by electrical discharges

Full Title

Perforating; Punching; Cutting-out; Stamping-out; Apparatus therefor (perforating by laser beam B23K26/00; subjecting the grinding tools or the abrading medium to vibration, e.g. grinding with ultrasonic frequency, B24B1/04; perforating by sand-blasting B24C; punching cards or tapes for statistical and record purposes G06K1/00) > Perforating by non-mechanical means, e.g. by fluid jet > by electrical discharges