A CNC tool grinding machine has at least one rotatable grinding wheel (1) movable relative to a workpiece (2) for grinding a flute surface (3) of a blade in the workpiece (2). The machine is programmed with a path for the grinding wheel (1) calculated to grind a smooth cutting edge (5) for the blade, and programmed with perturbations to the path which vary the movement of the grinding wheel (1) to grind a wavy cutting edge (6) in the workpiece. With such a machine, it is possible to grind all surfaces of a wavy cutting edge in a single set up rather than requiring two or more grinding and milling operations to form the wavy cutting edge.