Beneath you find the table with the required pre-drilling diameter for tapping metric thread
| Nominal diameter | Pitch P | Drill diameter (mm) |
| M3 | 0,50 | 2,50 |
| M4 | 0,70 | 3,30 |
| M5 | 0,80 | 4,20 |
| M6 | 1,00 | 5,00 |
| M8 | 1,25 | 6,75 (6,80) |
| M10 | 1,50 | 8,50 |
| M12 | 1,75 | 10,25 (10,50) |
| M14 | 2,00 | 12,00 |
| M16 | 2,00 | 14,00 |
| M18 | 2,50 | 15,50 |
| M20 | 2,50 | 17,50 |
| M22 | 2,50 | 19,50 |
| M24 | 3,00 | 21,00 |
Drill diameter = Nominal diameter - Pitch
Remark:
- Use a 6,80 mm drill for the theoretical drill diameter 6,75 mm.
- Use a 10,50 mm drill for the theoretical drill diameter 10,25 mm.