M14 x 1.5 tap drill size
12.5 mm
- Inches
- 0.4921
- Inch bit
- 1/2"
- Thread
- 77%
Drill a 12.5 mm hole before cutting an M14 thread with 1.5 mm pitch. The rule for metric taps is diameter minus pitch.
No metric bits? A 1/2" bit (0.5000 in) gives about 67% thread.
M14 x 1.5 thread and hole sizes
| Thread | M14, 1.5 mm pitch, fine |
|---|---|
| Major diameter | 14 mm 0.5512 in |
| Tap drill | 12.5 mm 0.4921 in |
| Closest inch bit | 1/2" 0.5000 in |
| Clearance hole, close fit | 15 mm |
| Clearance hole, medium fit | 15.5 mm |
Why 12.5 mm
Subtract the pitch from the diameter: 14 minus 1.5 is 12.5 mm. That leaves 77% thread, the usual target for a cut tap.
More thread than that adds almost no strength and makes the tap much easier to break. In hard or tough material, go 0.1 mm larger.
Tools for this job
- M14 x 1.5 tap
- 12.5 mm drill bit
- Tap and drill set
- Drill bit size gauge
- Thread pitch gauge
- Cutting oil for tapping
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