The tap drill size is nominal diameter minus pitch (e.g. M6 x 1.0 needs a 6-1 = 5mm drill).
| Thread size | Tap drill (mm) |
|---|---|
| M1.6 x 0.35 | 1.25 |
| M2 x 0.4 | 1.6 |
| M2.5 x 0.45 | 2.05 |
| M3 x 0.5 | 2.5 |
| M4 x 0.7 | 3.3 |
| M5 x 0.8 | 4.2 |
| M6 x 1.0 | 5.0 |
| M8 x 1.25 | 6.75 |
| M10 x 1.5 | 8.5 |
| M12 x 1.75 | 10.25 |
| M14 x 2.0 | 12 |