SHRINK FITTING – PURE PHYSICS FOR A SECURE GRIP
Shrink fitting looks very simple: just insert, it fits, it holds and it’s done! Only getting the components apart again is difficult – because a shrink-fit connection can no longer be separated without mechanical damage.
Nearly all materials shrink a little when they cool down. This physical phenomenon is applied when shrink fitting to connect two metal parts, such as a drive shaft and a gearwheel. The prerequisite is two workpieces where the outer dimensions of the one match the inner dimensions of the other with a slight oversize. The inside workpiece is frozen with cryogenic CO2 pellets or a liquid nitrogen immersion bath until it shrinks enough. This imparts the play needed in order to insert it into the opening of the outside part. As a rule, fractions of a millimeter suffice. Now you only have to wait. As the part warms back up again, it expands and creates a high-strength press fit. Additional components such as screws, wedges, clamping rings or weld seams are not needed. Which also eliminates the possibility of forming stress peaks or technical weaknesses. The crystalline structure of the metal also remains unimpaired – unlike in methods that work with heat. Shrink fitting preserves the material, is safe, fast and economical. Among other things, it is used on highly stressed shafts, ball bearings, bushings and journals.
