This part of ISO 6336 specifies the fundamental formulae for use in tooth bending stress calculations for involute internal and external spur and helical gears with a minimum rim thickness under the root of sR ≤ 3,5 mn. All load influences on tooth stress are included insofar as they are the result of loads transmitted by the gearing and insofar as they can be evaluated quantitatively (see 4.1.1).
The given formulae are valid for spur and helical gears with tooth profiles in accordance with the basic rack standardized in ISO 53 (see introduction). They may also be used for teeth conjugate to other basic racks if the virtual contact ratio is less than εan = 2,5.
NOTE 1 - See 4.1.1 c) and 5.3 for restrictions in the case of method C.
The load capacity determined on the basis of permissible bending stress is termed "tooth bending strength". The results are in good agreement with other methods for the range as indicated in ISO 6336-1.
The user of this part of ISO 6336 standard is cautioned that when the method specified is used for large helix angles and large pressure angles, the calculated results should be confirmed by experience as by method A.