Slewing Bearings

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Slewing Bearing for Shield Tunneling Machine

What Is a Slewing Bearing for Shield Tunneling Machine?

A slewing bearing for a shield tunneling machine (TBM) is a large-diameter, heavy-duty rotational component that serves as the critical connection between the cutterhead and the main frame of the tunnel boring machine. Often referred to as the “heart” or “spinal joint” of the TBM, this bearing enables the massive cutterhead to rotate smoothly while supporting enormous axial, radial, and tilting loads generated during excavation.

Typical slewing bearings used in TBMs range from 2 meters to over 10 meters in diameter, making them among the largest rolling bearings ever manufactured. Without this component, the cutterhead could neither rotate precisely nor transmit the immense forces required to crush rock and cut through soil. The bearing also houses an integral gear ring that engages with pinion gears driven by hydraulic or electric motors, forming the core of the TBM’s drive system.

Design Features of a Slewing Bearing for Shield Tunneling Machine

The design of a slewing bearing for shield tunneling machines is fundamentally different from conventional bearings due to the extreme operating environment. Below are the key design features:

Ultra-High Load Capacity – These bearings are engineered to simultaneously handle axial thrust from the forward push of the cutterhead, radial forces from uneven ground conditions, and tilting moments from off-center cutting loads.

Compact Cross-Section – Despite their enormous diameter, slewing bearings maintain a relatively slim cross-section, allowing them to fit within the limited space of the TBM’s front chamber.

Raceway Geometry – Three common designs are used: three-row roller raceways with separate paths for axial and radial loads, double-row tapered roller raceways for compact high-capacity applications, and crossed roller raceways for high rigidity under moderate loads.

Integral Gear Ring – The bearing includes either an internal or external gear ring that engages with pinion gears driven by hydraulic or electric motors.

Heavy-Duty Sealing Systems – Multi-lip seals protect against mud, sand, water, and fine abrasive particles that would otherwise destroy the raceways.

Material Selection – Heat-treated alloy steel (typically 42CrMo4 or equivalent) provides the necessary hardness, toughness, and fatigue resistance.

Main Types of a Slewing Bearing for Shield Tunneling Machine

Slewing bearings for shield tunneling machines are classified based on rolling element arrangement, gear position, and TBM type. The table below summarizes the main categories:

Type by Rolling Element	Load Capacity	Typical TBM Size	Key Advantage
Three-row roller bearing	Highest	Large (6m – 10m+)	Independent load paths, best durability
Double-row tapered roller bearing	High	Medium (4m – 8m)	Compact, good moment resistance
Crossed roller bearing	Moderate	Small (2m – 4m)	High rigidity, space-saving

By Gear Position: Internal gear type (teeth on inner ring) is most common for EPB shields, while external gear type (teeth on outer ring) is used in some slurry shields.

By TBM Type: Earth Pressure Balance shields typically use three-row roller bearings with internal gears. Slurry shield TBMs often employ double-row tapered roller bearings with enhanced sealing. Hard rock gripper TBMs require bearings with exceptional shock load resistance.

How Does a Slewing Bearing Work in Shield Tunneling Machine?

Understanding the working principle of a slewing bearing in a shield tunneling machine requires examining the entire drive train. Here is a step-by-step explanation:

Step 1: Power Generation – Hydraulic motors or electric motors mounted around the bearing’s circumference generate rotational power.

Step 2: Gear Engagement – Each motor drives a small pinion gear. These pinions engage directly with the gear ring machined into the slewing bearing (either internal or external teeth).

Step 3: Relative Rotation – One ring of the slewing bearing (typically the inner ring) is bolted to the cutterhead. The other ring (outer ring) is fixed to the TBM’s main shield body. When the pinions rotate, they drive the bearing ring, causing the cutterhead to turn.

Step 4: Load Transmission – As the cutterhead rotates and advances into the ground, axial loads (forward thrust) are transferred through the bearing’s axial raceways, radial loads (off-center forces) are absorbed by radial raceways, and tilting moments (uneven cutting resistance) are distributed across multiple rolling elements.

Step 5: Friction Minimization – The rolling elements (rollers) roll between the raceways, converting sliding friction into low rolling friction. This allows smooth rotation even under hundreds of tons of load.

Step 6: Continuous Lubrication – An automatic grease lubrication system continuously supplies fresh grease to the raceways and gear teeth, flushing out contaminants and reducing wear.

Key Advantages of a High-Quality Slewing Bearing for Shield Tunneling Machine

Investing in a premium slewing bearing for a shield tunneling machine delivers multiple operational and financial benefits:

Advantage	Benefit
Smooth, low-friction rotation	Reduced energy consumption, less heat generation
High reliability (10,000+ hours)	Fewer unplanned stops, predictable project timelines
Excellent shock load resistance	Survives encounters with boulders and hard rock layers
Compact force transmission	Shorter TBM length, easier handling in tight curves
Improved cutterhead positioning	Better steering accuracy, reduced over-excavation
Integrated monitoring capability	Real-time health data, predictive maintenance
Effective sealing systems	Longer raceway life in abrasive environments

Quantifiable Impact: A high-quality slewing bearing can reduce TBM downtime by up to 40% and extend the machine’s service life by 3–5 years compared to standard alternatives.

Common Challenges & Maintenance of a Slewing Bearing for Shield Tunneling Machine

Despite robust designs, slewing bearings for shield tunneling machines face severe challenges that require diligent maintenance.

Common Challenges

Abrasive grit ingress leads to raceway pitting and premature wear
High-pressure water intrusion causes corrosion and lubricant washout
Seal failure results in catastrophic contamination and potential bearing seizure
Inadequate grease supply causes metal-to-metal contact and overheating
Shock loads from boulders can crack rolling elements or cause brinelling of raceways
Difficult inspection location leads to late fault detection and unexpected failures

Maintenance Best Practices

Automatic Lubrication Systems – Programmed to deliver precise grease quantities at regular intervals. Grease consumption for a large TBM main bearing can reach 50–100 kg per day.

Regular Grease Analysis – Testing used grease for metal particles, water content, and consistency changes can reveal internal wear before failure occurs.

Vibration Monitoring – Accelerometers mounted near the bearing detect changes in vibration signatures that indicate raceway damage or rolling element issues.

Temperature Monitoring – Sudden temperature rises often signal lubrication failure or excessive friction.

Inspection Intervals – Visual and borescope inspections during scheduled TBM stops, typically every 500–1,000 hours of operation.

What Happens If Maintenance Fails?

Bearing failure in a TBM is a catastrophic event. The cutterhead may seize completely, requiring surface excavation from above for shallow tunnels, construction of bypass tunnels, or abandonment of the TBM in extreme cases. Repair costs often exceed $5–10 million, with project delays of 6–12 months.

Future Trends for the Slewing Bearing for Shield Tunneling Machine

The industry is evolving rapidly, with several emerging trends shaping the next generation of slewing bearings for shield tunneling machines.

Larger Bearings for Super TBMs – As cities push for larger diameter tunnels (15m+ for road and rail), slewing bearings must scale accordingly. Manufacturers are developing bearings up to 12–14 meters in diameter with new steel grades and heat treatment processes.

Smart Bearings with Embedded Sensors – Future slewing bearings will integrate fiber-optic and piezoelectric sensors directly into the raceways and rings, providing real-time data on raceway stress distribution, lubricant film thickness, early crack detection, and rolling element temperature.

Advanced Surface Coatings – New coatings such as diamond-like carbon and ceramic composites dramatically reduce friction and resist abrasion. Some coatings can extend bearing life by 3–5 times in sandy or muddy ground conditions.

Digital Twin Simulation – Each slewing bearing can be modeled as a digital twin that simulates remaining useful life based on actual operating data (loads, speeds, temperatures). This enables true predictive maintenance rather than scheduled replacement.

Sustainable Lubricants – Biodegradable, non-toxic greases are being developed to reduce environmental impact when leaks occur. These new lubricants maintain performance at high pressures and temperatures while being safe for groundwater.

Modular Bearing Designs – Some manufacturers are exploring segmented slewing bearings that can be replaced piece-by-piece without full TBM disassembly – a potential game-changer for tunnel repairs.

LDB: A Professional Slewing Bearing Supplier for Multiple Industries

LDB Slewing Bearing is an enterprise specializing in the design, development, manufacture, and sales of precision slewing bearings (slewing rings) and precision slewing drives. As a professional supplier, we provide high-performance small and large slewing rings suitable for various industries including construction machinery, wind power, medical equipment, robotics, and tunnel engineering.

Unlike other providers of slewing bearings, LDB can offer fully tailored slewing bearing solutions with integrated advanced monitoring, lubrication, and sealing systems for higher reliability and longer service life. Whether your application is a shield tunneling machine or an industrial crane, we deliver customized engineering to meet specific load, gear, and environmental requirements.

Our wide range of expert slewing bearing services also help cut costs and optimize performance, while our global presence allows slewing bearing solutions and services to be delivered quickly around the world. Choose LDB – your reliable partner for high-performance slewing bearings across any industry.

FAQ of Slewing Bearings for Shield Tunneling Machine

Q1: How long does a slewing bearing last in a shield tunneling machine?

A: Typically 8,000–15,000 operating hours, depending on ground conditions, maintenance quality, and bearing design. In favorable conditions (soft ground, proper lubrication, effective sealing), some bearings exceed 20,000 hours. Hard rock applications with poor maintenance may see failure before 5,000 hours.

Q2: Can the main slewing bearing be replaced after installation?

A: In most large TBMs, replacement is extremely difficult and rarely performed on-site. The bearing is embedded deep within the TBM’s structure, often requiring complete disassembly of the cutterhead and front chamber. Some modern designs allow bearing replacement through the cutterhead center, but this remains a complex, expensive operation. This is why initial bearing quality and customization are critical.

Q3: What happens if the slewing bearing fails during tunneling?

A: Bearing failure is catastrophic. The cutterhead may seize completely, stopping all excavation. Depending on tunnel depth and ground conditions, solutions range from chemical grouting and replacement via access shaft, to building a bypass tunnel around the TBM, or abandoning the TBM and boring a new tunnel from the other side. Costs typically exceed $10 million with delays of 6–18 months.

Q4: What is the difference between three-row roller and crossed roller slewing bearings?

A: Three-row roller bearings handle axial and radial loads independently using separate raceways, offering the highest load capacity and making them ideal for large TBMs (6m–10m+ diameter). Crossed roller bearings use a single raceway with rollers arranged perpendicularly, providing high rigidity in a lower profile, but they are suited for moderate loads only and typically used in small to medium TBMs (2m–5m diameter). Three-row designs are taller and more expensive, while crossed roller bearings are more compact and cost-effective for smaller machines.

Q5: Why should I choose a custom slewing bearing rather than an off-the-shelf one for my TBM?

A: Every TBM has unique requirements: cutterhead diameter (2m–10m+), expected loads (variable by geology), mounting interface, gear specifications (module, number of teeth), environmental sealing needs, and monitoring system integration. Off-the-shelf bearings rarely match these parameters precisely. A custom bearing ensures perfect fit with existing TBM structure, optimized gear design for your drive motors, appropriate seal selection for your ground conditions, integrated sensor ports for condition monitoring, and certification to your project’s safety standards. The upfront cost of custom is quickly recovered through reduced failures and longer service life.

Delivery of CAT Excavator Slewing Bearing to South America

May 15, 2026/in LDB Company News /by LDB Bearing

In June 2023, our company successfully delivered a Four-Point Contact Ball Slewing Bearing for a CAT excavator to a client in South America. The customer required a reliable slewing ring to support heavy-duty applications such as mining and earthmoving. We supplied a four-point contact ball slewing bearing, which features a single raceway design with four contact points per ball, allowing it to simultaneously handle axial loads, radial loads, and tilting moments.

This bearing type offers a compact cross-section, high load efficiency, and smooth rotation, making it an ideal match for CAT excavators. After rigorous factory testing—including dimensional accuracy, hardness, and gear inspection—we prepared the bearing for shipment. In June 2023, we shipped the unit via a dedicated South America logistics route, applying anti-corrosion treatment and reinforced packaging to ensure safe delivery.

Upon arrival, the client confirmed successful installation and reported excellent performance. The four-point contact ball slewing bearing delivered stable slewing, low vibration, and reduced noise during daily excavator operations. This case once again demonstrates our ability to provide application-specific slewing bearings for leading brands like CAT, with on-time delivery to customers across South America.

What Is a Four-Point Contact Ball Slewing Bearing?

A Four-Point Contact Ball Slewing Bearing is a large-scale precision bearing that supports heavy rotating structures. It mainly consists of an inner ring, an outer ring, a single row of steel balls, a cage (or spacer), and a sealing device. Both the inner and outer rings come in either integral or split structures. The integral ring offers strong rigidity, while the split design allows for easy adjustment. For split structures, LDB uses bolts to connect the two split rings before the product leaves the factory.

