Metric coarse
Tap drill 4.2 mm for a M5 × 0.8 thread — major Ø 5 mm, pitch 0.8 mm (31.75 TPI).
Profile
| Designation | M5 × 0.8 |
|---|---|
| Major (outside) diameter | 5 mm · 0.1969" |
| Pitch | 0.8 mm · 31.75 TPI |
| Pitch diameter | 4.48 mm · 0.1764" |
| Minor diameter (external) | 4.019 mm · 0.1582" |
| Minor diameter (internal) | 4.134 mm · 0.1628" |
| Recommended tap drill | 4.2 mm · ≈77% thread |
| Clearance hole | Close 5.3 · Normal 5.5 · Loose 5.8 mm |
| Hex head (across flats) | 8 mm |
| Socket key (across flats) | 4 mm |
ISO 273 clearance holes (fine / medium / coarse).
Target preload is 75% of proof load; torque is estimated from T = K · F · d.
| Grade / class | Stress area | Preload | Torque |
|---|---|---|---|
| Class 8.8 | 14.2 mm² | 6.17 kN | 6.17 N·m |
| Class 10.9 | 14.2 mm² | 8.83 kN | 8.83 N·m |
| Class 12.9 | 14.2 mm² | 10.32 kN | 10.3 N·m |
For a M5 × 0.8 thread, drill the hole with a 4.2 mm tap drill (4.2 mm — the standard D − P rule) before tapping. That produces roughly 77% thread engagement, the usual target for a strong, tappable hole. The mating bolt has a major diameter of 5 mm and a pitch of 0.8 mm (31.75 TPI).
To pass a M5 × 0.8 bolt through a part rather than thread it, use a clearance hole: Close 5.3 · Normal 5.5 · Loose 5.8 mm.
All values are generated from the standard thread formulas (ISO 68-1 / ASME B1.1) and published standard tables — not hand-entered. See the full reference.
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