An ECM method involves the use of a thin hollow electrode assembly that carries the electrolyte within and that is advanced relatively to the workpiece. The small profile of the electrode results in a minimal removal of metal in forming the desired rotor or stator shape. The electrode profile allows significant power consumption reduction or increased machining speed for a given rate of power input. The electrode can be a unitary ring shape or can be made of segments that are placed adjacent each other so that a continuous shape is cut. Not all the lobes of the stator or rotor have to be cut in the same pass. Electrode segments can be used to sequentially provide the desired lobe count in separate passes. The lobe shapes in the electrode can be slanted to get the desired rotor or stator pitch or they can be aligned with the workpiece axis.