ABSTRACT
This chapter considers in-service clamping force needs of the joint. In some applications, a noncritical foundation bolt is an example, gravity holds the joint in place and it is sufficient for the bolts merely to maintain alignment. Torque-turn equipment which tightens the fastener past yield, or to yield, is growing in popularity for automotive and similar applications. If the bolts are to be tightened by turning the nut or the head, then they will experience some torsional stress as well as tensile stress during assembly. Excessive preload can so compress a gasket that it will not be able to recover when internal pressure or a thermal cycle partially unloads it. The scatter in anticipated results could be narrowed considerably by going to a computerized torque-turn system; and reduced even further by ultrasonic control of assembly. Placing exact limits on the in-service clamping force will usually be impossible.
