The key points to pay attention to during the appearance inspection are as follows:
(1) Various cracks, such as raw material cracks, forging cracks, heat treatment cracks and grinding cracks, etc., these cracks will become a source of stress concentration and expand rapidly during the future operation of the bearing, causing the bearing to rupture and affecting the bearing life and operation. The security impact is huge.
(2) Various mechanical scars, such as abrasions, scratches, crushes, bumps, etc., will cause poor bearing installation, cause eccentric load and stress concentration, and cause a decrease in rotation accuracy and service life.
(3) Rust, black skin and pitting. The latter two are defects that easily store water and dirt, and can easily develop into rust. Rust is a source of pollution that leads to poor installation, early wear and fatigue. Severe corrosion will cause the bearing to be scrapped.
(4) Peeling and folding. The local parts of these two defects are not firmly bonded with the base metal, and there are often decarburization or carbon depletion phenomena around them to varying degrees. The material is easy to collapse, dent or wear, which has a negative impact on the bearing life and accuracy. Very disadvantageous.
How to judge whether the bearing is usable?
Mainly consider several aspects from the mechanical properties of the bearing, the degree of damage, importance, operating conditions and the period until the next maintenance. Generally speaking, if a bearing has the following conditions, it should be replaced with a new bearing and should no longer be used.
1. There is rust and damage on the raceway surface and rolling elements.
2. There is a break in any of the ferrules and rolling elements.
3. There are cracks or gaps in any of the inner ring, outer ring, rolling elements and cage.
4. The cage is significantly worn or the rivets are significantly loose.
5. The discoloration caused by heat is obvious.
6. There is obvious creep on the inner diameter surface of the inner ring or the outer diameter surface of the outer ring of the miniature bearing.
7. Bearings sealed with grease, seals or dust covers are obviously damaged.
8. There are obvious jams on the rolling surface, ribs and rolling elements.
9. There are serious indentations and scratches on the raceway surface and rolling elements.
