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Category
NA6904
Needle roller bearings utilize cylindrical rollers with a length-to-diameter ratio exceeding 4:1. This “needle-like” geometry enables exceptional radial load capacity within extremely compact cross-sections, providing superior space efficiency compared to ball bearings of equivalent dimensions.
Needle Roller Bearings
| ISO | NA6904 | |
| Bore diameter | d | 20 mm |
| Raceway diameter inner ring | F | 25 mm |
| Outside diameter | D | 37 mm |
| Width | B | 30 mm |
| Basic dynamic load rating | C | 17.5 kN |
| Basic static load rating | C0 | 24.2 kN |
| Limiting speed | 7700 r/min | |
| Mass bearing | 0.141 kg | |
Structural Breakdown
Key components include:
- Outer Ring: Typically with raceway (cageless types omit outer ring)
- Needle Rollers: Precision-ground rollers transmitting load via line contact
- Cage: Brass/steel/polymer material spacing rollers (cageless types exclude cage)
- Inner Ring: Optional component (e.g., NA-type with inner ring, RNA-type without)
Classification System
- By Design: Full complement (high load), caged (high-speed capable)
- By Function: Radial, thrust, combination bearings
- Special Types: Flanged (axial positioning), aligning (misalignment compensation)
Technical Advantages
| Feature | Engineering Benefit |
| Ultra-slim section | Saves 60% radial space |
| High load density | 300% higher capacity vs. balls |
| Shock resistance | Line contact distributes stress |
| Rotation accuracy | ±0.03mm for precision systems |
| Note: Speed limitation varies by cage material |
Industry Applications
- Automotive: Transmissions (e.g., JTEKT NK17/20), connecting rods
- Robotics: Articulated joints (full complement type prevalent)
- Aerospace: APU rotor support bearings
- Medical: CT scanner gantry rotation (MRI-safe versions)
- Construction: Hydraulic pump drives (Timken TOR 47)
Environmental Adaptation
| Condition | Recommended Solution |
| High temperature | Ceramic-coated rollers + special cages |
| Corrosive media | Full stainless steel (SS suffix) |
| Contaminated areas | Double-lip contact seals (2RS) |
| Ultra-high speed | Polymer cages + oil-air lubrication |
Contact Us
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