M2 Bolt Torque
An M2 8.8 bolt with a coarse M2×0.4 thread needs about 0.42 N·m (0.31 ft·lb) when dry and 0.31 N·m (0.23 ft·lb) when oiled, tightened to 70% of yield (clamp force 0.93 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 0.35 kN78 lbf | 0.16 N·m0.11 ft·lb | 0.12 N·m0.09 ft·lb | 0.08 N·m0.06 ft·lb |
| 4.8 | 0.46 kN104 lbf | 0.21 N·m0.15 ft·lb | 0.16 N·m0.12 ft·lb | 0.11 N·m0.08 ft·lb |
| 5.6 | 0.44 kN98 lbf | 0.19 N·m0.14 ft·lb | 0.15 N·m0.11 ft·lb | 0.10 N·m0.07 ft·lb |
| 5.8 | 0.58 kN131 lbf | 0.26 N·m0.19 ft·lb | 0.20 N·m0.14 ft·lb | 0.13 N·m0.10 ft·lb |
| 6.8 | 0.70 kN157 lbf | 0.31 N·m0.23 ft·lb | 0.24 N·m0.17 ft·lb | 0.16 N·m0.12 ft·lb |
| 8.8 | 0.93 kN209 lbf | 0.42 N·m0.31 ft·lb | 0.31 N·m0.23 ft·lb | 0.21 N·m0.16 ft·lb |
| 9.8 | 1.04 kN235 lbf | 0.47 N·m0.34 ft·lb | 0.35 N·m0.26 ft·lb | 0.24 N·m0.18 ft·lb |
| 10.9 | 1.31 kN294 lbf | 0.58 N·m0.43 ft·lb | 0.44 N·m0.33 ft·lb | 0.30 N·m0.22 ft·lb |
| 12.9 | 1.57 kN352 lbf | 0.70 N·m0.52 ft·lb | 0.53 N·m0.39 ft·lb | 0.36 N·m0.27 ft·lb |
| A2-70 | 0.65 kN147 lbf | 0.29 N·m0.22 ft·lb | 0.22 N·m0.16 ft·lb | 0.15 N·m0.11 ft·lb |
| A4-70 | 0.65 kN147 lbf | 0.29 N·m0.22 ft·lb | 0.22 N·m0.16 ft·lb | 0.15 N·m0.11 ft·lb |
| A4-80 | 0.87 kN196 lbf | 0.39 N·m0.29 ft·lb | 0.29 N·m0.22 ft·lb | 0.20 N·m0.15 ft·lb |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 0.41 kN92 lbf | 0.18 N·m0.13 ft·lb | 0.13 N·m0.10 ft·lb | 0.09 N·m0.06 ft·lb |
| 4.8 | 0.55 kN123 lbf | 0.24 N·m0.17 ft·lb | 0.18 N·m0.13 ft·lb | 0.11 N·m0.08 ft·lb |
| 5.6 | 0.51 kN116 lbf | 0.22 N·m0.16 ft·lb | 0.16 N·m0.12 ft·lb | 0.11 N·m0.08 ft·lb |
| 5.8 | 0.69 kN154 lbf | 0.30 N·m0.22 ft·lb | 0.22 N·m0.16 ft·lb | 0.14 N·m0.11 ft·lb |
| 6.8 | 0.82 kN185 lbf | 0.35 N·m0.26 ft·lb | 0.26 N·m0.19 ft·lb | 0.17 N·m0.13 ft·lb |
| 8.8 | 1.10 kN247 lbf | 0.47 N·m0.35 ft·lb | 0.35 N·m0.26 ft·lb | 0.23 N·m0.17 ft·lb |
| 9.8 | 1.23 kN277 lbf | 0.53 N·m0.39 ft·lb | 0.40 N·m0.29 ft·lb | 0.26 N·m0.19 ft·lb |
| 10.9 | 1.54 kN347 lbf | 0.67 N·m0.49 ft·lb | 0.49 N·m0.36 ft·lb | 0.32 N·m0.24 ft·lb |
| 12.9 | 1.85 kN416 lbf | 0.80 N·m0.59 ft·lb | 0.59 N·m0.44 ft·lb | 0.39 N·m0.29 ft·lb |
| A2-70 | 0.77 kN173 lbf | 0.33 N·m0.25 ft·lb | 0.25 N·m0.18 ft·lb | 0.16 N·m0.12 ft·lb |
| A4-70 | 0.77 kN173 lbf | 0.33 N·m0.25 ft·lb | 0.25 N·m0.18 ft·lb | 0.16 N·m0.12 ft·lb |
| A4-80 | 1.03 kN231 lbf | 0.44 N·m0.33 ft·lb | 0.33 N·m0.24 ft·lb | 0.21 N·m0.16 ft·lb |
Torque for M2 hex head bolts and nuts, standard ISO/ASME heads on steel with a 2.4 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
M2 thread and dimensions
- Coarse thread
- M2×0.4 — pitch 0.4 mm
- Fine thread
- M2×0.25 — pitch 0.25 mm
- Tensile stress area Aₛ
- 2.07 mm² (coarse), 2.45 mm² (fine)
- Pitch diameter d₂
- 1.740 mm
- Tap drill
- 1.6 mm (coarse), 1.75 mm (fine)
- Wrench size (hex head)
- 4 mm
- Clearance hole
- 2.4 mm
How the M2 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 × 2.07 mm² = 0.93 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 0.93 kN × (0.16·0.4 + 0.58·0.15·1.74 + 0.15·3.20/2) mm = 0.42 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (3.20 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for an M2 8.8 bolt?
About 0.42 N·m (0.31 ft·lb) with dry threads, 0.31 N·m (0.23 ft·lb) with oiled threads and 0.21 N·m (0.16 ft·lb) with PTFE or moly paste, for a coarse M2×0.4 thread tightened to 70% of yield. The resulting clamp force is 0.93 kN.
What is the torque for an M2 10.9 bolt?
About 0.58 N·m (0.43 ft·lb) with dry threads, 0.44 N·m (0.33 ft·lb) with oiled threads and 0.30 N·m (0.22 ft·lb) with PTFE or moly paste, for a coarse M2×0.4 thread tightened to 70% of yield. The resulting clamp force is 1.31 kN.
What size wrench fits an M2 bolt?
A standard M2 hex head bolt or nut takes a 4 mm wrench or socket.
What drill size do I need to tap M2?
Use a 1.6 mm drill for M2×0.4 and 1.75 mm for M2×0.25.