Most four-point contact ball slewing bearings include a cage or spacer. However, we use a full-ball structure only when the application demands a relatively large load capacity. The full-ball design provides higher bearing capacity but creates greater frictional resistance, which can easily cause scratches on the surface of the steel balls. The basic structure of a four-point contact ball slewing bearing may include no gear, external gear, or internal gear teeth, delivering high static load capacity for demanding applications.

How Does a Four-Point Contact Ball Slewing Bearing Work?

The working principle of a four-point contact ball slewing bearing relies on a single row of steel balls running in arc-shaped raceways. Each steel ball makes contact with the raceway at four points—two on the inner ring and two on the outer ring. This unique geometry allows the bearing to accept axial loads from either direction, radial loads, and tilting moments simultaneously.

The drive mechanism—usually a pinion gear—engages the internal or external gear teeth on the bearing ring. As the pinion rotates, it drives the bearing ring to turn, allowing the attached structure to rotate smoothly with minimal friction.

Key Features of Four-Point Contact Ball Slewing Bearings

Four-point contact ball slewing bearings from LDB offer several distinctive features that make them suitable for a wide range of applications:

Compact structure: The single-row design combines two seat rings into a lightweight, space-saving package.
Four-point contact geometry: Steel balls contact arc raceways at four points, enabling the bearing to bear axial force, radial force, and tilting moment at the same time.
Dual ring structure options: Choose between integral rings for maximum rigidity or split rings for easier adjustment during installation.
Flexible gear configurations: Available without gear, with internal gear, or with external gear teeth.
Wide size range: Outer diameters from 200mm to 10,000mm, inner diameters from 100mm to 8,000mm, ball diameters from 30mm to 75mm, and rated loads from 129kN to 3,410kN.
High-quality materials: LDB uses 42CrMo and 50Mn steel for superior strength and durability.
Effective sealing: Nitrile rubber seals protect the bearing from contaminants and retain lubricant.
Precision heat treatment: Normalizing hardness reaches 187HB-241HB, quenched and tempered hardness reaches 229HB-269HB, and raceway quenching hardness achieves HRC 55-62.
Short delivery time: LDB offers delivery within 10 to 30 days.
12-month warranty: Every bearing comes with a full one-year warranty against manufacturing defects.

Main Types of Four-Point Contact Ball Slewing Bearings

Based on gear configuration, four-point contact ball slewing bearings fall into three main types:

1. Non-Gear Type (No Gear)
This type has no gear teeth machined into the inner or outer ring. It suits applications where an external drive mechanism provides rotation independently of the bearing.

2. External Gear Type
The outer ring features gear teeth on its external surface. A pinion gear engages these teeth from outside the bearing. This configuration works well when the drive motor sits outside the rotating structure.

3. Internal Gear Type
The inner ring carries gear teeth on its internal surface. The pinion gear mounts inside the bearing ring. This design offers a cleaner layout and better protection for the gear system.

Each type allows LDB to match the bearing precisely to your mechanical design. We also offer both integral ring and split ring structures for each gear configuration.

Core Advantages of Four-Point Contact Ball Slewing Bearings

Four-point contact ball slewing bearings provide significant advantages over other bearing types:

Single bearing replaces multiple bearings
One four-point contact ball slewing bearing handles axial loads, radial loads, and tilting moments simultaneously. You do not need separate thrust bearings and radial bearings in your assembly.

Compact and lightweight design
The single-row structure occupies minimal space and adds little weight to your equipment. This helps you design more compact machinery.

High static load capacity
The four-point contact geometry distributes loads efficiently, allowing the bearing to support very high static loads without permanent deformation.

Bi-directional axial load capability
Unlike many bearings that handle axial load in only one direction, the four-point contact design accepts axial forces from either direction equally well.

Smooth rotation with low torque
Precision-ground raceways and high-quality steel balls deliver quiet, low-friction rotation, reducing power consumption and wear.

Long service life
With proper lubrication and maintenance, LDB’s four-point contact ball slewing bearings provide years of reliable continuous operation.

Customizable sealing and cage design
Based on your working environment, LDB can optimize the sealing structure and internal fixator to match your specific conditions.

Common Applications of Four-Point Contact Ball Slewing Bearings

Four-point contact ball slewing bearings from LDB serve a wide variety of industries and equipment:

Construction machinery
These bearings perform excellently in rotary conveyors, welding robots, manipulators, small and medium cranes, and excavators. The ability to handle combined loads makes them ideal for equipment that rotates under heavy weight.

Tower garage parking systems
Automated parking systems rely on four-point contact ball slewing bearings to rotate car-carrying platforms smoothly and accurately.

Crane and hoist equipment
Mobile cranes, tower cranes, and shipboard cranes use these bearings for their slewing mechanisms.

Excavators and earthmoving machines
Both medium and small excavators benefit from the compact size and high load capacity of four-point contact bearings.

Wind turbines
Some yaw and pitch systems in wind turbines use four-point contact slewing bearings for their ability to handle combined loads in outdoor environments.

Medical equipment
Large medical imaging devices and robotic surgery systems use these bearings for precise rotational positioning.

How to Select the Right Four-Point Contact Ball Slewing Bearing?

Selecting the correct four-point contact ball slewing bearing requires careful consideration of several factors:

Load requirements
Calculate the maximum axial load, radial load, and tilting moment your application will generate. LDB’s rated load range of 129kN to 3,410kN covers most medium to heavy-duty applications. Provide your load data to our engineers for accurate sizing.

Gear configuration
Decide whether you need no gear, internal gear, or external gear teeth based on your drive system layout. Internal gears suit designs where the motor mounts inside the bearing ring. External gears work when the motor sits outside.

Ring structure
Choose between integral ring for maximum rigidity or split ring for easier adjustment during installation. LDB pre-assembles split rings with bolts before delivery.

Size dimensions
Specify your required inner diameter (100mm to 8,000mm) and outer diameter (200mm to 10,000mm). Ball diameter (30mm to 75mm) affects load capacity and rotational smoothness.

Sealing requirements
Standard nitrile rubber seals suit most environments. For harsh conditions, LDB can design special sealing structures to protect against dust, moisture, and contaminants.

Heat treatment specifications
Verify that hardness levels meet your application needs. LDB provides normalizing hardness of 187HB-241HB, quenched and tempered hardness of 229HB-269HB, and raceway quenching hardness of HRC 55-62.

Cage or full-ball design
Use a cage design for most applications. Choose full-ball structure only when you need maximum load capacity and can accept higher friction.

Delivery time
LDB offers standard delivery within 10 to 30 days. For urgent requirements, please contact us to discuss expedited options.

Non-standard models
If your application requires a non-standard model, LDB can design and manufacture according to your specific requirements. We have commonly used standard models in stock, and our engineering team can develop custom solutions for any project.

LDB: Custom Four-Point Contact Ball Slewing Bearings Manufacturer

LDB specializes in the design, production, and supply of high-quality four-point contact ball slewing bearings. We serve customers across Asia, South America, Europe, and the Middle East, providing reliable components for construction machinery, parking systems, cranes, excavators, and more.

Our manufacturing capabilities
We produce four-point contact ball slewing bearings with outer diameters from 200mm to 10,000mm and inner diameters from 100mm to 8,000mm. Ball diameters range from 30mm to 75mm, and rated loads span from 129kN to 3,410kN. Our materials include 42CrMo and 50Mn steel, both known for their excellent strength, toughness, and wear resistance.

Quality assurance
Every bearing undergoes rigorous quality testing before leaving our factory. We inspect dimensional accuracy, hardness, gear teeth, and raceway surface quality. Our heat treatment process includes normalizing, quenching and tempering, and raceway induction hardening to achieve the required hardness levels.

Customization options
LDB provides a complete set of slewing bearings without gears, with external gears, with internal gears, or individual ring gears according to your requirements. For split ring designs, we connect the two split rings with bolts before shipment to simplify your installation. We can also optimize the sealing structure and internal fixator based on your working environment.

Packaging and delivery
We package each bearing using metal brackets or export standard fumigation-free wooden boxes. This ensures safe transportation to any global destination. Our standard delivery time is 10 to 30 days.

Technical support
Our engineering team can recommend the exact bearing model for your design or develop a fully custom solution. Whether you need a standard model or a non-standard design, we work closely with you to meet your specifications.

Warranty
All LDB four-point contact ball slewing bearings come with a 12-month warranty against manufacturing defects. We stand behind the quality and reliability of every product we ship.

Contact LDB today to discuss your four-point contact ball slewing bearing requirements. Provide your load data, size specifications, gear configuration, and any special requirements. We will respond with a competitive quote, technical recommendations, and a reliable delivery schedule.

Delivery of Volvo Excavator Slewing Bearing to South America

May 14, 2026/in LDB Company News /by LDB Bearing

In July 2022, our company successfully delivered a Four-Point Contact Ball Slewing Bearing for a Volvo excavator to a client in South America. The customer required a high-performance slewing ring to support demanding applications such as earthmoving, construction, and infrastructure projects. We supplied a four-point contact ball slewing bearing, which features a single raceway design with four contact points per ball, allowing it to handle axial loads, radial loads, and tilting moments simultaneously.

This bearing type offers a compact cross-section, high load efficiency, and smooth rotation, making it an ideal match for Volvo excavators. After rigorous factory testing—including dimensional accuracy, hardness, gear inspection, and raceway quenching hardness verification (HRC 55-62)—we prepared the bearing for shipment. In July 2022, we shipped the unit via a dedicated South America logistics route, applying anti-corrosion treatment and reinforced export-standard fumigation-free wooden box packaging to ensure safe delivery.

Upon arrival, the client confirmed successful installation and reported excellent performance. The four-point contact ball slewing bearing delivered stable slewing, low vibration, and reduced noise during daily excavator operations. This case once again demonstrates our ability to provide application-specific slewing bearings for leading brands like Volvo, with on-time delivery to customers across South America. LDB offers a 12-month warranty, delivery within 10-30 days, and full customization including internal gear, external gear, or non-gear options.

What Are Four-Point Contact Ball Slewing Bearings?

Four-point contact ball slewing bearings are large-scale precision bearings that support heavy rotating structures in demanding machinery. A four-point contact ball slewing bearing mainly consists of an inner ring, an outer ring, a single row of steel balls, a cage (or spacer), and a sealing device. Both the inner and outer rings come in either integral or split structures. The integral ring offers strong rigidity, while the split design allows for easy adjustment. For split structures, LDB uses bolts to connect the two split rings before the product leaves the factory.

Most four-point contact ball slewing bearings include a cage or spacer. However, manufacturers use a full-ball structure only when the application demands a relatively large load capacity. The full-ball design provides higher bearing capacity but creates greater frictional resistance. This friction can easily cause scratches on the surface layer of the steel balls. The basic structure of a four-point contact ball slewing bearing may include no gear, external gear, or internal gear teeth, delivering high static load capacity for demanding applications.

How Does a Four-Point Contact Ball Slewing Bearing Work?

When an external load applies to the bearing, the steel balls transfer forces across the four contact points. The distribution of load changes depending on the direction of the force. For vertical axial loads, all four contact points share the load. For combined loads, some contact points carry more force while others unload. This dynamic load distribution gives the bearing its ability to handle complex loading conditions in a single raceway. The drive mechanism—usually a pinion gear—engages the internal or external gear teeth on the bearing ring. As the pinion rotates, it drives the bearing ring to turn, allowing the attached structure to rotate smoothly with minimal friction.

Structural Features of Four-Point Contact Ball Slewing Bearings

Four-point contact ball slewing bearings possess several distinctive structural features that make them suitable for a wide range of applications. The single-row four-point contact ball slewing bearing consists of two seat rings, offering a compact structure and light weight. The four-point contact between the steel ball and the arc raceway enables the bearing to bear axial force, radial force, and tilting moment at the same time.

LDB manufactures these bearings with outer diameters ranging from 300mm to 10,000mm and ball diameters from 30mm to 75mm. Rated loads span from 129kN to 3,410kN, covering most medium to heavy-duty applications. The materials used include 42CrMo and 50Mn steel, both known for their excellent strength and wear resistance. The seal type is nitrile rubber, which provides effective protection against contaminants while retaining lubricant. The rolling body is a steel ball, and the heat treatment process delivers normalizing hardness of 187HB-241HB, quenched and tempered hardness of 229HB-269HB, and raceway quenching hardness of HRC 55-62. LDB offers a 12-month warranty on all products, with delivery times of 10 to 30 days.

Main Configuration Types of Four-Point Contact Ball Slewing Bearings

Based on gear configuration, four-point contact ball slewing bearings fall into three main types:

1. Non-Gear Type (No Tooth)
This type has no gear teeth machined into the inner or outer ring. It suits applications where an external drive mechanism provides rotation independently of the bearing.

2. External Gear Type (External Tooth)
The outer ring features gear teeth on its external surface. A pinion gear engages these teeth from outside the bearing. This configuration works well when the drive motor sits outside the rotating structure.

3. Internal Gear Type (Internal Tooth)
The inner ring carries gear teeth on its internal surface. The pinion gear mounts inside the bearing ring. This design offers a cleaner layout and better protection for the gear system.

