12-24 tap drill size
Use a #16 drill (0.1770 in) for a 12-24 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | #16 | 0.1770 |
| Cutting tap, 50% thread (hard material) | #12 | 0.1890 |
| Roll / form tap, 65% thread | #8 | 0.1990 |
- Pitch
- 1.0583 mm (24 TPI)
- Major Ø
- 0.2160
- Pitch Ø
- 0.1889
- Minor Ø
- 0.1709
12-24 tapping speeds and feeds
Feed = pitch (0.0417 in per rev). Starting points for a general-purpose HSS cut tap:
- Aluminum 6061 / 7075: 1,240 RPM · 51.7 IPM
- Free-machining / mild steel: 350 RPM · 14.6 IPM
- 304 / 316 stainless: 180 RPM · 7.50 IPM
12-24 tap speeds and feeds: all materials, form taps and G84 code · #16 drill size and speeds
Common questions
- What size drill for a 12-24 tap?
- Use a #16 drill (0.1770 in) for a 12-24 cutting tap at 75% thread.
- What drill for a 12-24 roll (form) tap?
- About 0.1976 in; the nearest standard drill is #8. Check your tap maker's table.
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.
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