The main role of the pinhole is used to suture penetration, so that the pinhole in the suture can move back and forth and the completion of the course into a seam.

• 在更换机针的尺寸时，不必要每次调整梭钩，所以在**的顶部磨制一个弧形凹点。凹痕的半径和所用的砂轮相同（现在砂轮磨削已被模压替代）。