大部分金属切削操作需要从工件上切下碎片或碎屑，来获得所需工件的外形和尺寸。
The majority of metal-cutting operations involve the separation of small segments or chips from the workpiece to achieve the required shape and size of manufactured parts.
使用的刀具外形必须正好与要切削螺纹的轮廓一致，即三角形刀具必须用于三角形螺纹等等。
The form of the tool used must exactly coincide with the profile of the thread to be cut, i. e. , triangular tools must be used for triangular threads, and so on.
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