(1). The configuration of early roller bearing in rolling mills was different from today's. At that time, the main setup was to install two spherical roller bearings in parallel on the same roller shaft. This configuration generally met the production requirements of the time, allowing rolling speeds up to 600 rpm. However, as speeds increased, its shortcomings became more pronounced: short bearing life, high consumption, low product precision, severe wear on the roller shaft, and significant axial movement of the roller.

(2). Four-row cylindrical roller bearings with thrust bearings feature a tight fit between the cylindrical roller bearing inner diameter and the roller neck, capable of withstanding radial forces. They offer advantages such as high load capacity, high limiting speed, high precision, detachable and interchangeable inner and outer rings, ease of machining, low production costs, and easy installation and removal. Thrust bearings withstand axial forces, and the specific structural type can be selected based on the mill's characteristics. For heavy loads at low speeds, thrust roller bearings are used to bear thrust loads with minimal axial play. When rolling speeds are high, angular contact ball bearings are employed, not only for their high limiting speed but also for the ability to precisely control axial play during operation. This ensures tight axial guidance for the roller, capable of withstanding general axial load forces.

This bearing configuration offers not only a long service life and high reliability but also features such as high precision in rolled products and ease of control. As a result, it is widely used in various applications, including support rolls for wire rod, plate, foil, twin-roll, cold rolling, and hot rolling mills.

(3). Four-row tapered roller bearings can withstand both radial and axial forces, eliminating the need for thrust bearings, making the main unit appear more compact. The inner diameter of the tapered roller bearings is loosely fitted with the roller neck, allowing for easy installation and removal. However, sliding creep may occur due to the loose fit, so the inner diameter is often machined with spiral oil grooves. This configuration is still widely used today, such as in the work rolls of four-roll hot and cold rolling mills, billet machines, steel beam rolling mills, and other rolling mill applications.