Edge Radius Variability and Force Measurement Considerations

A new, noncontact instrument, based on white light interferometry, is used to measure the edge radii of cutting tools with measurement errors of less than 3 μm. Edges of several commercial cutting inserts are measured and compared. It is found that the radius of the hone varies along the length of the edge in a parabolic manner. The difference between the edge radius at the center of the edge and the radius at the start of the corner can be as large as 25 μm (0.001 in). The variation between the edges on an insert and across inserts in a batch of tools can be as high as 25 μm (0.001 in). Statistically significant variations are also seen in the corner radius region in which much cutting occurs in turning, boring and face milling processes. Orthogonal cutting tests with tools of measured edge radius in the zone of cut indicate that the machining forces, especially the thrust force component, are sensitive to changes in edge radius on the order of measured variations. [S1087-1357(00)01603-8]