| 摘要 |
This invention provides a steel fastener having an elongate shank, an enlarged head formed at one end of the shank, and a generally pointed tip formed at the other end of the shank. A grooved portion of the shank is formed with helical grooves defining helical ribs and with annular grooves defining annular rings. The shank may have a cylindrical portion between the grooved portion and the tip and a cylindrical portion between the grooved portion and the head. Each of the annular grooves has a root where deepest and each of the annular rings has a crest where largest. According to this invention, the roots of the annular grooves define an imaginary cone diverging toward the tip, and the crests of the annular rings define an imaginary one converging toward the tip. Consequently, the fastener can be easily made without encountering the problem discussed above. Additionally, the fastener functions effectively for fastening a workpiece having a given thickness to a metal substrate having a thinner wall.
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