Resistance welding has already proved its inherent advantages as an assembly process. However@ the potential is still great for improving its quality and production capability@ as well as lowering its cost factors. In many cases the potential for improving resistance welding techniques is greater than the potential for improving other manufacturing processes. The potential for improvement is understandable in view of the number of variables involved and the exceedingly large combination of those variables that will produce satisfactory results. Although the fatigue life of spot welds subjected to cyclic loads compares favorably with rivets@ improvement is desirable to keep pace with the advancing requirements of jet aircraft@ high-thrust jet engines@ guided missiles@ unitized body-frames for automobiles@ etc. The endurance limit of spot welds under repeated loading is approximately 12 % of their tension-shear rupture loading regardless of the material used.