In the context of the development of a 500’000 rpm miniaturized permanent magnet motor, a 3D analytical model for the assessment of mechanical stresses is presented. The significant mechanical stresses and thermal constraints encountered at such speeds are limiting factors, especially for the permanent magnets. The model, taking into account the axial stress component and the temperature, can be used for fast multiphysics designs. It has been validated by FEM at several temperatures, geometries and speeds with low a error. The model is finally combined with an analytical electromagnetic model to illustrate the interactions with a motor.