Bearings are integral components in machinery, enabling parts to move smoothly with minimal friction. Selecting the right bearing is crucial for the Reali-Slim® Thin Section Bearings performance and longevity of the machine. Bearings size charts serve as essential tools, providing detailed specifications and dimensions that help in choosing the appropriate bearing for specific applications.

What Are Bearings?

Bearings are mechanical elements that reduce friction between moving parts and support radial and axial loads. They come in various types, including ball bearings, roller bearings, and needle bearings, each designed for specific applications and load types. Proper selection is vital to ensure efficient operation, minimize wear, and extend the life of the machinery.

Importance of Bearings Size Charts

Bearings size charts are comprehensive tables listing the dimensions and specifications of different bearing types. These charts are indispensable for engineers, technicians, and maintenance personnel when selecting bearings for machinery. They provide detailed information on:

  • Inner Diameter (ID): The bore size where the shaft is inserted.
  • Outer Diameter (OD): The external dimension of the bearing.
  • Width (W): The thickness of the bearing.
  • Load Ratings: The maximum radial and axial loads the bearing can withstand.
  • Speed Ratings: The maximum operational speed.

Key Elements of a Bearings Size Chart

  1. Bearing Type: Identifies the type of bearing (e.g., deep groove ball bearing, spherical roller bearing).
  2. Dimensions: Detailed measurements including ID, OD, and width.
  3. Tolerance Levels: Precision levels and allowable deviations in dimensions.
  4. Load Ratings: Both dynamic and static load ratings indicating the maximum load capacity.
  5. Speed Ratings: Maximum rotational speeds for optimal performance.
  6. Material Specifications: Information on the materials used, such as steel, ceramic, or hybrid materials.

How to Read a Bearings Size Chart

Reading a bearings size chart involves understanding the nomenclature and the standard measurement units used. Here’s a breakdown of how to interpret the chart:

  1. Bearing Code: Typically a series of numbers and letters denoting the bearing type, dimensions, and design.
  2. ID, OD, W: These columns list the inner diameter, outer diameter, and width, usually in millimeters or inches.
  3. Load Ratings: Expressed in Newtons (N) or pounds-force (lbf), these figures indicate the bearing’s load-carrying capacity.
  4. Speed Ratings: Given in revolutions per minute (RPM), indicating the maximum operational speed.
  5. Tolerance and Fit: Descriptions of the precision and fit required for optimal performance.

Example of a Bearings Size Chart Entry

Bearing Type Inner Diameter (mm) Outer Diameter (mm) Width (mm) Dynamic Load Rating (N) Static Load Rating (N) Max Speed (RPM)
6205 25 52 15 14,000 7,800 15,000

Selecting the Right Bearing

When selecting a bearing, consider the following factors:

  • Load Type: Determine if the bearing will primarily support radial, axial, or combined loads.
  • Speed Requirements: Ensure the bearing can operate at the desired speeds.
  • Environmental Conditions: Consider temperature, exposure to contaminants, and lubrication needs.
  • Fit and Clearance: Choose the right fit for the shaft and housing to avoid excessive play or binding.


Bearings size charts are vital tools in the selection and maintenance of bearings in various machinery and applications. By understanding how to read these charts and considering key factors such as load, speed, and environmental conditions, you can ensure the optimal performance and longevity of your bearings. Whether you are an engineer, technician, or a maintenance professional, familiarizing yourself with bearings size charts will enhance your ability to make informed decisions and maintain efficient operations.