5/8-11 tap drill size
Use a 17/32" drill (0.5312 in) for a 5/8-11 cutting tap at 75% thread.
| Tap type | Drill | Decimal (in) |
|---|---|---|
| Cutting tap, 75% thread | 17/32" | 0.5312 |
| Cutting tap, 50% thread (hard material) | 9/16" | 0.5625 |
| Roll / form tap, 65% thread | 37/64 | 0.5781 |
| Helicoil / STI insert (5/8-11×1D) | 41/64" | 0.6406 |
- Pitch
- 2.3091 mm (11 TPI)
- Major Ø
- 0.6250
- Pitch Ø
- 0.5660
- Minor Ø
- 0.5135
5/8-11 tapping speeds and feeds
Feed = pitch (0.0909 in per rev). Starting points for a general-purpose HSS cut tap:
- Aluminum 6061 / 7075: 430 RPM · 39.1 IPM
- Free-machining / mild steel: 120 RPM · 10.9 IPM
- 304 / 316 stainless: 60 RPM · 5.45 IPM
5/8-11 tap speeds and feeds: all materials, form taps and G84 code · 17/32" drill size and speeds
Common questions
- What size drill for a 5/8-11 tap?
- Use a 17/32" drill (0.5312 in) for a 5/8-11 cutting tap at 75% thread.
- What drill for a 5/8-11 roll (form) tap?
- About 0.5848 in; the nearest standard drill is 37/64. Check your tap maker's table.
- What drill for a 5/8-11 Helicoil?
- Drill 41/64" (0.6406 in), then tap with the 5/8-11 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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