Methodical connection with a hairpin. Symbolic image and designation of the thread in the drawings Symbolic designation of the stud in the drawing

Bolt is metal part in the form of a cylinder with an external thread. At the end is placed the head necessary to fix the part on the surface. The shape of the head depends on the requirements for a particular connection and installation conditions. Most often, the bolt is mounted with a key. Therefore, hex heads are more popular.

Head shapes

• Hexagonal.
• Square.
• Round.
• Cylindrical.
• Conical.

Bolt designation

For a long time, competing manufacturers used their own standards. This system has undergone a number of major changes, after which all parts began to meet certain parameters and be marked according to them. This provision was necessary in a rapidly developing industry, in which the lack of standards complicated the production process.

At the moment, there are three unified standards according to which markings are applied to the bolts for ease of use:

• GOST;

The recommended designation scheme for bolts and screws according to GOST is used in the CIS countries. The requirements of quality standards apply to food products, manufactured goods, clothing, etc. ISO is an international metric system adopted in 1964. At the moment, this standard is used in many countries around the world. DIN is accepted and used in Germany. This system has several standards.

Bolt head markings

Basic information about the bolt can be read on its head, it indicates important parameters details. Designations are necessary to select a suitable bolt for carrying out various kinds works. Special meaning has a characterizing performance characteristics connections. In the case of using bolts in the manufacture of furniture, they are extended minimum requirements strength, which is associated with a small load on the part. If necessary, use threaded connection on difficult industrial facilities higher requirements are placed on the bolt.

Also, the bolt is stamped with the mark of the production on which the part is made. Additionally indicate the direction and nature of the thread. Another milestone marking is the application of information about the composition of the alloy from which the bolt is made: material, steel grade and resistance to chemical components.

Bolt designation applied when marking

All bolts, except for cylindrical ones with a hole for a hex key, are marked on top of the head. Cylindrical products are marked on the end side. The designation of bolts is applied in the form of symbols recessed into the head or raised signs. Convex markings on the end of the head are rarely applied, most often the marks are deepened. Otherwise, the height of the designations is clearly regulated depending on the diameter of the part.

• Two digits on the head of the bolt indicate the strength class of the product. This value has great value. It depends on it whether the connection can withstand the load that is necessary in this case. There are 11 strength classes, they are denoted by two symbols with a dot between them. The first designation characterizes the strength of the bolt, and the second - the fluidity of the material from which it is made. At large industrial facilities, in auto and aircraft modeling, this indicator is given special attention. Mismatch with marking symbols can cause damage and create emergencies on the object. Designation high strength bolt starts from marking 8.8 to 12.9.

• Manufacturer's mark - to a stamp with the manufacturer's symbol, which indicates that before leaving production, the part has passed all mandatory quality checks and meets the parameters printed on the part. The absence of a maker's mark is possible, but may be a sign that the part does not meet quality standards.
• Thread designation. It is obligatory to put information on the bolt head with a left-hand thread. It is indicated by an arrow. Connections with right-hand threads are not marked separately.
• Letters on the head. These symbols may indicate the metal from which the bolt was made and the grade of steel. Designation A2 and A4 are applied to bolts made of resistant to chemicals and air materials. The underline indicates that the part was made from low carbon Martian steel.

Compliance with GOST

Let's consider what is the designation of bolts according to GOST. All products must comply with state quality standards. Requirements for bolts in Russia and the CIS countries are prescribed in GOSTs. These standards have been passed down to us since Soviet Union practically unchanged.

There are several GOSTs related to different types bolts. They indicate not only the requirements for quality, strength, compliance with dimensions and universal parameters, but also a scheme for designating parts when marking and indicating a certain type of bolt in the drawings.

What is in the standards?

There are a number of requirements and designations for such products. Bolts according to GOST must comply with all prescribed quality standards. In addition, the documentation contains layouts that this type of product must comply with. The drawings attached to the state quality standards indicate the design features of the bolt, symbols and the layout of symbols for marking.

Basic requirements according to GOST

• The parts must be completely free of traces of metal corrosion, large defects and cracks. The presence of the latter means that the product does not meet the quality standard.
• Stamping cracks are allowed on the surface of the part, provided that the length of the crack is less than the diameter of the bolt, and the width and depth are not more than 4% of the bolt diameter. Otherwise, the product cannot meet the state quality standard and should be discarded.
• According to GOST, rolling bubbles can be on the bolt, but their size cannot be more than 3% of the product diameter.

