Mounting Bearings 1

[tombak71]

Hello all
Question 1
I am currently doing my apprenitceship as Fitter Machinist and recently one of the tasks where I work, was to fit the bearings on the new tail pulley shaft. Shaft size is 50 mm and the bearings that I've used is 22211(SKF). I've mounted the new bearings under supervision of tradesman and everything went fine. Next day the tradesman that was supervising me went on his break and onother tradesman was suposed to check on my work. First thing that he's done was, he removed the bearing housing covers and had a look at it, then he asked me why I haven't used the spacer on one side to fix the bearing?
He's explanation was that always bearing spacers should be used in oredr to have one side fixed and the other floating.
He couldn't give me more information.

Can anyone explain and maybe refer some useful articles or web pages regarding this?

Thanks in advance
tombak71

 

[ischgl99]

You can go to

http://www.fag.com

and after registering download a lot of information on bearing housing and shaft design, mounting, unmounting, lubrication, etc.

To answer your question, typically one side is fixed and the other floating to allow for shaft expansion. If both sides are floating then the shaft can shift in the housing and if both sides are fixed, then as the shaft heats up, the bearings will see an axial load, leading to premature bearing failure. The fixed side usually will have the housing designed so that the inner and outer races are fixed in place. The spacers he was talking about are used to do this, some designs have the spacers machined into the housing and cover.

 

[tombak71]

Thanks a lot mbensema for very clear information.

tombak71

 

[unclesyd]

Take the advice given above for a beginning and try to check out each bearing manufacturer's web site for additional information. It used to be that bearing manufacturers put on free clinics on bearings and couplings, but you don't see that much anymore.

In locking shaft bearings very common mistake is not locking the bearing next to the coupling which will allow the axial load to be transferred to the coupling. Some couplings can take this axial load with no problem and some can't. It always pays to check which way the designer wants the axial movement to go.

 

[tombak71]

thanks unclesyd, much appreciated
tombak71

 

[brgguy22]

Right-on with the info, except on your description, the part number 22211 would call out a 55mm bore bearing. FYI the "spacer" is call a "stabalizer ring" or "stab ring". They usually come with every new housing. They are best used closest to the driver (motor, on the head pulley) but in your tail pulley application, it should not matter. One caveat though is to never fix both bearings.

 

[tombak71]

thanx brgguy22