"I was lucky in that I have a friend who is a toolmaker and he taught me the basics of screw cutting and dealing with difficult materials." (Brian)
I worked in a very specific part of the electronics industry, making vacuum tubes, or high power microwave amplifier components. These devices rely on many special metals, alloys and other materials for their construction and function, including working to very high tolerances. In the toolroom you would find tungsten, molybdenum, kovar, inconel, boron nitride, alumina etc and guys with many years experience of machining them. Working alongside them was a good education.
My training as a chemist helped too.
Apologies for a bit of thread drift but Brian is right, in that buying a machine is just the start.