| 摘要 |
<p>Sewing machine needles are produced by (a) drawing a needle stem to a predetermined value of the transverse section, while taking account of the expansion of a needle blank at the moment of pressing, (b) pressing the drawn needle stem through a matrix to obtain a needle blank with an oblong transverse section, (c) placing the oblong transverse section of the needle blank in the matrix block in such a manner that the large diameter is aligned with the pressing direction of the matrix blocks, these blocks being each provided with a projection for forming a throat on the needle blank, and (d) forming a needle body with a throat by pressing the blank between the matrix blocks. The quality of the needle blank and the expansion of the blank at the moment of pressing are considered so that the diameter of the needle blank can be determined. The transverse section of the needle blank may be reduced by a rotary stamping machine to an area which is 1.01-1.1 times the transverse section of the finished needle.</p> |
