Direct answer: A bearing clearance chart compares internal clearance classes such as CN, C3, C4 and C5. CN is normal clearance for many standard applications. C3 has greater internal clearance and is often used when interference fit, heat or higher speed will reduce running clearance. C4 and C5 provide even more clearance and should only be used when the machine design requires it.

Quick Reference: Bearing Clearance Application Chart

If you are unsure which code to specify, check this table against your operating conditions.

Class	Description	Operating Conditions	Typical Applications
C2	Tight (Less than Normal)	Low noise, high precision, low heat. Requires very precise machining of shaft/housing.	Precision Spindles, Gyroscopes, Micro-motors.
CN (C0)	Normal (Standard)	Standard temperatures (-20°C to +100°C) and normal fits. The default choice.	Conveyors, Standard Fans, Water Pumps, Agricultural Machinery.
C3	Loose (Greater than Normal)	High speeds, moderate heat, or heavy press fits. Allows for thermal expansion.	Electric Motors, Motorcycle Engines, Automotive Alternators.
C4	Extra Loose	High heat or severe vibration.	Vibrating Screens, Mining Crushers, Paper Mill Dryers.
C5	Extra Extra Loose	Extreme heat environments.	Kiln Cars, Steel Mill Rollers, High-Temp Ovens.

Engineering Note: Never use C4 or C5 bearings in a standard application “just to be safe.” Excessive clearance will lead to vibration, noise, and reduced load capacity.

Here is the golden rule every buyer must know:

Internal clearance is NOT the same as “precision” or “tolerance”. A loose bearing (C3/C4) can still be high precision (P5/P6).

If you install a standard clearance bearing into a high-temperature motor thinking it is “more precise,” it will seize up and fail. We created this guide to help you avoid these costly purchasing errors and ensure you order the right part the first time:

• Radial vs. Axial: Understanding the direction of movement.
• Decoding the Codes: When to choose C2, CN, C3, or C4.
• Selection Charts: Full ISO 5753 reference tables for quick lookups.

What is Radial vs. Axial Clearance?

Internal clearance is divided into two directions:

• Radial Internal Clearance: The total movement of the inner ring up and down (vertical) relative to the outer ring. This is the primary specification defined by ISO standards.

• Axial Internal Clearance: The total movement of the inner ring side-to-side (horizontal) relative to the outer ring.

Decoding the Codes: CN, C3, and C4

Manufacturers use standardized suffix codes to identify clearance classes. The scale moves from “Tight” to “Loose”:

• C2 (Tight): Clearance is smaller than normal. Used in high-precision machine tools where vibration must be minimized. Risk: Easily overheats if not installed perfectly.

• CN / C0 (Normal): The standard clearance. Usually, this is not marked on the bearing (e.g., a “6205” bearing has CN clearance). Suitable for standard applications with normal temperatures.

• C3 (Loose): Clearance is larger than normal. This is the most common specification for Electric Motors and pumps.

• C4 / C5 (Extra Loose): For extremely high-speed or high-temperature environments (like vibrating screens or kilns).

How to Read a Bearing Clearance Chart: CN vs C3 vs C4

Start by identifying the bearing type and bore diameter, because clearance values are not the same for every bearing family or size range. Then check the required clearance class: CN, C3, C4 or another suffix specified by the machine manufacturer.

Next, review the factors that reduce or change operating clearance. Interference fit on the shaft can expand the inner ring. Interference fit in the housing can compress the outer ring. A hotter inner ring can also reduce running clearance during operation. For this reason, a bearing that looks “loose” before installation may be correct after mounting and heating.

C3 does not mean higher quality. It means greater internal clearance than CN. A C3 bearing may be suitable when mounting fit or operating temperature reduces clearance, but it may create extra noise or vibration if used where normal clearance is required.

For purchasing or replacement work, do not select C3 or C4 just to be safe. Confirm the complete bearing model, bore size, speed, load direction, shaft and housing fit, temperature, lubrication, and machine type before ordering.

Why Choose C3 (Loose) Clearance?

Customers often ask: “Why would I want a loose bearing? Doesn’t that mean low quality?”

The answer lies in the difference between Initial Clearance (what you buy) and Operating Clearance (what happens when running). Two factors will “eat up” the clearance during operation:

1. Interference Fits: When you press a bearing onto a shaft, the inner ring expands. When you press it into a housing, the outer ring shrinks. This compression reduces the internal space.

2. Thermal Expansion: In operation, the inner ring (shaft) is usually hotter than the outer ring. Steel expands when hot, further closing the gap.

The Rule of Thumb: If you are using a tight interference fit or running at high speeds/temperatures (like in an electric motor), you need C3 to allow for this expansion. If CN clearance is used in an application where fit and heat reduce clearance too much, operating clearance may become insufficient, causing heat, friction and possible failure.

When to use C3?

In the B2B market, C3 is the most commonly requested “non-standard” clearance. But why?

The answer is simple: C3 provides room for expansion. When a bearing runs at high speeds, the friction generates heat, causing the inner ring to expand. Additionally, if the bearing is press-fitted onto the shaft (interference fit), the inner ring expands further.

You generally need a C3 clearance if your application involves:

• Electric Motors: High speeds generate heat; C3 is the industry standard for motor bearings.

• Heavy Interference Fits: A tight press fit can reduce a significant portion of the initial internal clearance. The exact reduction depends on bearing size, fit, material and mounting conditions. C3 compensates for this.

• High Vibrations: Equipment like crushers or gearboxes often benefit from the extra flexibility.

• Temperature Gradients: When the shaft gets much hotter than the housing (e.g., in internal combustion engines).

Bearing clearance standard quick reference table

Below are the standard clearance values (in microns, μm) for Deep Groove Ball Bearings and Cylindrical Roller Bearings.

How to read these tables:

1. Identify your bearing’s Bore Diameter (d).

2. Choose your clearance class (e.g., C3).

3. The value shows the minimum and maximum gap in microns.

Conclusion

Choosing between C3 and Normal clearance is a balancing act. Too little clearance leads to heat and seizing; too much clearance leads to noise and vibration.

Not sure which clearance your application needs? Don’t guess. [Contact TFL Bearing’s Engineering Team] today. We can help you calculate the precise fit and clearance for your machinery.

FAQ

Q: What does C3 mean on a bearing?

A: C3 means the bearing has greater internal clearance than CN, or normal clearance. It does not mean the bearing is higher quality; it means the internal clearance is larger before mounting.

Q: What is the difference between CN and C3 bearing clearance?

A: CN is normal internal clearance for many standard applications. C3 has more clearance and is often used when shaft fit, housing fit, heat or higher speed will reduce the final operating clearance.

Q: Should I choose C3 bearing clearance instead of CN?

A: Not always. C3 is useful when extra clearance is needed after mounting and heating, but it can increase noise, vibration or load concentration if the application only requires CN clearance.

Q: What is the difference between C3 and C4 bearing clearance?

A: C4 has more internal clearance than C3. C4 is usually used for applications with higher temperature, vibration or special operating conditions, and should not replace C3 unless the machine specification requires it.

Q: How do I use a bearing clearance chart?

A: First identify the bearing type and bore size, then compare the clearance class such as CN, C3, C4 or C5. After that, check shaft fit, housing fit, speed, temperature, load and lubrication because these factors affect final operating clearance.