M33 Bolt Torque
An M33 8.8 bolt with a coarse M33×3.5 thread needs about 1968.2 N·m (1451.6 ft·lb) when dry and 1458.5 N·m (1075.7 ft·lb) when oiled, tightened to 70% of yield (clamp force 310.7 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 116.5 kN26194 lbf | 738.1 N·m544.4 ft·lb | 546.9 N·m403.4 ft·lb | 355.8 N·m262.4 ft·lb |
| 4.8 | 155.4 kN34925 lbf | 984.1 N·m725.8 ft·lb | 729.2 N·m537.9 ft·lb | 474.4 N·m349.9 ft·lb |
| 5.6 | 145.6 kN32743 lbf | 922.6 N·m680.5 ft·lb | 683.7 N·m504.2 ft·lb | 444.7 N·m328.0 ft·lb |
| 5.8 | 194.2 kN43657 lbf | 1230.1 N·m907.3 ft·lb | 911.5 N·m672.3 ft·lb | 593.0 N·m437.4 ft·lb |
| 6.8 | 233.0 kN52388 lbf | 1476.1 N·m1088.7 ft·lb | 1093.8 N·m806.8 ft·lb | 711.6 N·m524.8 ft·lb |
| 8.8 | 310.7 kN69851 lbf | 1968.2 N·m1451.6 ft·lb | 1458.5 N·m1075.7 ft·lb | 948.8 N·m699.8 ft·lb |
| 10.9 | 436.9 kN98228 lbf | 2767.7 N·m2041.4 ft·lb | 2051.0 N·m1512.7 ft·lb | 1334.2 N·m984.0 ft·lb |
| 12.9 | 524.3 kN117873 lbf | 3321.3 N·m2449.7 ft·lb | 2461.2 N·m1815.3 ft·lb | 1601.0 N·m1180.9 ft·lb |
| A2-70 | 218.5 kN49114 lbf | 1383.9 N·m1020.7 ft·lb | 1025.5 N·m756.4 ft·lb | 667.1 N·m492.0 ft·lb |
| A4-70 | 218.5 kN49114 lbf | 1383.9 N·m1020.7 ft·lb | 1025.5 N·m756.4 ft·lb | 667.1 N·m492.0 ft·lb |
| A4-80 | 291.3 kN65485 lbf | 1845.2 N·m1360.9 ft·lb | 1367.3 N·m1008.5 ft·lb | 889.5 N·m656.0 ft·lb |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 127.8 kN28734 lbf | 789.6 N·m582.3 ft·lb | 576.9 N·m425.5 ft·lb | 364.2 N·m268.6 ft·lb |
| 4.8 | 170.4 kN38312 lbf | 1052.7 N·m776.5 ft·lb | 769.2 N·m567.3 ft·lb | 485.6 N·m358.1 ft·lb |
| 5.6 | 159.8 kN35917 lbf | 986.9 N·m727.9 ft·lb | 721.1 N·m531.8 ft·lb | 455.2 N·m335.8 ft·lb |
| 5.8 | 213.0 kN47890 lbf | 1315.9 N·m970.6 ft·lb | 961.5 N·m709.1 ft·lb | 607.0 N·m447.7 ft·lb |
| 6.8 | 255.6 kN57468 lbf | 1579.1 N·m1164.7 ft·lb | 1153.7 N·m851.0 ft·lb | 728.4 N·m537.2 ft·lb |
| 8.8 | 340.8 kN76623 lbf | 2105.5 N·m1552.9 ft·lb | 1538.3 N·m1134.6 ft·lb | 971.2 N·m716.3 ft·lb |
| 10.9 | 479.3 kN107752 lbf | 2960.8 N·m2183.8 ft·lb | 2163.3 N·m1595.5 ft·lb | 1365.7 N·m1007.3 ft·lb |
| 12.9 | 575.2 kN129302 lbf | 3553.0 N·m2620.6 ft·lb | 2595.9 N·m1914.7 ft·lb | 1638.8 N·m1208.7 ft·lb |
| A2-70 | 239.7 kN53876 lbf | 1480.4 N·m1091.9 ft·lb | 1081.6 N·m797.8 ft·lb | 682.8 N·m503.6 ft·lb |
| A4-70 | 239.7 kN53876 lbf | 1480.4 N·m1091.9 ft·lb | 1081.6 N·m797.8 ft·lb | 682.8 N·m503.6 ft·lb |
| A4-80 | 319.5 kN71834 lbf | 1973.9 N·m1455.9 ft·lb | 1442.2 N·m1063.7 ft·lb | 910.5 N·m671.5 ft·lb |
Torque for M33 hex head bolts and nuts, standard ISO/ASME heads on steel with a 36.0 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
M33 thread and dimensions
- Coarse thread
- M33×3.5 — pitch 3.5 mm
- Fine thread
- M33×2 — pitch 2 mm
- Tensile stress area Aₛ
- 693.6 mm² (coarse), 760.8 mm² (fine)
- Pitch diameter d₂
- 30.727 mm
- Tap drill
- 29.5 mm (coarse), 31 mm (fine)
- Wrench size (hex head)
- 50 mm
- Clearance hole
- 36.0 mm
How the M33 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 × 693.6 mm² = 310.7 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 310.7 kN × (0.16·3.5 + 0.58·0.15·30.73 + 0.15·43.00/2) mm = 1968.2 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (43.00 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for an M33 8.8 bolt?
About 1968.2 N·m (1451.6 ft·lb) with dry threads, 1458.5 N·m (1075.7 ft·lb) with oiled threads and 948.8 N·m (699.8 ft·lb) with PTFE or moly paste, for a coarse M33×3.5 thread tightened to 70% of yield. The resulting clamp force is 310.7 kN.
What is the torque for an M33 10.9 bolt?
About 2767.7 N·m (2041.4 ft·lb) with dry threads, 2051.0 N·m (1512.7 ft·lb) with oiled threads and 1334.2 N·m (984.0 ft·lb) with PTFE or moly paste, for a coarse M33×3.5 thread tightened to 70% of yield. The resulting clamp force is 436.9 kN.
What size wrench fits an M33 bolt?
A standard M33 hex head bolt or nut takes a 50 mm wrench or socket.
What drill size do I need to tap M33?
Use a 29.5 mm drill for M33×3.5 and 31 mm for M33×2.