| 摘要 |
A screw fastener formed with improved thread construction adapted to provide a staged or graduated entry into a workpiece. The fastener comprises a shank section formed with an integral driving head at one end and a tapered or conical point section at the other end, and a raised helical thread extending from near the tip of the conical point substantially throughout the length of the point and shank sections. The diameter of the thread increases gradually from the point tip along the length of the conical surface and then decreases in diameter - or increases at a lesser degree - as it approaches the cylindrical shank section.
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