*****The dies of these spring swages are drop forged S7 tool steel. The clapper dies are heat treated after forging and then welded to a mild steel spring. The weld wire is a high tensil strength wire designed for use with dissimilar materials. However the weld is also the stress point. Due to the likelihood that each blow will not be even, the weld will eventual fracture. It is for this reason that we can only replace these if the dies themselves fail and for reasonable amount of time and use. DO NOT USE Hands to hold under a power hammer.