
375Machining by Electrochemical Erosion
drilling (STEM). As shown in Figure 11.18, the cathodic tool is made from
a glass nozzle of 0.025–0.50 mm diameter. To conduct the machining cur-
rent through the acid electrolyte that lls the interelectrode gap, a plati-
num wire electrode is tted inside the glass nozzle. Solutions of sulfuric,
nitric, or hydrochloric acid with a concentration of 12–20 weight percent
are common electrolytes. Electrolyte temperature is normally 40°C for sul-
furic acid and 20°C for the rest. Electrolyte pressure that ranges between
275 and 400 kPa is recommended (Rumyantsev and Davydov, 1984). A gap
voltage of 70–150 V is ...