Indexable cutting insert for rotary cutting tools

A rotary cutting tool comprising a cutting portion having a longitudinal axis and a plurality of helically arranged teeth separated by helical gullets extending the length of said cutting portion, the leading edge of each tooth comprising a plurality of sockets and cutting inserts disposed in said sockets, each cutting insert comprising a six sided block having a longitudinal axis and two major parallel rhomboid-shaped plane surfaces constituting a seating face and a clearance face respectively, two opposed minor side surfaces constituting cutting faces extending parallel to said longitudinal axis and extending between said seating and clearance faces, each said cutting face forming an acute angle with said clearance face and forming a cutting edge along the intersection therewith, and two minor parallel plane and faces extending between seating and clearance faces and said two cutting faces, each said cutting face having a concave curvature centrally of its major dimension, and convex curvature at each end of its major dimension to define a serpenting cutting face and cutting edge;

• said sockets being of complementary shape to said cutting inserts and so disposed along each tooth that said cutting inserts are arranged along the leading edge of each tooth substantially the length thereof, with cutting edges in operable relationship thereto and in substantially parallel relationship with the leading edge of said tooth.