Balancing a 7" grinding cup wheel

[Ken Barnes <barnestrav@zzzzzzzzz>]

Greg,

Just catching up on my e-mail.  I have had significant grinder cup
chatter when my grinder bearings have gone bad.  I ruined a good
diamond cupwheel figuing it out.  I also disfigured a couple silicon
carbide wheels the second time it happened, but they were resurrected
by using a dressing tool.

If you use a grinder with bad bearings it will rotate the cup in a
slightly non-circular fashion, which will wear the cupwheel unevenly,
and eventually the cupwheel will be banging on the stone so hard that
either it or the grinder will come apart, as you have experienced.  You
cannot use a dressing tool to fix a silicon carbide cup wheel while it
is still on the bad grinder, since it is not rotating evenly.  You need
to fix or toss the bad grinder and true up the wheel on a good grinder.
 You can ruin a good grinder's bearings by using a bad cup wheel, so it
can spread from one grinder to another like some sort of virus.  I
could not figure out how to save my ruined diamond cup wheel, so it
sits in the disfigured tool pile and I am amazed at how awful it looks.

Ken Barnes