The RA9008 cross roller bearing is an ultra-thin precision bearing with a 90 mm bore, 106 mm outside diameter and only 8 mm width. Its compact envelope and approximate 0.12 kg mass make it suitable for robot joints, optical stages and lightweight rotary mechanisms.
Cylindrical rollers arranged alternately at 90 degrees allow one bearing position to support radial, bidirectional axial and overturning moment loads. The one-piece inner ring is normally selected as the rotating ring, while the separable outer ring requires uniform housing support.
LYDL supplies the RA9008 cross roller bearing in open, sealed, C0 and CC0 configurations. Higher accuracy, special grease, controlled clearance and inspection reports are available after technical confirmation.
Send your quantity, loads, speed, accuracy, sealing and lubrication requirements for an LYDL drawing review and quotation.
RA9008 Cross Roller Bearing Overview
The RA9008 cross roller bearing provides a 90 mm through-bore within a 106 mm outside diameter.
Its width is only 8 mm. This compact geometry helps reduce the axial space and rotating mass of precision equipment.
The difference between the bore and outside diameter is only 16 mm. The resulting radial section is 8 mm on each side.
Cylindrical rollers are arranged alternately at 90 degrees between the raceways. One bearing position can support radial load, axial load in both directions and overturning moment.
Spacer retainers separate adjacent rollers. They reduce roller-to-roller friction and help stabilize rotational torque.
RA9008 uses a one-piece inner ring and a separable outer ring. The inner ring is normally selected as the rotating ring when running accuracy is important.RA9008 combines a 90 mm bore with an 8 mm thin section for lightweight and compact precision rotary mechanisms
RA9008 Cross Roller Bearing Specifications
The principal RA9008 cross roller bearing dimensions and catalogue ratings are listed below.
Parameter
RA9008 specification
Bore diameter, d
90 mm
Outside diameter, D
106 mm
Width, B
8 mm
Radial section, (D − d) ÷ 2
8 mm
Roller pitch circle, dp
97 mm
Lubrication-hole reference, a × b
2 × 0.8 mm
Minimum corner radius, r min
0.5 mm
Maximum shaft shoulder, ds
93.5 mm
Minimum housing shoulder, Dh
100.5 mm
Basic dynamic radial load rating, C
6.76 kN
Basic static radial load rating, C0
12.4 kN
Approximate mass
0.12 kg
Ring structure
One-piece inner ring and separable outer ring
Standard lubrication
Grease lubrication
Standard-grease temperature range
−15°C to +80°C
The listed load ratings are basic radial catalogue values. They are not direct allowable limits for a combined-load application.
Bearing life depends on radial load, axial load, moment arm, speed, duty cycle, lubrication and required reliability.
Confirm the approved LYDL drawing before machining the shaft, housing or retaining cover.
What Makes RA9008 Different?
Practical 90 mm Through-Bore
The RA9008 cross roller bearing provides more routing space than RA8008 without requiring the 116 mm outside diameter of RA10008.
Its 90 mm opening can accommodate a hollow shaft, encoder components, cables, pneumatic tubes or an optical path.
Only 8 mm Wide
RA9008 maintains an 8 mm width while providing a relatively large central opening.
This leaves more axial space for motors, encoders, brakes and transmission components.
Low 0.12 kg Mass
The bearing weighs approximately 0.12 kg.
Low mass helps reduce inertia in robot arms, scanning heads, inspection platforms and other moving assemblies.
Combined-Load Capability
The crossed rollers support radial, bidirectional axial and moment loads in one bearing position.
This can simplify a compact rotary mechanism that would otherwise require separate radial and thrust bearings.
Size Balanced Between RA8008 and RA10008
RA9008 fills the dimensional gap between the 80 mm bore of RA8008 and the 100 mm bore of RA10008.
It is useful when an 80 mm opening is too small but the machine does not need a full 100 mm passage.
