Ductile Regime Grinding of Hard and Brittle Materials Based on Optimum Design of Cutting Edge Truncation

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As a means to realize ductile regime grinding of an optical glass, a truncation method in which diamond cutting edges are truncated to be aligned on the grinding wheel surface is focused on in order to optimize the truncation conditions. The results are summarized as follows.1. Three-dimensional shape of diamond grain cutting edges was measured using a scanning laser microscope and it is found that the shape of cutting edge can be represented by triangular cone and the negative rake angle is 70 degrees in average.2. Boron-silicate glass was ground by a single point diamond abrasive grain on an ultra-precision face lathe. The cutting edge characteristics of SD46 grains were measured in advance using the above method. It is found that the critical depth of cut dc at which the material removal process transits from ductile regime to brittle regime is about 100 nanometers at the negative rake angle of 70 degrees.3. Computer-aided simulation of surface plunge grinding was carried out and it is found that a finished surface roughness of nanometer order is easy to be generated by the truncation of coarse-grained grinding wheel, but a fine-grained grinding wheel is prerequisite in order to realize ductile regime grinding in which the maximum grain depth of cut must be kept less than the critical depth dc.4. A truing technique in which the grinding wheel axial profile is given by a straight line enveloped by circular arcs is proposed in order to realize the wheel axial profile of sub-micron flatness. The effectiveness of this technique was confirmed experimentally by electro-contact discharge truing of a metal-bonded diamond wheel.