US Patent 7959234 Rotatable cutting tool with superhard cutting member

A rotatable cutting tool that is useful for impingement upon a substrate and is adapted to be rotatably retained within the bore of a holder. The rotatable cutting tool includes an elongate cutting tool body, which has an axial forward end and an axial rearward end, as well as a socket at the axial forward end thereof. The rotatable cutting tool also includes a hard cutting member that is affixed to the cutting tool body within the socket. The hard cutting member has an axial forward end and an axial rearward end. The hard cutting member has a superhard axial forward portion at the axial forward end thereof wherein the superhard axial forward portion has a maximum transverse dimension. The hard cutting member further has a hard axial rearward portion contiguous with and axial rearward of the superhard axial forward portion. The hard axial rearward portion has a maximum transverse dimension. The ratio of the maximum transverse dimension of the superhard axial forward portion to the maximum transverse dimension of the hard axial rearward portion ranges between about 0.35 and about 0.45.