Conventional image designation of thread. Thread designation

The threads on the rods are depicted along the outer diameter with solid main lines, and along the inner diameter with solid thin lines.

You studied the basic elements of metric threads (outer and inner diameters, thread pitch, thread length and angle) in fifth grade. Some of these elements are indicated in the figure, but such inscriptions are not made on the drawings.

Threads in holes are depicted with solid main lines along the internal diameter of the thread and solid thin lines along the outer diameter.

The thread symbol is shown in the figure. It should be read like this: metric thread (M) with an outer diameter of 20 mm, third class of accuracy, right-handed, with a large pitch - “Thread M20 class. 3".

In the figure, the thread designation is “M25X1.5 class.” 3 left” should be read as follows: metric thread, outer thread diameter 25 mm, pitch 1.5 mm, fine, third class of accuracy, left.

Questions

1. What lines represent the threads on the rod?
2. What lines show threads in a hole?
3. How are threads indicated on drawings?
4. Read the entries “M10X1 class. 3" and "M14X1.5 cl. 3 left."

Working drawing

Each product - a machine or mechanism - consists of separate, interconnected parts.

Parts are usually made by casting, forging, and stamping. In most cases, such parts are subjected to machining on metal-cutting machines - lathes, drilling, milling and others.

Drawings of parts, provided with all instructions for manufacturing and control, are called working drawings.

The working drawings indicate the shape and dimensions of the part, the material from which it must be made. The drawings indicate the cleanliness of surface treatment and the requirements for manufacturing accuracy - tolerances. Manufacturing methods and technical requirements the finished part is indicated by an inscription on the drawing.

Cleanliness of surface treatment. On treated surfaces there are always traces of processing and unevenness. These irregularities, or, as they say, surface roughness, depend on the tool used to process.

For example, a surface processed with a garnish will be rougher (uneven) than after processing with a personal file. The nature of roughness also depends on the properties of the material of the product, on the cutting speed and feed rate when processing on metal-cutting machines.

To assess the quality of processing, 14 classes of surface cleanliness have been established. Classes are designated in the drawings by one equilateral triangle (∆), next to which the class number is indicated (for example, ∆ 5).

Methods for obtaining surfaces of different cleanliness and their designation in the drawings. The cleanliness of processing one part is not the same everywhere; therefore, the drawing indicates where and what kind of processing is required.

The sign at the top of the drawing indicates that for rough surfaces there are no requirements for cleanliness of processing. The sign ∆ 3 in the upper right corner of the drawing, taken in brackets, is placed if the same requirements are imposed on the surface treatment of the part. This is a surface with traces of processing with bastard files, roughing cutters, and an abrasive wheel.

Marks ∆ 4 - ∆ 6 - semi-clean surface, with barely noticeable traces of processing with a finishing cutter, personal file, grinding wheel, fine sandpaper.

Marks ∆ 7 - ∆ 9 - clean surface, without visible traces of processing. This treatment is achieved by grinding, filing with a velvet file, or scraping.

Mark ∆ 10 - a very clean surface, achieved by fine grinding, finishing on whetstones, filing with a velvet file with oil and chalk.

Signs ∆ 11 - ∆ 14 - surface cleanliness classes, achieved by special treatments.

Manufacturing methods and technical requirements for the finished part are indicated in the drawings by the inscription (for example, blunt sharp edges, harden, burnish, drill a hole together with another part and other requirements for the product).

Questions

1. What symbols indicate the cleanliness of the surface treatment?
2. After what type of treatment can a surface finish of ∆ 6 be obtained?

Exercise

Read the drawing in the figure and answer the questions in writing using the form provided.

“Plumbing”, I.G. Spiridonov,
G.P. Bufetov, V.G. Kopelevich

A part is a part of a machine made from a single piece of material (for example, a bolt, nut, gear, lead screw lathe). A node is a connection of two or more parts. The product is assembled according to assembly drawings. A drawing of such a product, which includes several units, is called an assembly drawing; it consists of drawings of each part or unit and depicts assembly unit(drawing of a single...

The most widely used fasteners are those that have a threaded surface. Due to a certain combination of turns and depressions, a reliable fastening is ensured that can withstand high pressure. There is simply a huge number of different fasteners, all of them are characterized by certain performance characteristics.

