Abstract: A rotary cutting tool blank comprises a cutting portion having a longitudinal axis and a plurality of teeth extending the length of said cutting portion, with each of the teeth having a cutting face and a trailing face and a land surface bridging the cutting and trailing faces. The land surfaces are interrupted by a plurality of spaced transverse depressions of relatively large radius arcuate cross section to form a plurality of cutting edge portions at the junction of the cutting face and the uninterrupted portions of the land surface. The cutting edge portions have a positive rake angle, and the trailing and cutting faces of each tooth have surfaces which undulate generally sinusoidally from one end of the cutting portion to the other so that the rake angle of each cutting edge portion varies continuously along its length. The cutting tool blank can be transformed to a cutting tool ready for use simply by suitably relieving the land surfaces to form cutting edges at the aforementioned cutting edge portions.