Insulating materials are now subjected to precision electrical discharge machining (EDM) using an assisting electrode method (AEM). The electrode materials usually comprise copper, graphite and copper alloys that have high melting temperature and excellent electrical and thermal conductivity. A brass electrode is known as a humble electrode. Performances of brass and copper pipe electrodes were compared on silicon nitride machining. Results showed that a brass electrode had more advantages than a copper electrode. Material removal rate (MRR), electrode wear ratio (EWR) and surface roughness were compared, while the conductive layers were examined by a scanning electron microscope (SEM) energy dispersive spectrometer (EDS).