Bearing Net

Another great product from NBC!

Double Row Ball Slew Rings

Double row ball slew rings are ideal in applications where a high moment load is to be supported, a degree of rigidity is required in the bearing system, or there are high radial loads. 

They find application in a wide variety of applications such as scrap handling grab cranes, portal or jib cranes or deck handling apparatus.

Special wide gear face designs find application in high-torque winches where the gear forces rather than bearing loads dictate the overall design.

All QCB® double row bearings are manufactured in 42CrMo4 steel for superior gear strength and toughness in arduous operating conditions. 

The standard stock units are listed below. However we have drawings on file to 4500mm diameter (internal and external gear)

Matching pinions and either electric or hydraulic gearboxes can be specified and offered for a complete solution.


Double row bearings datasheet HERE

INDIVIDUAL PDF FILES (under review - please contact NBC Technical)

Ungeared  SUN 504.2     SUN 610.2     SUN 979.2

External     SEG 504.2     SEG 610.2     SEG 816.2     SEG 979.2
                   SEG 1289.2     SEG 1380.2

Internal       SIG 700.2     SIG 976.2     SIG 982.2     SIG 1072.2
                   SIG 1470.2     SIG 1750.2


Available on request

Dimensions - External gear


Dimensions - Internal Gear


All QCB® double row ball bearings are made in 42CrMo4 for superior gear strength. Other manufacturers may vary.

Grease points

Will vary and are noted on the specific bearing drawings.

QCB® bearings are assembled using a standard lithium EP2 grease but should be greased during installation

Load and bolt limit curves

Bearings should operate within the prescribed triangular area at all times. If a combination radial and axial load act on the bearing this should be replaced by a single equivalent load to enable graphical analysis and selection. 

The bolt limit curve is based on the use of Grade 10.9 bolts.

If the load is suspended, or the axis of rotation is not vertical refer the application details to NBC Technical for assistance.

External gear

Internal Gear

Interchange information

QCB® double row slewing rings are usually interchangeable with those from other manufacturers. However as so many simple variations exist please check with NBC Technical.

In the quest for continual product improvement these specifications may change without notice.

Need help?

For immediate and expert advice call us on 01952 222300 or e-mail

Whilst every effort has been made to ensure the accuracy of the information on this website, if you spot a mistake please inform the Thanks!