Page 91 - Gear Technology Solutions

undercut and will maintain a healthy profile and root fillet. The center distance
in case of V0 gearing is identical to that without profile shift.

The effect of a positive profile shift is shown in Figure 8. The gear to the right
is in mesh with its generating rack in a non-profile shifted configuration. It can
be seen in the graphic that the root fillets show a beginning undercut. The
positive profile shift at the left side gear increases the effective pressure angle
of the involute because a part of the involute with a larger radius is used for the
flank. Positive profile shifted gears do not have a smaller base circle, however,
the root moves away from the base circle to a larger radius.

Figure 8: Elimination of undercut with profile shift

The profile shift factors of pinions and gears are often defined to optimize the
sliding conditions within the flank surface, or they are used to balance the tooth
thickness in the root between pinion and gear. This is a definite restriction if
undercut is an issue. Small amounts of undercut do not present a problem in
most cases. Small amounts of undercut can be seen as a way to realize a
certain gear design and avoid interferences or rolling disturbances.

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