Originally Posted by Steve_sr

I did some testing today with some half inch wide .003" pieces of an aluminum Coke can. As I suspected the bore is tapered. Smaller at the bottom than the top. Bottom looks to be about .014" while top is .020" dia. gap.

So it looks like I will need to find some .007" shim stock. The other question is what material should I use. I was thinking about either stainless or brass. As suggested I will be stretching (rounding) over the top to keep the shim from sliding down the bore. Is stainless malleable enough for this without cracking or should I use brass instead?

The local hardware store was zero help. I have found some shim material online but it is much larger quantity than I really need at significant cost. Only need a 4" x 4" piece. Any suggestions on other places to look for shim stock?