What is EDM (electrical discharge machining)?

EDM removes conductive metal with carefully controlled electrical sparks rather than a conventional cutting edge.

EDM erodes metal with controlled electrical sparks, cutting hardened steels and intricate shapes that ordinary tools cannot reach. It is common in mold-making, aerospace parts, and medical instruments.

Why shops choose a spark over a blade

A cutting tool has to be harder than the material it cuts, and it pushes against the part as it works. EDM sidesteps both problems. Because the spark never physically touches the metal, there is almost no cutting force, so delicate walls and tiny features are not bent or stressed. And because it erodes material electrically, it can shape steel already hardened — metal that would dull or defeat an ordinary cutter.

The details

1. It only works on conductive materials. The workpiece and the electrode form an electrical circuit, so EDM suits metals like steel, titanium, and carbide, but not plastic, wood, or glass.
2. Two main types cover most jobs. Wire EDM threads a thin, continuously fed wire through the part to cut precise profiles, while sinker EDM uses a shaped electrode to burn a matching cavity, such as a mold.
3. The gap matters. Sparks jump across a tiny gap filled with dielectric fluid, which insulates until the voltage builds, then flushes away the microscopic debris each spark creates.
4. It is precise, not fast. EDM can hold very tight tolerances and cut sharp internal corners a spinning tool cannot reach, but it removes material slowly compared with milling.