There is a difference between post and pre-1972 headstock bearings for the old Delta 46-111. Does anyone know where I can buy the SP-5339 equivalent bearings? I picked up a 1969 generation unit to dedicate to my Beall buffing system.
The detail most often overlooked when people think they can do this^^, is the fact that the non-extended side of an 875xx-series bearing isn't flush...it's recessed - a lot of folks don't realize this. It's best to use bearings consistent with the original design.Sometimes you can get away with a spacer to account for the extended race. But that depends on the ability to make an accurate thickness spacer.
There is some truth to this, particularly with decades old bearings - less so with current mfr of them. There are now several types of sealed bearings. This link explains differences. Speed ratings can be looked up.With older sealed bearings there were issues with friction heating because of the seals.
Don't just automatically replace a shielded bearing with a sealed bearing. Name brand sealed bearings now come with a max rpm rating. I don't know that I would buy a sealed bearing without knowing its rpm rating is well beyond my rpm needs.
In my experience very high rpm bearings are usually not sealed. Possibly because of the seal friction issue.