| 摘要 |
PURPOSE:To provide uniform piercing ability by a method wherein a needle point is formed with apexes of three surfaces comprising adjoining two surfaces, with which a square cone being a part having a given length from the needle point is formed, and one surface formed such that other surfaces are ground or polished. CONSTITUTION:By grinding the material of a sewing needle, a tip part is formed in the shape of a square cone. By causing one surface, formed by grinding other two surfaces than adjoining two surfaces with which the square cone is formed, to cross the adjoining two surfaces, the tip part of the sewing needle is formed in the shape of a triangular cone comprising the three surfaces. Even when a slight difference in a grinding depth is produced during grinding of the tip part in the shape of a square cone, since the apex of a triangle is always one point, formation of an acute needle point, formed with one point, to the tip of the sewing needle is facilitated. Thereby, piercing ability of the sewing needle is not uneven and uniform. |
