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Bearing Basics

Bearing Selection

Ball bearings are available in a variety of types, configurations, and sizes. There are several important factors to consider when choosing the proper bearing for you application. These factors include materials, cages, precision grade (ABEC), shields & seals, radial play, and lubricant.

Materials

Ball bearings are typically made of either stainless steel or chrome alloy steel. The reliability and high quality of ZXB ball bearings are the result of development in metallurgy, modern manufacturing techniques, and our strict methods of quality control. ZXB Bearing offers stainless steel for applications that require corrosion resistance, and chrome alloy steel for greater fatigue life. Both of these materials are heat-treated to achieve the appropriate hardness and dimensional stability, and are suitable for most applications.

Cages

ZXB Bearing has several cage types available for a variety of range of load, speed and temperature requirements. The most commonly used metallic cages are the one piece crown, the two piece ribbon and the two piece riveted types. These cages are generally considered to be interchangeable, although one may be more suitable for a particular application. Also available for some sizes are cages made of molded and machined nylon. Proper selection of a bearing cage can be extremely important. Our engineers can provide recommendations for any special requirements.

Precision Grade (ABEC)

Several factors should be considered in selecting a bearing's precision (ABEC) grade, including radial and axial runout requirements, bore and O.D. fits, and acceptable noise/vibration levels. Grades 1 and 3 are preferred for most standard applications. Higher grades typically include superior race finish and geometry. ZXB Bearing recommends these grades for precision assemblies where low noise/vibration, minimal runout and maximum life are important considerations.

Shields and Seals

Shields and seals are used to retain lubricant and to help prevent contamination from reaching internal bearing surfaces. Metal shields are popular for many applications and are available for most sizes. The effect of shields on bearing torque or running noise is insignificant.

Seals are generally made of synthetic rubber and offer improved lubricant retention and greater protection from contaminants. However, seals can greatly increase torque and limit overall operating speed.

Radial Play

Radial Play (or internal clearance) is the amount of internal radial looseness between the balls and races. Ball bearings are assembled to radial play values based upon a desired range. Radial Play within a ball bearing is necessary to accommodate thermal expansion, the effects of interference fit, and to control the amount of axial play. In applications where of extreme temperature, speed, load, or amount of axial play is important, our engineering department should be consulted for recommendations.

Lubricant

Selection of the lubricant can be critical. Proper lubrication helps to minimize friction and prevent wear between parts moving relative to one another. Lubricant also allows for the dissipation of frictional heat, as well as providing protection from moisture, corrosion and contaminants.

Unless torque is a problem, grease is generally preferred, as it is less susceptible to migration and leakage. However, grease can also increase bearing torque, depending on the type and quantity of used. Grease is typically applied with special equipment in a clean room environment. The preferred amount of grease, or fill amount, is normally specified as either a percentage (such as 30% +/- 5%) or a measurement range (such as 120-160 mgs). Oil is also applied using special equipment, but the amount is not normally specified.

Many lubricants are available for a wide range of conditions and requirements. Each has particular characteristics that make it suitable for specific applications. ZXB engineers can help select the lubricant best suited for your application.

 

 

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