Bearing clearance is a fundamental concept in mechanical engineering and the maintenance of rotating systems. Although often overlooked, it plays a direct role in the performance, durability, and safety of industrial machinery.
In this article, we’ll explain what bearing clearance is, the most common types (such as C3 and C4), and how this characteristic influences the operation of your equipment.
1. What is Clearance in a Bearing?
Clearance is the distance between the rolling elements (balls or rollers) and the inner and outer rings of the bearing when it is not in operation and no load is applied.
This “gap” allows the bearing enough mobility to absorb thermal expansion, misalignment, and dynamic loads — common factors in industrial environments.
🔧 Technically, this feature is linked to the mechanical tolerance of the assembly and the ideal fit for the shaft and housing.
2. Types of Clearance: Radial and Axial
There are two main types of clearance:
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Radial clearance – movement of the inner ring relative to the outer ring in a direction perpendicular to the axis of rotation.
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Axial clearance – movement of the rings in a direction parallel to the axis.
Radial clearance is the most common and is typically specified in bearing catalogs. It is classified into groups according to international standards (such as ISO 5753 and ABNT NBR 15403-1).
3. Clearance Classifications: Understanding C2, CN, C3, C4, and C5
Radial clearance is grouped as follows:
| Code | Clearance Type | Typical Application |
|---|---|---|
| C2 | Less than normal | High-precision equipment with low expansion |
| CN (or C0) | Normal clearance | General-purpose, standard applications |
| C3 | Greater than normal | High-temperature or high-speed environments |
| C4 | Greater than C3 | Heavy loads, significant thermal expansion |
| C5 | Much greater than C4 | Special applications, heavy machinery |
⚠ Important: Incorrect clearance selection can compromise lubrication, cause excessive noise, lead to premature wear, or even bearing failure.
4. How Clearance Impacts System Performance
The correct clearance ensures smooth and reliable bearing operation. Here’s how it directly impacts performance:
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Performance: Proper clearance reduces excessive friction and prevents seizure at high temperatures.
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Durability: Prevents accelerated wear and extends bearing lifespan.
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Safety: Incorrect clearance can cause vibrations, overheating, and catastrophic failures.
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Energy Efficiency: Less friction means lower energy consumption.
Excessive clearance:
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Causes increased vibration, instability, and noise.
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Reduces precision and allows lubrication to dissipate faster.
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Leads to premature wear and potential equipment failure.
Insufficient clearance:
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Can cause the bearing to seize as temperatures rise.
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Increases internal friction, heat, and risk of severe structural damage.
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May cause sudden equipment stoppage and component breakage.
5. When to Choose C3 or C4?
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Choose C3 for bearings operating at high speeds or in elevated temperatures — e.g., electric motors, industrial fans, centrifugal pumps.
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Choose C4 for heavy machinery that generates significant heat or experiences intense thermal expansion — e.g., steel mills, crushers, extruders.
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For precision applications with low thermal expansion and strict dimensional accuracy, opt for smaller clearances (C2) or normal clearance (CN).
6. How to Ensure the Correct Fit in Practice
Clearance selection should consider:
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Shaft and housing dimensions
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Application thermal conditions
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Load type (radial, axial, combined)
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Operating speed
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Lubrication type
⚠ Incorrect assembly — such as excessive tightening or misalignment — can nullify the correct clearance and compromise performance.
7. VICAN Helps You Choose the Right Bearing
VICAN Bearings offers specialized technical support to help you select the ideal bearing clearance for your application.
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Expert team for application analysis
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Fast delivery throughout Brazil
Bearing clearance is not a minor detail — it is a key factor in the success of your mechanical project.
Understanding clearance types and their applications helps avoid failures, reduce maintenance costs, and ensure maximum system performance.
When in doubt, count on VICAN.
VICAN — Performance and Durability
