EDM Service
Resolute Precision Manufacturing coordinates electrical discharge machining (EDM) both wire EDM and sinker EDM for precision machined components requiring features that conventional cutting tools cannot produce. Thin slots in hardened steel, precise internal profiles, small-radius corners, and features in exotic alloys are all within the scope of EDM. We manage the process and deliver EDM-finished parts from a single purchase order. Request a QuoteWhat EDM Produces That Conventional Machining Cannot
Electrical discharge machining removes material by electrical sparks rather than cutting forces. This fundamental difference gives EDM a unique set of capabilities. First, EDM can machine any electrically conductive material regardless of hardness hardened D2 tool steel at Rc 60 machines as easily as soft aluminum by EDM. Conventional cutting tools deflect, chatter, and wear rapidly in hardened materials; EDM does not.
Second, EDM produces features with internal corner radii approaching zero slots as narrow as 0.004 inch, square inside corners, and contours with no minimum radius constraint. Third, EDM produces no cutting forces on the workpiece fragile thin walls and delicate sections can be EDM-machined without deflection or damage.
Our Services
Wire EDM vs. Sinker EDM
Two EDM processes serve different geometric requirements:
Wire EDM — a thin brass wire (typically 0.004″ to 0.012″ diameter) travels through the part, cutting a precise contour path programmed from the drawing. Used for through-cuts: gear profiles, extrusion dies, keyways in hardened parts, thin slots, and precise contour profiles
Sinker EDM (die sinker) — an electrode machined to the shape of the desired cavity is fed into the workpiece, eroding the cavity shape. Used for blind features: injection mold cavities, blind slots, recesses, and internal profiles that a wire cannot reach
Specifications
| Wire EDM | Brass wire (0.004″–0.012″ diameter) for through-cut profiles in any electrically conductive material; taper cutting available. |
| Sinker EDM | Custom copper or graphite electrodes for blind cavities, slots, and recessed features. |
| Material | Any electrically conductive material, including hardened steel, carbide, titanium, Inconel, copper, and aluminum. |
| Dimensional Accuracy | Wire EDM: ±0.0002″ on contours; Sinker EDM: ±0.0005″ on cavity features. |
| Surface Finish | Ra 8–32 microinch as-cut; finer finishes available with additional skim passes. |
| Minimum Slot Width | 0.005″ minimum through-slot; dependent on material and part geometry. |
| Minimum Inside Radius | Approximately equal to the wire radius (0.002″–0.006″) for Wire EDM. |
| Documentation | Process certifications and dimensional inspection reports provided with finished parts. |
| ISO | ISO 9001:2015; outside suppliers qualified under RPM’s approved vendor procedures. |
When to Specify EDM on Your Drawing
Specify EDM when your part has one or more of these requirements:
Features in hardened or heat-treated material that must be produced after hardening
Narrow slots or keyways where the width is too small for a standard end mill
Internal corners with near-zero radius requirements
Thin-wall features where cutting forces would cause deflection or damage
Exotic alloy features where tool wear in conventional machining is prohibitive
High-accuracy contour profiles that require ±0.0002″ or better dimensional tolerance
Frequently Asked Questions
Can EDM machine parts that have already been hardened?
Yes this is one of EDM’s primary advantages. Wire and sinker EDM machine hardened materials as readily as soft materials. Common practice is to rough-machine before hardening and EDM the precision features after eliminating distortion risk from post-hardening conventional machining.
What is the surface finish produced by wire EDM?
Wire EDM typically produces Ra 16–32 microinch in the as-cut condition. Multiple skim passes improve surface finish to Ra 8 or better. For bearing surfaces and sealing faces, we specify additional skim passes or subsequent grinding to meet finish requirements.
Can wire EDM cut through thick sections?
Yes. Wire EDM cuts through any thickness of conductive material that fits within the machine’s Z-axis travel. Common cut heights range from a fraction of an inch to 12 inches or more. Taper angle capability allows cutting of die and punch profiles with draft angles.
What lead time should I expect for EDM operations?
Typical EDM turnaround through our outside supplier network is one to two weeks for standard wire EDM work. Complex sinker EDM with custom electrode fabrication may require two to three weeks. We schedule EDM operations in parallel with other outside operations where possible to minimize total elapsed time.