| 摘要 |
1376586 Self-tapping screws; rolling USM CORP 23 May 1973 [24 May 1972] 14732/74 Divided out of 1376585 Headings B3N and B3M A self-tapping threaded fastener comprises a cylindrical shank portion 12, a tapering workentering portion 16, a continuous thread formed on the work-entering portion and part of the shank portion, and a plurality of rows of thread forming lobes 30 superimposed on said thread over only the work-entering portion, one of said rows includes a lobe or lobes 30<SP>1</SP> which close to the junction of the shank portion and the workentering portion extend radially further from the longitudinal axis of the fastener than the distance from the axis to the crest of the thread on the shank portion. The fastener is formed by rolling between a primary and secondary die. Only the primary has lobe forming recesses whilst both dies have a rerolling section whereby after the lobes are formed the lobes on all but one row are rerolled to give the required construction. |
