The RA5008 cross roller bearing is an ultra-thin precision bearing with a 50 mm bore, 66 mm outside diameter and only 8 mm width. Its approximate 0.08 kg mass makes it suitable for small robot joints, optical stages and lightweight automation 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 RA5008 cross roller bearing in open, sealed, C0 and CC0 configurations. Higher accuracy, special grease, clearance control 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.
RA5008 Cross Roller Bearing Overview
The RA5008 cross roller bearing provides a 50 mm through-bore within a 66 mm outside diameter.
Its width is only 8 mm. The compact envelope is suitable for small rotary mechanisms with strict space and weight limits.
The difference between the bore and outside diameter is 16 mm. The radial section is therefore only 8 mm on each side.
Cylindrical rollers are arranged alternately at 90 degrees between the raceways. One bearing position can support radial, bidirectional axial and overturning moment loads.
Spacer retainers separate adjacent rollers. They reduce roller-to-roller friction and help stabilize rotational torque.
RA5008 has a one-piece inner ring and a separable outer ring. The inner ring is normally used as the rotating ring when running accuracy is important.
RA5008 Cross Roller Bearing Specifications
The principal RA5008 cross roller bearing dimensions and catalogue ratings are listed below.
Parameter
RA5008 specification
Bore diameter, d
50 mm
Outside diameter, D
66 mm
Width, B
8 mm
Radial section, (D − d) ÷ 2
8 mm
Roller pitch circle, dp
57 mm
Lubrication-hole reference, a × b
2 × 0.8 mm
Minimum corner radius, r min
0.5 mm
Maximum shaft shoulder, ds
53.5 mm
Minimum housing shoulder, Dh
60.5 mm
Basic dynamic radial load rating, C
5.10 kN
Basic static radial load rating, C0
7.19 kN
Approximate mass
0.08 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 combined-load operation.
Bearing life depends on the actual radial load, axial load, moment, speed, duty cycle, lubrication and required reliability.
Confirm the approved LYDL drawing before machining the shaft, housing or retaining cover.
What Makes RA5008 Different?
Compact 50 mm Through-Bore
The RA5008 cross roller bearing provides a 50 mm opening inside a 66 mm outside diameter.
The bore can accommodate a small hollow shaft, cables, pneumatic tubing or optical components.
Approximately 0.08 kg
RA5008 weighs only about 0.08 kg.
Its low mass is beneficial for moving robot arms, optical modules and laboratory equipment where inertia must be controlled.
Only 8 mm Wide
The bearing needs only 8 mm of axial installation space.
This leaves additional room for compact motors, encoders, brakes or transmission components.
Multiple Loads in One Bearing Position
The crossed rollers support radial, bidirectional axial and moment loads.
This can reduce the number of bearings required in a small rotary mechanism.
Sensitive to Mounting Geometry
The thin rings save space and weight but can follow errors in the surrounding structure.
Housing roundness and retaining-cover flatness are therefore important to installed accuracy and torque.
Typical RA5008 Cross Roller Bearing Applications
The RA5008 cross roller bearing is suitable for:
Small robot wrists and gripper axes
Compact SCARA robot joints
Microscope and optical rotary stages
Laboratory automation equipment
Semiconductor inspection modules
Precision camera and sensor gimbals
Medical testing instruments
Compact indexing mechanisms
The 50 mm opening provides useful routing space without requiring a large housing.
RA5008 is especially valuable when low mass and a thin bearing section are more important than high load capacity.
For additional selection information, visit the LYDL Cross Roller Bearing Guide and Cross Roller Bearing Product Range.
Need an RA5008 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 RA5008 cross roller bearing configuration and provide a quotation with the controlled drawing.
RA5008 Variants and Suffixes
Suffix conventions can vary between manufacturers. Confirm the complete designation and technical requirements before ordering.
Improves grease retention and contamination protection
RA5008C
Single-split alternative
Structure and availability require drawing confirmation
RA5008CUU
Single-split type with two seals
Confirm seal 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 improve grease retention and provide additional contamination protection.
Seal contact can increase starting torque. Open bearings may be preferable inside a clean enclosure requiring minimum resistance.
CC0 preload can improve rigidity and positioning stability. Excessive preload can increase friction, heat and sensitivity to mounting error.
An LYDL RA5008 cross roller bearing should be configured according to the application rather than by suffix alone.
Short Brand Naming Guide
Different manufacturers may use different names for bearings with a similar 50 × 66 × 8 mm envelope.
