Where is thread used? Wood carving elements

Threads according to their intended purpose are divided into the following groups:

1. Mounting threads. Designed for fastening parts, usually metric, single-start.

2. Fastening and sealing threads. They serve both to fasten parts and to prevent liquid leakage, usually pipe threads.

3. Threads for transmitting motion or running threads, often multi-start.

Types of threads according to profile.

According to the type of thread profile, they are divided into:

Metric thread(GOST 8724-81 (ST SEV 181-75) - diameters and pitches and GOST 9150-81 (ST SEV 180-75) - thread profile.

The thread profile is an equilateral triangle. The tops of the screw thread profile are blunted in a straight line by H/8, and the nuts by H/4. The profile of the depressions often has a rounding with a radius of H/6. Blunting of the profile is done to reduce stress concentrations and increase the durability of the cutting tool. There are threads with a large pitch, called the main thread, and with a fine pitch, which has 4 types. Fine pitch threads are used for large thread diameters, for thin-walled parts where the thread is used for adjustment. Suitable for diameters from 1 to 600 mm. A thread with a large pitch or the main one is designated M with an indication of the outer diameter (for example, M-20), and with a small pitch, the type of pitch is additionally indicated (for example, M20x2), the thread is a fastening thread, less often a running thread.

Pipe cylindrical thread(GOST 6357-81 (ST SEV 1157-78). The thread profile is an isosceles triangle with a profile angle of 55 0. It is made with a profile rounding with a radius of r = 0.137 and without gaps at the tops and bottoms for a good seal. Designed for connecting pipes and pipeline fittings and is a fastening and sealing thread. It is used in the diameter range from 1/8" to 6". It is an inch thread and is designated G with an indication of the outer diameter (for example G2").

Trapezoidal thread(GOST 9484-81, ST SEV 639-77 - diameters and pitches and ST SEV 146-75 - thread profile - for single-start threads and ST SEV 185-75 - for multi-start threads). The thread profile is trapezoidal with a profile angle of 30 0. Applicable in the range from 8 to 640 mm. Serves as a running thread. It is designated as Tr indicating the outer diameter, number of starts for multi-start threads or pitch (for example, Tr190x(2x8) or Tr190x8).

Thrust thread (GOST 10177-82 or ST SEV 1781-79). The profile is an unequal trapezoid with a profile angle of 33 0 and profile inclination angles of the working side of 3 0 and the non-working side of 30 0. Designed to transmit force in one direction. Also serves as a running thread. Suitable for diameters from 8 to 280 mm. Designated as Pack indicating the diameter and pitch (for example Pack 80x10).

Rectangular thread- is currently being replaced by persistent or trapezoidal, not standardized. It has less strength, is difficult to manufacture, creates a gap when worn, etc.

Round thread is not very common in mechanical engineering.

Tapered inch and pipe threads used for connecting pipelines to parts.

Fasteners.

Fasteners include bolts, screws, studs and nuts. These also include washers. Bolts are used to fasten parts that are not very thick; they do not require threading in the part. Structurally, they consist of a body with a chopped honour, and a head of various shapes, usually hexagonal. Conventionally, a bolted connection is depicted in the drawing, as shown in Fig. 1.3.

Screws resemble bolts in appearance or are used without a head; they are screwed into the part located last from the head. Conventionally, a screw connection is depicted as shown in Fig. 1.4.

Studs are used in the same cases as screws, but when the material of the threaded part does not provide sufficient durability of the threads when disassembling and assembling connections. Conventionally, a connection using a stud is depicted in the drawings, as shown in Fig. 1.5.

The listed parts are manufactured with normal and high precision.

The nuts are a hexagon with a height of 0.8 d to 1.6 d with an internal threaded hole and are used to tighten parts.

The washers are designed to protect the surfaces of parts from damage when tightening. They are installed under the nut or head, depending on what is being turned. Special washers also perform a locking function.

Fasteners are most often made of steel, and in special designs they can be made of non-ferrous metals. The material of the remaining bolts, screws, and studs is conventionally divided into 12 strength classes according to GOST 1759-70. The strength class is indicated by two numbers. The first number, multiplied by 100, indicates the minimum value of the tensile strength σ in MPa, the second, divided by 10, indicates the ratio of the yield strength σ t to the ultimate strength, and the product of these numbers multiplied by 10 is the yield strength in MPa.

