[HowardWoodard]

Thanks.  I haven't a clue how I can rough up the surface of the steel ball.  Maybe with a diamond cutting wheel on my Dremel.  The convex is already pretty rough.

Under a microscope you can see a ridge of some kind of residue on the ball from where it was in contact with the top ridge of the convex end of the shaft.  Maybe there was some kind of electrical welding used to manufacture the completed shaft.

I'm still hoping to find a replacement shaft.  I have a lead on what might turn out to be a parts donor.