Theoretical mass of bolts GOST 7798 70. Specifications and design of bolts with a hexagonal head. Reference regulatory and technical documents

Bolts made according to GOST, are among the most famous and widely used in the engineering industry, construction and some other areas. They have a hex head and a threaded shank. Bolts GOST 7798 belong to the accuracy class B, due to which they are in demand in a variety of areas.

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Technical characteristics of bolts according to GOST 7798-70

According to standards, the maximum length of products can reach 300 mm. The applied thread is full or incomplete, large or small, its diameter varies from 6 to 48 mm. In GOST, it is allowed to make partial changes to the design, namely, to the dimensions of the fasteners. Any adjustments are discussed individually and agreed with process engineers.

Bolts GOST 7798-70 are made from different types of steel (structural alloyed and low-alloyed, structural heat-resistant, carbon structural, heat-resistant, corrosion-resistant, heat-resistant) and non-ferrous metal alloys. It is possible to apply additional coatings to protect against aggressive factors and improve performance. The most common is the treatment of products with protective coatings based on zinc and nickel.

Photo: Bolt М6-6gх20.58.016

In GOST 7798-70 established standard strength classes. The most common and popular are 5.8, 8.8, 10.9, 12.9. Medium strength bolts (5.8, 8.8) are usually available. The manufacture of more resistant fasteners is carried out according to customer requirements. The length of the rod, the diameter of the thread and other characteristics depend on the scope and tasks assigned to the fasteners. Our company offers several options for the execution of bolts for use in various fields of production and construction.

Photo: Bolt М24-6gх110.58.096

Fasteners are made in 4 options:

• Execution 1. Flat hexagonal head with a chamfered top part (may have a cylindrical headrest);
• Version 2. The configuration is the same as in the first version. The lower part of the rod contains a hole in which a cotter pin can be installed;
• Execution 3. Hexagonal head with two locking drilled holes located at an acute angle and a solid shaft;
• Execution 4. The top plane of a head with a hole for marking of a product or other purposes.

Photo: Bolt М20-6gх80.58.016

Bolts are mounted with a wrench or a special nozzle on a hex head. Additionally, washers and nuts of a suitable size are used.
Fasteners manufactured according to GOST 7798-70 are used in mechanical engineering, construction and some other industries. With their help, rigid metal structures are connected; together with anchor sleeves, they are suitable for mounting equipment.

Capital Fasteners will manufacture bolts of any size in compliance with all standard parameters and GOST requirements. You can order fasteners with different types of coating, from a specific steel grade or a specific size. All stages of production are accompanied by strict quality control, so that the products are of high quality and excellent performance.

Photo: Bolt М6-6gх20.58.096

Nominal thread diameter,							(14)		(18)		(22)					(27)
thread pitch	large		1,25			1,75
	small			1,25
Rod diameter
Turnkey size
Head height								10,0	12,0	12,5	14,0		15,0			17,0	18,7	22,5	26,0	30,0
Diameter of circumscribed circle, not less than		10,9	14,2	17,6		19,9	22,8	26,2	29,6	33,0	37,3		39,6			45,2	50,9	60,8	71,3	82,6
Not less than			11,5	14,5		16,5	19,2	22,0	24,8	27,7	31,4		33,2			38,0	42,7	51,1	59,9	69,4
	at least	0,15						0,20											0,25
	no more
Bar hole diameter
Head hole diameter H15
Distance from reference surface to the axis of the hole in the head js15																		11,5	13,0	15,0

Bolt - a product in the form of a metal steel rod with external metric or inch threads on one side and on the opposite side - a hexagon head for a wrench or a hex socket head. A bolt constitutes a threaded connection by means of a nut or a threaded hole in any connected product.
The bolt according to GOST 7798-70 is made of carbon, stainless (A2 and A4) steels, as well as brass, copper, etc.
Bolt strength class 5.8; 8.8; 10.9 and less used strength classes 12.9; 4.8; 3.6. For galvanic coating of bolts, shiny or matte zinc, cadmium, nickel, chromium and burnishing (anodizing) are used.
The bolts offered by VIK-METIZ are widely used in the machine-building industry, at the construction site, in light and heavy industry, and other industries associated with production, together with nuts and washers of the same size. At the same time, bolts in accordance with GOST 7798-70 can be used for installation work in structures and equipment, together with drive-in anchors and anchor sleeves.

