Bearing fits

[Danni BurnsParticipant @danniburns84841]

Hi all.

I have a couple of bearing housings to mill and I would like to know what the bearing fit/size should be.

I guess that a couple of 0.002″ would be OK (so .03 – .05mm).

I used to Turn/Bore spogots and housings and I would turn to the above sizes and polish it down to custom fit the bearing; but I can’t Bore this on lathe – so its more difficult; hence I would like to know for tooling purposes and to avoid a sloppy job (or stuck bearing)

Does anyone have or know of a resource/table for finding these sizes?

cheers

[mgnbukParticipant @mgnbuk]

Hi Danni,

SKF

have a lot of design info – the challenge can be finding the particular information you want, but it will almost certainly be available on their website somewhere. Fits are dependant on many factors, but are influenced by what is driving the shaft etc. & what it is, in turn, driving. From memory, cyclic loads & drivers (i.e internal combustion engines) require higher levels of interference fit to prevent unwanted rotation of the bearing shells in housings. On a motorcycle engine I have, the interferences are such that the casings have to be heated to 120 degrees C to fit the bearings, then the inner bearing races similarly heated to fit the shafts. Bearings with larger than standard clearances are required, as the preloads reduce the internal clearance when everything cools to normal operating temperatures.

SKF used to do a large printed General Catalogue that contained such information. The copy I have is dated 2003 & runs to 1120 A5 pages. I don’t think they do these any more, so everything is online.

Nigel B.

[Danni BurnsParticipant @danniburns84841]

<p style=”text-align: left;”>Thanks nigel</p>
I will look on the skf link later from laptop. Not the easiest to decipher and near impossible on phone screen.

Cheers

 

 

[DiogenesParticipant @diogenes]

This might save some keyboard ‘legwork’ – https://www.skf.com/uk/products/rolling-bearings/principles-of-rolling-bearing-selection/bearing-selection-process/bearing-interfaces

 

[bernard towersParticipant @bernardtowers37738]

You need to be more careful with ball race fits as having them overtight shortens their life by a considerable amount, not as important on on adjustable bearings like taper Timkins or angular contact astray have room for adjustment. Once told with small bearings (under 1″) that its better to err on the loose side and use bearing fit if possible. Not necessarily true for needle roller bearings as they rely on the correct fit to compress the outer shell to make the rollers fit a predetermined shaft size.

[Danni BurnsParticipant @danniburns84841]

Hi all.

Just to close this off, I found this very good explanation video for Fits Chart – Shaft and Hole.

I think it focuses on just what you need to know as a foundation before getting confused when looking at further charts/sites on the subject for your specific requirements.

It’s a 20-minute clip, so go make a brew first.

https://www.youtube.com/watch?v=pIE-f-pRM-U

warm regards

[Author]

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