Metric Threads: Table of ISO Metric Thread standards.
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.
Isothermal Annealing: Austenitizing a ferrous alloy and then cooling to and holding at a temperature at which austenite transforms to a relatively soft ferrite carbide aggregate.
Isothermal Transformation: A change in phase at any constant temperature.
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.
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.
Knoop Hardness Test: An indentation hardness test.
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.
Left Hand Thread: A screw thread that is screwed in by rotating counterclockwise.
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 Motion: Motion in a straight line.
Linear Motor: A motor consisting of two parts, typically a moving coil and stationary magnet track.
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.
Lock: A mechanical device that is used on a door or container to restrict access.
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 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 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 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.
Mean Time Between Failure: The average time between failures for a continuously operating system.
Mean Time to Failure: The measured operating time of a system or component divided by the number of failures that occurred during that time.
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.
Mechatronics: The introduction of electronic controls into mechanical components.
Membrane: A thin sheet or layer.
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.
Metric Threads: Tapping and clearance drill sizes for coarse and fine metric thread sizes.
Microhardness: The hardness of microscopic areas or of the individual microconstituents in a metal.
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.
Milling Cuffer: A cutting tool, generally cylindrical in shape and used on a milling machine and operated essentially like a circular saw.
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
Model Engineers Thread: A thread based upon the Whitworth thread form that was established in 1912.
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, ...
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 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.
Orifice: Accurate size opening for controlling fluid flow.
Original Equipment Manufacturer: Products supplied by the company which first created the product.
Outside Caliper: An instrument used to measure the outer dimension of an object.
Outside Diameter: A dimension commonly used to specify the size of a cylindrical bar or pipe.
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.
Peck: An old unit of volume.
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.
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.
Pulley: A disc with a groove around its circumference to locate a rope or cable and is used to change the direction of a force and/or multiply the force.
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.
Radiated Noise: The dissemination of sound energy as acoustic waves from a source (e.g. a vibrating panel, running engine etc.).
Radius Gauge: Any one of a number of small flat, standard-shaped metal leafs or blades used for checking the accuracy of regular concave and convex surfaces.
Rainflow Analysis: A method of representing a random signal by various numbers of sinusoids that would produce the same amount of fatigue damage.
Ramjet: A jet engine with no mechanical compressor, consisting of specially shaped tubes or ducts open at both ends.
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.
Refrigerant: The working fluid used in refrigerators.
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.
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.
Right Hand Thread: A screw thread that is screwed in by rotating clockwise. Most threads are right handed.
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.
Rocking Grate: An advanced form of firebar.
Rockwell Hardness: Hardness determined from size of indentation using a diamond or steel ball and given load.
Rolled Thread: A thread formed by plastically deforming a blank rather than by cutting.
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.
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.
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.
Sandblasting: A process of blowing sand by compressed air with considerable force through a hose against an object.
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.
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.
Self Extinguishing: A material which will not support combustion when external source of flame is removed.
Self-Aligning Bearing: A roller-element bearing with one spherical raceway that automatically provides compensation for shaft or housing deflection or misalignment.
Series Wound Motor and Generator: Electric motor in which the armature and field windings are connected in series with each other.
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.
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.
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.
Shrinking Hammer: A special hammer with faces shaped to allow for correction of locally stretched sheet metal.
Shunt Wound Motor and Generator: Machines in which the armature and field windings are connected in parallel with each other.
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.
Side Cutters: A tool like a pair of pliers except the end opposite the handles have sharp edges used to cut wire.
Siemens and Halske Thread: German electrical engineering company that later became part of Siemens AG. Siemens & Halske Thread was used in telephones around 1900 AD.
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 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.
Spall: Small chips or fragments which are sometimes given off by electrodes during the welding operation.
Speculum: A copper-tin alloy with 33 to 45% of tin that has very high optical reflectivity when polished.
Spindle: Another name for an axle.
Spindle Speed: The rotational speed at which a machine is set.
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.
Split Pin: A metal pin with two arms which is passed through a hole and held in place by the springing apart of the arms.
Spring Dividers: Dividers whose legs are held together at the hinged end by the pressure of a C-shaped 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.
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.
Straightedge: As it sounds, an unmarked tool used to draw straight lines.
Strain Gauge: A sensor that experiences a change in resistance when it is stretched or strained.
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 Amplitude: One-half the range of fluctuating stress developed in a specimen in a fatigue test.
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.
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 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.
Symmetrical Thread: Both flanks of the thread profile are inclined at the same angle.
Synchronous Belt Drive: Also known as a Toothed Belt Drive.
Synchronous Motor: An AC motor whose rotor is activated by DC.
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.
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 Cycling: Subjecting a product to pre-determined temperature changes, between hot and cold extremes.
Thermal Resistance: The property of a material, device or system that impedes the flow of heat.
Thermal Shock: Stresses induced in a material because of a rapid temperature change or a thermal gradient.
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: A helical projection of uniform section on the internal or external surface of cylinder or cone.
Thread Angle: The angle formed by the two sides of the thread with each other.
Thread Axis: A line running lengthwise through the centre of the screw.
Thread Crest: The top surface joining the two sides of a thread.
Thread Depth: The distance between the crest and the root of a thread.
Thread Flank: The thread flanks join the thread roots to the crest.
Thread Height: This is the radial distance between the minor and major diameters of the thread.
Thread Length: The length of the portion of the fastener with threads.
Thread Micrometer: A micrometer in which the spindle is ground to a point having a conical angle of 60 degrees.
Thread Pitch: The distance from a point on one screw thread to a corresponding point on the next thread.
Thread Pitch Diameter: The diameter of a screw thread measured from the thread pitch line on one side to the thread pitch line on the opposite side.
Thread Root: The bottom surface joining the sides of two adjacent threads.
Thread Runout: The portion at the end of a threaded shank which is not cut or rolled to full depth, but which provides a transition between full depth threads and the fastener shank or head.
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.
Thrust: The force exerted in any direction by a fluid jet.
Thrust Bearing: A bearing designed to only take axial or thrust 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 req

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