Precision bearings are classified according to ISO grading standards: P0, P6, P5, P4, P2. The grades are sequentially increased, of which P0 is ordinary precision, and other grades are precision grades. Of course, different grading standards, different types of bearings, their grading methods are different, but the meaning is one. The performance of precision bearings requires the rotor to have high runout accuracy, high speed rotation and low friction and frictional changes.
Since the precision of the precision bearing itself is less than 1μm, it is required to have high dimensional accuracy and shape accuracy with the matching parts (shaft, bearing housing, end cover, retaining ring, etc.), especially the matching surface precision should be controlled in the same way as the bearing. In the horizontal, this is crucial and is most easily overlooked. It must also be noted that if the matching parts of the precision bearing do not meet the above requirements, the precision bearing will often be several times larger or even more than 10 times larger than the original bearing after installation. It is not a precision bearing at all. The reason is the matching machine. The error of the piece is often not simply superimposed on the error of the bearing, but is amplified by different multiples.