| 摘要 |
<p>1,252,970. Rolling threads; making selftapping screws. U.S.M. CORP. 4 July, 1969 [5 July, 1968], No. 33811/69. Headings B3A and B3M. A pair of thread rolling dies 90, 92 are used to roll a thread on a self-tapping screw blank 74, and simultaneously to breakoff ears 76, 78 on the blank, and to remove an excess portion 80. The ears were produced by a previous swaging operation, and serve to provide cutting edges when broken away. Each die has a threading section 106 and a flat section 110 for breaking the ears. Alternatively, only one of the dies need have a flat section 110. The die 90 additionally includes a tapered protrusion 108 for removing the portion 80.</p> |
