Bearings: standards, dimensions. Standard bearing sizes

A bearing is a special unit, which is a part of the support for supporting the shaft and designed to rotate or roll the latter without losing energy for friction. There are several varieties of such constructive elements. In this case, the sizes of bearings are in most cases regulated by GOST.

Varieties

Nodes of this type are used in industry and other branches of the national economy very widely. There are hydrostatic, gas-static, magnetic and other bearing groups. However, the most common varieties are knots of sliding and rolling. According to the perceived load, both these groups are divided into:

• Radial;

• Persistent;

• Radial-thrust.

Rolling bearings

The main elements of this type of knots are balls or rollers, located at a certain distance from each other in a special cage, called the separator. During the operation of the bearing they roll along the treadmills of two rings, one of which is static in most cases. Nodes of this type are used in industry most often. The fact is that in comparison with sliding bearings they have a number of advantages. To such it is possible to attribute first of all a small friction and insignificant consumption of lubricant. Simplicity of operation and installation is also what distinguishes such bearings. Standards (their sizes are regulated by GOST) of such nodes are presented in special tables. Therefore, it is not difficult to find a suitable bearing in this or that case. A node of this type can be selected absolutely to any type of structure.

The sensitivity to vibrating and shock loads is the only drawback with which these bearings differ. Standards for their manufacture must be observed. Otherwise, they will not last too long.

Types of rolling bearings

In addition to the perceived load, nodes of this type are classified into groups according to the following characteristics:

• The form of rolling elements. In this regard, distinguish between ball and roller bearings. The rolling bodies of the latter kind can be conical, cylindrical, acicular, twisted, barrel-shaped, etc., in this case.

• By the ability of self-establishment. In this case, distinguish between spherical and non-self-aligning bearings.

• By the number of rolling bodies. There are single row and double row bearings.

• In size. All bearings produced for today on this basis are divided into several series.

Depending on the series with the same internal diameter, the width of the bearing and its outer D can vary. Used rolling bearings can be used to assemble cars, bicycles, windmills, etc.

Dimensions

The dimensions of the nodes of this type determine GOST 3478-79. At its observance very durable and durable bearings are obtained. These standards apply to all types of rolling elements, with the exception of special purpose models having a special design. In the latter case, the nodes can be manufactured in a variety of sizes, most suitable for a particular design.

To know the standard dimensions of bearings of each series, you can, as already mentioned, by special tables that indicate the outer and inner diameters, the smallest overall dimensions (Rmin), and the nominal width of the inner and outer rings (B). As an example, here is a table for a series of bearings of diameters 8 (abbreviated).

More detailed tables can be found in the specialized literature. There are also bearing standards in Compass - a graphic editor designed for automated design (in the design library). There are tables for different knot diameters.

Accuracy classes

The standard dimensions of rolling bearings can thus be learned from special tables. However, in some cases, some deviations in the dimensions from GOST are allowed. According to the accuracy class, rolling bearings are divided into:

• Normal "0";

• Increased accuracy "6";

• High "5";

• High-altitude "4";

• Super high "2".

Nodes designed for different designs may have strictly defined tolerances. So, for example, the standards of bearings for a bicycle (608 type) are:

• Tolerances of the balls - 0 / -0.005;

• Internal track - + 0.0001 / -0.0003;

• Of the external track - + 0.0001 / -0.0005.

Notation

The standards of rolling bearings during their manufacture are strictly observed. To ensure that the consumer can see what kind of knot in front of him and for what purposes he can be used, special markings are used. Rolling bearings are usually marked with an engraved set of numbers. Sometimes standard markings include letters. Wherein:

• The first digit or letter indicates the bearing type.

• The next two digits determine the node series. The first indicates a group of width or height, the second indicates a diameter.

• The last two digits represent the hole diameter code. If we multiply it by 5, we can get the value of d in mm.

The standard dimensions of bearings 66414 (landing in this case is selected in accordance with GOST 3325-85), for example, such:

• D - 70 mm;

• D - 180 mm;

• Width - 42 mm;

• Weight - 5.74 kg.

Plain bearings

Knots of this type consist of two main elements: a strong body and an insert, between which are special lubricants. The main advantages of such bearings include, first of all, small diameters, as well as the ability to make them detachable and use for shafts of very complex construction. Disadvantages of the nodes of this variety are considered not too long life and the need for expensive lubricants.

Types of plain bearings

At the moment there are nodes of this group:

• High-speed;

• Split (used, for example, in crankshafts);

• Precision machines, precisely guide shafts and enabling adjustment of the gap;

• Cheap low-speed mechanisms;

• Intended for work in special conditions (water, corrosive environments).

Depending on the mode of operation in a bearing of this type, there may be liquid or semi-liquid friction. In the first case, the working surfaces of the shell and shaft are separated by a rather thick layer of oil. When semi-liquid friction is added to the liquid boundary (through the thinnest oil film formed by molecular bonds).

Dimensions of plain bearings

The dimensions of the nodes of this group are determined by GOST 2795. Data from special tables is also what is necessarily taken into account when manufacturing such bearings. Standards in this case apply to such parameters as:

• Outer and inner diameter;

• Length (l);

• The size of the bevel (C);

• Tolerances (limit deviations).

The table below (abbreviated) presents standard sizes of plain bearings of different rows.

Design features and materials

The standards of plain bearings, therefore, are strictly defined by GOST. Some requirements are also required for the quality of materials used for their manufacture. The bearing housing of the slide, as already mentioned, can be integral or detachable. In the latter case, special pins or bolts are used to connect the parts. The bearing of the sliding bearing is made in the form of a sleeve. In a single knot it can be made of two halves. On shafts subject to deformation, usually mount self-aligning plain bearings.

The following materials can be used for the manufacture of the nodes of this type:

• Cast iron (for hull);

• Bronze, cast iron or plastic (for bushings).

In some cases, but of course, very rarely, the bushings are made of wood or even from chipboard.

Primary requirements

Thus, bearing standards (or rather, compliance with them) make it possible to produce the highest quality, durable and with excellent performance characteristics. The requirements for the nodes of this group are as follows:

• The materials and design of the plain bearings must be such as to provide a minimum coefficient of friction between the housing and the sleeve.

• The strength and rigidity of the assembly should be such that it can withstand any necessary loads.

• The maximum simplicity of the bearing design is welcomed. When installing it, there should be no difficulties.

• The bearings must be manufactured in such a way that their surface has sufficient area to remove the heat generated during operation.

How do

Manufacture of sliding and rolling bearings in specialized large enterprises, which usually include two main shops: thermal and mechanical. The assembly lines of such factories often operate in automatic mode. In addition, modern spraying machines are also installed in the shops.

In our country the most popular are knots produced in domestic factories, as well as in Switzerland (SKF). Standards of SKF bearings are the same as for Russian ones.