# M4 bolt torque

Tighten an M4 × 0.7 class 8.8 bolt to 3.1 N·m (2.3 ft-lb) with dry threads, or 2.3 N·m when lubricated. Class 10.9 takes 4.4 N·m and class 12.9 takes 5.1 N·m.

## M4 × 0.7 torque by property class

| Property class | Dry torque (K 0.20) | Lubricated (K 0.15) | Clamp load | Proof load |
|---|---|---|---|---|
| Class 8.8 | 3.1 N·m (2.3 ft-lb) | 2.3 N·m (1.7 ft-lb) | 3.8 kN | 5.1 kN |
| Class 10.9 | 4.4 N·m (3.2 ft-lb) | 3.3 N·m (2.4 ft-lb) | 5.5 kN | 7.3 kN |
| Class 12.9 | 5.1 N·m (3.8 ft-lb) | 3.8 N·m (2.8 ft-lb) | 6.4 kN | 8.5 kN |

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

## M4 bolt data

- Thread: M4 × 0.7 coarse
- Tensile stress area: 8.8 mm²
- Wrench: 7 mm (ISO 4014/4017)
- Socket head cap screw hex key: 3 mm
- Tap drill: 3.3 mm
- Clearance hole (ISO 273): 4.3 close, 4.5 normal, 4.8 loose (mm)

## Method

Proof stress from ISO 898-1 (580 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 M4 8.8 bolt?**
About 3.1 N·m (2.3 ft-lb) with dry threads and about 2.3 N·m lubricated, based on 75 % of proof load.

**What is the torque for an M4 10.9 bolt?**
About 4.4 N·m (3.2 ft-lb) dry and 3.3 N·m lubricated.

**What is the torque for an M4 12.9 bolt?**
About 5.1 N·m (3.8 ft-lb) dry and 3.8 N·m lubricated.

**What size wrench fits an M4 bolt?**
7 mm for ISO hex bolts. An M4 socket head cap screw takes a 3 mm hex key.

**What drill size do I need to tap M4?**
Use a 3.3 mm drill for M4 × 0.7 coarse thread.

Source page: https://machinistcharts.com/bolt-torque/m4/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)