Bearings: standards, sizes. Standard bearing sizes

2024 Author: Howard Calhoun | [email protected]. Last modified: 2024-01-17 18:37

A bearing is a special unit, which is a part of the support to support the shaft and is designed to rotate or roll the latter without losing energy to friction. There are several varieties of such structural elements. At the same time, the dimensions of bearings in most cases are regulated by GOST.

Varieties

Knots of this type are widely used in industry and other sectors of the economy. There are hydrostatic, gas-static, magnetic and other groups of bearings. However, the most common varieties are sliding and rolling units. According to the perceived load, both of these groups are divided into:

• radial;
• stubborn;
• angular contact.

Rolling bearings

The main elements of this type of units are balls or rollers located at a certain distance from each other in a special cage called a separator. During the operation of the bearing, they roll along the treadmillstwo rings, one of which is static in most cases. Knots of this type are used most often in industry. The fact is that in comparison with plain bearings, they have a number of advantages. These include, first of all, low friction and low lubricant consumption. Ease of operation and installation is also what distinguishes such bearings. The standards (their sizes are regulated by GOST) of such nodes are presented in special tables. Therefore, finding a suitable bearing in one case or another will not be difficult. A knot of this type can be matched to absolutely any typical construction.

Sensitivity to vibration and shock loads is the only drawback that distinguishes such bearings. Standards in their manufacture must be observed. Otherwise, they won't last too long.

Types of rolling bearings

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

• Shape of rolling elements. In this regard, a distinction is made between ball and roller bearings. The rolling elements of the latter type can be conical, cylindrical, needle-shaped, twisted, barrel-shaped, etc.
• According to the ability of self-establishment. In this case, a distinction is made between spherical and non-self-aligning bearings.
• By the number of rolling elements. There are single row and double row bearings.

• According to size. All bearings produced today according to this featuredivided into several series.

Depending on the series with the same inner diameter, the width of the bearing and its outer D may vary. Rolling bearings can be used when assembling cars, bicycles, windmills, etc.

Sizes

GOST 3478-79 determines the dimensions of nodes of this type. If it is followed, very strong and durable bearings are obtained. These standards apply to all types of rolling units, with the exception of special-purpose models that have a special design. In the latter case, the nodes can be made in a variety of sizes, most suitable for a particular design.

You can find out the standard sizes of bearings of each series, as already mentioned, from special tables that indicate the outer and inner diameters, the smallest limit dimensions (Rmin), as well as the nominal width of the inner and outer rings (B). As an example, below is a table for a series of bearings with diameters 8 (abbreviated).

d	D	Size B for series							Rmin
		7	1	2	3	4	5	6
0.6	2.5	-	1	-	1.4	-	-	-	0.05
1.5	4.0	-	1.2	1.7	2	-	-	-	0.05
3	7	-	2	2.5	3	-	-	-	0.10
7	14	-	3.5	5	6	-	-	-	0.15
20	32	4	7	8	10	12	16	22	0.3
200	250	16	24	30	37	50	67	90	1 for episode 7, 1.5 for episodes 1-6

More detailed tables can be found in specialized literature. There are also bearing standards in Compass, a graphical editor designed for computer-aided design (indesign library). There are tables for different knot diameters.

Accuracy classes

Standard dimensions of rolling bearings can therefore be found in special tables. However, in some cases, some deviations in dimensions from GOST are allowed. According to the accuracy class, rolling bearings are divided into:

• normal "0";
• high precision "6";
• high "5";
• extra high "4";
• super high "2".

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

• ball tolerances - 0/-0.005;
• inner track - +0.0001/-0.0003;
• outer track - +0.0001/-0.0005.

Notation

Standards of rolling bearings must be observed in their manufacture. In order for the consumer to be able to see what kind of node is in front of him and for what purposes it can be used, special markings are used. Rolling bearings are usually designated by an engraved set of numbers. Sometimes standard markings include letters. At the same time:

• The first number or letter indicates the bearing type.
• The next two digits define the node's series. The first indicates a width or height group,the second is the diameter.
• The last two digits are the hole diameter code. If you multiply it by 5, you can get the value of d in mm.

Standard sizes of bearings 66414 (fits in this case are chosen according to GOST 3325-85), for example, these are:

• d - 70mm;
• D - 180mm;
• 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 there are special lubricants. The main advantages of such bearings include, first of all, small diameters, as well as the ability to make them split and use them for shafts of a very complex design. The disadvantages of nodes of this variety are considered to be not too long service life and the need to use expensive lubricants.

Types of plain bearings

Currently there are nodes of this group:

• high-speed;
• split (used, for example, in crankshafts);
• precision machines that precisely guide the shafts and enable gap adjustment;
• cheap low-speed mechanisms;
• designed to work in special conditions (water, aggressive environments).

Depending on the mode of operation, this type of bearing can have fluid or semi-fluid friction. In the first casethe working surfaces of the housing and shaft are separated by a rather thick layer of oil. With semi-fluid friction, boundary friction is added to liquid friction (through the thinnest oil film formed by molecular bonds).

Plain bearing dimensions

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

• outer and inner diameter;
• length (l);
• chamfer size (C);
• tolerances (limit deviations).

The table below (abbreviated) shows standard plain bearing sizes for different rows.

d	D for rows		L for rows
	1	2	1	2	3	4
1	3		1	2
9	14	12	6	10	14
25	32	30	20	25	30	35

Design features and materials

Standards for plain bearings are thus strictly defined by GOST. Some requirements are also imposed on the quality of the materials used for their manufacture. The sleeve bearing housing, as already mentioned, can be one-piece or split. In the latter case, special studs or bolts are used to connect the parts. The sleeve of the plain bearing is made in the form of a sleeve. In a one-piece assembly, it can be made of two halves. Shafts subject to deformation are usually fitted with self-aligning plain bearings.

The following materials can be used to make knots of this type:

• cast iron (for body);
• bronze, cast iron or plastic (for bushings).

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

Basic Requirements

Thus, bearings standards (or rather, compliance with them) allow us to produce the highest quality, durable and with excellent performance. The requirements for the nodes of this group are as follows:

• Materials and design of plain bearings must be such as to provide a minimum coefficient of friction between the housing and the sleeve.
• The strength and stiffness of the knot must be such that it can withstand any necessary loads.
• Welcome to the maximum simplicity of bearing design. When itinstallation should be no problem.
• Bearings should be manufactured in such a way that their surface has sufficient area to remove the heat generated during operation.

How they do it

Sliding and rolling bearings are manufactured at specialized large enterprises, which usually include two main workshops: thermal and mechanical. The assembly lines of such factories most often operate in automatic mode. In addition to them, modern spraying machines are also installed in the workshops.

In our country, the most popular components are those produced at domestic factories, as well as in Switzerland (SKF). SKF bearing standards are the same as Russian bearings.