| 摘要 |
1,004,883. Producing taps; screws. RESEARCH ENGINEERING & MANUFACTURING Inc. March 20, 1962, No. 10743/62. Headings B3A and B3N. A thread-forming screw or tap, having a generally cylindrical main shank portion, is rolled between dies to produce a helical thread which has formed on it, or spaced from it on an extension of the helical thread path, a number of projections for causing swaging of an internal thread in a parent body. The projections lie on a spiral which tapers towards the work entering end. Projections 31, Fig. 5, form threads in a parent body fractionally larger than the threads 30 in order to reduce driving friction. The threads at the entering end may be dispensed with, Fig. 9, the projections still following the helical thread path. To facilitate forming of the projections, depressions may be produced laterally or longitudinally on one or both sides of each projection. Longitudinally assymetrical projections, Fig. 5, or projections formed with displaced depressions 109 and 110, Fig. 28, to form a wave, may be provided. In the case where a screw is to be held tightly without using a lock washer the threads themselves can perform a small amount of swaging. |
