3/4 inch bolt torque
A 3/4-10 bolt takes 172 ft-lb in Grade 2, 266 in Grade 5 and 376 in Grade 8, dry, at 75% of proof load; the 3/4-16 fine thread takes 192, 297 and 420. Oiled threads take a quarter less.
Sources checked
| Thread | Grade | DryK 0.20 | Zinc platedK 0.20 | OiledK 0.15 | WaxedK 0.10 | Clamp load |
|---|---|---|---|---|---|---|
| 3/4-10UNC (coarse) | Grade 2 | 172233 | 172233 | 129175 | 86.1117 | 13,778 lbf61.3 kN |
| Grade 5 | 266361 | 266361 | 200271 | 133180 | 21,293 lbf94.7 kN | |
| Grade 8 | 376509 | 376509 | 282382 | 188255 | 30,060 lbf133.7 kN | |
| 3/4-16UNF (fine) | Grade 2 | 192261 | 192261 | 144196 | 96.2130 | 15,386 lbf68.4 kN |
| Grade 5 | 297403 | 297403 | 223302 | 149201 | 23,779 lbf105.8 kN | |
| Grade 8 | 420569 | 420569 | 315427 | 210284 | 33,570 lbf149.3 kN |
Work out 3/4 inch torque
Change grade, threads or preload
3/4-10 Grade 5, dry, plain steel
266ft-lb361N·m
- Clamp load
- 21,293 lbf (94.7 kN)
- Proof load
- 28,390 lbf
The working
- Tensile stress area. A = 0.7854 × (D − 0.9743 ÷ n)² = 0.7854 × (0.75 − 0.9743 ÷ 10)² = 0.334 in²
- Proof load. Grade 5 proof stress is 85,000 psi, so A × stress = 28,390 lbf.
- Clamp load. 75% of proof load = 21,293 lbf.
- Torque. T = K × D × F = 0.2 × 0.75 in × 21,293 lbf = 3,194 in-lb ÷ 12 = 266 ft-lb (361 N·m).
Where the 3/4-10 numbers come from
The 3/4-10 UNC (coarse) thread has a tensile stress area of 0.334 in². A Grade 8 bolt’s proof stress is 120,000 psi, so its proof load is 40,080 lbf, and 75% of that is a clamp load of 30,060 lbf.
Torque = K × D × F = 0.20 × 0.75 in × 30,060 lbf = 4,509 in-lb, or 376 ft-lb (509 N·m) dry. With oil (K 0.15) it’s 282 ft-lb (382 N·m).
Other sizes
All sizes on one page: the SAE bolt torque chart.
Questions
What torque for a 3/4-10 Grade 8 bolt?
376 ft-lb (509 N·m) dry and 282 ft-lb (382 N·m) oiled, at 75% of proof load. That clamps the joint with 30,060 lbf (133.7 kN).
What torque for a 3/4-10 Grade 5 bolt?
266 ft-lb (361 N·m) dry, at 75% of proof load; a quarter less with oiled threads.
Coarse or fine thread?
Use whichever the bolt has. The fine 3/4-16 thread has a bigger stress area than the coarse one, so it takes slightly more torque for the same clamp. A thread gauge settles it.
Does this apply to wheel nuts or engine bolts?
No. Use the vehicle maker’s value for those: see lug nut torque by vehicle. These numbers are for general-purpose steel bolts where no spec exists.
Sources
- Portland Bolt: SAE J429: proof load, yield and tensile strength for Grades 2, 5 and 8 (checked October 14, 2026)
- Portland Bolt: Thread pitch chart: UNC and UNF threads per inch and tensile stress areas (checked October 14, 2026)
- Fastenal: Mechanical properties of inch fasteners, with UNC and UNF tensile stress areas (checked October 14, 2026)
- Engineering Toolbox: Threaded bolts: tensile stress area formulas for unified and ISO metric threads (checked October 14, 2026)
- Fastenal: Torque–tension relationship for A307 A, Grade 5, 8 and 9 coarse thread bolts (75% of proof load; K 0.15 and 0.20) (checked October 14, 2026)
- Portland Bolt: Bolt torque chart: T = KDP at 75% of proof load, with K for plain, waxed and galvanized bolts (checked October 14, 2026)
Spotted a number that doesn’t match your manual or a source? Tell us; corrections are logged on the sources page.