A device adapted for use with electrical discharge machining apparatus generates tapped holes in a workpiece using a threaded, hollow carbon tool. The tool is releasably connected to a reversible hydraulic motor by a coupling which feeds dielectric fluid through the interior of the tool into the space between the machining tip of the tool and the workpiece. The motor is mounted on a vertically reciprocable slide arrangement carried by a support which is mounted on the head of the conventional electrical discharge machine. The tool extends downwardly through a threaded guide which is held in spaced relationship to the workpiece by the support, thereby allowing fluid emanating from the tip of the tool to carry machined fragments upwardly out of the tapped hole. The slide includes a slide plate mounted on a pair of upright guide posts carried by the support. The weight of the slide plate and the motor apply constant downward pressure on the tool, thereby precisely controlling the spacing between the tool tip and the workpiece, even during motor reversal. A plurality of aligning elements removably mounted on the support allow rapid set-up and alignment of the tool relative to the workpiece.
展开▼
