Abstract: A cutting tool assembly comprises a cutting tool having a plurality of cutting edges which is held in a desired cutting position by a tool holder. The tool holder comprises an elongate body having a bifurcated end defining a pair of spaced tool gripping members and a tool receiving opening between which the cutting tool is releasable clamped in a vise like action. Each of the tool gripping members include a pair of opposed contoured faces each having a retaining wall for complementally abutting certain cutting edges of the tool in order to prevent rotation of the cutting tool relative to the holder. One edge of the cutting tool extends outwardly beyond the holder adjacent one corner of the tool receiving slot so as to be disposed in cutting relationship to the workpiece which is to be cut.