EDM (Electrical Discharge Machining) removes metal with controlled electrical sparks rather than a cutting tool. The workpiece and an electrode are submerged in dielectric fluid; thousands of tiny discharges per second erode the metal. Because there is no cutting force and hardness doesn't matter, EDM machines hardened steel, carbide and exotic alloys and produces sharp internal corners and fine details a cutter can't reach.
The two main types are wire EDM, which threads a fine brass wire like a bandsaw to cut through-profiles, and sinker (ram) EDM, which burns a shaped electrode down into the work to form cavities — common in mold and die making.
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