When choosing a fit, the first consideration is the type of load the ferrule will carry. Generally, there are three types of load bearing types of ferrules: 1 fixed load The synthetic radial load acting on the ring is borne by the local area of the raceway of the ring and transmitted to the opposite area of the shaft or bearing seat. This load is called a fixed load. Fixed loads are characterized by the resultant radial load vector being stationary relative to the ferrule. Neither the ring nor the resultant radial load rotates or rotates at the same speed are stationary loads. A looser fit is available for ferrules that are subject to a fixed load. 2 rotating load The synthetic radial load acting on the ring rotates along the circumferential direction of the raceway and is borne by various parts in turn. This load is called rotational load. Rotational loading is characterized by the resultant radial load vector rotating relative to the ferrule. There are three cases of rotating loads: (1) The load direction is fixed and the ferrule rotates; (2) The load vector rotates and the ferrule remains stationary; (3) The load vector and the ferrule rotate at different speeds. 3 Swing load and indeterminate load Sometimes the direction and magnitude of the load cannot be determined exactly. For example, in high-speed rotating machinery, in addition to the load bearing the weight of the rotor in a fixed direction, there is also a rotating load caused by unbalanced mass. If this rotating load is greater than the fixed load Much larger, the resultant load is still a rotating load; and if the rotating load is much smaller than the fixed load, the resultant load is a swinging load. Both rotational and oscillating loads are constantly changing in magnitude and direction. In the variable working state, the load on some ferrules may be a rotating load, a fixed load, and a swinging load. This load is called an indeterminate load. Swing loads and indeterminate loads should be treated equally with rotating loads in terms of fit. Too loose fit will cause damage to the mating surface. For ferrules that rotate relative to the load direction and shafts or seat holes, transition fit or interference fit should be selected. The size of the interference is based on the principle that when the bearing is working under load, the ferrule does not produce “creep” phenomenon on the mating surface on the shaft or in the seat hole. When the load is very light, or the ferrule occasionally rotates at a low speed under heavy load, a transition fit can be used. At this time, the shaft surface should have higher hardness and smaller surface roughness. For heavy load occasions, it should usually be tighter than that for light load and normal load occasions. The heavier the load, the greater the interference should be.  

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