A cartridge assembly for a travelling wire electrode electrical discharge machining apparatus includes a cartridge barrel having a first open end and a second open end, and a wire guide mounted in the first open end of the cartridge barrel for guiding the wire electrode. A current pick-up holder is mounted in the second open end of the cartridge barrel and includes an index pin for engagement with a current pick-up. A current pick-up is provided for delivering current to the wire electrode, the current pick-up being mounted in the pick-up holder and including a longitudinal bore for engagement with the wire electrode. The current pick-up includes a first end and a second end, with a tool engagement portion located at the first end of the current pick-up for engagement of a tool to rotate the current pick-up relative to the current pick-up holder. An index pin receiving portion is located at the second end of the current pick-up for receiving the index pin of the current pick-up holder. The current pick-up can be rotated through successive indexed orientations to expose new unworn inner peripheral surfaces of the bore of the current pick-up to extend the life of the current pick-up.