EDM (electrical discharge machining)
is a method for cutting holes, pockets, and other shapes
into hardened steel, as well as imparting a surface texture
to the internal cavities of mold tools. Square pocket
holes are often created with this method. With wire
EDM, a copper wire is continuously fed between two spools.
When electrically charged, it’s able to cut through hardened
tool steels quickly and
accurately.