1 Model Information & Technical Parameters

Model：KDN.K02508AR0

Dimensions

Matching shaft diameter d：25 mm

Assembly width B：8 mm

Effective needle roller length：7.2 mm

Performance Data

Minimum required shaft hardness ≥HRC60

Shaft raceway roughness Ra ≤0.2 μm

AR0: Standard radial clearance group

Technical Attributes

Supply form: Needle rollers + cage assembly (without inner ring & outer ring)

Structure type: KDN inner-ringless caged needle roller assembly

Axial characteristic: Only radial load acceptable, axial force prohibited

Cage: High-strength pressed steel cage

Coating: None

Seal: Open construction, no built-in seal

Pre-grease: None

Logistics & Industry Codes

Net weight：0.018 kg

Indicative carbon footprint：0.06 kg CO₂e

eClass code：23-05-09-01

UNSPSC code：31171506

Suffix Explanation

KDN.K: Caged needle roller assembly without separate inner and outer rings; shaft and housing bore act as raceway surfaces.

02508: Suitable shaft diameter 25 mm, assembly width 8 mm.

AR0: Standard radial clearance grade for general applications, wider clearance range and better assembly tolerance compared with CP0.

Important reminder: This model has no solid inner and outer rings. The mating shaft and housing bore must be hardened and precision ground. Insufficient hardness and surface finish will lead to rapid wear, raceway scoring or seizure. Only pure radial load is allowed; continuous axial impact is forbidden. Open design relies on external lubrication and housing dust protection; dry running is prohibited. Do not strike the cage directly during installation; pressing force shall be applied to cage end face.

2 Structure & Operating Characteristics

Japan NMT KDN.K02508AR0 compact caged needle roller assembly removes independent inner and outer rings to achieve minimum radial installation size. Classified needle rollers ensure uniform load distribution. AR0 standard clearance fits general precision transmission applications with higher assembly tolerance than CP0 precision version. Pressed steel cage separates rollers to avoid roller-to-roller contact friction and improve permissible rotational speed.

Selection reference: KDN.K02508AR0 (AR0 standard clearance for general use); KDN.K02508CP0 (CP0 precision clearance for low-runout high-precision equipment); NA/NK/RNA series are needle bearings with outer ring.

3 Core Performance Advantages

1. Minimal structure without inner and outer rings, ultra-small radial dimension suitable for compact integrated machinery.

2. AR0 standard clearance offers high assembly tolerance, ideal for mass production of general machinery.

3. Classified high-precision needle rollers realize balanced contact stress and stable wear resistance.

4. Cage separates rollers to eliminate sliding friction between rollers and raise maximum allowable speed.

5. Compatible with integrated housing design to realize lightweight transmission unit integration.

6. Open design supports both long-term grease lubrication and circulating oil lubrication.

4 Typical Application Fields

4.1 Automation Equipment

Rotary fixture supports, linear module hinge pivots, miniature manipulator oscillating joints

4.2 Light Industry Conveying Machinery

Conveyor roller supports, connecting rod oscillating mechanisms, textile machine rotary pivots

4.3 General Transmission Parts

Auxiliary supports for small gearboxes, hinge parts of low-speed reducers

4.4 Construction Machinery Accessories

Miniature hinges for hydraulic equipment, light-load oscillating support points

5 Assembly Specifications & Usage Guidelines

5.1 Assembly Environment & Operation Standards

Maintain clean assembly environment to prevent metal debris entering roller gaps. Apply pressing force on cage end face; never strike cage body directly. Manually rotate after assembly to confirm smooth rotation without jamming or abnormal noise. Inspect hardness and roughness of shaft and housing raceway in advance.

5.2 Selection Guidance

General working conditions, loose assembly tolerance, no ultra-low runout requirement → KDN.K02508AR0

High-precision equipment requiring low vibration and low runout → KDN.K02508CP0

Outer ring required for direct installation into housing bore → NK / RNA needle roller bearings

Complete inner and outer rings for standard bearing replacement → NA series needle roller bearings

5.3 Lubrication Maintenance Instruction

No pre-filled lubricant at delivery; evenly apply grease during assembly. Circulating oil lubrication is recommended for continuous medium-high speed operation. Establish regular oil replenishment cycle; dry operation is strictly prohibited.

5.4 Environmental Application Notes

No anti-rust coating. Apply anti-rust oil and seal tightly for long-term storage. Install housing end covers and oil seals under dusty and humid conditions. Add buffer structure if frequent impact loads exist.

6 Fault Identification

Common failure modes: Needle roller surface pitting, shaft raceway scoring, cage distortion & fracture, sintering caused by poor lubrication. Once cage deformation or roller damage occurs, replace the whole assembly completely; repairing and reusing are forbidden.