The performance of a gear pair depends largely on the manufacturing precision. The production cost
consequently increases with accuracy. The gear designer is thus faced with the decision as to the
precision level really needed for a given application.
The ANWAGMA IS0 1328-1 for Cylindrical Gears [i], which sets 13 gear accuracy levels with
allowable lead and form deviations for gearwheels, specifies mandatory inspection items and also
contains criterions of quality given as useful information. This paper aims to study the effects of the
tolerances on helix formfj and slopehp deviations which, while not individually subject to mandatory
tolerances, are recognised to have a significant influence on performance of a gear pair.
The deviations are studied and compared for an helical gear of grades 5 and 7. The investigation is
conducted from the perspective of the longitudinal load distribution in view of form and lead deviations,
and its influence on tooth fillet bending and surface contact stresses.