Assembling interference fits by expanding the outer part instead of forcing it on.
A shrink fit is an interference fit made thermally. The outer component is heated so that it expands, dropped over the inner component with clearance, and allowed to cool. As it contracts it grips, and the resulting joint carries far more torque and axial load than a fit that could be pressed together without damage.
The critical variable is temperature, because temperature is what decides how much the part has actually expanded. Too cold and it will not go on, or it seizes halfway, which is worse. Too hot and you risk affecting the metallurgy of a part that was heat treated for a reason.
Induction gives fast, controlled, local heating of the outer component, and a machine working on measured temperature rather than a fixed timer will hit the same expansion every time regardless of how warm the part was when it arrived.
No press force on the parts, so no galling, no scoring of the fit surfaces and no damage to a tooth form or a bearing race.
Higher interference than a press fit can achieve, which means more torque capacity from the same joint.
Fast and local: the outer part is heated in seconds while the inner part stays cold, which is exactly the temperature difference the fit needs.
Repeatable: with closed-loop temperature control, every assembly gets the same fit.
We will confirm the configuration for your material, component geometry and production requirements.
The required temperature rise follows from the designed interference, the diameter and the coefficient of thermal expansion, plus enough extra clearance to actually get the part on before it starts cooling. That is an arithmetic question with one answer, and the machine should be set to it.
Shrink fitting needs uniform expansion through the ring, not a hot skin over a cold core. Lower frequency penetrates further and heats more uniformly, which is why these machines are medium frequency rather than high.
If the outer part is hardened or tempered, the shrink fitting temperature must stay safely below its tempering temperature, or the assembly operation quietly undoes the heat treatment.
Send a drawing, the material, the case depth or temperature you need, and your production rate. Our engineers will help define the right machine for your process.