Typical RA9008 Cross Roller Bearing Applications
The RA9008 cross roller bearing is suitable for:
Compact robot wrists and elbows
Hollow-shaft servo modules
Optical and laser scanning stages
Industrial vision and inspection gimbals
Semiconductor alignment equipment
Laboratory automation systems
Precision measuring instruments
Compact indexing mechanisms
The 90 mm opening provides useful space for an encoder ring, cable bundle or hollow drive shaft.
RA9008 should be selected according to the complete loads, moment arm, required accuracy and installed torque.
For additional selection information, visit the LYDL Cross Roller Bearing Guide and Cross Roller Bearing Product Range.supports compact rotary motion in robot joints, optical stages, semiconductor equipment and inspection systems.
Need an RA9008 technical review? Send LYDL your quantity, radial load, axial load, moment load, speed and duty cycle.
Please include the rotating ring, accuracy, clearance or preload, sealing, lubricant and operating temperature.
We will review the RA9008 cross roller bearing configuration and provide a quotation with the controlled drawing.
RA9008 Variants and Suffixes
Suffix conventions can vary between manufacturers. Confirm the complete designation and technical requirements before ordering.
Improves grease retention and contamination protection
RA9008C
Single-split alternative
Structure and availability require drawing confirmation
RA9008CUU
Single-split type with two seals
Confirm sealing drag and operating torque
C0
Standard or positive radial clearance
Generally favors lower rotational resistance
CC0
Controlled negative clearance or preload
Improves rigidity but increases mounting sensitivity
P6T / P5T
Specified rotational-accuracy options
Confirm the rotating ring and inspection method
P4 / P2 custom
LYDL high-precision option
Requires approved accuracy and inspection criteria
UU seals provide additional contamination protection and grease retention.
Seal contact can increase starting torque. Open bearings may be preferable in clean equipment requiring minimum rotational resistance.
CC0 preload can improve rigidity and positioning stability. Excessive preload can increase friction, heat and mounting sensitivity.
An LYDL RA9008 cross roller bearing should be configured from the application rather than from a suffix alone.
Choose the RA8008 Cross Roller Bearing when an 80 mm passage is sufficient and the smallest outside diameter is preferred.
Select the RA10008 Cross Roller Bearing when the application requires a 100 mm central opening.
RA9008 provides a balanced middle option. Its bore and outside diameter are both 10 mm larger than RA8008 and 10 mm smaller than RA10008.
Installation and Housing Requirements
The thin rings of the RA9008 cross roller bearing closely follow the geometry of the surrounding components.
Control housing roundness, shaft coaxiality, shoulder perpendicularity and retaining-cover flatness.
Use 93.5 mm as the catalogue maximum shaft-shoulder diameter. Use 100.5 mm as the catalogue minimum housing-shoulder diameter.
Confirm both dimensions against the final LYDL drawing.
Clean all mating surfaces before installation. Remove burrs that could cause local stress or misalignment.
Do not strike the rings or force the bearing into a distorted housing.
Tighten the outer-ring retaining cover gradually in a diagonal sequence. Uniform force helps prevent deformation of the separable outer ring.
After installation, rotate the inner ring slowly. Check torque, noise, smoothness and runout before connecting the motor.
Abnormal installed torque may result from:
Uneven retaining-cover tightening
Housing roundness error
Insufficient cover rigidity
Shaft and housing misalignment
Excessive interference
Excessive preload
Seal drag or excessive grease
These installation factors should be checked before identifying the bearing as the source of the problem.
Accuracy and Rotational Torque
Accuracy requirements should identify which ring rotates and which surface is measured.
RA9008 is normally used with inner-ring rotation. The runout inspection method should match the final assembly arrangement.
A higher accuracy grade cannot compensate for a distorted housing or uneven outer-ring clamping.
Installed torque should be measured after the retaining cover reaches its specified tightening condition.
For direct-drive equipment, provide the motor’s available starting torque. This helps determine whether seals or CC0 preload are suitable.
Lubrication and Operating Conditions
Standard RA9008 configurations normally use grease lubrication.
Grease viscosity and fill quantity should match the load, speed, temperature and required rotational resistance.
