4-48 tap drill size
Use a #42 drill (0.0935 in) for a 4-48 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | #42 | 0.0935 |
| Cutting tap, 50% thread (hard material) | #40 | 0.0980 |
| Roll / form tap, 65% thread | #37 | 0.1040 |
| Helicoil / STI insert (#4-48×1D) | #27 | 0.1440 |
- Pitch
- 0.5292 mm (48 TPI)
- Major Ø
- 0.1120
- Pitch Ø
- 0.0985
- Minor Ø
- 0.0864
4-48 tapping speeds and feeds
Feed = pitch (0.0208 in per rev). Starting points for a general-purpose HSS cut tap:
- Aluminum 6061 / 7075: 2,390 RPM · 49.8 IPM
- Free-machining / mild steel: 680 RPM · 14.2 IPM
- 304 / 316 stainless: 340 RPM · 7.08 IPM
4-48 tap speeds and feeds: all materials, form taps and G84 code · #42 drill size and speeds
Common questions
- What size drill for a 4-48 tap?
- Use a #42 drill (0.0935 in) for a 4-48 cutting tap at 75% thread.
- What drill for a 4-48 roll (form) tap?
- About 0.1028 in; the nearest standard drill is #37. Check your tap maker's table.
- What drill for a 4-48 Helicoil?
- Drill #27 (0.1440 in), then tap with the 4-48 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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