Radial Run Out Stack up

[umatrix]

I have a roller bearing, the cup and cone have a circular runout tolerance. The hub that the shaft and bearing are inserted also have a circular run out tolerance.

I am a trying to understand if the cup and cone tolerances will add/stack up and affect the hub run out?

 

[Tmoose]

The run-outs could stack up in many different ways.
Would the function of your machine be affected if the hub and bearing runouts were at the theoretical maximum and assembled to create the greatest runout?

Precision machine tool spindle builders will position the race and (usually rotating) shaft runouts to reduce the assembly runout.
Super precision spindle bearings have the runout high spots marked to allow optimized assembly.

 

[umatrix]

Thanks Tmoose.

Are there any good references for doing a radial run out stack up of bearing and hub/shaft assembly, that you can suggest ?

 

[3DDave]

Runout is, worst case, nominally twice the radial offset; if the runout of the bore to the OD is 0.0002, then the offset of the axis is 0.0001. (inch tolerance) Radial stack is linear stack + phase. In phase they add, 180 degrees out, they subtract.

 

[umatrix]

This is for a wheel bearing. I am trying to find the radial stack up of the inner and outer bearing and the hub.

Circular Run Out
Inner bearing = 0.070
Outer bearing = 0.070

Hub = 0.075

The datums A-B are the bores.

Could I also find the lateral runout from these tolerances ?

 

[3DDave]

Axial runout from radial runout?

 

[umatrix]

Let's come back to the lateral run out. First I would like to see if I have the right idea for the radial stack.
Would radial run out stack simply be bearing circular radial tolerance + the hub radial tolerance ( 0.070+0.075) = 0.145

 

[3DDave]

Runout is between a surface and an axis. In a bearing there is runout between the bore and the inner race and another between the outer race and the outer surface and between the bore and the outer surface. The hub has runout between the bearing bore and other surfaces, though except for the radial location of the studs / wheel bolt holes, it doesn't matter much.

Are you looking at runout around the bearing bore or about the outer race as the hub turns on the bearing?

 

[umatrix]

I took the run out tolerance of the inner race and outer race and summed them to get 0.070. I.e, Inner race r/o tolerance 0.035 , and outer race 0.035.

I am looking for the runout on the surface of the hub, and how both bearings run out contributes to it.

 

[3DDave]

0.070 is the value to use if the bearing is seized with rust and the hub is spinning on the hub shaft.

 

[umatrix]

sorry, I guess I am missing the point. Thanks for trying to help. It's probably the way I am presenting the question.

 

[3DDave]

What is the surface that controls the axis of rotation?

 

[umatrix]

I believe it would be the hub bore, the surface that the bearing cones insert.