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Angular Contact Ball Bearings: Understanding P4 vs. P5 Precision Grades

2025-05-03

Choosing the right angular contact ball bearings is important for machines that require high precision and performance, such as CNC machines, robots, and aerospace equipment. Two common high-precision grades are P4 and P5. Let’s take a closer look at what they mean and how to choose between them.

1. What Are Bearing Precision Grades?

According to the international standard ISO 492:2014, angular contact ball bearings are divided into five precision levels, from lowest to highest:

P0 (standard)
P6
P5 (high precision)
P4 (ultra-high precision)
P2 (extremely high precision)

In this guide, we focus on P4 and P5, which are commonly used in industrial applications requiring high performance.

2. Main Differences Between P4 and P5 Bearings

Feature	P4 Bearings	P5 Bearings
Precision Level	Ultra-high precision	High precision
Dimensional Tolerance	Very tight (e.g., inner diameter ±1.5 μm)	Slightly looser (e.g., inner diameter ±2.5 μm)
Rotational Accuracy	Very low runout (≤3 μm radial, ≤4 μm axial)	Slightly higher runout (≤5 μm radial, ≤6 μm axial)
Surface Finish	Extremely smooth (Ra ≤0.05 μm)	Smooth, but not as fine (Ra ≤0.1 μm)
Manufacturing Process	Uses special grinding and polishing with strict quality control	Standard precision methods with moderate checks

3. Common Applications

Use P4 Bearings When:

You need extreme accuracy (like in medical devices or optical systems)
The machine runs at very high speeds (over 15,000 RPM)
Low friction and heat are important

Examples:

High-speed spindles
Semiconductor manufacturing equipment
Precision grinding machines
Aerospace testing devices

Use P5 Bearings When:

You need good precision but not the highest level
Your budget is limited, but you still want reliable performance

Examples:

Industrial robots
CNC machining centers
High-speed packaging machines

4. Cost and Maintenance Considerations

Factor	P4 Bearings	P5 Bearings
Price	30–50% more expensive than P5	More affordable
Installation Environment	Requires cleanroom installation	Can be installed in normal workshops
Maintenance Frequency	Check every 500 hours	Check every 1,000 hours

5. Why Does Precision Matter?

Using the wrong bearing grade can lead to:

Premature wear and failure
Increased energy consumption
Poor product quality (e.g., rough surface finish on machined parts)

Final Thoughts

If your application requires extreme precision, speed, and reliability, go with P4 bearings. If you're looking for a cost-effective option that still offers solid performance, P5 bearings are usually the best choice.

Need help choosing the right bearing for your machine? Feel free to contact our team for expert advice!

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