Four-point contact ball bearings
Four-point contact ball bearings (fig. 1) are radial single row angular contact ball bearings with raceways that are designed to support axial loads in both directions. For a given axial load, a limited radial load can be supported (→ Design of bearing arrangements, Load ratio). These bearings take up considerably less axial space than double row bearings.
The inner ring is split. This enables a large number of balls to be incorporated in the bearing, giving the bearing its high load carrying capacity. The bearings are separable, i.e. the outer ring with ball and cage assembly can be mounted separately from the two inner ring halves.
Both inner ring halves of SKF Explorer four-point contact ball bearings have a recessed shoulder. This improves oil flow when the bearing is used together with an SKF cylindrical roller bearing (fig. 2). In addition, these recesses can be used to facilitate dismounting.
The standard assortment of SKF four-point contact ball bearings comprises bearings in the QJ 2 and QJ 3 series.
Depending on their design, series and size, SKF four-point contact ball bearings are fitted with one of the cages shown in table 1.
SKF four-point contact ball bearings can be supplied with two locating slots in the outer ring (fig. 3) to prevent it from turning (designation suffix N2). The locating slots are positioned 180° apart. The dimensions and tolerances of the locating slots are in accordance with ISO 20515:2012 and are listed in table 2.