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Shrink Fit vs Force Fit Pros & Cons

Shrink Fit vs Force Fit Pros & Cons

(OP)
Morning guys,

I have been researching interference fits of bearings on shafts and if there are any advantages or disadvantages to shrink fit vs force fit. From what I could gather, when using shrink fitting one doesn't have to use a large amount of force when sliding the bearing onto the shaft and the risk of seizing or galling the shaft is reduced. Also, no beveling of the shaft and other parts is necessary.

However, I was wondering if there are other factors that can further separate one vs the other.

Any input is much appreciated.


RE: Shrink Fit vs Force Fit Pros & Cons

Aromit53,

I design aircraft mechanical systems (transmissions, actuators, etc) that often use high-performance rolling element bearings. First, whenever practical we try to eliminate inner bearing races (usually with cylindrical roller bearings) and use a hardened shaft surface instead. When a separate inner race that requires an interference fit on a shaft is used, thermal fitting is usually the preferred assembly method. When performed correctly thermal fitting is the method least like to cause damage to the race or shaft surface. However, removal of a bearing race having an interference fit to a shaft is a different story. Since it's not usually practical to produce sufficient temperature differential between the race and shaft to relieve the interference fit. A special puller tool is typically used to apply a balanced axial force between the inner race and shaft to minimize damage during removal. Aerospace rolling element bearings often have puller grooves at the free end of the inner race to make removal easier.

There are limits to thermal fitting bearing races. For example, common commercial bearing steels are usually stabilized for max operating temps of 250-300 degF. So this limits the max temperature you can use for thermal fitting. Regardless of the method used to install your bearing, the most important thing is to do a thorough job of calculating the correct fit for your specific application. This task can get quite complicated with high-performance bearing systems, since the installed fit between the inner race and shaft can have a significant effect on bearing performance at operating conditions.

RE: Shrink Fit vs Force Fit Pros & Cons

Just a note; thermal fitting is not exclusively heating. Lowering the temperature can often achieve the desired results. Of course a combination of both is not unusual.

Clyde Hancock
Design & analysis of electric motors and generators
https://www.motorconsultants.com/home.html

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