Basic-shaft System

a system of fits for mating plain (unthreaded) parts of machines in which the shaft represents the basic part. Thus, for given design dimensions of the mating parts the limiting dimensions of the shaft remain constant for all fits. Various types of fits are achieved by changing the limiting dimensions for the holes of one of the mating parts. The use of the basic-shaft system is expedient when the shaft can be used without any additional machining, for instance, shafts made of sized material. It is also used where several parts are to be mounted on the same plain shaft using different fits, for instance, in mating a wrist pin with a connecting rod and piston of an internal-combustion engine.