Fundamentally, shrink-fitting is a simple operation involving either contraction or expansion of one component on another to cause interference and the development of pressure, holding the two components together mechanically.
Each method of securing parts in an assembly has unique advantages. In the case of shrink-fitting, parts made from any metal can be assembled: steel to steel, steel to copper, aluminum to steel, magnesium to steel, etc. Usually, the temperatures involved in heating for expansion are significantly lower to avoid changes in metallurgical structure as in tempering or melting. Due to the possibility of stress concentrations, the influence of shrink-fitting should be evaluated in critical assemblies.
In practice, the operation is simple, requiring minimal preparation of surfaces, minimal control, and no cleaning after assembly frequently. Since the securing force is mechanical, superficial oxidation or tarnishing does not interfere, avoiding any need for the use of flux. Parts assembled by shrink fitting can be disassembled by selectively heating the outside component. This procedure is especially suitable for induction heating with its rapid heating rate and accuracy, permitting replacement of worn parts or correction of alignment.
Induction heating often offers unique advantages in shrink-fitting. Heating may be localized, providing sufficient expansion locally for a shrink-fit without heating a whole large casting or carefully machined component, minimizing distortion. This rapid, selective heating also facilitates the dis-assembly of shrink-fitted components, as noted above. Additionally, induction heating provides a fast, repeatable process that can be incorporated in production for minimum handling and easy automation.