Index deviation

The displacement of any tooth flank from its theoretical position, relative to a datum tooth flank.

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Distinction is made as to the direction and algebraic sign of this reading. A condition wherein the actual tooth flank position was nearer to the datum tooth flank, in the specified measuring path direction (clockwise or counterclockwise), than the theoretical position would be considered a minus (-) deviation. A condition wherein the actual tooth flank position was farther from the datum tooth flank, in the specified measuring path direction, than the theoretical position would be considered a plus (+) deviation.

The direction of tolerancing for index deviation along the arc of the tolerance diameter circle within the transverse plane.¹

Notes

1. ANSI/AGMA 1012-G05, "Gear Nomenclature, Definition of Terms with Symbols".