Page 60 - Gear Technology Solutions

Figure 9: The correct pinion and gear pitch surfaces

Although the pitch elements are hyperbolic and not conical, it is possible to use
conical faces for the blanks of pinion and gear. If point P in Figure 9 was cho-
sen at the center of the face width, then line (nop-nog) can be used as a normal
vector to define the face angle a blank with straight face cones if the hypoid set
was manufactured by face hobbing, which implies parallel depth teeth.

Straight face cones will merely influence the top root clearance of the gearset
in the range of 30 to 60 microns. Using straight face cones will not change the
form of the pitch surface nor will it influence the base surface (root surface).
Those functional surfaces are given by kinematical relationships and have to
be considered when thinking about the shape of the surface of action. No
plane of action can exist between two hyperbolic base elements. The correct
surface of action is curved and warped, as shown in Figure 10.

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