SCREW FASTENER WITH DOUBLY REINFORCED LEAD AND IMPROVED BASE PENETRATION PART OR LEAD END PART

摘要

PROBLEM TO BE SOLVED: To provide a screw fastener with a novel improved doubly reinforced lead capable of reducing inserting torque. SOLUTION: This screw fastener is provided with first main threads, and a pair of second auxiliary threads alternately formed between the thread ridges in the first main threads. A part of a doubly reinforced lead conventionally formed between a tip part and the main threads or between the first thread ridges of the first main threads and the second thread ridges is eliminated. COPYRIGHT: (C)2004,JPO&NCIPI