• A bolt that has torn damage that goes into the thread or bearing part is also rejected.
• According to the quality standard, products that have defects at the end of the head can be suitable provided that the defect does not exceed the size of the circle above the limit value.
• A slight point change in the color of the alloy in the form of ripples is allowed.

Quality control

All products are controlled by two parameters: visual compliance with the standard and metallographic examination. During visual quality control, the product is inspected for deviations from state standard by size and diameter, the presence of mechanical damage and defects, as well as the presence of corrosive changes. Metallographic evaluation involves a magnetic study. For more detailed study composition of the part, the metal etching method can be used. These techniques make it possible to accurately determine the amount of impurities in the alloys and the nature of the material from which the product was made. If a part does not meet the standards, it will be rejected.

Scheme for decoding symbols of bolts

The bolt symbol is presented as a long list of numbers and letters, each of which denotes a specific product parameter. This information is indicated on the manufacturer's factory packaging and provides comprehensive information about the part.

At first glance, it may seem that it is very difficult to decipher what is indicated on the package, but this is not so. All designations go in a certain order and characterize separate parameter products. One of the most commonly used quality standards is GOST 7798-70, which describes the main parameters of hex bolts. Consider the decryption of the record using an example.

Product 2M12x1.50LH-5gx50.66.A.047 GOST 7798-70

• Product. In this place, the name of the part is written: bolt, screw, stud, etc.
• The quality class is dictated by GOST, so it may not be specified. There are three classes - A, B and C, where the designation A indicates the highest accuracy of the part.
• The number 2 indicates performance. There are only four types of performance. Version 1 is not specified by default.
• M is the thread type designation. The first letter of its name is indicated: metric, conical or trapezoidal.
• 12 - bolt diameter in millimeters.
• 1.5 - thread pitch, may not be specified if it is the main thread for a given diameter.
• LH - designation that this bolt has a left-hand thread. If the product is made with a main (right) thread, then this will not be indicated.
• 5g indicates which accuracy class the thread was cut to. Classes can be numbered from 4 to 8, where 4 is the most accurate class.
• 50 - bolt length (designation in millimeters).
• 66 - product strength class. On the bolt head, these indicators are placed with a dot between the numbers. AT symbol do not put a dot.
• A - a characteristic of the steel used for the manufacture. In this case, it is indicated that the bolt was cast from automatic steel. The letter C says that the part was made of calm steel. This parameter characterizes the strength class of the bolt. This means that the class is higher than 8.8.
• 047 indicates the type of coating and its thickness on the product. There are several types of coating - from 01 to 13. In this case, the type of coating is 04, and its thickness is 07 microns.

The symbol for bolt fasteners allows you to fulfill the requirements for a particular product and design as accurately as possible. Compliance with quality standards is the key to successful reproduction of project requirements. The mark that the product complies with GOST allows you to study the properties of the part according to these documents and means its full compliance with the standards. GOST standards correspond to others unified systems. To transfer from one system to another, it is enough to use metric table translation.

Stud connection

Exercise3 . On an A3 sheet, draw a stud and a nut according to the action- real dimensions and their connection - according to relative. Draw a threaded hole for the stud. Stud of normal accuracy class, execution 1. Nut in accordance with GOST 5915-70. Place a spring washer GOST 6402-70 under the nut. Take the initial data from table 3.1.

An example of a drawing of a pin connection is shown in fig. 3.3.

Table 3.1

Initial data for building a connection with a hairpin

3.1. Image of a hairpin connection

On a sheet of drawing paper in A3 format, places are marked for the image of the stud, nut, hole for the stud and connections. Outline the location of the connection types (main, top and left view) with centerlines. On the main view outline the contours of the details m and n. According to the task, determine the length of the screwed end of the stud l one . In detail n draw a threaded hole according to those shown in Fig. 3.1 relative sizes ( l 2 and l 3). In this hole, the threaded end of the stud is depicted. The stud is screwed in to the full length of the thread l 1 .

On the main view of the drawing mark the thickness of the washer s = 0,1sd; nut height: H = 0,8d; and thread exit for the nut: k = (0,25…0,5)d or (0.2…0.4) P. determine the length of the pin l = m + s + H + k and the length of its thread: l 0 = 2d + 2p.

