NMT Ltd.
Corporate Communications Department
Japan NMT KDN.K02508CP0 KDN Series Precision Needle Roller Assembly, Caged Needle Roller Unit, CP0 Precision Clearance Class
1 Model Information & Technical Parameters
Model：KDN.K02508CP0
Dimensions
Matching shaft diameter d：25 mm
Assembly width B：8 mm
Effective needle roller length：7.2 mm
Performance Data
Required shaft hardness ≥HRC60
Shaft raceway roughness Ra ≤0.2 μm
CP0: Precision 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: Radial load only, no axial load capacity
Cage: High-strength pressed steel cage
Coating: None
Seal: Open type, no 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 inner and outer rings; shaft and housing serve as raceway surfaces.
02508: Suitable shaft diameter 25 mm, assembly width 8 mm.
CP0: Precision radial clearance grade for high-precision operation and low runout applications.
Important reminder: This model has no solid inner or outer ring. The shaft and housing bore must be hardened and precision ground to meet hardness and roughness standards, otherwise rapid wear and seizure will occur. It can only bear pure radial load; axial force is not permitted. Open design requires external lubrication and housing dust sealing. Dry friction operation is prohibited. Avoid unilateral impact on rollers during installation; never strike the cage directly.
2 Structure & Operating Characteristics
Japan NMT KDN.K02508CP0 compact precision caged needle roller assembly eliminates separate inner and outer rings to minimize radial installation dimension. Pre-sorted high-precision needle rollers ensure uniform load distribution and low operational vibration. CP0 precision clearance controls radial runout, ideal for low-to-medium speed precision transmission. Pressed steel cage separates rollers to prevent mutual friction and enable higher limiting speed.
Selection reference: KDN.K = bare needle roller assembly; NA/NK = needle roller bearing with outer ring; RNA = outer ring needle roller bearing without inner ring.
3 Core Performance Advantages
1. Integrated design without inner & outer rings, extremely compact radial profile to save installation space.
2. CP0 precision clearance grade delivers low radial runout for low-vibration precision machinery.
3. Sorted precision needle rollers realize balanced contact stress and outstanding wear resistance.
4. Cage separates rollers to eliminate roller-to-roller sliding friction and raise allowable speed.
5. Compatible with customized housing design for integrated gearbox and transmission units.
6. Open construction supports both circulating oil lubrication and long-service grease lubrication.
4 Typical Application Fields
4.1 Precision Transmission Equipment
Small precision planetary reducers, auxiliary gear supports, servo transmission mechanisms
4.2 Automation Equipment
Linear slide hinges, rotary fixtures, miniature manipulator rotary joints
4.3 Textile & Light Industry Machinery
Spinning units, feed rollers, oscillating connecting rod supports
4.4 Construction Machinery Accessories
Miniature hinge pivots, rotary supports for hydraulic attachments
5 Assembly Specifications & Usage Guidelines
5.1 Assembly Environment & Operation Standards
Keep assembly area clean to prevent metal debris entering roller gaps. Do not strike cage directly; pressing force shall act on cage end face. Manually rotate after assembly to confirm smooth rotation without jamming or abnormal noise. Verify hardness and roughness of shaft and housing raceway.
5.2 Selection Guidance
Limited space, shaft/housing can be machined as raceway → KDN.K02508CP0
Outer ring required for direct mounting into housing → NK / RNA series needle roller bearings
Complete inner & outer rings for universal replacement → NA series needle roller bearings
5.3 Lubrication Maintenance Instruction
No pre-filled lubricant upon delivery; apply grease evenly during assembly. Circulating oil lubrication recommended for continuous medium-high speed operation. Set regular oil replenishment cycle; dry running is strictly forbidden.
5.4 Environmental Application Notes
No anti-rust coating. Apply anti-rust oil and seal tightly for long-term storage. Equip housing end covers and oil seals under dusty and humid conditions. Add buffer structure for frequent impact load conditions.
6 Fault Identification
Common failure modes: Needle roller surface pitting, shaft raceway scoring, cage deformation & fracture, sintering caused by insufficient lubrication. Once cage deformation or roller damage occurs, replace the whole assembly completely; reuse is forbidden.