Abstract: A workpiece (1) is clamped onto a compound rest table (5) and machined by a tool electrode (2) running tensioned between two electrode guides (10, 11). A container (18) holds the working liquid into which a working zone (9) of the workpiece (1) is immersed. The lower electrode guide (1) is supported on the stand (4) of the machine by means of a guidearm (13). The guide-arm (13) crosses the back wall (19) of a container (18) at a right angle in an opening (21a) covered by a sliding closing piece (22) that is parallel to the back wall (19) of the container (18). The guide-arm (13) crosses the closing piece (22) of the container (18) at a right angle in another opening (24) where it is slidable. The closing piece (22) is arranged at the outside of the container (18) on a side (26) of the back wall ( 19) facing the stand (4).