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ANSI/ASME B1.5 - ACME Screw Threads

Acme trapezoidal threads.

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ACME trapezoidal thread screw

Acme thread dimensions:

Outside Diameter Screw
TPIInside Diameter Nut
Crest Nut
Outside Clearance
Inside Clearance
Fit Allowance
1/4 16 0.187 0.023 0.005 0.005 0.0010
5/16 14 0.241 0.026 0.005 0.005 0.0010
3/8 10 0.275 0.037 0.010 0.010 0.0013
7/16 10 0.337 0.037 0.010 0.010 0.0013
1/2 10 0.400 0.037 0.010 0.010 0.0015
5/8 8 0.500 0.046 0.010 0.010 0.0016
3/4 6 0.583 0.062 0.010 0.010 0.0018
7/8 6 0.708 0.062 0.010 0.010 0.0019
1 6 0.833 0.062 0.010 0.010 0.0021

The ANSI/ASME B1.5 ACME Screw Threads Standard provides

  • General Purpose ACME, and
  • Centralizing ACME

Centralizing Acme threads have limited clearance at the major diameters of both the internal and external threads and are used extensively for feed screws. Restricted clearance enables a bearing at the major diameter of the thread to preserve alignment of the thread axis preventing wedging on the flanks and part sagging.

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