Abstract: An apparatus and method which utilize electrical discharge machining equipment and techniques to prepare an electrically conductive surface for thermal spray coating or for other purposes. The apparatus includes one or more electrodes, with each electrode having a working face, defining a plane. The one or more electrodes are mounted on the leading end of a shaft and can form part of an electrode assembly. The shaft is at least moveable axially by a shaft actuating mechanism and, in some applications, may also rotate the shaft. Each electrode is moveable by a gap setting mechanism in response to and in a direction different than the axial movement of the shaft to form a voltage gap between each working face and the surface being prepared. A supply of dielectric fluid is disposable in the voltage gap. An electrical discharge circuit conducts an electric current through the dielectric fluid in the gap to produce a gap voltage. The shaft actuating mechanism is controlled by a gap voltage control system.