In the top view, circles are drawn:

d- outer diameter of the thread;

d 1 = 0,85d – conditional image threads at the end of the stud (thread inner diameter);

D = 2d- the diameter of the circle for constructing the hexagon of the nut;

D w = washer diameter.

From a top view of main view and the left view projectively transfer the dimensions of the faces of the nut, the diameter of the washer d w, conditional image of the thread d 1 .

Determine the bevel size with = 0,15d and at the end of the stud hole diameter d 0 = 1,1d in detail m, and put them on the drawing.

The sequence of drawing chamfers of a hex nut is described in clause 3.2.

Hatching the elements of the parts shown in the sectional drawing.

Apply dimensions. On this assembly drawing, it is necessary to put down the dimensions:

d- stud thread diameter;

l- the length of the pin;

l 0 - the length of the nut end of the stud;

l 1 - the length of the end of the pin screwed into the part;

S- turnkey size.

Dimensions l 1 , l 0 and S is consistent with GOST.

Then the extra lines are removed from the drawing and circled around it.

* Dimensions must be coordinated with GOST

Rice. 3.1. Building a connection with a hairpin according to conditional relationships

3.2. Stud drawing. It is performed in accordance with the standards in the following sequence: (Fig. 3.2). Based on the task data, according to table 3.1, we determine the GOST for the hairpin. Stud sizes: d, p, l, l 1 , l 0 are known from the assignment and execution of clause 3.1. chamfer value with determined according to table 01.

The hairpin is drawn in one projection, and its axis must be parallel to the main inscription of the drawing. Its designation is written on the drawing.

Rice. 3.2. Hairpin

3.3. Nut drawing. It is performed in accordance with GOST 5915-70 in the following sequence (Fig. 3.3)

Rice. 3.3. screw

On the working drawings, the nuts are drawn with the image of the line of intersection of the conical surface (chamfer) with flat faces.

1.3.1. Nuts are depicted according to actual dimensions, for which they write out from the corresponding GOSTs:

d- thread diameter;

D- diameter of the circumscribed circle around the hexagon (auxiliary circle for constructing a regular hexagon);

S- turnkey size;

H- the height of the nut.

1.3.2. On the places of the images, axial and center lines are applied.

1.3.3. In place of the top view, a regular hexagon is built by dividing the circle D and inscribe a circle with a diameter D 1 ≈ (0,9...0,95)S.

1.3.4. In place of the main view and the view on the left, mark the height of the nut H, project a hexagon (from a top view) and a chamfer diameter D 1 (points 1" and 3""). From the chamfer diameter D 1 (points 1" and 3"") draw straight lines at an angle of 30° to the horizontal until they intersect with the edges of the hexagon (point 2") in the main view and the face in the left view (4"").

1.3.5. The projection of point 2" will be the lowest point of the line of intersection (hyperbola) of the conical surface with the plane, and the projection of point 3" will be the highest.

1 3.6. The resulting highest and lowest points of the hyperbola are connected by a smooth freehand curve, and then they are circled along the pattern. Usually the line of intersection (hyperbola) is replaced by an arc of a circle. Arc radius R take equal R = 1,5d and draw an arc through the lowest points of the intersection line (points 5 "and 6"). The center of the great arc of the circle will be at centerline and at a distance R from the lowest point (points 5" and 6"). Small arc center R 2 circles is located graphically as shown in Fig.1.3. Radius of curvature R 1 in the left view is used equal R 1 = d and also pass it through the lowest points (2"" and 5"").

1.3.7. Top view outside diameter threads are represented by an arc of 3/4 circle.

Table 3.2

Stud sizes (excerpts from GOST)

Notes: 1. Standard range of stud lengthsl:10, 12, 14, 16, 16, (18), 20, (22), 25) (28), 30, (32), 35, (38), 40, (42), 45, (48), 50, 55, 60, 65 , 70, 75, 80, 90, (95), 100, (105), 110, (115), 120, 130, 140, 150, 160, 170, 180, 190, 200, 220, 240, 260, 280, 300.

Table 3.3

Hexagon nuts of normal accuracy (GOST 5915-70)

Notes: 1. Execution 1 applies tod = 18 mm and more, and version 2 , ford <16 мм.

2. An example of a symbol for a nut with a thread diameter of 12 mm and dimensions in accordance with GOST 5915-70 version 1, with a large thread pitch:

Nut M12 GOST 5915-70.

