Wire EDM cuts metal by generating controlled electrical discharges between a continuously fed thin wire electrode and the workpiece, eroding material along a programmed path. Since there's no mechanical cutting force involved, it's a solid option for hardened tool steels, fragile thin-wall sections, and internal profiles a milling cutter simply can't reach.

This Wire EDM guide covers when the process makes sense for your parts, the practical limitations you need to plan around, and the specific drawing callouts that help our engineers quote and program the job right the first time.

How Wire EDM Works

The wire and workpiece sit in a dielectric fluid bath, separated by a precise gap. The machine fires rapid electrical discharges that vaporize microscopic chips of material, while the wire feeds continuously so a fresh electrode surface is always in the cut zone. The path is CNC-controlled, so you get repeatable geometry without tool deflection.

The workpiece has to be electrically conductive—that's non-negotiable. Tool steels, stainless grades, copper alloys, aluminum, and most conductive hard alloys cut fine. Plastics, ceramics, and other nonconductive materials won't work with standard Wire EDM.

Where Wire EDM Makes Sense

Complex profiles: narrow slots, internal contours, and intricate openings can be cut without needing a rotating tool to fit the feature.
Hardened workpieces: you can often wire-cut after heat treatment, which avoids the headaches and cost of machining hardened stock conventionally.
Zero cutting force:Thin walls and small features aren't subject to milling cutter loads, but you still need to manage thermal effects and fixturing deflection to hold your tolerances.
Tooling components:Punches, dies, inserts, and gauges all benefit from precise profile cutting to maintain edge geometry and fit.
Sharp internal detail:Wire EDM gives you a much tighter internal radius than a typical end mill, limited only by wire diameter and the discharge gap.

Start Holes and Closed Profiles

For a closed internal opening, the wire has to enter through a start hole first. That hole can be drilled conventionally or via small-hole EDM. You'll want to plan its position, diameter, and relation to the finished contour early in the process.

An open external profile can often be approached from the edge, but you need to control the cut-off section so it doesn't shift, bind the wire, or mar the finished surface at the end of the cut.

Kerf, Corner Radius and Taper

The programmed path accounts for wire diameter plus the discharge gap, which together set the effective kerf. Internal corners can't be perfectly sharp; the minimum radius depends on the wire size and process parameters you're running.

Wire EDM can also cut controlled tapers on suitable geometry. If the top and bottom profiles differ, send both contours and clearly mark the reference height. Large tapers, thick stock, or abrupt profile changes may need extra process review before we quote.

Accuracy, Surface Finish and Skim Cuts

The first cut removes the bulk of the material. One or more skim cuts then refine size and surface finish using lower discharge energy. Each additional pass adds machine time, so specify tolerances and finish based on what the part actually needs to do.

Accuracy depends on workpiece thickness, flushing, thermal stability, wire condition, feature geometry, and how the part is fixtured. A tight tolerance on one functional profile is not the same as applying that tolerance to every cut edge across the board.

Material and Heat-Treatment Considerations

Even though cutting forces are low, the electrical discharge creates a thin thermally affected layer on the surface. How much that matters depends on the material and application. For critical tooling, fatigue-sensitive parts, or special surfaces, you'll want a defined skim-cut strategy, polishing, or another secondary operation.

Heat treatment can also relieve stress and move the blank. It's worth discussing whether rough machining, stress relief, hardening, and final wire EDM should happen in a specific sequence to hold your final dimensions.

Information to Put on the Drawing

Material grade, condition, and heat-treatment status.
Finished thickness and the reference face.
Profile tolerance and how it ties back to the hole pattern or datum structure—this is critical for the machinist to hold the part in the right frame of reference.
Internal corner radii and any relief features—these dictate whether we can use standard tooling or if we need custom ground electrodes and wire paths.
If there's a taper angle or the top and bottom profiles differ, spell that out—it changes how we program the wire path and whether we need a 4-axis setup.
Surface finish, recast layer, or polishing requirements—only call these out if they actually affect function, because they add cycle time and cost.
Let us know the quantity and whether this is a prototype, a tooling component, or a recurring production part—that determines how we approach the job and quote it.

Wire EDM or CNC Milling?

CNC milling is usually the better fit for open pockets, flat faces, and features you can reach with a rotating tool. Wire EDM becomes the right call when you're working with hardened or conductive material, the profile is a through-cut, you need tight internal corners, or you want to avoid cutting forces altogether. A lot of parts end up using both processes—mill the bulk, then wire the critical profile. is often efficient for open pockets, faces and accessible three-dimensional features. Wire EDM becomes attractive when the material is conductive and hard, the profile is through-cut, internal radii are small or cutting force must be minimized. Many components use both processes.

Frequently Asked Questions

Can Wire EDM cut any metal?

It handles most conductive metals and alloys, but we need to check conductivity, thickness, heat treat condition, and what the part has to do in service before we commit to the process.

It can process many metals and conductive alloys, but conductivity, thickness, heat treatment and application requirements should be reviewed before selecting the process.

Does Wire EDM need a start hole?

If you're cutting a closed internal contour, yes—we need a start hole to thread the wire through the workpiece before the cut begins.

A closed internal contour normally requires a start hole so the wire can be threaded through the workpiece.

How can I receive an accurate quotation?

Send us the CAD profile, print, material grade, thickness, heat treatment, quantity, tolerances, and surface finish requirements. Balford will review the project against its Wire EDM service and get back to you with a firm quote.

Provide the CAD profile, drawing, material, thickness, heat treatment, quantity, tolerance and surface requirement. Balford can review the project against its Have a precision profile to manufacture? Send the drawing to Balford for process review..

Wire EDM Machining Guide for Precision Metal Parts