Bolt symbol in accordance with GOST 7798-70 version 1 with thread diameter 8 mm, hexagonal head size "turnkey" - 13 mm and length 35 mm, coarse pitch, thread tolerance 6g, strength class 5.8, uncoated:

Bolt М8-6g*35.58(S13) GOST 7798-70

Execution 2 thread diameter 20 mm, hexagon head size "turnkey" - 30 mm and length 100 mm, fine pitch -1.5 mm, thread tolerance 6g, strength class 8.8, steel grade 40X, coated 01-zinc and coating thickness 6 micron:

Bolt 2M20*1.5-6g*100.88.40X.016GOST 7798-70

Retail prices for bolts GOST 7798-70:

Bolts GOST 7798-70

A bolt is a fastening element of any connection, in this case, designed to connect flanged pipe fittings to a pipeline or to create a detachable flange connection for various purposes in a pipeline section.
The GOST 7798-70 bolt is a steel rod of a certain length, having a hexagonal head for a wrench at one end, and an external thread at the other end.

Requirements for fasteners used in flange connections, including requirements for GOST 7798-70 bolts, are given in GOST 20700-75. GOST 7798-70 bolts are manufactured from various steel grades. Depending on the purpose of fasteners and specific conditions of use, these can be carbon, stainless, cold-resistant, heat-resistant and other steels.
Bolt sizes GOST 7798-70:

Note: it is not recommended to use bolts with length dimensions enclosed in brackets. In order to correctly select fasteners, in particular GOST 7798-70 bolts, for connecting flanges, it is necessary to know exactly a number of parameters of the completed pipeline system. These include:

• working pressure in the pipeline;
• working environment temperature;
• working environment (aggressive, non-aggressive, liquid, gaseous, etc.);
• indicators of the external environment (ambient temperature, humidity, pollution with harmful substances, etc.);
• steel grade of installed flanges.

For reliable and tight fastening of a flange connection with bolts GOST 7798-70, nuts, washers and sealing material (paronite or rubber gaskets) are used.

An example of a symbol for a bolt of version 1 with a thread diameter d = 12 mm, with a turnkey size S = 18 mm, a length l = 60 mm, with a large thread pitch with a tolerance field of 6g, strength class 5.8, uncoated:

Bolt M12 - 6g x60.58 (S 18) GOST 7798-70

Bolts GOST 7798-70 are produced in various designs. Bolt head options are set by the manufacturer.

For bolts of execution 1, the diameter of the smooth part is equal to the nominal diameter of the thread. For bolts of version 2, the diameter of the smooth part is approximately equal to the average diameter of the thread. Bolts of version 1 are made without cotter holes, version 2 - with a cotter hole in the shaft, version 3 - with two through holes in the head, version 4 - version of the bolt head with a hole on the end of the bolt head. The through holes in the head of the bolts are designed for cottering with wire to prevent self-unscrewing.

Bolts GOST 7798-70 have a metric thread according to GOST 24705-2004 of a fixed length. The thread tolerance field indicates the accuracy of its execution. The larger the value of the tolerance field, the greater the deviation of the thread parameters from the nominal ones. For flange fasteners, including GOST 7798-70, the tolerance field for external thread is considered sufficient - 6g. The thread pitch is the distance between the tops of the threads. The thread pitch can be large or small. Coarse bolt thread pitch is used more often.

For carbon steel fasteners, the strength class is indicated by two numbers separated by a dot. For example: 4.6, 8.8, 10.9 etc.

The first digit indicates 1/100 of the nominal tensile strength, measured in MPa. In the case of 8.8, the first 8 means: 8 x 100 = 800 MPa (8000 kgf / cm²).

The second digit is the ratio of the yield strength to the tensile strength multiplied by 10. In our example, the second 8 means: Yield strength / 8 x 10. Hence the yield strength \u003d 8 x 8 x 10 \u003d 640 MPa (6400 kgf / cm²).

The yield strength is the maximum working load of the bolt. When calculating a bolted connection for a given load, a coefficient of 0.5-0.6 from the yield strength is used, i.e. with a yield strength of 6.4 tons, the calculated load will be: 6.4x0.5 = 3.2 tons.

