A diamond cutting tool is disclosed that forms at least a pair of grooves in the shank of the tool. The grooves contain sintered diamond prior to formation of concave flutes next to the grooves. The grooves are angled to form positive or negative cutter rake angles, whichever is desired. The adjacent concave flutes subsequently formed in the shank of the tool begin parallel with the cutting face of the sintered diamond and curve away from the base of the diamond back towards the surface of the shank. Sharpening of the diamond then results in very little removal of the diamond material thus assuring the integrity of the tool.