For example, strength class 4.8 indicates that the part is made of steel with the mechanical characteristics:

σ in = 400 MPa, σ t = 4.8 = 320 MPa and σ t / σ in = 0.8.

Steel grade Steel 10 has these properties.

The material of the remaining nuts and washers is divided into 7 strength classes. The strength class is indicated by a number that, when multiplied by 100, gives the value of stress from the test load in MPa. For example, strength class 4 shows that the nut or washer is made of steel grade St.3, because σ in = 4*100 = 400 MPa.

You need to look at the specific strength classes yourself in /2/. The strength class is recorded in the symbol of the fastener.

Conventional image of fasteners.

According to the standards, the symbol includes the name of the part, design, thread diameter, fine thread pitch, degree of accuracy and main thread deviation, length of the bolt, screw (without head) or stud, strength class, indication of the use of mild steel, type of coating, coating thickness and GOST for the part. If the design is normal (without holes), the thread is basic, the use of mild steel is not regulated, the product is uncoated, then this information is excluded from the designation. When manufacturing parts from alloy steels, the grade of steel is also indicated after the strength class.

Designation examples:

Bolt 2 M20x2.6x70.48.S.037 GOST

Bolt M20.6dh70.48 GOST

Screw M12x1.25.8dx40.88.35x.019 GOST

Screw M12.8dh40.43 GOST

Nut M20x2.6N.2x13.037 GOST

Nut M20.6N.5 GOST

Methods for locking threaded connections.

There are a large number of ways to lock or protect against self-unscrewing.

They boil down to the following:

1. Increased friction in the thread or at the end of the nut (lock nuts, spring washers).

2. Rigid connection of the nut with the screw shaft (castle nuts or use of wire)

Profile thread is established by GOST 9150-81 and is a triangle with an apex angle of 60 degrees.

This is the main type of fastening thread. Designed for connecting parts directly to each other or using standard products with metric threads - bolts, screws, studs, nuts.

Its main elements and parameters are specified in millimeters (GOST 24705-81).

According to GOST 8724-81, metric threads are made with large and fine pitches on surfaces with a diameter of 1 to 68 mm; above 68 mm, the thread has only a fine pitch, and the fine pitch of the thread can be different for the same diameter, and the large one has only one meaning. The large pitch is not indicated in the thread symbol. So, for a thread with a diameter of 10 mm, the large thread pitch is 1.5 mm, fine- 1.25; 1; 0.75; 0.5 mm.

M18-6g metric external thread, nominal diameter 18 mm, coarse pitch, thread tolerance range 6g;

M18x0.5-6g the same, fine pitch R=0,5;

M18LH-6g the same, but left;

M18-6N metric internal thread, nominal diameter 18 mm, coarse pitch, thread tolerance range 6N.

Inch thread

Currently, there is no standard that regulates the main dimensions of inch threads. The previously existing OST NKTP 1260 has been canceled, and the use of inch threads in new designs is not allowed.

Triangular profile thread with an apex angle of 55°.

Thread pipe cylindrical

In accordance with GOST 6311-81, cylindrical pipe threads have an inch thread profile, i.e. isosceles triangle with an apex angle of 55°.

Threads are standardized for diameters from 1/16" to 6" in number of pitches z from 28 to 11. The nominal thread size is conventionally related to the internal diameter of the pipe (to the nominal diameter). Thus, a thread with a nominal diameter of 1 mm has a nominal diameter of 25 mm and an outer diameter of 33.249 mm.

Examples of symbols:

G1 1/2 -A cylindrical pipe thread, 1 1/2 nominal bore in inches, accuracy class A;

G1 1/2 LH-B-40 the same, but left, accuracy class B, make-up length 40 mm.

Thread persistent

Trapezoidal thread

Thread with a profile in the form of an equilateral trapezoid with an angle of 30°. Used to transmit reciprocating motion or rotation in heavily loaded moving threaded connections. Often used in the manufacture of lead screws, according to GOST 24738-81 it is performed on surfaces with a diameter of 8 to 640 mm.

