其二为一种修整的线接触，展成的等螺距齿面与理论轨迹曲面沿某一空间曲线近似相切。

The new tooth surface can be prolonged by the normal profile of the internal toroidal surface, or replaced by an equal pitch helical surface.

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通过数学分析将麻花钻前刃面端截面曲线归纳成广义渐开线；

With mathematic analysis the end section curve of front blade of twist drills is induced into generalized involute;

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