Fabrication of Deep, Narrow Holes in Steel Using High-speed Electrical Discharge Machine with Conductive Aqueous Working Fluid

Conductive aqueous working fluid is increasingly being used instead of dielectric oils or deionized water for hole-fabrication in steel by means of electrical discharge machining (EDM). In the present study, the drilling speed, rate of wear on a tool electrode, and the precision of a hole-fabrication EDM system using aqueous working fluid (conductivity <1000 μS/cm) were examined. The working fluid was deionized water containing an additive which was composed of a surfactant (dispersant for other contents), a cleaner, an extreme pressure agent, an antirust agent, an antiseptic, and an antifoaming agent. For holes of diameter 0.40–1.20 mm and depth of 20 mm fabricated in S50C steel, the drilling speed and the wear on the tool electrode were improved by increasing the amount of additive. However, the precision of the fabricated hole decreased when the additive was used.