Trapezoidal thread can be single-pass(GOST 24738-81, GOST 24737-81) and multi-pass(GOST 24739-81). GOST 9484-81 establishes a trapezoidal thread profile.

Tr40 X 6 -trapezoidal single-start thread with an outer diameter of 40 mm, pitch 6 mm.

Thread persistent

R thread with a profile in the form of an unequal trapezoid with a working side angle of 3° and a non-working side-30 o. Thrust thread, like trapezoidal, May be single-pass And multi-pass. Performed on surfaces with a diameter from 10 to 640 mm (GOST 10177-82). It is used to transmit large forces acting in one direction: in jacks, presses, etc.

Example of a symbol:

S80х 10 -persistent single-start thread with an outer diameter of 80 mm, pitch 10 mm;

S80х 20(P10)-persistent multi-start thread with an outer diameter of 80 mm, a stroke of 20 mm, a pitch of 10 mm.

Rectangular thread (square)

Round thread

Threads with a round profile (GOST 6242-83) have a relatively long service life and increased resistance under significant loads. It is used in the manufacture of frequently screwed connections (spindles, valves, etc.) operating in a polluted environment, as well as thin-walled parts with rolled or stamped threads (electric lamp base, etc.).

Example of a symbol:

Rd16-round thread with outer diameter 16 mm.

If round threads are used in connections of sanitary fittings, then its designation will be as follows: Kr12x2.54 (GOST 13536-68).

Each nation has its own culture, way of life, traditions. But everyone has one thing in common - the desire for beauty. And if the ancient man, when arranging his home, had the only goal - to hide from bad weather and wild animals, then with the transition to settled life, priorities change: the development of science and culture leads to the arrangement of life, the home is decorated. The development of crafts in a particular area depends on the availability of materials and minerals. Thus, in the area of ​​the northern seas, where the main industries are fishing and hunting, walrus ivory carving originated. In mountainous regions with large reserves of ore, blacksmithing develops. Forested regions are rich in timber. It has long been used for housing construction and home improvement. After completing field work, peasants engage in wood carving to while away the long winter evenings. Over time, an exciting hobby turns into a main craft. Many achieve unprecedented mastery in this. The products of masters have the right to compete with the works of famous artists. And why compare? With the help of simple tools and imagination, the hands of a craftsman create extraordinary and rare masterpieces from the most ordinary wood. Artistic wood carving is a truly unique phenomenon.

Wood carving: main types

Over time, this type of applied art not only did not lose its popularity, but on the contrary, it developed. Depending on the type of materials used and the method of processing, new types of wood carving are distinguished: relief, flat-relief, sculpture, flat-notched and sawn. The main difference is the location of the pattern in relation to the surface or background of the work. Each of these types has its own methods of implementation, tasks and final result. Let's look at each of them in more detail.

Saw thread

This is one of the carving methods when the background is completely removed from the canvas. It also has other names: slotted or through wood carving.
This term accurately describes the process of wood processing. Geometric carving and relief are perfectly combined here. This is one of the oldest techniques; it requires a certain skill and dexterity, such as openwork through carving. The technique here is as follows: the workpiece is secured, outlined, the main design is applied and holes for the saw are drilled. The contour is followed by filing and subsequent preparation of the material for work: chamfering with a chisel and sanding the workpiece with sandpaper. The effect of airiness, lightness, weightlessness is created. The work is so delicate and elegant that it is sometimes difficult to believe that wood was used.

Flat relief carving

All types of wood carvings differ in their relationship to the background: it is either absent, or located in the same plane with the design, or recessed a few millimeters inward. The background is the surface of the products, which is decorated with geometric shapes or floral patterns. In this case, it is removed around the surface of the design and cut 5-7 millimeters deep into the canvas. The work is carried out in such a way that the background and the drawing are both in the same plane, but at the same time they look three-dimensional, and in different ones: the drawing is raised above the background due to the indentations along its contour, but at the same time all the details are at the same height. This style usually depicts figures of people, animals and birds, and elements of the plant world. It all depends on the master’s idea and execution technique. Most often, flat-relief carving is used in architecture and applied arts.

