3/4" bolt torque
Tighten a 3/4-10 UNC grade 5 bolt to 267 ft-lb (361 N·m) with dry threads, or 200 ft-lb when lubricated. Grade 8 takes 376 ft-lb and grade 2 takes 172 ft-lb.
3/4" torque by thread and grade
Tap a row to show it on the dial. The unit switch above changes every value on this page.
| Thread and grade | Dry torque | Lubricated | Clamp load | Proof load |
|---|---|---|---|---|
| 3/4-10 UNC Grade 2 | 129 ft-lb | 13,797 lbf | 18,395 lbf | |
| 3/4-10 UNC Grade 5 | 200 ft-lb | 21,322 lbf | 28,429 lbf | |
| 3/4-10 UNC Grade 8 | 282 ft-lb | 30,101 lbf | 40,135 lbf | |
| 3/4-16 UNF Grade 2 | 144 ft-lb | 15,385 lbf | 20,513 lbf | |
| 3/4-16 UNF Grade 5 | 223 ft-lb | 23,776 lbf | 31,702 lbf | |
| 3/4-16 UNF Grade 8 | 315 ft-lb | 33,566 lbf | 44,755 lbf |
Clamp load is 75 % of proof load. Dry: K = 0.20. Lubricated: K = 0.15.
3/4" at a glance
Wrench, drill and thread data for the same bolt.
Before you tighten
Lubricant changes the number
Oil, moly paste or anti-seize lowers the nut factor K, so the same torque produces far more clamp load. Use the lubricated value whenever the threads are oiled, or the bolt can yield.
Tighten in a star pattern
On flanges and covers, bring every bolt to about 30 %, then 70 %, then full torque, crossing the pattern each pass. Finish with one round at full torque in sequence.
Give the thread enough grip
Engage at least one diameter of thread in steel, about 1.5 diameters in cast iron and 2 diameters in aluminium, or the internal thread strips before the bolt reaches its clamp load.
How the number is worked out
The 3/4-10 grade 5 figure, step by step.
- K
- 0.20, nut factor for dry plain steel
- F
- 21,322 lbf, 75 % of the 28,429 lbf proof load
- d
- 0.7500 in, nominal diameter
Where the inputs come from
Proof strength is taken from SAE J429: 55,000 psi for grade 2 at this size, 85,000 psi for grade 5 and 120,000 psi for grade 8. Multiply by the tensile stress area to get the proof load.
The stress area comes from ASME B1.1: As = 0.7854 × (D − 0.9743 / n)². Target clamp load is 75 % of proof load.
Lubricated values use K = 0.15. For other coatings or preload targets, use the torque calculator.
Other inch sizes
Common questions
What is the torque for a 3/4 grade 5 bolt?
About 267 ft-lb dry for 3/4-10 UNC and 297 ft-lb for 3/4-16 UNF, based on 75 % of proof load.
What is the torque for a 3/4 grade 8 bolt?
About 376 ft-lb dry for 3/4-10 UNC and 420 ft-lb for 3/4-16 UNF.
What is the torque for a 3/4 grade 2 bolt?
About 172 ft-lb dry for 3/4-10 UNC.
What size wrench fits a 3/4 bolt?
A standard 3/4" hex cap screw takes a 1-1/8" wrench or socket.