Machining movement based analytical modelling of twist drill and its application

This paper presents a novel direct approach of analytical modelling of twist drill based on grinding movement. The geometric model is the recording of machining locus on the drill blank. Adapting to peculiarity of the twist drill configuration, it is further projected on consecutive cross-sections of the flute and flank. Thus, the drill model is manifested analytically by a series of planar curves without resorting to numeric approximation. Precise solutions for a number of key elements for drill structure are deduced, such as flank/flute intersection, chisel edge determination, and various cutting angles’ calculation. The modelling procedure is illustrated by practical examples. Its effectiveness is demonstrated by the agreement between the modelled and measured values of the cutting edge and chisel edge.This modelling method can be applied as a platform to improve the drill point performance. The machining is composed of helical movement of the fluted drill blank and transversal movement of the grinding wheel. The flank configuration can be modified by varying some grinding variables concerned with helical movement of the blank, transversal movement of the grinding wheel, and cross-sectional profile of the grinding wheel. Its validity is verified by practical examples with favourable results of thrust experiments and wearing tests.