Three major bearing use misunderstandings, quickly see if you have stepped in

Three major bearing use misunderstandings, quickly see if you have stepped in
The use of bearings in mechanical equipment is very common, but there are always some people will misunderstand the use of bearings on some issues, such as the following three misunderstandings.

Misunderstanding one: bearing is not standard parts?

Raise the issue of people, the bearing or some understanding, but to answer this question, but not easy. It must be said that bearings are both standard parts, but also not standard parts.

The first layer of meaning: bearings are standard parts. What do you mean by standard parts? Come on, let's look at Baidu Encyclopaedia how to say.

It says, standard parts of the structure, size, drawing, marking and other aspects of complete standardisation. It refers to the same type of bearing, the same size structure, with the installation of interchangeability.

For example, 608 bearings, its external dimensions are 8mm ID x 22mm OD x 7mm width, that is, you buy 608 bearings in the SKF home and in the NSK home to buy 608 bearings external dimensions are the same, that is, the length of a mould.

In this sense, we say that the bearing is a standard part, only refers to the same model head.

The second meaning: the bearing is not a standard part. The first meaning said, for 608 bearings, the same external dimensions, the internal may not be the same! The real guarantee of your long-term use is the internal structure parameters.

The same 608 bearing, the internal can be very different. For example, the clearance can be MC1, MC2, MC3, MC4, MC5 according to the fit tolerance for selection; cage can be iron or plastic; precision can be P0, P6, P5, P4, etc. Selected according to the use; grease can be from high temperature to low temperature of hundreds of kinds of choice according to the working conditions, and the amount of grease sealing into the different.

In this sense, we say that the bearing is not a standard part. According to the specific conditions of use, can provide different performance of 608 bearings for Jun to choose. In order to standardise them, it is necessary to define the parameters of the bearing (dimensions, seal type, cage material, clearance, grease, sealing volume, etc.).

Conclusion: for bearings, you must not simply regarded as standard parts, must understand the meaning of its non-standard parts, in order to choose the bearing, on the right sedan chair to marry the right man.

Myth 2: Can you use this bearing for 10 years?

For example: you go to buy a car, 4S shop sales and manufacturers brag about the warranty 3 years or 100,000 km, you used six months to find the tyres broken, looking for 4S shop claims, but was told that the warranty is not covered, you're very angry, swore to dislike the sky and the earth dislike of the 4S shop, but was disliked by the 4S shop to dislike back. Warranty manual clearly written warranty 3 years or 100,000 kilometres is conditional, for the whole car core parts (engine, transmission, etc.) warranty, you this tyre is a wear parts, not in the warranty scope.

In fact, 3 years or 100,000 kilometres is conditional. So many people often ask "bearings can be used for 10 years?" There are also conditions.

This question is the service life of the bearings, for the service life of the bearings, must be a certain use conditions under the service life, leaving aside the use of conditions to talk about the service life of the bearings is playing a rogue. Similarly, this 10 years but also according to the specific frequency of use of the product, converted to hours (h), because the calculation of bearing life can not be calculated when the years, can only calculate the number of hours (h).

Calculate the service life of the bearing, what conditions are needed? Calculate the service life of the bearing generally need to know the bearing use of the force situation (axial force Fa and radial force Fr), the speed situation (run how fast, running at a constant speed or variable speed running), the temperature situation (the temperature of the work). If it is an open bearing, you also need to know what lubricant, cleanliness and so on.

With these conditions, but also need to calculate the two life.

Life: the basic rated life of the bearing L10 (assessment of how long the bearing material fatigue spalling), the specific formula is as follows (from the SKF comprehensive sample):

It is important to understand that the basic rating life of a bearing is to assess the degree of handling resistance of the bearing, generally giving a theoretical calculated life of 90% reliability. Only this formula may not be enough, such as SKF or NSK may give a variety of correction factors.

Life two: the average grease life L50 (assessment of how long the grease will dry out), each bearing manufacturer's calculation formula is different, the following to NSK sample book gives the calculation formula:
The average grease life of the bearing L50 basically determines the final service life of the bearing, the quality is good, do not give the lubricant (grease dried up), dry friction can be friction how long? So this average grease life L50 is basically considered to be the final service life of the bearing (Note: the average grease life L50 for the reliability of 50% of the empirical formula for calculating the life, for reference only, the actual test and evaluation of the discrete larger).

Conclusion: bearing can be used for how long, you said it does not count, I said it does not count, bearing the actual conditions of use say.

Myth three: your bearing so brittle, a pressure on the collapse?

The bearings are easy to have a strange sound when they are gently pressed, which indicates that the bearings have produced internal scars.

Normal installation of bearings, if the inner ring is a mating surface, then it will press the inner ring, the outer ring is not stressed, and will not produce scars, as shown below.

The average grease life of the bearing L50 basically determines the final service life of the bearing, the quality is good, do not give the lubricant (grease dried up), dry friction can be friction how long? So this average grease life L50 is basically considered to be the final service life of the bearing (Note: the average grease life L50 for the reliability of 50% of the empirical formula for calculating the life, for reference only, the actual test and evaluation of the discrete larger).

Conclusion: bearing can be used for how long, you said it does not count, I said it does not count, bearing the actual conditions of use say.

Myth three: your bearing so brittle, a pressure on the collapse?

The bearings are easy to have a strange sound when they are gently pressed, which indicates that the bearings have produced internal scars.

Normal installation of bearings, if the inner ring is a mating surface, then it will press the inner ring, the outer ring is not stressed, and will not produce scars, as shown below.

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