Effect of Cutting-Edge Shape on Ductile Regime Grinding of Optical Glass in Single-Grit Diamond Grinding

A series of single-grit grinding is carried out using single-crystal diamond grit as the cutting tool and borosilicate glass as the workpiece. The three-dimensional shape of cutting edges is measured using a scanning laser microscope (SLM), and the three characteristic angles, rake angle, edge angle and wedge angle, are introduced for one-faced and two-faced cutting edges. The critical depth of cut dc, at which the machining process changes from the ductile regime to the ductile-to-brittle intermediate regime and below which lateral cracks disappear, is observed using an atomic force microscope (AFM) and the depth is measured using the SLM. It is found from the experiments that the critical depth of cut varies from 60 to 160 nm depending on the rake angle and roundness of the cutting edge. As to the effect of grinding direction, the value of dc in the case of up-cut grinding is 20 nm larger than that in the case of down-cut grinding.