N·m
mm
About 0.2 for plain, dry steel threads; around 0.15 or lower when lubricated. Use the fastener maker's figure if given.
Result
Bolt preload (clamp force)25.00 kN
How it is calculated, with your numbers
- Bolt preload (clamp force)
f = t / (k × d / 1000) / 100050 / (0.2 × 10 / 1000) / 1000 = 25.00 kN
Working uses the metric units the formula is written in.
- t Tightening torque (N·m)
- d Nominal bolt diameter (mm)
- k Nut factor K
- f Bolt preload (clamp force)
What it means
Torque is only a way of reaching the clamping force a joint needs. Most of it is lost to friction in the threads and under the head; the short-form relation T = K × F × d wraps all of that into the nut factor K. Oil or copper grease on the threads lowers K, so the same torque stretches the bolt much further. That is why service manuals say whether threads should be dry or oiled.
Assumptions and limits
- Short-form torque equation; real K varies with finish, coating and lubricant.
Sources
- Budynas, R. G. and Nisbett, J. K., Shigley's Mechanical Engineering Design, McGraw-Hill (torque and bolt preload).