The same, version 2, with a fine thread pitch of 1.25 mm:

Nut 2M12 x 1.25 GOST5915-70.

Rice. 3.4. An example of a hairpin connection

The scope of bolts is incredibly extensive, and in order to choose them correctly, you should familiarize yourself with their types and designations in accordance with GOST. After reading our article, even a non-technical person will be able to cope with this task.

1

This fastener has found its wide application. It is impossible to imagine an industrial area in which bolts would not be used. Construction, aviation, machine building, shipbuilding, and just life - in all these areas they are indispensable. With their help, you can get a strong, reliable and, which is very convenient, a detachable connection. This fastener consists of two parts - a threaded rod and a head. It most often has a hexagonal shape.

Hardware is classified depending on the purpose, shape and strength of the product. Let us dwell on the concept of strength class in more detail. This characteristic determines the mechanical properties of the fastener. There are 11 classes in total. They are denoted by two numbers delimited by a dot. The first number multiplied by 100 corresponds to the nominal temporary resistance. For example, for fasteners with an accuracy class of 3.6, it is 300 N / mm 2. And multiplying the next figure by 10, we find out the nominal yield strength. For the above bolt, it will be 60 N / mm 2.

furniture bolt

There are special ones with a strength class of not more than 5.8. They are mainly used in the construction and furniture industries. But plow and road fasteners can already have a higher strength class - 8.8. The first found their application in the installation of attachments for agricultural machines. Engineering products have the highest strength class (up to 12.9), since they are involved in the assembly of critical structures.

The bolts are hinged in shape, manufactured in accordance with GOST 3033–78. Their feature is the head, made in the form of a movable part of the swivel joint. But the upper part of the eyebolt, the features of which can be found in more detail by studying GOST 4751–73, is a ring. These products are especially relevant for the installation of installations, unloading and loading operations, for towing. And all thanks to the unique design. The bolt shaft is screwed into the mounting hole, and a hook can be hooked onto the ring and a rope can be tied.

Anchor bolts (GOST 24379.1–2012) are indispensable if you need to fix a heavy object on the wall, hang something from the ceiling, or fix a massive structure. This is a spacer element. During its tightening, the nut located at the end of the product is drawn into the body and expands it.

The bolt heads may be different. The most common can rightfully be called a hexagon, which is ideal for a wrench. These products are manufactured in accordance with the requirements specified in GOST 7798.7817-80, 10602-94 and 18125-72. But there are also hardware with semicircular and countersunk heads (GOST 7783-81, 7801-81, 7802-8 and 7785-81, 7786-81, 17673-81). Noteworthy products with a flange. Structurally, they resemble standard parts, only they have an additional flange. It looks like an ordinary nut.

2

The symbol for hardware appeared in the USSR at the beginning of the last century. Absolutely all parameters are indicated in the full designation, starting from the name of the hardware and its strength class and ending with the standard number. It consists of 13 items. The name of the product is indicated first, followed by the accuracy class. The third position is occupied by the performance of the product. Depending on the state standard, it can be in 4 versions. If version 1 is used, then it is not indicated. Products of execution 2 have a hole for a cotter pin at the end of the threaded part, and 3 - a pair of through holes in the head. Hardware version 4 does not have any additional holes.

On the drawings placed in the directories, such parameters as length, diameter of the rod and threads for each type of hardware are marked. Further, the designation specifies the nominal diameter, pitch, direction and tolerance field of the thread. The eighth position is occupied by the length of the product. Behind it is the strength class. Moreover, in this case, the values ​​of the nominal tensile strength and yield strength may not be delimited by a point. The next is an indication of the use of autonomous or calm steel. Next comes the grade of the material. The last two positions are occupied by coverage information and the state standard number.

3

In this paragraph, we will focus on the main ones. If we are talking about hexagon head bolts, then the strength class, the manufacturer's trademark, must be indicated. A special designation is applied to products with a left-hand thread. Marking can be both recessed and convex, and the size of the characters is completely determined by the manufacturer.

Bolt marking

In the case when low-carbon martensitic steels are used for the manufacture of hardware of strength class 10.9, the class is underlined by a straight line. A designation is applied to the end or side surface of the head. In the latter case, the marking signs are made predominantly in-depth. True, convex symbols are also allowed, the main thing is that they do not lead the parameters of the product beyond the limits of the norms. Character sizes are determined by the manufacturer.

