Right, I have segments.exe that does a similar thing. What I need to figure though is the width I need in order to overlay the ring below enough that there won't be a gap.

Say for instance I want to build a bowl that has a 10" top diameter and is 3" high from the table it sits on. I want a graceful curve in to the bottom. How do I figure out how wide a board to use in each ring so that when assembled and placed over the ring below I know the overlap will be enough to allow me to turn it say 1/8" think without poking a hole in it? Maybe I'm just over thinking it and should go with boards that would definitely not have this problem and have a little more waste.

-Jim