Each type allows LDB to match the bearing precisely to your mechanical design. We also offer both integral ring and split ring structures for each gear configuration. The features include four-point contact with internal tooth, external tooth, or no tooth options.

Core Advantages of Four-Point Contact Ball Slewing Bearings

Four-point contact ball slewing bearings provide significant advantages over other bearing types:

Compact and lightweight design
The single-row structure consists of two seat rings, occupying minimal space and adding little weight to your equipment. This helps you design more compact machinery.

High static load capacity
The four-point contact geometry distributes loads efficiently, allowing the bearing to support very high static loads without permanent deformation.

Bi-directional axial load capability
Unlike many bearings that handle axial load in only one direction, the four-point contact design accepts axial forces from either direction equally well.

Smooth rotation with low torque
Precision-ground raceways and high-quality steel balls deliver quiet, low-friction rotation, reducing power consumption and wear.

Long service life
This series of slewing ring suits main engines that require large axial load capacity, high overturning moment resistance, long service life, and continuous operation.

Customizable sealing and cage design
According to the requirements of the supporting working environment, LDB can optimize the design of the sealing structure and the internal fixator.

Common Applications of Four-Point Contact Ball Slewing Bearings

Four-point contact ball slewing bearings from LDB serve a wide variety of industries and equipment:

Tower garage parking systems
Automated parking systems rely on four-point contact ball slewing bearings to rotate car-carrying platforms smoothly and accurately.

Crane and hoist equipment
Mobile cranes, tower cranes, and shipboard cranes use these bearings for their slewing mechanisms.

Excavators and earthmoving machines
Both medium and small excavators benefit from the compact size and high load capacity of four-point contact bearings.

Wind turbines
Some yaw and pitch systems in wind turbines use four-point contact slewing bearings for their ability to handle combined loads in outdoor environments.

Medical equipment
Large medical imaging devices and robotic surgery systems use these bearings for precise rotational positioning.

Key Factors When Choosing a Four-Point Contact Ball Slewing Bearing

Selecting the correct four-point contact ball slewing bearing requires careful consideration of several factors:

Ring structure
Choose between integral ring for maximum rigidity or split ring for easier adjustment during installation. LDB pre-assembles split rings with bolts before delivery.

Size dimensions
Specify your required inner diameter (100mm to 8,000mm) and outer diameter (200mm to 10,000mm). Ball diameter (30mm to 75mm) affects load capacity and rotational smoothness.

Sealing requirements
Standard nitrile rubber seals suit most environments. For harsh conditions, LDB can design special sealing structures to protect against dust, moisture, and contaminants.

Cage or full-ball design
Use a cage design for most applications. Choose full-ball structure only when you need maximum load capacity and can accept higher friction.

Delivery time
LDB offers standard delivery within 10 to 30 days. For urgent requirements, please contact us to discuss expedited options.

Non-standard models
LDB has commonly used standard models available. For non-standard models, we can design and manufacture according to customer requirements.

LDB: Custom Four-Point Contact Ball Slewing Bearings Manufacturer

LDB is an enterprise specializing in the design, development, manufacture, and sales of precision slewing bearings (slewing rings) and precision slewing drives. As a professional slewing ring supplier, we provide high-performance small and large slewing rings to customers worldwide.

Unlike other providers of slewing bearings, LDB can offer fully tailored slewing bearing solutions with integrated advanced monitoring, lubrication, and sealing systems for higher reliability and longer service life. Our wide range of expert slewing bearing services also helps cut costs and optimize performance, while our global presence allows slewing bearing solutions and services to be delivered quickly around the world.

Customization capabilities
LDB provides a complete set of slewing bearings without gears, external gears, internal gears, or individual ring gears according to customer requirements. We can optimize the sealing structure and internal fixator based on your specific working environment. For split ring designs, we connect the two split rings with bolts before shipment to simplify your on-site installation.

Technical support
LDB has commonly used standard models in stock. For non-standard requirements, our engineering team can design and manufacture according to your specifications. Whether you need a standard model or a fully custom solution, we work closely with you to meet your requirements.

Contact LDB today to discuss your four-point contact ball slewing bearing needs. Provide your load data, size specifications, gear configuration, and any special requirements. We will respond with a competitive quote, technical recommendations, and a reliable delivery schedule.

Slewing Bearings for Armored Combat Vehicles

May 14, 2026/in Bearing Knowledge, Slewing Bearing Knowledge /by LDB Bearing

The modern battlefield demands exceptional structural integrity, speed, and precision from armored combat vehicles (ACVs). Whether navigating rugged, off-road terrain or engaging hostile targets while moving at high speeds, tanks, infantry fighting vehicles (IFVs), and armored personnel carriers rely on advanced subsystems to maintain field dominance. At the core of every modern combat vehicle’s offensive and defensive capability is a highly specialized mechanical component designed to facilitate continuous, smooth rotation under extreme stress: the slewing bearing. Serving as the structural and cinematic link between the heavily armored vehicle chassis and its weapon system, these large-diameter joints are essential to tactical mobility and survivability.

What is Slewing Bearing in Armored Combat Vehicles?

In the context of armored combat vehicles, a slewing bearing is a specialized, low-profile, large-diameter roller or ball bearing engineered to support the full weight of a fully weaponized turret while allowing it to rotate 360 degrees. Far from being a standard industrial component, a military-grade slewing bearing operates as a multi-functional interface. It connects the dynamic upper turret structure—which houses the main armament, complex optical sensors, electronic targeting systems, and crew stations—to the fixed, lower hull of the vehicle.

In wheeled and tracked armored vehicles, these heavy-duty assemblies are placed at the base of the turret ring. The bearing must support the massive static weight of modern main battle tank turrets, which frequently weigh between 10 and 20 metric tons, while keeping the physical profile as low as possible to reduce the vehicle’s total height and target cross-section. Beyond simply acting as a weight-bearing mechanism, the slewing bearing provides a precise pathway for high-torque rotation, allowing electric or hydraulic turret drive systems to swing massive weapon systems toward targets instantly and smoothly.

How Do Turret Slewing Bearings Work Under Combat Shock Loads?

Operating a combat vehicle in an active theatre exposes mechanical components to some of the most violent force combinations in modern engineering. While standard bearings are rated for predictable, steady radial or axial loads, a turret slewing bearing must maintain smooth rotational kinematics while subjected to massive, instantaneous shock events.

The primary mechanical stress occurs during main gun deployment. When a large-caliber cannon (such as a 120mm smoothbore gun) fires, it generates an immense backward force known as recoil shock load. This force travels directly through the gun cradle and into the turret structure, exerting a massive, instantaneous overturning moment on the slewing bearing. The joint must immediately absorb and dissipate these tens of thousands of kilonewtons of energy, preventing the turret from detaching from the hull or tilting out of alignment.

Furthermore, combat vehicles face unexpected threats from beneath, such as improvised explosive devices (IEDs) and anti-tank landmines. When an explosion occurs under the hull, a massive, vertical upward shock wave passes through the vehicle. The internal rolling elements—whether balls or rollers—must distribute this intense energy across the entire circumference of the raceways, preventing severe metal structural deformation or fracturing that could lock the turret in a single position during a tactical engagement.

Key Design Features of Military-Grade Slewing Bearings

To achieve combat-ready status, military-grade designs are modified into highly specialized variants compared to standard heavy-industrial equipment.

Ultra-Low Profile and High Stiffness

To minimize the overall silhouette of the vehicle and lower its visibility to enemy sensors, defense-grade bearings feature an ultra-low profile design. The height of the bearing ring is kept as compact as possible without sacrificing cross-sectional thickness. This geometry provides high structural stiffness, preventing the bearing from flexing or warping when traveling over uneven terrain or encountering heavy terrain vibrations.

Integrated Ballistic Deflectors and Gear Rings

The rings are typically designed with internal or external integrated gear teeth that mesh with the primary turret drive pinions. To prevent foreign object debris (FOD), such as ballistic fragments, shrapnel, sand, or concrete dust, from entering the gear teeth and jamming the rotation, the bearing outer rings are often machined with protective labyrinth barriers or integrated steel deflector lips.

Advanced Seal Architectures for Chemical, Biological, and Radiological (CBRN) Defense

Modern military operations require vehicles to maintain hermetic, over-pressurized crew cabins to shield soldiers from hazardous contaminants. The slewing bearing must feature specialized, multi-stage elastomeric lip seals capable of containing internal cabin pressure while resisting degradation from engine fluids, heavy chemical decontaminants, sand abrasion, and deep water during amphibious or deep-fording maneuvers.

Advanced Metallurgy and Hardening Solutions for Defense-Grade Bearings

The exceptional load demands and environmental hazards of defense applications require specialized metallurgy and advanced thermal processing. Standard commercial steel alloys are prone to structural fatigue or cracking under sudden ballistic shock loads.

The structural rings of military slewing bearings are typically forged from high-cleanliness, vacuum-degassed alloy steels, such as premium-grade 42CrMo4 or equivalent Cr-Mo steel variants, which are thoroughly quenched and tempered to guarantee optimal core toughness, high impact resistance, and excellent yield strength at sub-zero temperatures. The internal raceways then undergo medium-frequency induction hardening. This precise thermal treatment hardens the raceway surfaces to 55–60 HRC while maintaining a ductile, shock-absorbing core. The depth of this induction-hardened layer is closely monitored, as a deep case depth is required to prevent subsurface micro-cracking and spalling when subjected to heavy main gun recoil forces.

The rolling elements are also engineered for maximum durability. Manufacturers utilize high-precision carbon-chromium bearing steel or advanced silicon nitride ceramic rolling elements. Ceramic elements offer advantages such as lower weight, reduced friction, and an immunity to metal micro-welding, which ensures smooth operation even if the internal lubrication film is temporarily disrupted during heavy combat maneuvers.

Advantages of Precision Slewing Bearings in Combat Target Acquisition

In a tactical engagement, the speed and accuracy of a vehicle’s target acquisition system directly determine its survivability. A precision-engineered slewing bearing delivers key operational advantages that improve a platform’s lethality by optimizing target stabilization and precision execution.

Eliminating Backlash for Stabilized Fire Control

Modern main battle tanks rely on stabilized fire control systems to track and engage enemy targets while traveling at high speeds over rough terrain. This requires a zero-backlash or preloaded bearing design, such as a high-precision cross roller slewing bearing. By crossing cylindrical rollers at right angles alternately between the rings, this configuration eliminates internal play and mechanical play. This structural rigidity successfully prevents the turret from wobbling or vibrating under heavy vibrations, allowing the stabilizer gyroscopes and laser designators to maintain a precise, continuous target lock even during violent maneuvers.

Enhancing High-Speed Slew and Micro-Targeting Accuracy

When ambushed or facing multiple threat vectors simultaneously, the turret must rotate rapidly to counter incoming targets. A high-quality four point contact ball slewing bearing provides exceptionally low, consistent frictional torque across all rotational angles. This uniform internal friction allows the turret drive actuators to smoothly shift from maximum high-speed rotation to delicate, fraction-of-a-degree micro-adjustments required for long-range target locking, ensuring excellent first-round hit capabilities under intense combat duress.

Ensuring Tactical Reliability and Low Maintenance in Theatre

When deployed in remote, high-threat operational areas, logistics supply chains can face significant disruption. Defense equipment must function reliably for extended periods with minimal field maintenance.

A premium, military-grade joint addresses these theater challenges through several engineering improvements:

Redundant Lubrication Channels: Rings are machined with multiple, independent lubrication entry ports, ensuring grease is distributed evenly across the raceways even if individual ports become clogged with debris or battlefield contaminants.
Excellent Wear Margins: Optimized internal track geometries distribute heavy loads evenly, preventing localized stress concentrations and extending field service life without mid-lifecycle teardowns.
Simplified Field Swap Configurations: In field service scenarios, a flanged slewing bearing design simplifies maintenance. Flanged rings distribute high bolt-clamping forces evenly and feature standard bolt spacing, allowing forward repair teams to perform swift replacements using basic field tools.

The Future of Turret Slewing Bearings in Next-Generation Armored Vehicles

As defense forces transition toward modern digital warfare and highly autonomous mobile platforms, the technical specifications for vehicle turret rings are shifting rapidly to meet future operational demands.

The Rise of Unmanned and Remote Turrets

Modern armored fighting vehicle designs are increasingly adopting unmanned, remote-controlled turret systems. By removing the crew from the upper turret structure, the overall weight of the turret can be reduced. This allows for lower-weight, thinner-profile slewing bearings, which optimizes vehicle weight distribution and frees up weight budget for advanced active protection armor plates.

Integration of High-Energy Systems

Future combat platforms are integrating directed-energy weapons, such as high-power tactical lasers and electromagnetic rail systems. These systems place new demands on the turret bearing, which must provide stable ground paths for high electrical currents while protecting internal rolling elements from electrical pitting or magnetic arc damage.

Smart Sensor Integration

Next-generation bearings are increasingly being integrated with internal sensor packages. By embedding electronic strain gauges, thermistors, and vibration sensors directly into the stationary ring, the vehicle’s onboard computer can continuously monitor the health of the joint, alerting mechanics to maintenance needs well before a physical failure occurs.

