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M12 x 1.25 tap drill size
Use a 10.8 mm drill to tap M12 x 1.25 (fine pitch). The rule is major diameter minus pitch: 12 − 1.25 = 10.75 mm, rounded to the nearest standard drill (DIN 336). Closest inch drill: 27/64 (10.72 mm).
M12 x 1.25 thread specifications
| Thread | M12 x 1.25 ISO metric fine |
|---|---|
| Major (nominal) diameter | .4724 in / 12.00 mm |
| Pitch | 1.25 mm (≈ 20.3 threads per inch) |
| Recommended tap drill | 10.8 mm = .4252 in |
M12 clearance hole (ISO 273)
| Fit | Hole diameter |
|---|---|
| Fine (close) | 13 mm |
| Medium (normal) | 13.5 mm |
| Coarse (loose) | 14.5 mm |
A clearance hole lets the M12 bolt pass through freely. Drill the tap-drill size only in the part that gets threaded.
Tips for tapping M12 x 1.25
- Use cutting fluid, and with a hand tap back off about half a turn every turn or two to break the chip. Aluminium and soft materials are the exception: they tap cleanly with spiral-point taps.
- For blind holes, drill deeper than the thread you need. Allow at least 3–4 pitches beyond the last full thread for a plug tap (5.0 mm here).
- Thread engagement of 1–1.5 × the diameter (12.0–18.0 mm) is enough for most steel parts. Softer materials need more.