the intergranular space. This results in an increase in the height at which the diamond grains project out from the binder, and for certain values of this height the process of continuous self-sharpening of the diamond grains begins. This method is easily realized on standard equipment. The electroerosive (electric discharge) method for controlling the condition of the cutting surface of diamond wheels is based on breakdown of current-conducting material when current pulses are passed between the electrodes. Pulsed discharges, initiated from pulsed or d.c. current generators, as a result of erosion remove mierovolumes of binder from the wheel surface, promoting exposure of the grains and an increase in their projection height. A disadvantage of the electroerosive process on the working surface of the diamond wheel is the possibility that the grain.~ might fall within the discharge zone, which leads to formation of cracks, microcleavages, and a new submicrorelief for the diamond grains. An advantage of this method is the possibility of realizing it without using the aggressive media usually filling the interelectrode gap. As was established by previous investigations, in grinding siliconized graphite, the structure and properties of the material promote microfracture of the diamond grains, creating conditions for renewal of the microrelief. Therefore the major problem in controlling the condition Of the cutting surface is removal of grinding products from the intergranular spaces and control of the rate at which the grains are exposed. The use of an electroerosive process would lead to increased consumption of diamonds as a result of additional fracture of the grains. Furthermore, the method is inferior to the electrochemical method with respect to the degree of development of the cutting relief formed. With the goal of achieving the best conditions for action on the working surface of a diamond wheel, we chose a setup for controlling the condition of the cutting relief in which independent action on the binder of the wheel was incorporated with the help of a cathode device connected to the negative pole of a d.c. current source. Such a setup allows us to change the intensity of electrochemical action by changing the gap between the cathode and the wheel or by changing the applied voltage, and is distinguished by stable maintenance of the specified electrochemical action. The design of the cathode device was chosen according to the grinding setup. In the case of machining with the face of the wheel, wear of the cutting surface has practically no effect on the characteristics of the interelectrode gap when using cathode devices of familiar designs. At the same time, the process of circular external grinding is accompanied by a decrease in the wheel diameter due to its wear, and the use of cathode devices of conventional design leads to a variable gap over the length of contact with the wheel. So the actual active area of the cathode is reduced, which diminishes the technological capabilities for controlling the rate of the electrochemical action on the cutting surface of the wheel. In order to eliminate the indicated disadvantage, we developed a special design for the cathode device (Fig. 1). The gap between surfaces of the device and the wheel is held constant owing to the fact that the cathode chock is split and consists of individual segments 2, clamped down on the flat spring 3. The ends of the spring through the rod 4 are connected with screw 5, the movement of which changes the radius of curvature in accordance with the radius of curvature of the wheel surface 1. The cathode device holder 6 can be moved in the radial direction to control the gap. The design allows us to broaden the technological capabilities for controlling the condition of the cutting relief as a result of most efficiently using the working surface of the cathode.