Originally Posted by captain america

Hi Hookem. Well OK, first things first: are you using the right size shims? Right size of screw? If you have the right size, the shims shouldn't be able to work their way over the screw.

Shims are used to align the clutch bell with the spur. What vehicle is this for, what clutch are you using, and what engine? Ideally, you want a little bit of back-and-forth play of your clutch bell on the flywheel, and by a little, I mean under 1mm.

Info or pics are always helpful