Understanding RB, RE, and RU Series Crossed Roller Bearings

What Are Crossed Roller Bearings?

Crossed roller bearings are high-precision bearings designed with cylindrical rollers arranged alternately at 90° angles in a V-shaped raceway. Unlike conventional bearings that require multiple components to handle different load directions, a single crossed roller bearing can simultaneously support radial loads, axial loads, and overturning moments. The rollers are separated by spacers or retainers, preventing roller-to-roller contact and reducing friction while maintaining proper orientation.

This orthogonal arrangement delivers two core benefits: exceptional structural rigidity—often three to four times that of conventional bearing combinations—and a compact profile that minimizes both axial cross-section and radial mounting space. These characteristics make crossed roller bearings optimal for applications such as industrial robot joints, CNC rotary tables, manipulator swiveling units, medical equipment, measuring instruments, and semiconductor manufacturing machines.

Understanding the BRB (RB) Series with Separable Outer Ring

The BRB (RB) Series is the basic model of crossed roller bearings. It features a separable outer ring (split into two halves) and an integrated inner ring (solid, continuous piece). This design is specifically optimized for applications where high rotational accuracy of the inner ring is required.

The separable outer ring allows for easier assembly around the shaft, as the two halves can be positioned and secured during installation. The inner ring, being solid, provides a stable mounting surface for rotating components. For equivalent dimensions, the BRB series offers a balance of load capacity and compactness, making it a versatile choice for precision rotary applications.

Applications of the BRB (RB) Series:
This series is commonly used in machine tool index table swiveling units, CNC rotary tables (where the table rotates while the housing remains fixed), manipulator joints, robotic wrists, and precision measuring instruments. Its ability to provide high inner-ring rotational accuracy makes it particularly suitable for applications requiring precise positioning of a rotating shaft or table.

Understanding the BRE (RE) Series with Separable Inner Ring

The BRE (RE) Series shares the same major dimensions as the BRB series but features the opposite structural arrangement: a separable inner ring (split into two halves) and an integrated outer ring (solid, continuous piece).

This configuration is specifically designed for applications requiring high rotational accuracy of the outer ring. The solid outer ring provides a stable mounting surface for rotating housings, while the separable inner ring allows for assembly around shafts where pre-assembled clamping is needed.

Applications of the BRE (RE) Series:
This series is commonly used in rotating platforms where the outer ring rotates, such as direct drive motor rotors, rotary indexing systems, turntable bearings, and certain types of robotic turn tables. It is also found in medical imaging equipment (CT scanner gantries) and semiconductor manufacturing tools where the outer housing needs to rotate with high precision while the inner shaft remains stationary.

Understanding the BRU (RU) Series with Integrated Rings

The BRU (RU) Series features both inner and outer rings as solid, integrated structures with pre-drilled mounting holes on both rings. Because the mounting holes are provided, this model does not require a presser flange or specialized housing for installation.

The integrated ring design offers several distinct advantages:

• • Simplified Installation: No auxiliary clamping flanges or housing retainers are needed—the bearing can be bolted directly onto the machine structure.

• • Stable Performance: Since both rings are non-separable, installation has minimal impact on internal clearance and preload, ensuring consistent rotational accuracy and torque.

• • Versatile Mounting: This model can be used for both inner-ring rotation and outer-ring rotation.

Applications of the BRU (RU) Series:
This series is particularly suitable for applications requiring easy installation, stable performance, and high rigidity. Typical uses include large robotic bases and waist rotation units, heavy-duty CNC rotary tables, direct drive motor systems, industrial automation turntables, and precision assembly equipment. The pre-drilled mounting holes on both rings make it the preferred choice for modular machine designs and applications where installation space is limited.

