The traditional inspection of involute gear profile and helix deviations results in plots of deviations from a
perfect involute and from a perfect helix. While this is appropriate for gears with an unmodified profile or
helix, it is not ideal for gears that have intentional modifications. This paper explores the advantages of
looking directly at deviations from the design shape. This type of analysis is implied but not explicitly
stated nor is it pictured in ISO 1 328-1 :201 3. Also presented is a modification to zone based tolerance
evaluation as presented in ISO 1 328-1 :201 3, with limits on the total deviation from design given
graphically.
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