A 1/2-inch Grade 8 bolt takes 106.4 ft·lbs (144.3 N·m) dry, or 79.8 ft·lbs oiled. Every size in the range is listed below — click a value for the full spec including all six surface conditions and fine-thread figures.
| Size | TPI (UNC) | ft·lbs (dry) | N·m (dry) | ft·lbs (oiled) |
|---|---|---|---|---|
| #6 | 32 | 1.9 | 2.6 | 1.4 |
| #8 | 32 | 3.4 | 4.6 | 2.6 |
| #10 | 24 | 5.0 | 6.8 | 3.7 |
| 1/4" | 20 | 11.9 | 16.1 | 8.9 |
| 5/16" | 18 | 24.6 | 33.4 | 18.4 |
| 3/8" | 16 | 43.6 | 59.1 | 32.7 |
| 7/16" | 14 | 69.8 | 94.6 | 52.3 |
| 1/2" | 13 | 106.4 | 144.3 | 79.8 |
| 9/16" | 12 | 153.6 | 208.3 | 115.2 |
| 5/8" | 11 | 211.9 | 287.3 | 158.9 |
| 3/4" | 10 | 375.8 | 509.5 | 281.8 |
| 7/8" | 9 | 606.4 | 822.2 | 454.8 |
| 1" | 8 | 909.0 | 1232.4 | 681.8 |
| 1-1/8" | 7 | 1287.6 | 1745.8 | 965.7 |
| 1-1/4" | 7 | 1816.9 | 2463.4 | 1362.7 |
| 1-3/8" | 6 | 2382.2 | 3229.8 | 1786.6 |
| 1-1/2" | 6 | 3161.3 | 4286.2 | 2370.9 |
Dry/plain steel, K = 0.20 · UNC coarse thread · Clamp load 75% of proof load · Click any ft·lbs value for full details
Identification: Six radial lines on the head. Head markings are the only reliable way to tell grades apart — plating and finish tell you nothing about strength.
Material and strength: Medium carbon alloy steel, quenched and tempered. Tensile strength 150,000 psi, proof load 120,000 psi per SAE J429.
Where it is used: High-stress joints — suspension, driveline, towing hardware, structural machinery connections.
Worth knowing: Grade 8 holds 150,000 psi tensile across the full size range, so torque scales smoothly with diameter with no strength step-down.
Every figure comes from T = K × D × F, where K is the nut factor (0.20 dry, 0.15 oiled), D is nominal diameter, and F is clamp load set at 75% of the bolt's proof load. Proof stress and tensile stress area come from SAE J429.
These are engineering reference values for a standard hex bolt in a steel joint. Where a manufacturer publishes a specific figure for an assembly, that figure takes precedence. Full methodology →
It depends on diameter. A 1/4-inch Grade 8 takes 11.9 ft·lbs, a 1/2-inch takes 106.4 ft·lbs, and a 3/4-inch takes 375.8 ft·lbs — all dry, plain steel, UNC coarse thread. The full table on this page covers #6 through 1-1/2 inch.
Six radial lines on the head. Head markings are the only reliable way to identify grade — never assume from appearance or plating.
Medium carbon alloy steel, quenched and tempered, with a tensile strength of 150,000 psi and a proof load of 120,000 psi per SAE J429.
Yes. Lubrication cuts the friction coefficient from about 0.20 to 0.15, so the same clamp load needs roughly 25% less torque. A 1/2-inch Grade 8 goes from 106.4 ft·lbs dry to 79.8 ft·lbs oiled.