The origin of electrical discharge machining (EDM) dates back to 1770 when English scientist Joseph Priestly discovered the erosive effect of electrical discharges. During the 1930s, attempts were made for the first time to machine metals and diamonds with electrical discharges. Erosion was caused by intermittent arc discharges occuring in air between the tool electrode and workpiece connected to a DC power supply. These processes were not very precise due to overheating of the machining area and may be defined as “arc machining” rather than “spark machining” (Ho and Newman, 2003).