# M27 bolt torque

Tighten an M27 × 3 class 8.8 bolt to 1,116 N·m (823 ft-lb) with dry threads, or 837 N·m when lubricated. Class 10.9 takes 1,544 N·m and class 12.9 takes 1,805 N·m.

## M27 × 3 torque by property class

| Property class | Dry torque (K 0.20) | Lubricated (K 0.15) | Clamp load | Proof load |
|---|---|---|---|---|
| Class 8.8 | 1,116 N·m (823 ft-lb) | 837 N·m (618 ft-lb) | 206.7 kN | 275.6 kN |
| Class 10.9 | 1,544 N·m (1,139 ft-lb) | 1,158 N·m (854 ft-lb) | 286.0 kN | 381.3 kN |
| Class 12.9 | 1,805 N·m (1,331 ft-lb) | 1,354 N·m (998 ft-lb) | 334.2 kN | 445.6 kN |

Clamp load = 75 % of proof load. Method: T = K × F × d.

## M27 bolt data

- Thread: M27 × 3 coarse
- Tensile stress area: 459.4 mm²
- Wrench: 41 mm (ISO 4014/4017)
- Socket head cap screw hex key: 19 mm
- Tap drill: 24 mm
- Clearance hole (ISO 273): 28 close, 30 normal, 32 loose (mm)

## Method

Proof stress from ISO 898-1 (600 MPa for 8.8 at this size, 830 MPa for 10.9, 970 MPa for 12.9) × tensile stress area As = π/4 × (d − 0.9382 p)². Target clamp load F = 75 % of proof load. T = K × F × d with K = 0.20 dry, 0.15 lubricated.

## FAQ

**What is the torque for an M27 8.8 bolt?**
About 1,116 N·m (823 ft-lb) with dry threads and about 837 N·m lubricated, based on 75 % of proof load.

**What is the torque for an M27 10.9 bolt?**
About 1,544 N·m (1,139 ft-lb) dry and 1,158 N·m lubricated.

**What is the torque for an M27 12.9 bolt?**
About 1,805 N·m (1,331 ft-lb) dry and 1,354 N·m lubricated.

**What size wrench fits an M27 bolt?**
41 mm for ISO hex bolts. An M27 socket head cap screw takes a 19 mm hex key.

**What drill size do I need to tap M27?**
Use a 24 mm drill for M27 × 3 coarse thread.

Source page: https://machinistcharts.com/bolt-torque/m27/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)