4

There are very serious requirements for hardware, which can be found in GOST. Also in the state standards are given and sketches of products. The drawings show not only the design of the bolts, but also the location and marking features. On the surface of the rod elements there should be no traces of corrosion, mechanical damage and stress cracks. It is possible to have stamping cracks with a length of less than 1d, a width and a depth not exceeding 0.04d of a hardware on the heads and ends of the bolt rods. The depth of rolling bubbles should be less than 0.03d.

Bolt types

Products with flaws are also rejected if they go beyond the chamfer at the end of the head or go to the supporting surface. And the defects located on the edges of the hexagon should not take the circle beyond the limiting dimensions. The width of the flaws located on the edge of the recess of the hexagonal head cannot exceed 0.06d. And their depth should be less than the height of the recess. The presence of rowan is also allowed. For bolts with a diameter less than M12, the depth of the defect can be no more than 0.25 mm. For hardware of larger diameter, this parameter should not exceed 0.02d. Products with slight burrs on the bearing surface of the head are not rejected.

Finished products are subject to two types of control: visual and metallographic. With the help of the first it is possible to identify most of the defects. In this case, visual control is carried out without the use of any magnifying devices. In the latter case, we are talking about magnetic testing methods or deep etching.

When preparing technical design documentation (including such as working and assembly drawings), developers need to name its contents in some way. For this, words are used that reflect the meaning of these entities.

When working drawings are drawn up, a word such as “ hairpin". In technology, it means a rod used as a fastener that has threads at both ends.

One of its parts with carvings, hairpin is screwed into the main part, and the other passes with a gap through the hole of the part that is supposed to be fixed, and its fixation is carried out by screwing the nut onto the second threaded part hairpins. There is another mounting option: it is threaded into the holes of the two fastened parts hairpin, and nuts are screwed onto its ends.

It should be noted that the scope of such fasteners as studs is practically unlimited. They are widely used in mechanical engineering, instrument making, many other industries, construction. Studs are used in the assembly of modern internal combustion engines, other vehicle components, in the installation of ventilation systems, heating systems, water supply and gas supply. Installation of billboards, fixing boards and timber during the installation of wooden buildings, as well as many other processes are not complete without studs.

The most common and most widely used threaded parts are screws, bolts, nuts, studs and inserts. It is with their help that the largest number of various detachable connections are formed.

Which type of connection to use in each particular case is determined by factors such as:

The strength of the material from which the parts are made;

Features of their design and manufacturing technology;

The frequency with which assembly and disassembly of the connection will be carried out during operation.

Bolted connections are used only in cases where there is sufficient free access to both the bolt head and the nut. In addition, it makes sense to use them in order to fasten together parts that have a relatively small thickness, also when the assembly and disassembly of the connections will be carried out repeatedly. In the last of the listed cases, it also makes sense to give preference to connecting with screws or studs (especially in cases where the thickness of the parts to be joined is really large).

In cases where access is provided by the mounting tool only from one side (for example, only to the nut), it is most preferable to use screws and studs to fasten the parts together. It should be noted that if the connection will experience significant loads, then screws should not be used, but it is better to use studs instead. Their fixation (locking) is carried out directly in the body parts. It is necessary in order to prevent them from unscrewing when it is necessary to unscrew the nuts. Locking is carried out with the help of adhesives, screwing on the thread run, landing on the thread with an interference fit.

The main materials that should be used in the manufacture of studs, nuts, bolts and screws, as well as their mechanical parameters, are specified in GOST 1759–82. According to this document, 12 strength classes are provided for studs, screws and bolts manufactured from alloyed and carbon steels, and seven for nuts. As for the choice of material for the production of a particular product, it is determined by the working conditions and manufacturing technology.

For mass production of bolts, steel grades 16XSN, 15X, 15, 10 are used, cold heading technology is used. The thread on such bolts is rolled. They are protected from corrosion by applying oxide films or galvanic coatings.

All detachable connections can be divided into 2 groups: threaded and non-threaded.

To threaded include standard fasteners threaded parts: bolts, screws, studs, nuts. All fastener threaded products have a metric thread with a large pitch, less often with a fine one, and are manufactured in accordance with the relevant standards that establish requirements for the material, coating and other conditions for the manufacture of these parts. Each fastener has a symbol, which reflects: accuracy class, shape, main dimensions, material and coating.

