1 Model Information & Technical Parameters

Model：KDN.J02508XP0

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

XP0: Ultra-precision radial clearance group

Technical Attributes

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

Structure type: KDN.J caged needle roller assembly with optimized J-type cage window layout

Axial characteristic: Pure radial load only, axial load forbidden

Cage: High-precision pressed steel J-type optimized window cage

Coating: None

Seal: Open design, 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.J: J-type optimized window caged needle roller assembly without separate inner & outer rings; shaft and housing bore act as raceway.

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

XP0: Ultra-precision radial clearance grade. Clearance range narrower than CP0, stricter control on radial runout for high-end precision machinery.

Important reminder: This model has no solid inner and outer rings. Mating shaft and housing bore must be hardened and precision ground. Insufficient hardness and surface finish will cause early pitting, scoring or seizure. Only pure radial load permitted; axial force and continuous impact are prohibited. Open construction requires external lubrication and housing dust protection; dry running is not allowed. Never strike cage directly during installation; pressing force shall act on cage end face.

2 Structure & Operating Characteristics

Japan NMT KDN.J02508XP0 compact high-precision needle roller assembly adopts J-type cage with optimized window layout to improve roller centering stability. XP0 ultra-precision clearance features tighter radial clearance than CP0 for superior runout control. Strictly sorted needle rollers deliver uniform load distribution, smooth rotation and low noise. Pressed steel cage separates rollers to avoid mutual friction and enable stable continuous medium-high speed operation.

Selection reference:

KDN.K02508AR0 (AR0 standard clearance for general machinery)

KDN.K02508CP0 (CP0 precision clearance for mid-to-high precision equipment)

KDN.J02508XP0 (XP0 ultra-precision clearance for inspection & servo precision mechanisms)

NA/NK/RNA series: needle roller bearings with outer ring.

3 Core Performance Advantages

1. J-type optimized window cage enhances roller positioning stability and consistent rotary accuracy.

2. XP0 ultra-precision clearance provides minimal radial clearance to meet ultra-low runout and high positioning accuracy requirements.

3. Fully sorted high-precision rollers ensure balanced contact stress, smooth low-speed operation and low noise.

4. Compact ringless design minimizes radial installation space, ideal for lightweight integrated unit design.

5. Open construction supports both long-service grease lubrication and circulating oil lubrication.

6. Strict batch clearance control ensures consistent assembly precision in mass precision equipment production.

4 Typical Application Fields

4.1 High-end Precision Automation Equipment

Rotary pivots for vision inspection equipment, servo rotary tables, high-precision manipulator joints

4.2 Precision Transmission Components

Miniature precision planetary reducers, auxiliary gear supports, hinge parts of indexing mechanisms

4.3 Measuring & Laboratory Equipment

Precision fixture rotary supports, oscillating supports for miniature test mechanisms

4.4 Medical Precision Equipment Accessories

Miniature precision rotary mechanisms, light-load high-precision hinge pivots

5 Assembly Specifications & Usage Guidelines

5.1 Assembly Environment & Operation Standards

Maintain dust-free clean assembly area to prevent fine contaminants entering roller gaps. Apply pressing force to cage end face; do not strike cage sidewall. Manually rotate after assembly to verify smooth rotation without jamming or periodic abnormal noise. Check hardness and roughness of shaft and housing raceway before assembly.

5.2 Selection Guidance

General machinery, loose assembly tolerance → KDN.K02508AR0

Standard precision equipment, low vibration demand → KDN.K02508CP0

Vision inspection, servo units, demanding ultra-low radial runout → KDN.J02508XP0

Outer ring required for direct housing mounting → NK / RNA needle roller bearings

Standard replaceable bearing with complete inner & outer rings → NA series needle roller bearings

5.3 Lubrication Maintenance Instruction

No pre-filled lubricant upon delivery; apply suitable grease evenly during assembly. Circulating oil lubrication recommended for continuous long-term medium-high speed operation. Schedule regular oil replenishment; dry running is strictly forbidden.

5.4 Environmental Application Notes

No anti-rust coating. Coat anti-rust oil and seal tightly for long-term storage. Equip end covers and oil seals for dust and humid working environment. Add buffer structure under frequent impact load conditions.

6 Fault Identification

Common failure modes: Needle roller surface pitting, shaft raceway scoring, cage window deformation, seizure caused by insufficient lubrication. Replace whole assembly once cage distortion or roller damage occurs; repair and reuse are prohibited.