M6×0.75 Tap Drill Size
The number you came for, then the reasoning behind it.
M6×0.75 tap drill — 75% thread
5.25 mm
5.269 mm exact · nearest inch drill #5 (0.2055")
How it's calculated
Tap drill = major diameter − pitch → 6 − 0.75 = 5.25 mm
The exact 75% figure is major − (pitch × 75 / 76.98). The simple subtract-the-pitch rule lands within a hundredth of a millimetre of it, which is why every machinist uses it.
All engagement percentages
| % thread | Exact hole | Metric drill | Inch equivalent |
|---|---|---|---|
| 50% | 5.513 mm | 5.5 mm | 0.2188" (7/32 drill) |
| 65% | 5.367 mm | 5.4 mm | 0.2130" (#3 drill) |
| 75% | 5.269 mm | 5.25 mm | 0.2055" (#5 drill) |
| 85% | 5.172 mm | 5.2 mm | 0.2040" (#6 drill) |
Which percentage should you actually use?
75% for through-holes in mild steel and aluminium. 65% for blind holes, stainless, titanium and anything where the tap is at risk. 50% for hand-tapping deep holes. The strength you give up going from 75% to 60% is around 5%; the tapping torque you give up is around 30%. In practice the threads almost never fail — the tap does.
75% for through-holes in mild steel and aluminium. 65% for blind holes, stainless, titanium and anything where the tap is at risk. 50% for hand-tapping deep holes. The strength you give up going from 75% to 60% is around 5%; the tapping torque you give up is around 30%. In practice the threads almost never fail — the tap does.