How to Distinguish Bearings of Different Precision Levels

Precision grades are established according to ISO standards. However, due to variations in national standards, their nomenclature may differ significantly.

The precision grades of bearings are primarily classified based on dimensional accuracy and rotational accuracy. These grades are standardized into six levels: 0, 6X, 6, 5, 4, and 2, with precision increasing sequentially from grade 0. Details are as follows:

• Grade 0: Widely used in general bearing systems with rotational accuracy greater than 10 μm, such as gearboxes and feed mechanisms in ordinary machine tools, automotive and tractor transmissions, general-purpose motors, pumps, and agricultural machinery.
• Grades 6 and 5: Suitable for bearing systems requiring rotational accuracy between 5–10 μm or higher speeds, such as the front support (grade 5) and rear support (grade 6) of lathes, precision instruments, and high-precision rotating mechanisms.
• Grades 4 and 2: Used in ultra-precision systems with rotational accuracy below 5 μm or extremely high speeds, such as precision coordinate boring machines, gear systems in precision grinders, high-precision instruments, and high-speed cameras.
  Application Scenarios for Different Bearing Types by Precision Grade
  Deep Groove Ball Bearings
• P0: General industrial equipment (e.g., motors, fans, pumps, reducers) with low precision and speed requirements. P6: Automotive engines, wind turbines, precision pumps—suitable for moderate speed and precision. P5 and above High-speed turbines, industrial robots, and other high-speed, precision equipment.
  Angular Contact Ball Bearings
  P0: Ordinary rotating mechanisms with low precision demands.P6: Machine tool spindles, high-speed motors—enhances precision.P5: Precision machine tools, optical instruments—ensures high rotational accuracy and rigidity. P4 and above: Aerospace, semiconductor manufacturing—extremely high precision and speed.
  Self-Aligning Ball Bearings
• P0: Motors, agricultural machinery, automotive transmissions—tolerates moderate misalignment.P6 and above**: Precision instruments requiring stability.

Self-Aligning Roller Bearings

• P0: Heavy machinery (e.g., crushers, vibrating screens, paper mills)—handles large radial and axial loads.P6 and above: High-precision equipment (e.g., rolling mills)—ensures stability and reliability.
  Tapered Roller Bearings
• P0: Automotive transmissions, rear axles, general engineering machinery.P6: Machine tool feed systems with moderate precision needs. P5 and above: Aerospace, precision machine tool spindles—high precision and load capacity.
  Cylindrical Roller Bearings
• P0: Industrial conveyors (e.g., belt conveyor rollers).P6 and above: High-precision grinding machine spindles, CNC machine lead screw supports.
  Thrust Ball Bearings
• P0 Low axial load applications (e.g., small power tools). P6 and above: Precision lathe lead screws—high axial accuracy.
  Thrust Roller Bearings
• P0: Heavy machinery (e.g., cranes, rolling mills)—axial support.P6 and above**: Aerospace engines, precision coordinate boring machines—extreme axial accuracy and load capacity.
  Impact of Bearing Precision Grade
  Performance Effects
• Rotational Accuracy: Higher grades reduce rotational runout (e.g., high-precision spindles in machine tools).
• Friction Characteristics: Smoother surfaces and tighter tolerances minimize friction and heat, ideal for high-speed systems.
• Stiffness: Enhanced dimensional accuracy ensures stable stiffness (e.g., aerospace engine bearings).
  Lifespan Effects
• Load Distribution: Higher precision reduces stress concentration, extending lifespan (e.g., large motors).
• Wear and Fatigue Reduced sliding and friction slow wear and fatigue (e.g., precision grinder spindles).
• Sealing and Lubrication: Tight tolerances improve sealing and lubrication retention, prolonging service life.
  When selecting bearings, there are the following considerations:
  Lubrication and Heat Dissipation: For high-speed rotating bearings, in addition to choosing the appropriate bearing type, the lubrication method and heat dissipation measures need to be considered. For example, using mist lubrication or jet lubrication can effectively reduce the temperature of high-speed bearings. At the same time, selecting a lubricating oil with low viscosity and high flash point also helps to reduce heat generated by friction.
  Accuracy Matching: When selecting the bearing accuracy, it should be matched with the overall accuracy requirements of the equipment. For example, in a high-precision grinder, the spindle bearing needs to be selected with P4 class or higher accuracy, while the feed shaft bearing may meet the requirements with P5 or P6 class.
  Application Scenarios: Self-aligning bearings are often used in situations where it is difficult to ensure the coaxiality of the two bearing seat holes, such as long shaft transmissions and equipment with unstable installation bases. In large mechanical equipment such as mining machinery and metallurgical equipment, self-aligning roller bearings are widely used, which can effectively compensate for the shaft deflection caused by equipment deformation or installation errors. Working Environment
• Temperature Range: Determine the ambient temperature range in which the bearing operates. For high-temperature environments, select high-temperature-resistant bearing materials such as ceramic ball bearings and special alloy bearings, and use high-temperature-resistant grease. For low-temperature environments, choose grease with good low-temperature performance to ensure good lubrication and starting performance of the bearing at low temperatures.
• Chemical Corrosion: In environments with chemical corrosive media, such as in the chemical and electroplating industries, select stainless steel bearings or bearings with anti-corrosion surface treatment, and use anti-corrosion grease. In addition, sealing measures can be taken to prevent corrosive media from entering the bearing interior.
  Price of Bearings by Precision Grade
  Prices vary based on type, brand, and specifications. For example: Deep Groove Ball Bearings: P0 (lowest cost) to higher grades (more expensive). Angular Contact Ball Bearings: Higher precision grades incur higher costs due to manufacturing complexity. Imported brands, special materials, and large-sized bearings also command premium pricing.
  For purchasing guidance, consult LDB-Bearing, a supplier offering diverse bearing types (e.g., slewing rings, cross roller bearings, cylindrical roller bearings). Consider application-specific requirements (e.g., construction machinery, wind energy, automotive) to determine the optimal bearing type, size, and precision grade.