Metric coarse
Tap drill 37.5 mm for a M42 × 4.5 thread — major Ø 42 mm, pitch 4.5 mm (5.64 TPI).
Profile
| Designation | M42 × 4.5 |
|---|---|
| Major (outside) diameter | 42 mm · 1.6535" |
| Pitch | 4.5 mm · 5.64 TPI |
| Pitch diameter | 39.077 mm · 1.5385" |
| Minor diameter (external) | 36.479 mm · 1.4362" |
| Minor diameter (internal) | 37.129 mm · 1.4618" |
| Recommended tap drill | 37.5 mm · ≈77% thread |
| Clearance hole | Close 43 · Normal 45 · Loose 48 mm |
| Hex head (across flats) | 65 mm |
| Socket key (across flats) | 32 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 | 1120.9 mm² | 487.6 kN | 4095.8 N·m |
| Class 10.9 | 1120.9 mm² | 697.77 kN | 5861.2 N·m |
| Class 12.9 | 1120.9 mm² | 815.46 kN | 6849.9 N·m |
For a M42 × 4.5 thread, drill the hole with a 37.5 mm tap drill (37.5 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 42 mm and a pitch of 4.5 mm (5.64 TPI).
To pass a M42 × 4.5 bolt through a part rather than thread it, use a clearance hole: Close 43 · Normal 45 · Loose 48 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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