Surface texture produced by peripheral milling with helical end mills

Abstract

An investigation of the surface texture produced by peripheral milling with end mills has been made. Theoretical relationships are presented to predict the theoretical cusp height and approximate the arithmetical average surface roughness based on the geometrical considerations of a circular tooth path. Experimentation was conducted to correlate the theoretical approximations and to determine the significance of process variables using multiple regression analysis. The theory, based entirely on the geometrical aspects of a circular tooth path, indicated that the theoretical cusp height may be determined knowing the cutter diameter and the incremental feed per tooth. The location of the mean line, about which the surface roughness was evaluated, is determined. Approximations of the arithmetical average surface roughness are presented which indicate that the roughness may be approximated knowing only the cutter diameter and the incremental feed per tooth. A compensation for tooth height variation is also considered. Multiple regression analyses of data obtained experimentally for this project and data obtained from a similar study involving end mill deflection indicate that feed per tooth and cutter helix angle are the primary process parameters contributing to surface finish. A relationship between cutter helix angle, radial rake angle and oblique radial rake angle indicates that the oblique radial rake angle and not the helix angle may be the most significant variable not included in the geometry based theory.