10-24 tap drill size
Use a #25 drill (0.1495 in) for a 10-24 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | #25 | 0.1495 |
| Cutting tap, 50% thread (hard material) | #20 | 0.1610 |
| Roll / form tap, 65% thread | 11/64 | 0.1719 |
| Helicoil / STI insert (#10-24×1D) | #10 | 0.1935 |
- Pitch
- 1.0583 mm (24 TPI)
- Major Ø
- 0.1900
- Pitch Ø
- 0.1629
- Minor Ø
- 0.1389
10-24 tapping speeds and feeds
Feed = pitch (0.0417 in per rev). Starting points for a general-purpose HSS cut tap:
- Aluminum 6061 / 7075: 1,410 RPM · 58.8 IPM
- Free-machining / mild steel: 400 RPM · 16.7 IPM
- 304 / 316 stainless: 200 RPM · 8.33 IPM
10-24 tap speeds and feeds: all materials, form taps and G84 code · #25 drill size and speeds
Common questions
- What size drill for a 10-24 tap?
- Use a #25 drill (0.1495 in) for a 10-24 cutting tap at 75% thread.
- What drill for a 10-24 roll (form) tap?
- About 0.1716 in; the nearest standard drill is 11/64. Check your tap maker's table.
- What drill for a 10-24 Helicoil?
- Drill #10 (0.1935 in), then tap with the 10-24 STI tap.
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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