1-3/4" Bolt Torque
A 1-3/4" A307 bolt with a coarse 1-3/4"-5 UNC thread needs about 1337.5 ft·lb (1813.4 N·m) when dry and 994.0 ft·lb (1347.7 N·m) when oiled, tightened to 70% of yield (clamp force 214.5 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| A307 | 214.5 kN48211 lbf | 1337.5 ft·lb1813.4 N·m | 994.0 ft·lb1347.7 N·m | 650.6 ft·lb882.1 N·m |
| A574 | 887.0 kN199402 lbf | 5531.8 ft·lb7500.1 N·m | 4111.3 ft·lb5574.2 N·m | 2690.8 ft·lb3648.3 N·m |
Torque for 1-3/4" hex head bolts and nuts, standard ISO/ASME heads on steel with a 46.0 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
1-3/4" thread and dimensions
- Coarse thread
- 1-3/4"-5 UNC — pitch 5 TPI
- Tensile stress area Aₛ
- 1225.5 mm²
- Pitch diameter d₂
- 41.151 mm
- Tap drill
- 1-9/16
- Wrench size (hex head)
- 2-5/8"
- Clearance hole
- 46.0 mm
How the 1-3/4" 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% × 250 MPa × 1225.5 mm² = 214.5 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 214.5 kN × (0.16·5.08 + 0.58·0.15·41.15 + 0.15·56.36/2) mm = 1813.4 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (56.36 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for a 1-3/4" A307 bolt?
About 1337.5 ft·lb (1813.4 N·m) with dry threads, 994.0 ft·lb (1347.7 N·m) with oiled threads and 650.6 ft·lb (882.1 N·m) with PTFE or moly paste, for a coarse 1-3/4"-5 UNC thread tightened to 70% of yield. The resulting clamp force is 214.5 kN.
What size wrench fits a 1-3/4" bolt?
A standard 1-3/4" hex head bolt or nut takes a 2-5/8" wrench or socket.
What drill size do I need to tap 1-3/4"?
Use a 1-9/16 drill for 1-3/4"-5 UNC.