An apparatus includes an electrode assembly comprising a carriage having a plurality of electrode holders, the electrode holders being respectively configured to detachably receive a plurality of electrodes, the electrodes include a plurality of first electrodes and a plurality of second electrodes. The first electrodes are configured for rough machining a workpiece by electric discharging or wire electric discharging to remove material from the workpiece, the second electrodes are configured for finish machining the rough machined workpiece by electric discharging to remove material from the rough machined workpiece.