# 1/4 inch bolt torque

Tighten a 1/4-20 UNC grade 5 bolt to 8.5 ft-lb (11 N·m) with dry threads, or 6.3 ft-lb when lubricated. Grade 8 takes 12 ft-lb and grade 2 takes 5.5 ft-lb.

## 1/4 torque by thread series and SAE grade

| Thread | Grade | Dry torque (K 0.20) | Lubricated (K 0.15) | Clamp load |
|---|---|---|---|---|
| 1/4-20 UNC | Grade 2 | 5.5 ft-lb (7.4 N·m) | 4.1 ft-lb | 1,313 lbf |
| 1/4-20 UNC | Grade 5 | 8.5 ft-lb (11 N·m) | 6.3 ft-lb | 2,029 lbf |
| 1/4-20 UNC | Grade 8 | 12 ft-lb (16 N·m) | 8.9 ft-lb | 2,864 lbf |
| 1/4-28 UNF | Grade 2 | 6.3 ft-lb (8.5 N·m) | 4.7 ft-lb | 1,500 lbf |
| 1/4-28 UNF | Grade 5 | 9.7 ft-lb (13 N·m) | 7.2 ft-lb | 2,319 lbf |
| 1/4-28 UNF | Grade 8 | 14 ft-lb (18 N·m) | 10 ft-lb | 3,274 lbf |

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

## 1/4 bolt data

- Threads: 1/4-20 UNC, 1/4-28 UNF
- Wrench: 7/16 in
- Tap drill: #7 (0.2010 in) for UNC, #3 (0.2130 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 1/4 grade 5 bolt?**
About 8.5 ft-lb dry for 1/4-20 UNC and 9.7 ft-lb for 1/4-28 UNF, based on 75 % of proof load.

**What is the torque for a 1/4 grade 8 bolt?**
About 12 ft-lb dry for 1/4-20 UNC and 14 ft-lb for 1/4-28 UNF.

**What is the torque for a 1/4 grade 2 bolt?**
About 5.5 ft-lb dry for 1/4-20 UNC.

**What size wrench fits a 1/4 bolt?**
A standard 1/4" hex cap screw takes a 7/16" wrench or socket.

Source page: https://machinistcharts.com/bolt-torque/1-4-inch/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)