The threaded surface can be classified according to a fairly large number various signs. The designations used make it possible to determine the main parameters, thereby simplifying the selection of suitable fasteners. Depending on the surface being processed, external and internal threads are distinguished. Internal and external threads have the same characteristics. In addition, the following types of connections are distinguished:

1. Metric.
2. Metric conical type.
3. Pipe cylindrical type.
4. Conical pipes.
5. Double conical.
6. Thrust thread.
7. Round.
8. Trapezoidal.

The turns can be left or right. The spread of the left-hand thread is quite large; it is used for fastening ordinary and critical parts.

Thread profiles and parameters

The most widespread is the metric profile. To regulate the main parameters, GOST 9150-81 was adopted, which was then replaced by GOST 9150-2002. Among the features of such a surface, the following points can be noted:

1. The coils resemble an equilateral triangle, the profile angle is 60 degrees. The outer turns have a slightly different angle of bluntness of the turns and depressions. The main parameters are the nominal diameter and pitch of the turns.
2. Options with fine pitch are used when it is necessary to ensure high tightness of the resulting connection.
3. When designating, the letter “M” is used, after which the diameter is indicated. Tolerances and other information are displayed on the drawing only when it is used to obtain high-precision and high-quality products.

The inch type of fasteners has become less widespread. Today in the CIS there are practically no standards regulating the basic parameters of such a surface. Inch versions are usually used when carrying out repairs. The peculiarity of this version is that the main dimensions are expressed in inches.

Download GOST 9150-2002

Cylindrical pipe threads are characterized by a profile that is characteristic of metric threads. The surface is formed by triangles with equal sides and an apex angle of 55 degrees. GOST 6367-81 was adopted as standards. It is used for connecting pipes and thin-walled cylindrical products. For the conical one, our own GOST 6211-81 was developed; the profile in this case corresponds to the inch profile. Pipe versions are extremely common today. The process of cutting them was significantly simplified due to the advent of special tools and equipment.

There is a fastening element in the form of a trapezoid. In this case, the profile resembles an isosceles trapezoid, the angle between the individual sides is 30 degrees. A similar form is used if the workpiece has a diameter from 10 to 640 mm. Designations and many other points are indicated in GOST 9481-81. Application area: rotation transmission.

The thrust is standardized by GOST 24737-81. The shape in this case resembles an unequal trapezoid, one of the sides tilts at an angle of 3 degrees. Scope of application – transmission of unilateral force that exerts an impact in the axial direction

Each fastening element is characterized by its own specific features, on which their purpose depends.

In the regulatory documentation you can find all the common designations and dimensions required to determine the dimensions and other qualities of the threaded surface.

Purpose of thread and its elements

The purpose of the fastening element in question is to connect and fix individual elements. The products in question may be designed to transmit rotation or some force. The main elements can be called:

1. The profile is considered in the section that is formed when passing through the axis. In other words, the axis created cuts the product along the floors, resulting in a specific shape being displayed. Based on the resulting image, some other most important parameters can be determined.
2. A turn is the part of the surface that is formed during a full revolution. In some cases, the number of turns of the working part is indicated. This indicator can be determined by dividing the length of the working part by the step indicator.
3. The profile angle is formed between the sides. In some cases, this parameter is indicated on the drawings. To indicate the angle, a plane passing through the axis of the product is used.
4. The thread pitch is considered the most important parameter, which is indicated in technical documentation and on the drawings. A similar parameter determines the distance between parallel points of two adjacent depressions. In metric, the specified distance is indicated in millimeters.
5. The profile height is also considered an important parameter. It is taken into account when designing various products. Profile height is the distance that is formed between the top of the turns and the base. As this parameter increases, the strength of the resulting connection increases significantly, but the make-up process becomes more complicated.
6. Outer, middle and inner diameter. On drawings and in other technical documentation, as a rule, the outer diameter is indicated - the diametrical dimension that describes the surrounding threaded surface. Other indicators are taken into account extremely rarely, but are also recorded in special tables.

Some of the above parameters are indicated in the drawing with special symbols, others can be found in special technical documentation. When cutting turns, information is given to the outer diameter and pitch of their location.

