Effect of drill gash rake angle on drillability in plain carbon and low alloy steels

In this study, the effects of the gash rake angle (γ a ), which is an important component of the drill geometry, on the thrust force and drilling torque occurring in the drilling of ordinary carbon steels (AISI 4140 and Ck 45) were examined through experimental and FEM-supported numerical simulation studies on surface roughness, tool surface roughness, wear and diameter deviation values were investigated experimentally. In the experiments, 6.8 mm diameter solid cementite carbide, coated and internal cooling channel drills with +10°, 0°, −10° gash rake angle were used. Three different feed rates and cutting speed levels were selected as cutting parameters. Determination of material-specific gash rake angle and cutting parameters for different materials was carried out by Taguchi-assisted variance analysis of experimental data. In experimental studies, the gash rake angle was 65.9% effective on the thrust force for AISI 4140 tempered steel, while it was the second effective parameter with 29.22% for Ck 45 manufacturing steel. While the feed rate is the more effective parameter in the drilling moments that occur when drilling different materials, it has been observed that γ a also has a significant effect. It has been determined that chisel edge wear, main cutting edge wear and crater wear occur in the drill when drilling AISI 4140 tempered steel and Ck 45 manufacturing steel. The data obtained from the finite element-assisted chip removal analyses support the experimental results and provide guiding results in the selection of material-specific gash rake angle.