Metric coarse
Tap drill 50.5 mm for a M56 × 5.5 thread — major Ø 56 mm, pitch 5.5 mm (4.62 TPI).
Profile
| Designation | M56 × 5.5 |
|---|---|
| Major (outside) diameter | 56 mm · 2.2047" |
| Pitch | 5.5 mm · 4.62 TPI |
| Pitch diameter | 52.428 mm · 2.0641" |
| Minor diameter (external) | 49.252 mm · 1.9391" |
| Minor diameter (internal) | 50.046 mm · 1.9703" |
| Recommended tap drill | 50.5 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 | 2030 mm² | 883.06 kN | 9890.2 N·m |
| Class 10.9 | 2030 mm² | 1263.68 kN | 14153.3 N·m |
| Class 12.9 | 2030 mm² | 1476.84 kN | 16540.6 N·m |
For a M56 × 5.5 thread, drill the hole with a 50.5 mm tap drill (50.5 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 5.5 mm (4.62 TPI).
To pass a M56 × 5.5 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.
Same diameter
Nearby sizes