ELECTRON DISCHARGE MACHINING TOOL

An electron discharge machining tool (10) for removal of conductive material from a workpiece such as a plug (28) in a nuclear steam generator tube (26) is an end effector connected to a remotely operated manipulator arm by a mount (56). A piston (47) drives a hollow conductive rod (44) with a graphite electrode cutter (30) in reciprocating motion through receptacle (14) having a restrictive drain (37) and containing deionized water. The reciprocation of rod (44) is controlled by power supply (50) sensing the electrical potential and signalling valve (48) which controls hydraulic flow in conduits (54a, 54b) communicated to opposite sides of the piston (47). A TV camera (32) and a light (34) mounted behind a lens (36) are used to monitor the machining.