M20 × 1.5 tap drill size
18.50 mm drill — or 47/64 (0.7344 in) = 69% thread
M20 fine series, 1.5 mm pitch. Tap drill Ø = nominal − pitch = 20 − 1.5 = 18.50 mm (≈77% thread, the standard chart value).
| Drill | Size | Thread % |
|---|---|---|
| 18.50 mm | 0.7283 in | 77% |
| 47/64 (inch) | 0.7344 in / 18.65 mm | 69% |
Rounding to your nearest stock drill moves the thread percentage only a few points. Cut taps only — roll-form taps need a larger hole. Verify before you cut.
Need a different thread percentage? Open the tap drill calculator · Metric tap chart · All calculators