The self-locking screw bolt has a common thread part and a self-locking thread part with slit on the top of thread. During prodn, after the multiple thread part is chased, at least two screw teeth are connected with thread die of the same pitch to chase the self-locking thread part while the common thread part is chased. On the thread die, there are multiple thread die part to form the multiple thread, and the last thread die part to form the self-locking thread part and the common thread part simultaneously. |