Geometry, specification, and drilling performance of a plane rake faced drill point design

Abstract

A study of a modified drill point design with plane rake faces is presented. The critical geometries that uniquely define the drill point design are analysed based on the international standard. The study shows that the modified drill design yields positive normal rake angle on the entire lips and point relieving in the chisel edge region. An experimental study of drilling a high tensile steel using 7–13 mm high-speed steel (HSS) drills with titanium nitride (TiN) coatings has been carried out to assess the new drill point design. It shows that the modified plane rake faced (PRF) drills can reduce the thrust force by as much as 46.9 per cent with an average of 23.8 per cent, as compared to the conventional twist drills under the corresponding cutting conditions, while the reduction in torque is also significant with the maximum of 24.9 per cent. These drilling performance improvements are comparable to those from using the multi-facet drills that were claimed as one of the most heartening drill developments in several decades for drilling force reduction, while the PRF drills can be easily sharpened using the conventional twist drill grinders. The drill-life tests amply demonstrate the superiority of the PRF drills over the conventional twist drills.