| 摘要 |
617,321. Self-tapping screws. GASKELL, C. R. Jan. 16, 1947, No. 1498. Convention date, April 14, 1943. [Class 83 (iii)] [Also in Group XXV] A self-tapping, parallel thread screw for use in wood or similar material has a single inclined plane surface 7 extending from a diametrical width at the outer end of the screw to the outer periphery of the threads, the length of this surface being greater than the diameter of the screw and the marginal edges thereof forming cutting edges. The surface is inclined at an angle of approximately ten degrees with the axis of the screw while the front and rear faces of the thread make angles of the order of 35 and 15 degrees, respectively with the vertical. |