LDB: Custom Slewing Bearings Supplier in China

Operating in the demanding military and defense sector requires reliable, field-tested manufacturing partners capable of delivering exceptional accuracy and durability. Luoyang Longda Bearing Co., Ltd. (LDB-Bearing) was established in 1999 and is located in China’s bearing production base – Luoyang, Henan. LDB Bearing has a product range from 150mm to 4000mm in diameter slew bearing and gear rings, covering the production and manufacturing of various standard and non-standard specifications of slew bearings.

LDB has design and manufacturing expertise in slew bearing and slew drive across a diverse range of markets and industries. Backed by comprehensive advanced engineering modeling, rigorous material testing, and strict quality control processes, LDB produces high-integrity components capable of enduring extreme tactical environments and high-shock load conditions.
If you need slewing bearing for your project, or want to consult some related knowledge, you are welcome to contact us at any time, our professional technology and expertise can provide you with the best solution to meet your different needs.

Slewing Bearings in Tidal and Wave Energy

May 13, 2026/in Bearing Knowledge, Slewing Bearing Knowledge /by LDB Bearing

The global transition toward green energy has turned the spotlight onto oceans as a massive source of untapped power. Tidal current turbines and wave energy converters (WECs) are rapidly advancing from experimental prototypes to commercial-scale installations. Operating in the world’s harshest marine environments requires high-performance machinery. Every subsea system depends on a robust, highly optimized mechanical joint to handle enormous, unpredictable multi-directional forces: the slewing bearing.

What is Slewing Bearing in Tidal and Wave Energy Systems?

In marine renewable energy systems, a slewing bearings serves as the heavy-duty mechanical “joint” that enables controlled rotational movement between structural components. These large-diameter, low-speed bearings act as the primary connection point between stationary foundations and dynamic, power-capturing elements. They ensure that heavy marine machinery can adapt smoothly to changing environmental inputs without sacrificing structural integrity.

In tidal stream applications, these components are strategically integrated into two critical subsystems. First, they are utilized in Yaw Systems, connecting the main turbine nacelle to the fixed tower or seabed foundation. This allows the entire structure to rotate and align perfectly with incoming or receding tidal currents, mitigating structural stress while maximizing kinetic capture. Second, they are deployed in Pitch Systems at the root of the turbine blades. These systems constantly regulate blade angles relative to fluid flow speeds to optimize power generation and protect the rotor during extreme storm surges.

For wave energy converters, the applications are even more diverse due to the varied kinematics of wave motion. Devices like oscillating wave surge converters, attenuators, and point absorbers use these robust components within their articulated joints, mooring pivots, and power take-off (PTO) link arms to smoothly translate multi-directional wave motions into linear or rotational power.

How Do Slewing Bearings Work Under the Sea?

Operating submerged or in the splash zone presents complex kinematic challenges. Unlike high-speed industrial bearings found in automotive or manufacturing plants, subsea applications operate under low rotational speeds (often less than 10 RPM) but must bear massive, complex force combinations.

When ocean currents strike turbine blades or waves slam into a WEC flap, the mechanical joint experiences a simultaneous combination of severe loads. Axial forces push down directly along the axis of rotation due to gravity and hydrostatic pressure. Simultaneously, radial forces push perpendicular to the shaft, caused by cross-current shear or direct wave impact. Most destructively, massive overturning moments exert intense leverage forces that try to tilt or rock the bearing rings apart, exacerbated by long turbine blades or tall wave-capturing structures.

To accommodate these demands, internal rolling elements roll along precisely machined raceways designed to distribute these multi-axial loads evenly. For lighter loads or high-vibration oscillating applications, a four point contact ball slewing bearing uses unique gothic-arch raceways to efficiently transmit axial, radial, and moment loads through a single row of balls, saving valuable space inside the subsea enclosure.

When loads scale up, systems often upgrade to a double row ball slewing bearing or a specialized double row different diameter ball slewing bearing. This configuration uses a larger ball row to handle heavy downward axial thrust and a smaller ball row to manage uplift and stabilizing loads, optimizing internal stress distribution and extending the fatigue life of the raceways.

For the most extreme, megawatt-scale deepwater installations, systems utilize a heavy-duty three-row roller slewing bearings setup. This design separates axial and radial loads into individual horizontal and vertical roller rows, maximizing rigidity and load capacities within a compact footprint while resisting extreme structural deflections.

Key Design Features of Marine-Grade Slewing Bearings

To survive subsea deployment without catastrophic premature failure, standard industrial designs are heavily modified into highly specialized, marine-grade variants capable of withstanding deep-sea hydrostatic pressure and continuous saltwater exposure.

Advanced Sealing Architectures

Seawater ingress causes rapid grease degradation, raceway scoring, and galvanic corrosion. Marine-grade systems utilize multiple lip seals made of high-nitrile elastomers, combined with stainless steel mechanical face guards or maze rings. The interior cavity is often maintained at a slight positive pressure (+0.5 bar above ambient hydrostatic pressure) via an automated lubrication system, creating an active barrier that prevents saltwater from passing the sealing lips even during deep subsea submersion.

Structural Rigidity & Integrated Gearing

Because structural deflection can concentrate stress on the rolling elements and cause premature fatigue cracking, the outer and inner rings feature extra-thick cross sections to prevent distortion under extreme load spikes. To streamline the drivetrain and reduce total component counts, these rings are engineered with precision integrated gearing. Depending on the space limitations of the nacelle or articulation housing, engineers specify an internal or external gear ring to mesh directly with hydraulic or electric drive pinions, ensuring smooth and reliable torque transmission.

Advanced Material Solutions of Slewing Bearing in Tidal and Wave Energy Systems

The combination of high salinity, dissolved oxygen, and microbiologically influenced corrosion (MIC) makes the ocean one of the most destructive environments on earth. Marine-grade components rely on a combination of advanced metallurgy and multi-layered surface treatments to ensure long-term reliability.

The base rings are typically forged from high-quality alloy steels like 42CrMo4, which undergo precise quenching and tempering to achieve high core toughness and excellent yield strength under impact. The internal raceway surfaces are then subjected to medium-frequency induction hardening, reaching a hardness of 55–60 HRC to prevent subsurface fatigue pitting. Rolling elements are manufactured from high-chromium carbon steel or specialized ceramic materials to resist flat-spotting and eliminate metal-to-metal micro-welding under boundary lubrication conditions.

Externally, the entire assembly is protected by advanced corrosion-resistant coatings. Technologies such as Thermal Spray Aluminum (TSA), zinc-nickel plating, or multi-layer epoxy systems provide critical sacrificial cathodic protection against salt spray and water. For applications requiring weight reductions or simplified mounting in compact marine enclosures, a flanged slewing bearing is often selected. The integrated L-shaped or I-shaped flanges feature pre-drilled bolt holes that distribute clamping forces evenly across the mounting structure, reducing stress concentrations and simplifying underwater installation by commercial divers or remote operated vehicles (ROVs).

Advantages of Precision Slewing Bearings in Maximizing Marine Energy Yield

Every micrometer of play or millisecond of lag in an offshore energy asset directly impacts power output and return on investment. Precision engineering delivers tangible thermodynamic and financial benefits to tidal and wave energy operators.

Optimizing Hydrodynamic Alignment

Tidal currents shift directions with changing tides, and waves approach from fluctuating vectors. A precision-engineered yaw bearing ensures the entire harvesting apparatus can orient itself smoothly and accurately. By keeping the rotor or wave flap at a perfect angle to the fluid flow, the system maximizes kinetic energy capture and prevents cosine losses caused by misalignment, ensuring the plant operates at peak aerodynamic and hydrodynamic efficiency.

Minimizing Friction and Power Dissipation

High-quality internal geometries, such as those found in a cross roller slewing bearing, offer distinct advantages for oscillating wave energy converters. By crossing cylindrical rollers at right angles alternately between the rings, this design achieves excellent rotational accuracy, eliminates internal play, and maintains a highly consistent, low frictional torque. Lower internal friction ensures that even small, low-amplitude wave movements are successfully captured and converted into electricity, instead of being lost as heat within the joint.

Minimizing O&M Costs in Remote Offshore Environments

Deploying heavy engineering vessels, specialized crane barges, and deep-sea dive teams to service a failed component can cost hundreds of thousands of dollars per day. In offshore renewables, minimizing Operations and Maintenance (O&M) costs is critical to lowering the Levelized Cost of Energy (LCOE) and making ocean energy cost-competitive with onshore wind and solar.

Investing in premium subsea-engineered joints reduces these financial risks through extended wear life, where deep-case induction hardening and optimized roller profiles prevent micro-pitting and raceway fatigue, eliminating the need for mid-lifecycle field overhauls. Furthermore, modern intelligent units feature built-in fiber-optic strain gauges, temperature sensors, and acoustic emission transceivers. These systems stream real-time health data back to shore, enabling predictive maintenance before a component fails. Optimized internal cavities also feature dedicated grease evacuation channels that pump used lubricants cleanly into containment bladders rather than venting into the ocean, complying with strict maritime environmental laws while preventing lubricant starvation.

The Future of Slewing Bearings in Emerging Marine Renewable Tech

As the marine energy industry scales up to multi-megawatt platforms, mechanical demands are increasing exponentially. Next-generation designs are evolving to meet these challenges through several key advancements.

Tidal turbines are expanding toward 2-megawatt to 3-megawatt outputs, requiring rotor diameters that rival large onshore wind turbines. Future yaw and pitch systems will exceed 4 to 5 meters in diameter, demanding advanced manufacturing techniques to maintain structural integrity and precision geometry across large-scale components. Additionally, manufacturers are increasingly building digital twins of operating units by pairing real-time sensor data with advanced finite element models. These systems calculate real-time fatiguing loads based on actual ocean conditions, allowing operators to adjust turbine orientation during heavy storms to extend the asset’s operating life. To handle the unpredictable, multi-directional pounding of deep-sea waves, designers are shifting toward hybrid internal layouts that combine the high moment rigidity of roller tracks with the low frictional properties of ball tracks to optimize overall platform stability.

LDB: Custom Slewing Bearings supplier in Emerging Marine Renewable Tech

Operating in the demanding marine renewable sector requires reliable, field-tested manufacturing partners. LDB delivers high-end engineering expertise tailored to these challenging environments.

With comprehensive manufacturing capabilities, LDB designs and builds tailored solutions ranging from high-capacity three-row roller slewing bearings to precise four point contact ball slewing bearings. Backed by advanced Finite Element Analysis (FEA) and multi-step non-destructive testing (NDT), every assembly is engineered to withstand extreme subsea loads, high salinity, and long operational life cycles.

LDB’s commitment to quality control and technical expertise ensures that each product complies with international maritime standards. Whether building a breakthrough tidal stream array or a next-generation wave energy farm, LDB provides the customized engineering support, advanced material treatments, and reliable sealing systems needed to secure your subsea investments and ensure peak operational uptime.
Let LDB’s custom slewing bearing solutions safeguard your offshore assets, maximize your energy yield, and drive down your lifetime operational costs.

Delivery of Doosan Excavator Slewing Bearing to South America

May 12, 2026/in LDB Company News /by LDB Bearing

In November 2022, our company successfully delivered a Four-Point Contact Ball Slewing Bearing for a Doosan excavator to a client in South America. The customer needed a high-performance slewing ring to support demanding applications such as earthmoving, construction, and infrastructure development. We supplied a four-point contact ball slewing bearing, which features a single row of steel balls with four contact points between each ball and the raceway. This design allows the bearing to withstand axial loads, radial loads, and tilting moments simultaneously.

Manufactured from high-strength 42CrMo and 50Mn steel, this bearing offers a compact structure, light weight, and high static load capacity ranging from 129kN to 3,410kN. LDB provides outer diameters from 200mm to 10,000mm, inner diameters from 100mm to 8,000mm, and ball diameters from 30mm to 75mm to meet various excavator models. After rigorous factory testing including dimensional inspection, hardness testing (raceway quenching hardness HRC 55-62), and gear accuracy verification, we shipped the bearing in November 2022. We used anti-corrosion treatment and export-standard fumigation-free wooden boxes for secure ocean freight to South America.

The customer confirmed successful installation and reported that the four-point contact ball slewing bearing delivered smooth rotation, low noise, and stable performance under daily operating conditions. LDB provides a 12-month warranty, 10-30 day delivery, and flexible gear options including internal gear, external gear, or non-gear configurations. For split ring designs, we pre-connect the two split rings with bolts before shipment to simplify on-site installation. This case further demonstrates our capability to serve Doosan excavator users across South America with custom-engineered slewing solutions.

What Are Four-Point Contact Ball Slewing Bearings?

A four-point contact ball slewing bearing is a specialized heavy-load bearing that enables smooth rotation in large machinery. The main components include an inner ring, an outer ring, a single row of steel balls, a cage or spacer, and a sealing device. Manufacturers offer both integral and split designs for the inner and outer rings. An integral ring provides excellent rigidity, while a split ring gives you more flexibility during adjustment. For split designs, LDB uses bolts to fasten the two split rings together before shipping.

