Originally Posted by CrankyFranky

I understand that hardness and sphericity are distinct qualities. And that austenitic structure is destroyed by heat treatment. I guess that you can get the 304 or 316 balls in Gr.25, but I don't see them commonly. When you go to the LBS and ask for grade 25 balls, they don't tell you the hardness.

Since the older cup-and-cone machines weren't built to today's standards of accuracy, and since one adjusts the bearings more-or-less by feel as per the many descriptions of proper adjustment to avoid preload, would a more round gr.25 tend to have you adjust the wheel closer and therefore less tolerant of contaminaton or misalignment?

And if the more accurately round grade 25 cited above also is harder, would the properly adjusted hub or BB then be more prone to damage of the cup/cones because the balls are harder than the cups or cones?