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Miniature & small ball bearings

2.Application Structure, Required Performance, Environment

Review the dimensions of the location where the bearing is to be mounted, the expected performance of the bearing, the operating environment and conditions.
In recent years, the size of equipment has been reduced, and there are many cases where there are restrictions on the structure. However, in order to maintain the required performance for a long period of time, it is recommended to provide as much space as possible.
It is also important to take market factors into account for selecting the bearing part number and specification.

Application structure and functions

Determine the size envelope for the bearing by reviewing the structure and function of the application.
Take the dimensions of the inner diameter, outer diameter, and width into consideration when choosing a bearing size.

Operating environment (temperature, humidity,vibration, dust, etc.)

The bearing material, retainer, lubricant, etc. are determined from the upper and lower limits of the assumed environmental temperature and humidity.
The vibration conditions are taken into consideration when determining preload, lubricant, etc.
The cleanliness of the system influences the selection of shield or seal type. Depending on the operating condrtions, bearing temperature is occasionally higher than ambient temperature.


The dimension (size) of the bearing is selected based on the magnitude, position, and direction of loads applied to the bearing.
It is necessary to review the structure of the equipment to determine if excessive loads would be applied to the bearing.
If so, select a larger size bearing or reduce the loads.

Materials and dimensions of shaft and housing

The dimensions and tolerances of the bore diameter, outer diameter and width of the bearing are determined based on the dimensions and materials of the shaft and housing.
Temperature changes can affect the bearing internal clearance if there are differences in linear expansion coefficients of the shaft, housing, and bearing materials.

Rotational speed, rotation precision, rotating ring

The bearing's dimensional tolerances, retainers, clearances,preloads, lubricants, etc. are determined based on rotational speed, rotation precision, rotation conditions (continuous/intermittent/reciprocating rotation,innerring/outer ring rotation).


There are two types of torque: starting torque and rotating torque.
In particular, when there is a low torque requirement it is necessary to consider the type of lubricant, the fill amount and the retainer.


When an application is noise sensitive, the acoustic properties of bearing components and lubricants need to be considered.
It is also necessary to review other conditions around the bearing, such as the preload, imbalance and resonance of the rotor during operation of the bearing.


The service life is defined in JIS B 1518, but it is not strictly defined elsewhere.
Life is defined in various ways depending on the application and the degree of performance deterioration(sound, torque, runout, etc.)requirements from each customer.
In general, life can be calculated as rating life (fatigue life of material), modified rating life, functional life (performance such as sound, torque and vibration) and lubricant life.

Restricted substances

In recent years, various regulations have been established for the environment, health and safety.
It is necessary to confirm if regulated substances are present.
Substances that are harmful to the environment and humans are restricted.

Other special application conditions

In certain applications, proper care must be taken into how the bearing is exposed to special operating conditions. Applications where chemicals, gases, salt water, etc. are present, where dust cannot be generated by the bearing, and where electricity could flow through the bearing are all examples of special operating

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