Choosing the correct type of slewing bearing for your machine is the single most important decision in bearing selection. The wrong type can fail prematurely under load or be oversized and unnecessarily expensive. This guide from Kavitsu Robotronix explains every major type of slewing bearing by rolling element design and gear configuration, with real-world application examples for each.
Classification by Rolling Element Type
The rolling element is the core engineering element of every slewing bearing. It determines load capacity, speed capability, and overall performance. There are three main families:
1. Single Row Ball Slewing Bearing
Most CommonLight to Medium LoadCost EffectiveThe most widely used type. A single row of steel balls is held in a precision raceway between the inner and outer rings. The balls make four-point contact with the raceways, allowing them to carry axial, radial, and moment loads in all directions with a single row.
Key characteristics: Compact height, good load capacity per unit size, smooth and quiet rotation, good speed capability, lower cost than roller types.
Best applications: Light cranes, solar trackers, medical imaging equipment, stage platforms, light excavators, agricultural machinery, wind turbine pitch bearings (smaller turbines).
Bore diameter range: 100mm to approximately 3,000mm
2. Double Row Ball Slewing Bearing
Higher Moment CapacityMedium to Heavy LoadTwo parallel rows of steel balls provide significantly higher moment (tipping) load capacity compared to a single row design. The increased ball contact area distributes loads more evenly, making this type suitable for machines with large overhanging loads or asymmetric loading.
Key characteristics: Higher axial and moment load capacity than single row, greater height than single row, can handle larger off-centre loads without deformation.
Best applications: Medium cranes, vehicle turntables, stackers/reclaimers, offshore equipment, larger excavators, passenger boarding bridges.
Bore diameter range: 200mm to approximately 3,500mm
3. Three Row Roller Slewing Bearing
Highest Load CapacityHeavy to Very Heavy DutyThe highest capacity slewing bearing design available. Three separate rows of cylindrical rollers — one row for axial load in each direction, and one row for radial load — are arranged in separate raceways. Each row is independently sized for its specific load direction, allowing very high loads to be carried simultaneously.
Key characteristics: Maximum axial, radial, and moment load capacity; largest height profile; highest weight; used where ball bearings cannot cope with the load magnitude; typically requires higher precision machined mounting surfaces.
Best applications: Ship deck cranes, large offshore platform cranes, large bucket wheel excavators, large wind turbine yaw bearings, very large industrial rotary tables, tunnel boring machines.
Bore diameter range: 500mm to 4,500mm+
Classification by Gear Configuration
Any of the three rolling element types above can be manufactured with different gear configurations depending on how the bearing is driven:
External Gear Slewing Bearing
Most AccessibleEasy MaintenanceGear teeth are cut on the outer circumference of the outer ring. The drive pinion meshes with the gear from outside the bearing. This is the most common configuration because the drive pinion is easily accessible for inspection and replacement without removing the bearing.
Best for: Cranes, excavators, general industrial slewing equipment where access for maintenance is straightforward.
Internal Gear Slewing Bearing
Compact DesignProtected GearGear teeth are cut on the inner circumference of the inner ring. The drive pinion sits inside the bearing bore. This design is more compact in outer diameter and the gear is more protected from external contamination.
Best for: Solar trackers, satellite dish positioners, radar systems, applications where compact overall diameter is important and contamination protection is a priority.
Non-Gear (Gearless) Slewing Bearing
No Driven RotationFree RotationNo gear teeth on either ring. The bearing rotates freely and is driven by an external mechanism — typically a hydraulic cylinder, chain drive, or separate gearbox/pinion on a separate ring. Simpler and lower cost when a separate drive mechanism already exists.
Best for: Hydraulic-driven turntables, conveyor systems, applications where the rotation is driven by means other than a gear pinion.
Quick Reference Comparison Table
| Type | Axial Load | Radial Load | Moment Load | Typical Diameter | Cost Level |
|---|---|---|---|---|---|
| Single Row Ball | Medium | Low–Medium | Medium | 100–3,000mm | Lowest |
| Double Row Ball | High | Medium | High | 200–3,500mm | Medium |
| Three Row Roller | Very High | Very High | Very High | 500–4,500mm+ | Highest |
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