# 3/8 inch bolt torque

Tighten a 3/8-16 UNC grade 5 bolt to 31 ft-lb (42 N·m) with dry threads, or 23 ft-lb when lubricated. Grade 8 takes 44 ft-lb and grade 2 takes 20 ft-lb.

## 3/8 torque by thread series and SAE grade

| Thread | Grade | Dry torque (K 0.20) | Lubricated (K 0.15) | Clamp load |
|---|---|---|---|---|
| 3/8-16 UNC | Grade 2 | 20 ft-lb (27 N·m) | 15 ft-lb | 3,196 lbf |
| 3/8-16 UNC | Grade 5 | 31 ft-lb (42 N·m) | 23 ft-lb | 4,940 lbf |
| 3/8-16 UNC | Grade 8 | 44 ft-lb (59 N·m) | 33 ft-lb | 6,974 lbf |
| 3/8-24 UNF | Grade 2 | 23 ft-lb (31 N·m) | 17 ft-lb | 3,623 lbf |
| 3/8-24 UNF | Grade 5 | 35 ft-lb (47 N·m) | 26 ft-lb | 5,599 lbf |
| 3/8-24 UNF | Grade 8 | 49 ft-lb (67 N·m) | 37 ft-lb | 7,905 lbf |

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

## 3/8 bolt data

- Threads: 3/8-16 UNC, 3/8-24 UNF
- Wrench: 9/16 in
- Tap drill: 5/16 (0.3125 in) for UNC, Q (0.3320 in) for UNF

## Method

Proof strength from SAE J429 × tensile stress area As = 0.7854 × (D − 0.9743/n)² (ASME B1.1). F = 75 % of proof load. T = K × F × D with K = 0.20 dry, 0.15 lubricated.

## FAQ

**What is the torque for a 3/8 grade 5 bolt?**
About 31 ft-lb dry for 3/8-16 UNC and 35 ft-lb for 3/8-24 UNF, based on 75 % of proof load.

**What is the torque for a 3/8 grade 8 bolt?**
About 44 ft-lb dry for 3/8-16 UNC and 49 ft-lb for 3/8-24 UNF.

**What is the torque for a 3/8 grade 2 bolt?**
About 20 ft-lb dry for 3/8-16 UNC.

**What size wrench fits a 3/8 bolt?**
A standard 3/8" hex cap screw takes a 9/16" wrench or socket.

Source page: https://machinistcharts.com/bolt-torque/3-8-inch/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)