3/4-10 tap drill size
Use a 21/32" drill (0.6562 in) for a 3/4-10 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | 21/32" | 0.6562 |
| Cutting tap, 50% thread (hard material) | 11/16" | 0.6875 |
| Roll / form tap, 65% thread | 45/64 | 0.7031 |
| Helicoil / STI insert (3/4-10×1D) | 49/64" | 0.7656 |
- Pitch
- 2.54 mm (10 TPI)
- Major Ø
- 0.7500
- Pitch Ø
- 0.6850
- Minor Ø
- 0.6273
3/4-10 tapping speeds and feeds
Feed = pitch (0.1000 in per rev). Starting points for a general-purpose HSS cut tap:
- Aluminum 6061 / 7075: 360 RPM · 36.0 IPM
- Free-machining / mild steel: 100 RPM · 10.0 IPM
- 304 / 316 stainless: 50 RPM · 5.00 IPM
3/4-10 tap speeds and feeds: all materials, form taps and G84 code · 21/32" drill size and speeds
Common questions
- What size drill for a 3/4-10 tap?
- Use a 21/32" drill (0.6562 in) for a 3/4-10 cutting tap at 75% thread.
- What drill for a 3/4-10 roll (form) tap?
- About 0.7058 in; the nearest standard drill is 45/64. Check your tap maker's table.
- What drill for a 3/4-10 Helicoil?
- Drill 49/64" (0.7656 in), then tap with the 3/4-10 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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