Metric fine
Tap drill 54.5 mm for a M56 × 1.5 thread — major Ø 56 mm, pitch 1.5 mm (16.93 TPI).
Profile
| Designation | M56 × 1.5 |
|---|---|
| Major (outside) diameter | 56 mm · 2.2047" |
| Pitch | 1.5 mm · 16.93 TPI |
| Pitch diameter | 55.026 mm · 2.1664" |
| Minor diameter (external) | 54.16 mm · 2.1323" |
| Minor diameter (internal) | 54.376 mm · 2.1408" |
| Recommended tap drill | 54.5 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 | 2340.8 mm² | 1018.24 kN | 11404.2 N·m |
| Class 10.9 | 2340.8 mm² | 1457.13 kN | 16319.9 N·m |
| Class 12.9 | 2340.8 mm² | 1702.91 kN | 19072.6 N·m |
For a M56 × 1.5 thread, drill the hole with a 54.5 mm tap drill (54.5 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 56 mm and a pitch of 1.5 mm (16.93 TPI).
To pass a M56 × 1.5 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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