To tap an M3 thread (pitch 0.5 mm), drill a 2.5 mm hole for standard 6H tolerance. Use 2.6 mm for a looser 7H fit. M3 taps are common in small electronics, optics and instrument housings.
| Tolerance class | Drill diameter | Pitch | Thread depth |
|---|---|---|---|
| 6H (standard) | 2.5 mm | 0.5 mm | 4–6 mm |
| 7H (loose) | 2.6 mm | 0.5 mm | 4–6 mm |
| 4H (tight) | 2.45 mm | 0.5 mm | 4–6 mm |
FAQ
2.5 mm drill for standard M3 thread (6H, pitch 0.5 mm).
2.5 mm = 0.098 in. Closest imperial drill: #39 (0.0995 in) or 3/32 in (2.38 mm, slightly undersized).
Full M3 thread data in the app
Profile viewer, tolerance calculator, 28 thread types
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