Why the bearing axis of rotation is very difficult? - bearing knowledge

Bearing as an important parts of machinery and equipment operation, when we find the bearing in the process of operation, the bearing axis always feeling turn to be not moved, the so-called hard bearing axis? This is how to return a responsibility? According to actual situation, also has a lot of people ask this kind of similar problems, China bearing network for everyone to make relevant solutions. Why the bearing axis of rotation is very difficult? In general, the main reasons are the following aspects, can be considered from several aspects, and find the appropriate method to solve very well. 1, lubrication failure, the oil level too high or too low, bearing clearance improper choice. 2, clean degree does not reach the designated position, may have sundry. 3, oil seal, shoulder and sealing, locking piece ( The sun) The position such as inappropriate. 4, shaft concentricity wrong is, cross positioning caused by axial stuck. 5, low accuracy of bearing box, and twisted.