3/4" Bolt Torque
A 3/4" Grade 5 bolt with a coarse 3/4"-10 UNC thread needs about 261.0 ft·lb (353.9 N·m) when dry and 195.0 ft·lb (264.4 N·m) when oiled, tightened to 70% of yield (clamp force 95.8 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| Grade 2 | 59.4 kN13345 lbf | 161.8 ft·lb219.3 N·m | 120.9 ft·lb163.9 N·m | 80.0 ft·lb108.4 N·m |
| Grade 5 | 95.8 kN21528 lbf | 261.0 ft·lb353.9 N·m | 195.0 ft·lb264.4 N·m | 129.0 ft·lb174.9 N·m |
| Grade 8 | 135.3 kN30425 lbf | 368.9 ft·lb500.1 N·m | 275.6 ft·lb373.6 N·m | 182.3 ft·lb247.2 N·m |
| A307 | 37.8 kN8489 lbf | 102.9 ft·lb139.5 N·m | 76.9 ft·lb104.3 N·m | 50.9 ft·lb69.0 N·m |
| A325 | 95.8 kN21528 lbf | 261.0 ft·lb353.9 N·m | 195.0 ft·lb264.4 N·m | 129.0 ft·lb174.9 N·m |
| A490 | 135.3 kN30425 lbf | 368.9 ft·lb500.1 N·m | 275.6 ft·lb373.6 N·m | 182.3 ft·lb247.2 N·m |
| A574 | 156.2 kN35111 lbf | 425.7 ft·lb577.1 N·m | 318.0 ft·lb431.2 N·m | 210.4 ft·lb285.3 N·m |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| Grade 2 | 66.2 kN14881 lbf | 175.5 ft·lb238.0 N·m | 129.2 ft·lb175.2 N·m | 82.8 ft·lb112.3 N·m |
| Grade 5 | 106.8 kN24007 lbf | 283.2 ft·lb383.9 N·m | 208.4 ft·lb282.6 N·m | 133.7 ft·lb181.2 N·m |
| Grade 8 | 150.9 kN33927 lbf | 400.2 ft·lb542.6 N·m | 294.5 ft·lb399.4 N·m | 188.9 ft·lb256.1 N·m |
| A307 | 42.1 kN9466 lbf | 111.7 ft·lb151.4 N·m | 82.2 ft·lb111.4 N·m | 52.7 ft·lb71.5 N·m |
| A325 | 106.8 kN24007 lbf | 283.2 ft·lb383.9 N·m | 208.4 ft·lb282.6 N·m | 133.7 ft·lb181.2 N·m |
| A490 | 150.9 kN33927 lbf | 400.2 ft·lb542.6 N·m | 294.5 ft·lb399.4 N·m | 188.9 ft·lb256.1 N·m |
| A574 | 174.2 kN39153 lbf | 461.9 ft·lb626.2 N·m | 339.9 ft·lb460.9 N·m | 218.0 ft·lb295.5 N·m |
Torque for 3/4" hex head bolts and nuts, standard ISO/ASME heads on steel with a 20.6 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
3/4" thread and dimensions
- Coarse thread
- 3/4"-10 UNC — pitch 10 TPI
- Fine thread
- 3/4"-16 UNF — pitch 16 TPI
- Tensile stress area Aₛ
- 215.8 mm² (coarse), 240.6 mm² (fine)
- Pitch diameter d₂
- 17.400 mm
- Tap drill
- 21/32 (coarse), 11/16 (fine)
- Wrench size (hex head)
- 1-1/8"
- Clearance hole
- 20.6 mm
How the 3/4" torque is calculated
Preload is 70% of the bolt's yield strength times its tensile stress area. Torque then follows the ISO 16047 / VDI 2230 formula, which splits it into thread pitch, thread friction and friction under the head:
F = 70% × 634 MPa × 215.8 mm² = 95.8 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 95.8 kN × (0.16·2.54 + 0.58·0.15·17.40 + 0.15·24.61/2) mm = 353.9 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (24.61 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for a 3/4" Grade 5 bolt?
About 261.0 ft·lb (353.9 N·m) with dry threads, 195.0 ft·lb (264.4 N·m) with oiled threads and 129.0 ft·lb (174.9 N·m) with PTFE or moly paste, for a coarse 3/4"-10 UNC thread tightened to 70% of yield. The resulting clamp force is 95.8 kN.
What is the torque for a 3/4" Grade 8 bolt?
About 368.9 ft·lb (500.1 N·m) with dry threads, 275.6 ft·lb (373.6 N·m) with oiled threads and 182.3 ft·lb (247.2 N·m) with PTFE or moly paste, for a coarse 3/4"-10 UNC thread tightened to 70% of yield. The resulting clamp force is 135.3 kN.
What size wrench fits a 3/4" bolt?
A standard 3/4" hex head bolt or nut takes a 1-1/8" wrench or socket.
What drill size do I need to tap 3/4"?
Use a 21/32 drill for 3/4"-10 UNC and 11/16 for 3/4"-16 UNF.