Abstract: An apparatus for preparing a surface of a cylinder bore by electrical discharge machining includes a rotatable spindle and at least one electrode operatively connected to a power source and rotatably supported upon the spindle, the electrode being movable radially relative to the surface of the cylinder bore between a first retracted position such that the electrode is positioned within the cylinder bore prior to preparing the surface and at a second position spaced from the first position wherein the electrode is adjacent the surface of the cylinder bore for preparing the surface by electrical discharge machining as the electrode rotates with the spindle.

Abstract: A fast hole drilling EDM electrode and a more efficient apparatus and method for electrical discharge machining using the electrode. The electrode has an electrically conductive body with a leading end or tip and a length of relatively uniform non-circular cross-section that is operatively adapted to provide a dielectric flush path between the electrode body and the hole being machined in the workpiece. At least one dielectric supply bore is formed lengthwise through the body. The one or more supply bores connect a dielectric exit at the leading end of the body with a dielectric entrance located distally therefrom. This electrode is operatively adapted for being rotated during the machining process and for its non-circular cross-section to form a hole with a circular cross-section, when so rotated.