7221 ACD/P4A
7200 & 7300 Series Super Precision Angular Contact Ball Bearings
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Basic Information
Main Dimensions
Ball & Washer Dimensions
Performance
Materials
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7221 ACD/P4A Bearing Product Overview & Core Advantages
The 7221 ACD/P4A is a single-row angular contact ball bearing designed for applications demanding high precision and superior rigidity. Engineered to a P4 (ABEC-7) tolerance class, it is optimized to handle significant combined loads—simultaneous radial and axial loads—from a single direction. Its 25° contact angle provides excellent axial load capacity, making it an ideal choice for high-speed spindles and precision machinery where accuracy and reliability are paramount. The bearing is pre-lubricated and available with a preload for immediate, precise operation.
7221 ACD/P4A Bearing Model Code Explained, Specifications & Naming Convention
The model number 7221 ACD/P4A provides specific technical details:
- 72: Denotes the bearing series, indicating a specific internal design and performance profile.
- 21: Specifies the bore diameter; '21' corresponds to a 105 mm bore.
- AC: Stands for Angular Contact with a standard contact angle.
- D: Indicates that the bearing has a high internal preload for enhanced rigidity and rotational accuracy.
- /P4A: The precision class designation. P4 is equivalent to ABEC-7, signifying very high dimensional and running accuracy. The 'A' suffix often indicates a specific tolerance arrangement or contact angle.
Note: This is an open (unsealed) bearing, offering versatility for custom lubrication systems.
7221 ACD/P4A Bearing Structural Features & Performance Benefits
The design of the 7221 ACD/P4A translates directly into critical performance benefits:
- High Rigidity and Precision: The combination of a phenolic resin cage, a 25° contact angle, and an applied preload (D) ensures minimal deflection under load, providing exceptional system stiffness and precise shaft positioning essential for high-precision applications.
- Superior Load Capacity: The optimized internal geometry allows it to handle high radial dynamic load ratings (36,675 lbf) and substantial one-direction axial loads simultaneously.
- High-Speed Capability: The lightweight and robust phenolic cage reduces centrifugal forces, enabling stable operation at high limiting speeds (10,000 rpm). The open design facilitates efficient air or oil mist lubrication for optimal thermal management.
- Premium Materials: Manufactured from chrome steel for both rings and balls, the bearing ensures high durability, wear resistance, and a long operational life under demanding conditions.
7221 ACD/P4A Bearing Typical Application Areas
The 7221 ACD/P4A is specified for high-performance machinery across various industries, including:
- Machine Tool Spindles: High-speed milling, grinding, and turning centers.
- Precision Gearboxes: Applications requiring minimal runout and high positional accuracy.
- High-Frequency Motors and Spindles: Where rapid acceleration and deceleration are required.
- Industrial Pumps and Compressors: For robust performance under combined loads.
