The positions of the starting and final tangent points of the gear hob along the tooth axis are shown in the figure.
For straight teeth:
For helical teeth:
Where
E – cut in stroke;
U — cut out stroke;
B – gear width;
H — cutting tooth depth;
Dao — outer diameter of gear hob;
η—— Installation angle of gear hob;
Da — outer circle diameter of gear;
β—— Helix angle of gear.