1/4-32 tap drill size
Use a 7/32 drill (0.2188 in) for a 1/4-32 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | 7/32 | 0.2188 |
| Cutting tap, 50% thread (hard material) | #1 | 0.2280 |
| Roll / form tap, 65% thread | 15/64 | 0.2344 |
- Pitch
- 0.7938 mm (32 TPI)
- Major Ø
- 0.2500
- Pitch Ø
- 0.2297
- Minor Ø
- 0.2162
Common questions
- What size drill for a 1/4-32 tap?
- Use a 7/32 drill (0.2188 in) for a 1/4-32 cutting tap at 75% thread.
- What drill for a 1/4-32 roll (form) tap?
- About 0.2362 in; the nearest standard drill is 15/64. 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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