M5 x 0.8 tap drill size
4.2 mm
- Inches
- 0.1654
- Inch bit
- #19
- Thread
- 77%
Drill a 4.2 mm hole before cutting an M5 thread with 0.8 mm pitch. The rule for metric taps is diameter minus pitch.
No metric bits? A #19 bit (0.1660 in) gives about 75% thread.
M5 x 0.8 thread and hole sizes
| Thread | M5, 0.8 mm pitch, coarse |
|---|---|
| Major diameter | 5 mm 0.1969 in |
| Tap drill | 4.2 mm 0.1654 in |
| Closest inch bit | #19 0.1660 in |
| Clearance hole, close fit | 5.3 mm |
| Clearance hole, medium fit | 5.5 mm |
Why 4.2 mm
Subtract the pitch from the diameter: 5 minus 0.8 is 4.2 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
- M5 x 0.8 tap
- 4.2 mm drill bit
- Tap and drill set
- Drill bit size gauge
- Thread pitch gauge
- Cutting oil for tapping
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