The parameters on the rear cone surface (big end) of bevel gear are standard values. Note that the back cone is "oblique" on the drawing, with the height of the tooth top, the height of the tooth root and the height drawn along the back cone "oblique". The diameter of the cyclotron is drawn along the radial direction and intersects with the back cone, and the sub-cone (line) passes through this intersection.
Helical gears are based on normal parameters. Because the gear cutter parameters are standardized, both spur gears and helical gears can be machined, and when machining helical gears, they are all cut along the normal direction.