EDM stands for electronic discharge machine. They generate a spark between an electrode and the workpiece. This spark wears a path through the workpiece. The path takes the shape of the electrode. In a sinking EDM, an electrode could be made square and then square shaped holes can be burned and so on. Sinking EDM's are priceless when a tap or drill bit breaks off in a workpiece. The taps and drills can be burned out using a small electrode. The main reason I built one.
In a Wire EDM the wire is the electrode and since the wire is round it can feed in any direction under CNC control. Fresh wire is feed into the work area as it wears.
The pic is my home built sinking edm. Both types of machines are impressive to watch run.
Jim
