Selecting the correct bearing begins with understanding its dimensions. Whether you are replacing an existing bearing, designing a new machine or sourcing components for industrial equipment, accurate size information is essential.

A bearing that matches the shaft diameter but has an incorrect outside diameter or width may lead to installation problems, excessive vibration or premature failure.

This guide explains how bearing dimensions are defined, how bearing numbering works and how to choose the correct size for your application.

Understanding Bearing Dimensions

Every standard deep groove ball bearing is identified by three basic dimensions:

• d – Bore Diameter (Inner Diameter)
• D – Outside Diameter
• B – Width

For example:

These dimensions follow international ISO standards, allowing interchangeability between manufacturers that comply with the same specifications.

Common Deep Groove Ball Bearing Series

Different bearing series are designed for different performance requirements.

6000 Series

Compact design with low friction, commonly used in electric motors, household appliances and light industrial equipment.

6200 Series

A balanced choice offering higher load capacity while maintaining good speed performance.

6300 Series

Designed for heavier radial loads in industrial machinery, pumps and gearboxes.

6700 Series

Thin section bearings developed for compact equipment where installation space is limited.

6800 Series

Lightweight bearings widely used in robotics, medical devices and automation systems.

6900 Series

Thin section bearings that provide an excellent balance between compact size and load capacity.

How to Read a Bearing Number

A bearing number is not random. It provides information about the bearing series and bore size.

For example:

6205ZZ C3

• 62 = Bearing series
• 05 = Bore code (25 mm)
• ZZ = Metal shields on both sides
• C3 = Greater-than-normal internal clearance

Understanding this coding system makes it easier to identify replacement bearings and compare products from different manufacturers.

Choosing the Correct Bearing Size

Before ordering a bearing, always confirm:

• Shaft diameter
• Housing bore
• Available installation width
• Required load capacity
• Operating speed
• Environmental conditions
• Seal type
• Clearance class

Selecting the correct dimensions is only the first step. Operating conditions are equally important.

Engineering Tip

When replacing an existing bearing, avoid selecting a replacement based solely on the bearing number printed on the shield. Verify the actual dimensions and confirm that the seal type, internal clearance and precision grade match the application’s requirements.

For OEM equipment, maintaining dimensional consistency across all bearing locations can simplify maintenance and reduce inventory costs.

Frequently Asked Questions

What are the three basic bearing dimensions?

The bore diameter (d), outside diameter (D) and width (B).

Are bearing dimensions standardized?

Yes. Most deep groove ball bearings follow ISO standards, making them interchangeable when the specifications are the same.

Can I replace a ZZ bearing with a 2RS bearing?

In many cases, yes. However, the operating environment and speed requirements should be considered before making the change.

Where can I find the dimensions of a specific bearing model?

You can refer to the individual product pages on the NKMB website, where detailed dimensions and specifications are provided for each bearing series.

Conclusion

A clear understanding of bearing dimensions is essential for selecting the right product and achieving reliable equipment performance. By combining accurate size information with proper consideration of speed, load and environmental conditions, engineers can significantly improve machine reliability and reduce maintenance costs.

NKMB offers a comprehensive range of deep groove ball bearings, thin section bearings and miniature bearings manufactured to international standards for OEM manufacturers, distributors and industrial users worldwide.