bdring wrote:OK, I have mine flipped. I thought it would be better to put the ridge on the inside in case it even decided (unlikely) to come off. Probably OK either way, but my spacers for the other axis were calculated with ridge facing in.
Note: I have seen them bind bearing to bearing. That happened on the rotational engraver. It only takes a thou' or two to do it. It is not a robust design without the shim. You are right that it does not add length in your orientation though.
We can put a dab of superglue on the bearing/derlin sholder to keep it on if there is any concern. It held my shafts well.
I am curious as to if a piece of debris got stuck on the outer race when they were put together. I have used bearings side by side for rollers in many different applications and never had an issue as long as I put them in contact with very clean surfaces. Sometimes I even run a very fine bead of superglue in the valley between the two outer races to keep out desbris. The bearings are ground to incredibly tight tolerances (talking ten thousandths of an inch here). Unless there is a problem with a particular bearing (something not meeting spec), I can't see that being an issue. I can see a piece of plastic or something causing an issue if it gets in between the bearing surfaces, but I can't see face to face bearings causing an issue unless there is a quality or debris problem. There is more lateral slop in the bearing/race than the grind on the width.
At any rate, putting in a spacer will eliminate any concern. I put them in my pulleys just to be sure.