10-32 tap drill size
Use a #21 drill (0.1590 in) for a 10-32 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | #21 | 0.1590 |
| Cutting tap, 50% thread (hard material) | #18 | 0.1695 |
| Roll / form tap, 65% thread | #16 | 0.1770 |
| Helicoil / STI insert (#10-32×1D) | #3 | 0.2130 |
- Pitch
- 0.7938 mm (32 TPI)
- Major Ø
- 0.1900
- Pitch Ø
- 0.1697
- Minor Ø
- 0.1517
10-32 tapping speeds and feeds
Feed = pitch (0.0313 in per rev). Starting points for a general-purpose HSS cut tap:
- Aluminum 6061 / 7075: 1,410 RPM · 44.1 IPM
- Free-machining / mild steel: 400 RPM · 12.5 IPM
- 304 / 316 stainless: 200 RPM · 6.25 IPM
10-32 tap speeds and feeds: all materials, form taps and G84 code · #21 drill size and speeds
Common questions
- What size drill for a 10-32 tap?
- Use a #21 drill (0.1590 in) for a 10-32 cutting tap at 75% thread.
- What drill for a 10-32 roll (form) tap?
- About 0.1762 in; the nearest standard drill is #16. Check your tap maker's table.
- What drill for a 10-32 Helicoil?
- Drill #3 (0.2130 in), then tap with the 10-32 STI tap.
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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