M27 bolt torque
An M27 x 3 bolt takes 1,115 N·m in class 8.8, 1,543 in 10.9 and 1,803 in 12.9, dry, at 75% of proof load (823, 1138 and 1330 ft-lb). Fine pitches take a little more. Oiled threads take a quarter less.
Sources checked
| Thread | Class | DryK 0.20 | Zinc platedK 0.20 | OiledK 0.15 | WaxedK 0.10 | Clamp load |
|---|---|---|---|---|---|---|
| M27 x 3coarse | Class 4.6 | 308418 | 308418 | 231314 | 154209 | 17,413 lbf77.5 kN |
| Class 8.8 | 8231,115 | 8231,115 | 617837 | 411558 | 46,434 lbf206.6 kN | |
| Class 10.9 | 1,1381,543 | 1,1381,543 | 8541,157 | 569771 | 64,234 lbf285.7 kN | |
| Class 12.9 | 1,3301,803 | 1,3301,803 | 9971,352 | 665902 | 75,069 lbf333.9 kN | |
| M27 x 2fine | Class 4.6 | 333452 | 333452 | 250339 | 167226 | 18,817 lbf83.7 kN |
| Class 8.8 | 8891,205 | 8891,205 | 667904 | 444603 | 50,177 lbf223.2 kN | |
| Class 10.9 | 1,2301,667 | 1,2301,667 | 9221,250 | 615834 | 69,412 lbf308.8 kN | |
| Class 12.9 | 1,4371,949 | 1,4371,949 | 1,0781,461 | 719974 | 81,120 lbf360.8 kN |
Work out M27 torque
Change grade, threads or preload
M27 x 3 Class 8.8, dry, plain steel
823ft-lb1,115N·m
- Clamp load
- 46,434 lbf (206.6 kN)
- Proof load
- 275.4 kN
The working
- Tensile stress area. A = π/4 × (d − 0.9382 × P)² = π/4 × (27 − 0.9382 × 3)² = 459 mm²
- Proof load. Class 8.8 proof stress is 600 MPa, so A × stress = 275,400 N.
- Clamp load. 75% of proof load = 206,550 N.
- Torque. T = K × D × F = 0.2 × 27 mm × 206.55 kN = 1,115 N·m (823 ft-lb).
Where the M27 x 3 numbers come from
The M27 x 3 coarse thread has a tensile stress area of 459 mm². A Class 10.9 bolt’s proof stress is 830 MPa, so its proof load is 380,970 N, and 75% of that is a clamp load of 285,728 N.
Torque = K × D × F = 0.20 × 27 mm × 285.73 kN = 1,543 N·m (1,138 ft-lb) dry. With oil (K 0.15) it’s 1,157 N·m (854 ft-lb).
Other sizes
All sizes on one page: the metric bolt torque chart.
Questions
What torque for an M27 x 3 Class 10.9 bolt?
1,543 N·m (1,138 ft-lb) dry and 1,157 N·m (854 ft-lb) oiled, at 75% of proof load. That clamps the joint with 64,234 lbf (285.7 kN).
What torque for an M27 x 3 Class 8.8 bolt?
1,115 N·m (823 ft-lb) dry, at 75% of proof load; a quarter less with oiled threads.
Coarse or fine thread?
Use whichever the bolt has. The fine M27 x 2 thread has a bigger stress area than the coarse one, so it takes slightly more torque for the same clamp. A thread gauge settles it.
Does this apply to wheel nuts or engine bolts?
No. Use the vehicle maker’s value for those: see lug nut torque by vehicle. These numbers are for general-purpose steel bolts where no spec exists.
Sources
- Fastenal: Mechanical properties per ISO 898-1 (externally threaded fasteners): proof stress by property class (checked October 14, 2026)
- Engineering Toolbox: Metric bolts: minimum ultimate tensile and proof loads, with ISO 898-1 stress areas (checked October 14, 2026)
- Engineering Toolbox: ISO 724 metric threads: coarse and fine pitches with tensile stress areas (checked October 14, 2026)
- Engineering Toolbox: Threaded bolts: tensile stress area formulas for unified and ISO metric threads (checked October 14, 2026)
- Fastenal: Torque–tension relationship for metric fasteners, property classes 4.6, 8.8, 10.9 and 12.9 (checked October 14, 2026)
- Portland Bolt: Bolt torque chart: T = KDP at 75% of proof load, with K for plain, waxed and galvanized bolts (checked October 14, 2026)
Spotted a number that doesn’t match your manual or a source? Tell us; corrections are logged on the sources page.