Abstract: The mechanism of spherical hob's cutting internal gear is explained and the new concept of generating gear of spherical hob is presented. Some new equations about the main parameters, the equations of helicoids, the equations of cutting edges and the flank angles of spherical hob are given.

Key words: 螺旋升角, 螺旋线导程, 内齿轮, 球面螺旋面, 球形滚刀