RKB double row angular contact ball bearings are equivalent to two single row paired angular contact ball bearings in the arrangement back-to-back or face-to-face. So they can accept radial loads together with axial loads acting in both directions. The width is narrower than the two equivalent single row bearings in pair.
The large double row angular contact ball bearings of RKB production range include bearings specially designed for rolling mills (bearing designation series 305 followed by three numbers).
The standardized items of the series ISO 32 and 33 have the filling slot and are non-separable, thus single direction axial loads should be applied.
The special bearings with drawing number of series 305 can have either split two-part inner ring or split two-part outer ring. They are non-separable and usually are mounted with radial play in the housing. In the bearings with split two-part inner ring the load lines refer to the back-to-back arrangement. The load lines of the bearings with split two-part outer ring are in the face-to-face arrangement.
The main dimensions of bearing series 32 and 33 are as per ISO 15 specifications. The dimensions of bearing series 305 do not follow any standards, but are internationally accepted and recognized in the rolling mill applications. The manufacturing tolerances conform to ISO 492 for normal class specification, but running accuracy grade is in accordance with P6 at least. These bearings are generally produced with a uniform axial internal clearance, but special values suitable for specific applications can be supplied on request.
The double row angular contact ball bearings in RKB production program are normally filled with two machined brass cage (one for each ball row).
RKB single angular contact ball bearings are designed to accommodate combined loads acting in radial and axial direction. They can take axial loads in one direction only. When radially loaded, in the bearing occurs an axially acting load which has to be compensated. For this reason one bearing or paired bearings are mounted on each shaft end. These bearings are not separable and their use at relatively high speed is allowed. Manufactured in various constructive versions, they can be with different contact angles, depending on the application (suffix AC, A and B).
RKB produces two types of single row angular contact ball bearings: those of normal design and those intended for paired mounting (used respectively for tandem arrangement, DB and DF arrangements when axial loads have to be taken in both directions).
In the case of single row angular contact ball bearings the efforts between rings and rolling elements are transmitted at an angle to a plane perpendicular to the bearing axis. The value of this angle depends on the magnitude of the raceway radius, ball diameter and radial clearance in the bearing when the curvature centers of the raceway are in the same plane.
The main dimensions are in accordance with ISO/R 15. The values for the tolerance of the normal, P6 and P5 classes conform to ISO 492. Internal axial clearance or preload is obtained only when the bearings are mounted in the assembly and depends on the location of the second bearing which assures the shaft axial guiding.
RKB single angular contact ball bearings are fitted with a cage type depending on series and size: pressed steel sheet cage, machined brass cage guided on balls or on the inner ring and machined steel cage.
Large size paired 718 and 719 series bearings in DF and DB configuration for power transmission equipment are included in RKB production program.
FOUR-POINT ANGULAR CONTACT BALL BEARINGS
RKB four-point angular contact ball bearings are single row bearings where the raceway is designed to accommodate significant axial loads in both directions. Generally they have contact angle of either 35° or 45°. They need less axial space than double row or paired angular contact ball bearings. The four-point contact ball bearings have a split two-part inner (bearing designation QJ) or outer (bearing designation Q) ring, allowing a large number of balls to be incorporated, thus providing a high load carrying capacity. The bearings are of separable design of the parts.
To prevent rotation of the outer ring (when split inner ring) all the bearings with outside diameter over 160 mm are provided with locating slots (suffix N).
The main boundary dimensions are in accordance to ISO 15. The tolerances have values conform to ISO 492 and the normal class is for RKB standard production. The fitted cage is machined brass centered on outer ring for the standard common type QJ with split inner ring. RKB produces these bearings with normal axial internal clearance measured before mounting under zero measuring loads, but most sizes can also be supplied with greater or smaller clearance to special order.