M8×1.25 tap drill size
Use a 6.8mm drill (6.80 mm) for a M8×1.25 cutting tap at 75% thread.
| Tap type | Drill | Decimal (mm) |
|---|---|---|
| Cutting tap, 75% thread | 6.8mm | 6.80 |
| Cutting tap, 50% thread (hard material) | 7.1mm | 7.10 |
| Roll / form tap, 65% thread | 7.45 mm | 7.45 |
| Helicoil / STI insert (M8×1.25×1D) | 9.0mm | 9.00 |
- Pitch
- 1.25 mm
- Major Ø
- 8.00
- Pitch Ø
- 7.19
- Minor Ø
- 6.65
Common questions
- What size drill for a M8×1.25 tap?
- Use a 6.8mm drill (6.80 mm) for a M8×1.25 cutting tap at 75% thread.
- What drill for a M8×1.25 roll (form) tap?
- About 7.45 mm; the nearest standard drill is 7.45 mm. Check your tap maker's table.
- What drill for a M8×1.25 Helicoil?
- Drill 9.0mm (9.00 mm), then tap with the M8×1.25 STI tap.
Other Metric sizes
Drill sizes from Machinery's Handbook and ASME B1.1/B1.13M; roll tap sizes from the form-tap formula. Tap and insert makers' tables are authoritative.