The published −15°C to +80°C range relates to a standard grease configuration.
Vacuum, cleanroom, low-temperature and high-temperature applications require separate grease, seal and material confirmation.
Open bearings require a clean enclosure. Sealed versions improve protection but are not maintenance-free in every operating condition.
LYDL Manufacturing and Quality Control
LYDL controls ring material, heat treatment, raceway grinding, roller sorting, assembly clearance and final inspection.
Inspection for an RA9008 cross roller bearing can include:
Bore, outside diameter and width
Raceway geometry and surface condition
Radial clearance or preload
Inner-ring rotational runout
Starting and running torque
Noise and rotational smoothness
Seal condition and grease quantity
Marking and packaging inspection
Roundness and torque control are particularly important because RA9008 has only an 8 mm radial section.
Material certificates, dimensional reports and accuracy records can be supplied when agreed before production.
LYDL uses anti-rust protection and shock-resistant export packaging. Concentrated pressure on the thin outer ring is avoided.
Interchange and Cross-Reference Guidance
RA9008 and IKO CRBS908 share nominal boundary dimensions of 90 × 106 × 8 mm.
Their published load ratings and mass are not identical. Internal roller design, clearance, accuracy and sealing options may also differ.
A matching bore, outside diameter and width do not prove complete interchangeability.
Before replacement, provide:
Existing manufacturer and complete model
All suffixes
Shaft and housing drawing
Required clearance or preload
Rotating ring
Loads, moment and speed
Lubrication and environmental conditions
LYDL will compare the existing product with the RA9008 cross roller bearing and issue a controlled drawing for approval.
RA9008 Cross Roller Bearing FAQ
1. When should I choose RA9008 instead of RA8008 or RA10008?
Choose RA9008 when an 80 mm passage is too small but a 100 mm bore would unnecessarily increase the housing size.
It provides a practical middle option with a 90 mm bore and 106 mm outside diameter.
2. Can an encoder be installed inside the 90 mm bore?
It may be possible, but the usable opening depends on the shaft, shoulders, fasteners and cable-routing structure.
Check the complete assembly drawing rather than relying only on the nominal bore.
3. Is RA9008 suitable for a compact servo output?
Yes, if the combined loads, moment, speed, accuracy and torque meet the application requirements.
The 8 mm width leaves additional axial space for a motor, encoder, brake or gearbox.
4. What determines the moment capacity of RA9008?
Moment performance depends on the internal crossed-roller geometry, applied moment arm, preload and surrounding housing rigidity.
The static radial rating should not be used as a direct allowable moment value.
5. Why can torque vary once during every revolution?
Periodic torque can indicate housing roundness error, uneven cover clamping, misalignment or localized contamination.
The shaft, housing and retaining cover should be checked before replacing the bearing.
6. Can the outer ring rotate?
RA9008 is normally selected for inner-ring rotation because its outer ring is separable and housing-clamped.
For outer-ring rotation, evaluate an integrated-ring RAU design or another suitable structure.
7. Can RA9008 directly replace IKO CRBS908?
The nominal dimensions match, but published load ratings, mass and internal configurations differ.
Compare clearance, accuracy, seals, lubrication, shoulders and controlled drawings before approving replacement.
8. Is RA9008UU necessary inside a sealed machine?
Not always. An open bearing may provide lower resistance when the machine already has effective contamination control.
Choose UU when additional grease retention and environmental protection are more important than minimum torque.
Request an RA9008 Quotation
Send your application data or existing drawing to receive an RA9008 cross roller bearing quotation.
LYDL can review open, sealed, clearance-controlled and customized precision configurations.
Provide quantity, loads, moment, speed, rotating ring, accuracy, clearance, sealing, lubricant and temperature for an efficient technical review.
ISO 492:2023 — geometrical product specifications and radial-bearing tolerances.
Engineering note: Catalogue values support preliminary selection only. Final life, fit, accuracy, clearance and interchangeability require complete application data and an approved LYDL drawing.
