5/8-11 tap drill size
Use a 17/32" drill (0.5312 in) for a 5/8-11 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | 17/32" | 0.5312 |
| Cutting tap, 50% thread (hard material) | 9/16" | 0.5625 |
| Roll / form tap, 65% thread | 37/64 | 0.5781 |
| Helicoil / STI insert (5/8-11×1D) | 41/64" | 0.6406 |
- Pitch
- 2.3091 mm (11 TPI)
- Major Ø
- 0.6250
- Pitch Ø
- 0.5660
- Minor Ø
- 0.5135
Common questions
- What size drill for a 5/8-11 tap?
- Use a 17/32" drill (0.5312 in) for a 5/8-11 cutting tap at 75% thread.
- What drill for a 5/8-11 roll (form) tap?
- About 0.5848 in; the nearest standard drill is 37/64. Check your tap maker's table.
- What drill for a 5/8-11 Helicoil?
- Drill 41/64" (0.6406 in), then tap with the 5/8-11 STI tap.
Other UNC 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.