Material Selection for EDM
EDM works on any electrically conductive material. But "works" and "works well" are different things. Cut speed, surface finish, wire consumption, and cost all vary by material.
Tool Steels
D2, A2, S7, M2, H13 — these are the materials EDM was built for. They cut predictably in both hardened and annealed states. D2 is the single most common material across wire and sinker work. It holds tolerance well and produces a manageable recast layer.
The key consideration is the heat-affected zone. EDM creates a recast layer 0.0002"–0.001" deep depending on power settings. For most tooling applications this is acceptable. For fatigue-critical work, remove it by polishing or light grinding.
Carbide
Tungsten carbide is one of the best arguments for EDM's existence. Conventional machining of carbide destroys tooling, is slow, and tolerances are hard to hold. Wire EDM cuts carbide cleanly at 40–60% of the speed of tool steel. Wire consumption is higher because carbide is abrasive to the wire. Budget accordingly — carbide jobs cost 40–80% more per inch than equivalent geometry in tool steel.
Stainless Steel
300-series stainless (304, 316) cuts roughly 20% slower than carbon steel due to lower thermal conductivity. Stainless is prone to micro-cracking in the recast layer if power settings are too aggressive — a good shop dials back power and takes lighter skim passes. 17-4 PH machines similarly to tool steel.
Aluminum
Aluminum EDMs fast — 2–3x the speed of steel — because of high thermal conductivity and low melting point. The challenge is a rough, pitted surface on the first cut that requires more skim passes to clean up. The recast layer is also thicker than on steel for equivalent settings.
Inconel & Nickel Superalloys
Increasingly common for aerospace gas turbine components. EDM doesn't care about hardness or toughness — it just erodes. Cut speeds are 30–50% of steel, wire consumption is high, surface finish tends rougher. But the alternative is often "there is no alternative," which is why EDM gets the work.
Titanium
EDMs well but requires careful flushing due to a tendency to produce a thick recast layer. Medical and aerospace implant work frequently specifies wire EDM for titanium components where conventional machining would distort thin walls.
PCD (Polycrystalline Diamond)
Can only be shaped by EDM. If you're making PCD cutting tools or wear components, EDM isn't an option — it's the only option.
Material Comparison Matrix
| Material | Cut Speed | Surface | Wire Use | Cost Impact |
|---|---|---|---|---|
| D2 Tool Steel | Baseline (1.0x) | Excellent | Normal | Baseline |
| A2 / S7 / H13 | 0.95–1.05x | Excellent | Normal | Same |
| M2 High Speed | 0.85x | Very Good | Slightly Higher | +10–15% |
| Tungsten Carbide | 0.4–0.6x | Good | High | +40–80% |
| 304/316 Stainless | 0.8x | Good | Normal | +10–20% |
| Aluminum 6061 | 2.0–3.0x | Rough first cut | Low | –20–30% |
| Inconel 718 | 0.3–0.5x | Fair | Very High | +60–100% |
| Titanium 6Al-4V | 0.5–0.7x | Good | High | +30–50% |
Material cost impacts are multiplicative with tolerance requirements. Carbide at ±0.001" is 40–80% more than D2 at ±0.001". Carbide at ±0.0002" could be 2–3x the cost of D2 at ±0.001" because you're stacking slower cut speed with additional skim passes. When quoting exotic materials, get the material to the shop early so they can run test cuts if needed.
Working with a challenging material?
Tell us the material and tolerance. We'll connect you with a shop that's cut it before.