Bolted connection

A bolted connection consists of 5 parts: two parts to be connected, a bolt, a washer and a nut.

Rice. 1. Visual representation of a bolted connection.

Bolt- fastener, which is a cylindrical rod, usually with a hexagonal head at one end and a screw thread at the other.

Bolt heads can also have a different shape: square, rectangular, semicircular with a square underhead or mustache. In most designs, the head has a chamfer that smoothes the sharp edges of the head and facilitates the position of the wrench when screwing (Fig. 2)

Rice. 2. Bolt and its main elements.

The working drawing of the bolt is made according to the dimensions taken from the corresponding standard (GOST 7798-70).Please note that the parts to be connected shaded in different directions. This is done in order to make drawings easier to read, making it possible to distinguish adjacent parts by hatching.

Rice. 3. Drawing of a bolted connection.

Rice. 4. Simplified image of a bolted connection.

Each bolt thread diameter d corresponds to certain dimensions of its head. With the same thread diameter d, the bolt can be produced in various lengths l, which is standardized. The thread length of the bolt is also standardized and is set depending on its diameter d and length l.

Designation

For example, the entry "Bolt M12x1.25x60 GOST 7798-74" means: a bolt with a metric thread of 12 mm, a pitch of 1.25 mm (fine), a bolt length of 60 mm.

With a conditional image of a bolted connection:

a) chamfers on the heads of bolts, nuts and the rod are not depicted,

b) the gap between the bolt shaft and the hole in the parts to be joined is not shown,

c) the thread is conventionally depicted along the entire length of the rod,

d) in views perpendicular to the thread axis, the thread is depicted by a circle corresponding to the outer diameter of the thread; washers are not depicted in the same views.

Bolts, nuts and washers on the assembly drawings are shown uncut.

nuts

screw- a part of a prismatic shape, equipped with a through, and sometimes a blind axial threaded hole.

Structural forms of nuts are very diverse. Most often, nuts are hexagonal with two chamfers, square with one chamfer, hexagon slotted and crowned, having radial grooves for locking them with cotter pins.

Rice. 5 hex nuts

In mechanical engineering and in everyday life, special nuts are often used: round, wing nuts, winged, round slotted, cap, square, etc.

Fig. 6. Types of nuts: a) hexagonal, b) castellated, c) square,

d) slotted, e) wing nut, f) winged, g) round slotted.

Nuts are screwed onto the threaded end of the bolt, while the parts to be joined are clamped between the nut and the bolt head.

Hex nuts according to GOST 5915-70 are most commonly used in two versions: with two and one external chamfers (Fig. 6, a). Wing nuts used for tightening nuts without a wrench (Fig. 6, e) are selected according to GOST 3032-76.

The drawing of the nut is made according to the dimensions taken from the relevant standard.

Rice. 7. Nut drawing

Designation

For a nut, indicate the diameter and type of thread.

The entry "Nut M16 GOST 5915-70" means: a nut with a metric thread, having a diameter of 16 mm, a large pitch.

washers

Washer- a flat disk with a round hole in the center.

There are flat washers and spring washers.

Flat washers are used in the following cases:

a) if the holes for bolts or studs are not round (oval, rectangular), when the bearing surface of the nuts is small;

b) if it is necessary to protect the supporting surface of the part from scuffing when tightening the nut with a wrench;

c) to eliminate the possibility of self-unscrewing nuts when they experience vibrations or temperature changes;

d) if the parts are made of soft material (aluminum, brass, bronze, wood, etc.), in this case a large supporting surface under the nut is needed to prevent the part from collapsing.

There are washers round (Fig. 8, a), square (Fig. 8, b), spring, multi-bladed (Fig. 8, c), locking, spherical (Fig. 8, d) (eliminating the skew of the stud or bolt when changing position parts of the parts to be joined), quick-detachable (Fig. 8, e), oblique (Fig. 8, f) (for leveling the slopes of the shelves of channels and I-beams), etc.

Rice. 8. Washers: a) round, b) square, c) multi-bladed, d) spherical, e) quick-release, f) oblique.

flat washers have two executions: execution of 1 accuracy classes A and C - without chamfer; execution of the 2nd accuracy class A - with chamfers (Fig. 7, a).

