This part of ISO 1328 establishes a tolerance classification system relevant to measurements on tooth flanks of individual cylindrical involute gears. It specifies definitions for gear flank tolerance terms, the structure of the flank tolerance class system, and allowable values. It is strongly recommended that any user of this part of ISO 1328 be very familiar with the methods and procedures outlined in ISO/TR 10064-1. Use of techniques other than those of ISO/TR 10064-1 combined with the limits described in this part of ISO 1328 may not be suitable. This standard provides the gear manufacturer and the gear buyer with a mutually advantageous reference for uniform tolerances. Ten flank tolerance classes are defined in this standard, numbered 2 through 11, in order of decreasing precision. Equations for tolerances and their ranges of validity are provided in 5.3 for the defined accuracy of gearing. In general, these tolerances are applicable to the following ranges: 5 <= z <= 1000 or 15 000 / mn whichever is less 5 mm <= d <= 15 000 mm 0.5 mm <= mn <= 70 mm 4 mm <= b <= 1200 mm ß <= 45° where d is reference diameter; mn is normal module; b is facewidth (axial); z is number of teeth; ß is helix angle. See clause 4 for required and optional measuring methods. This standard does not apply to enclosed gear unit assemblies, including speed reducers or increasers, gear motors, shaft mounted reducers, high speed units, or other enclosed gear units which are manufactured for a given power, speed, ratio or application. Gear design is beyond the scope of this standard. The use of the flank tolerance classes for the determination of gear performance requires extensive experience with specific applications. Therefore, the users of this standard are cautioned against the direct application of tolerance values to a projected performance of unassembled (loose) gears when they are assembled. Refer to the latest ISO Publications Index for applicable standards. Surface texture is not considered in this standard. For additional information on surface texture, see ISO/TR 10064-4.