We tend to think of press fit assemblies as being relatively small. For example, a bushing for an automotive control arm assembly is typically less than 2 inches in diameter. But, much larger assemblies can also be accomplished with press fits, too. One example is railcar wheelsets. Railcar wheels are 36 inches in diameter and several inches wide. A wheelset—two wheels connected by an axle—can weigh more than 400 pounds.

Wheels can be press fit or shrink fit to axles. Also known as a force fit or interference fit, a press fit is an assembly in which one part is inserted tightly into a hole in another part. The assembly stays in place through friction and the force of the two parts pushing against each other. The process is reliable, simple, and does not require heating, cooling or soldering.