Standards Development

Scope

This document establishes a tolerance classification system relevant to manufacturing and conformity assessment of individual worm and worm wheel of cylindrical worm gear pair with manufacturing specification parameters, mathematically defined for each of the five worm flank profile types A, C, I, K and N as defined in ISO 10828. This document can also be applied to modified flank shapes which can be produced using the same manufacturing processes as the flank shapes mentioned. This document relates to analytical measurement methods and single flank composite measurement methods.

It specifies definitions for worm and worm wheel gear flank tolerance terms, manufacturing specifications data to be reported in the drawing, and verification parameters for conformity assessment, with tolerance classification formulas, the structure of the flank tolerance class system, allowable values.

Definition of right and left flank as well as right and left helix are defined as in ISO 10828.

Single flank testing shall be an alternative or a complement to coordinate measurements when specific agreements are needed between costumer and supplier.

Double flank tolerances are not covered in this document as ISO 1328-2 can be applied as well ISO/TR 10064-2 for measurement methods. For consistency of worm gear tooth flank tolerancing, the practice of double flank measurements for single enveloping cylindrical worm gear is significantly critical:

— one side due to the difficulty to set-up the datum axis of the worm in the datum midplane of worm wheel;

— the other side as any centre distance variation of the worm gear set during meshing induces bias in the results as kinematic conjugacy of tooth flanks is impacted.

Gear design is beyond the scope of this document.

Surface texture is not considered in this document. For additional information on surface texture or waviness of tooth flanks, see ISO/TR 10064-4.