Metric Threads
The most commonly used type of general-purpose screw thread, one of the first international standards agreed when the International Organization for Standardization was set up in 1947.
| Size [mm] | Pitch [mm] | Tap drill [mm] | Clearance drill [mm] |
| 1.0 | 0.25 | 0.75 | |
| 1.1 | 0.25 | 0.85 | |
| 1.2 | 0.25 | 0.95 | |
| 1.4 | 0.3 | 1.1 | |
| 1.6 | 0.35 | 1.25 | 1.8 |
| 1.7 | 0.35 | 1.3 | |
| 1.8 | 0.35 | 1.45 | |
| 2 | 0.4 | 1.6 | 2.4 |
| 2.2 | 0.45 | 1.75 | |
| 2.5 | 0.45 | 2.05 | 2.90 |
| 3.0 | 0.5 | 2.5 | 3.40 |
| 3.5 | 0.6 | 2.9 | 3.90 |
| 4.0 | 0.7 | 3.3 | 4.50 |
| 4.5 | 0.75 | 3.7 | |
| 5 | 0.8 | 4.2 | 5.50 |
| 6 | 1 | 5 | 6.60 |
| 7 | 1 | 6 | |
| 8 | 1.25 | 6.8 | 9.0 |
| 9 | 1.25 | 7.8 | |
| 10 | 1.5 | 8.5 | 12.0 |
| 11 | 1.5 | 9.5 | |
| 12 | 1.75 | 10.2 | 14.0 |
| 14 | 2 | 12 | 16.0 |
| 16 | 2 | 14 | 18.0 |
| 18 | 2.5 | 15.5 | |
| 20 | 2.5 | 17.5 | 22.0 |
| 22 | 2.5 | 19.5 | 25.0 |
| 24 | 3 | 21 | 27.0 |
| 27 | 3 | 24 | 30.0 |
| 30 | 3.5 | 26.5 | 33.0 |
| 33 | 3.5 | 29.5 | |
| 36 | 4 | 32 | 40.0 |
| 39 | 4 | 35 |
| Size [mm] | Pitch [mm] | Tap drill [mm] | Clearance drill [mm] |
| 4 | .35 | 3.6 | |
| 4 | .5 | 3.5 | |
| 5 | .5 | 4.5 | |
| 6 | .5 | 5.5 | |
| 6 | .75 | 5.25 | |
| 7 | .75 | 6.25 | |
| 8 | .5 | 7 | 9 |
| 8 | .75 | 7.25 | 9 |
| 8 | 1 | 7.5 | 9 |
| 9 | 1 | 8 | |
| 10 | .75 | 9.25 | 11 |
| 10 | 1 | 9 | 11 |
| 10 | 1.25 | 8.8 | 11 |
| 11 | 1 | 10 | |
| 12 | .75 | 11.25 | 14 |
| 12 | 1 | 11 | 14 |
| 12 | 1.5 | 10.5 | 14 |
| 14 | 1 | 13 | 16 |
| 14 | 1.25 | 12.8 | 16 |
| 14 | 1.5 | 12.5 | 16 |
| 16 | 1 | 15 | 18 |
| 16 | 1.5 | 14.5 | 18 |
| 18 | 1 | 17 | 20 |
| 18 | 2 | 16 | 20 |
| 20 | 1 | 19 | 22 |
| 20 | 1.5 | 18.5 | 22 |
| 20 | 2 | 18 | 22 |
| 22 | 1 | 21 | 24 |
| 22 | 1.5 | 20.5 | 24 |
| 22 | 2 | 20 | 24 |
| 24 | 1.5 | 22.5 | 26 |
| 24 | 2 | 22 | 26 |
| 26 | 1.5 | 24.5 | |
| 27 | 1.5 | 25.5 | 30 |
| 27 | 2 | 25 | 30 |
| 28 | 1.5 | 26.5 | |
| 30 | 1.5 | 28.5 | 33 |
| 30 | 2 | 28 | 33 |
| 33 | 2 | 31 | 36 |
| 36 | 3 | 33 | 39 |
| 39 | 3 | 36 | 42 |
Reference
BS 919-3:2007 Screw gauge limits and tolerances. Specification for gauges for screw threads of ISO metric form
ISO 68-1: ISO general purpose screw threads - Basic profile - Metric screw threads.
ISO 261, titled ISO general purpose metric screw threads-General plan, is an international standard that defines a detailed list of preferred combinations of outer diameter D and pitch P for ISO metric screw threads.
ISO 262, titled ISO general purpose metric screw threads-Selected sizes for screws, bolts and nuts, defines a shorter list of thread dimensions - a subset of the combinations listed in ISO 261
See also: British Association Threads, British Standard Whitworth, Thread.
Subjects: Mechanical Engineering