I use the Devcon epoxy for the corks and a drillstock mandrel. I've learned how close to the center i can apply the epoxy on both sides of each ring so as not to epoxy it to the mandrel but i don't worry about the outside, though it's better if the epoxy isn't on the outside. Not a huge prob if it is though...unless i'm shaping completely by hand, in which case i'm more stingy with the epoxy out towards the edges.

Since the rings are on a smooth mandrel i don't clamp them, rather stand the mandrel and rings on end with the bottom cork supported against the top of the vice jaws that's holding the end of the mandrel then i slide something on the top end that presses the corks a little...it doesn't take much...something like few fender washers or whatever is handy.

Cheers,

MontanaMoose