The interference of rotating ferrule should also be small within the possible range. As long as the influence of thermal expansion at the working temperature and the influence of centrifugal force at the highest speed are ensured, the creep or sliding of the tight fitting surface will not be caused. According to the working load and bearing size, the fixed ferrule selects a very small clearance fit or interference fit. Too loose or too tight is not conducive to maintaining the original accurate shape.