The present invention provides an improved method of manufacturing a rupture disk and specifically of forming a score on a rupture disk. The method of the present invention includes the rotating of a rupture disk blank relative to an electrical discharge machining or “EDM” cutting wire and the simultaneous moving of the EDM cutting wire toward the axis of the disk while maintaining the wire in a selected position such as generally parallel to the disk peripheral skirt or flange. The rotation of the disk and the movement of the EDM wire can be precisely controlled with the motion system of a commercially available EDM machine. With the present invention, a precise score is cut a partial distance through the disk thickness and preferably on the convex side of the dome, near the transition from the dome to the flange and in a generally “c” shaped pattern. The formed score creates a pattern of weakness so that the disk will open in either of the forward or reverse buckling direction. Score patterns other than the “c” shaped pattern could be cut.