involute gear with double pressure angles
Boreholes on Circular Arc with Inclined Plane
Double helical ribbons impe
helical gear
螺旋齿轮
斜齿轮副
圆柱斜齿轮
渐开线斜齿轮
斜齿圆柱齿轮
针齿轮
斜齿轮
圆柱斜轮
the heat exchanger with helical inserts
complex wheel teeth gear set
gear with addendum modification