Comment by mikewarot

You need to be able to move stuff around in a machine shop. I'd make gears and things for fun. The last job I had was very satisfying, but the pay and commute sucked. Doing it for funsies in my own shop would be awesome.

I'd start with my current harbor freight lathe and work my way up to building a cnc tool cutter and then gear hobbing, shaping, skiving, machines, all open source. I've got ideas on how to skive straight bevel gears, which is currently impossible because the pitch varies across the tooth.

Then on to photolithography, atomic force microscopy and eventually high vacuum systems.