Writer: Eric Bearing Limited
1. The assembly site must be kept clean. The operation and service life of SKF bearings are very important. It is necessary to prevent the bearings from being contaminated with dust, pollutants and moisture-contaminant pairs.
2. Check the bearing seat hole and the matching surface on the shaft, such as geometric and dimensional accuracy and cleanliness.
3. Apply a little oil or grease to the mating surface of the bearing ring.
4. The shaft and bearing housing holes have a guide chamfer of 10 degrees to 15 degrees.
5. Moisture generated by condensation can cause corrosion of the bearing and the mating surface of the bearing, so do not excessively cool the SKF bearing.
6. Fill the dental drill bearing with lubricant after installation and check whether the bearing configuration is working properly.
The heating temperature of the bearing depends on the bearing size and the required interference. Regarding the precautions for hot-packing operations, there are the following points to be noted:
1. Do not heat the bearing above 120 degrees Celsius;
2. In order to prevent the bearing from directly contacting the bottom of the oil groove, it is best to consider placing the dental drill bearing on the two metal or lifting the SKF bearing;
3. Heat the dental drill bearing to 20-30 degrees Celsius higher than the required temperature, so that the inner ring does not become cold during operation, and it is difficult to install;
4. After installation, the bearing cools down and the width direction also shrinks, so use a shaft nut or other suitable method to tighten it to prevent a gap between the inner ring and the bearing shoulder.
Performance required by bearing cage material:
Good dimensional stability and high mechanical strength
In addition, good workability is also required. Depending on the application, good impact resistance, heat resistance, and corrosion resistance are required.
Material of bearing ring and rolling element:
High-carbon chromium bearing steel is usually used for the rings and rolling elements. Most SKF bearings use SUJ2 in JIS steel grades. Use SUJ3 for large bearings.
In the case of further impact resistance, use chromium steel, chromium molybdenum steel, nickel chromium molybdenum steel as the bearing material, and use carburizing quenching to make the steel have a hardened layer from the surface to an appropriate depth. Carburized bearings with appropriate hardening depth, fine structure, suitable hardness of surface and core hardness have better impact resistance than bearings using bearing steel, and the chemical composition of general steel for carburizing bearings. SKF 23218 CCK/C3W33 bearings online , pls click here :
SKF bearing cage material:
The material of stamping cage is low carbon steel. Depending on the application, brass plates and stainless steel plates are also used. The material of the cut cage is made of high-strength brass and carbon steel, and synthetic resin is also used.
Impact of improper selection of SKF bearings on use after assembly
Improper selection of bearings, a large part of the reason is that when there is a large axial load, it is not appropriate to use thrust bearings or bearing support structures that can withstand larger diameters and axial combined loads. It is not appropriate to use only cylindrical roller bearings without cages. of. Poor lubrication of SKF bearings is the direct cause of bearing damage. An analysis of the current status of damaged bearings. The bearing has no fatigue damage on the rolling working surface of the imported bearing after 3000 hours of cumulative work, and the bearing only scratches. The bearing fatigue life calculated according to the radial load is very long.
It is observed that the material structure at the bearing fracture is fine without coarse grains. The fracture is silver-gray and belongs to brittle fracture. There is no obvious wear and material burn on the inner raceway of the bearing. The obvious wear and scratch phenomenon is found on the side of the inner ring rib of the bearing. The main reason is that both sides of the main crack on the side of the inner ring rib, SKF The bearings were found to be visually cracked and blue in some areas. The imported bearing and the side of the inner ring ribs were normal.
1. Bearing size restrictions.
Usually the space where the bearing can be installed is limited. In most cases, the shaft diameter (or bearing inner diameter) is based on mechanical design or other design limitations. Therefore, the choice of bearing type and size is determined according to the inner diameter of the bearing. As a result, the main dimensions of standard bearings are compiled based on the internal diameter dimensions of international standards.
2. Classification of bearings.
According to the classification of bearings, the industries that may use imported bearings are analyzed. The key issue is to determine the key industries to attack based on the actual situation of the company's stocking.
3. Bearing installation: The installation of SKF bearings must be carried out under dry, clean environmental conditions. Before installation, the machining quality of the mating surface of the shaft and the housing, the end surface of the shoulder, the groove and the connecting surface should be carefully checked.
Generally, high-speed operation and high-precision equipment need bearings, because it is necessary to ensure normal speed and high precision and reduce maintenance costs.
Generally, the shaft is supported by two bearings in the radial and axial directions. The SKF bearing on one side is called a fixed-end bearing. It bears both radial and axial loads. The role of relative axial displacement. The other side is called the free end, which only bears radial load and can move relatively in the axial direction.
The fixed-end bearings must be fixed with both the shaft and the bearing box. The more suitable bearings are radial bearings that can withstand compound loads, such as deep groove ball bearings, spherical roller bearings and double-row or paired angular contact ball bearings or tapered rollers. Sub bearing. Radial bearing combinations that bear simple radial loads, such as cylindrical roller bearings without ribs on the inner and outer rings combined with deep groove ball bearings or four-point contact ball bearings or bidirectional thrust bearings, can also be used as fixed-end bearings. At this time, the second bearing provides bidirectional axial positioning, but it must be kept at a certain radial distance from the bearing box during installation. The free end bearing will not squeeze in the imported bearing when the length of the shaft changes due to thermal expansion. Axial displacement can occur inside the bearing, as well as bearing rings and bearing seats.
"Cross-fixed" refers to such an imported bearing configuration, in which each SKF bearing is positioned unidirectionally on the shaft in the opposite direction. This combination is mainly used for short axis. All radial bearings that can withstand axial loads in at least one direction are applicable, including deep groove and angular contact ball bearings, tapered roller bearings and NJ cylindrical roller bearings. When angular contact ball bearings or tapered roller bearings are used, In some cases, a preload must be applied.