Bearing Spacer Tolerance

It depends. To provide an accurate reply to your question, show cross-section of completely installed bearing + shaft, bearing housing, accessories etc.

The roller fits over a shaft that is 0.050" shorter than the measurement on the outside of the bearings and is held together with a capscrew and washer. This pulls the pressure against the inner races and spacer.

Thanks,

dgibson

What about the outer races?

What you are describing is fine, as long as there isn't significent lateral thrust....

The outer races are pressed against the shoulders of the roller. My problem is that we are trying to hold the length of the spacers within 0.0005" of the distance between the two shoulders and this is causing a lot of time to be consumed doing this. I have not been able to glean this particular answer from any of the bearing manuals. If we could stretch the tolerance to +/-0.001 it would save about 10 hours on this run of parts.

Thanks,

This data is not likely to be available on bearing manuals directly.

Based on your application, load - value and type, this is to be calculated.

As far as I can make out from your sketch, this spacer is providing the initial preload to the bearing. This initial pre-load (and it's tolerance) can be calculated by equipment designer or upto some extent by bearing manufacturer.

Unfortunately as I can see from SKF site your bearing D=28mm and d = 12mm. For this size the tolerance of ± 0.01mm (0.0005") seems to be OK if not a bit wide.

Why don't send a mail to your bearing supplier - they should be able to give the exact answer.

The SKF catalogue gives for the radial gap class C3 values from 11 to 25 µm.

The balls for the 6001 bearing have a diameter of 5/32" and the grove radius is usually 1.05 Rball. With those assumptions the axial shift of of the rings will be 0.0808±0.0156mm to contact. For the 2 bearings the probabilistic value will be double.

The nominal value depends on the degree of preloading the designer intends to obtain but as you see the tolerances to the contact are quite large and in a discussion with the designer I am sure you could increase your tolerance field.

This was computed without taking the influence of assembly diametral tolerances on the radial clearance in the assemblied bearing. The effect will be a decrease of the axial relative displacement but I doubt it will modify in a sensible way the dispersion.

If any other question feel free to ask.

Thanks, Dgibson