Superconducting Ba2YCu3O7-δ ceramics were machined by the electric discharge machining (EDM), using a square-wave-pulse discharge circuit. To maintain stable discharge during machining, a small duty factor, less than 2% depending on the pulse width and the peak current value, was required. A typical machining rate was 70μm/min for a machining electrode of 5mm radius, a puls width of 10μs, and a peak current value of 5.2A. A small discharge energy was preferable to make the inner region of the sample free from damages by the heating effect of the electric discharge. The critical temperature of the Ba2YCu3O7-δ ceramics 50μm below the machined surface was almost identical with that of the bulk.
