"There are many different ways to make holes in things. Most of them involve drilling or cutting in some way, but there are other techniques. Years ago, the husband of a friend of my wife came to me for help. He was a civil engineer, but also very gifted mechanically, and he had a roomful of lathes, milling machines, and the like. He wanted help to build a spark erosion machine. This works by repeatedly bringing a shaped metal electrode onto a workpiece. Every time this happens there is a spark between the electrode and the workpiece. The electrode is immediately withdrawn and then brought down onto the workpiece again, and again, and again. Each spark erodes a tiny part of the workpiece. If you do this fast enough and long enough, you will slowly but surely erode the workpiece away."
Scratches to Sketches