J. M. Leadbeater said:
Many years ago one London dealer bought a pile of FAG NJ306E bearings with brass cages....as I went to put them into stock I opened one up, took the outer raceway off and looked at the rollers under a good light to see the slight tapering at the edges of each roller...there was non. I phoned FAG who suggested they must of been old stock as their bearings now had 'crowned' 'superblend' rollers. The dealer flogged them to Commando owners...wonder how long they lasted??...... DO NOT ASSUME a bearing has crowned /superblended rollers. If you cannot see the 'crowning' / 'superblending' on the rollers 1 phone the bearing manufacturer and ask or even 2 pull out a roller and run a micrometer over it....assuming you can use a micrometer or even that you have one....
Again JM, you have to destroy the race to 'pop' a roller out - on the bearings I have seen anyway. ?
And, the 'crowning' you mention is described in the literature as the VERY SLIGHT ROUNDING on the VERY END of the roller.
There is no way to use a micrometer to measure this, it is only a mm or 2 on the very end of the roller.
The rest of the roller is a perfect cylindrical shape - as you would expect in a cylindrical roller bearing !
Also, I have had a quick look at the rollers on a Hoffman bearing in an early dommie engine.
They appear to have rounded edges on the rollers - and this would be a circa early 1950s bearing.
When I get a chance, I'll take another pic - the one I did in a hurry the other day was blurry, focussed on the wrong area,
when I had a chance to review it.
They (Hoffmans) didn't come in a C3 clearance option though (?).
Which is the important bit these days to ensure they don't crush when installed...
Maybe the FAGs you saw had missed a stage in the manufacture ?