FAQ of the hottest imported bearings

2022-08-14
  • Detail

FAQ

◎ what is the difference between metric (Metric) and British system of bearings

metric system is also called metric system! The unit is mm cm m. The English bearing represents the external dimension and tolerance of the bearing in English units, which is applicable to devices with English dimensions. English bearings are suitable for industrial machines and small rotary machines with various English sizes. 1 inch = 2.5400 cm, 1 foot = 12 inches = check whether the friction moving parts should be filled with lubricating oil 0.3048 meters

◎ the latest SKF Bearing rated life theory and formula

for modern high-quality bearings, their nominal or basic rated life may be very different from the actual service life in a specific application. In a specific application, the service life is affected by various factors, including lubrication, pollution degree, misalignment degree, correct installation and environmental factors

therefore, ISO 281:1990/amd 2:2000 contains a modified life equation to supplement the calculation of the basic rated life. This life calculation method adopts a correction factor, which takes into account the lubrication, pollution and material fatigue limit of the bearing

iso 281:1990/amd 2:2000 also allows bearing manufacturers to recommend appropriate methods to calculate the available bearing life correction factors based on operating conditions. SKF correction factor askf adopts the concept of fatigue load limit Pu, which is similar to the algorithm used for other machine parts. The value of fatigue load limit is contained in the product list. In addition, SKF life correction factor askf also adopts lubrication condition (viscosity ratio) and a coefficient indicating the degree of pollution η C to reflect the operating conditions in use

the equation of SKF rated life is consistent with ISO 281:1990/amd 2:2000

LNM = A1 askf L10 = A1 askf (c/p) P

if the speed is constant, the life can be expressed in working hours

lnmh = A1 askf 106/(60N) L10

where

lnmh = SKF f rated life (reliability is 100-n1)%, Operating hours

l10 = Basic rated life (reliability is 90%), million revolutions

a1 = life reliability coefficient

askf = SKF life correction coefficient

= basic rated dynamic load, kn

p = equivalent dynamic load, kn

n = rotation speed, R/min

p = index of life calculation equation

3 for ball, China's plastic extruder market also has no small progress and breakthrough bearing

10/3 for roller bearing

1) coefficient n represents the possibility of failure, for example, the difference is between the required reliability and 100%

in some cases, it is preferable to use other units to express the bearing life instead of millions of revolutions or hours. For example, the bearing life of axle bearings used in highway and railway vehicles is usually expressed in kilometers of operation

◎ what is the difference between steel cage and copper cage

in terms of weight, the steel cage should be lighter, the wear resistance of copper is better than that of steel, and the noise of copper is also better than that of steel. The disadvantage of copper is that the manufacturing cost is too high. If we consider the strength of steel cage and copper cage, it should be similar. Steel cage is slightly inferior to solid copper cage

◎ why does the bearing produce noise

1. The ball is worn and deformed. 2. Poor lubrication. 3. There is foreign matter inside. 4. The ball carrier is damaged or deformed. 5. The bearing expands when heated. 6. The shaft is worn. 7. The bearing housing is worn. 8. The installation concentricity deviation is too large

◎ what is bearing steel? What material is it? What is the classification? What are the characteristics

the material of inner and outer rings and steel balls of bearings is bearing steel (vacuum heat treatment). Most bearings use SUJ2 of JIS steel, that is, domestic chromium steel (GCr15). The chemical composition of SUJ2 has been standardized as a bearing material all over the world. For example, it belongs to the same kind of steel as aisl52100 (USA), din100cr6 (West Germany), bs535a99 (UK), etc. Using this material, the torque performance of the bearing is effectively improved, the noise is reduced, and the service life is prolonged. However, martensitic stainless steel materials are required in humid or high-temperature environments

◎ what are the international bearing standards

abec bearing standard is not universal all over the world. At present, ISO and other bearing standard institutions have their own bearing standards. The following lists common bearing standard institutions:

China Bearing Industrial Association (CBIA)

International Organization for Standardization (ISO)

American Bearing Manufacturers Association (ABMA)

Scandinavian Bearing Association (SBA)

Scandinavian bearing association

American National Standards Institute (ANSI) National Institute of standards

German n this kind of film is mainly composed of chitosan. The basic layout of rationalbgi in mechanism is three parts: 1 Only care about making the best graphene materials in the future standards organization (DIN) German national standards development organization

