What is EDM Machining and When Do You Need It?

How EDM Works

Electrical Discharge Machining removes material through a series of rapid electrical sparks between the tool (electrode) and the workpiece. Because there's no physical cutting force, EDM can machine extremely hard materials and create features that conventional machining cannot.

Wire EDM

Uses a thin wire electrode to cut through the workpiece like a bandsaw. Ideal for:

• Complex 2D profiles in hardened steel
• Tight tolerance slots and keyways
• Precision splitting with minimal material removal (0.020" kerf)
• Small internal features with sharp corners

Sinker EDM

Uses a shaped electrode that 'sinks' into the workpiece. Ideal for:

• Complex 3D cavities
• Blind holes with specific shapes
• Micro-features

Cutting "Uncuttable" Materials

This is where Wire EDM has no competition. Because material removal is electrical — not mechanical — hardness is completely irrelevant. The only requirement is that the material conducts electricity. If it does, the wire cuts it, regardless of how hard it is.

Solid carbide is the best example. A solid carbide end mill, a carbide insert, a carbide wear pad — Wire EDM cuts through them without hesitation. You can section a solid carbide tool, modify its geometry, or cut a profile into it. No conventional milling, grinding, or sawing method gets near solid carbide without destroying the tool in the process.

Plasma-sprayed carbide overlay is another case that comes up regularly in oilfield work. Many downhole and surface components have tungsten carbide or chrome carbide deposited by plasma spray for wear resistance. Once that overlay is on the part, it is essentially unmachineable by conventional means — carbide overlays will destroy HSS and carbide cutting tools almost immediately. Wire EDM cuts through the overlay cleanly and precisely, with no tool wear, because there is no tool making mechanical contact.

If you have a component with carbide overlay that needs a slot, a profile, or a dimensional modification — Wire EDM is often the only viable method.

Achievable Tolerances

• Wire EDM: ±0.0002" achievable
• Sinker EDM: ±0.0002" typical
• Surface finish: 8–16 Ra typical