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M5 x 0.8 tap drill size
Use a 4.2 mm drill to tap M5 x 0.8 (coarse pitch). The rule is major diameter minus pitch: 5 − 0.8 = 4.2 mm. Closest inch drill: #19 (4.22 mm).
M5 x 0.8 thread specifications
| Thread | M5 x 0.8 ISO metric coarse |
|---|---|
| Major (nominal) diameter | .1969 in / 5.00 mm |
| Pitch | 0.8 mm (≈ 31.7 threads per inch) |
| Recommended tap drill | 4.2 mm = .1654 in |
M5 clearance hole (ISO 273)
| Fit | Hole diameter |
|---|---|
| Fine (close) | 5.3 mm |
| Medium (normal) | 5.5 mm |
| Coarse (loose) | 5.8 mm |
A clearance hole lets the M5 bolt pass through freely. Drill the tap-drill size only in the part that gets threaded.
Tips for tapping M5 x 0.8
- 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 (3.2 mm here).
- Thread engagement of 1–1.5 × the diameter (5.0–7.5 mm) is enough for most steel parts. Softer materials need more.