Thanks for the help everybody!
I had spent some time searching the WWW for the answer, but I felt like
a guy trying to do a search on how to put motor oil in a car. You'd
probably come up with several pages detailing viscosity, thermal
breakdown, the refining process, environmental issues, etc, when all you
really need is someone to say "dump it in the valve cover".
My understanding of trigonometry is pretty limited, and I'm having a
hard time wrapping my mind around the concepts and understanding the
terms, but from reading through the responses, this looks like exactly
the information I will need. Once it soaks in, I plan to use that
knowldege to build a couple of jigs for cutting keyed miter slots on a
table mounted router (or a TS, I suppose) and I'll post the plans and
pictures on my website, and post a note in the wreck here in case
anybody else might be interesting in making such a jig.
Special thanks to Bill Rogers, who, despite his initial dislike of me,
still gave me the benefit of the doubt and offered his help. Also,
eyeballing it would work, but I thought it would be handy to know in the
planning stages if my lumber is X thick and I want the key to be Y long,
can I do it without cutting through the box?
Thanks again everybody. I'll mull over the math stuff a bit and build a
couple jigs then hopefully have the information to share with everybody
here in a week or two.