1-1/2" Bolt Torque
A 1-1/2" Grade 5 bolt with a coarse 1-1/2"-6 UNC thread needs about 1891.9 ft·lb (2565.1 N·m) when dry and 1404.7 ft·lb (1904.5 N·m) when oiled, tightened to 70% of yield (clamp force 354.1 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| Grade 2 | 157.4 kN35382 lbf | 840.8 ft·lb1140.0 N·m | 624.3 ft·lb846.4 N·m | 407.8 ft·lb552.9 N·m |
| Grade 5 | 354.1 kN79610 lbf | 1891.9 ft·lb2565.1 N·m | 1404.7 ft·lb1904.5 N·m | 917.5 ft·lb1243.9 N·m |
| Grade 8 | 568.6 kN127832 lbf | 3037.9 ft·lb4118.8 N·m | 2255.5 ft·lb3058.1 N·m | 1473.2 ft·lb1997.4 N·m |
| A307 | 158.7 kN35667 lbf | 847.6 ft·lb1149.2 N·m | 629.3 ft·lb853.3 N·m | 411.1 ft·lb557.3 N·m |
| A325 | 354.1 kN79610 lbf | 1891.9 ft·lb2565.1 N·m | 1404.7 ft·lb1904.5 N·m | 917.5 ft·lb1243.9 N·m |
| A490 | 568.6 kN127832 lbf | 3037.9 ft·lb4118.8 N·m | 2255.5 ft·lb3058.1 N·m | 1473.2 ft·lb1997.4 N·m |
| A574 | 656.2 kN147521 lbf | 3505.8 ft·lb4753.2 N·m | 2602.9 ft·lb3529.1 N·m | 1700.1 ft·lb2305.0 N·m |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| Grade 2 | 177.1 kN39808 lbf | 917.1 ft·lb1243.4 N·m | 669.1 ft·lb907.2 N·m | 421.1 ft·lb571.0 N·m |
| Grade 5 | 398.4 kN89568 lbf | 2063.4 ft·lb2797.6 N·m | 1505.5 ft·lb2041.2 N·m | 947.6 ft·lb1284.7 N·m |
| Grade 8 | 639.8 kN143822 lbf | 3313.3 ft·lb4492.2 N·m | 2417.4 ft·lb3277.6 N·m | 1521.5 ft·lb2062.9 N·m |
| A307 | 178.5 kN40129 lbf | 924.5 ft·lb1253.4 N·m | 674.5 ft·lb914.5 N·m | 424.5 ft·lb575.6 N·m |
| A325 | 398.4 kN89568 lbf | 2063.4 ft·lb2797.6 N·m | 1505.5 ft·lb2041.2 N·m | 947.6 ft·lb1284.7 N·m |
| A490 | 639.8 kN143822 lbf | 3313.3 ft·lb4492.2 N·m | 2417.4 ft·lb3277.6 N·m | 1521.5 ft·lb2062.9 N·m |
| A574 | 738.3 kN165973 lbf | 3823.6 ft·lb5184.1 N·m | 2789.8 ft·lb3782.4 N·m | 1755.9 ft·lb2380.7 N·m |
Torque for 1-1/2" hex head bolts and nuts, standard ISO/ASME heads on steel with a 39.7 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
1-1/2" thread and dimensions
- Coarse thread
- 1-1/2"-6 UNC — pitch 6 TPI
- Fine thread
- 1-1/2"-12 UNF — pitch 12 TPI
- Tensile stress area Aₛ
- 906.6 mm² (coarse), 1020.0 mm² (fine)
- Pitch diameter d₂
- 35.350 mm
- Tap drill
- 1-11/32 (coarse), 1-27/64 (fine)
- Wrench size (hex head)
- 2-1/4"
- Clearance hole
- 39.7 mm
How the 1-1/2" 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 × 906.6 mm² = 354.1 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 354.1 kN × (0.16·4.23 + 0.58·0.15·35.35 + 0.15·48.42/2) mm = 2565.1 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (48.42 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for a 1-1/2" Grade 5 bolt?
About 1891.9 ft·lb (2565.1 N·m) with dry threads, 1404.7 ft·lb (1904.5 N·m) with oiled threads and 917.5 ft·lb (1243.9 N·m) with PTFE or moly paste, for a coarse 1-1/2"-6 UNC thread tightened to 70% of yield. The resulting clamp force is 354.1 kN.
What is the torque for a 1-1/2" Grade 8 bolt?
About 3037.9 ft·lb (4118.8 N·m) with dry threads, 2255.5 ft·lb (3058.1 N·m) with oiled threads and 1473.2 ft·lb (1997.4 N·m) with PTFE or moly paste, for a coarse 1-1/2"-6 UNC thread tightened to 70% of yield. The resulting clamp force is 568.6 kN.
What size wrench fits a 1-1/2" bolt?
A standard 1-1/2" hex head bolt or nut takes a 2-1/4" wrench or socket.
What drill size do I need to tap 1-1/2"?
Use a 1-11/32 drill for 1-1/2"-6 UNC and 1-27/64 for 1-1/2"-12 UNF.