ABSTRACT
The preload must be determined before the tightening torque can be defined. Proper preload is difficult to determine, whether for an inch or metric fastener. The following calculations will help you to come up with a close approximation. The necessary minimum preload (clamp load) can be measured (tested in the actual application) or can be calculated with the following formula. At any rate, the preload should be determined in such a way that there is always a minimum clamp force in the joint to prevent slipping or separating in the interfaces of the joint members when the operation forces are applied.
