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Bearing unit fit

Bearing unit fit

(OP)
Hi all!

I have a question regarding the bearing units, like in the picture below.



Selecting the appropriate fit for a bearing is quite important I always thought. (Intereference fit/loose fit on shaft/housing) But how are the fits arranged with a bearing unit; a housing and bearing provided by the manufacturer? Is the outer ring of the bearing always an interference fit? So the shaft has always a loose fit? I'm a bit confused here, because nowhere is indicated which fit should be applied.

I have been searching through SKF and INA catalogs, but could not find an answer to my question.


Thanks!

RE: Bearing unit fit

As soon as I opened the SKF catalog, the first page I looked at had the shaft tolerance for a bearing assembly driven by set-screws as shown in your picture. The tolerance I found was nominal - 0.0005" up to 1-15/16" and nominal - 0.001" for 2 inch and above. This would be a slip fit to allow for installation. The housing fit is not provided because they assemble that portion. Housing fits are almost always a slip fit except for stationary shaft applications.

Johnny Pellin

RE: Bearing unit fit

The mating shaft for this particular type of bearing is usually a loose slip fit, and the set screws are used to prevent the shaft from spinning inside the bearing bore. The bearing OD has a spherical interface with the flange, which allows for some angular misalignment capability in the bearing attachment. This type of bearing is usually located at assembly and held in position by clamped friction from the flange bolts.

RE: Bearing unit fit

It should be noted that the loose fit / set screw arrangement is not suitable for severe loads / severe conditions. It works, but it is a tradeoff between convenience/serviceability vs robustness.

The outer race fits within pillow block bearings varies - they are usually quite close but clearance fits.

RE: Bearing unit fit

Good morning, i am facing also the same problem of the bearing fits and tolerance, i have one bearing 6206 2RS CR and because that bearing housing damage, i have to fabricate a new housing but i do not know what is the tolerance i have to inform to the Lathe operator, any one have experience about that issue?

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