Most of these bearings come with a cage or spacer. However, when your application demands extra load capacity, a full-ball design works better. Keep in mind that full-ball bearings carry more load but also create higher friction. This friction may lead to surface scratches on the steel balls over time. You can order four-point contact ball slewing bearings with no gear, external gear, or internal gear teeth. All configurations deliver impressive static load capacity for tough working conditions.

How Does a Four-Point Contact Ball Slewing Bearing Work?

The operating principle of this bearing type centers on the interaction between steel balls and arc-shaped raceways. Each steel ball touches the raceway at four distinct points—two points on the inner ring and two points on the outer ring. This clever geometry allows a single bearing to manage axial loads coming from either direction, radial loads, and tilting moments all at once.

When heavy forces enter the bearing, the steel balls distribute those forces across the four contact points. The load distribution shifts depending on the force direction. Pure vertical loads engage all four contact points evenly. Combined loads cause some points to carry more force while others relax. This dynamic behavior explains why one bearing can replace multiple bearing types in complex applications. A pinion gear drives the system by engaging the internal or external gear teeth on the bearing ring. As the pinion turns, the bearing ring rotates, and your equipment moves smoothly with very little friction.

Structural Features of Four-Point Contact Ball Slewing Bearings

These bearings stand out because of their smart structural design. The single-row configuration uses two seat rings, which keeps the whole assembly compact and surprisingly lightweight. The steel balls contact the arc raceway at four points, giving the bearing the ability to handle axial forces, radial forces, and tilting moments all in one unit.

LDB builds these bearings with outer diameters between 300mm and 10,000mm. Ball diameters range from 30mm to 75mm, while rated loads fall between 129kN and 3,410kN. We choose 42CrMo and 50Mn steel for their outstanding strength and resistance to wear. The seals use nitrile rubber, a material that keeps contaminants out and lubrication in. Heat treatment follows strict standards: normalizing hardness reaches 187HB-241HB, quenching and tempering delivers 229HB-269HB, and raceway quenching hits HRC 55-62. Every LDB bearing comes with a 12-month warranty and ships within 10 to 30 days.

Main Configuration Types of Four-Point Contact Spherical Slewing Bearings

You have three main choices when it comes to gear configuration:

Non-Gear Type (No Tooth)
This version has no gear teeth on either ring. It works perfectly when your drive system operates independently of the bearing itself.

External Gear Type (External Tooth)
The outer ring carries gear teeth on its outside surface. A pinion gear engages these teeth from the exterior. This setup fits applications where the drive motor sits outside the rotating part.

Internal Gear Type (Internal Tooth)
The inner ring holds gear teeth on its inside surface. The pinion mounts within the bearing ring. This arrangement gives you a cleaner look and adds protection to the gear mechanism.

LDB offers all three types, and we can match the gear configuration precisely to your mechanical layout. You also get to choose between integral and split ring structures. All options feature four-point contact with your selected tooth configuration.

Core Advantages of Four-Point Contact Spherical Slewing Bearings

Why do engineers choose four-point contact ball slewing bearings over other options? Here are the main benefits:

One bearing does the work of several
A single four-point contact ball slewing bearing handles axial loads, radial loads, and tilting moments together. You no longer need separate bearing types in your assembly.

Small and light
The single-row design uses just two seat rings. This simplicity saves valuable space and keeps weight low, helping you build more compact machinery.

Handles high static loads with ease
The four-point contact pattern spreads loads efficiently. The bearing can support extremely high static loads without permanent damage.

Works equally well for both axial directions
Many bearings only accept axial loads from one direction. This design accepts axial forces from either direction without any performance difference.

Turns smoothly with low resistance
Precision-ground raceways and quality steel balls deliver quiet, easy rotation. You get lower power consumption and reduced wear over time.

Built to last
This bearing series suits equipment that demands high axial loads, strong overturning moment resistance, continuous operation, and a long service life.

Customizable for your environment
Based on your specific working conditions, LDB can modify the sealing structure and internal fixator to match your needs.

Common Applications of Four-Point Contact Spherical Slewing Bearings

You will find these bearings working hard in many different types of equipment:

Construction machinery
Rotary conveyors, welding robots, manipulators, small and medium cranes, and excavators all rely on these bearings. Their ability to manage combined loads makes them perfect for rotating equipment under heavy weight.

Tower parking systems
Automated parking garages use four-point contact ball slewing bearings to rotate car platforms with precision and smoothness.

Cranes and hoists
Mobile cranes, tower cranes, and marine cranes all depend on these bearings for their slewing functions.

Excavators and earthmoving gear
Both medium-sized and small excavators benefit from the compact size and high load capacity of this bearing type.

Wind turbines
Many yaw and pitch systems in wind turbines use these bearings because they handle combined loads well in outdoor conditions.

Medical equipment
Large medical imaging machines and robotic surgery systems use these bearings for accurate rotational positioning.

Key Factors When Choosing a Four-Point Contact Ball Slewing Bearing

Before you order a slewing bearing, consider these important factors:

Load demands
Figure out the maximum axial load, radial load, and tilting moment your application will create. LDB’s rated load range of 129kN to 3,410kN suits most medium and heavy-duty jobs. Send your load data to our team for precise sizing.

Gear type
Pick no gear, internal gear, or external gear based on your drive layout. Internal gear works when your motor mounts inside the bearing ring. External gear fits when your motor sits outside.

Ring design
Choose integral ring for maximum rigidity. Choose split ring for easier adjustment during installation. LDB pre-assembles split rings with bolts before shipping to save you time.

Size specifications
Tell us your required inner diameter (100mm to 8,000mm) and outer diameter (200mm to 10,000mm). Ball diameter (30mm to 75mm) affects both load capacity and rotation smoothness.

Seal needs
Standard nitrile rubber seals work for most environments. For harsh or dusty conditions, LDB can create special sealing designs to keep contaminants away.

Hardness requirements
Check that hardness levels match your application. LDB delivers normalizing hardness of 187HB-241HB, quenched and tempered hardness of 229HB-269HB, and raceway hardness of HRC 55-62.

Cage vs. full-ball
Use a cage design for most standard applications. Choose the full-ball structure only when you need maximum load capacity and can accept higher friction.

Delivery schedule
LDB’s standard delivery takes 10 to 30 days. For urgent projects, contact us to discuss faster options.

Standard or custom
LDB keeps common standard models in stock. For non-standard requirements, we design and manufacture according to your exact specifications.

LDB: Custom Four-Point Contact Ball Slewing Bearings Manufacturer

LDB stands as a professional enterprise dedicated to the design, development, manufacturing, and sales of precision slewing bearings and slewing drives. We deliver high-performance small and large slewing rings to customers across the globe.

What makes LDB different from other suppliers? We offer fully customized slewing bearing solutions. Our team integrates advanced monitoring systems, lubrication mechanisms, and sealing technologies to give you higher reliability and extended service life. Our comprehensive service offerings help you reduce costs while optimizing performance. Thanks to our worldwide presence, we can deliver solutions and support quickly no matter where you are located.

Customization options
LDB supplies complete slewing bearing sets with no gear, external gear, internal gear, or individual ring gears based on your specific requirements. We can redesign the sealing structure and internal fixator to match your working environment perfectly. For split ring designs, we pre-connect the two halves with bolts before shipment to make your installation process easier.

Quality you can trust
Every bearing passes through rigorous quality checks before leaving our factory. We verify dimensional accuracy, hardness levels, gear quality, and raceway surface finish. Our heat treatment process includes normalizing, quenching and tempering, and induction hardening to achieve the target raceway hardness of HRC 55-62.

Packaging and shipping
Each bearing travels in a metal bracket or an export-standard fumigation-free wooden box. This packaging guarantees safe delivery to any destination worldwide. We back every product with a 12-month warranty and a standard lead time of 10 to 30 days.

Technical support
LDB maintains inventory of common standard models for quick shipment. For non-standard requirements, our engineering team designs and manufactures to your specifications. Whether you need a standard product or a fully custom solution, we work closely with you to meet your goals.

Contact LDB today to discuss your four-point contact ball slewing bearing requirements. Share your load data, size specifications, gear configuration, and any special needs. We will provide a competitive quote, technical recommendations, and a reliable delivery schedule.

Large Slewing Bearings: Key Applications and Engineering Insights

May 12, 2026/in Bearing Knowledge, Slewing Bearing Knowledge /by LDB Bearing

What Are Large Slewing Bearings?

Large slewing bearings are heavy-duty, oversized rotational components designed to handle complex loads that standard bearings cannot manage. Unlike conventional bearings that typically support only radial or axial loads individually, large slewing bearings are specifically engineered to accommodate radial forces, axial forces, and tilting moment loads simultaneously. This unique capability makes them essential for any machinery that requires smooth, controlled rotation while supporting significant weight.

A typical large slewing bearing consists of an inner ring, an outer ring, a set of rolling elements (steel balls or rollers), and often gear teeth integrated into one of the rings. These components are manufactured from high-strength steel alloys such as 42CrMo or 50Mn, with raceways induction-hardened to achieve surface hardness of HRC 55-62. The result is a durable, reliable component that can operate for decades under extreme conditions.

How Do Large Slewing Bearings Handle Complex Loads?

The working principle of large slewing bearings lies in their unique raceway geometry and multiple rows of rolling elements. Depending on the specific design – whether single-row four-point contact, double-row ball, or cross-roller – these bearings distribute applied forces across multiple contact points between the rolling elements and the raceways.

In a Four Point Contact Ball Slewing Bearing , each steel ball contacts the raceway at four distinct points – two on the inner ring and two on the outer ring. This geometry allows the bearing to manage axial loads from either direction, radial loads, and tilting moments within a single, compact row. In double-row designs, there are two separate raceways and eight points of contact per ball, providing even higher load capacity and greater structural rigidity.

When a piece of heavy machinery operates – for example, a crane lifting a steel beam – the slewing bearing at its base experiences downward axial force from the weight, radial force from the boom’s extension, and a tilting moment that tries to tip the structure. The bearing’s internal geometry resists all three forces simultaneously, keeping the rotation smooth and the structure stable.

Common Applications of Large Slewing Bearings Across Major Industries

Large slewing bearings are the unsung heroes behind many of the world’s most impressive machines. Their ability to enable smooth rotation under extreme loads makes them indispensable across four major industrial sectors.

Heavy Construction and Earthmoving Equipment

The construction industry relies heavily on rotational machinery. On any major building site, large slewing bearings are hard at work. Tower cranes and mobile cranes use these bearings at their base or turntable to allow the boom to swing a full 360 degrees while carrying immense weight. Without a reliable slewing bearing, the crane could not rotate smoothly or safely.

Excavators represent another critical application. A slewing ring is mounted between the undercarriage (tracks) and the main body (cabin). This allows the operator to rotate the cabin and digging arm independently of the track direction, drastically improving digging efficiency and site mobility. Whether the machine is digging a foundation or loading trucks, the slewing bearing enables continuous, precise rotation under heavy and often shock loads.

Renewable Energy Systems

The global push for green energy has created massive demand for precision engineering, and large slewing bearings are absolutely essential in this sector, particularly in wind and solar power.

On wind turbines, two types of slewing bearings are critical. Yaw bearings are installed between the tower and the nacelle (the housing at the top containing the generator). They allow the entire nacelle to rotate and face directly into the wind, optimizing energy capture as wind direction changes. Pitch bearings are mounted at the base of each turbine blade, allowing the blade angle to be adjusted. This adjustment optimizes power capture during normal operation and feathers the blades to prevent damage during severe storms.

In large-scale solar farms, dual-axis solar trackers incorporate slewing bearings to follow the sun’s trajectory across the sky. By keeping solar panels oriented directly at the sun throughout the day, these systems can increase energy absorption by 30-40% compared to fixed installations.

Marine and Offshore Industries

The marine and offshore sectors demand equipment that can withstand harsh, corrosive environments while managing extreme loads. Deck cranes on cargo ships, which lift containers from holds to docks, rely on large slewing bearings for their rotational function. Offshore oil rig platforms use slewing bearings in cranes and pipe-handling equipment, where saltwater spray and constant motion create uniquely challenging conditions.

Specialized underwater remotely operated vehicles (ROVs) used for subsea inspection and maintenance also incorporate compact slewing bearings in their manipulator arms and thrusters. In all these marine applications, slewing bearings are often custom-engineered with specialized anti-corrosive coatings and superior sealing systems to prevent saltwater intrusion and ensure a long operational lifespan.

Industrial Robotics and Manufacturing

The automation of heavy manufacturing requires robust rotational joints. Heavy-duty industrial robots – such as those used in automotive assembly lines to lift and position car chassis – rely on slewing bearings at their base and major pivot points. These bearings must provide not only high load capacity but also precise positioning and low friction for accurate, repeatable movements.

Large industrial turntables, packaging machines, and material handling systems use slewing rings to index heavy loads quickly and accurately. For example, a turntable in a manufacturing cell might rotate a heavy engine block between multiple workstations. The slewing bearing ensures smooth, precise indexing, keeping production lines moving without interruption.

