Bearing Tolerances: The Key to Long-Lasting Equipment

Bearing Tolerances: The Key to Long-Lasting Equipment

by Kevin Sweeney
12 April, 2023
5 min read

Bearing tolerances is an essential aspect of engineering design, and their significance cannot be overstated. Bearings play a crucial role in the proper functioning of rotating equipment, and their proper selection and installation are crucial to achieving long-lasting equipment performance. This article aims to explore the importance of bearing tolerances in equipment longevity and the factors that affect their tolerances.

Types of Bearing Tolerances

Bearing tolerances are the allowable limits of deviation from the ideal size, shape, and position of a bearing. The International Organization for Standardization (ISO) has established various standards for bearing tolerances. Bearing tolerances include bore, outer diameter, width, radial clearance, axial clearance, and running accuracy. Radial clearance refers to the amount of play between the inner and outer races of a bearing. Axial clearance refers to the amount of play in the axial direction. Running accuracy refers to the degree of precision of the bearing’s rotational movement.

ISO tolerances for bores
ISO tolerances for bores

ES = upper deviation · EI = lower deviation · IT = fundamental tolerance · (H = fundamental deviation)

Zero line · Housing · Clearance fit · Transition fit · Interference fit

Factors Affecting Bearing Tolerance

Bearing tolerances are influenced by several factors, including material, geometry, and load conditions. Material properties such as hardness, strength, and fatigue resistance affect the bearing’s ability to withstand loads and stresses. How to choose the appropriate material, read our article.

The geometry of the bearing, including its shape, size, and surface finish, affects its ability to distribute and support loads evenly. Load conditions such as speed, temperature, and vibration also affect bearing tolerances by inducing stress and wear.

To achieve optimal performance, bearing tolerances must be carefully selected and designed to suit the specific operating conditions of the equipment. For example, a high-speed spindle bearing requires tighter tolerances to reduce friction and prevent heat buildup, while a heavy-duty bearing used in a mining application may require looser tolerances to accommodate large shock loads.

How to Measure Bearing Tolerances

Measuring bearing tolerances is a critical step in ensuring proper performance and longevity of equipment. There are several methods for measuring bearing tolerances, including dimensional inspection, surface roughness analysis, and vibration analysis.

Dimensional inspection involves measuring the dimensions of the bearing components and comparing them to the design specifications. To verify that the bearing meets the required tolerances for size, shape, and concentricity. Surface roughness analysis involves measuring the roughness of the bearing surfaces and comparing them to the required specifications to ensure that the bearing surfaces are smooth and free from defects that can lead to premature wear.

Vibration analysis involves measuring the vibration levels of the bearing during operation and comparing them to acceptable levels to detect any abnormal vibration patterns that may indicate wear or damage to the bearing components.


Bearing tolerance plays a critical role in the long-term performance and reliability of mechanical equipment. Through careful consideration of factors such as material selection, manufacturing processes, and design specifications, engineers can ensure that bearings are properly matched to their intended applications and are able to withstand the anticipated loads and stresses. By minimizing variations in tolerances and achieving precise fit and alignment, equipment designers can improve operational efficiency, reduce maintenance costs, and extend the service life of their machines. Therefore, it is crucial for engineers to prioritize the selection and implementation of appropriate bearing tolerances to optimize the performance and durability of their equipment.

If you have any questions about bearing tolerances, please Contact us.

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Written by

Kevin Sweeney

Founder and CEO at Pacific International Bearing Sales Inc (PIB)
Education: BS Business and Economics California State University Hayward Ca
CBS (Certified Bearing Specialist)

My role with Pacific International Bearings (PIB) is currently CEO. Since 1976, I have been deeply involved in the bearing industry, working in manufacturing sales at NTN Bearing and subsequently in Bearing Distribution. Before establishing PIB in 1990, I gathered valuable experience in bearing manufacturing and distribution. The last 45 + years in the bearing industry have been both rewarding and challenging, assisting customers across a large number of diverse bearing applications.
Outside of the bearing industry, my interests are family, woodworking, motorcycling, cars, gardening, and golf.
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