Ignoramus12789 wrote:

http://igor.chudov.com/tmp/baldor-grinder.jpg

It is a military surplus grinder. I bought a 7" and 6" wheels for
it. It works, it is very quiet and vibrates very little. The wheels
have plastic insert to match the hub and seem to be a bit off
center. How can I center them?

Make bushings on a lathe - aluminum or brass are fine - and make sure they run
true by themselves (I'd drill/ream the hole first, then put it on a mandrel
between centers) and then remount the wheels and true them up with a dressing
stone, diamond, or even a star wheel (Harold will kill me for mentioning it).

GWE