jimmuller 

I could post this in the Bicycle Mechanics forum but I'm betting I get a better answer here where people haven't completely gone over to the dark side to use cartridge bearings.

What are the general rules of thumb, if they exist at all outside esoteric mechanical engineering textbooks, for radius of curvature vs. bearing size vs axle and cone diameter?

I'm asking because I've seen different bearing cones for a non-bike application which have visibly different radii but for which one would expect the same ball size. So what is the general rule? Could it tolerate a range of radii as long as the balls fit? Does the hub race have to match the cone race to some degree? Does a visibly smaller radius imply it was necessarily meant for smaller balls or might it tolerate a larger size as long as the ball has a smaller radius than the cone?