3/4-20 tap drill size
Use a 45/64 drill (0.7031 in) for a 3/4-20 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | 45/64 | 0.7031 |
| Cutting tap, 50% thread (hard material) | 23/32 | 0.7188 |
| Roll / form tap, 65% thread | 47/64 | 0.7344 |
- Pitch
- 1.27 mm (20 TPI)
- Major Ø
- 0.7500
- Pitch Ø
- 0.7175
- Minor Ø
- 0.6959
Common questions
- What size drill for a 3/4-20 tap?
- Use a 45/64 drill (0.7031 in) for a 3/4-20 cutting tap at 75% thread.
- What drill for a 3/4-20 roll (form) tap?
- About 0.7279 in; the nearest standard drill is 47/64. Check your tap maker's table.
Other UNEF 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.
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