Bolt dimensions (diameter and length) D(mm)xL(mm) according to GOST 7798-70
and GOST 10602-94 for flange connections for various pressures (Ru)

This type of bolt is the most sold and widely used. It should be noted that galvanized fasteners are recommended to be used only in dry rooms. For outdoor work and structures in aggressive environments, it is better to use hot-dip galvanized or stainless steel bolts A2-70, A4-70 or A4-80. For highly loaded joints, fasteners of strength classes 10.9 and 12.9 are used. Bolts with a controlled tightening torque are laid in the projects of especially important structures, such as bridges, skylights.

The closest analogue of DIN 933 bolts is DIN 931, which also correspond to GOST "y 7798-70. The size range of these bolts, as a rule, differs from DIN 933 in greater length.

Along with bolted connections, screw connections are used. There are two main differences between one and the other:

• bolts are used in tandem with a nut, and screws are screwed directly into the part, in which a threaded mounting hole is provided in advance;
• to install the bolt, a wrench is used that requires lateral access to the nut or hex head of the bolt, and screws are installed with various types of screwdrivers that need access to the end of the screw head.

Bolt marking

Hex head bolts are marked according to ISO 3506-1 or ISO 898-1. The general view of the marking is shown in the figure. In the conditionally lower part of the end of the bolt head, a stamp with a strength class is affixed, in the conditionally upper part - the brand of the manufacturer. Another marking option is a brand of strength class on one of the sides of the bolt head. The ISO 898-1 standard does not require a maker's mark, only a strength class.

Bolted connections

Bolted connections used in mechanical engineering are usually plug-in connections, as this allows them to be easily installed and removed: they are quite reliable and can be used in various conditions. In addition, standard fasteners are cheap fasteners.

Among the disadvantages of bolted connections, one can mention, for example, their reliability, which to a large extent depends on a torque that is difficult to control (alternative: bolts with controlled tightening torque). In addition, there are discontinuity points in bolts where the stress value reaches its maximum. The load in many bolted connections is a force directed along the axis of the bolt, as well as a transverse shear force in the perpendicular direction.

In thin-plate and lap bolts, the transverse shear force can act directly on the bolt, causing shear stress. Corresponding connections are designed in such a way that the friction force caused by the axial force of the bolt transfers the transverse shear force from one part to another. In this case, the torsional stress associated with the torque of the nut is only the shear stress that occurs in the bolt shaft.

It follows that the most important characteristic of the bolt, in terms of the strength of the connection, is the tensile strength. Under static loading of a bolt, it can fail as follows:

• the bolt fails when the tensile stress exceeds the tensile strength;
• the bolt thread is cut off;
• the thread of the nut is cut off.

If the threads of both the bolt and the nut are strong enough, then when the axial load is transferred from the bolt to the nut, the bolt should fail. It is cut off either at the thread or at the stem, provided that the head has not separated.

The threading method has a great influence on the fatigue strength of the bolt metal. There are two ways to make a thread: cutting (cutting on a lathe) or forming (rolling). Standard bolts are made almost exclusively by forming, and for extra large or strong bolts - by cold forming (cold rolled bolts). In the manufacture of bolts of very large or, conversely, very small diameters, it is possible to use hot rolling. The fatigue strength of bolts with hot rolled threads is higher than that of hardened bolts. The increase in fatigue strength is due, for example, to finishing of the thread surface, molding at the root of the thread, as well as compressive stress caused by plastic molding on the thread surface.

To achieve a reliable bolted connection, the correct pre-tightening is critical. It should be sufficient, but not too large. The more accurate the pre-tightening is, the easier and cheaper it will be to design the connection, but, on the other hand, with an increase in the tightening accuracy, the cost of the bolting installation procedure increases.

Insufficient pre-tightening can lead to:

• displacement of the joint surface under the action of axial load;
• increase in bolt stress amplitude;
• bolt aging;
• unscrewing the nut during vibration;
• slip of the joint under the action of shearing moments.

Too much pre-tightening can lead to:

• static overload of the bolt during the action of an external load;
• unscrewing the bolt under external tensile load as a result of plastic elongation;
• breakage of the bolt when it is pre-tightened.

It is necessary to maintain sufficient tension in the bolted connection during the entire period of operation. The following causes may lead to damage to the connection thread:

• bolt break;
• thread cutting;
• unscrewing the nut;
• settling of connection details.

Examples of using bolts GOST 7798-70 / DIN 933