Relief carving

All types of wood carving require a certain skill and skill. You need to start with the simplest patterns. In order to correctly understand the essence of each element, it is better for a beginner to reproduce new and more complex details from plasticine, and then start processing wood. This also applies to relief carvings.
It is rightfully considered the most picturesque. This is a design carved into wood, processed over the entire surface and convex relative to the background. Images of flora and fauna, monograms, various symbols, and geometric shapes can be used as an idea. The quality of the finished product directly depends on the choice of wood. In this case, birch, oak, and beech are good to use. Their wood makes it possible to clearly work out each element down to the smallest detail and clearly highlight the contours. In this case, the background is cut off in order to reduce all the details of the ornament in relation to the main design at all identical points of its parts. Then, in lower areas, the ornament is restored. Then the background is selected and polished. This is a fairly labor-intensive technique. Therefore, it requires patience and some experience.

Sculptural carving

When considering the main types of wood carving, one cannot ignore sculptural carving.
This method of wood processing allows you to create three-dimensional images without a background - sculptures that can be viewed from all sides. The technique is used mainly in the process of making souvenirs, toys, household items, and for interior decoration.

Flat thread

A distinctive feature of this type of wood processing is the application of ornaments to a flat surface. Depending on the nature of the pattern, it can be flat-relief carving, that is, the pattern is displayed in the form of recesses, recesses, and flat-relief, when the ornament protrudes above the surface. Each of these types is divided into several subtypes, among which there is flat-notched geometric carving. This type is one of the simplest. It has long been used in the decoration of various household utensils with a flat surface: cutting boards, wooden dishes, furniture. The only tool used is a knife-jamb, and geometric shapes are used as a design: square, rhombus, triangle, circle, oval and their combinations. Interestingly, in ancient times geometric carving was not used as a simple decoration. Each element was symbolic and served as a talisman.

So, we looked at the main types of wood carving. Of course, this is the material of more than one article. And not even one book. The experience of masters has been passed on from generation to generation for many centuries. Something, unfortunately, has been lost, but something has been preserved, modified and developed into a new industry. And this is already a good sign. It once again proves that this type of decorative art continues to develop. And today it is no less popular than several centuries ago.

In mechanical engineering, two types of connections are used - detachable and permanent. The first type is obtained using rivets and bolts; this method is the most common. The second type is obtained by welding, soldering, and gluing parts. If the parts are fastened using the first method, special metal threads are used, which come in different types.

Metal carving

The thread profile of various materials is a section of a plane running along the axis of the workpiece. The main characteristics include:

1. The outer diameter is the dimensions of the tops of the cylinder, as well as the depressions of the inner surfaces. For pipe threads, the diameter is designated conventionally in inches.
2. The internal diameter is a thread parameter that indicates the dimensions of the cylinder to fit along the tops of internal threaded profiles, or along the recesses of external connections.
3. Pitch is the distance between the sides of two turns lying next to each other, which is measured along the axis of the part.
4. The profile angle is the value between the sides of the thread profile triangle, which is measured in the axial plane.
5. By continuing the sides of the profile, the height of the original triangle is obtained.

Purpose

Threaded profiles are external and internal. They are used for the following purposes:

• reliable fastening of the mechanism parts at the required distance;
• creating a hermetically sealed pipe connection;
• preventing part movement.

Types of thread

Cylindrical metal threads are classified by size, position on the surface, number of starts and area of ​​use. In production there are:

• metric;
• inch (symbol of sizes in inches);
• metric conical;
• round;
• trapezoidal;
• persistent.

These types are used in industry to connect parts of various types.

Metric

This type of threaded profile is used for fastening connections. As a result of compliance with technical conditions, it can be used as a chassis. In cross-section, the thread has the form of a triangle with equal sides, the angle of the apex of which is 55°. Manufactured with one or more passes to increase the strength of the connection of parts.

In industry, threads are distinguished with sizes from 0.25 mm to 600 mm, with a pitch of 0.25 mm to 6 mm, right and left versions. Fine pitch is used for thin-walled surfaces. The product marking contains the letter M, size, pitch, and also adds the number of passes and type of execution.

Metric thread

Inch

This type of thread is used to connect pipes and shut-off valves. Apply to metal surfaces and plastic. Dimensions are indicated in inches; in cross-section it looks like a triangle with equal sides and an apex angle of 55°. The valleys and peaks are removed to prevent rubbing of the metal. The size range starts from 3/16 to 4 inches.

