Posted by BillS on March 04, 2013 at 18:01:02:
In Reply to: Re: PFAUTER P900 DEFFERENTIAL CHANGE GEARS posted by chuck tucker on March 04, 2013 at 15:19:31:
Sorry - I forgot to say Normal Diametral Pitch, but "DP" is commonly understood to be "normal" to teeth, where "Transverse DP" is DP measured parallel to gear face.
NDP is used in hob formulas for differential gear ratio where helix angle is part of the formula. Normal Module is likewise used for the same reason.
When differential formula uses Gear Lead instead, DP and Helix angle are "absorbed" into Gear Lead and no longer appear in the differential formula.
I probably made a confusing mess here - some one else can probably show this better than I have.