An electron discharge machining (E.D.M.) tool combination (10) is useful for removal of an installed nuclear steam generator tube plug of conductive material. A conductive wand shaft (12) connected to an E.D.M. voltage source (16) is movably mounted in a housing (20) and insulated from the housing. An inlet adapter (26) is mounted on the wand end and connected to a source (30) of deionized and demineralized water to provide a dielectric fluid and removed material carrier. A hollow electrode (40) is mounted on a hollow extension (36) beyond the end of the wand and inlet adapter (26) in fluid communication with the adapter for movement with the wand relative to the housing. A drive plate (72) is moved by means of a ball nut (74) along a roller ball shaft (76) which is rotationally driven by a motor (82) in the housing (20). The drive plate (72) reciprocates the wand and electrode for E.D.M. operation. The wand position can be monitored remotely by a signal from a potentiometer (92) with a tap (90) movable with the wand.
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