shrinkfit

Shrink fit, also written shrink-fit, is a method of making a tight, interference fit between two components by exploiting differential thermal expansion. By heating one part or cooling another, the components are temporarily enlarged or reduced in diameter; once assembled and returned to ambient temperature, the parts press against each other with a strong interference.

The fit relies on the coefficient of thermal expansion and the chosen tolerances. Typical practice is to heat the outer component (for example a bearing outer race or a hub) in a controlled manner or to cool the inner component (such as a shaft or a pin) so that the components can be assembled with modest force. The assembly is then allowed to cool and contract, creating clamping pressure and a rigid joint. Induction heating is commonly used for rapid, local heating and repeatable builds; ovens and oil baths are used for larger parts.

Applications include mounting bearings on shafts, assembling gears, hubs, pulleys, tool holders, bushings, and other interference-fit joints in automotive, industrial machinery, and machining equipment. Shrink fits offer high to very high torque and stiffness without fasteners or adhesives, and can provide good concentricity and load transfer.

Limitations include the need for careful temperature control to avoid altering metallurgical properties or causing surface damage, potential difficulty in disassembly, and the requirement for compatible materials and tolerances. Disassembly usually requires heating or cooling and replacement of components after overly repeated thermal cycling.