Bearing Tolerance Chart Explained

The precise world of bearings revolves around detailed measurements and exacting specifications. One critical tool for ensuring optimal bearing performance is the bearing tolerance chart. This vital reference provides insights into how bearings can fit and function within machinery, underscoring the importance of accurate measurements in bearing applications.

What is a Bearing Tolerance Chart?

A bearing tolerance chart is a detailed guideline, outlining the permissible limits of variation in a bearing's dimensions. It serves to aid in the selection of the right bearings for specific applications, detailing key parameters such as inner and outer diameters, radial play, and axial play.

Why is it Important to Consult a Bearing Tolerance Chart?

Accurate interpretation of a bearing tolerance chart is key to achieving a proper bearing fit and function. It helps avoid premature bearing failure, which can result from improper fit, thereby enhancing the performance and efficiency of the machinery.

How to Interpret a Bearing Tolerance Chart

Much like learning what bearing numbers mean, interpreting a bearing tolerance chart requires:

• Tolerance Class: Each row usually represents a specific bearing type within a tolerance class, ranging from high to low precision, each suitable for various applications.
• Dimensional Values: Tolerance charts present dimensions like ID, OD, and radial and axial play, indicating acceptable measurement ranges for bearings.
• Radial Play and Axial Play: These values denote the bearing's permissible 'play' in radial and axial directions, crucial in applications with substantial load or movement along these axes.
• Match to Application Requirements: The right bearing with the appropriate tolerance class can make all the difference. Table 1 below provides a comprehensive overview of the required performance, corresponding applications, and the suitable tolerance class for different scenarios.

Table 1 High precision bearing applications

Bearing Tolerance Chart

Bearing tolerances, as well as the allowable values for the boundary dimensions and operational accuracy of bearings, are specified.

The rules governing these tolerances are set out in JIS B 1514-1, -2, and -3, addressing roller bearings with a focus on part 1: radial bearings, part 2: thrust bearings, and part 3: permissible chamfer dimensions. These JIS regulations are based on the corresponding ISO standards.

Bearing tolerances are categorized into six classes: 0, 6X, 6, 5, 4, and 2, with precision increasing with the class number.

Class 0 bearings suffice for regular use, while Class 5 or higher bearings are needed for intense conditions, as shown in Table 1.

These tolerances, conforming to ISO standards, may have different names globally. Table 2 outlines specific tolerances per bearing class and pertinent bearing organizations.

Standards and organizations concerned with bearings include:

• JIS : Japanese Industrial Standard
• BAS : The Japan Bearing Industrial Association Standard
• ISO : International Organization for Standardization
• ANSI : American National Standards Institute, Inc.
• ABMA : American Bearing Manufactures Association
• DIN : Deutsches Institut für Normung
• BS : British Standards Institution
• NF : Association Francaise de Normalisation

Table 2 Bearing type and tolerance class

To illustrate the precision of dimensions and operation for various bearing types, we'll use the example of radial bearing tolerances, excluding tapered roller bearings. See Table 3.

Table 3 JIS B 1514-1: Radial bearing tolerances (tapered roller bearings excluded)

(1) Inner ring (bore diameter)

(2) Inner ring (running accuracy and width)

(3) Outer ring (outside diameter)

(4) Outer ring (running accuracy and width)

Accuracies for dimensions and running of other bearing types are listed in:

• Table 4 ANSI/ABMA: Tolerances for measuring instrument ball bearings (inch series)

(1) Inner ring and outer ring width

(2) Outer ring

• Table 5 JIS B 1514-1: Tolerances for metric series tapered roller bearings

(1) Inner ring

(2-1) Outer ring

(2-2) Outer ring

(3) Assembled bearing width and effective width

• Table 6 BAS 1002: Tolerances for metric series double-row and four-row tapered roller bearings (class 0)

(1) Inner ring, outer ring width and overall width

(2) Outer ring

• Table 7 ANSI/ABMA 19: Tolerances and permissible values for inch series tapered roller bearings

(1) Inner ring

(2) Outer ring

(3) Radial runout of assembled bearing inner ring/outer ring

(4) Assembled bearing width and overall width

• Table 8 Tolerances for metric J series tapered roller bearings

(1) Bore diameter and width of inner ring and assembled bearing width

(2) Outside diameter and width of outer ring and radial runout of assembled bearing inner ring/ outer ring

• Table 9 JIS B 1514-2: Tolerances for thrust ball bearings

(1) Shaft race and central race

(2) Housing race

(3) Bearing height and central race height

• Table 10 JIS B 1514-2: Tolerances for spherical thrust roller bearings (class 0)

(1) Shaft race

(2) Housing race

• Table 11 JIS B 1514-1: Tolerances and permissible values for tapered bores of radial bearings (class 0)

(1) Basically tapered bore (taper 1:12)

(2) Basically tapered bore (taper 1:30)

• Table 12 Tolerances and permissible values for flanged radial ball bearings

(1) Tolerances on flange outside diameters

(2) Tolerances and permissible values on flange widths and permissible values of running accuracies relating to flanges

Conclusion

Understanding and effectively using a bearing tolerance chart is integral to successful bearing applications and optimal machinery performance. It’s not just about the right fit, but also about enhancing efficiency and extending bearing service life. At Lily-Bearing, we are committed to providing high-quality bearings with precise tolerances to meet your diverse application needs. Through accurate bearing selection using our comprehensive bearing tolerance chart, you can achieve significant improvements in machinery performance.