The RU85 cross roller bearing is a reliable 55 × 120 × 15 mm precision bearing with integrated inner and outer rings and mounting holes on both rings. Its crossed cylindrical rollers support radial loads, bidirectional axial loads and overturning moments within one compact unit.
With a dynamic radial load rating of 20.3 kN and static radial load rating of 29.5 kN, the RU85 cross roller bearing is suitable for robot joints, CNC rotary tables, semiconductor equipment, medical systems and precision positioning mechanisms.
LYDL supplies open RU85 and double-sealed RU85UU versions. P5, P4 and P2 accuracy, controlled clearance or preload, special grease, laser marking and inspection reports are available according to project requirements.
RU85 Cross Roller Bearing Overview
RU85 cross roller bearing is a compact, mounting-holed precision bearing with a 55 mm bore, 120 mm outside diameter and 15 mm width. It belongs to the RU series crossed roller bearings and uses integrated inner and outer rings for stable installation and high structural rigidity.
Cylindrical rollers are arranged alternately at 90 degrees inside the bearing. This configuration allows RU85 to carry radial loads, axial loads in both directions and overturning moments simultaneously. Mounting holes on both rings allow the bearing to be bolted directly to properly prepared mating structures, reducing the number of separate bearing seats or clamping components required.
RU85 is especially suitable for equipment that needs a medium-size through bore, compact axial height and reliable positioning under combined loads.
Key Advantages
Integrated inner and outer rings for improved mounting stability
Direct mounting holes on both rings
High rigidity within a 15 mm axial width
Supports radial, bidirectional axial and moment loads
Suitable for inner-ring or outer-ring rotation
Open, sealed, preload and high-precision options available
RU85 Technical Specifications
Parameter
RU85 Specification
Bearing type
Mounting-holed cross roller bearing
Ring structure
Integrated inner and outer rings
Bore diameter, d
55 mm
Outside diameter, D
120 mm
Width, B
15 mm
Roller pitch circle diameter, dp
85 mm
Minimum chamfer, r min.
0.6 mm
Greasing-hole diameter, d1
3.1 mm
Reference shoulder diameter, ds max.
79 mm
Reference housing shoulder diameter, Dh min.
93 mm
Inner-ring mounting PCD
65 mm
Inner-ring mounting holes
8 × M5 through
Outer-ring mounting PCD
105 mm
Outer-ring mounting holes
8 × Ø5.5 mm through
Outer-ring counterbore
Ø9.5 mm, depth 5.4 mm
Basic dynamic radial load rating, C
20.3 kN
Basic static radial load rating, C₀
29.5 kN
Approximate mass
1.0 kg
Standard ring and roller material
GCr15 / 100Cr6 bearing steel
Available accuracy grades
P5, P4 and P2
Main load directions
Radial, bidirectional axial and moment
The load ratings above are catalog reference values in the radial direction. Bearing life under combined radial, axial and moment loading should be checked against the actual load cycle, speed, duty ratio, lubrication and mounting rigidity.LYDL RU85 integrated cross roller bearing with a 55 mm bore and 120 mm outside diameter.
Integrated Structure and Mounting Design
Unlike crossed roller bearings with a split inner or outer ring, RU85 uses integrated rings with pre-machined mounting holes. This makes the bearing less sensitive to assembly-induced ring separation and helps maintain stable rotational accuracy after installation.
The 55 mm center opening provides space for shafts, cables, air lines or compact drive components. The 15 mm width helps reduce the axial length of robot joints and precision rotary modules.
Direct mounting simplifies the surrounding structure, but the bearing still requires rigid, flat and accurately machined mating surfaces. Insufficient mounting rigidity or uneven bolt tightening can reduce rotational accuracy and create localized raceway loading.
For an overview of alternative constructions, visit the complete cross roller bearing range.
RU85 Models, Seals, Clearance and Accuracy Options
RU85 variations should be selected according to contamination level, rotational torque, positioning accuracy and operating environment.
Clean equipment or systems using external protection
RU85UU
Sealed on both sides
Robot joints and equipment exposed to dust or grease leakage risk
C0 clearance
Positive internal radial clearance
Applications prioritizing low starting torque
CC0 preload
Controlled negative clearance or preload
Applications prioritizing rigidity and positioning stability
P5
Precision grade
General precision automation
P4
High-precision grade
Robot joints, rotary tables and inspection equipment
P2
Ultra-high-precision grade
Metrology, optical and highly accurate positioning systems
Special grease
Lubricant selected by speed, temperature or environment
Vacuum, low-temperature, cleanroom or low-torque applications
Custom marking/report
Customer model, serial number or inspection documentation
OEM projects and traceability requirements
A typical inquiry may be written as: RU85UU / P4 / CC0 / specified grease Suffix order and clearance definitions can vary between manufacturers. The approved LYDL drawing and purchase specification should therefore control the final configuration. Special lubrication, corrosion protection or low-torque requirements should be stated separately instead of relying only on a suffix.
RU85 Interchange and Cross-Reference Guidance
RU85 is commonly reviewed against the following mounting-holed crossed roller bearing references:
These references indicate a similar 55 × 120 × 15 mm envelope and mounting-hole arrangement, but they do not guarantee automatic interchangeability.
