I'm using XL belts, purely because I already have lots of XL timing pulleys which will enable me to experiment with the ratios. HTD would be better in theory.

I will use a form tool to cut the pulleys. The profile is a simple trapezium which I have ground on to a piece of HSS. You can make HTD pulleys accurately with a ballnose cutter ... or some people use a drill but I think that's a bit crude.

If you do decide to try it you might find my program here useful:

http://www.mycncuk.com/forums/showth...ating-programs