Stainless steel, magnesium, brass and titanium sheets, having thickness equal to 1 mm, were used as workpiece materials and hydrocarbon oil (Hedma 111) was used as dielectric fluid. These workpiece materials were chosen in order to have a wide range of both physical and mechanical properties; density, electrical resistivity, Brinnel hardness (HB), melting point and specific heat values of the selected materials are reported in