Miniature and instrument bearings are normally made of either 440 stainless steel for applications that require corrosion resistance and 52100 chrome steel for maximum fatigue life. These materials are heat treated to achieve optimum hardness and dimensional stability and they are suitable for most applications.
Static vs Dynamic – The main difference between a static and dynamic load lies in the forces produced by the weight of an object. When static, the load remains constant and doesn’t change over time. With a dynamic load, some outside factor causes the forces of the weight of the load to change. Some of the factors that can affect a load and make it dynamic include, Movement, Tension and Outside Force.
Shields vs Seals
A shield (non-contact) or seal (contact) is often installed to retain lubricant and to prevent contamination from entering the bearing raceways. Shield and seal configurations can be either single or doubled sided. You can regrease a shielded bearing, but it is not suggested for a sealed bearing. Most shields are Metallic, seals are usually made from elastomeric materials.
The retainer, (ball separator), is used to separate and position the balls at equal intervals around the bearing raceways. Retainers are available in two standard types. The most common is a 2-piece closed ball pocket design known as a ribbon retainer. The crown retainer is a single piece open ball pocket design.
The ABEC scale is an industry accepted standard for the tolerances of a ball bearing. There are five classes from largest to smallest tolerances: 1, 3, 5, 7, 9. The higher ABEC classes provide better precision, efficiency, and the possibility of greater speed capabilities.
Internal clearance is the internal radial looseness in a bearing and is the measured value of the total radial movement of the outer ring with respect to the inner ring in a plane perpendicular to the bearing axis. Ball bearings are assembled to radial play values depending upon the desired range. The radial play is determined by the actual raceway diameters and ball diameter.
Oil or Grease