consist of a radial needle roller bearing and a thrust ball bearing
are supplied without an inner ring
can be combined with an inner ring . where the shaft cannot be hardened and ground (data table, must be ordered separately)
can accommodate axial loads in one direction and, therefore, locate the shaft in one direction only
can be mounted back-to-back , for short shafts and where changes in length due to thermal expansion are relatively minor
For these types of arrangements, SKF recommends preloading the thrust ball bearings with Belleville washers (cup springs). This preload helps to prevent the balls from skidding if one of the thrust bearings becomes unloaded. Preload also improves performance of the thrust ball bearings while reducing noise levels.