How to choose a slewing bearing

This article provides a comprehensive guide on how to select the right slewing bearing for your application. It explains the structure and types of slewing bearings, evaluates critical factors such as load, speed, and environmental conditions, and offers a step-by-step selection process. It also highlights supplier considerations, material specifications, and engineering practices to help engineers, procurement teams, and equipment manufacturers make informed decisions.

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How Do I Choose a Slewing Bearing?

Slewing bearings—also known as slew bearings or slewing ring bearings—are essential components that enable rotational movement while supporting axial, radial, and moment loads simultaneously. They are widely used in heavy machinery, wind turbines, cranes, robotics, and precision equipment that require reliable 360° rotation.

This guide walks you through understanding slewing rings, their components, types, applications, and the key technical and commercial factors to consider when selecting the right slewing bearing.

What Is a Slewing Bearing?

A slewing bearing is a large-size bearing designed to support and transmit combined loads while allowing smooth rotational movement. Unlike standard bearings, slewing rings can handle very high load capacities, making them indispensable in large-scale industrial applications.

Components of a Slewing Bearing

  • Inner and Outer Rings – Provide structural integrity.

  • Rolling Elements (Balls or Rollers) – Enable rotation and distribute loads.

  • Spacers or Cages – Maintain uniform separation of rolling elements.

  • Seals – Protect the bearing from dust, dirt, and moisture.

  • Mounting Holes – Facilitate installation on machinery.

  • Lubrication Systems – Ensure smooth operation and easy maintenance.

  • Optional Features – Integrated gears or surface coatings for specific applications.

Types of Slewing Bearings

Different slewing ring designs support varying performance needs:

Type Description
Four-Point Contact Ball Slewing Ring Bearing Handles axial, radial, and moment loads.
Eight-Point Contact Ball Slewing Ring Bearing Enhanced load distribution for heavy-duty machinery.
Cross Roller Slewing Ring Bearing Provides high precision under all load types.
Three-Row Roller Slewing Bearing Offers the highest load capacity by separating load directions.
Thrust Ball Slewing Rings Designed for heavy axial loads.
Combination Slewing Rings Mix ball and roller elements for balanced performance.
RealiSlim TT Turntable Bearings Compact design for limited space applications.
Mating Pinions Provide powered rotation when integrated with gears.

Applications of Slewing Bearings

Slewing bearings are indispensable in industries such as:

  • Cranes & Construction Equipment

  • Wind Turbines

  • Medical Devices (CT scanners, surgical equipment)

  • Robotics & Automation

  • Transport Vehicles

  • Heavy Industrial Machinery

Key Factors for Selecting a Slewing Bearing

  1. Load Conditions

    • Axial Load – Vertical forces acting along the axis.

    • Radial Load – Horizontal forces perpendicular to the axis.

    • Moment Load – Tilting forces that cause bending.
      Accurate load calculation is essential to avoid early bearing failure.

  2. Material & Heat Treatment

    • High-grade steels (e.g., 42CrMo4, 50Mn) increase strength and durability.

    • Heat treatment improves hardness and wear resistance.

  3. Rotational Speed

    • Bearings must support the required speed without vibration or premature wear.

  4. Precision Requirements

    • For robotics and medical devices, high positioning accuracy and repeatability are critical.

  5. Environmental Conditions

    • Consider exposure to dust, moisture, temperature extremes, or corrosive environments.

    • Use proper seals and coatings for extended service life.

  6. Cost and Total Lifecycle Value

    • Balance initial cost with long-term reliability, maintenance, and replacement costs.

  7. Supplier Reliability

    • Select a manufacturer with strong engineering support, strict quality control, and customization capabilities.

Step-by-Step Guide to Choosing the Right Slewing Bearing

  1. Identify Equipment Requirements – Define load, speed, precision, environment, and service life.

  2. Calculate Maximum Loads – Consider both static and dynamic loads.

  3. Apply Service Factors – Adjust for usage frequency, shock, and impact loads.

  4. Evaluate Gear Requirements – If using geared slewing rings, verify gear strength and standards (AGMA/ISO).

  5. Select Mounting Arrangement – Ensure stability, easy assembly, and maintenance.

  6. Compare Bearing Styles – Match load ratings with series (RK, MT, XR, TR, etc.).

  7. Check Gear Size & Quality – Verify tooth design, hardness, and backlash control.

  8. Perform Preliminary Selection – Compare load curves with calculated service conditions.

  9. Finalize Selection – Confirm the design meets all operational requirements before ordering.

Material and Manufacturing Excellence at Bearing Maker

  • Rings – Typically made of 42CrMo4 or 50Mn, with high tensile strength and hardness.

  • Rolling Elements – Commonly use 100Cr6 / GCr15 steel with excellent fatigue resistance.

  • Heat Treatment – Selective hardening achieves hardness HRc 50–60 for wear resistance.

  • Quality Control – Bearings undergo strict assembly, load, and durability testing.

  • Lubrication Recommendation – Lithium ester grease for reliable performance across -20°C to 120°C.

Conclusion

Choosing the right slewing bearing is a critical step in ensuring the performance, safety, and longevity of your machinery. By carefully evaluating load, speed, precision, environmental conditions, and supplier quality, you can select a slewing ring that meets your specific application needs.

For tailored engineering support and high-performance slewing bearings, contact bearing maker for expert consultation.

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