Effect of tool nose profile tolerance on surface roughness in finish turning

Although the influence of nose geometry of a cutting tool insert on the surface roughness of the finished workpiece has been studied in detail, the effect of the tool nose profile tolerance in new cutting inserts on the surface roughness has not been investigated in the past. In this paper, we study the effect of tool nose profile tolerance in new inserts on the surface roughness using simulation and experimental methods. In the simulation study, a high-resolution optical metrology system was used to capture an image of the tool nose. A sub-pixel edge detection approach combining moment invariance operator with modified Sobel 2-D filter operator was used to extract the nose edge profile. The workpiece profile was then generated digitally using the extracted nose profile, and the effect of the nose profile deviation on the surface roughness was assessed. The maximum differences in the surface roughness parameters R-t, R-a, and R-q between the surfaces generated by the actual tool nose and the ideal (circular) tool nose images were found to be 40.3, 26.1, and 24.5 %, respectively. The simulation study showed that the nose profile deviation alone can cause the surface roughness to vary as much as 40.3 % (Rt) although the same type of inserts are used. The simulation results for Rt and Rq were found to agree well with the experimental data with less than 10 % difference for 79 % of the tool edges. Our study shows that although the nose radius tolerance is within the 10 % allowed in the ISO3685 standard, the nose profile deviation has a significant influence on the surface roughness.