effect of the rigid and elastic thread portions a separately prepared round rod is clampingly set between movement start ends of pair rolling flat dies each of which has distinct front and rear portions in the direction of its progress the front portion being formed on the inner side with a set of small parallel threads for preliminary processing inclined in coincidence with the helical lead angle of the screw and formed at a uniform pitch the rear portion being formed on the inner side with a set of large parallel threads for finish processing formed as extensions of every other ones of and at twice the pitch of the small threads for preliminarily processing and the two rolling flat dies are moved in opposite directions in a clamping relation to the round rod thus effecting a first step of preliminarily forming the outer periphery of a rotating round rod with two continuous small threads having a predetermined pitch and a second step performed subsequent to the first step for regularly forming a large thread in super imposition on every other one of and at double the pitch of the two small threads thereby forming a buffer groove in the top of the large thread with plastic deformation of the two small threads in this way the screw with groove for self locking according to the invention is manufactured now specific examples of the mode of practice in connection with the screw with groove for self locking according to the invention will be described in detail with reference to.