Axial Bearing Installation : with and without washer Washer

[iucu]

What is the difference between installing a bearing on :
- Housing Steel shoulder (bearing outer ring touch the housing shoulder)
- Steel washer (between housing and bearing is a washer)
If Housing is aluminum, I may understand, to prevent the wearing, but if housing is steel, what would be the benefit of Washer ?

 

[tbuelna]

The separate washer (or spacer/shim) makes it easier to adjust the spacing of a pair of outer bearing races to create a specific axial preload or clearance in the bearing set. Machining a separate washer to fit at assembly is easier than machining the housing, and the washer costs little to replace if machined incorrectly.

Using selective fit at assembly of incremental thickness washer/spacer/shim sets allows precise control of axial preload/clearance/position without having to machine the shoulder faces of mating housings to tight location tolerances.

http://www.northernindmfg.com/selective-fit-precision-shims/