<VV> Re: Re: Spindle Question

[Rex Chivers]

Hello Dan, understand about the relationship between fit and function.  Have 
machined and rebushed many motor endbells in my day.  Typically we would 
make the outboard (axially (sp?)) captive bearing a .0003 interferance and 
the inboard .0003 clearance so that the shaft could grow lengthwise due to 
thermal expansion, but would remain in a fixed position (relative to the 
outboard bearing) when run uncoupled from thrust faces.

The outer races of both inner and outer bearings appeared to be a good snug 
fit as they were installed, however I guess it is always possible that they 
have spun in the housing at the very bottom of the fit.  Did not actually 
mic the fits, and I guess it is possible that the one of the new bearings 
actually failed, I will know more when I disassemble it Saturday.

So if I understand what you are saying is that even though the inner races 
of both the inner and outer bearings have clearance that the load on the 
bearing created by the weight of the vehicle prevents them from spinning on 
the shaft, and not the fit to the spindle .  Also you mentioned the outer 
bearing inner race having a ~.001 clearance, can I assume the same for the 
inner bearing inner race as it is a slip fit on the spindle also ?

Lastly, loctite red (stud and bearing mount) would be the correct choice if 
needed ?

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There are rules about when and why a race is supposed to fit tight or loose. 
Mostly its whether the load rotates relative to the bearing or not.
An electric motor with a horizontal shaft needs the bearings tight on the 
shaft, but the bearing ODs can be a slip fit in the motor end bells. 
Conventional front wheel hubs are the opposite, and need the outer races 
genuinely tight to prevent creep.
The outboard inner race needs to be a slip fit (~0.001 inch diametral 
clearance)on the spindle to allow adjustment.  Because the load (car 
weight/gravity) is always one direction there is minimal tendency for the 
inner race to creep even with clearance.  If the outer race was a slip fit 
in the hub it would creep slowly as the wheel turned, and wear it and the 
hub.

Knurling a shaft to tighten a bearing fit is looking for trouble.  Even in a 
slip fit application the support needs to be 100%.  I've got an old "Ask 
Walt" bearing seminar with pictures of a bearing race with the knurl pattern 
fretted right into the race ID surface.  The right grade of loctite plus 
primer on degreased slightly worn parts is going to work for a long long 
time.
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