Bearing accuracy class

When a consumer is faced with the question of choosing a replacement bearing for a failed, he should know its main characteristics. These are bearing type, its designation and size. In some cases, it is necessary to clarify a number of additional characteristics: the presence of a protective cover, separator material, accuracy class. Today we dwell on the latter.

What is the accuracy class of the bearing?

This characteristic indicates the precision of the bearing components, i.e. minimum tolerance established on bodies and raceways, axial alignment, landing (inner) diameter.

Why do you need accuracy class?

This parameter affects, first of all, accuracy, rotational speed, smooth running and service life. In automotive and general engineering, bearings of zero (normal) accuracy class are used. A high accuracy class is needed only when the bearing is placed in a knot that requires high precision of work - for example, in machine spindles and high-speed knots.

What are the accuracy classes?

In the GOST system there are six classes (given in ascending order):

0 - zero or normal, most often not indicated in the marking;

6 - increased;

5 - high;

4 - precision;

T - especially precision;

2 - super precision.

This system operates on the territory of most countries of the former USSR.

Imported bearings are mainly marked in the ISO system (Europe) or ABEC (USA), with five accuracy classes.

Below is a table of correspondence of accuracy classes in various systems:

High-precision bearings are used in high-precision assemblies: spindles of computer hard disks and tape heads, printing presses and equipment used in metallurgy. Super-precision bearings are used where it is necessary to ensure the highest rotational speeds: in dental instruments (dental drills), aircraft turbines, centrifuges and turbo-compressors. Often, these bearings produce piece, under the order, and they can not be purchased in the public domain.

In no case should bearings of a high accuracy class be replaced with bearings without a class or with a lower accuracy class. This will adversely affect the operation of the mechanism as a whole. Replacing the zero-grade bearings with high-precision bearings is not advisable and will not give any tangible improvements in the operation of the assembly.

Also worth mentioning about roller and skate bearings: most often sellers, wanting to earn money, insist that a bearing of class ABEC-5, ABEC-7, and even ABEC-9 is required. However, in this case it makes sense to purchase the usual bearings of the manufacturer of the premium class - NSK, Koyo, SNR or SKF. The high accuracy grade of the 608zz bearing is needed if it accelerates to a speed of 700 km / h. Rollers and skaters, as a rule, accelerate to a maximum of 150-200 km/h.