Acme Thread

A screw thread having a 29 degree included angle. Used largely for feed and adjusting screws on machine tools.

Acme Thread

The Acme thread is easier to machine and is stronger than the square thread. Acme threads are thicker and wider and operate better in environments with dirt and debris.

Acme Thread
Number of threads per inchDepth of thread [inches]Width at top of thread [inches]Width at bottom of thread [inches]Space at top of thread [inches]Thickness at root of thread [inches]

Note: all dimensions in the above table are in inches.

The Acme Thread has clearance at top and bottom and so in order to avoid confusion the following image and table shows dimensions for the Tap, Nut, Screw, Die Tap and Die.

Acme thread parts

Acme Thread Parts
Dimension RequiredClass of ThreadSymbolFormula
Outside DiameterTapANominal size + 0.020 inch
NutBNominal size + 0.020 inch
Screw and Die TapCNominal size
DieDNominal size
Root DiameterTapENominal size - (1 / TPI) + 0.020
NutFNominal size - (1 / TPI)
Screw and Die TapGNominal size - (1 / TPI) + 0.020
DieHNominal size - (1 / TPI) + 0.020
Width of Flat on Top of ThreadTapJ(0.3707 / TPI) - 0.0052
NutK(0.3707 / TPI)
Screw and Die TapL(0.3707 / TPI)
DieM(0.3707 / TPI) - 0.0052
Width of Flat at Bottom of ThreadTapN(0.3707 / TPI) - 0.0052
NutP(0.3707 / TPI) - 0.0052
Screw and Die TapR(0.3707 / TPI) - 0.0052
DieS(0.3707 / TPI)

Note: Nominal Size is outside diameter of the thread. TPI is Threads per Inch.


Screw Threads - Machinery′s Data Sheets, 1910, The Industrial Press

See also: British Association Threads, British Standard Whitworth, Lead Screw, Thread.

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Subjects: Fixings and Fasteners