Diagram Adaptation Slope Modification fHa

[[Is...]]

Noticed in the fHa drop down there is a Slope modification which can take leaning profile charts and make them line up with the nominal. Just wanted some clarification on when this would be used? I assume when a slope modification is provided in the gear data?

[[Ky...]]

I think I saw it once on a customer's print a few years back. The nominal helix angle was zero, but they wanted the tolerance for fHb to be around a different nominal angle. I could not tell you why they wanted that, though. I don't know much about the design of gears, I just measure them.