Product Overview
51108 Thrust Ball Bearings YJJ022 are one-way axial load-bearing components designed for high-precision, low-speed to medium-speed applications. The “51108” is the standard model number (per ISO 104), indicating a single-row thrust ball bearing with an inner diameter (d) of 40mm, outer diameter (D) of 60mm, and thickness (T) of 13mm— critical dimensions for compatibility with standard shafts and housings. The “YJJ022” is a custom specification that enhances the bearing’s performance: it includes a reinforced brass cage and a high-temperature lubricant pre-filled at the factory, making the bearing suitable for applications with mild temperature fluctuations (up to 120°C). Unlike two-way thrust bearings, these one-way bearings excel at handling unidirectional axial loads (e.g., the downward thrust of a crane hook or the upward thrust of a car transmission shaft), with a compact design that saves installation space in tight mechanical assemblies. They are widely used in automotive, construction, and industrial equipment due to their high load capacity and easy maintenance.
Product Features
Dimensional Precision & Load Capacity
Manufactured to P5 precision grade, the bearings have tight dimensional tolerances: inner diameter tolerance (d) of 0 to -0.011mm, outer diameter tolerance (D) of 0 to +0.018mm, and thickness tolerance (T) of 0 to -0.015mm. This precision ensures smooth contact between the balls and raceways, reducing vibration (≤ 50dB at 1,800 rpm) and improving equipment stability. The static axial load capacity is 105 kN, and the dynamic axial load capacity is 48 kN— sufficient to handle heavy loads like the weight of a 10-ton crane hook (when used in pairs for safety).
Material & Cage Design
The raceways (shaft washer and housing washer) are made of chrome steel (GCr15), heat-treated to HRC 60-64 for wear resistance, while the rolling balls use high-carbon chromium steel (SUJ2) for high impact resistance (can withstand minor shocks up to 15 kN). The YJJ022 specification includes a brass cage (H62 brass)— more durable than plastic cages (resists temperatures up to 150°C) and less prone to deformation under load compared to steel cages. The brass cage has a pocket design that evenly spaces the balls (10 balls total for 51108), reducing friction between balls by 25% and preventing ball skidding during sudden load changes.
Pre-Lubrication & Sealing
Factory-pre-lubricated with high-temperature lithium grease (NLGI 2), the bearings are ready to use out of the box— no additional lubrication is needed for the first 6 months of operation. Optional PTFE seals (available as an accessory) can be installed on the housing washer to prevent dust and moisture ingress, extending service life by 30% in dusty environments (e.g., construction sites). The grease is compatible with most industrial lubricants, allowing easy replenishment during maintenance.
Usage
Industry Applications
Automotive Transmissions
In manual and automatic car transmissions, these bearings support the axial thrust of the input shaft (generated when shifting gears). The 40mm inner diameter fits standard transmission shafts, while the 105 kN static load capacity handles the thrust from gear meshing (up to 80 kN during hard shifting). The brass cage resists the high temperatures (up to 120°C) inside the transmission, preventing cage melting— a common issue with plastic cages in older transmission designs.
Construction Machinery
Used in crane hoists and excavator bucket cylinders, the bearings handle the axial load from lifting heavy objects (e.g., a 5-ton steel beam). The one-way design ensures the load is supported in the downward direction (preventing the hoist from slipping), while the P5 precision reduces vibration during lifting— critical for maintaining control of the load. The pre-lubricated grease withstands the dusty, dirty environment of construction sites, reducing the need for frequent maintenance.
Printing & Packaging Machinery
In printing press impression cylinders and packaging machine sealing rollers, the bearings support the axial thrust from the cylinder’s pressure (e.g., 20 kN of pressure to seal plastic bags). The low vibration (≤ 50dB) ensures the printing cylinder remains stable, preventing print misalignment (e.g., smudged text on labels). The compact design (13mm thickness) fits into the narrow space between the cylinder and machine frame, simplifying the mechanical layout.
Operational Conditions
The bearings operate optimally at speeds between 500 rpm and 2,000 rpm— speeds above 2,500 rpm may cause overheating (temperature > 80°C) and reduce load capacity by 15%. They handle temperatures from -20°C to 120°C (standard model) or up to 150°C (with brass cage). Avoid axial misalignment of more than 0.5mm— misalignment can cause uneven ball contact, leading to raceway damage and premature failure.
FAQ
Installation & Maintenance
How to install the bearing correctly?
Clean the shaft and housing washer seats with acetone to remove oil or rust— any debris can cause misalignment.
Press the shaft washer (inner washer) onto the shaft until it is flush with the shaft shoulder— use a bearing press (not a hammer) to avoid damaging the washer.
Place the rolling balls and brass cage onto the shaft washer (ensure balls fit into the cage pockets).
Lower the housing washer (outer washer) onto the balls, aligning it with the housing seat— ensure the washer is perpendicular to the shaft (use a square to check).
Tighten the housing bolts to a torque of 15-20 N·m (for M8 bolts) to secure the housing washer in place.
When should lubrication be replenished?
For light use (e.g., printing presses, 8 hours/day operation), replenish grease every 6-8 months; for heavy use (e.g., construction cranes, 24 hours/day operation), replenish every 3-4 months. To replenish: 1) Clean the grease nipple (if equipped) with a cloth. 2) Inject grease until it oozes from the bearing’s sides (indicates full filling). 3) Wipe away excess grease to prevent dust buildup.
Performance & Compatibility
Can this bearing be used for two-way axial loads?
No— it is a one-way thrust bearing and only supports axial load in the direction of the shaft washer (toward the housing washer). For two-way loads, install two 51108 YJJ022 bearings back-to-back (shaft washers facing each other) or use a two-way thrust bearing (e.g., model 52108).
What is the difference between the YJJ022 specification and standard 51108 bearings?
The standard 51108 typically uses a plastic cage (nylon 66) and no pre-lubrication, while the YJJ022 uses a brass cage (more durable, high-temperature resistant) and is factory-pre-lubricated with high-temperature grease. The YJJ022 also has a slightly smoother raceway finish (Ra ≤ 0.015μm vs. Ra ≤ 0.02μm for standard models), reducing friction and noise.
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