I think the fingernail test is probably a pretty fair assessment. It's the way I've done it my entire life... well that and a visual inspection. There may be some tolerance in the number but it certainly wouldn't be much. I can't say I've ever seen a spec for that but one could exist.
I looked in my factory manual I have hoping for some specs but couldn't find any. I have a pretty good set of slide calipers so I measured the id of the bearing and the od of the spindle and came up with .006 difference. Would that be enough to hold that collar and not let it spin?
Thanks for your reply and thoughts.
I found out that the diameter of the spindle is 1.624 from the threads to the step for the seal. The ID of the bearing collar is 1.625. I remeasured mine and they're a little smaller than spec and I can't seem to find any spindles so I'm going to get some new bearings and put it back together and hope for the best.