1" Bolt Torque
A 1" Grade 5 bolt with a coarse 1"-8 UNC thread needs about 624.9 ft·lb (847.3 N·m) when dry and 465.9 ft·lb (631.6 N·m) when oiled, tightened to 70% of yield (clamp force 173.4 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| Grade 2 | 67.8 kN15252 lbf | 244.5 ft·lb331.4 N·m | 182.2 ft·lb247.1 N·m | 120.0 ft·lb162.7 N·m |
| Grade 5 | 173.4 kN38990 lbf | 624.9 ft·lb847.3 N·m | 465.9 ft·lb631.6 N·m | 306.8 ft·lb415.9 N·m |
| Grade 8 | 245.1 kN55103 lbf | 883.2 ft·lb1197.4 N·m | 658.4 ft·lb892.6 N·m | 433.6 ft·lb587.8 N·m |
| A307 | 68.4 kN15375 lbf | 246.4 ft·lb334.1 N·m | 183.7 ft·lb249.1 N·m | 121.0 ft·lb164.0 N·m |
| A325 | 173.4 kN38990 lbf | 624.9 ft·lb847.3 N·m | 465.9 ft·lb631.6 N·m | 306.8 ft·lb415.9 N·m |
| A490 | 245.1 kN55103 lbf | 883.2 ft·lb1197.4 N·m | 658.4 ft·lb892.6 N·m | 433.6 ft·lb587.8 N·m |
| A574 | 282.9 kN63590 lbf | 1019.2 ft·lb1381.9 N·m | 759.8 ft·lb1030.1 N·m | 500.3 ft·lb678.4 N·m |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| Grade 2 | 74.3 kN16694 lbf | 261.5 ft·lb354.6 N·m | 192.5 ft·lb261.0 N·m | 123.5 ft·lb167.4 N·m |
| Grade 5 | 189.8 kN42678 lbf | 668.5 ft·lb906.4 N·m | 492.1 ft·lb667.2 N·m | 315.6 ft·lb427.9 N·m |
| Grade 8 | 268.3 kN60315 lbf | 944.8 ft·lb1281.0 N·m | 695.4 ft·lb942.9 N·m | 446.1 ft·lb604.8 N·m |
| A307 | 74.9 kN16829 lbf | 263.6 ft·lb357.4 N·m | 194.0 ft·lb263.1 N·m | 124.5 ft·lb168.7 N·m |
| A325 | 189.8 kN42678 lbf | 668.5 ft·lb906.4 N·m | 492.1 ft·lb667.2 N·m | 315.6 ft·lb427.9 N·m |
| A490 | 268.3 kN60315 lbf | 944.8 ft·lb1281.0 N·m | 695.4 ft·lb942.9 N·m | 446.1 ft·lb604.8 N·m |
| A574 | 309.6 kN69605 lbf | 1090.3 ft·lb1478.3 N·m | 802.5 ft·lb1088.1 N·m | 514.8 ft·lb697.9 N·m |
Torque for 1" hex head bolts and nuts, standard ISO/ASME heads on steel with a 27.0 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
1" thread and dimensions
- Coarse thread
- 1"-8 UNC — pitch 8 TPI
- Fine thread
- 1"-12 UNF — pitch 12 TPI
- Tensile stress area Aₛ
- 390.8 mm² (coarse), 427.8 mm² (fine)
- Pitch diameter d₂
- 23.338 mm
- Tap drill
- 7/8 (coarse), 59/64 (fine)
- Wrench size (hex head)
- 1-1/2"
- Clearance hole
- 27.0 mm
How the 1" 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 × 390.8 mm² = 173.4 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 173.4 kN × (0.16·3.17 + 0.58·0.15·23.34 + 0.15·32.54/2) mm = 847.3 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (32.54 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for a 1" Grade 5 bolt?
About 624.9 ft·lb (847.3 N·m) with dry threads, 465.9 ft·lb (631.6 N·m) with oiled threads and 306.8 ft·lb (415.9 N·m) with PTFE or moly paste, for a coarse 1"-8 UNC thread tightened to 70% of yield. The resulting clamp force is 173.4 kN.
What is the torque for a 1" Grade 8 bolt?
About 883.2 ft·lb (1197.4 N·m) with dry threads, 658.4 ft·lb (892.6 N·m) with oiled threads and 433.6 ft·lb (587.8 N·m) with PTFE or moly paste, for a coarse 1"-8 UNC thread tightened to 70% of yield. The resulting clamp force is 245.1 kN.
What size wrench fits a 1" bolt?
A standard 1" hex head bolt or nut takes a 1-1/2" wrench or socket.
What drill size do I need to tap 1"?
Use a 7/8 drill for 1"-8 UNC and 59/64 for 1"-12 UNF.