Slewing Bearing


Slewing bearings, as they are more commonly described, are used inside a machine or system when it is necessary to guide the rotary motion of one part in relation to another. A slewing bearing must guarantee support for the required loads with maximum rigidity within the precision range appropriate to the application, comply with operating parameters and offer a service lifetime compatible with the lifetime of the machinery to which it is fitted.


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Three Ways to Drive a Slewing Ring Bearing

Designed similar to ball bearings, slewing ring bearings are used in rotating and turntable applications. The success of the slew ring bearings correlates to how the system is driven.

Slewing bearings are comprised of an inner and an outer ring, one of which incorporates a gear. Three ways to drive this type of bearing include external gear, external belt, and drive-plate coupling.

Internal & External gear

Most slewing ring manufacturers offer a geared option. The mating gear for any slew ring should be made of a softer material than the actual gear itself. 

External belt 

Belts come in various widths and the ability to withstand pounds of tension.

Drive-plate coupling 

A drive-plate coupling connects to a motor assembled directly to the slewing ring.

Slewing Bearings

Application Slewing Ring Bearings With Internal Gear

  • A slewing ring bearing with internal gear is used in various rotating machines with or without eccentric loads.


  • The Torriani internal geared slewing ring is widely used in demolition and sorting grabs, cranes packaging industry, transport industry and agricultural machines.

Structure Of A Slewing Bearing

These bearings consist of two concentric rings, one of which incorporates a gear. These bearings are able to bear axial and radial loads as well as overturning torque.

They can be driven by an external gear, external belt, or drive-plate coupling. They can also be driven by an internal gear on one of the ring’s outer sides.





Before Installing The Bearing

– Check the mounting surface of the main piece of machinery

– Ensure all supporting parts have sufficient strength

– The connecting surface should be machined

– The surface also must be smooth without burrs

During Installation

– Test radial positioning

– Tighten all mounting bolts (When tightening the bolts, there should be sufficient pre-tightening force, and the pre-tightening force should be 70% of the yield limit of the bolt material or to its specific torques limit set by its specific application). 

– Check bearing rotation

– Any paint that is damaged during installation must be repaired. Failure in doing so could result in corrosion issues.

After Installation

– Ensure the pre-tightening torque of the mounting bolts meets the requirements

– Ensure the proper amount and type of grease/lubricant is used 

– Slew bearings require the raceway to be lubricated

More About  Slewing Bearing


The Maintenance Of A Slewing Bearing

Large-diameter bearings – especially slewing ring bearings – handle complex loads in heavy-duty rotating equipment such as cranes, earth excavators and tunnel boring machines. They must handle combinations of thrust, radial and tilting moment loading.


The Function Of A Slewing Bearing

A slewing bearing or rotary bearing is an important mechanical component used to enable rotation between different parts. They are used in large-scale slewing devices such as lifting and transportation machinery, mining machines, construction equipment, port machinery and wind turbines.

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