ABSTRACT
The threads are obviously an important element of the threaded fastener. They give this
sturdy industrial product its unique ability to be installed, removed, and reinstalled as many
times as we wish. They also affect fastener performance in a major way. As we’ll see, thread
type, thread class, thread configuration, the way in which the threads are produced, and the
fit between male and female threads can affect not only thread strength-and, therefore,
fastener tensile strength-but also the resistance of the fastener to such things as self-
loosening and fatigue. The amount of preload achieved for a given torque can be influenced
by thread configuration and by whether the threads have been cut or rolled. Finally, and not
least, the strength of the threads helps to define the strength of the fastener. All things
considered, it’s worthwhile to take a close look at threads.
