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.
In general, the information for SKF high-precision bearings is valid for SKF-SNFA super-precision bearings. However, it is best to refer to the individual sections "Angular contact ball bearings in the 718 (SEA) series" and "Angular contact thrust ball bearings for screw drives" for additional information.
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.