Metric conical

This threaded profile is applied to a conical workpiece along the internal or external surface. According to technical specifications, the taper angle is 1:16. Used in pipe fastenings to create increased tightness. In the drawings, metric tapered threads are marked MK, then the size and pitch values ​​are indicated.

Round

Round threads are used in pipe fasteners, when connecting taps, joints and branches. The documentation is marked Kr, followed by the nominal dimensional values. A rounded profile with an angle of 30° is produced at the base and at the tops.

Trapezoidal

Threads of this type are considered popular. It differs from analogues in the property of independent braking. This characteristic is achieved by the rotational movement of the nut along the shaft, which results in increased friction. Does not require the use of additional elements to secure parts.

Trapezoidal threads are used to convert rotation into translational trapezoidal threads. Used in automotive equipment, industrial equipment, machine tools, robotics. The movement of the part on the shaft is smooth without jerking. Nominal sizes from 8 mm to 640 mm, with pitches from 1.5 mm to 12 mm. The diagrams are marked with Tr, and then the main parameters are indicated.

Persistent

This type of threaded profile is used for equipment on the shafts of which there is an increased axial load. In cross-section, it is a trapezoid with the working side located at an angle of 3°, and the other at an angle of 30°. Denoted by the Latin letter S.

Thrust thread

Advantages and disadvantages of threaded connections

The operational advantages of a threaded connection include:

1. Control of force when producing a thread profile on a workpiece.
2. As a result of effective self-braking, fixation occurs in the required position.
3. Easy to assemble and disassemble using available tools.
4. Low manufacturing costs.
5. Types of connections.
6. Possibility of fastening large parts.

The downside of a threaded connection is the uneven load along the thread profile. This phenomenon can lead to premature failure of the first turn as a result of increased operating forces. Another disadvantage is the effect of self-unscrewing under the influence of vibrations.

Threading

Produced using several methods:

1. A chisel and a chisel comb. It is performed on a machine using the necessary cutters, thanks to which precise calibrated measuring devices are obtained. Rarely used due to low production speed.
2. Using a rolling die, as a result of rolling over the body of the part, a threaded surface is obtained. It is obtained by extruding onto a workpiece using rollers.
3. Milling a threaded connection is possible using special tools. The cutter cuts into the workpiece, gradually decreasing by the thread pitch.
4. Grinding equipment is used to produce joints for measuring equipment with high precision.

You can make an external fastener profile yourself in a garage, and you should perform the following manipulations:

1. Secure the workpiece in a vice; its diameter must correspond to the size of the external thread.
2. Pick up the die and secure it in the holder.
3. Using a file, remove the chamfer from the workpiece, then coat it with oil.
4. Carefully lower the die onto the part.
5. Slowly turn the tool and screw it to the mark of the required thread length.

For internal cutting, taps are used and the following manipulations are performed:

1. Using reference tables, determine the required drill diameter.
2. Secure the workpiece in a vice and drill a hole using an electric drill. In this case, the tool must be at a right angle. The recess must be made larger than the profile size, taking into account the taper taper.
3. Replacing the drill with a countersink, chamfer the surface of the hole.
4. The first run is performed with the first number tool, lubricating the working surface with oil.
5. Two turns of the tap are alternated with one in the opposite direction in order to prevent tool breakage and chip discharge.
6. Next, repeat the run of the second and third number taps. The numbers are indicated on the shank.

1. For external threads, remove the chamfer from the workpiece and install the die on it at a right angle, having previously lubricated it with oil.
2. If skewed, trim and continue threading.
3. Before cutting the internal thread, drill a hole while keeping the tool perpendicular. Remove the chamfer and apply oil.
4. To prevent tap breakage, it is not recommended to use reinforcement machines or equipment.
5. If a tool breaks, tools should be used to remove debris from the recess.

To obtain high-quality fastening, it is necessary to follow the recommendations and rules for thread cutting. Selecting a quality tool will make the task easier and speed up the process.

