In this video, I demonstrate a Small Hole EDM constructed from a bastardized solenoid type doorbell, a desk lamp and a 24v 1.8A electric bicycle battery charger. In most EDM systems direct physical contact is not made between cathode and anode, and a dielectric fluid is used to facilitate the erosive process of arcing. The fluid also carries away any swarf. In this particular device, contact is made briefly to energize the coil of the solenoid, which retracts the electrode (tool) creating the spark gap which is what causes the arcing, depolarization of material and subsequent erosion. The erosion conforms to the shape of the die/tool/electrode, with slightly enlarged diameters compared to the tool.
