Improved chip discharge in drilling of glass plate using back tapered electroplated diamond tool

Previous studies of a through-hole drilling for hard and brittle materials using electroplated diamond tool devised by the authors have led to several challenges such as a restraint of crack size at the inlet and outside, a suppression of chip adhesion on the tool and an improvement of processing efficiency. In this paper, the devised tool was redesigned in order to restrain cracks of the inlet side as well as to improve the chip discharge. The new design of the tool featured a back taper which was expected to bring an effect of restraining crack size by preventing any interference between the tool cylindrical surface and the hole inner surface during drilling process. In addition, the chip can be discharged from the drilled hole through the back taper. Results of the experiment indicated that by providing the back tapered shape, the width of the inlet hole can be reduced slightly as the interference between the glass plate and the tool cylindrical surface was suppressed. Furthermore, the adhesion of chip on tool can be restrained by using the tool with large chip discharge space as the chip was easily discharged to the outside of the hole. Moreover, an abrupt change in thrust force was not detected, and the crack width was found in small size.