Join Date: Jan 2015
Location: Norway, Sandnes
Theoretical you are right about the lateral force. When you apply a force at the end of a wrench, this force does two things. It applies a moment (arm x force) and a lateral force to the socket/nut/bolt equal to your applied force but in opposite direction. This force will be lower with a longer wrench and higher with a shorter wrench for one particular moment. The lateral (radial force to the threads) force will only cause some friction in the threads reducing the moment slightly. This must not be mixed with the friction caused by the axial force in the threads. The example below has nothing to do with the threads itself, it would also be the same turning a shaft in a slide bearing.
An example: Moment 30 Nm, wrench length 0.5m. Nut/bolt diameter 0.025m (25mm), frictional coefficient 0.15.
Lateral (radial) force = 30Nm/0.5m = 60N. Frictional force (or tangential force) in nut/bolt= 60Nx0.15 = 9 N.
Reduced moment caused by friction = 9N x 0.0125m=0.113 Nm. (0.0125m is radius of nut/bolt threads)
In other words, this can fully be ignored. To ensure a correct moment, I agree with the previous post, what about the calibration of the torque wrench?.
2016 FJR AE (ES)
Last edited by rogerf; 03-20-2018 at 03:58 AM.