Bolt Torque Tables
Recommended tightening torques for common bolt sizes and grades (4.6, 8.8, 10.9, 12.9, A2-70, A4-80). Essential for flange assembly and mechanical connections.
Torque for Grade 8.8 Steel Bolts (Dry)
| Size | Torque (Nm) | Clamp force (kN) |
|---|---|---|
| M6 | 10 | 6.4 |
| M8 | 25 | 11.6 |
| M10 | 49 | 18.4 |
| M12 | 86 | 26.8 |
| M16 | 211 | 49.9 |
| M20 | 411 | 77.8 |
| M24 | 710 | 112 |
| M30 | 1430 | 180 |
| M36 | 2478 | 262 |
Torque for Grade 10.9 Steel Bolts (Dry)
| Size | Torque (Nm) | Clamp force (kN) |
|---|---|---|
| M6 | 13 | 8.0 |
| M8 | 32 | 14.6 |
| M10 | 62 | 23.1 |
| M12 | 109 | 33.6 |
| M16 | 266 | 62.4 |
| M20 | 517 | 97.2 |
| M24 | 890 | 140 |
| M30 | 1790 | 225 |
| M36 | 3100 | 327 |
Torque for Stainless Steel A2-70 (Dry)
| Size | Torque (Nm) | |
|---|---|---|
| M6 | 6 | — |
| M8 | 15 | — |
| M10 | 30 | — |
| M12 | 52 | — |
| M16 | 128 | — |
| M20 | 249 | — |
| M24 | 430 | — |
Lubrication affects torque
The torque values above are for dry, unlubricated bolts. If the threads are lubricated (oil, anti-seize, grease), the friction coefficient drops and the same torque produces 20–40% more clamping force. Reduce the torque by approximately 25% for lubricated bolts, or use the manufacturer's lubricated torque values.
Flange Bolt Tightening Sequence
Always tighten flange bolts in a crisscross (star) pattern:
1. Tighten all bolts finger-tight.
2. Tighten to 30% of final torque in a crisscross pattern.
3. Tighten to 60% of final torque.
4. Tighten to 100% of final torque.
5. Do a final pass at 100% torque clockwise.
This ensures the gasket compresses evenly and prevents leaks.
How CHI can help
Ask CHI about bolt torque values and to recommend the correct tightening sequence for your flange assembly. The CHI assistant can look up specific values, explain what each table entry means, and help you cross-reference between different standards and unit systems.