ACME and Stub ACME threads: size chart
Full chart with the tap drill for every size. Press “Calculate” on any row to open the calculator with that thread.
ACME is the American 29° trapezoidal thread for transmitting motion: lead screws, presses, jacks and valves. Stub ACME (ASME B1.8) is the version with a shortened thread, 0.3·P high instead of 0.5·P, for thin walls or where a full thread does not fit. In Europe its equivalent is the 30° metric trapezoidal thread (Tr).
| Thread | Threads per inch | Pitch (mm) | Ø major | Basic pitch Ø | Nut minor Ø (basic) | Calculate |
|---|---|---|---|---|---|---|
| ACME 1/4"-16 | 16 | 1.587 | 0.25" · 6.35 mm | 0.2188" · 5.556 mm | 0.1875" · 4.762 mm | |
| ACME 5/16"-14 | 14 | 1.814 | 0.3125" · 7.938 mm | 0.2768" · 7.031 mm | 0.2411" · 6.124 mm | |
| ACME 3/8"-12 | 12 | 2.117 | 0.375" · 9.525 mm | 0.3333" · 8.467 mm | 0.2917" · 7.408 mm | |
| ACME 1/2"-10 | 10 | 2.54 | 0.5" · 12.7 mm | 0.45" · 11.43 mm | 0.4" · 10.16 mm | |
| ACME 5/8"-8 | 8 | 3.175 | 0.625" · 15.875 mm | 0.5625" · 14.287 mm | 0.5" · 12.7 mm | |
| ACME 3/4"-6 | 6 | 4.233 | 0.75" · 19.05 mm | 0.6667" · 16.933 mm | 0.5833" · 14.817 mm | |
| ACME 7/8"-6 | 6 | 4.233 | 0.875" · 22.225 mm | 0.7917" · 20.108 mm | 0.7083" · 17.992 mm | |
| ACME 1"-5 | 5 | 5.08 | 1" · 25.4 mm | 0.9" · 22.86 mm | 0.8" · 20.32 mm | |
| ACME 1-1/4"-5 | 5 | 5.08 | 1.25" · 31.75 mm | 1.15" · 29.21 mm | 1.05" · 26.67 mm | |
| ACME 1-1/2"-4 | 4 | 6.35 | 1.5" · 38.1 mm | 1.375" · 34.925 mm | 1.25" · 31.75 mm | |
| ACME 2"-4 | 4 | 6.35 | 2" · 50.8 mm | 1.875" · 47.625 mm | 1.75" · 44.45 mm |
| Thread | Threads per inch | Pitch (mm) | Ø major | Basic pitch Ø | Nut minor Ø (basic) | Calculate |
|---|---|---|---|---|---|---|
| Stub ACME 1/4"-16 | 16 | 1.587 | 0.25" · 6.35 mm | 0.2312" · 5.874 mm | 0.2125" · 5.397 mm | |
| Stub ACME 5/16"-14 | 14 | 1.814 | 0.3125" · 7.938 mm | 0.2911" · 7.394 mm | 0.2697" · 6.849 mm | |
| Stub ACME 3/8"-12 | 12 | 2.117 | 0.375" · 9.525 mm | 0.35" · 8.89 mm | 0.325" · 8.255 mm | |
| Stub ACME 1/2"-10 | 10 | 2.54 | 0.5" · 12.7 mm | 0.47" · 11.938 mm | 0.44" · 11.176 mm | |
| Stub ACME 5/8"-8 | 8 | 3.175 | 0.625" · 15.875 mm | 0.5875" · 14.922 mm | 0.55" · 13.97 mm | |
| Stub ACME 3/4"-6 | 6 | 4.233 | 0.75" · 19.05 mm | 0.7" · 17.78 mm | 0.65" · 16.51 mm | |
| Stub ACME 7/8"-6 | 6 | 4.233 | 0.875" · 22.225 mm | 0.825" · 20.955 mm | 0.775" · 19.685 mm | |
| Stub ACME 1"-5 | 5 | 5.08 | 1" · 25.4 mm | 0.94" · 23.876 mm | 0.88" · 22.352 mm | |
| Stub ACME 1-1/4"-5 | 5 | 5.08 | 1.25" · 31.75 mm | 1.19" · 30.226 mm | 1.13" · 28.702 mm | |
| Stub ACME 1-1/2"-4 | 4 | 6.35 | 1.5" · 38.1 mm | 1.425" · 36.195 mm | 1.35" · 34.29 mm | |
| Stub ACME 2"-4 | 4 | 6.35 | 2" · 50.8 mm | 1.925" · 48.895 mm | 1.85" · 46.99 mm |
How to read the chart
Basic pitch Ø: D − 0.5·P on general-purpose ACME and D − 0.3·P on Stub ACME. It is the reference for measuring the flank over wires.
Nut minor Ø (basic): D − P on general-purpose ACME and D − 0.6·P on Stub ACME. The real nut also carries the allowance of its class, so the hole is machined slightly larger.
Internal ACME threads are usually turned or milled; if they are tapped, the drill is given by the ACME tap data sheet. "Calculate" opens the calculator with that size.
Related tools
Cutting parameters calculator
Cutting speed (Vc), rpm, feed and theoretical surface finish for turning, milling, drilling and threading by material and tool. A starting point.
GSM Code List
List of G and M Codes for CNC Programming. Search and filter ISO commands by control, machine or function.
CNC G-code Simulator
CNC IDE: editing with G/M tooltips, line inspector, conversion between controls and 2D/3D toolpath.