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Tap Drill Chart with G84 Tapping Feeds
Standard cut-tap drill sizes for roughly 75% thread engagement, with the decimal size and the feed per minute at 500 RPM so you can sanity-check a G84 line at a glance.
Inch tap drills (UNC / UNF)
| Tap | Drill | Decimal | G84 F @ 500 RPM |
|---|---|---|---|
| #4-40 | #43 | 0.0890 | F12.5 |
| #6-32 | #36 | 0.1065 | F15.63 |
| #8-32 | #29 | 0.1360 | F15.63 |
| #10-24 | #25 | 0.1495 | F20.83 |
| #10-32 | #21 | 0.1590 | F15.63 |
| 1/4-20 | #7 | 0.2010 | F25.0 |
| 1/4-28 | #3 | 0.2130 | F17.86 |
| 5/16-18 | F | 0.2570 | F27.78 |
| 5/16-24 | I | 0.2720 | F20.83 |
| 3/8-16 | 5/16 | 0.3125 | F31.25 |
| 3/8-24 | Q | 0.3320 | F20.83 |
| 7/16-14 | U | 0.3680 | F35.71 |
| 7/16-20 | 25/64 | 0.3906 | F25.0 |
| 1/2-13 | 27/64 | 0.4219 | F38.46 |
| 1/2-20 | 29/64 | 0.4531 | F25.0 |
| 9/16-12 | 31/64 | 0.4844 | F41.67 |
| 9/16-18 | 33/64 | 0.5156 | F27.78 |
| 5/8-11 | 17/32 | 0.5312 | F45.45 |
| 5/8-18 | 37/64 | 0.5781 | F27.78 |
| 3/4-10 | 21/32 | 0.6562 | F50.0 |
| 3/4-16 | 11/16 | 0.6875 | F31.25 |
| 7/8-9 | 49/64 | 0.7656 | F55.56 |
| 1-8 | 7/8 | 0.8750 | F62.5 |
| 1-12 | 59/64 | 0.9219 | F41.67 |
Metric coarse tap drills
| Tap | Drill (mm) | Decimal (in) | G84 F @ 500 RPM |
|---|---|---|---|
| M3 × 0.5 | 2.5 | 0.0984 | F250. mm/min |
| M4 × 0.7 | 3.3 | 0.1299 | F350. mm/min |
| M5 × 0.8 | 4.2 | 0.1654 | F400. mm/min |
| M6 × 1.0 | 5.0 | 0.1969 | F500. mm/min |
| M8 × 1.25 | 6.8 | 0.2677 | F625. mm/min |
| M10 × 1.5 | 8.5 | 0.3346 | F750. mm/min |
| M12 × 1.75 | 10.2 | 0.4016 | F875. mm/min |
| M14 × 2.0 | 12.0 | 0.4724 | F1000. mm/min |
| M16 × 2.0 | 14.0 | 0.5512 | F1000. mm/min |
| M20 × 2.5 | 17.5 | 0.6890 | F1250. mm/min |
Tapping feed formula
- Inch, G94: F = RPM ÷ TPI
- Metric, G94: F = RPM × pitch
- Any, G95/G99: F = pitch (1 ÷ TPI)
- Metric tap drill: major Ø − pitch
Roll-form taps need a larger drill than this chart — check the tap maker's recommendation.
Tap drill questions
What size drill for a 1/4-20 tap?
A #7 drill (0.201 in) gives about 75% thread.
What size drill for an M6 × 1.0 tap?
A 5.0 mm drill. For metric coarse threads, tap drill = major diameter − pitch.
How do I calculate the feed for G84 on a Haas?
In feed-per-minute mode, F = RPM ÷ TPI (inch) or RPM × pitch (metric). In feed-per-rev mode, F is the pitch.