Abstract: The method of abrasion forming friable material such as carbon blocks to form electrical discharge machining electrodes therefrom comprising the steps of moving a master model, having an abrasive surface which is a mirror image of a desired form to be abrasion machined in the friable material, which surface is related in size to the desired form to be machined by an additional movement to be imparted to the master model, toward the friable material with the abrasive surface of the master model and workpiece in engagement while imparting the additional relative motion between the master model and workpiece, which additional relative motion is in all directions in a plane perpendicular to the direction of movement of the master model and workpiece and flushing between the master model and workpiece to prevent build up of abraded particles of the workpiece on the master model.

Abstract: A cutting master for total form abrasion machining a predetermined shape in a friable material including a body having a surface which is substantially the mirror image of a shape to be machined by abrasion, which surface is abrasive, is different in size from the shape to be abrasion machined by a predetermined amount, and includes a flat portion having a dimension related to the difference in size between the predetermined shape and the abrasive surface.

Abstract: Servo head structure for electrical discharge machining or the like comprising a rectangular frame having a rectangular ram positioned therein, bearing means for guiding the rectangular ram for movement in the frame, a shaft rotatably mounted in the frame and extending through the ram, a rotary hydraulic servo motor secured to the frame and connected to the shaft for rotation of the shaft, and cable means secured at opposite ends thereof to opposite ends of the ram and wrapped around the shaft centrally thereof, whereby on rotation of the servo motor controlled movement of the ram with respect to the frame is accomplished.