Brand or supplier group
Common designation
Important note
THK
RA5008 / RA5008UU
RA-series reference designation
IKO
CRBS508, CRBS508 A UU or CRBS508 V
Internal structure and ratings vary by version
LYDL
RA5008, RA5008UU, RA5008UUCC0
Accuracy and clearance suffixes follow the approved order
Some aftermarket suppliers
XRA5008 or SRA5008
Supplier-specific prefix; drawing comparison is required
Similar model names do not guarantee identical rollers, preload, accuracy, seals or load ratings.
Use the complete suffix and controlled drawing when comparing brands.
Choose the RA8008 Cross Roller Bearing when the mechanism requires an 80 mm passage.
Select the RA9008 Cross Roller Bearing when a 90 mm central opening is required.
RA5008 provides the smallest housing envelope and lowest mass of these three models.
Installation and Housing Requirements
The thin rings of the RA5008 cross roller bearing follow the geometry of the surrounding structure.
Control housing roundness, shaft coaxiality, shoulder perpendicularity and retaining-cover flatness.
Use 53.5 mm as the catalogue maximum shaft-shoulder diameter. Use 60.5 mm as the catalogue minimum housing-shoulder diameter.
Confirm both values against the final LYDL drawing.
A 66 mm bearing outside diameter does not mean the complete housing can also be 66 mm.
Additional material is required for the housing wall, retaining cover and fasteners.
Clean all mounting surfaces and remove burrs before installation. Do not force the bearing into a distorted housing.
Tighten the outer-ring cover gradually in a diagonal sequence. Uniform force helps prevent deformation of the separable outer ring.
After installation, rotate the inner ring slowly. Check starting torque, smoothness, noise and runout before connecting the motor.
Abnormal torque may result from:
Uneven retaining-cover tightening
Housing roundness error
Insufficient cover rigidity
Shaft and housing misalignment
Excessive interference or preload
Seal drag
Excessive or unsuitable grease
These installation factors should be checked before identifying the bearing as defective.
Accuracy and Small-Motor Torque
Accuracy requirements should identify the rotating ring and inspection method.
RA5008 is normally used with inner-ring rotation. The measured runout should match the final assembly arrangement.
A higher accuracy grade cannot compensate for a distorted housing or uneven outer-ring clamping.
Small motors may have limited starting torque. Seal resistance, preload, grease viscosity and clamping deformation should be evaluated before ordering.
Lubrication and Operating Conditions
Standard RA5008 configurations normally use grease lubrication.
Grease viscosity and fill quantity should match the load, speed, temperature and required torque.
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 RA5008 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
Torque and roundness control are particularly important for a bearing weighing only about 0.08 kg.
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
RA5008 and IKO CRBS508 share nominal boundary dimensions of 50 × 66 × 8 mm.
Their published load ratings and mass are not identical. CRBS508 variants can also use different retainers, separators or roller complements.
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
Clearance or preload requirement
Rotating ring
Loads, moment and speed
Lubrication and operating environment
LYDL will compare the existing bearing with the RA5008 cross roller bearing and issue a controlled drawing for approval.
RA5008 Cross Roller Bearing FAQ
1. Is RA5008 the smallest option for a 50 mm bore?
It is one of the compact 8 mm-wide choices.
Thinner 5 mm alternatives may exist, but they normally have different outside dimensions, ring structures and lower load capacity.
2. Can the complete housing outside diameter be only 66 mm?
Normally no. The bearing outside diameter is 66 mm, but the housing needs additional wall thickness, a retaining cover and fastener space.
The final envelope should be determined from the complete assembly drawing.
3. Is a 0.08 kg bearing strong enough for a robot joint?
Low mass does not mean the bearing has no load capacity.
Suitability depends on the actual radial, axial and moment loads, housing rigidity and required service life.
4. Which clearance is better for an optical stage?
C0 generally favors lower torque. CC0 can improve rigidity and reduce internal movement.
The correct choice depends on motor torque, positioning accuracy, temperature and mounting quality.
5. Why might a small motor struggle to rotate RA5008?
Possible causes include seal friction, excessive preload, high-viscosity grease and outer-ring deformation after clamping.
Provide the available starting torque before choosing the final configuration.
6. Can the outer ring rotate?
RA5008 is normally used with 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 bearing structure.
7. Can RA5008 directly replace IKO CRBS508?
The nominal boundary dimensions match, but published ratings and available internal configurations differ.
Compare clearance, accuracy, seals, lubrication, shoulders and controlled drawings before replacement.
8. Can RA5008 be supplied for vacuum or cleanroom use?
Yes, subject to technical confirmation.
Vacuum-compatible grease, low-particle requirements, seals, materials and cleaning procedures must be defined before production.
Request an RA5008 Quotation
Send your application data or existing drawing to receive an RA5008 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.
