The RU297 cross roller bearing is a large, high-rigidity precision bearing with a 210 mm bore, 380 mm outside diameter and 40 mm width. Integrated mounting holes in both rings allow direct installation without a separate bearing housing or clamping flange in many rotary systems.
RU297 has a 156 kN basic dynamic load rating, a 281 kN basic static load rating and an approximate mass of 21.3 kg. It is suitable for large robot bases, heavy-duty positioners, CNC rotary tables, hollow direct-drive axes and precision observation platforms.
LYDL supplies RU297, RU297G and RU297X mounting configurations. Open or sealed structures, CC0/C0 clearance, P5/P4/P2 accuracy and NP6×5 grease fittings are available. Dimensional reports, rotational inspection and reinforced export packaging can be provided.
RU297 Cross Roller Bearing | Reliable 210×380×40 mm
The RU297 cross roller bearing is a large crossed cylindrical roller bearing with integrated inner and outer rings. Mounting holes are machined directly into both rings.
Its rollers are arranged alternately at right angles. This allows one bearing to support radial load, axial load and overturning moment.
RU297 combines a 210 mm hollow bore with a 40 mm axial width. It is designed for large rotary mechanisms that require rigidity, positioning accuracy and service routing through the rotational center.
View the complete RU cross roller bearing series or explore our cross roller bearing category for other sizes and structures.
RU297 Cross Roller Bearing Specifications
Parameter
RU297 specification
Bore diameter, d
210 mm
Outside diameter, D
380 mm
Bearing width, B
40 mm
Roller pitch circle diameter, dp
297.3 mm
Basic dynamic load rating, C
156 kN
Basic static load rating, C₀
281 kN
Approximate mass
21.3 kg
Maximum inner shoulder diameter, ds
272 mm
Minimum outer shoulder diameter, Dh
320 mm
Minimum chamfer radius, r
2.5 mm
Greasing-hole diameter, d₁
6 mm
Inner-ring bolt-circle diameter
240 mm
Outer-ring bolt-circle diameter
350 mm
Inner-ring mounting holes
16 holes
Outer-ring mounting holes
16 holes
Available mounting structures
RU297, RU297G and RU297X
Available seals
Open, UU, U or UT
Available clearance
CC0 or C0
Available accuracy
P5, P4 or P2
Optional grease nipple
NP6×5
The dimensions and ratings are catalog reference values.
Final selection must consider the actual load spectrum, moment arm, speed, mounting rigidity and required service life. The approved LYDL drawing remains the controlling dimensional document.LYDL RU297 cross roller bearing for large precision rotary systems.
Key Advantages of the RU297 Cross Roller Bearing
Large 210 mm Hollow Bore
The 210 mm center opening provides space for a hollow shaft, reducer output or direct-drive motor rotor.
It can also route electrical cables, pneumatic tubes, hydraulic lines and sensor connections through the rotary axis.
The effective routing space must include shoulders, bolts, connectors and cable bend radius.
Integrated Mounting Structure
The RU297 cross roller bearing can be fastened directly to the rotating component and supporting frame.
This may eliminate a separate housing or clamping flange. It can also reduce the number of surrounding components.
Direct mounting still requires rigid support. Thin plates or interrupted mounting surfaces may deform the bearing rings.
Combined-Load Capacity
RU297 supports radial, axial and moment loads in one bearing position.
This is useful in robot bases, positioners and rotary tables with an offset payload. The overturning moment must be calculated from load and distance.
High Rigidity in a Compact Width
RU297 has a 380 mm outside diameter but remains only 40 mm wide.
This helps reduce axial assembly length. However, the large diameter makes mounting-face flatness and bolt-load distribution especially important.
Inner- and outer-ring counterbores face the same direction
Both bolt heads are accessible from the same assembly side
RU297G
Inner- and outer-ring counterbores face opposite directions
The two rings are fastened from opposite sides
RU297X
Inner ring has M12 threaded holes; outer ring retains counterbored through holes
Bolts must engage directly with the inner ring
RU297 Standard Mounting Holes
The inner ring has 16 × Ø14 through holes on a 240 mm PCD.
Each hole has an Ø20 counterbore with a depth of 13 mm.
The outer ring has the same hole dimensions on a 350 mm PCD. The inner- and outer-ring counterbores face the same direction.
RU297G Mounting Holes
RU297G uses the same hole quantity, diameters, counterbore dimensions and bolt circles.
Its inner- and outer-ring counterbores face opposite directions. This supports installation from two different sides.
