| 摘要 |
1,009,630. Self-tapping screws. GENERAL AMERICAN TRANSPORTATION CORPORATION. May 2, 1963 [May 7, 1962], No. 17344/63. Heading B3N. [Also in Division F2] A self-tapping screw comprises a screwed shank 11, having a leading end D with angularly spaced triangular shaped flat faces 14, Figs. 1, 4, 5, forming cutting edges 13, and a countersunk head 16, Figs. 1, 2, the end 18 of which has a tool-engaging recess 19, and is serrated, and the surface 17 of which has a number of thread convolutions 21 thereon. The pitch of thread 21 decreases from turn to turn as shown at P10-P12, Fig. 2, and the constant pitch P1 of thread 15 is greater than the variable pitch of thread 21.
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