A method of making a tillage blade by obtaining a generally circular sheet metal steel disc having an outer peripheral edge. Waves are made in the outer peripheral edge of a circular steel disc in a predetermined pattern while the steel is cold. The outer peripheral edge is then sharpened at a predetermined acute angle with respect to a first plane by grinding. Then the disc is heat treated to make it harder so it will wear longer. If it is desired to have a concave/convex disc, instead of a coulter, then during the heat treating process the disc is deformed so that the sharpened portions of the peripheral edge remain generally in the first plane but a central portion of the disc is disposed at least partially in a second plane which is parallel to but spaced from the first plane.