# 1 inch bolt torque

Tighten a 1-8 UNC grade 5 bolt to 644 ft-lb (873 N·m) with dry threads, or 483 ft-lb when lubricated. Grade 8 takes 909 ft-lb and grade 2 takes 250 ft-lb.

## 1 torque by thread series and SAE grade

| Thread | Grade | Dry torque (K 0.20) | Lubricated (K 0.15) | Clamp load |
|---|---|---|---|---|
| 1-8 UNC | Grade 2 | 250 ft-lb (339 N·m) | 187 ft-lb | 14,992 lbf |
| 1-8 UNC | Grade 5 | 644 ft-lb (873 N·m) | 483 ft-lb | 38,616 lbf |
| 1-8 UNC | Grade 8 | 909 ft-lb (1,232 N·m) | 681 ft-lb | 54,517 lbf |
| 1-12 UNF | Grade 2 | 274 ft-lb (371 N·m) | 205 ft-lb | 16,410 lbf |
| 1-12 UNF | Grade 5 | 704 ft-lb (955 N·m) | 528 ft-lb | 42,269 lbf |
| 1-12 UNF | Grade 8 | 995 ft-lb (1,348 N·m) | 746 ft-lb | 59,674 lbf |

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

## 1 bolt data

- Threads: 1-8 UNC, 1-12 UNF
- Wrench: 1-1/2 in
- Tap drill: 7/8 (0.8750 in) for UNC, 59/64 (0.9219 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 grade 5 bolt?**
About 644 ft-lb dry for 1-8 UNC and 704 ft-lb for 1-12 UNF, based on 75 % of proof load.

**What is the torque for a 1 grade 8 bolt?**
About 909 ft-lb dry for 1-8 UNC and 995 ft-lb for 1-12 UNF.

**What is the torque for a 1 grade 2 bolt?**
About 250 ft-lb dry for 1-8 UNC.

**What size wrench fits a 1 bolt?**
A standard 1" hex cap screw takes a 1-1/2" wrench or socket.

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