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Sinker EDM Machining Services

Six sinker EDM machines for blind cavities, square internal corners, deep keyways and features that have no through-path for a wire. Electrodes designed and machined in-house, so lead time does not depend on anyone else.

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What it is

Burning a shape, not cutting it

Sinker EDM — also called die sinking or ram EDM — pushes a shaped copper or graphite electrode into the workpiece under a dielectric fluid. The spark erodes the exact negative of the electrode. Because nothing rotates and nothing touches, we can produce a square internal corner with no radius at all, sink a cavity into fully hardened steel, and reach into places where no cutter has clearance.

Machining bay at GY Machining where sinker EDM electrodes are milled
Electrodes are milled here, next to the EDM bay
Machine and process data

What we can sink

  • Sinker EDM machines6
  • Max workpiece500 × 350 × 250 mm
  • Achievable tolerance±0.01 mm
  • Internal cornerSquare — no radius required
  • Surface finishRa 0.4 – 3.2 µm
  • Max depthUp to 150 mm
  • ElectrodesCopper and graphite, made in-house
  • Material hardnessNo limit

A finer finish costs more time, not more money per part — tell us the Ra you actually need and we will quote the settings that reach it without over-polishing.

Typical work

What customers use our sinker EDM for

Blind cavities

Pockets with a closed bottom, where a wire has no way in and a cutter cannot reach the corner.

Square internal corners

Keyways, hex and square broach forms, and splines with no corner radius.

Injection mould cores and cavities

Detail sunk into hardened tool steel after heat treatment.

Deep ribs and slots

Narrow features deeper than any end mill of that diameter can cut without chatter.

Text, logos and serial marks

Engraved into hardened surfaces where laser marking will not survive the process.

Broken tap and stud removal

Eroding out a seized tool without damaging the thread around it.

Materials

Materials we sink

Any conductive material, hardened or annealed. Tool steels are the everyday work; we also sink stainless, titanium and carbide.

Tool steel D2 / SKD11H13S7A24140Stainless 303 / 304 / 316L17-4 PHTitanium Gr.5Aluminium 6061 / 7075Copper C110Tungsten carbideBeryllium copper
Good to know

Before you send the drawing

Do I need to supply the electrode?
No. We design and machine copper or graphite electrodes here, on the same machining centres that cut your part. That is one less supplier in your chain and one less thing to wait for.
Wire EDM or sinker EDM — which do I need?
If the feature goes all the way through the part, wire EDM is faster and cheaper. If it is blind — a pocket with a floor, a deep rib, a cavity — it has to be sinker. Send the drawing and we will tell you which we would use and why.
How square can an internal corner really be?
Truly square. The corner takes the shape of the electrode, so there is no tool radius at all. If the drawing calls out a sharp corner, we can give you one; a milling cutter never can.
What surface finish comes off the machine?
Between Ra 0.4 and 3.2 µm depending on how we set it. A mirror-fine finish takes more machine hours, so we quote the finish your drawing asks for rather than the finest we can do.
Related

Often ordered together

Wire EDM

Through-profiles, sharp corners and hardened plate, cut with a wire. Wire EDM →

CNC Milling

The part and its electrodes are milled on the same floor, days before they meet. CNC milling →

Surface finishing

Polishing, plating and coating after the cavity is sunk. Surface finishes →

Send the drawing. You will have a price and a lead time in 16 hours.

STEP, IGES, X_T, DWG, DXF or PDF. Metric or inch. No minimum order.

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