”Spark Erosion is a recent machining technique with lot of advantages in particular when machining difficult pieces with intricated shapes. The principle of spark erosion is uncomplicated. A workpiece and tool are placed in a working position in such a way that they do nor touch each other. The workpiece and the tool are conected to a DC source via a cable. The voltage applied between the electrode and the workpiece and the discharge current have a time sequence. The voltage builds up an electrical field throughout the space between the electrodes. They are separated by a gap which which is filled with an insulating fluid.”