| 摘要 |
A bolt is provided to prevent burr from forming on a clamping face of the bolt head by the position of a final cut portion from a bottom end of the bolt head to a central part of the bolt head during forming of a bolt head, and prevent burr from forming on the clamping face by forming the bolt using a forging process without an additional process, and a method for manufacturing the bolt is provided. A method for manufacturing a bolt comprises: a step of cutting a long wire(10) to a predetermined length; a step of forming a preformed part(12) with a diameter larger than that of the wire on one portion of the cut wire by a forging process; a first trimming step of partially trimming the preformed part from one end of the preformed part to the other end thereof to form a bolt head(13') on one portion of the preformed part; a second trimming step of trimming the preformed part from the other end of the preformed part to the bolt head(13') to form a bolt head(13") on the other portion of the preformed part; and a step of forming a spiral part(14) on the other portion of the wire. The second trimming step comprises overlapping an end of the bolt head(13') formed in the first trimming step such that a portion of the preformed part except a bolt head(13) capable of cutting. The step of forming the preformed part comprises a first forging process of partially expanding one portion of the wire such that the portion of the wire is expanded to a diameter slightly larger than that of the wire to form an expanded part(11), and a second forging process of forming the expanded part into a circular preformed part. |
