Use of thinner sheet metal makes proper threaded fastener selection more critical.

In thread forming and tapping applications, as materials get thinner, the assembly window between how easily a part forms threads (drive torque) and the point in which threads strip out (failure torque) narrows. As a result, torque levels must be tightly controlled and designs that optimize products' performance in the joint must be used. Product designs that have smaller thread pitches, the distance from thread crest to thread crest, and features under the head are often considered. In ideal cases the mating part can be configured with an extrusion, which will increase the engagement length for the threads. The result is improved assembly performance, says Gene Simpson, director of engineering and technical services for Semblex Corp., Elmhurst, Ill.