This is one of a pair of miniature punches and dies that could only be produced with the EDM process.
Both parts are extremely hard toolsteel ; over 60 Rockwell C.
The button is A-2 toolsteel hardened to 60-62 RC and still needs to be finish ground.
The openings are 0.0209″ wide.
This is the mating punch.
Die clearance is 0.0013″ total and the punches are 0.156″ long.
They were cut by wire EDM cutting an electrode, then sinker EDM cutting the punch profiles and orbiting the electrode to bring the punches to size.
This is a stainless steel tube that forms part of a needle biopsy instrument. The tubing is very thin…the wall is 0.004″ thick. The slots need square ends and must be precisely oriented around the tube. The slots must be bur-free since other parts slide in the tube. Despite its expense, EDM is the obvious processing choice for a part like this.
The slots are 0.015″ wide. There are six of them around the periphery of the tube which is just over 1.0 mm in diameter. The slots were cut using the sinker EDM by vectoring a six pronged electrode around the tube which was oriented standing up in the worktank. The tube is so flimsy that the first attempts resulted in deformation of the tube when it was clamped into the vee block even though the clamping was performed very gingerly.
Here is the electrode. It is made from copper tungsten which is the material of choice for electrodes that are fragile and must stand up to repeated use. This electrode material is quite difficult to machine on conventional equipment, but wire EDM cuts it very well. The two big flats cut into the body are reference surfaces for aligning the electrode when it’s used. This electrode has burned 6 tubes and still has a good bit of life in it.