By Yossi Tuchner, vibration specialist certified to
ISO 18436 CAT III
Why Bearings Are Heated for Mounting
Bearings and shafts are designed with an interference fit so the bearing will not slip on the shaft during operation.
Heating the bearing expands the inner ring, creates a temporary clearance, and allows smooth mounting without force
that could damage rolling elements or raceways.
Heating Methods and Their Implications
Open Flame Heating
An open flame applies radiant heat to one side of the bearing and relies on conduction to warm the rest. This method
is poorly controlled and often overheats the heated side while the opposite side remains relatively cool. The resulting
temperature gradient can degrade surfaces and still leave the bearing insufficiently expanded, which risks sticking on
the shaft during mounting. Localized overheating may also alter surface metallurgy and make the material brittle.
Hot Plate Heating
A hot plate conducts heat from one side into the bearing. Although more uniform than a flame, it can still produce
significant temperature gradients. As with a flame, one side may be overheated while the other is not warm enough,
which can shorten bearing life and cause difficulties during mounting.
Induction Heating
Induction heating uses an alternating magnetic field to induce eddy currents in the bearing. The bearing heats
quickly and uniformly throughout its mass. Modern heaters use built-in temperature sensing to control the target
temperature and heating rate, which protects the bearing rings, rolling elements and seals.
- Controlled temperature via integrated sensors for accurate inner ring targets and proper heating rates.
- Uniform heating that provides consistent inner diameter expansion and reduces the risk of sticking on the shaft.
- No adverse change to material properties when used correctly. Even sealed and greased bearings can be heated.
- A demagnetization cycle at the end removes residual magnetism to prevent debris attraction after installation.
Conclusion
Compared with open flame or hot plate methods, induction heating delivers precise, uniform and repeatable results that
protect bearing integrity and simplify mounting. For details or assistance selecting a heater and defining temperature
targets, contact Tuchner Engineering.