In this paper, calculating method of lead angle of helical gear by measuring span length of length bar and base tangent length is put forward, and lead angle calculating formula is deducel.

• 分析齿轮主要参数，提出用测量跨棒（球）距和公法线长度计算斜齿圆柱齿轮螺旋角的测绘方法，并推导出螺旋角的计算公式。