Core Advantages of Large Slewing Bearings Across Industries

Large slewing bearings offer several distinct advantages that make them the preferred choice for demanding rotational applications.

High Load Capacity – These bearings are designed to handle massive static and dynamic loads. Depending on size and configuration, a single large slewing bearing can support hundreds of tons while maintaining smooth rotation.

Combined Load Management – Unlike standard bearings that struggle with multiple load directions, large slewing bearings are specifically engineered to simultaneously manage axial, radial, and tilting moment forces.

Compact Integration – By combining load support and rotational guidance into a single component, slewing bearings simplify machine design. The ability to integrate gear teeth directly into the bearing ring eliminates the need for separate drive components.

Durability in Harsh Environments – With proper material selection, heat treatment (HRC 55-62 raceway hardness), and sealing systems, large slewing bearings can operate reliably for decades in environments ranging from dusty construction sites to corrosive offshore platforms.

Customizability – Large slewing bearings can be tailored to specific applications, including choices of gear type (internal, external, or no gear), ring material (42CrMo, 50Mn, C45), rolling elements (balls or rollers), and sealing arrangements.

Selecting the Right Large Slewing Bearing

Not all slewing bearings are created equal. Because the applications for large slewing bearings involve such extreme weights and critical safety standards, choosing the right specification is vital.

Engineers must carefully calculate the following factors before selecting a bearing:

Load requirements – Maximum axial load, radial load, and tilting moment (kN·m) that the bearing will experience under normal and peak operating conditions.
Rotational speed – While large slewing bearings typically operate at slow speeds, the number of rotations per day or year affects fatigue life calculations.
Environmental conditions – Temperature extremes, dust, moisture, chemical exposure, and the presence of saltwater or other corrosives all influence material and seal selection.
Mounting structure – The stiffness and flatness of the supporting structure affect load distribution across the bearing.
Drive configuration – Gear type (internal, external, or no gear) must match the machine’s drive system.
Maintenance access – Available space for lubrication fittings, inspection, and potential replacement should be considered early in the design process.

Working with an experienced manufacturer that provides engineering support during the selection process helps ensure that the final bearing meets both performance requirements and operational expectations.

Conclusion

Large slewing bearings are critical components that enable rotation in heavy machinery across construction, renewable energy, marine, and industrial automation sectors. Their ability to simultaneously handle axial loads, radial loads, and tilting moments makes them indispensable for equipment ranging from tower cranes and excavators to wind turbines and solar trackers.

By understanding what these bearings are, how they work, and where they are applied, engineers and equipment operators can make informed decisions that improve machine reliability and operational safety. The right slewing bearing – properly selected, correctly installed, and regularly maintained – will provide decades of trouble-free service, turning silently beneath thousands of tons of steel and concrete.

LDB: A Trusted Supplier of Large Slewing Bearings

LDB (Luoyang Longda) is a professional manufacturer specializing in the production and sales of high-quality slewing bearings, slewing drives, and gear transmission devices. With years of experience in the industry, LDB serves customers across construction machinery, renewable energy, marine equipment, and industrial automation.

LDB’s large slewing bearings are manufactured using premium materials including 42CrMo, 50Mn, and C45, with rolling elements made from GCr15 bearing steel. Raceways are induction-hardened to HRC 55-62, providing excellent wear resistance and long operational life. Outer diameters range from 300 mm to 10,000 mm, and gear configurations include no gear, internal gear, or external gear to suit various drive systems.

LDB offers a standard lead time of 30 days for custom orders, with flexible customization options including ring material, cage material (steel 20 or ZL112 cast aluminum alloy), spacer material (nylon 6 or nylon 66), and sealing systems. All products undergo rigorous inspection and testing before shipment, including dimensional accuracy, rotational torque, and raceway hardness checks. Finished bearings are protected with anti-corrosion oil and packaged in metal brackets or export-standard fumigation-free wooden boxes.

Whether the application is a tower crane on a construction site, a yaw bearing in a wind turbine, a deck crane on a cargo ship, or a turntable in an automated manufacturing line, LDB provides reliable, custom-engineered large slewing bearings that meet demanding performance requirements.

FAQ: Common Questions About Large Slewing Bearing Applications

Q1: What is the difference between a single-row and a double-row large slewing bearing?

A single-row slewing bearing typically uses a four-point contact ball design, where each ball contacts the raceway at four points, allowing it to handle axial loads from both directions, radial loads, and tilting moments in one compact row. A double-row slewing bearing uses two separate rows of balls with eight points of contact per ball, providing higher load capacity, greater rigidity, and longer service life for the most demanding applications such as wind turbines and concrete pump trucks.

Q2: How often do large slewing bearings need maintenance?

Maintenance intervals depend on the application, operating environment, and duty cycle. For construction equipment like excavators and cranes, lubrication is typically required every 150-200 operating hours or weekly. For wind turbines, yaw and pitch bearings are often lubricated at scheduled service intervals every 6-12 months. Marine applications may require more frequent inspection due to corrosive saltwater exposure. Always follow the manufacturer’s recommendations for lubrication type and frequency.

Q3: Can large slewing bearings be repaired, or must they be replaced when damaged?

Minor damage such as localized pitting or surface corrosion can sometimes be repaired through re-grinding raceways or replacing rolling elements. However, significant damage to raceways, gear teeth, or ring structural integrity typically requires full replacement. LDB offers engineering support to assess bearing condition and recommend the most cost-effective solution, including remanufacturing services for certain bearing types.

Q4: What factors shorten the service life of a large slewing bearing?

The most common factors include inadequate or contaminated lubrication, improper installation (uneven mounting surfaces or incorrect bolt torque), exceeding rated load capacities, exposure to severe contamination (sand, water, chemicals), and lack of regular inspection. Proper selection, correct installation, and a disciplined maintenance program are essential to achieving the bearing’s expected service life.

Q5: How do I select the right gear type (internal, external, or no gear) for my application?

External gear configurations are most common for construction machinery like excavators and cranes, where the pinion drives the outer ring. Internal gears are often preferred for wind turbines and compact installations where space is limited and the drive pinion can be placed inside the bearing envelope. No gear (plain) bearings are used when rotation is driven by friction rollers or separate ring gears. The choice depends on your machine’s drive system design, available space, and maintenance access requirements.

Delivery of Komatsu Excavator Slewing Ring to South America

May 8, 2026/in LDB Company News /by LDB Bearing

In the field of construction machinery, the quality and timely delivery of slewing rings directly affect the stable operation of host equipment. In August 2021, our company successfully completed a supply task for a Komatsu excavator slewing ring to a client in South America. This case demonstrates our supply chain capability and professional understanding of the Four-Point Contact Ball Slewing Bearing.

The slewing ring supplied is of the four-point contact ball type. This bearing features a single raceway design where each ball contacts the raceway at four distinct points, allowing it to simultaneously withstand axial loads, radial loads, and tilting moments. Compared to other designs, it offers higher load efficiency, a compact cross-section, and good impact resistance, making it particularly suitable for excavators.

The client in South America explicitly requested a four-point contact ball slewing bearing for their Komatsu excavator. After order confirmation, our company strictly controlled every stage of production, inspection, and packaging. The slewing rings were shipped in August 2021 via a dedicated South America logistics route. Each unit underwent dimensional accuracy, rotational flexibility, hardness, and flaw detection tests to confirm compliance with Komatsu standards. Anti-corrosion treatment and reinforced packaging were applied for long-distance ocean transportation.

Upon arrival in South America, the slewing rings were installed and tested. The customer reported excellent performance, including low friction, high rigidity, and stable rotational accuracy, effectively reducing slewing noise and vibration. This case proves our company’s professional capability in critical components for construction machinery, from product selection and quality control to international logistics.

What is a Four Point Contact Ball Slewing Bearing?

A four point contact ball slewing bearing is a precision rotary component primarily composed of an inner ring, an outer ring, a single row of steel balls, a cage (or spacer), and sealing devices. Both the inner and outer rings can be manufactured as either integral or split structures. Integral rings offer higher rigidity, while split rings allow for easier adjustment. For split structures, bolts are used to connect the two split rings before the product leaves the factory.

This type of slewing bearing generally includes a cage or spacer to separate the balls. However, a full-ball (no cage) structure is used when load requirements are relatively high. The full-ball design provides larger load capacity but comes with higher frictional resistance, which can potentially cause scratches on the surface layer of the steel balls.

The basic structure of a four point contact ball slewing bearing is available in three gear configurations: without gear, with external gear, or with internal gear. All configurations offer high static load capacity. As a product of LDB (Luoyang Longda), this bearing type is manufactured with materials including 42CrMo and 50Mn, with nitrile rubber seals as standard.

How Does a Four Point Contact Ball Slewing Bearing Work?

The working principle of a four point contact ball slewing bearing is based on its unique Gothic arch raceway geometry. Unlike conventional ball bearings where the ball contacts the raceway at two points, this design allows each steel ball to make contact at four points – two on the inner ring and two on the outer ring.

When loads are applied, the contact points engage as follows:

Pure axial load in one direction: Two of the four contact points become active
Reversed axial load: The opposite pair of contact points engages
Combined loads (axial + radial + tilting moment): All four contact points share the load simultaneously

This load distribution mechanism enables a single-row bearing to perform functions that would otherwise require two separate rows. The single-row four-point contact ball slewing bearing consists of two seat rings, offering a compact structure and light weight. The four-point contact between the steel ball and the arc raceway allows the bearing to bear axial force, radial force, and tilting moment at the same time. This is achieved because the Gothic arch raceway profile creates a precise contact geometry that distributes loads efficiently across the bearing.

Key Features of Four Point Contact Ball Slewing Bearings

The four point contact ball slewing bearing offers a range of distinctive engineering features:

Single-row compact design: Consists of only two seat rings (inner and outer), providing a compact structure with light weight
Four-point contact geometry: Steel balls contact the arc raceway at four points, enabling combined load handling (axial, radial, and tilting moment simultaneously)
Multiple gear options: Available as no gear, internal gear, or external gear to suit various drive configurations
Flexible ring structure: Choice between integral rings (higher rigidity) and split rings (easier adjustment)
Cage or full-ball options: Caged designs for standard applications; full-ball designs for higher load capacity with the trade-off of increased friction
High static load capacity: Engineered to withstand demanding static and dynamic conditions
Wide dimensional range: Outer diameter from 300 mm to 10,000 mm, ball diameter from 30 mm to 75 mm
High load rating: Rated load from 129 kN to 3,410 kN
Fast delivery: Standard lead time of 10–30 days for custom orders

LDB specific features:

Materials: 42CrMo and 50Mn high-grade steel
Seal type: Nitrile rubber for effective contamination protection
Hardness: Normalizing hardness 187-241 HB, quenched and tempered hardness 229-269 HB, raceway quenching hardness HRC 55-62
Inner diameter range: 100 mm to 8,000 mm
Warranty: 12 months

Main Types of Four Point Contact Ball Slewing Bearings

Four point contact ball slewing bearings can be classified based on three main criteria: gear configuration, ring structure, and ball arrangement.

1. By gear configuration:

No gear (plain): For applications where the drive system does not require gear engagement
Internal gear: Gear teeth cut on the inner ring, suitable for compact drive designs where space is limited
External gear: Gear teeth cut on the outer ring, commonly used in excavators, cranes, and turntables

2. By ring structure:

Integral ring design: Higher rigidity, suitable for heavy-duty applications requiring maximum structural integrity
Split ring design: Allows for easier adjustment and maintenance; bolts connect the two split rings before the product leaves the factory

3. By ball arrangement:

Caged design: Standard configuration with spacers or cages to reduce friction and prevent ball-to-ball contact
Full-ball design: No cage or spacer, providing higher load capacity but increased frictional resistance; friction can also easily cause scratches on the surface layer of the steel ball

Core Advantages of Four Point Contact Ball Slewing Bearings

The four point contact ball slewing bearing offers several distinct advantages over other slewing bearing types:

Combined load capability: Can simultaneously bear axial force, radial force, and tilting moment within a single row, eliminating the need for multiple bearing arrangements
Compact and lightweight: The single-row two-seat-ring design saves space and reduces overall machine weight, making it ideal for mobile equipment
Bidirectional axial load support: Handles thrust loads from both directions without additional raceways or bearings
High static load capacity: Suitable for applications with heavy shock loads and intermittent rotation patterns common in construction machinery
Design flexibility: Customizable gear type (no gear, internal gear, external gear), ring structure (integral or split), and ball arrangement (caged or full-ball) to meet specific requirements
Long service life: Optimized sealing and lubrication options extend operational life, especially in harsh environments
Cost-effective: Lower manufacturing and maintenance costs compared to double-row or cross-roller alternatives
Fast customization: 10–30 day delivery for custom orders enables rapid project execution

LDB product advantages:

This series of slewing ring is suitable for main engines requiring large axial load, high overturning moment, long service life, and continuous operation
Sealing structure and internal fixator can be optimized based on the specific working environment requirements
Both standard and non-standard models available – non-standard models designed and manufactured to customer requirements
Complete sets available without gears, with external gears, with internal gears, or individual ring gears
Secure packaging: metal bracket or export-standard fumigation-free wooden box

Common Applications of Four Point Contact Ball Slewing Bearings

Four point contact ball slewing bearings are widely used across various industries, particularly in construction machinery. Based on LDB’s application scope, common applications include:

Construction and heavy machinery:

Rotary conveyors
Welding robots and manipulators
Small and medium cranes
Excavators (turntable applications)
Aerial work platforms

Other industrial applications:

Solar tracking systems
Wind turbine yaw and pitch systems
Industrial turntables and indexing tables
Medical imaging equipment (CT scanners)
Material handling equipment
Radar and antenna rotators
Packaging machinery

The four point contact ball slewing bearing is especially suitable for applications that demand high axial load capacity, resistance to overturning moment, and continuous operation with extended service life. The single-row four-point contact ball slewing bearing is particularly well-suited for main engines with large axial load, high overturning moment, high service life requirements, and continuous operation.

