Wire vs sinker
EDM removes material using controlled electrical discharges in a dielectric fluid instead of a cutting tool. Because there is no mechanical cutting force, it is well suited to electrically conductive materials, including hardened tool steels, carbide and other difficult-to-machine alloys.
A fine charged wire follows your profile through the full thickness of the part, cutting intricate 2D and tapered shapes with very sharp internal corners and a clean edge. Choose it for through-cut profiles, dies, gears, splines and fine 2D detail in hardened steel.
A shaped graphite or copper electrode is sunk into the workpiece to burn its mirror image — producing blind cavities, deep ribs, fine slots and sharp internal detail no rotating tool can reach. Choose it for mould and die cavities, blind features and 3D detail.
Often combined on one part - for example a sinker-burned cavity finished with wire-cut profiles, or a start hole drilled for a closed wire path. If you already know which process you need, tell us; if not, we'll recommend the route.
Applications
Part types and features that benefit from non-contact machining—especially hard, intricate or delicate components made from electrically conductive materials.
Hardened press dies, mould cavities and forming tools machined after heat treatment, with small internal radii and fine details that are difficult to produce by conventional cutting.
Spur gears, splines, cams and serrated profiles cut in conductive materials, with controlled geometry and minimal mechanical cutting force.
Narrow slots, internal keyways and fine apertures with small internal radii that may be difficult to produce using conventional rotary tools.
Capability boundary
Indicative limits across our wire and sinker EDM work. Your geometry, material and finish set the achievable numbers — confirmed against your drawing at quoting.
| Capability | Wire EDM | Sinker EDM |
|---|---|---|
| Typical tolerance | From ±0.005 mm* | From ±0.01 mm* |
| Typical surface finish | Down to ~Ra 0.2 μm | Matte to polished, depending on electrode and finish strategy |
| Internal corner radius | Limited by selected wire diameter | Limited by electrode geometry |
| Typical slot / kerf | Typically ~0.2–0.3 mm | Determined by electrode size |
| Typical workpiece thickness | Up to ~300 mm (machine dependent) | Suitable for deep blind cavities and ribs |
| Taper / draft | Controlled tapered profiles | Draft produced by electrode design |
| Feature capability | Start holes, fine profiles, narrow slots | Blind cavities, ribs, engraving, text |
| Typical applications | Through profiles, dies, gears, precision 2D shapes | Cavities, mould details, slots, keyways |
Values are representative. Specific tolerances and finishes are agreed and confirmed against your drawing at DFM review.
Process control
Result quality on an EDM part is decided before the first spark — in process choice, setup and electrode planning — and confirmed by how the surface and critical features are checked.
We confirm wire vs sinker (or a combination) against the geometry, hardness and feature detail before quoting — the single biggest driver of cost and outcome.
Datums and fixturing are planned so profiles, cavities and existing machined features stay aligned — critical when EDM follows prior milling or heat-treat.
For sinker work we plan electrode count, material and wear allowance — typically a roughing and a finishing electrode — to hold form and finish in the cavity.
Spark energy is tuned to manage the recast layer and heat-affected zone, with skim passes where a part is fatigue- or finish-critical.
Where needed, EDM is followed by polishing, grinding or stoning — so sealing faces, sliding surfaces and cosmetic detail meet their final spec.
Critical corners, slot widths and profiles are measured — optical, CMM or gauge — and reported against your drawing, not assumed from the program.
Surface integrity
EDM can leave a recast layer and heat-affected zone on the machined surface. Their extent depends on the material, discharge parameters and finishing strategy. For many applications, the as-EDM surface may meet the confirmed requirements. For fatigue-, sealing- or fracture-sensitive features, surface integrity should be reviewed and managed accordingly.
We treat EDM as a shaping process—not always the final surface step—and plan any required finishing and inspection accordingly.
Metals we EDM
EDM cuts any conductive metal regardless of hardness — which is exactly why it's reached for on the materials conventional tools struggle with.
EDM cuts any electrically conductive metal regardless of hardness; non-conductive materials can't be EDM machined. Send your material and condition and we'll confirm feasibility and any surface considerations.
Process choice
EDM is slower than conventional cutting, so it earns its place when hardness, sharp internal geometry or delicate sections make a rotating tool the wrong choice. The question isn't "is EDM capable" — it's whether your part genuinely needs it.
Not sure? Send your model and we'll advise whether EDM, milling, turning or grinding is the right route at DFM review.
Common questions
When the part is hardened, has sharp internal corners a tool radius can't leave, or is a thin profile that would distort under cutting force. Wire EDM cuts a through-profile in any conductive metal regardless of hardness — ideal for dies, gears and fine 2D detail — though it's slower than milling on soft, open geometry.
For blind cavities, deep ribs, fine slots and 3D internal detail that a wire can't reach through the part — the go-to for injection-mould and die cavities. A shaped electrode burns its mirror image into the surface.
Hardened tool steels, tungsten carbide, superalloys (Inconel, Hastelloy), titanium and stainless — the materials that are hardest to cut conventionally. Any electrically conductive metal can be EDM machined; non-conductive materials cannot.
On wire EDM, down to the wire radius (around 0.1 mm); on sinker EDM, down to the electrode radius. Far sharper than any milling cutter can leave — confirmed against your drawing.
Down to roughly 0.2 µm Ra on wire EDM, and matte-to-polished on sinker depending on the electrode and settings. Spark erosion leaves a thin recast layer, which skim passes reduce where finish is critical.
Often not — EDM finishes are acceptable for many parts. Where a surface is sealing-, sliding-, cosmetic- or fatigue-critical, we follow EDM with polishing, grinding or stoning to meet the final spec.
A 2D drawing (DXF / DWG) for wire profiles or a 3D model (STEP / IGES) for sinker work, plus material and hardness, heat-treat sequence, critical corners/slots/depths, surface and tolerance priorities, and quantity. A sketch is enough to start.
Send your DXF, DWG, or STEP files along with your project requirements. Our engineering team will review your wire EDM or sinker EDM requirements, assess manufacturing feasibility, and provide quotation and DFM feedback based on your project.
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