Why does the precision bearing turn black and blue? Various common failure causes and solutions

When we use precision bearings, we will find that the bearings turn black and blue. This is caused by improper operation during use or installation. How should we solve it? Next, the precision bearing manufacturer will introduce the reasons and solutions for the black and blue of precision bearings and other common faults. Let’s take a look!

Precision bearings turn black and blue

Cause Analysis

1. In use, the bearing will turn black and blue when it is burnt due to the high temperature;

2. When the precision bearing is installed by heating method, the bearing is annealed due to the high heating temperature, which reduces the hardness of the bearing.


1. Pay attention to the correct use of bearings and strictly control the temperature;

2. When using the heating method to install the bearing, the heating temperature should be controlled according to the regulations and the operation should be carried out in accordance with the correct installation process.

Bearing temperature rise is too high

Cause Analysis

1. The reason for the excessive temperature rise of the bearing may be the intrusion of impurities or dirt during installation and use;

2. Improper use of lubricant, or lack of grease but not added in time;

3. The friction of gaskets, sealing devices, bushings and other parts or friction due to loose fit;

4. Improper installation will also cause excessive temperature rise of the bearing, such as non-concentric mounting holes, deflection of the inner and outer rings, deformation of the raceway, and improper gap adjustment, etc.;

5. When choosing to use unmatched bearings, or temporarily substituting other types of bearings, it is easy to generate heat due to overload or high speed.


1. Install in accordance with the correct operating procedures;

2. Pay attention to regular maintenance and maintenance, check whether the lubricating grease is sufficient, and regularly check whether the bearing is in a stable operating state, if any abnormality is found, it needs to be repaired in time.

3. It is necessary to select and use suitable precision bearings according to the oil pipe data.

Abnormal noise during operation

Cause Analysis

1. If the rolling elements and raceways of the bearing have severe peeling and uneven surfaces, it will cause abnormal bearing noise;

2. Improper installation of bearing parts, or friction after the accessories are loose;

3. The less lubricant;

4. Iron filings or dirt enter the bearing.


1. Install the bearing correctly in accordance with the process;

2. Frequent use of lubricants, add them in time;

3. Regularly check the operation of the bearing to find out the problem and solve it in time.

Severe wear of the fluid body

Cause Analysis

1. The bearing can withstand improper axial load;

2. The installation of rolling elements is skewed during installation;

3. The lubricant is too thick;

4. Because the rolling elements do not roll, sliding friction is caused and the bearing is damaged;

5. If the bearing temperature rises too high, it will also cause damage to the rolling elements;

6. The rolling elements are crushed due to mechanical vibration or improper bearing installation;

7. The bearing manufacturing precision is not high, the heat treatment is improper, the hardness is low, and the rolling elements are ground into a polygonal shape.


1. Install the bearing correctly;

2. Use a suitable lubricant or replace the lubricant regularly;

3. Correct use and maintenance of bearings.

Pit scars in the fluid channel

Cause Analysis

1. Metal peeling and rusting;

2. Lack of lubricant and not added in time;

3. The bearing has been subjected to shock load;

4. Electric current flows through the bearing, causing high temperature locally to cause the metal to melt.


1. Select correctly according to the different performance of different bearings;

2. Add lubricating oil in time;

3. The equipment must have a grounding device to avoid leakage.

There are cracks in the inner and outer rings of the bearing

Cause Analysis

1. Poor contact between the journal or bearing seat hole mating surface, gaps in the stressed parts of the raceway, large and uneven bearing forces, fatigue cracks will occur;

2. Be beaten during disassembly and assembly;

3. Large bearing clearance causes shock and vibration;

4. The bearing itself is of poor quality and internal cracks appear.


1. Avoid violent beating when loading and unloading;

2. Replace worn bearings in time;

3. Purchase high-quality bearings.

Bearing metal peeling

Cause Analysis

1. The bearing is subjected to impact force and alternating load, and the contact stress on the surface of the rolling elements changes repeatedly;

2. The installation of the inner and outer rings is skewed, the axial matching steps are not vertical, and the shaft holes are not concentric;

3. The bearing clearance is adjusted too tightly;

4. Iron filings or hard dirt fall between the bearing mating surfaces;

5. The shaft journal or bearing seat hole is elliptical, causing the raceway to be locally overloaded;

6. The selected substitute bearing model does not meet the requirements.


1. Install and use bearings correctly;

2. Keep the surrounding environment clean and tidy during operation to prevent iron filings and other dirt from falling into the bearing;

3. Choose bearings with appropriate model and performance.

The hydraulic body is crushed, mostly in the thrust bearing

Cause Analysis

1. Excessive extrusion force caused by too small installation clearance;

2. Severe impact during use;

3. Foreign matter entered into the lubricant, mixed with hard iron filings and other dirt;

4. The rolling element itself has cracks or the bearing runs for too long.


1. Adjust the bearing clearance in place;

2. Ensure that the lubricant is sealed to avoid entering foreign objects;

3. Regularly carry out the maintenance of the bearing and replace it in time according to the situation.

Can’t turn after installation

Cause Analysis

1. The bearing is not cleaned, and there is sand or iron filings between the rolling elements and the raceway;

2. The cage is deformed and the rolling elements are in contact with the bearing ring;

3. The fit of the bearing and the shaft (or the housing hole) is too tight (too large interference and reduced bearing clearance) or the original bearing clearance is too small.


1. Clean the bearing correctly, and check whether it is clean after cleaning;

2. Install correctly;

3. Scrape the shaft diameter (or shell hole diameter) to appropriately reduce the fit interference;

4. If the original clearance of the bearing is found to be too small, a new bearing must be replaced.

Scratches in the bearing fluid passage

Cause Analysis

1. The upper and lower rings of the bearing are not parallel;

2. The speed is too large;

3. The rolling elements slide on the raceway;

4. Lubricant enters foreign matter such as dust.


1. Pay attention to correct installation and use;

2. Pay attention to the correct selection and use of lubricants, and keep them well.

The above is a complete introduction to the reasons and solutions for the black and blue of precision bearings and other common faults. After the above introduction, it can be seen that many faults in the bearing are caused by incorrect installation, improper use, and careless maintenance.

Therefore, the correct installation, use, and maintenance are very important. These basic tasks must be done well, so that the operating efficiency of the bearing can be greatly improved, and the service life of the bearing can be increased.