Page 143 - Gear Technology Solutions

The outline in a cross-sectional view of a pinion and a gear is shown in Figure 3.
Pinion axis and gear axis intersect at the labeled crossing point. The common
pitch line of pinion and gear is also labeled in the graphics. Before the profile shift,
the pitch line is also identical to the reference pitch line, which divides the profile of
both members into the addendum and dedendum. A positive pinion profile shift
and a positive gear profile shift are applied parallel to their common pitch line. The
positive profile shift means that the cutting tool moves away from the respective
members and increases their diameters. The pinion pitch line is still maintained
while the new profile dividing reference pitch is shifted down, shown as a dashed
line below the common pitch line. Also, the gear pitch line is maintained at the
common pitch line location, while the new reference pitch line of the gear is shifted
up, shown as dotted line. In order to mate and roll pinion and gear, which have
now increased diameters, the reference pitch lines have to be moved back to the
location of the original common pitch line. These moves can only be accomplished
with a parallel shift of the pinion axis with the amount of the pinion profile shift, but
in the opposite direction of the profile shift, and with a parallel shift of the gear axis
with the amount of the gear profile shift but in the opposite direction of the gear
profile shift. In the new axis location, the original crossing point moved to the new
crossing point location.

Figure 4: Enlarged detail A from Figure 2

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