The relation formula for the largest radius of rounded root of bolt with the cutting depth at the root of the nut, and the pitch of the nut is given.

• 摘要推导出螺栓螺纹根部最大圈弧半径与螺母螺纹小径处的削平高度、螺距的关系，探讨了增大圆弧半径的途径；