How to select 608 2RS bearings?

1. Selection of 608 2RS bearing clearance

The operating conditions of bearings, including the rotational speed, temperature, and fit tolerance of bearings, are directly related to the selection of bearing clearance.

Generally, motors with a rotational speed of less than 3500 revolutions per minute mostly use cm clearance. For high-temperature and high-speed motors, a relatively larger clearance is required. In cases where a tighter fit is used, there is a large temperature difference between the inner and outer rings, a need to reduce friction torque, and deep groove ball bearings bear a large axial load or need to improve the self-aligning performance, a large clearance group is suitable. When higher rotational accuracy is required or axial displacement needs to be strictly limited, a small clearance group is suitable.

2. Selection of 608 2RS bearing precision

The precision of rolling bearings is divided into (main) dimensional precision and rotational precision. The precision grades have been standardized and are divided into five grades: P0 grade, P6 grade, P5 grade, P4 grade, and P2 grade.

3. The functions of lubrication are as follows:

1) Lubricate all parts of the bearing to reduce the rotational friction between the raceway surface and the steel ball, the sliding friction between the steel ball and the cage, and the sliding friction within the cage and the raceway guiding surface.

2) Take away the heat generated by internal friction of the bearing and other heat coming from the outside to prevent the heating of the bearing and the deterioration of the lubricant.

3) Make the rolling contact surface of the bearing often form an appropriate oil film to alleviate the concentrated stress of impact load and extend the fatigue life of the bearing.

4) Prevent the corrosion of steel balls, raceways, and cages as well as the invasion of garbage, foreign matters, and moisture to achieve rust prevention and dust prevention of the bearing.

Distinguished according to temperature and working conditions: Greases can be classified according to their allowable operating temperatures. The consistency and lubricating ability of greases are affected by the operating temperature. Bearings operating at a certain temperature must choose greases with the correct consistency and good lubricating effect at the same temperature. Greases are manufactured for different operating temperature ranges and can be divided into low-temperature (lt), medium-temperature (mt), and high-temperature (ht) greases. At the same time, there is a type of grease called ep (extrusion resistant) or em (extrusion resistant and added with molybdenum disulfide), with additives added to strengthen the strength of the lubricating oil film.

4. Cage

The cage plays the role of equally spacing and isolating the rolling elements in the bearing, guiding and driving the rolling elements to rotate. In separable bearings, the cage also plays the role of preventing the rolling elements from falling. According to different processes, cages can be divided into: stamped cages, turned cages, molded cages and pin cages. According to different materials, cages can be divided into steel cages, copper cages, nylon cages and phenolic resin cages.

5. Bearing steel materials

High-carbon chromium bearing steel

Suitable for bearings with an operating temperature lower than 200℃. Commonly used steels are GCr4, GCr15, GCr15SiMn, GCr15SiMo, GCr18Mo.

Carburized bearing steel

It can withstand large impact loads and fracture toughness, and also has strong wear resistance and contact fatigue strength. Suitable for bearings with an operating temperature lower than 150℃. Commonly used steels are G20Cr, G20CrMo, G20CrNiMo, G20CrNi2MoA, etc.

High-temperature bearing steel

In addition to having the properties of general bearing steel, it also has certain high-temperature properties such as high-temperature hardness and high-temperature wear resistance. Commonly used steel grades: CrMo4V with a maximum service temperature of 315℃; Cr14Mo4V with a maximum service temperature of 425℃; W6Mo5Cr4V2 with a maximum service temperature of 425℃.

Stainless steel bearing steel

It has extremely high hardenability, excellent mechanical properties and corrosion resistance. Commonly used steel grades: 9Cr18, 9Cr18Mo, 1Cr13, 2Cr13, etc.

For more information, feel free to contact QIBR