Please c.f.,
Thanks Will for the acknowledgment, I hope it’s still useful to folks. 
It’s a very cool thing — I’d really like to see a couple of more general things along these lines — I’ve fiddled w/ this sort of thing a bit in METAPOST, but it’s not as cool when one has to manually do CAM.
In particular, I’m doing parts w/ tenons and matching mortises — the tenons at least are just a matter of a couple of pockets of various sizes.