Here are a couple more Yahoo discussion groups that may be of interest
to those of us trying to build mechanical music "stuff".
ModelersCad at http://groups.yahoo.com/group/ModelersCad --
discussions of CAD, laser cutting, etching, milling, etc.
Casting at http://groups.yahoo.com/group/casting -- discussions
of most types of casting: plastics, metal using lost wax methods,
conventional metal casting, etc.
Most of these people are building model railroad equipment, including
live steam, and are very knowledgeable.