Parameters that determine the shape and dimensions of the thread profile (see Fig. 1):

• thread pitch R;
• theoretical profile height H - the height of a triangular profile with sharp corners, obtained by extending the sides of the profile until they intersect;
• working profile height h is the height at which the threads of the bolt (screw) and nut come into contact;
• profile angleα is the angle between the straight sides of the profile;
• profile angle- the angle between the lateral straight side and the perpendicular to the center line of the thread.

For threads with a symmetrical profile, the profile angle is equal to half the profile angle.

Metric thread (Fig. 2) is the main triangular fastening thread. Metric threads come in coarse and fine pitches. Coarse pitch metric threads are the most common because they have less impact on wear and manufacturing errors than fine pitch threads. Metric threads with fine pitches, compared to threads with coarse pitches with the same outer diameter, provide parts with greater strength (the depth of the thread grooves is smaller and the internal diameter of the thread is larger) and reliability against self-unscrewing (the thread pitch, and therefore the thread lead angle, is smaller ). Therefore, metric threads with fine pitches are used in the manufacture of thin-walled threaded parts that serve for regulation and are subject to dynamic loads.

Inch threads (Fig. 3), like metric threads, are triangular, fastening. It is used to replace threaded parts of old and imported machines imported from countries that use the inch system of measures (USA, England, etc.), and in some special cases.

Metric tapered thread

A metric tapered thread has a triangular profile, similar (in terms of the dimensions of the profile elements) to the profile of a metric thread according to GOST 25229-82 (ST SEV 307-76). It is used for conical threaded tight (tight) connections.

Round threads (Fig. 4) are used for screws that carry large dynamic loads, operating in a polluted environment with frequent unscrewing and screwing (car couplings, fire fittings), as well as in thin-walled products, such as, for example, on sockets and sockets of electric lamps, parts of gas masks, etc. Several types of round threads are standardized.

Trapezoidal thread (Fig. 5) - the main thread of the screw - nut and worm gears. It is convenient to manufacture, has lower friction losses compared to triangular threads, and is more durable than rectangular threads.

The thrust thread (Fig. 6) has an asymmetrical trapezoidal thread profile. Used for screws that bear large one-sided axial loads in presses, pressing devices of rolling mills, load hooks, etc.

Pipe cylindrical, pipe conical and conical inch

Pipe cylindrical (Fig. 7), pipe conical (Fig. 8) and conical inch (Fig. 9) threads are small triangular inch fastening and sealing threads. They are mainly used for connecting pipes and pipeline fittings. Tapered threads ensure tight connections between threaded parts without special seals.

Rectangular (and square) threads are made on screw-cutting lathes. This method does not allow for high accuracy, and therefore this thread is used relatively rarely and, accordingly, is not standardized.

Standard thread sizes are taken according to the relevant GOST depending on the outer diameter d thread.

Studies of thread strength show that the axial load is distributed unevenly between thread turns, which is explained not only by the impossibility of producing absolutely accurate threads, but also by an unfavorable combination of bolt and bolt deformations (the bolt is stretched and the nut is compressed). To simplify thread strength calculations, it is conventionally assumed that the axial load is distributed evenly between the thread turns. Thread strength calculations are usually carried out as a test.

From Fig. 1 it can be seen that if an axial force acts on the parts mating with threads (bolt and nut, etc.) F, then the threads of each part work for shearing, crushing and bending.

The thread of a fastener is calculated only for shear and crushing, since its calculation for bending according to the formulas for the strength of materials is very conditional.

With the same materials of the mating threaded parts, the thread strength calculation is carried out for the male part using the formulas:
for cutting

to crumple


where τ c is the calculated thread shear stress;
σ sm - calculated bearing stress between threads;
n is the number of thread turns that absorb the load;
k is the coefficient of thread completeness (see Fig. 1), showing the ratio of the height of the thread in the dangerous section to the thread pitch;
[τ c ] - permissible thread shear stress;
[σ sm ] - permissible stress on thread collapse.

Thread completeness coefficient for metric threads of bolts, screws and studs (see Fig. 1) k=0.75; nuts k=0.88; trapezoidal thread k=0.65.

If the female threaded part is made of a material that is less durable than the material of the part covered by the thread, then thread shear calculations should be performed for each of these parts. Shear strength condition of the female part

Since the thread strength of standard fasteners is guaranteed by GOST, the thread strength of these parts is not calculated for strength.