Wire EDM vs. Sinker EDM
The most common question buyers ask. The answer is almost always straightforward once you understand what each process can and can't do.
Capability Comparison
| Factor | Wire EDM | Sinker EDM |
|---|---|---|
| Feature Type | Through-cuts and profiles | Cavities, blind holes, 3D shapes |
| Best Tolerance | ±0.0001" | ±0.0002" |
| Best Surface Finish | Ra 8 μin | Ra 8 μin (with orbiting) |
| Inside Corners | Wire radius (0.004"–0.006") | Electrode radius (very small) |
| Setup Cost | Lower (no electrode to make) | Higher (electrode fabrication) |
| Per-Part Cost at Volume | Linear with quantity | Decreasing (electrode amortized) |
| Unattended Operation | Excellent — lights-out capable | Good with tool changer |
| Typical Applications | Die sections, punches, gears, splines, extrusion dies | Mold cavities, forging dies, blind ribs, textures |
When to Use Wire EDM
Your feature is a through-profile — it goes all the way through the workpiece. Die openings, gear teeth, internal splines, extrusion die openings, stripper plate holes. If you can imagine pushing the shape through the block like a cookie cutter, wire EDM is your process.
When to Use Sinker EDM
Your feature is a blind cavity — it doesn't go through. Injection mold cavities, forging die impressions, blind keyways, rib details, textured surfaces. If the feature has a bottom, sinker is your process.
When You Need Both
Many tool and die jobs use both processes on the same workpiece. Wire EDM cuts the through-profiles, then sinker EDM adds the blind cavities and detail features. A shop that runs both processes in-house eliminates a handoff and holds tighter overall tolerances because there's no re-fixturing between shops.
If your project needs both wire and sinker EDM, find one shop that does both. Every time a part ships from one shop to another for additional operations, you lose time, risk damage, and accumulate tolerance stack-up from re-fixturing. A single shop running both processes controls the entire workflow and takes ownership of the final result. The best shops run both processes under one roof for exactly this reason.
Not sure which EDM process you need?
Send us your drawing and we'll recommend the right approach.