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If you design miniature metal parts, one of the first questions you will ask a machining partner is: how small can you go? When it comes to small wire EDM, the short answer is that a well-equipped shop can produce through-holes down to about 0.07 mm in diameter, slots only slightly wider than a human hair, and internal corner radii of roughly 0.02 to 0.05 mm. The long answer, which matters far more when you are specifying a drawing, is that the minimum size depends on the wire diameter, the spark gap, the workpiece thickness, and the material itself. This article breaks down each factor so you can design micro parts that are actually manufacturable.
Wire EDM cuts with a continuously fed charged wire that never touches the workpiece. Material is removed by electrical sparks jumping across a tiny gap filled with dielectric fluid. Because of this, the minimum feature size is governed by a simple geometric relationship:
Minimum cut width = wire diameter + 2 x spark gap
Standard wire EDM work uses brass wire of 0.20 mm or 0.25 mm. Fine-wire machines go much smaller: 0.10 mm, 0.07 mm, 0.05 mm, 0.03 mm, and even 0.02 mm wires are commercially available for micro machining. The spark gap (also called overcut) typically ranges from about 0.005 mm to 0.05 mm per side, depending on the power settings, the number of skim passes, and the material. Put those together, and the practical limits look like this:
| Feature | Typical Minimum (Fine-Wire EDM) | What Limits It |
|---|---|---|
| Smallest through-hole / slot width | Approx. 0.05 - 0.08 mm | Wire diameter plus spark gap on both sides |
| Minimum internal corner radius | Approx. 0.02 - 0.05 mm | Wire radius plus spark gap; the wire cannot cut a sharper inside corner than its own radius |
| Thinnest wall or web between two cuts | Approx. 0.05 - 0.10 mm | Vibration, flushing pressure, and part rigidity, not the wire itself |
| Smallest standalone part | Sub-millimeter (micro gears, pins, nozzles) | Workholding and handling rather than cutting capability |
At ANOK, our Sodick wire EDM machines routinely hold the smallest hole diameter at 0.07 mm, with tolerances as tight as 0.003 mm and perpendicularity of 0.001 to 0.002 mm. Those numbers represent the practical, repeatable end of the spectrum rather than a one-off laboratory result.
For through-holes, the floor is set by the thinnest wire the machine can reliably tension and thread. A 0.02 mm wire with a conservative spark gap yields a hole of roughly 0.04 to 0.06 mm in ideal conditions; in production, most shops quote 0.07 to 0.10 mm as the dependable minimum. Two caveats are worth remembering:
Designers often focus on hole size and forget the other three limits that define a micro part:
The narrowest slot equals the kerf: wire diameter plus twice the overcut. With a 0.03 mm wire and a finishing spark gap, slots around 0.05 to 0.06 mm are achievable, which is why wire EDM is the standard process for micro-slots in carbide punches, injector components, and precision springs.
A traveling wire is round, so a perfectly sharp internal corner is physically impossible. The minimum internal radius is roughly the wire radius plus the spark gap. With a 0.02 mm wire, that works out to about 0.02 to 0.03 mm, which is far sharper than any milling cutter can reach. If your design needs a truly square internal corner, plan for a matching relief or a two-piece assembly instead.
Below roughly 0.05 to 0.10 mm, a thin wall starts to deflect under flushing pressure and spark forces, and accuracy suffers even though the wire itself is capable of the cut. Material choice matters here: a rigid material like tungsten carbide holds a thin web far better than a soft copper alloy.
Wire EDM only cuts electrically conductive materials, but within that rule it is remarkably indifferent to hardness. Hardened tool steel, titanium, tungsten carbide, copper, and graphite all cut without cutting forces, which is exactly why the process can hold micron-level features: there is no tool pressure to push the part or the wire off course. A few practical guidelines:
Sub-0.1 mm features are not a party trick; they show up in real production parts across several industries we serve. In fiber-optic connectors, brass and stainless steel guide pins are produced at 0.6985 mm diameter with roundness held to a tenth of a micron. In medical devices, fine slots and holes in titanium and 316L stainless components must stay burr-free to be safe inside the human body. In precision tooling, micro-slots in carbide punches and dies define the shape of stamped electronics terminals. In every one of these cases, the minimum manufacturable size was the deciding factor in choosing wire EDM machining over milling, grinding, or laser cutting.
Not every wire EDM machine can run a 0.02 mm wire; it requires fine-wire threading hardware, precision tension control, and high-resolution axis drives. When you evaluate wire EDM services for miniature parts, ask three questions: What is the smallest wire diameter the shop runs in production? What tolerance and perpendicularity do they guarantee at that size, not just claim on a capability sheet? And how do they inspect the finished micro features, since measuring a 0.07 mm hole is a discipline of its own?
At ANOK Precision Manufacturing, our wire EDM department runs Sodick machines and holds tolerances down to 0.003 mm with the smallest hole diameter at 0.07 mm, on parts up to 500 mm in diameter and 400 mm thick. Because wire EDM sits in the same ISO 9001:2015 certified factory as our CNC milling, turning, and grinding departments, micro features can be combined with conventionally machined geometry in a single, accountable workflow. If you have a drawing with features near these limits, send it to our engineering team for a free DFM review, and we will tell you exactly what is achievable before you commit to production.