In this paper, the deformation-mechanical support effect is investigated on the basis of a simulation study, focusing on the classical fatigue limit assessment of steel shafts. Starting from a short overview of notch approximation methods and their transfer to the deformation-mechanical support effect in fatigue limit assessments, an elastic-plastic FEM calculation series with 22,100 cases is presented. Currently used calculation methods for the deformation-mechanical support effect are examined in comparison with the simulatively determined stress in the alternately elastic-plastic deformed notch root. It is shown that in some cases significant strength reserves can be utilized for design calculations if the effect for notched shafts is estimated more accurately. In contrast, the opposite is true for very mildly notched shafts, especially under tension-compression load. In these cases, the deformation-mechanical support effect is overestimated by current methods, i.e. the design is on the unsafe side. A new method is presented as a pragmatic solution to the problem, which allows the user to more accurately consider the effect in the dimensioning by taking into account notch effect, load, and the material. By using the nominal cross-section (outside and inside diameter), which is normally distinct in shafts, it was possible to avoid the use of the plastic notch factor. The method does not require any additional simulations, can be used with almost no additional effort, and is therefore also applicable to nominal stress-based concepts. All evaluated, results as well as detailed information on all models, are provided. The authors invite the reader to critically examine the results and/or to use them for own analyses.