Cylindrical Hole Self-aligning Ball Bearing

Cylindrical bore self-aligning ball bearings are rolling bearings designed specifically to address working conditions with "insufficient installation accuracy and easy misalignment of shafts and housings". Their core advantage lies in the combination of a spherical outer ring raceway and a cylindrical inner ring bore - they can achieve automatic alignment through spherical contact to compensate for angular deviations and coaxiality errors between the shaft and housing, while also being compatible with conventional cylindrical shaft diameters without the need for special installation tools. Widely used in rotating equipment with medium-low loads and requirements for smooth operation, they serve as fundamental supporting components with "strong fault tolerance" in industrial and civil fields.​

1. Core Structure and Design Highlights​

The structural design of cylindrical bore self-aligning ball bearings is optimized around the dual requirements of "self-aligning function" and "versatility". Key components and their characteristics are as follows:​

Raceways and Rolling Elements: The outer ring features a complete spherical concave raceway, while the inner ring is machined with two rows of symmetric arc raceways. Two rows of high-purity bearing steel (GCr15SiMn) balls are placed between them, forming a "spherical-arc" contact pair. This structure allows the bearing to deflect slightly around its geometric center (self-aligning movement), minimizing additional loads caused by installation deviations. The steel balls undergo quenching and precision grinding processes, achieving a hardness of HRC 60-65, with a fatigue life over 30% longer than that of ordinary steel.​

Cages: There are two main types of cage materials based on working conditions: ① Stamped steel cages (SPCC cold-rolled steel), with a temperature resistance range of -20℃ to 200℃, high structural strength, and good impact resistance, suitable for scenarios with slight vibrations such as agricultural machinery and heavy-duty motors; ② Glass fiber-reinforced nylon 66 cages, with a temperature resistance of -40℃ to 120℃, a low friction coefficient (≤0.002), and operating noise 5-8 dB lower than that of steel cages, suitable for equipment requiring low noise such as household appliances and precision fans. Their core function is to evenly separate the two rows of steel balls to avoid collision and wear.​

Cylindrical Bore Design: The inner ring bore is a standard cylindrical shape (distinguished from tapered bore self-aligning ball bearings). Its fit tolerance with the shaft is compatible with conventional specifications (e.g., shaft tolerance k6, m6; housing tolerance H7). Only regular press-fitting tools are required during installation, without the need for additional tapered sleeve components. It is compatible with over 90% of cylindrical shaft diameters, offering far greater versatility than special bore models.​

Sealing and Protection: Three types of sealing are available to meet protection needs in different environments: open type (no seal, requiring external lubrication, suitable for clean and dry environments), double-sided steel shielded type (suffix ZZ, excellent dust resistance, with a grease retention rate of 90%), and double-sided rubber sealed type (suffix 2RS, IP52 dust and water resistance, suitable for humid and dusty scenarios such as water pumps and textile machines).​

2. Key Performance Parameters and Advantages​

The performance of cylindrical bore self-aligning ball bearings focuses on "self-aligning capability" and "working condition adaptability". Key parameters and advantages are shown in the table below:​

3. Typical Models and Specification System​

Cylindrical bore self-aligning ball bearings follow ISO standards, with domestic models prefixed with "12", "13", "22", and "23" (Series starting with "1" are light series, featuring narrow width and low load; Series starting with "2" are medium series, featuring wide width and high load). Examples of typical model specifications are as follows:

Note: Meanings of model suffixes - "2RS" = double-sided rubber sealed, "ZZ" = double-sided steel shielded, no suffix = open type; "K" indicates a tapered bore (not a cylindrical bore), so attention should be paid to distinction during selection.​

4. Application Fields and Scenario Matching​

Due to their "self-aligning and fault-tolerant" characteristics, cylindrical bore self-aligning ball bearings are mainly suitable for scenarios where "installation accuracy is difficult to control" or "misalignment is prone to occur". Specific fields and selection logic are as follows:

5. Usage and Maintenance Precautions​

Load Control: The actual radial load should be controlled within 1/3 of the basic dynamic load rating, and the axial load should not exceed 1/2 of the radial load to avoid premature failure caused by excessive extrusion between steel balls and raceway edges.​

Installation Points: Avoid tapping the inner and outer rings of the bearing during installation (it is recommended to apply force evenly with a sleeve). The coaxiality error between the shaft and housing should be ≤0.1mm (although the bearing can self-align, excessive deviation will increase friction loss). An interference fit (e.g., k6) should be used between the inner ring and the shaft, and a transition fit (e.g., H7/js6) between the outer ring and the housing.​

Lubrication Specifications: Open-type bearings require regular replenishment of lithium-based grease (replenish once every 300 hours for speeds below 10,000 r/min). Sealed bearings are pre-greased at the factory and do not require disassembly and grease replenishment during their service life. Only under high-temperature working conditions (≥150℃) should the grease condition be checked once every 100 hours.​

Failure Early Warning: If there is a "jamming feeling", "continuous abnormal noise (e.g., 'clunking sound')", or the housing temperature exceeds 75℃ during operation, stop the machine immediately for inspection. The cause may be excessive self-aligning angle, insufficient lubrication, or foreign object intrusion.​

Storage Requirements: Store horizontally in a dry and well-ventilated environment (humidity ≤60%, temperature 5℃-30℃). Avoid long-term stacking (stacking height should not exceed 5 layers) to prevent bearing deformation that affects the self-aligning function.

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