What is spark EDM used for?

Burning shaped cavities, deep ribs and sharp inside corners into hardened steel, mainly for injection moulds, die-casting dies and forging dies.

Copper or graphite electrodes?

Graphite machines faster and wears less on large electrodes; copper gives finer finishes on small details. Shops choose by the job.

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Spark EDM machine (die sinker)

Also called: die sinking EDM, sinker EDM, spark erosion machine, ram EDM, EDM machine

A spark EDM (die-sinking) machine burns a cavity into a metal part with a shaped electrode, usually copper or graphite, using electrical sparks in oil. It makes blind pockets, sharp inside corners, ribs and textures in hardened steel that milling cannot, mainly for moulds and dies.

Quick facts

Electrode: Copper or graphite, machined to the shape of the cavity
Works on: Any conductive metal, including hardened tool steel and carbide
Typical accuracy: About ±0.01 mm
Finish: From rough to fine; also textured (VDI) finishes for moulds
Fluid: Dielectric oil
Cost driver: Electrode making and burning time

Typical work

Mould cavities, deep ribs and sharp internal corners
Die-casting and forging die details
Blind pockets and shapes in hardened steel
Mould textures (spark finish)
Small precise holes and slots where wire cannot reach

Spark EDM or wire cut?

	Spark EDM	Wire cut EDM
Tool	Shaped electrode	Moving wire
Makes	Blind cavities and pockets	Through profiles
Best for	Moulds and die cavities	Punches, dies, slots

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Questions

What is spark EDM used for?: Burning shaped cavities, deep ribs and sharp inside corners into hardened steel, mainly for injection moulds, die-casting dies and forging dies.
Copper or graphite electrodes?: Graphite machines faster and wears less on large electrodes; copper gives finer finishes on small details. Shops choose by the job.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 8 October 2026.