1-1/4" Bolt Torque
A 1-1/4" Grade 5 bolt with a coarse 1-1/4"-7 UNC thread needs about 1090.9 ft·lb (1479.1 N·m) when dry and 810.7 ft·lb (1099.2 N·m) when oiled, tightened to 70% of yield (clamp force 244.2 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| Grade 2 | 108.5 kN24401 lbf | 484.8 ft·lb657.4 N·m | 360.3 ft·lb488.5 N·m | 235.8 ft·lb319.7 N·m |
| Grade 5 | 244.2 kN54902 lbf | 1090.9 ft·lb1479.1 N·m | 810.7 ft·lb1099.2 N·m | 530.5 ft·lb719.3 N·m |
| Grade 8 | 392.1 kN88158 lbf | 1751.7 ft·lb2375.0 N·m | 1301.8 ft·lb1765.0 N·m | 851.8 ft·lb1154.9 N·m |
| A307 | 109.4 kN24598 lbf | 488.8 ft·lb662.7 N·m | 363.2 ft·lb492.5 N·m | 237.7 ft·lb322.2 N·m |
| A325 | 244.2 kN54902 lbf | 1090.9 ft·lb1479.1 N·m | 810.7 ft·lb1099.2 N·m | 530.5 ft·lb719.3 N·m |
| A490 | 392.1 kN88158 lbf | 1751.7 ft·lb2375.0 N·m | 1301.8 ft·lb1765.0 N·m | 851.8 ft·lb1154.9 N·m |
| A574 | 452.5 kN101735 lbf | 2021.5 ft·lb2740.8 N·m | 1502.3 ft·lb2036.8 N·m | 983.0 ft·lb1332.8 N·m |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| Grade 2 | 120.2 kN27015 lbf | 522.8 ft·lb708.8 N·m | 382.8 ft·lb519.0 N·m | 242.8 ft·lb329.2 N·m |
| Grade 5 | 270.4 kN60784 lbf | 1176.2 ft·lb1594.8 N·m | 861.3 ft·lb1167.7 N·m | 546.3 ft·lb740.7 N·m |
| Grade 8 | 434.2 kN97603 lbf | 1888.7 ft·lb2560.8 N·m | 1383.0 ft·lb1875.0 N·m | 877.2 ft·lb1189.3 N·m |
| A307 | 121.1 kN27233 lbf | 527.0 ft·lb714.5 N·m | 385.9 ft·lb523.2 N·m | 244.8 ft·lb331.8 N·m |
| A325 | 270.4 kN60784 lbf | 1176.2 ft·lb1594.8 N·m | 861.3 ft·lb1167.7 N·m | 546.3 ft·lb740.7 N·m |
| A490 | 434.2 kN97603 lbf | 1888.7 ft·lb2560.8 N·m | 1383.0 ft·lb1875.0 N·m | 877.2 ft·lb1189.3 N·m |
| A574 | 501.0 kN112636 lbf | 2179.6 ft·lb2955.2 N·m | 1596.0 ft·lb2163.8 N·m | 1012.3 ft·lb1372.5 N·m |
Torque for 1-1/4" hex head bolts and nuts, standard ISO/ASME heads on steel with a 33.3 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
1-1/4" thread and dimensions
- Coarse thread
- 1-1/4"-7 UNC — pitch 7 TPI
- Fine thread
- 1-1/4"-12 UNF — pitch 12 TPI
- Tensile stress area Aₛ
- 625.2 mm² (coarse), 692.2 mm² (fine)
- Pitch diameter d₂
- 29.393 mm
- Tap drill
- 1-7/64 (coarse), 1-11/64 (fine)
- Wrench size (hex head)
- 1-7/8"
- Clearance hole
- 33.3 mm
How the 1-1/4" 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% × 558 MPa × 625.2 mm² = 244.2 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 244.2 kN × (0.16·3.63 + 0.58·0.15·29.39 + 0.15·40.48/2) mm = 1479.1 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (40.48 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for a 1-1/4" Grade 5 bolt?
About 1090.9 ft·lb (1479.1 N·m) with dry threads, 810.7 ft·lb (1099.2 N·m) with oiled threads and 530.5 ft·lb (719.3 N·m) with PTFE or moly paste, for a coarse 1-1/4"-7 UNC thread tightened to 70% of yield. The resulting clamp force is 244.2 kN.
What is the torque for a 1-1/4" Grade 8 bolt?
About 1751.7 ft·lb (2375.0 N·m) with dry threads, 1301.8 ft·lb (1765.0 N·m) with oiled threads and 851.8 ft·lb (1154.9 N·m) with PTFE or moly paste, for a coarse 1-1/4"-7 UNC thread tightened to 70% of yield. The resulting clamp force is 392.1 kN.
What size wrench fits a 1-1/4" bolt?
A standard 1-1/4" hex head bolt or nut takes a 1-7/8" wrench or socket.
What drill size do I need to tap 1-1/4"?
Use a 1-7/64 drill for 1-1/4"-7 UNC and 1-11/64 for 1-1/4"-12 UNF.