Tapered roller bearings are separate bearings. The inner and outer rings of the bearing have tapered raceways. This type of bearing is divided into different structural types such as single-row, double-row and four-row tapered roller bearings according to the number of rows of rollers installed. Single row tapered roller bearings can bear radial loads and axial loads in one direction. When the bearing is subjected to a radial load, an axial component force will be generated, so another bearing that can withstand the axial force in the opposite direction is needed to balance it. The ability of single row tapered roller bearings to withstand axial loads depends on the contact angle, that is, the angle of the outer ring raceway. The larger the angle, the greater the axial load capacity. The most commonly used tapered roller bearings are single row tapered roller bearings. In the front wheel hub of the car, small-sized double-row tapered roller bearings are used. Four-row tapered roller bearings are used in heavy machines such as large cold and hot rolling mills.