4-4 tap drill size
Use a 3-3/4 drill (3.7500 in) for a 4-4 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | 3-3/4 | 3.7500 |
| Cutting tap, 50% thread (hard material) | 3-13/16 | 3.8125 |
| Roll / form tap, 65% thread | 3-7/8 | 3.8750 |
- Pitch
- 6.35 mm (4 TPI)
- Major Ø
- 4.0000
- Pitch Ø
- 3.8376
- Minor Ø
- 3.7294
4-4 tapping speeds and feeds
Feed = pitch (0.2500 in per rev). Starting points for a general-purpose HSS cut tap:
- Aluminum 6061 / 7075: 70 RPM · 17.5 IPM
- Free-machining / mild steel: 20 RPM · 5.00 IPM
- 304 / 316 stainless: 10 RPM · 2.50 IPM
4-4 tap speeds and feeds: all materials, form taps and G84 code
Common questions
- What size drill for a 4-4 tap?
- Use a 3-3/4 drill (3.7500 in) for a 4-4 cutting tap at 75% thread.
- What drill for a 4-4 roll (form) tap?
- About 3.8895 in; the nearest standard drill is 3-7/8. 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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