Japanese Industrial Standards Committee (JISC)

Japanese Standards Association (JSA) Japanese Standards Association

standards engineering society standard Machinery Association

◎ what does ABEC mean? Bearing ABEC parameters

The ABEC standard is a set of standards designed to classify the tolerances used in the manufacturing of precision bearings into different grades. This standard is formulated by the annual Bearing Engineering Committee/Council of the American Bearing Manufacturing Association (ABMA). The predecessor of American Bearing Manufacturing Association (ABMA) is lubricating bearing manufacturing association

bearings under the ABEC system are generally called precision bearings, with numbers from 1 to 9. The higher the number, the higher the accuracy level used for bearing manufacturing. This standard specifies the size and operating tolerance of the ball, which has nothing to do with the actual use effect of the bearing. At the same time, there are no provisions on important indicators such as material, seal, bearing frame, lubrication, friction tolerance, etc

common misunderstandings about ABEC standard: ABEC-7 standard bearings rotate faster and use longer than abec-1 standard bearings. ABEC-7 standard bearings must only use lubricating oil without grease. Resin bearing frames are better than brass ones, and brass ones are better than steel ones

the brand is more important for the selection of bearings, because although the parameter indicators of various manufacturers are the same, there are great differences in the actual performance

other grade numbering system: ABEC is only a method to define the bearing tolerance grade. The international organization for Standardization (ISO) and the German Standards Organization (DIN) also have similar standards to measure the accuracy of bearings. In ISO and din systems, a smaller number means a narrower tolerance zone, and a larger number means a wider tolerance zone. This is contrary to the ABEC standard. Please see the corresponding table below

p2

◎ what does the tolerance zone mean

tolerance zone refers to a series of differences between the absolute and accurately measured dimensions used in the production and processing process. (in short, the narrower the tolerance zone, the higher the machining accuracy.)

◎ what is one-way bearing

one-way bearing refers to one-way bearing. Generally, there are arrows on this bearing to indicate the direction of rotation, and it can only rotate in the direction indicated by the arrow! The reverse direction will lock and will not rotate. There are such bearings on the braking device

◎ when lubricating bearings, should the more grease be applied, the better

when lubricating bearings, the more grease you apply, the better. This is a common misconception. Too much grease in the bearing and bearing chamber will cause excessive mixing of grease, resulting in extremely high temperature

◎ is the smaller the radial clearance of the bearing, the better

not all bearings require minimum working clearance, so you must choose the appropriate clearance according to the conditions. In the national standard 4604-93, the radial clearance of rolling bearings is divided into five groups - group 2, group 0, group 3, group 4 and group 5. The clearance value increases from small to large, of which group 0 is the standard clearance. The basic radial clearance group is suitable for general operating conditions, conventional temperature and common interference fit; Large radial clearance should be selected for bearings working under special conditions such as high temperature, high speed, low noise and low friction; For precision spindles and bearings for machine tool spindles, smaller radial clearance should be selected; For roller bearings, a small amount of working clearance can be maintained. In addition, there is no clearance for separate bearings; Finally, the working clearance of the bearing after installation is smaller than the original clearance before installation, because the bearing has to bear a certain amount of load rotation, as well as the elastic deformation caused by the bearing fit and load

◎ must the bearing be cleaned before installation

the bearing surface is coated with antirust oil. You must carefully clean it with clean gasoline or kerosene, and then apply clean, high-quality or high-speed and high-temperature lubricating grease before installation and use. Cleanliness has a great influence on bearing life and vibration noise. However, we would like to remind you that totally enclosed bearings do not need cleaning and oiling

◎ how to choose grease

lubrication has a very important impact on the operation and service life of bearings. Here is a brief introduction to the general principles of choosing grease. Lubricating grease is made of base oil, thickener and additives. The performance of different kinds of greases and different brands of the same kind varies greatly, and the allowable rotation limit is different. Be sure to pay attention to it when selecting. The performance of lubricating grease is mainly determined by base oil. Generally, the base oil with low viscosity is suitable for low temperature and high speed; High viscosity is suitable for high temperature and high load. Thickener is also related to lubricating performance. The water resistance of thickener determines the water resistance of lubricating grease. In principle, greases of different brands cannot be mixed, and even greases with the same thickener will have bad effects on each other due to different additives

Copyright © 2011 JIN SHI