Gear oil has many incomparable characteristics. If it can effectively prevent rust, this is what other additives do not have.

According to the geometrical relationship, the intersection line between the normal plane and the indexing cylindrical surface at a point on the helical cylindrical gear tooth line is an ellipse.　　

The corresponding machines and cutters are hobbing machine and hobbing cutter, gear shaper and gear shaper cutter, horizontal milling machine and gear milling cutter