Dimension table
| Designation | TPI | Pitch p (in) | Nom. d (in) | d₂ pitch (in) | d₁ basic (in) |
|---|---|---|---|---|---|
| 1/4-16 ACME | 16 | 0.06250 | 0.2500 | 0.2188 | 0.1875 |
| 5/16-14 ACME | 14 | 0.07143 | 0.3125 | 0.2768 | 0.2411 |
| 3/8-12 ACME | 12 | 0.08333 | 0.3750 | 0.3333 | 0.2917 |
| 7/16-12 ACME | 12 | 0.08333 | 0.4375 | 0.3958 | 0.3542 |
| 1/2-10 ACME | 10 | 0.10000 | 0.5000 | 0.4500 | 0.4000 |
| 5/8-8 ACME | 8 | 0.12500 | 0.6250 | 0.5625 | 0.5000 |
| 3/4-6 ACME | 6 | 0.16667 | 0.7500 | 0.6667 | 0.5833 |
| 7/8-6 ACME | 6 | 0.16667 | 0.8750 | 0.7917 | 0.7083 |
| 1-5 ACME | 5 | 0.20000 | 1.0000 | 0.9000 | 0.8000 |
| 1-1/4-5 ACME | 5 | 0.20000 | 1.2500 | 1.1500 | 1.0500 |
| 1-1/2-4 ACME | 4 | 0.25000 | 1.5000 | 1.3750 | 1.2500 |
| 1-3/4-4 ACME | 4 | 0.25000 | 1.7500 | 1.6250 | 1.5000 |
| 2-4 ACME | 4 | 0.25000 | 2.0000 | 1.8750 | 1.7500 |
| 2-1/2-3 ACME | 3 | 0.33333 | 2.5000 | 2.3333 | 2.1667 |
| 3-2 ACME | 2 | 0.50000 | 3.0000 | 2.7500 | 2.5000 |
| 3-1/2-2 ACME | 2 | 0.50000 | 3.5000 | 3.2500 | 3.0000 |
| 4-2 ACME | 2 | 0.50000 | 4.0000 | 3.7500 | 3.5000 |
| 5-2 ACME | 2 | 0.50000 | 5.0000 | 4.7500 | 4.5000 |
Source: ASME B1.5-1997 (General ACME). Basic formulas: d₂ = d − p/2 · d₁ = d − p (basic diameters; class 2G tolerances not included). The 29° angle differs from ISO trapezoidal thread (Tr) at 30°.
Key technical characteristics
- Included angle
- 29° (14.5° per flank)
- Profile
- Trapezoidal (flat crest)
- Standard
- ASME B1.5 (General ACME)
- Primary function
- Power and motion transmission
- Precision variant
- Stub ACME — coarser pitch and lower profile
- Designation
- Diameter-TPI ACME (e.g. 1-5 ACME)
Typical applications
- Lead screws in manual and semi-automatic lathes.
- Power screws in presses, bench vises, mechanical jacks.
- Linear actuators for slow movement with high force output.
- Manual lathe chuck and clamping mechanisms.
Compatibility and interoperability
- ✗NOT interchangeable with ISO trapezoidal thread (Tr) — 29° ACME vs 30° ISO. Profiles do not mesh correctly.
- ✗NOT for structural fastening — trapezoidal profile has lower tensile strength than V-thread (60°) for the same diameter.
- ✓ACME and Stub ACME are compatible within the same system — Stub has shorter flanks for space-constrained applications.
Selection guide
- 01For high-efficiency lead screws (CNC, ballscrew equivalent) consider ball screws — ACME has higher friction.
- 02ACME is preferred over ballscrew when self-locking capability under axial load is needed.
- 03Always specify lead screw and nut material — bronze or plastic (Nylon, Delrin) nut reduces wear.
- 04For new CNC machine design, prefer ball screws or ISO trapezoidal (Tr) for better availability in Mexico.