A modeling method is presented for the evaluation of the eroded crater during electrical discharge machining. The method is based on the propagation of the melting crater when other effects such as evaporation can take place. Calculations are performed for a point heat source on the surface of copper and steel electrodes. An experimental technique for the measurement of the amount of eroded material is described: the method consists of extraction of the metal from the dielectric fluid by chemical reactions and measurement of the resulting color intensity.