Quick-reference torque values for 1-3/8" bolts across all SAE grades. Dry steel, UNC thread.
Values assume dry/plain steel (K = 0.20) and UNC thread. See full details →
A dry 1-3/8" Grade 5 bolt takes 1469.0 ft·lbs (1991.7 N·m) on the coarse 6 TPI thread. Oiled, that falls to 1101.8 ft·lbs; the dry figure on an oiled bolt overshoots the intended clamp load by about 33%. Grade 8 needs 2382.2 ft·lbs (62% more), and the fine 12 TPI thread raises the Grade 5 figure to 1672.5 ft·lbs.
1-3/8" bolts carry torques beyond most hand wrenches; a torque multiplier or hydraulic wrench is normal, and critical joints are better controlled by bolt tension than by torque. Grade 5 uses the reduced 74 ksi proof stress above 1" and Grade 2 the 33 ksi figure, which is why Grade 8 pulls further ahead at these sizes.
ft·lbs unless noted. Clamp load is the 75%-of-proof preload in lbs.
| UNC (coarse) | 1-3/8"-6 |
| UNF (fine) | 1-3/8"-12 |
| Stress area (UNC / UNF) | 1.155 / 1.315 in² |
| Hex wrench size | 2-1/16" (hex cap screw, ASME B18.2.1) |
| Tap drill (UNC / UNF) | 1-7/32" / 1-19/64" |
Threads per ASME B1.1; tap drills for about 75% thread engagement.