| 摘要 |
942,417. Making screws. GKN SCREWS & FASTENERS Ltd. Oct. 1, 1962 [Oct. 4, 1961], No. 35712/61. Heading B3A. A method of making a screw adapted to remove paint from an internal thread with which it is engaged comprises forming a blank of circular cross-section, pressing a pair of diametrically opposed flats at one end of the blank to produce an oval cross-section projecting radially beyond the major diameter of the blank, thread rolling the blank to produce, at the said end, two diametrically opposed positions where the thread is interrupted by a groove having a cutting edge formed along the side which when engaged with an internal thread is leading. A pair of diametrically opposed flats are pressed on the end portion of a blank 10 having a taper 11 to produce raised portions 13 extending radially beyond the blank diameter D. The dimension X across the flats is less than the core diameter " Y " of the threaded screw. The blank is finally thread rolled in a known manner to produce a thread 14 interrupted by a pair of grooves formed by the re-displacement of the raised portions 13. The material flow produced by the rolling forms a cutting edge 16 having an undercut portion 17 on the leading side of the grooves and on the trailing side a sloping surface 18. The screw may also be used as a self tapping screw for use with resinous synthetic materials. |
