Defination of Basic Hob Profiles

The basic hob profile is the normal sectional profile of an imaginary tooth rack, which meshes with the workpiece teeth under the following conditions: 

1), The basic profile line of the rack rolls on a defined pitch circle diameter of the workpiece. 

2), The pitch of the rack is equal to the pitch on the pitch circle diameter, 

3), Meshing with the workpiece takes place:

Standardized basic hob profiles are shown in: DIN 3972 and DIN 58412 standard