1" 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 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 |
|---|---|---|---|---|
| 1-8 UNC Grade 2 | 187 ft-lb | 14,992 lbf | 19,990 lbf | |
| 1-8 UNC Grade 5 | 483 ft-lb | 38,616 lbf | 51,488 lbf | |
| 1-8 UNC Grade 8 | 681 ft-lb | 54,517 lbf | 72,689 lbf | |
| 1-12 UNF Grade 2 | 205 ft-lb | 16,410 lbf | 21,880 lbf | |
| 1-12 UNF Grade 5 | 528 ft-lb | 42,269 lbf | 56,359 lbf | |
| 1-12 UNF Grade 8 | 746 ft-lb | 59,674 lbf | 79,565 lbf |
Clamp load is 75 % of proof load. Dry: K = 0.20. Lubricated: K = 0.15.
1" 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 1-8 grade 5 figure, step by step.
- K
- 0.20, nut factor for dry plain steel
- F
- 38,616 lbf, 75 % of the 51,488 lbf proof load
- d
- 1.0000 in, nominal diameter
Where the inputs come from
Proof strength is taken from SAE J429: 33,000 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 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.