ISO 10300-3:2014 specifies the fundamental formulae for use in the tooth root stress calculation of straight and helical (skew), Zerol and spiral bevel gears including hypoid gears, with a minimum rim thickness under the root of 3,5 mmn. All load influences on tooth root stress are included, insofar as they are the result of load transmitted by the gearing and able to be evaluated quantitatively. Stresses, such as those caused by the shrink fitting of gear rims, which are superposed on stresses due to tooth loading, are intended to be considered in the calculation of the tooth root stress, σF, or the permissible tooth root stress σFP. ISO 10300-3:2014 is not applicable in the assessment of the so-called flank breakage, a tooth internal fatigue fracture (TIFF).
The formulae in ISO 10300-3:2014 are based on virtual cylindrical gears and restricted to bevel gears whose virtual cylindrical gears have transverse contact ratios of Ɛvα < 2. The results are valid within the range of the applied factors as specified in ISO 10300-1 (see also ISO 6336-3). Additionally, the given relationships are valid for bevel gears, of which the sum of profile shift coefficients of pinion and wheel is zero (see ISO 23509).