How to Select the Right Four Point Contact Ball Slewing Bearing?

Selecting the correct four point contact ball slewing bearing for your application requires careful consideration of the following factors:

Selection Factor	Considerations
Load requirements	Calculate axial load, radial load, and tilting moment (kN·m). LDB’s rated load range is 129–3,410 kN.
Dimensional constraints	Verify outer diameter (300–10,000 mm), inner diameter (100–8,000 mm), and ball diameter (30–75 mm) fit your mounting space.
Gear configuration	Choose no gear, internal gear, or external gear based on your drive system design.
Ring structure	Select integral ring for higher rigidity or split ring for easier adjustment.
Ball arrangement	Choose caged design for standard applications with lower friction, or full-ball design for higher load capacity (note: full-ball design has higher friction and may cause scratches on steel ball surface).
Operating environment	Consider temperature, dust, moisture, and chemical exposure. LDB uses nitrile rubber seals as standard, with customization available for special environments.
Material and hardness	LDB offers 42CrMo and 50Mn materials with raceway quenching hardness HRC 55-62 for optimal wear resistance.
Precision requirements	Specify required tolerances for your application.
Delivery schedule	LDB standard lead time is 10–30 days for custom orders.
Warranty	LDB offers 12 months warranty on all slewing bearings.

Additional selection tips:

For large axial loads and overturning moments with continuous operation, the single-row four-point contact ball slewing bearing is highly recommended
LDB can optimize sealing structure and internal fixator design based on your specific working environment
Both standard and non-standard models are available – contact LDB for non-standard requirements
Consider the total cost of ownership, including maintenance intervals and expected service life

LDB ：Custom Four Point Contact Ball Slewing Bearings Manufacturer

LDB (Luoyang Longda) is a professional enterprise specializing in the production and sales of slewing bearings (slewing rings), slewing drives, and gear transmission devices. As a reliable supplier of high-performance rotary components, LDB serves industries ranging from construction machinery to renewable energy.

LDB four point contact ball slewing bearing specifications:

Parameter	LDB Range / Value
Brand	LDB (Luoyang Longda)
Outer diameter	300 mm – 10,000 mm
Inner diameter	100 mm – 8,000 mm
Ball diameter	30 mm – 75 mm
Rated load	129 kN – 3,410 kN
Gear type	No gear, internal gear, external gear
Delivery lead time	10 – 30 days
Material	42CrMo, 50Mn
Seal type	Nitrile rubber
Rolling element	Steel ball
Normalizing hardness	187 HB – 241 HB
Quenched and tempered hardness	229 HB – 269 HB
Raceway quenching hardness	HRC 55 – 62
Warranty	12 months
Packaging	Metal bracket or export standard fumigation-free wooden box

LDB product advantages:

Superior design: The single-row four-point contact ball slewing bearing is suitable for main engines requiring large axial load, high overturning moment, long service life, and continuous operation.
Customizable engineering: According to the requirements of the supporting working environment, LDB can optimize the design of the sealing structure and the internal fixator.
Flexible manufacturing: LDB maintains commonly used standard models, and non-standard models can be designed and manufactured according to customer requirements.
Complete solutions: LDB provides complete sets of slewing bearings without gears, with external gears, with internal gears, or individual ring gears according to customer requirements.
Secure packaging: All products are shipped in metal brackets or export-standard fumigation-free wooden boxes to ensure safe delivery.

Why choose LDB?

Experience: Years of expertise in slewing bearing design and manufacturing
Quality: High-grade materials (42CrMo, 50Mn) with precision heat treatment and raceway hardening to HRC 55-62
Customization: Full engineering support for non-standard models
Speed: 10-30 day delivery for custom orders
Warranty: 12 months on all products
Global shipping: Reliable logistics network supporting delivery worldwide

Whether you need a four point contact ball slewing bearing for an excavator turntable, a crane, a welding robot, a rotary conveyor, or any other rotary application, LDB delivers custom-engineered solutions with fast lead times and dependable quality.

Contact LDB today to discuss your specific four point contact ball slewing bearing requirements．

Slewing Bearing in Crane: The Ultimate Guide to Function, Types, and Maintenance

May 8, 2026/in Bearing Knowledge, Slewing Bearing Knowledge /by LDB Bearing

What is a Slewing Bearing in a Crane?

A slewing bearing, often referred to as a slewing ring or turntable bearing, is a large rotational rolling-element bearing specifically designed to support heavy, slow-turning, or slow-oscillating loads. In crane applications, the slewing bearing acts as the pivotal joint between the crane’s stationary undercarriage (the lower structure) and the rotating upper structure, which includes the cab, boom, and lifting mechanism.

Unlike standard bearings found in automotive wheels or small machinery, slewing bearings are engineered to handle complex forces simultaneously. These forces include three distinct load types:

Axial loads – The downward vertical weight of the crane’s upper structure and the load being lifted.
Radial loads – Horizontal forces caused by wind pressure, centrifugal motion during rotation, or side pulls.
Tilting moments – The leverage effect created when a heavy load is suspended at the end of a long boom, which tries to tip the crane over.

A typical slewing bearing consists of an inner ring, an outer ring, a set of rolling elements (steel balls or rollers), and often gear teeth integrated into one of the rings. This compact yet robust design enables the crane to rotate smoothly while supporting immense weight.

How Does a Slewing Bearing Work in a Crane?

The working principle of a slewing bearing in a crane is based on its unique raceway geometry and the arrangement of rolling elements. When the crane’s upper structure rotates, the slewing bearing allows this movement while simultaneously resisting the three types of forces described above.

In a four point contact ball slewing bearing, which is commonly used in medium-duty cranes, each steel ball contacts the raceway at four distinct points – two on the inner ring and two on the outer ring. This geometry allows the bearing to manage axial loads from either direction (upward or downward), radial loads, and tilting moments within a single, compact row of balls.

When the crane operates – for example, lifting a heavy steel beam at the end of a long boom – the slewing bearing experiences downward axial force from the weight, radial force from the boom’s extension, and a tilting moment that tries to tip the structure forward. The bearing’s internal geometry resists all three forces simultaneously, keeping the rotation smooth and the crane stable.

For larger, more demanding crane applications, double-row ball bearings or three-row roller slewing bearings are used. These designs provide additional load paths and greater structural rigidity, distributing forces across multiple rows of rolling elements and significantly increasing load capacity.

Why is the Slewing Bearing Crucial for Crane Safety and Performance?

The performance and safety of any lifting equipment rely heavily on its foundational components. The slewing bearing is absolutely essential for crane operation for three primary reasons.

Flawless 360-Degree Rotation – Efficiency on a construction site requires agility. The slewing bearing allows the crane’s boom to rotate continuously in any direction, making material handling faster and highly precise. Without a reliable slewing bearing, the crane could not position loads accurately or respond quickly to changing site conditions.

Massive Load Distribution – Cranes routinely lift thousands of kilograms. The slewing bearing acts as the load-bearing spine of the machine, distributing this massive weight evenly across the undercarriage to prevent structural failure. Proper load distribution also protects the crane’s chassis and mounting structure from localized stress concentrations.

Operational Stability – A high-quality, perfectly fitted bearing prevents wobbling and unwanted movement. It ensures the crane remains balanced during operation, significantly reducing the risk of tipping or swaying during a heavy lift. This stability is especially critical when operating at height or in windy conditions.

In short, the slewing bearing is the component that enables a crane to be both powerful and precise. Without it, the crane could not rotate safely, and the risk of mechanical failure or catastrophic tip-over would increase dramatically.

Common Types of Slewing Bearings Used in Cranes

Different crane designs and duty cycles require different load capacities. Consequently, manufacturers use a variety of slewing bearing types based on the crane’s intended workload. The three most common types are as follows.

Single-Row Four-Point Contact Ball Bearings – These bearings are ideal for light to medium-duty mobile cranes, truck-mounted cranes, and smaller tower cranes. They offer excellent cost-effectiveness and handle dynamic loads well within their rated capacity. The four-point contact geometry provides a compact solution for applications where space and weight are considerations.

Double-Row Ball Bearings – By utilizing two separate rows of steel balls with eight points of contact per ball, these bearings provide higher load capacity and greater stability than single-row designs. They are frequently used in medium-sized tower cranes, crawler cranes, and larger mobile cranes that operate at higher duty cycles.

Three-Row Roller Slewing Bearings – These bearings are designed for the absolute heaviest lifting applications. They feature three independent rows of rolling elements: one row for axial loads (upward), one row for axial loads (downward), and one row for radial loads. If you see a massive offshore crane, a heavy-duty crawler crane lifting hundreds of tons, or a large port crane, it almost certainly uses a three-row roller bearing to handle extreme axial and radial loads safely.

Each type has its place in the crane industry. The selection depends on factors such as maximum lift capacity, rotational speed, duty cycle, and cost constraints.

Top Maintenance Tips for Crane Slewing Bearings

Replacing a slewing bearing is incredibly expensive and causes massive operational downtime. To maximize the lifespan of a slewing bearing in crane operations, regular maintenance is non-negotiable. The following essential tips should be followed.

Consistent Lubrication – Friction is the primary enemy of any bearing. Apply high-quality grease to the raceways and gear teeth strictly according to the manufacturer’s recommended schedule. Insufficient lubrication leads to metal-to-metal contact, rapid wear, and eventual bearing failure. Over-lubrication can also cause seal damage, so follow the specified quantity and frequency.

Check Bolt Tension – The bolts securing the slewing ring to the crane structure experience immense and variable stress. Regularly inspect and tighten these bolts to the required torque specifications using calibrated torque tools. Loose bolts allow relative movement between the bearing and mounting structure, leading to fretting corrosion, bolt fatigue, and potential bearing misalignment.

Monitor for Wear and Tear – Pay close attention to unusual grinding noises, excessive vibrations, or jerky movements during rotation. These are early warning signs of internal bearing degradation such as spalling, pitting, or ball damage. Any change in rotational smoothness should trigger an immediate inspection.

Protect from Debris – Ensure the bearing’s protective seals remain intact and undamaged. Dirt, sand, water, and other contaminants can severely damage the internal rolling elements if they bypass the seals. In dusty construction environments or marine applications, more frequent seal inspection and cleaning are recommended.

Additionally, keep detailed maintenance records including lubrication dates, bolt torque checks, and any observed abnormalities. These records help predict bearing life and schedule replacement before a catastrophic failure occurs.

Selecting the Right Slewing Bearing for Your Crane

Choosing the correct slewing bearing for a crane application requires careful evaluation of multiple factors. Engineers should consider the following key parameters before making a selection.

Load Requirements – Calculate the maximum axial load, radial load, and tilting moment (in kN·m) that the bearing will experience under normal and peak operating conditions. These values determine the required bearing size, type, and internal geometry.

Rotational Speed – While crane slewing bearings typically operate at slow speeds (often less than 2-3 revolutions per minute), the number of rotations per day or year affects fatigue life calculations. High-cycle applications such as port cranes require different design considerations than occasional-use mobile cranes.

Installation Space and Mounting Dimensions – The available space for the bearing determines maximum outer diameter, minimum inner diameter, and bolt circle diameter. The mounting structure’s flatness and stiffness must also be evaluated to ensure proper load distribution.

Precision and Rigidity Requirements – Some crane applications, such as those requiring precise load positioning or robotic control, demand higher rotational accuracy and greater structural rigidity. This influences the choice between ball bearings and roller bearings, as well as the internal clearance specifications.

Environmental Conditions – Temperature extremes, dust, humidity, and saltwater exposure all affect material selection, sealing systems, and corrosion protection requirements. Outdoor cranes in coastal areas benefit from anti-corrosion coatings and upgraded seals.

LDB: A Trusted Supplier of Custom Crane Slewing Bearings

LDB (Luoyang Longda) is a professional manufacturer specializing in the production and sales of high-quality slewing bearings, slewing drives, and gear transmission devices. With years of experience in the industry, LDB serves crane manufacturers and operators worldwide, providing custom-engineered solutions for mobile cranes, tower cranes, crawler cranes, and offshore cranes.

