Needle roller bearing, characterized by their slender rollers (with a length-to-diameter ratio typically ranging from 3 to 10), offer unique advantages such as compact structure, small radial dimensions, and high load-carrying capacity. Here are specific examples of their applications across various fields, illustrating their practical value: 
- Manual Transmissions: Single-row needle roller bearing or combined needle roller and thrust ball bearing are widely used on the input, output, and intermediate shafts of transmissions. For instance, the support between the input shaft and the clutch driven plate operates in a narrow space and must bear radial loads from gear transmission (up to several thousand Newtons). The compact design of needle roller bearings fits perfectly here, while their high load capacity ensures stable power transmission during gear shifts.
- Automotive Clutches: Cage needle roller bearing without inner rings are commonly used in clutch release bearings. They directly use the outer circle of the clutch release sleeve as the raceway, saving axial space. When the driver depresses the clutch pedal, the bearing pushes the release lever along with the release fork. The rolling friction of the needles makes the disengagement process smoother, reducing pedal effort.
- Steering Systems: The connection between the steering knuckle arm and the tie rod end needs to withstand radial impact forces during steering, with limited installation space. Needle roller bearings with cages are employed here, as they can handle high-frequency impact loads while ensuring steering flexibility, often seen in mechanical steering systems of economy cars.
- Grinder Spindle: Grinding machines demand extremely high machining precision (up to 0.001mm), requiring strict control over the radial runout of the spindle. High-precision (P4 class) combined needle roller and angular contact ball bearings are used here. The needle roller part bears radial loads from the high-speed rotating grinding wheel (rotating at over 3000r/min), while the angular contact ball part counteracts axial forces. Combined with precise lubrication, these bearings ensure stable spindle operation and meet the required surface roughness of workpieces.
- CNC Lathe Feed Axes: The support of the ball screw on the feed axis must bear radial forces from the screw in a confined space while maintaining feeding accuracy. Outer ring - free needle roller bearing directly use the screw journal as the raceway. When combined with the preloading structure of the screw nut, they reduce radial space usage and minimize shaft deflection through the uniform distribution of rollers, enhancing feeding precision.
- Washing Machine Drum Shafts: During operation, washing machine drums rotate at high speeds (500-1200r/min), and the weight of clothes creates significant radial loads on the drum shaft. Double-row needle roller bearing is used for shaft end support. The two rows of rollers evenly distribute the load, and the interference fit between the bearing outer ring and the washing machine housing reduces vibration, preventing abnormal noise during operation. Their compact structure is ideal for the limited internal space of washing machines.
- Air Conditioner Compressors: The eccentric shaft of rotary compressors must withstand radial forces from refrigerant compression and operate in high-temperature environments (around 100°C). Sealed needle roller bearing with high-temperature grease are used here. The outer ring is fixed to the compressor housing, while the inner ring rotates with the eccentric shaft. The high load capacity of the rollers handles pulse loads during compression, and the sealed structure prevents refrigerant leakage and impurity ingress.
- Tractor Transmissions: Tractor transmissions endure large torques and frequent impacts (e.g., from varying plowing resistance) during operation, along with exposure to dust and mud in field environments. Reinforced needle roller bearings with double-lip seals are used on the intermediate shafts of transmissions. The sealing structure blocks intrusion, while thickened rollers and high-strength steel cages withstand impact loads, extending service life in harsh conditions.
- Combine Harvester Cutters: The moving and fixed blades of cutters move at high relative speeds (around 800r/min), and the cutter shaft must bear radial resistance from cutting straw. Outer ring - free needle roller bearings are employed here, with the cutter shaft surface quenched (HRC60) to serve directly as the raceway. This reduces the number of parts, and the line contact of the rollers distributes loads from the blades, preventing shaft deformation.
- Dental High-Speed Handpieces: Dental drills operate at extremely high speeds (up to 400,000r/min) and require stable rotation in a small space (about 10mm in diameter). Miniature needle roller bearing (with rollers only 0.6mm in diameter) is used inside, paired with ceramic rollers (lightweight and low-friction) and high-speed grease. They bear radial forces during drilling while minimizing heat and vibration, ensuring precise operation by dentists.
- Surgical Robot Joints: The joints of surgical robot arms demand high-precision rotation (positioning error <0.1mm) and lightweight structures. Thin-section needle roller bearing is used at joint shafts, with the outer ring integrated into the joint housing and the inner ring in interference fit with the rotating shaft. The uniform distribution of rollers ensures coaxiality during rotation, meeting the strict accuracy requirements of minimally invasive surgery.
