When a conductive medical-device part has a narrow slot, internal form or small opening, a note that only says "use EDM" does not finish the process decision. Wire-cut, sinker and small-hole EDM are separate routes. The useful choice depends on the feature, where it sits and how an electrode can reach it. Making that distinction before an RFQ keeps the quote centered on the actual constraint instead of treating the whole part as an EDM job.

Start with the feature, not the process name

First confirm that the specified material is electrically conductive, because that is the material boundary for the EDM processes Lab Ready lists. Then isolate the feature that conventional milling or turning does not address efficiently. The overall part may still begin with CNC machining, with EDM reserved for a narrow slot, internal form, small opening or hardened feature that earns the additional operation.

For that feature, mark whether it passes through the workpiece or stops inside it, identify the available approach direction, and state the required tolerance, surface condition and inspection record. Those inputs matter more than adding a broad EDM note to the drawing. The earlier guide to choosing between EDM and precision grinding addresses the process-family decision; the next step is selecting the EDM route that fits the geometry.

Use wire EDM when the wire has a workable path

Wire EDM uses a continuously fed wire electrode to cut a narrow path through conductive material, as shown in Makino's EDM process overview. That makes the wire route a candidate for through-profiles, slots and contours where the wire can enter from an edge or through a planned start opening. The drawing should make the complete cut path understandable rather than showing only the final profile.

Before quoting, identify the stock condition, the entry or start-hole strategy, the profile depth and the features used to locate the cut. Do not assume that every internal shape is automatically a wire operation. If the electrode cannot pass through the required path, the access condition points toward another route.

Use sinker EDM when a shaped electrode must form the feature

Sinker EDM uses a shaped electrode in a dielectric bath to remove material from a conductive workpiece. It becomes a quoting candidate when the required form is blind, recessed or otherwise cannot be produced by passing a wire through the part. The electrode and the part feature must therefore be considered together.

Show the complete internal form, depth, corner requirements, approach direction and surrounding geometry. Those details let the reviewer distinguish a genuine sinker feature from one that remains better suited to milling, wire EDM or another operation. This feature-specific approach also supports the narrow and difficult-to-access geometry described for spinal device and instrument components.

Use small-hole EDM when the opening is the primary feature

Small-hole EDM uses a rotating tube electrode with flushing to produce small, deep openings in conductive materials. Lab Ready lists it for small precision holes, but the listing is not a universal size or tolerance promise. The drawing still needs the hole diameter, depth, location, material condition and acceptance requirement for review.

A small opening may also support a later wire-EDM path, but that sequence should be confirmed from the actual geometry. Treat the start feature and the final cut as separate RFQ inputs when both matter. For instrument parts, also identify the working interface around the opening so the manufacturing and inspection plan can follow the feature's function rather than its diameter alone.

Put five decision inputs on the RFQ

  1. Material and condition: state the exact conductive alloy and any relevant condition or hardness.
  2. Feature type: distinguish a through-profile, blind internal form or small opening.
  3. Access: show the approach direction, cut path and any planned start opening.
  4. Acceptance: identify the tolerance, surface requirement and datum relationship that control the feature.
  5. Inspection: name the feature that needs a documented result instead of requesting a blanket report for the whole part.

Engineering Takeaway

Wire, sinker and small-hole EDM are three different routes, not one "use EDM" note: wire EDM cuts through-profiles and slots where a wire has a clear path, sinker EDM forms blind or recessed features with a shaped electrode, and small-hole EDM produces small, deep openings with a rotating tube electrode. Put the feature type, access direction, tolerance and inspection requirement on the RFQ so the actual constraint — not the part as a whole — drives the process choice.

Use the medical-device RFQ checklist to assemble the surrounding quantity, finish and delivery inputs. When the EDM candidate feature is marked on the drawing, send it through the RFQ form with its material, access condition and inspection need so the manufacturing route can be reviewed.