For each bearing, there is its own limit rotational speed, bearing speed is mainly by the bearing internal friction heat caused by the temperature rise of the limit, when the rotational speed exceeds a certain limit, the bearing will be due to burns and so on and can not continue to rotate, and even make the bearing stuck.

Therefore, we are rotating the right type of bearing according to the rotational speed of the bearing, then we need to go to understand what are the requirements for rotational speed selection of bearings. In some applications, other factors are more important than the limiting speed. Such as: low speed, reciprocating oscillation, etc.

The limiting speed of a bearing is the threshold value at which it can rotate continuously without generating frictional heat that causes burns. Therefore, the limiting speed of the bearing depends on the type, size and precision of the bearing as well as the lubrication method, the quality and quantity of the lubricant, the material and type of the cage, the load conditions and other factors.

First, the rotational speed on the selection of bearing type

1. Ball bearings have higher limiting speed and rotary accuracy than roller bearings, so ball bearings should be preferred in high speed.

2. In the same conditions of the inner diameter, the smaller the outer diameter, the smaller the rolling body, the smaller the centrifugal inertia force added to the peripheral raceway of the rolling body during operation, and thus also suitable for work at higher speeds. Therefore, in high speed, it is appropriate to use the same diameter series in the outer diameter of the smaller bearings. If the bearing with a smaller diameter and the bearing capacity does not meet the requirements, and then installed the same bearing, or consider using a wide range of bearings.

3. Cage material and structure of the bearing speed has a great impact on the bearing.

Solid keep frame than stamping keep frame allows some higher speed, bronze entity keep frame allows higher speed. Generally higher speed work occasions, it is appropriate to choose deep groove ball bearings, angular contact bearings, cylindrical roller bearings; in the lower speed work occasions, can choose tapered roller bearings.

Tapered roller bearings limit speed, generally about 65% of the deep groove ball bearings, cylindrical roller bearings 70%, 60% of the angular contact ball bearings. Thrust ball bearings have a low limiting speed and can only be used in lower speed applications.

The limiting speed given by the bearing manufacturer generally refers to the high speed that can be achieved under the agreed conditions: e.g. bearing tolerance is 0 level; bearing clearance is 0 group; bearing load is 10% of the rated load; lubrication and cooling conditions are normal; centripetal bearings bear radial load only, axial bearing bearings bear axial load only; the temperature of the outer ring is not more than 100℃, etc..

The range of speeds required for the application helps to determine what type of bearing to use. Most of the bearing manufacturer's catalogue provides its product limit speed value, practice has proved that in the limit speed below 90% of the state work is better.

Second, the factors affecting the bearing speed

Factors affecting the limiting speed of the bearing include the size of the applied load; the direction of the force; the type of lubricant, the amount of lubricant; bearing manufacturing accuracy that is the tolerance level of the bearing and the size of the clearance of the bearing and so on.

In addition, the lubricant according to its type and grade of different, but also may be better than other performance but not for high-speed rotation.

Bearing limit speed of the high and low factors are related to the type of bearing, load, precision, size, lubrication, clearance, cage and cooling conditions. However, the main factor is still the bearing material allowable working temperature or lubricant.

Third, the rolling bearing with the selection method

Correct selection of bearing with, to ensure the normal operation of the machine, improve the service life of the bearing and make full use of the bearing capacity of the bearing has a great relationship.

1. Whether the collar is rotating. When the inner ring or outer ring bearing work for the rotating circle, should use a slightly tight fit, the size of its surplus should make the surface in the working load does not occur ‘crawling’, because once crawling, with the surface to be worn, produce sliding, the higher the speed of the ring, the more serious the wear and tear. Bearing work, if the inner ring or outer ring for the non-rotating ring, in order to disassemble and adjust the convenience, it is appropriate to choose a loose fit.

2, load type. Bear a local load of the collar should be selected loose transition fit or clearance is small with, in order to let the friction torque between the ring raceway to drive the collar transposition, so that the collar force uniformity, prolonging the service life of the bearing.

Fourth, other factors affecting the bearing with

1. The influence of the working temperature. Bearing work, due to friction heat and other heat sources, the temperature of the ring is higher than the temperature of its matching parts. Thermal expansion of the inner ring will cause it to loosen with the journal, while the outer ring of thermal expansion will cause it to tighten with the shell hole.

2. Rotational accuracy and rotational speed of the impact. For bear load and require high rotational accuracy of the bearing, in order to eliminate the elastic deformation and vibration of the impact, should avoid the use of clearance fit. For some precision machine tool light load bearings, in order to avoid and shaft shape error on the bearing accuracy, often with clearance fit. Generally speaking, the higher the rotational speed of the bearing, the tighter the fit should be.

3, mounting and dismounting bearing conditions. Considering the convenience of bearing mounting and dismounting, it is appropriate to use a loose fit, for heavy machinery with large and very large bearings, this is particularly important. Such as the requirements of easy mounting and dismounting and the need for a tight fit, can be used to separate the type of bearing, or the use of the inner ring with a tapered hole, with a tight sleeve and back off the groove of the bearing.