Before replacement, verify:
Bore, outside diameter and width
Inner- and outer-ring mounting-hole patterns
Counterbore dimensions
Seal configuration
Accuracy grade and permitted runout
Radial clearance or preload
Starting and running torque
Load ratings and lubricant
Shoulder dimensions and mounting interface
THK and IKO are trademarks of their respective owners. They are mentioned only for product identification and dimensional comparison. LYDL is an independent bearing manufacturer and is not affiliated with or endorsed by these companies.
Where RU85 Is Typically Used
The balance between a 55 mm bore, 15 mm width and direct bolt mounting makes RU85 useful in medium-size precision rotary mechanisms.
Industrial Robotics
RU85 can support radial, axial and moment loads in robot wrists, rotary joints, end-effectors and compact servo actuators. The center opening can accommodate cables or transmission components.
CNC Rotary and Indexing Tables
Its integrated structure and controlled preload help maintain rigidity during indexing, positioning and light machining operations. Mounting accuracy and bolt preload should be verified after assembly.
Semiconductor and Inspection Equipment
RU85 is suitable for wafer-handling modules, optical inspection stages and precision rotary platforms that require smooth movement and limited deflection.
Medical and Laboratory Systems
The bearing can be used in compact imaging mechanisms, sample-handling systems and laboratory automation where installation space and repeatable positioning are important.
Choosing Between RU66, RU85 and RU124
RU85 occupies the middle position between two frequently selected RU models:
Choose the RU66 cross roller bearing when a 35 mm bore and smaller 95 mm outside diameter are sufficient.
Choose RU85 when the design requires a 55 mm bore, 120 mm outside diameter and moderate combined-load capacity.
Choose the RU124 cross roller bearing when an 80 mm bore, higher load capacity or a larger mounting interface is required.
Final selection should not be based on dimensions alone. Calculate the equivalent bearing load and service life using the actual radial load, axial load, overturning moment, speed and operating cycle. The cross roller bearing selection guide provides additional information about structures, loads and model selection.
RU85 Installation Recommendations
Clean the bearing and both mounting surfaces before assembly. Remove burrs, dust, metal particles and dried anti-rust oil where necessary.
Confirm the mounting-hole pattern, shoulder dimensions and available bolt depth against the approved drawing.
Place the bearing onto the mounting surface without hammering or applying impact through the rollers.
Install the bolts loosely, then tighten them gradually in a diagonal sequence.
Apply the specified final tightening torque using a calibrated torque wrench.
Rotate the bearing during staged tightening and check for abnormal resistance.
Measure axial and radial runout after installation. Compare the result with the application requirement rather than relying only on the bearing accuracy grade.
Confirm running torque, lubrication and sealing before operating the equipment at full speed or load.
The mounting surface, housing rigidity, drive alignment and bolt tightening procedure can all affect the final rotational accuracy. A P2 or P4 bearing cannot compensate for an uneven or flexible installation interface.
LYDL Inspection and Export Packaging
LYDL can inspect RU85 according to the selected accuracy, preload and documentation requirements. Available inspection items include:
Bore, outside diameter and width
Mounting-hole diameter, position and PCD
Ring roundness and raceway geometry
Material hardness
Radial clearance or preload
Starting and running torque
Radial and axial runout
Rotation smoothness, noise and appearance
Model marking and serial-number verification
Inspection reports, material certificates and traceability records can be supplied when specified before production.
After inspection, the bearing is protected with suitable anti-rust treatment and packed in a sealed or vacuum bag. Shock-resistant material, an individual carton and an export plywood case can be used according to order quantity and transportation method.
Why Source RU85 From LYDL?
LYDL manufactures precision cross roller bearings in Luoyang, China. Production and quality-control capabilities cover precision machining, raceway grinding, superfinishing, component sorting, cleaning, assembly, preload control and final inspection.
Customers can specify:
P5, P4 or P2 accuracy
Open or double-sealed construction
Clearance or preload level
Standard or application-specific grease
Running-torque requirements
Customer marking and private labels
Material and dimensional inspection reports
Individual, batch or reinforced export packaging
RU85 Frequently Asked Questions
Is RU85 suitable for a robot joint with a 55 mm center passage?
Yes. RU85 has a 55 mm bore and mounting holes on both rings, making it suitable for robot joints where cables, shafts or drive components must pass through the center. Load, torque, speed and mounting rigidity still need to be checked.
Should I select RU85 or RU85UU?
Select open RU85 for clean equipment with external contamination protection. RU85UU has seals on both sides and is generally preferred when dust protection and grease retention are important. Seals may slightly increase rotational resistance.
Can RU85 be installed without a separate bearing housing?
Its integrated rings and mounting holes allow direct bolting to accurately machined supporting components, which can reduce separate housing or flange parts. Both mounting faces must still provide sufficient flatness, rigidity and support.
Is preload always better for RU85?
No. Preload can improve rigidity and positioning stability, but excessive preload increases rotational torque and heat generation. Low-torque systems may require positive clearance or carefully controlled light preload.
Can RU85 directly replace CRBF5515AT?
It is a dimensional cross-reference candidate, but replacement should only be approved after comparing the complete drawings, mounting holes, counterbores, seals, load ratings, accuracy, clearance or preload and rotational torque.
What information is required for an RU85 quotation?
Please provide quantity, radial and axial loads, overturning moment, speed, duty cycle, rotating ring, required accuracy, clearance or preload, seal type, temperature, lubricant and any inspection-document requirements.
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