Tap drill size
Metric thread → drill diameter before tapping
| Thread | Pitch, mm | Drill, mm |
|---|---|---|
| M3 | 0.5 | 2.5 |
| M4 | 0.7 | 3.3 |
| M5 | 0.8 | 4.2 |
| M6 | 1 | 5 |
| M8 | 1.25 | 6.8 |
| M10 | 1.5 | 8.5 |
| M12 | 1.75 | 10.2 |
| M14 | 2 | 12 |
| M16 | 2 | 14 |
| M20 | 2.5 | 17.5 |
Drill = thread Ø − pitch (M8×1.25 → 6.8 mm). For soft metals (aluminium, brass) add 0.1 mm. Fine pitches (M8×1.0 → 7.0 mm) — see fine pitch tables. Oil the tap.