Classification of bearings:
According to the size of the outer diameter, it is divided into:
1. Micro bearings: bearings with a nominal outer diameter range of less than 26mm.
2. Small bearings: bearings with a nominal outer diameter size range of 28-55mm.
3. Small and medium-sized bearings: bearings with a nominal outer diameter size range of 60-115mm.
4. Medium and large bearings: bearings with a nominal outer diameter size range of 120-190mm.
5. Large bearings: bearings with a nominal outer diameter size range of 200-430mm.
6. Extra large bearings: bearings with a nominal outer diameter range of 440mm or more

Ultimate speed of bearings
The rotational speed of the bearing is mainly limited by the temperature rise caused by friction and heating inside the bearing
After exceeding a certain limit, the bearing may not continue to rotate due to burns or other reasons.
The limit speed of a bearing refers to the limit at which it can rotate continuously without generating frictional heat that can cause burns
Limits. Therefore, the ultimate speed of a bearing depends on the type, size, and accuracy of the bearing
And lubrication methods, quality and quantity of lubricants, materials and types of cages, load conditions, etc
Various factors.
Fatigue life of bearings:
1. Fatigue life: The bearing bears composite operation, and the raceway surfaces of the inner and outer rings, as well as the rolling element
The rotating surface, due to repeated loading and material fatigue, appears on the raceway surface or rotating surface
Flaking's fish scale like damage. The total number of rotations where Flaking first appeared on the intercepted lane is called
Rolling fatigue life is often referred to as narrow life.
The fatigue life of bearings, even with the same size, structure, material, heat treatment, and processing method
Bearings, even when operating under the same conditions, are uneven. This is because of the material
Its own unevenness. Therefore, treat this uneven lifespan as a statistical phenomenon.
2. Rated fatigue life: The so-called rated fatigue life refers to the combination of bearings of the same model,
Operate one by one under the same operating conditions, with 90% of the bearings being able to avoid rolling
The total number of operations of Flaking caused by fatigue. When the rotational speed is constant
Use total operating time to represent the rated fatigue life.
3. During operation, the size of bearings may change due to changes in material structure. This transformation is influenced by
The impact of temperature, time, and stress.
4. In order to avoid impermissible dimensional changes due to structural changes in materials during work, the bearing material must undergo special heat treatment.