LDB’s crane slewing bearings are manufactured using premium materials including 42CrMo, 50Mn, and C45, with rolling elements made from GCr15 bearing steel. Raceways are induction-hardened to HRC 55-62, providing excellent wear resistance and long operational life even under heavy cyclic loading. Outer diameters range from 300 mm to 10,000 mm, accommodating everything from small truck-mounted cranes to massive port cranes.

For crane applications, LDB offers flexible customization options including:

Gear configurations: no gear, internal gear, or external gear
Ring materials: 42CrMo, 50Mn, C45 based on strength and cost requirements
Cage materials: steel 20 or ZL112 cast aluminum alloy
Spacer materials: nylon 6 or nylon 66
Sealing systems: standard nitrile rubber or custom designs for harsh environments

LDB offers a standard lead time of 30 days for custom orders. All products undergo rigorous inspection and testing before shipment, including dimensional accuracy checks, rotational torque testing, and raceway hardness verification. Finished bearings are protected with anti-corrosion oil and packaged in metal brackets or export-standard fumigation-free wooden boxes.

Whether you need a single-row four-point contact bearing for a mobile crane, a double-row ball bearing for a tower crane, or a three-row roller bearing for a heavy-lift crawler crane, LDB provides reliable, custom-engineered solutions backed by engineering support and a 12-month warranty.

FAQ About Slewing Bearings in Cranes

Q1: How often should the slewing bearing on a crane be lubricated?

Lubrication frequency depends on crane usage and operating conditions. For cranes in daily construction use, lubrication is typically recommended every 150-200 operating hours or weekly. For cranes used intermittently, lubrication every month is usually sufficient. Always follow the manufacturer’s specifications for grease type and quantity. Heavy-duty or high-cycle applications may require more frequent lubrication.

Q2: What are the signs that a crane slewing bearing is failing?

Common warning signs include grinding or clicking noises during rotation, excessive vibration or wobbling, jerky or uneven rotational movement, increased resistance when slewing, and visible rust or pitting around seals. If any of these symptoms appear, the bearing should be inspected immediately by qualified personnel. Continued operation with a failing bearing risks sudden failure and potential crane tip-over.

Q3: How long does a slewing bearing last in a typical crane?

With proper installation, regular maintenance, and operation within rated load limits, a crane slewing bearing can last 10 to 15 years or more. Factors that reduce service life include inadequate lubrication, overloading, contamination ingress, and improper bolt torque. Cranes in harsh environments or with very high duty cycles may require replacement sooner.

Q4: Can a crane slewing bearing be repaired instead of replaced?

Minor damage such as localized surface pitting may be repairable through re-grinding raceways or replacing rolling elements. However, significant damage to raceways, gear teeth, or ring structural integrity typically requires full replacement. An experienced manufacturer can assess the bearing condition and recommend the most cost-effective solution. For critical crane applications, replacement is often the safer and more reliable option.

Q5: What is the typical lead time for a custom crane slewing bearing from LDB?

LDB offers a standard lead time of 30 days for custom crane slewing bearings. This includes material selection, precision machining, heat treatment, assembly, and final inspection. For non-custom, standard-size bearings, shorter lead times may be available. Clients should consult LDB’s engineering team for specific project timelines.

Q6: What materials are best for crane slewing bearings operating in coastal environments?

For coastal or offshore crane applications, materials with good corrosion resistance are essential. LDB offers ring materials such as 42CrMo with specialized anti-corrosion coatings. Sealing systems should be upgraded to prevent saltwater ingress. Regular cleaning and more frequent lubrication inspections are also recommended for coastal operations.

Delivery of Caterpillar Excavator Slewing Ring to Europe

May 7, 2026/in LDB Company News /by LDB Bearing

In the field of construction machinery, the quality and timely delivery of slewing rings directly affect the stable operation of host equipment. In February 2025, our company successfully completed a supply task for a CAT excavator slewing ring to a client in Europe. This case demonstrates our supply chain capability and professional understanding of the Four-Point Contact Ball Slewing Bearing.

The slewing ring supplied in this project is of the four-point contact ball type. This bearing features a single raceway design where each ball contacts the raceway at four distinct points, allowing it to simultaneously withstand axial loads, radial loads, and tilting moments. Compared to other designs, the four-point contact ball bearing offers higher load efficiency, a compact cross-section, and good impact resistance, making it particularly suitable for excavators that require frequent slewing and heavy-duty operation.

The client in this case was based in Europe and explicitly requested a four-point contact ball slewing bearing for their CAT excavator. After order confirmation, our company strictly controlled every stage of production, inspection, and packaging. The slewing rings were shipped in February 2025 via a dedicated Europe logistics route. Each unit underwent dimensional accuracy, rotational flexibility, hardness, and flaw detection tests to confirm compliance with CAT standards. Anti-corrosion treatment and reinforced packaging were applied for long-distance transportation.

Upon arrival in Europe, the slewing rings were installed and tested. The customer reported excellent performance in actual excavator operations, including low friction, high rigidity, and stable rotational accuracy, effectively reducing slewing noise and vibration. This case once again proves our company’s professional capability in critical components for construction machinery, from product selection and quality control to international logistics.

What is a Four Point Contact Ball Slewing Bearing?

A four point contact ball slewing bearing is a precision rotary component primarily composed of an inner ring, an outer ring, a single row of steel balls, a cage (or spacer), and sealing devices. Both the inner and outer rings can be manufactured as either integral or split structures. Integral rings offer higher rigidity, while split rings allow for easier adjustment; for split structures, bolts are used to connect the two halves before the product leaves the factory.

This type of slewing bearing generally includes a cage or spacer to separate the balls. However, a full-ball (cageless) structure is used when load requirements are relatively high. The full-ball design provides larger load capacity but comes with higher frictional resistance, which can potentially cause scratches on the surface layer of the steel balls.

The basic structure is available in three gear configurations: without gear, with external gear, or with internal gear. All configurations offer high static load capacity. As a product of LDB (Luoyang Longda), this bearing type is manufactured using materials including 42CrMo and 50Mn, with nitrile rubber seals provided as standard.

How Does a Four Point Contact Ball Slewing Bearing Work?

The working principle is based on the Gothic arch raceway geometry.

Contact points:

Conventional bearings: ball contacts raceway at 2 points
Four point contact bearing: ball contacts raceway at 4 points (2 on inner ring, 2 on outer ring)

Load engagement:

Pure axial load in one direction → 2 of 4 contact points become active
Reversed axial load → opposite pair of contact points engages
Combined loads (axial + radial + tilting moment) → all 4 contact points share the load simultaneously

Key outcomes:

A single-row bearing performs functions that would otherwise require two separate rows
Consists of two seat rings (inner and outer)
Compact structure and light weight
Gothic arch raceway profile creates precise contact geometry for efficient load distribution

Key Features of Four Point Contact Ball Slewing Bearings

Design features:

Single-row compact design – only two seat rings, light weight
Four-point contact geometry – enables combined load handling (axial, radial, and tilting moment simultaneously)

Configuration options:

Gear options: no gear, internal gear, or external gear
Ring structure: integral (higher rigidity) or split (easier adjustment)
Ball arrangement: caged (standard) or full-ball (higher load capacity, higher friction)

Performance specifications:

High static load capacity
Outer diameter range: 300 mm – 10,000 mm
Ball diameter range: 30 mm – 75 mm
Rated load range: 129 kN – 3,410 kN
Fast delivery: 10–30 days for custom orders

LDB specific features:

Materials: 42CrMo and 50Mn
Seal type: Nitrile rubber
Hardness:
- Normalizing: 187-241 HB
- Quenched and tempered: 229-269 HB
- Raceway quenching: HRC 55-62
Inner diameter range: 100 mm – 8,000 mm
Warranty: 12 months

Main Types of Four Point Contact Ball Slewing Bearings

1. By gear configuration:

No gear (plain) – for applications without gear engagement
Internal gear – teeth on inner ring, suitable for compact drive designs
External gear – teeth on outer ring, common in excavators, cranes, and turntables

2. By ring structure:

Integral ring design – higher rigidity, for heavy-duty applications
Split ring design – easier adjustment and maintenance; bolted together before shipment

3. By ball arrangement:

Caged design – standard, with spacers or cages to reduce friction and prevent ball-to-ball contact
Full-ball design – no cage or spacer; higher load capacity but increased friction and potential for scratches on steel ball surfaces

Core Advantages of Four Point Contact Ball Slewing Bearings

Performance advantages:

Combined load capability – bears axial, radial, and tilting moment forces in a single row
Bidirectional axial load support – no additional raceways required
High static load capacity – ideal for heavy shock loads and intermittent rotation

Design advantages:

Compact and lightweight – saves space, reduces overall machine weight
Design flexibility – customizable gear type, ring structure, and ball arrangement
Cost-effective – lower manufacturing and maintenance costs than double-row or cross-roller alternatives

Operational advantages:

Long service life – optimized sealing and lubrication for harsh environments
Fast customization – 10–30 day delivery for custom orders

LDB product advantages:

Suitable for main engines requiring large axial load, high overturning moment, long service life, and continuous operation
Sealing structure and internal fixator can be optimized based on working environment
Both standard and non-standard models available
Complete sets available (without gears, with external gears, with internal gears, or individual ring gears)
Secure packaging: metal bracket or export-standard fumigation-free wooden box

Common Applications of Four Point Contact Ball Slewing Bearings

Construction and heavy machinery:

Rotary conveyors
Welding robots and manipulators
Small and medium cranes
Excavators (turntable applications)
Aerial work platforms

Other industrial applications:

Solar tracking systems
Wind turbine yaw and pitch systems
Industrial turntables and indexing tables
Medical imaging equipment (CT scanners)
Material handling equipment
Radar and antenna rotators
Packaging machinery

Best suited for:

Applications demanding high axial load capacity
Resistance to overturning moment
Continuous operation with extended service life

How to Select the Right Four Point Contact Ball Slewing Bearing?

Key selection factors:

Factor	Considerations
Load requirements	Axial, radial, and tilting moment (kN·m); LDB range: 129–3,410 kN
Dimensional constraints	Outer diameter (300–10,000 mm), inner diameter (100–8,000 mm), ball diameter (30–75 mm)
Gear configuration	No gear, internal gear, or external gear based on drive system
Ring structure	Integral (higher rigidity) or split (easier adjustment)
Ball arrangement	Caged (lower friction) or full-ball (higher load capacity, but higher friction and scratch risk)
Operating environment	Temperature, dust, moisture, chemicals; LDB uses nitrile rubber seals (customization available)
Material and hardness	42CrMo and 50Mn; raceway quenching hardness HRC 55-62
Precision requirements	Specify required tolerances
Delivery schedule	LDB standard: 10–30 days for custom orders
Warranty	LDB offers 12 months

Additional selection tips:

For large axial loads and overturning moments with continuous operation → single-row four-point contact ball slewing bearing is highly recommended
LDB can optimize sealing structure and internal fixator design based on your working environment
Non-standard models available upon request
Consider total cost of ownership (maintenance intervals + expected service life)

LDB ：Custom Four Point Contact Ball Slewing Bearings Manufacturer

Company profile:
LDB (Luoyang Longda) is a professional enterprise specializing in the production and sales of slewing bearings (slewing rings), slewing drives, and gear transmission devices, serving industries from construction machinery to renewable energy.

Product specifications:

Parameter	LDB Range / Value
Brand	LDB (Luoyang Longda)
Outer diameter	300 mm – 10,000 mm
Inner diameter	100 mm – 8,000 mm
Ball diameter	30 mm – 75 mm
Rated load	129 kN – 3,410 kN
Gear type	No gear, internal gear, external gear
Delivery lead time	10 – 30 days
Material	42CrMo, 50Mn
Seal type	Nitrile rubber
Rolling element	Steel ball
Normalizing hardness	187 HB – 241 HB
Quenched and tempered hardness	229 HB – 269 HB
Raceway quenching hardness	HRC 55 – 62
Warranty	12 months
Packaging	Metal bracket or export-standard fumigation-free wooden box

LDB product advantages:

Suitable for main engines requiring large axial load, high overturning moment, long service life, and continuous operation
Customizable sealing structure and internal fixator based on working environment
Standard and non-standard models available
Complete solutions (without gears, with external gears, with internal gears, or individual ring gears)
Secure packaging for safe delivery

Why choose LDB?

Experience: Years of expertise in slewing bearing design and manufacturing
Quality: High-grade materials (42CrMo, 50Mn) with precision heat treatment and raceway hardening to HRC 55-62
Customization: Full engineering support for non-standard models
Speed: 10-30 day delivery for custom orders
Warranty: 12 months on all products
Global shipping: Reliable logistics network worldwide

Contact:
Whether you need a four point contact ball slewing bearing for an excavator turntable, crane, welding robot, rotary conveyor, or any other rotary application, LDB delivers custom-engineered solutions with fast lead times and dependable quality. Contact LDB today to discuss your specific requirements.