Electrical Discharge Machine
Electrical Discharge Machining (EDM) is a process that uses electrical discharges from an electrode to erode an electrically conductive material. As a result, it is possible to erode or "burn" the shape of the electrode into the workpiece. If you need a square hole, (or other unique shape) in a part make a square electrode and burn it into the part. This machine is great for removing broken bolts, taps, easy outs, drills, and studs etc. from expensive work pieces!
Will disintegrate metal.