RU297X Mounting Holes
RU297X has 16 × M12 threaded through holes in the inner ring on a 240 mm PCD.
The outer ring has 16 × Ø14 through holes with Ø20 × 13 mm counterbores on a 350 mm PCD.
Confirm the mounting direction before ordering. RU297, RU297G and RU297X should not be selected from boundary dimensions alone.
Seal, Clearance and Accuracy Codes
A configured designation may be written as: RU297 / UU / CC0 / P4 / B / G / -N
Code
Meaning
No seal code
Open bearing
UU
Seals installed on both sides
U
One seal on the outer-ring counterbore side
UT
One seal on the opposite side
CC0
Controlled negative-clearance or preload range
C0
Normal reference clearance
P5
Precision-grade rotational accuracy
P4
Higher rotational accuracy
P2
Ultra-precision accuracy
No R or B code
Accuracy referenced to inner-ring rotation
R
Accuracy referenced to outer-ring rotation
B
Accuracy applied to both rings
G
Opposite counterbore directions
X
M12 threaded holes in the inner ring
-N
Grease nipples supplied
NP6×5
Grease nipple specified for this size group
Not every suffix combination is a stocked product.
The complete designation must appear on the quotation and drawing. Clearance, accuracy, seal orientation and controlled ring should be confirmed separately.
RU297 Cross Roller Bearing Applications
Typical applications include:
Large industrial robot bases
Heavy robotic positioners
Welding and assembly positioners
CNC rotary and tilting tables
Large precision indexing systems
Hollow-shaft direct-drive motors
Reducer output supports
Optical observation platforms
Antenna and radar positioners
Large inspection and scanning systems
Semiconductor equipment turntables
Automated production fixtures
RU297 is well suited to systems that require a large central opening.
It can support internal cable routing while keeping the rotary structure relatively compact. The final design must protect cables from twisting, abrasion and excessive bending.
For positioners, include the fixture, workpiece and center-of-gravity distance in the load calculation.
Emergency stopping and rapid reversal may produce higher moment loads than steady operation.Typical RU series applications include compact robots, rotary actuators, inspection systems and laboratory automation
RU297 provides a substantial increase in bore size and ratings over RU228.
RU445 should be considered when a 350 mm central opening or greater static-load margin is required. Its larger dimensions also demand a stronger supporting structure.
See our cross roller bearing selection guide for additional selection factors.
Need an RU297 Drawing or Quick Quotation?
If the model is known, send the RU297, RU297G or RU297X designation, accuracy, seals, quantity and destination.
If selection is not complete, provide the loads, moment arm, speed, duty cycle and available mounting space. Request an RU297 technical review and quotation
Brand Reference and Interchange Guidance
THK RU297, RU297G and RU297X designations may be used as reference numbers when identifying an existing bearing.
Matching 210 × 380 × 40 mm dimensions alone does not confirm interchangeability.
Before replacing another brand, compare:
Inner- and outer-ring bolt circles
Hole quantity and diameter
Counterbore direction and depth
M12 threaded-hole location
Shoulder dimensions
Seal orientation
Clearance or preload
Controlled rotating ring
Radial and axial runout
Grease-port position
Load ratings
Starting and running torque
Some market cross-reference tables associate the size with CRBF21040 or CRBE21040 designations.
These references should be treated as search aids only. IKO, HIWIN and other manufacturers may use different internal designs, ratings and suffix systems.
Obtain the original label and technical drawing before approving a replacement.
THK, IKO and HIWIN names belong to their respective owners. They are used only for product identification and technical comparison.
LYDL is an independent manufacturer. It does not claim affiliation with or endorsement by these brands.
RU297 Installation Recommendations
Provide Rigid Supporting Plates
RU297 has large 240 mm and 350 mm bolt circles.
The mounting plates must distribute bolt force without local bending. Thin plates can deform between fasteners.
Evaluate plate thickness, ribs, material and foundation stiffness together. Bearing accuracy cannot compensate for a flexible base.
Inspect Mounting-Face Flatness
Clean both mounting faces before assembly.
Remove burrs, dirt and raised material around every hole. Confirm that the bearing seats without rocking or forced alignment.
Mounting-face errors can increase torque and reduce rotational accuracy.
Use a Progressive Tightening Sequence
Install all bolts before applying final torque.
Tighten in a diagonal sequence. A practical process is to increase torque in several stages, such as 30%, 60% and 100%.
The final torque must follow the selected fastener grade, thread engagement, lubrication and mating material.