Key Differences Between BRB, BRE, and BRU Series

Feature	BRB (RB) Series	BRE (RE) Series	BRU (RU) Series
Structure	Separable outer ring, integrated inner ring	Separable inner ring, integrated outer ring	Both rings integrated (non-separable)
Primary Rotation	Inner ring rotation	Outer ring rotation	Both inner and outer ring rotation
Mounting	Requires housing or flange for outer ring	Requires housing or flange for inner ring	Pre-drilled mounting holes, no housing required
Installation Complexity	Moderate—split outer ring requires alignment	Moderate—split inner ring requires alignment	Simple—direct bolt-on installation
Typical Application	CNC index tables, machine tool rotary tables, manipulator joints, precision measuring instruments	Direct drive motor rotors, rotary indexing systems, turntable bearings, medical CT gantries	Large robotic bases, heavy-duty CNC tables, industrial turntables, modular automation equipment
Precision Grades	P5, P4, P2	P5, P4, P2	P5, P4, P2

How to Select the Right Crossed Roller Bearing Series

Selecting the appropriate series requires evaluating your application across three primary criteria:

1. Which Ring Rotates?

If the inner ring rotates and the outer ring is fixed, the BRB (RB) Series is the standard choice. If the outer ring rotates and the inner ring is fixed, the BRE (RE) Series is more appropriate. If both rings may rotate or you need the simplest installation, the BRU (RU) Series is recommended.

2. Installation Constraints

For applications where a presser flange or complex housing is impractical, the BRU (RU) Series offers the easiest installation due to pre-drilled mounting holes on both rings. For designs where the housing or shaft is integrated into the machine structure, the BRB or BRE series may be more appropriate.

3. Space and Precision Requirements

All three series are available in P5, P4, and P2 precision grades. For applications requiring ultra-compact dimensions, the BRB series offers a slim profile. For maximum stability and consistent performance under variable loads, the BRU series provides the most robust solution.

BY Bearings: A Trusted Crossed Roller Bearing Supplier

BY Bearings (Luoyang Boying Bearing Co., Ltd.) specializes in the manufacturing of high-precision crossed roller bearings and rotary table bearings for CNC machine tools, robotics, and industrial automation systems. The company offers comprehensive bearing solutions across all three series—BRB (RB), BRE (RE), and BRU (RU)—with precision grades up to P2 and strict ISO 9001 quality control.

With over 16 years of industry experience, BY Bearings has established itself as a reliable partner for manufacturers requiring precision bearing solutions. Every bearing is manufactured using high-quality bearing steel, precision grinding processes, and rigorous quality inspection procedures to ensure stable performance and consistent accuracy.

BY Bearings offers a comprehensive portfolio of precision crossed roller bearings, ranging from the core BRB (RB), BRE (RE), and BRU (RU) series to specialized designs for unique application requirements. Whether you need ultra-slim profiles (BRA), integral ring constructions (BX, BBH), exceptional rigidity (BBS), or large-scale system solutions (BSU), BY Bearings provides tailored solutions across nine distinct series—all available in precision grades up to P2 with strict ISO 9001 quality control.

BY Bearings also offers custom dimension tailoring, specialized preload options, sealing configurations, and lubrication solutions based on equipment structure, load requirements, and installation space. With exports to over 100 countries, the company delivers reliable solutions for both OEM and aftermarket needs across robotics, CNC machining, medical equipment, and precision instrumentation.

Need help selecting the right crossed roller bearing series for your application? Contact BY Bearings today for technical consultation and find the optimal bearing solution for your specific requirements.

FAQs About Crossed Roller Bearing Series

Q1: What is the main difference between BRB (RB) and BRE (RE) series?
The BRB (RB) series has a separable outer ring with an integrated inner ring, optimized for inner ring rotation. The BRE (RE) series has a separable inner ring with an integrated outer ring, optimized for outer ring rotation.

Q2: Which crossed roller bearing series is easiest to install?
The BRU (RU) series is easiest to install because both rings have pre-drilled mounting holes and are integrated (non-separable), eliminating the need for a presser flange or specialized housing.

Q3: Can the BRU (RU) series be used for both inner-ring and outer-ring rotation?
Yes. The BRU (RU) series supports both inner-ring and outer-ring rotation due to its integrated ring design and mounting holes on both rings.

Q4: What precision grades are available for these crossed roller bearing series?
All three series—BRB (RB), BRE (RE), and BRU (RU)—are available in P5, P4, and P2 precision grades, with P2 offering the highest level of accuracy.

Q5: What crossed roller bearing series does BY Bearings offer?
BY Bearings manufactures nine series of precision crossed roller bearings: BRB (RB), BRE (RE), BRU (RU), BRA, BSU, BX, BBH, and BBS. The first three are the core models, while the remaining series address specialized needs such as ultra-slim designs, integral ring constructions, and high-rigidity configurations. All series are available in precision grades up to P2 under ISO 9001 quality control.