The principle of EDM is corrosion removing the metal based on the electro erosion which happens when the implusive spark of the tool electrode and the workpiece discharges, and processing the workpiece to fullfil the planed demands on the workpiece's size shape, surface quality and etc. As it directly uses electric energy and heat energy to carry non-contact processing on workpieces, it can work on materials as long as they have good electric conductivity, such as some new materials that some machines can't process.

EDM tool is the special maching tool working based on that principle. It is also called electric corrosion machining tool, and mainly used to process kinds of high-hardness materials such as hard alloy, chilled steel and etc, and molds and spare parts with complicated shapes, and to cut, notch and remove tools broken in the holes of workpieces, such as drills, screw taps and etc.

There are EDM shaping machines, EDM cutting machines, EDM grinding machines and kinds of EDM machines for special uses such as processing small holes, screw ring gauge,profile hole nozzle plate and etc.