1-12 tap drill size
Use a 59/64 drill (0.9219 in) for a 1-12 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | 59/64 | 0.9219 |
| Cutting tap, 50% thread (hard material) | 61/64 | 0.9531 |
| Roll / form tap, 65% thread | 31/32 | 0.9688 |
- Pitch
- 2.1167 mm (12 TPI)
- Major Ø
- 1.0000
- Pitch Ø
- 0.9459
- Minor Ø
- 0.9098
1-12 tapping speeds and feeds
Feed = pitch (0.0833 in per rev). Starting points for a general-purpose HSS cut tap:
- Aluminum 6061 / 7075: 270 RPM · 22.5 IPM
- Free-machining / mild steel: 80 RPM · 6.67 IPM
- 304 / 316 stainless: 40 RPM · 3.33 IPM
1-12 tap speeds and feeds: all materials, form taps and G84 code · 59/64 drill size and speeds
Common questions
- What size drill for a 1-12 tap?
- Use a 59/64 drill (0.9219 in) for a 1-12 cutting tap at 75% thread.
- What drill for a 1-12 roll (form) tap?
- About 0.9632 in; the nearest standard drill is 31/32. 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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