On Fri, 19 May 2006 13:56:29 -0500, "B.B."
u wrote:

The other day I changed the boot on my car's CV joint, and while I
had the thing apart I began to wonder how they go about making it.
For anyone who hasn't had one apart, it's an outer housing with a
spherical cavity with six grooves around the inside. There's a ball
cage that's about six millimeters thick, spherical outside and inside,
with six oblong holes around it. Two a little longer so you can wiggle
the cage into the housing. It's a very snug fit. Inside that, a
six-sided vaguely star shaped piece. Spherical, again, on the outside,
and also a snug fit. The six grooves rounded bottom, for six ball
bearings to fit into.
The part I'm curious about, how do they setup to grind an internal
spherical surface, and how to measure it? Then the grooves cut in the
star and housing, they were rounded-bottom, to hug the bearings. But
there's also a gradient. As a ball rolls toward one end of the housing,
it moves slightly out of the cage, so the housing groove is deeper. But
as it rolls to the other end, the opposite is true, the groove in the
star has to be deeper. Again, how would you set up for that kind of
cut, and how to measure it when done?
I know the factories use CNC machines, but is it practically possible
to make such a shape with only manual machines and mechanical linkages?


Practically impossible just about sises it up.

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