Metric fine
Tap drill 54 mm for a M56 × 2.0 thread — major Ø 56 mm, pitch 2 mm (12.7 TPI).
Profile
| Designation | M56 × 2.0 |
|---|---|
| Major (outside) diameter | 56 mm · 2.2047" |
| Pitch | 2 mm · 12.7 TPI |
| Pitch diameter | 54.701 mm · 2.1536" |
| Minor diameter (external) | 53.546 mm · 2.1081" |
| Minor diameter (internal) | 53.835 mm · 2.1195" |
| Recommended tap drill | 54 mm · ≈77% thread |
| Clearance hole | Close 58 · Normal 62 · Loose 66 mm |
| Hex head (across flats) | 85 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 | 2300.7 mm² | 1000.81 kN | 11209.1 N·m |
| Class 10.9 | 2300.7 mm² | 1432.2 kN | 16040.6 N·m |
| Class 12.9 | 2300.7 mm² | 1673.77 kN | 18746.2 N·m |
For a M56 × 2.0 thread, drill the hole with a 54 mm tap drill (54 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 56 mm and a pitch of 2 mm (12.7 TPI).
To pass a M56 × 2.0 bolt through a part rather than thread it, use a clearance hole: Close 58 · Normal 62 · Loose 66 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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