| 摘要 |
1,219,723. Self-tapping screws. ILLINOIS TOOL WORKS Inc. 25 April, 1969 [25 April, 1968], No. 21335/69. Heading B3N. [Also in Division F2] A self-tapping screw comprises a screwed shank 14, Fig. 1, having a substantially uniform root diameter, a portion 20 of the thread having a substantially uniform crest diameter, and an included flank angle of 60 degrees, whereas the portion 22, has a larger crest diameter, and an included flank angle of 45 degrees. Portion 22 forms a complete thread form, to or within onehalf pitch of the head 12. The blank is formed with two diameters 29, 30 and the thread is rolled on to the shank by a pair of dies having grooves 42 for portion 20, and deeper grooves 44, for portion 22. |