Manage the 21.3 kg Bearing Safely
Use suitable lifting and positioning equipment.
Support the bearing evenly. Do not lift it by a seal, grease nipple or a small number of mounting holes.
Protect the ring edges and precision mounting faces from impact.
Confirm Lubrication Access
The RU297 cross roller bearing has 6 mm reference greasing holes.
An NP6×5 nipple can be supplied when specified with the -N code. Check nipple access after surrounding components are installed.
Relubrication intervals depend on load, speed, temperature, motion angle and contamination.
Perform a Controlled Run-In
Rotate the system slowly after installation.
Check torque, noise, vibration and temperature. Increase operating speed and load gradually.
Continuous high-speed use requires separate verification of preload, grease, seal drag and heat generation.
RU297 Inspection and Export Packaging
LYDL inspection for an RU297 cross roller bearing may include:
Bore, outside diameter and width measurement
Roller pitch circle verification
Inner- and outer-ring PCD inspection
Through-hole and counterbore measurement
M12 thread inspection for RU297X
Clearance or preload confirmation
Radial and axial runout inspection
Starting and running-torque measurement
Seal and lubrication-port inspection
Appearance and marking verification
Inspection report and product photographs
At approximately 21.3 kg, RU297 requires reinforced packaging.
After inspection, the bearing is cleaned and protected against corrosion. It is then secured against movement and edge impact.
A reinforced carton or wooden case can be selected according to quantity and transport conditions.dimensional inspection, rotation testing and protective export packaging at LYDL.
Why Source RU297 from LYDL?
RU297, RU297G and RU297X configurations
Open, UU, U and UT seal options
CC0 and C0 clearance control
P5, P4 and P2 accuracy capability
Mounting-hole and M12 thread inspection
Rotational runout and torque reports
Grease and seal customization
OEM marking and batch traceability
Reinforced export packaging
Application-based technical support
RU297 Cross Roller Bearing FAQ
Why is the 210 mm bore useful?
The bore can accommodate a hollow shaft, motor rotor, reducer output or service lines.
The effective opening must include shoulders, connectors, fasteners and cable bend radius.
How is the allowable overturning moment determined?
It cannot be determined directly from the 281 kN static rating.
The calculation requires radial load, axial load, moment arm, acceleration, shock and required safety factor.
When should RU297G be selected?
Select RU297G when the two rings must be fastened from opposite sides.
Its counterbores face opposite directions, while the standard RU297 counterbores face the same direction.
What is the main benefit of RU297X?
RU297X provides 16 M12 threaded holes in the inner ring.
It is useful when bolts must engage directly with the inner ring and rear-side nuts cannot be installed.
Can a flexible mounting plate reduce bearing accuracy?
Yes.
A flexible or uneven plate can deform the bearing rings. This may increase torque, runout and load concentration.
Is RU297 designed for continuous high speed?
RU297 is mainly selected for rigidity, precision and combined-load capacity.
High-speed operation requires verification of preload, seals, grease, heat generation and drive torque.
How should a 21.3 kg RU297 be handled?
Use suitable lifting support and protect the precision faces.
Do not lift the bearing by its seals, grease nipple or unsupported ring edges.
When should RU445 be selected?
Consider RU445 when the machine requires a 350 mm bore or greater static-load capacity.
RU297 remains the more compact option when its 210 mm bore and calculated capacity are sufficient.
LYDL can provide an RU297 quotation, technical drawing, lead-time confirmation and application review.
Engineering Standards and References
The following references support product identification, calculation and inspection terminology:
THK Model RU Technical Data — RU297 dimensions, ratings, mounting holes, suffixes and grease-nipple specifications: THK Cross-Roller Ring Technical Data
THK RU Product Overview — integrated inner- and outer-ring structure and application characteristics: THK Model RU
THK Model Number Coding — seal, clearance, accuracy and rotating-ring designation principles: THK Model Number Coding
IKO Crossed Roller Bearing Catalog — crossed roller structure and alternative brand terminology: IKO Crossed Roller Bearings
ISO 281:2007 — dynamic load ratings and rating life: ISO 281:2007
ISO 492:2023 — radial bearing geometrical specifications and tolerances: ISO 492:2023
ISO 15:2017 — radial bearing boundary-dimension principles: ISO 15:2017
ISO 15243:2017 — bearing damage and failure classification: ISO 15243:2017
These references provide general engineering frameworks.
The LYDL-approved drawing, inspection agreement and purchase order remain the controlling documents for the supplied bearing.
