| 摘要 |
1,065,905. Self-tapping screws; rolling screw threads. P. L. ROBERTSON MFG. CO. Ltd. Nov. 17, 1965, No. 48879/65. Headings B3M and B3N. [Also in Division F2] A self-tapping screw is formed from a blank (1) of elliptical cross-section, by rolling the blank between dies (2), (2), Fig. 7 (not shown). The dies are inclined to the axis of the screw so as to be closer together at the head end of the screw, so that the screw thread (6) adjacent the screw head (3) is formed with a circular cross-section, whereas the screw thread (6) at the opposite end of the screw has an elliptical cross-section. The major diameter of the threads at the cutting end of the screw is slightly larger than the threads adjacent the head. The threads (6) may terminate short of head 3, and the screw may have a pyramidal, or conical point. The screw may be hardened, and may have two starts.
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