M42 Bolt Torque
An M42 8.8 bolt with a coarse M42×4.5 thread needs about 4060.9 N·m (2995.2 ft·lb) when dry and 3010.0 N·m (2220.0 ft·lb) when oiled, tightened to 70% of yield (clamp force 502.2 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 188.3 kN42334 lbf | 1522.8 N·m1123.2 ft·lb | 1128.7 N·m832.5 ft·lb | 734.6 N·m541.8 ft·lb |
| 4.8 | 251.1 kN56446 lbf | 2030.5 N·m1497.6 ft·lb | 1505.0 N·m1110.0 ft·lb | 979.5 N·m722.4 ft·lb |
| 5.6 | 235.4 kN52918 lbf | 1903.5 N·m1404.0 ft·lb | 1410.9 N·m1040.6 ft·lb | 918.3 N·m677.3 ft·lb |
| 5.8 | 313.9 kN70557 lbf | 2538.1 N·m1872.0 ft·lb | 1881.2 N·m1387.5 ft·lb | 1224.4 N·m903.1 ft·lb |
| 6.8 | 376.6 kN84669 lbf | 3045.7 N·m2246.4 ft·lb | 2257.5 N·m1665.0 ft·lb | 1469.3 N·m1083.7 ft·lb |
| 8.8 | 502.2 kN112892 lbf | 4060.9 N·m2995.2 ft·lb | 3010.0 N·m2220.0 ft·lb | 1959.0 N·m1444.9 ft·lb |
| 10.9 | 706.2 kN158754 lbf | 5710.6 N·m4212.0 ft·lb | 4232.7 N·m3121.9 ft·lb | 2754.8 N·m2031.9 ft·lb |
| 12.9 | 847.4 kN190505 lbf | 6852.8 N·m5054.3 ft·lb | 5079.3 N·m3746.3 ft·lb | 3305.8 N·m2438.2 ft·lb |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 202.6 kN45547 lbf | 1606.6 N·m1185.0 ft·lb | 1177.8 N·m868.7 ft·lb | 749.0 N·m552.4 ft·lb |
| 4.8 | 270.1 kN60730 lbf | 2142.1 N·m1580.0 ft·lb | 1570.4 N·m1158.3 ft·lb | 998.7 N·m736.6 ft·lb |
| 5.6 | 253.3 kN56934 lbf | 2008.2 N·m1481.2 ft·lb | 1472.3 N·m1085.9 ft·lb | 936.3 N·m690.6 ft·lb |
| 5.8 | 337.7 kN75912 lbf | 2677.7 N·m1974.9 ft·lb | 1963.0 N·m1447.8 ft·lb | 1248.4 N·m920.7 ft·lb |
| 6.8 | 405.2 kN91094 lbf | 3213.2 N·m2369.9 ft·lb | 2355.6 N·m1737.4 ft·lb | 1498.0 N·m1104.9 ft·lb |
| 8.8 | 540.3 kN121459 lbf | 4284.3 N·m3159.9 ft·lb | 3140.8 N·m2316.5 ft·lb | 1997.4 N·m1473.2 ft·lb |
| 10.9 | 759.8 kN170802 lbf | 6024.7 N·m4443.6 ft·lb | 4416.8 N·m3257.6 ft·lb | 2808.8 N·m2071.7 ft·lb |
| 12.9 | 911.7 kN204962 lbf | 7229.7 N·m5332.3 ft·lb | 5300.1 N·m3909.2 ft·lb | 3370.6 N·m2486.0 ft·lb |
Torque for M42 hex head bolts and nuts, standard ISO/ASME heads on steel with a 45.0 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
M42 thread and dimensions
- Coarse thread
- M42×4.5 — pitch 4.5 mm
- Fine thread
- M42×3 — pitch 3 mm
- Tensile stress area Aₛ
- 1120.9 mm² (coarse), 1206.0 mm² (fine)
- Pitch diameter d₂
- 39.077 mm
- Tap drill
- 37.5 mm (coarse), 39 mm (fine)
- Wrench size (hex head)
- 65 mm
- Clearance hole
- 45.0 mm
How the M42 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 × 1120.9 mm² = 502.2 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 502.2 kN × (0.16·4.5 + 0.58·0.15·39.08 + 0.15·55.00/2) mm = 4060.9 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (55.00 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for an M42 8.8 bolt?
About 4060.9 N·m (2995.2 ft·lb) with dry threads, 3010.0 N·m (2220.0 ft·lb) with oiled threads and 1959.0 N·m (1444.9 ft·lb) with PTFE or moly paste, for a coarse M42×4.5 thread tightened to 70% of yield. The resulting clamp force is 502.2 kN.
What is the torque for an M42 10.9 bolt?
About 5710.6 N·m (4212.0 ft·lb) with dry threads, 4232.7 N·m (3121.9 ft·lb) with oiled threads and 2754.8 N·m (2031.9 ft·lb) with PTFE or moly paste, for a coarse M42×4.5 thread tightened to 70% of yield. The resulting clamp force is 706.2 kN.
What size wrench fits an M42 bolt?
A standard M42 hex head bolt or nut takes a 65 mm wrench or socket.
What drill size do I need to tap M42?
Use a 37.5 mm drill for M42×4.5 and 39 mm for M42×3.