| 摘要 |
A male screw which has a protrusion protruding from a thread thereof at least with regard to the normal direction to a flank of the thread. To obtain such male screw, a blank is introduced between rolling dies which are moved relative to one another and is rolled between the rolling dies to be formed with a thread. In this thread rolling process, the rolling pressure on an area of a die face of at least one of the rolling dies is determined to be higher than that in ordinary thread rolling process and the rear end portion of the area of the die face is made to bite into the blank, causing the corresponding portion of the blank to be forced out to form the protrusion.
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