There are many types of ball bearings, each with special features designed for different purposes and to meet specific requirements. The structure of the application, dimensions of the equipment or component which the bearing will be assembled to, and the application environment and conditions need to be confirmed. It is necessary to take several factors into account in order to decide the bearing part number and specification that your application will require. Additionally, the market is an important factor in your bearing part number and specification selection. Setting an overarching standard for the selection of bearings is difficult, as each type of the bearing has different criteria for application-influencing factors. Therefore, you should always review your selection of bearings according to your application’s specific requirements. Following are a few generic guidelines to help you through some of the factors that influence the selection of ball bearings.
Structure and function of the equipment
The required dimensions and performance should be based on an understanding of the structure and function of the equipment involved. The scaling down of equipment has made bearing structure limitations more severe. We recommend taking into account the items listed below and selecting properly, to achieve the required bearing performance.
Application environment (temperature, humidity, vibration, dust, etc.)
The bearing material, retainer and lubricants are selected based on the ranges of predicted temperature and humidity. The proper preload and lubricant are selected based on the vibration conditions. The presence of dust influences the selection of the shield or seal type. In certain bearing operation conditions, the temperature of the ball bearings can sometimes be higher than environmental temperature.
Loads applied to ball bearings
Selecting the bearing dimension, or Part Number, should be based on the magnitude, position, and direction of loads applied to the bearing. The equipment’s structure should be taken into account to determine if excessive loads would be applied. If so, it will be necessary to select a larger size bearing or decrease the loads in the application.
Material and dimensions of the shaft and housing
When it comes to choosing the bearing dimensions and tolerances of bore, outer diameter, and width, the decision should be based on dimensions and material of the shaft and housing. Temperature changes will cause fluctuations in bearing internal clearance, and it is important to take this into account. There are differences in linear expansion coefficients between either shaft or housing material and bearing material.
RPM, Rotation Precision, Rotation Ring
Dimensional tolerance, retainer, clearance, preload, and lubricant are selected based on speed, rotation precision, and rotation conditions (continuous/intermittent/back and forth/outer or inner ring rotation).
Torque can be classified into either starting torque or running torque. When an application is torque sensitive, enclosure types, lubricant selection, fill amount and retainer type and material, need to be considered carefully.
When an application is noise sensitive, it is necessary to take bearing noise characteristics, lubricants and preloads into account. Care must be taken during installation and handling. Improper installation, handling damage, or contamination could worsen the noise level.
JIS B 1518 / ISO 281 does define rating life for ball bearings, however, bearing life can be defined in a variety of ways. The life of a bearing is not only affected by the application requirements, but also by the progress of degradation for the required performance levels, such as noise, torque, runout, etc. When it comes to bearing life, consider rating life, noise life, performance life, and lubricant life.
Environmental, health, and safety regulations on certain substances have been put into place in recent years. Determining whether your application involves any regulated substances that are harmful to humans or the environment is critical. Substances harmful to the environment and humans are restricted.