Spring washers they are a left-handed helical protrusion (Fig. 9), they serve to protect threaded connections from self-unscrewing during operation. The spring washer has a cut and when the nut is tightened, the washer abuts against the end of the nut and the bearing surface of the part, thereby delaying the reverse rotation of the nut or bolt. In addition, the spring washer provides a constant tension between the threads of the bolt and the nut and thereby helps to delay the reverse rotation of the nut.

Rice. 9. Spring washers

Rice. 10. Spring washer: visual image and drawing.

Washers can be of various configurations. The sizes of washers for bolts and nuts are selected according to GOST 11371-78.

Designation

For washers indicate the diameter of the bolt.

The entry "WASHER 12" means: washer for a bolt with a diameter of 12 mm.

screw connection

Screw- a threaded rod, at one end of which there is a mortgage head.

The screw differs from the bolt by the presence of a slot (slot) for a screwdriver.

Screws are also made from wood, metal, plastic and other materials.

In modern life, the use of screws is quite extensive. Screws are used in a wide variety of industries: in mechanical engineering, railway construction, electrical engineering, construction, furniture production, equipment manufacturing, electronics, installation work, and repair. A high-quality screw is considered a very important element in the construction or repair of houses. In furniture factories, a screw is indispensable in order to be able to combine the parts of the furniture produced. In such enterprises, the screw is usually wooden or plastic.

Screws are divided into two types: fixing and adjusting.

Main types fixing screws differ in the shape of the head (cylindrical, semicircular, secret, semi-secret).

Rice. 11. Mounting screw and its parameters.

Screws are made with heads of various shapes: cylindrical GOST 1491-80, with a semicircular head GOST 17473-80, with a countersunk head GOST 17475-80, etc. The heads can be partially or completely (Fig. 12) recessed (sunk).

Rice. 12. Fixing screws

Set screws are used to adjust gaps and fix parts during assembly.

Rice. 13. Set screw application example

Rice. 14. Set screw and its parameters.

Some types of set screws do not have heads.

The screw connection consists of 3 parts: two parts to be connected and a screw.

Rice. 15. Screw connection: illustration.

Rice. 16. Screw connection: drawing and conditional image.

Stud connection

Hairpin- a cylindrical rod, at both ends of which a thread is cut.

The pin is applied:

a) when the parts do not have a place to place the bolt head,

b) if one of the parts has a significantly greater thickness, then it is uneconomical to use a bolt that is too long,

c) if frequent disassembly of the connection is necessary, and the thread in the part does not have sufficient resistance due to the properties of the material (aluminum alloy, cast iron).

At one end, the stud is screwed into the blind hole of the part (landing end) for the entire length of the thread, and at the other end, a nut is screwed, under which a washer is placed (coupling end).

Rice. 17.

Studs come in a variety of shapes and types. For example, threaded studs M2 - M12 with a length of 10 to 80 mm are of two types: for connecting parts, one of which is threaded, and for connecting parts with smooth holes. Studs of the first type have threads of various lengths at the ends of the rod, and studs of the second type have the same thread length at both ends or a thread cut over the entire length of the rod. Studs of both types may have an unthreaded part of a smaller diameter than the thread.

Fig.18. Hairpin and its parameters.

Stud sizes are standardized. The length b 1 (this length includes the thread run) of the screwed threaded end is determined by the material of the part into which it must be screwed, and can be of different sizes. Threaded stud end l designed for screwing a nut onto it when connecting fastened parts. Under stud length l refers to the length of the rod without a screw-in threaded end. The length of the threaded (nut) end l 0 can have different values, determined by the diameter of the thread d and the length of the stud l.

When depicted in the drawing, the line defining the thread boundary at the lower end of the stud is always drawn at the level of the surface of the part into which the stud is screwed.

Rice. 19. Visual representation of the connection with a hairpin.

Rice. 20. Making a drawing of the connection with a stud.

The thread is conventionally depicted along the entire lengthhairpins. The question of drawing in one way or another depends on how many studs are involved in the connection.

Rice. 21. Hairpin connection: a) drawing; b) conditional image

Designation

"Stud M10x60" should be understood that the stud has a metric thread, its diameter is 10 mm, and the length is 60 mm (to the screwed end).

The image of fasteners has to be encountered on assembly drawings. Bolts, screws, studs, nuts and washers on the assembly drawings are shown not cut. In these drawings, bolts, studs and screws are drawn in relative size and simplified. This means that the size of the individual elements is determined depending on the outer diameter (d) of the thread.