Introduction

6308 bearings are widely used in various industrial applications due to their versatility and durability. Understanding their dimensions is crucial for proper selection and installation. This comprehensive guide provides a detailed overview of 6308 bearing dimensions, including industry standards, tolerances, and critical measurements.

Key Terms

Before delving into the dimensions, it is important to define some key terms related to bearings:

• Inner Diameter (d): The diameter of the bearing's inner race, which fits onto the shaft.
• Outer Diameter (D): The diameter of the bearing's outer race, which fits into the housing.
• Width (B): The distance between the bearing's inner and outer races.
• Tolerance: The permissible variation in a bearing's dimensions or characteristics.

Industry Standards

6308 bearings adhere to the international standard ISO 15:2014. This standard defines the dimensions, tolerances, and other characteristics of these bearings. The designation "6308" follows the standard numbering system, where:

• The first digit (6) indicates the bearing type (deep groove ball bearing).
• The second and third digits (30) indicate the bore diameter series (08 indicates an 8 mm bore).
• The last two digits (08) indicate the inner diameter code.

Bearing Dimensions

The dimensions of a 6308 bearing are as follows:

• Inner Diameter (d): 40 mm
• Outer Diameter (D): 68 mm
• Width (B): 16 mm

Tolerances

The tolerances for 6308 bearings are specified in ISO 15:2014. The following table summarizes the tolerances for critical dimensions:

Critical Measurements

In addition to the basic dimensions, several critical measurements are important for proper bearing selection and installation:

• Radial Clearance: The clearance between the balls and the races when the bearing is assembled. It affects the bearing's performance and life.
• Axial Clearance: The clearance between the inner and outer rings in the axial direction. It determines the bearing's axial play.
• Raceway Curvature: The shape of the raceways, which determines the bearing's load capacity and friction.
• Ball Diameter: The diameter of the balls used in the bearing.

Applications

6308 bearings are used in various applications, including:

• Automotive transmissions and gearboxes
• Industrial machinery and equipment
• Pumps and compressors
• Wind turbines
• Agricultural equipment

Effective Strategies for Bearing Selection

To ensure optimal performance and longevity of 6308 bearings, consider the following strategies:

• Follow Industry Standards: Adhere to ISO 15:2014 when selecting and specifying bearings.
• Verify Tolerances: Confirm that the bearing's tolerances meet your application requirements.
• Consider Application Loads: Choose bearings with appropriate load capacity for the anticipated operating conditions.
• Select the Right Lubrication: Lubricate bearings properly to minimize friction and wear.
• Perform Regular Maintenance: Monitor bearings regularly and replace them when necessary.

Tips and Tricks

• Use a feeler gauge to measure radial and axial clearances.
• Check for bearing noise or vibration to identify potential issues.
• Store bearings in a clean and dry environment.
• Handle bearings with care to avoid damage.

Step-by-Step Approach to Bearing Installation

1. Clean the shaft and housing surfaces before installation.
2. Apply a thin layer of lubricant to the bearing races.
3. Align the bearing with the shaft and housing.
4. Gradually tighten the mounting bolts or screws.
5. Check the bearing for proper fit and clearance.

Frequently Asked Questions (FAQs)

1. What is the inner diameter (d) of a 6308 bearing?
A. 40 mm

2. What is the tolerance for the outer diameter (D) of a 6308 bearing?
A. ±0.015 mm

3. What is the purpose of radial clearance in a bearing?
A. To accommodate thermal expansion and misalignment.

4. How should 6308 bearings be lubricated?
A. With a grease or oil that meets the bearing manufacturer's specifications.

5. What is the recommended maintenance interval for 6308 bearings?
A. The maintenance interval varies based on the application. Refer to the bearing manufacturer's guidelines.

6. What is the difference between a deep groove ball bearing and a radial ball bearing?
A. Deep groove ball bearings have deeper raceways than radial ball bearings, providing higher load capacity.

7. What are the advantages of using 6308 bearings?
A. Versatility, durability, low friction, and high load capacity.

8. How do I determine the correct size of a 6308 bearing for my application?
A. Consider the shaft diameter, load capacity, and other application requirements. Refer to the bearing manufacturer's catalog or an engineer for assistance.