1/2-28 tap drill size
Use a 15/32 drill (0.4688 in) for a 1/2-28 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | 15/32 | 0.4688 |
| Cutting tap, 50% thread (hard material) | 31/64 | 0.4844 |
| Roll / form tap, 65% thread | 31/64 | 0.4844 |
- Pitch
- 0.9071 mm (28 TPI)
- Major Ø
- 0.5000
- Pitch Ø
- 0.4768
- Minor Ø
- 0.4613
Common questions
- What size drill for a 1/2-28 tap?
- Use a 15/32 drill (0.4688 in) for a 1/2-28 cutting tap at 75% thread.
- What drill for a 1/2-28 roll (form) tap?
- About 0.4842 in; the nearest standard drill is 31/64. 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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