In this paper the author using tensor calculus shows that the equation for induced normal curvature of Nankai University and that of Sakai (Japanese) are of unity.

Using the changing rate of maximum feed-rate as a threshold, the surface of the part is divided into different areas according to the values of normal curvature radius.

This paper describes the establishing process of the equation of working profile curved surface of worm CAM mechanism, the calculation of its pressure Angle and normal curvature.