12-28 tap drill size
Use a #14 drill (0.1820 in) for a 12-28 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | #14 | 0.1820 |
| Cutting tap, 50% thread (hard material) | #10 | 0.1935 |
| Roll / form tap, 65% thread | #7 | 0.2010 |
- Pitch
- 0.9071 mm (28 TPI)
- Major Ø
- 0.2160
- Pitch Ø
- 0.1928
- Minor Ø
- 0.1773
Common questions
- What size drill for a 12-28 tap?
- Use a #14 drill (0.1820 in) for a 12-28 cutting tap at 75% thread.
- What drill for a 12-28 roll (form) tap?
- About 0.2002 in; the nearest standard drill is #7. Check your tap maker's table.
Other UNF 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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