M56 Bolt Torque
An M56 8.8 bolt with a coarse M56×5.5 thread needs about 9769.5 N·m (7205.6 ft·lb) when dry and 7221.4 N·m (5326.3 ft·lb) when oiled, tightened to 70% of yield (clamp force 909.4 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 341.0 kN76669 lbf | 3663.6 N·m2702.1 ft·lb | 2708.0 N·m1997.3 ft·lb | 1752.5 N·m1292.6 ft·lb |
| 4.8 | 454.7 kN102226 lbf | 4884.7 N·m3602.8 ft·lb | 3610.7 N·m2663.1 ft·lb | 2336.7 N·m1723.4 ft·lb |
| 5.6 | 426.3 kN95837 lbf | 4579.4 N·m3377.6 ft·lb | 3385.0 N·m2496.7 ft·lb | 2190.6 N·m1615.7 ft·lb |
| 5.8 | 568.4 kN127782 lbf | 6105.9 N·m4503.5 ft·lb | 4513.4 N·m3328.9 ft·lb | 2920.9 N·m2154.3 ft·lb |
| 6.8 | 682.1 kN153339 lbf | 7327.1 N·m5404.2 ft·lb | 5416.1 N·m3994.7 ft·lb | 3505.0 N·m2585.2 ft·lb |
| 8.8 | 909.4 kN204452 lbf | 9769.5 N·m7205.6 ft·lb | 7221.4 N·m5326.3 ft·lb | 4673.4 N·m3446.9 ft·lb |
| 10.9 | 1278.9 kN287510 lbf | 13738.3 N·m10132.9 ft·lb | 10155.1 N·m7490.0 ft·lb | 6571.9 N·m4847.2 ft·lb |
| 12.9 | 1534.7 kN345012 lbf | 16486.0 N·m12159.5 ft·lb | 12186.2 N·m8988.1 ft·lb | 7886.3 N·m5816.6 ft·lb |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 360.2 kN80973 lbf | 3812.6 N·m2812.1 ft·lb | 2795.0 N·m2061.5 ft·lb | 1777.3 N·m1310.9 ft·lb |
| 4.8 | 480.2 kN107964 lbf | 5083.5 N·m3749.4 ft·lb | 3726.6 N·m2748.6 ft·lb | 2369.8 N·m1747.9 ft·lb |
| 5.6 | 450.2 kN101216 lbf | 4765.8 N·m3515.1 ft·lb | 3493.7 N·m2576.8 ft·lb | 2221.7 N·m1638.6 ft·lb |
| 5.8 | 600.3 kN134955 lbf | 6354.4 N·m4686.8 ft·lb | 4658.3 N·m3435.8 ft·lb | 2962.2 N·m2184.8 ft·lb |
| 6.8 | 720.4 kN161945 lbf | 7625.3 N·m5624.1 ft·lb | 5590.0 N·m4123.0 ft·lb | 3554.7 N·m2621.8 ft·lb |
| 8.8 | 960.5 kN215927 lbf | 10167.0 N·m7498.8 ft·lb | 7453.3 N·m5497.3 ft·lb | 4739.6 N·m3495.7 ft·lb |
| 10.9 | 1350.7 kN303648 lbf | 14297.4 N·m10545.2 ft·lb | 10481.2 N·m7730.5 ft·lb | 6665.0 N·m4915.9 ft·lb |
| 12.9 | 1620.8 kN364377 lbf | 17156.8 N·m12654.2 ft·lb | 12577.4 N·m9276.6 ft·lb | 7998.0 N·m5899.0 ft·lb |
Torque for M56 hex head bolts and nuts, standard ISO/ASME heads on steel with a 62.0 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
M56 thread and dimensions
- Coarse thread
- M56×5.5 — pitch 5.5 mm
- Fine thread
- M56×4 — pitch 4 mm
- Tensile stress area Aₛ
- 2030.0 mm² (coarse), 2144.0 mm² (fine)
- Pitch diameter d₂
- 52.428 mm
- Tap drill
- 50.5 mm (coarse), 52 mm (fine)
- Wrench size (hex head)
- 85 mm
- Clearance hole
- 62.0 mm
How the M56 torque is calculated
Preload is 70% of the bolt's yield strength times its tensile stress area. Torque then follows the ISO 16047 / VDI 2230 formula, which splits it into thread pitch, thread friction and friction under the head:
F = 70% × 640 MPa × 2030.0 mm² = 909.4 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 909.4 kN × (0.16·5.5 + 0.58·0.15·52.43 + 0.15·73.50/2) mm = 9769.5 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (73.50 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for an M56 8.8 bolt?
About 9769.5 N·m (7205.6 ft·lb) with dry threads, 7221.4 N·m (5326.3 ft·lb) with oiled threads and 4673.4 N·m (3446.9 ft·lb) with PTFE or moly paste, for a coarse M56×5.5 thread tightened to 70% of yield. The resulting clamp force is 909.4 kN.
What is the torque for an M56 10.9 bolt?
About 13738.3 N·m (10132.9 ft·lb) with dry threads, 10155.1 N·m (7490.0 ft·lb) with oiled threads and 6571.9 N·m (4847.2 ft·lb) with PTFE or moly paste, for a coarse M56×5.5 thread tightened to 70% of yield. The resulting clamp force is 1278.9 kN.
What size wrench fits an M56 bolt?
A standard M56 hex head bolt or nut takes a 85 mm wrench or socket.
What drill size do I need to tap M56?
Use a 50.5 mm drill for M56×5.5 and 52 mm for M56×4.