ANSI/ASME B1.5 - ACME Screw Threads
Acme trapezoidal threads.
Acme thread dimensions:
| Outside Diameter Screw (in) | TPI | Inside Diameter Nut (in) | Crest Nut (in) | Outside Clearance (in) | Inside Clearance (in) | Fit Allowance (in) |
|---|---|---|---|---|---|---|
| 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 | 12 | 0.275 | 0.037 | 0.010 | 0.010 | 0.0013 |
| 7/16 | 12 | 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.
