What is Electrical Discharge Machining?

Electrical Discharge Machining (EDM) is a manufacturing process that allows for the creation of complex shapes made from very hard materials and to very tight tolerances
Also called spark machining or spark erosion, EDM uses electrical discharges (sparks) to remove material from a workpiece.
The tool and the workpiece do not ever actually make contact, but they are placed into a dielectric (insulating) liquid. Voltage builds up in between the tool and the workpiece until the electric field becomes stronger than the dielectric.
When it does, a spark channel forms, and the intense temperature and pressure cause a small amount of material to be vaporized and eroded from the workpiece.