M30 × 3.5 tap drill size

26.50 mm drill — or 1-3/64 (1.0469 in) = 75% thread

M30 coarse series, 3.5 mm pitch. Tap drill Ø = nominal − pitch = 30 − 3.5 = 26.50 mm (≈77% thread, the standard chart value).

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