Bolts Screws and Studs

Types of Replacement Bolts, Screws, and Studs

Shoulder bolts are the group most often misunderstood. The smooth shoulder is a bearing surface that a linkage or roller turns on, and the thread exists only to retain it. Substituting a fully threaded bolt of the same nominal diameter puts a moving part on a thread, which chews itself out and takes the mating hole with it.

Structural and machine bolts carry rated loads, and material grade is what makes them capable of it. A visually identical fastener of a lower grade will thread in, torque up, and then fail under a load the original handled. Studs and stud kits are used where a joint is opened repeatedly, since a stud protects the threads in the casting from wear each time. Flange screws spread clamp load without a separate washer and are common where sheet metal or castings would otherwise dimple.