| 摘要 |
491,680. Self-tapping screws. ROSENBERG, H. June 22,1937, No. 17331. Drawings to Specification. [Classes 83 (ii) and 83 (iii)] A tapping screw having a thread tapering at the entering end has the thread intersected by one or more grooves extending along the body to provide abrupt cutting shoulders, the surfaces of the thread and the grooves being compacted by stamping or rolling. The construction of tapping screw is described in Specification 491,710. |
