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Principles of Bearing Selection and Application

Principles of Bearing Selection and Application

A bearing arrangement does not only consist of rolling bearings but includes the components associated with the bearings such as the shaft and housing. The lubricant is also a very important component of the bearing arrangement because it has to prevent wear and protect against corrosion so that the bearing can deploy its full performance. Beside these, the seal is also a very important component, the performance of which is of vital importance to the cleanliness of the lubricant. Cleanliness has a profound effect on bearing service life - which is why lubricants and seals have become part of the SKF business.

To design a rolling bearing arrangement it is necessary

  • to select a suitable bearing type
  • to determine a suitable bearing size,

but this is not all. Several other aspects have to be considered, such as

  • a suitable form and design of other components of the arrangement
  • appropriate fits and bearing internal clearance or preload
  • holding devices
  • adequate seals
  • the type and quantity of lubricant
  • installation and removal methods, etc.
  • Each individual decision affects the performance, reliability and economy of the bearing arrangement.

    The amount of work entailed depends on whether experience is already available about similar arrangements. When experience is lacking, when extraordinary demands are made or, when the costs of the bearing arrangement and any subsequent outline have to be given special consideration, then much more work is needed including, for example, more accurate calculations and/or testing.

    In the following sections of this general technical introduction, the designer of a bearing arrangement can find the necessary basic information presented in the order in which it is generally required. Obviously it is impossible to include all the information needed to cover every conceivable bearing application. For this reason, in many places, reference is made to the comprehensive SKF application engineering service, which includes technical support about the selection of the right bearing as well as calculations of the complete bearing arrangement. The higher the technical demands placed on a bearing arrangement and the more limited the available experience of using bearings for particular applications, the more advisable it is to make use of this service.

    The information contained in the general technical section usually applies to rolling bearings generally, or at least to a group of bearings. Special information specific to one bearing type only can be found in the text preceding the appropriate individual table section.

    It should be noted that the values provided in the product tables for load and speed ratings as well as for the fatigue load limit are heavily rounded.


    Bearing terminology

    To better understand frequently used bearing terms, definitions are provided below and explained with the help of drawings. A detailed collection of bearing specific terms and definitions can be found in ISO 5593:1997: Rolling bearings - Vocabulary.

    Bearing arrangement

    1. Cylindrical roller bearing
    2. Four-point contact ball bearing
    3. Housing
    4. Shaft
    5. Shaft abutment shoulder
    6. Shaft diameter
    7. Locking plate
    8. Radial shaft seal
    9. Distance ring
    10. Housing bore diameter
    11. Housing bore
    12. Housing cover
    13. Snap ring

    Following terminology is used for the different parts of a rolling bearing.

    Radial bearings

       

    1. Inner ring
    2. Outer ring
    3. Rolling element: ball, cylindrical roller, needle roller, tapered roller, spherical roller
    4. Cage
    5. Capping device
      • Seal made of elastomer, contact (shown in figure) or non-contact
      • Shield made of sheet steel, non-contact
    6. Outer ring outside diameter
    7. Inner ring bore
    8. Inner ring shoulder diameter
    9. Outer ring shoulder diameter
    10. Snap ring groove
    11. Snap ring
    12. Outer ring side face
    13. Seal anchorage groove
    14. Outer ring raceway
    15. Inner ring raceway
    16. Sealing groove
    17. Inner ring side face
    18. Chamfer
    19. Mean bearing diameter
    20. Total bearing width
    21. Guiding flange
    22. Retaining flange
    23. Contact angle
    24. Thrust bearings

    25. 24 Shaft washer
    26. 25 Rolling element and cage assembly
    27. 26 Housing washer
    28. 27 Housing washer with sphered seat surface
    29. 28 Sphered seat washer