PURPOSE: To acquire a double cam provided with high impact strength at a low cost without drifting of both cams by applying such work processes to a workpiece as machining its outer diameter and thickness dimensions and its grindstone clearance groove, shaping it into upper and lower surface cams, together with thereto, so as to determine predetermined hardness given thereto and applying plane polishing, thick dimensions, and remove distortion.

CONSTITUTION: A workpiece 8 is cut off from a metal round bar having its outer diameter dimension not less than maximum outer diameter dimensions of upper and lower surface cams 1 and 2 of a double cam, set to be slightly thicker than the cam, processed to have predetermined outer diameter and thick dimension which is needed to the double cam processing by an NC lathe, subjected to a processing of a round grindstone clearance groove 3, and provided with a cam center reference hole 7, a cam attaching hole 5 and a reference hole 6 drilled therein. The double cam is processed in a machining center so as to provide the contours of the upper and lower surface cams 1 and 2 with polishing margins to be worked, subjected to vacuum harden ing to have predetermined hardness, and to a flat plane polishing additionally serving as determined thickness. dimension and removing distortion, subjected to a finishing process at the cam center reference hole 7, and the upper and lower surface cams 1 and 2 are simultaneously finished.