Metric fine
Tap drill 37 mm for a M39 × 2.0 thread — major Ø 39 mm, pitch 2 mm (12.7 TPI).
Profile
| Designation | M39 × 2.0 |
|---|---|
| Major (outside) diameter | 39 mm · 1.5354" |
| Pitch | 2 mm · 12.7 TPI |
| Pitch diameter | 37.701 mm · 1.4843" |
| Minor diameter (external) | 36.546 mm · 1.4388" |
| Minor diameter (internal) | 36.835 mm · 1.4502" |
| Recommended tap drill | 37 mm · ≈77% thread |
| Clearance hole | Close 40 · Normal 42 · Loose 45 mm |
| Hex head (across flats) | 60 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 | 1082.4 mm² | 470.85 kN | 3672.6 N·m |
| Class 10.9 | 1082.4 mm² | 673.8 kN | 5255.6 N·m |
| Class 12.9 | 1082.4 mm² | 787.45 kN | 6142.1 N·m |
For a M39 × 2.0 thread, drill the hole with a 37 mm tap drill (37 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 39 mm and a pitch of 2 mm (12.7 TPI).
To pass a M39 × 2.0 bolt through a part rather than thread it, use a clearance hole: Close 40 · Normal 42 · Loose 45 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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