Sources and scope for this page: Industry convention — no single governing standard (conventional usage, definitions vary between sources), covering the definition of edm (electrical discharge machining). No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. How sources, methods and updates are recorded.
Definition
EDM cuts any electrically conductive material regardless of hardness, which makes it the standard process for hardened tool steel, complex internal profiles and sharp internal corners that no milling cutter can reach.
It leaves a recast layer — a thin surface of re-solidified metal with different properties from the bulk, often containing microcracks. Where fatigue life matters the recast layer must be removed by a finishing pass or by polishing.
Common misuse
Using an EDM'd surface as a finished surface on a fatigue-critical part. The recast layer is a crack initiation site.