Comparison of cutting edge characterization techniques applied to industrial tools with sub micrometer edge radius

Within micro and precision machining, cutting tool performance with respect to the ability to generate fine surfaces is largely determined by the size of the edge radius, which dramatically affects the minimum uncut chip thickness. In the recent years emphasis has been placed on cutting edge radius characterization. While the measurement techniques from literature can be well suited for ordinary tools with edge radii in the order of tens of microns, tools for fine finishing operations, exhibit edge radii in the sub-micrometer range, which limit the robust applicability of such techniques. This paper presents an investigation on the characterization of ball nose end mill cutting edges with sub micrometer edge radius. For this purpose CBN and WC tools cutting edges were characterized by means of a confocal microscope (Olympus Lext OLS4100). The measurements were validated through reference AFM measurements and the data fitted with known cutting edge determination algorithms. The influence of the roughness of rake and clearance face on the robustness of the edge radius calculation is discussed and the capabilities and limitations of the methods are highlighted.