MULTI-THREAD ROLLING DIE MANUFACTURING METHOD, MULTI-THREAD ROLLING DIE, AND MULTI-THREAD BOLT MANUFACTURING METHOD USING THE SAME

摘要

Provided are a multi-thread rolling die manufacturing method for improving the durability of a fine thread working portion, a multi-thread rolling die, and a multi-thread bolt manufacturing method. The multi-thread rolling die comprises a parallel thread ridge (5) having an extended parallel thread, and a projection (6) corresponding to the fine thread ridge formed periodically in the bottom (5a) of the parallel thread ridge (5) in accordance with the phase shift between the fine thread ridge and the parallel thread ridge extended from the fine thread. The bottom portion (6c) of the portion having the projection (6) corresponding to the fine thread is so raised as to become flat at a position shallower than the bottom (5b) of the reference parallel thread.