Pretty much everything I've ever done is because of either survival or model airplanes. I took seven math courses in high school just so I'd never have any problems understanding the math. I've never done any machining but have done extensive drafting.
As far as it goes, I'm sure even with no instructions at all, a whole bunch of metal and a lathe and mill I'd eventually figure out the do's and dont's, but I'd probably be significantly injured a few times in the process, not to mention turn out a whole lot of metal spirals and nothing to show for it.