The present invention relates to a method for trueing grinding disks having an outer layer with diamonds or cubic crystalline boron nitride using a driven trueing roll and an additional trueing aid.
Profiled diamond grinding disks are, during production thereof pre-profiled by a pressing step and subsequently ground with ceramic disks such as silicon carbide grinding disks. This is, however, an expensive method, and subsequent profiling must be carried out by the producer of the disk. Therefore, it is already known to provide for the use of profiled grinding disks with diamond or cubic crystalline boron nitride in galvanic binding only one layer of grain, whereby however such disks after loss of their exact form cannot be used any longer.
The use of trueing respectively profiling rolls of steel or hard metal is known for the trueing and profiling of corundum or silicon carbide grinding disks with ceramic binding. Such a profil roll presses during each revolution of the grinding disk onto the grinding grains which project farthest from the binding. These grinding grains partly break under the applied pressure out of the brittle binding material of the grinding disk and are pressed partly into the grinding surface of the disk. Also known are profile rolls of silicon carbide in ceramic or bakelitic binding for the trueing of grinding disks (U.S. Pat. No. 2,456,762) which are, however, usable only for grinding disks with diamonds in ceramic or bakelitic binding material. Diamond tools, such as diamond trueing rolls, are usually used for trueing of grinding disks with corundum or silicon carbide, which tools, in view of their greater hardness, permit to provide such grinding disk with the necessary profile.
Further known is the trueing of a diamond grinding disk using a so-called crushing roll, which has no diamond layer and which is at slow circumferential speed pressed against the grinding disk to be trued, which is rotated with the same circumferential speed. With such a crushing roll it is possible to true grinding disks with diamond or with cubic crystalline boron nitride, but an additional trueing aid is thereby advisable which consists of corundum in ceramic binding and therefore is relatively soft and accordingly adapts itself easily to the profile. In a known method (German Auslegeschrift No. 25 34 872) such a stationary trueing aid is pressed with constant pressure against the grinding disk. Thereby an addition to the grinding surface due to compression during the rolling in of the profile shall be avoided, in that the grain of the grinding disk which at first has been pressed by the stationary trueing stone into the peripheral surface of the grinding disk, are again removed from the binding thereof, to thereby provide an improved peripheral surface, or a greater grinding output. The trueing stone is therefore given the task to clean the peripheral surface of the grinding disk from crushed binding and broken out grain particles.
Grinding disks with an outer layer or cubic crystalline boron nitride or diamond particles, which are trued by diamond trueing rolls, show after trueing not a sufficient grinding capacity. This results especially from the fact that, during the cutting of the cubic crystalline grains with diamond, surfaces are produced on these cubic crystalline grains which impair the grinding capacity. To assure that the grains project slightly beyond the binding material, which is necessary for the removal of the shavings during the grinding, there has been up to now, after trueing of the diamond grinding disk with a diamond trueing roll, a reworking carried out, for instance by use of the above-described stationary trueing stone, with which the binding material has been set back so that the individual grains of the grinding disk project partly beyond the binding to thereby create a shaving space between the individual grains. This method has, however, shown itself to be imperfect in practice. If for instance the grinding disk has to be provided with a thread profile, the teeth of which end with a sharp edge, then, by subsequent use of the stationary trueing aid a rounding of the tooth edges is produced, which is highly undesirable. This is due to the fact that, by the subsequent use of a stationary trueing aid, it is impossible, due to the high relative speed between the trueing aid and the grinding disk, to receive a sufficient projection of the cubic crystalline boron nitride grains beyond the peripheral surface of the binding material, for instance if the peripheral speed of the grinding disk is 30 meters per second.