What is the most commonly used bearing?

Slewing bearings are large-scale bearings capable of withstanding axial loads, radial loads, and overturning moments simultaneously. They are widely used in heavy machinery requiring rotational functionality, such as cranes, excavators, wind power equipment, and port machinery. Their "commonality" depends on the type of equipment and load requirements. Here are the most prevalent types in industry:

I. Classification by Rolling Element Type 

1. Single-row four-point contact ball slewing bearing

• Structure: The inner or outer ring is integral, with arc-shaped raceways, and the steel balls make four-point contact with the raceways.

• Features:

• Can bear axial loads, radial loads, and overturning moments simultaneously; compact structure and light weight.

• Low rotational speed (usually ≤10r/min), but with moderate load-carrying capacity and low manufacturing cost.

• Applications: Small and medium-sized construction machinery (e.g., small cranes, excavators, truck-mounted cranes), solar tracking systems, light port machinery, etc.

• Advantages: High cost-performance ratio, suitable for medium-load scenarios with limited space, making it the first choice for small and medium-sized equipment.

2. Double-row different-diameter ball slewing bearing

• Structure: Composed of two rows of steel balls with different diameters, with raceways designed to adapt to different load directions.

• Features:

• Higher axial load-carrying capacity than single-row four-point contact ball bearings, capable of withstanding large overturning moments, with moderate radial load-carrying capacity.

• Lighter than roller bearings, with relatively simple installation and maintenance.

• Applications: Medium-sized cranes, tower cranes, concrete pump trucks, aerial work platforms, etc.

• Advantages: Balances load-carrying capacity and structural weight in medium-heavy load scenarios, with wide applications.

3. Single-row crossed roller slewing bearing

• Structure: Rollers are arranged crosswise at 90°, making line contact with the V-shaped raceways of the inner and outer rings, with separators between the rollers.

• Features:

• Strong radial and axial load-carrying capacity, high rigidity, and high precision (capable of achieving high rotational positioning accuracy).

• Low friction coefficient, suitable for scenarios requiring frequent start-stop or positioning.

• Applications: Rotating joints of industrial robots, machine tool turntables, precision radars, medical equipment, and other occasions with high precision requirements.

• Advantages: Irreplaceable in high-precision, medium-load scenarios, serving as the core rotating component of precision equipment.

4. Three-row roller slewing bearing

• Structure: Contains two rows of axial rollers (to bear axial loads and overturning moments) and one row of radial rollers (to bear radial loads), with the three rows of rollers bearing forces independently.

• Features:

• Extremely strong load-carrying capacity (especially for overturning moments), capable of withstanding super-heavy loads, with high reliability.

• Complex structure, heavy weight, and high cost, suitable for low-speed, extreme heavy-load scenarios.

• Applications: Large cranes (e.g., crawler cranes, portal cranes), port shore bridges, large excavators, wind turbine mainframes (above megawatt class), etc.

• Advantages: Serves as the "workhorse" for heavy equipment, performing stably under extreme working conditions.

II. Classification by Structural Form 

1. Internal-tooth or external-tooth slewing bearing

• Gears are machined on the inner or outer ring of the bearing, which can directly mesh with a driving device (e.g., hydraulic motor), simplifying the transmission structure of the equipment.

• Applications: Rotating parts of cranes, slewing mechanisms of excavators, and other equipment requiring power-driven rotation (with an extremely high proportion; most slewing bearings are toothed).

2. Toothless slewing bearing

• No gear structure, requiring external driving devices (e.g., gearboxes, couplings) to achieve rotation.

• Applications: Scenarios with special requirements for rotational driving methods (e.g., precision turntables, some wind power equipment), with a relatively low proportion.

Summary: The Most Common Core Types

• Small and medium-sized equipment: Single-row four-point contact ball slewing bearing 

• Medium and large equipment: Double-row different-diameter ball slewing bearing 

• Heavy/extra-heavy equipment: Three-row roller slewing bearing 

• High-precision equipment: Single-row crossed roller slewing bearing 

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