Image and designation of threads in the drawings

The threaded surface is represented by a complex shape, which is formed by the screw movement of a flat contour. This type of connection is used extremely often today. That is why certain standards were adopted for their designation in the drawing. To simplify the task of creating project documentation a complex profile is designated conventionally. The thread designation can be characterized as follows:

1. Often, when displaying a section, a thin line is used that extends slightly into the hatching. To indicate such a connection, the type of connection is indicated on the extension dimension lines (for example, “M” indicates metric). The next number shows the diametrical size.
2. In some cases it is used symbol thread associated with the profile display. A similar leader is required to indicate the angle between individual turns.
3. When creating critical and high-precision products, dimensional tolerances are specified. As a rule, this is done by displaying an extension flange or regular dimension lines.
4. The roughness of the resulting surface is also important when creating high-quality and responsible fasteners.

Schematic designation tapered thread practically no different from metric. In some cases, the turns are depicted in their original form. However, it is quite difficult to depict it, so the symbol is most often used.

Mounting threads

The most widespread are fasteners. Their purpose is to screw together and secure individual parts. Among the features we note the following points:

1. The coils must be designed for high force. To do this, the pitch is reduced or the profile height is increased.
2. If the resulting product must have high tightness, then attention is paid to the shape of the tops of the turns and depressions. They must fit perfectly together.
3. Attention is paid to the hardness of the material used during manufacturing, since when exposed to an axial load, the working part is often cut off.

Fastening elements of this type are characterized by reliability and practicality in use.

Running threads

In some cases, the purpose of the surface in question is not to fasten parts, but to ensure smooth movement within a certain range. The features of such products include the following points:

1. The profile has a shape that ensures a smooth ride. To do this, a surface with the fewest corners is created.
2. As a rule, working part long, there are travel stops at the beginning and end.
3. The material used to create the workpiece must have high wear resistance.

Such products are extremely rare today, since their reliability and service life are relatively low.

Dimensions according to GOST 6211-81

The GOST in question is used to designate tapered pipe threads. The table displays the following information:

1. Diameter in the main plane.
2. Working part length.

Download GOST 6211-81

Threads are made with a cutting tool, removing a layer of material, rolling - by extruding screw protrusions, casting, pressing, stamping, depending on the material (metal, plastic, glass) and other conditions.

Due to the design of the thread-cutting tool (for example, a tap, Fig. 8.14; dies, Fig. 8.15) or when retracting the cutter, when moving from a section of the surface with a full-profile thread (sections l) to a smooth one, a section is formed where the thread seems to move to no (sections l1), a thread run-out is formed (Fig. 8.16). If the thread is made to a certain surface that does not allow the tool to be brought all the way to it, then an under-thread is formed (Fig. 8.16.6, c). The run-out plus the undercut forms an undercut of the thread. If you need to make a full profile thread, without a run, then to remove the thread-forming tool, make a groove, the diameter of which for external threads should be slightly less than the internal diameter of the thread (Fig. 8.16, d), and for internal threads - slightly larger than the outer diameter of the thread (Fig. . 8.17).At the beginning of the thread, a conical chamfer is usually made, which protects the outer turns from damage and serves as a guide when connecting parts to the thread (see Fig. 8.16). The chamfer is performed before cutting the thread. The dimensions of chamfers, runs, undercuts and grooves are standardized, see GOST 10549-80* and 27148-86 (ST SEV 214-86). Fastening products. Thread exit. Runaways, undercuts and grooves. Dimensions.

Constructing an accurate image of thread turns takes a lot of time, so it is used in rare cases. According to GOST 2.311 - 68 * (ST SEV 284-76), in the drawings the thread is depicted conditionally, regardless of the thread profile: on the rod - with solid main lines along the outer diameter of the thread and solid thin lines - along the inner diameter, along the entire length of the thread, including the chamfer ( Fig. 8.18, a). In the images obtained by projection onto a plane perpendicular to the axis of the rod, an arc is drawn along the internal diameter of the thread as a continuous thin line, equal to 3/4 of the circle and open anywhere. In the images of the thread in the hole, solid main and solid thin lines seem to change places (Fig. 8.18.6).

A solid thin line is applied at a distance of at least 0.8 mm from the main line (Fig. 8.18), but not more than the thread pitch. Hatching in sections is brought to the line of the outer diameter of the thread on the rod (Fig. 8.18, d) and to the line of the internal diameter in the hole (Fig. 8.18.6). Chamfers on a threaded rod and in a threaded hole that do not have a special structural purpose are not shown in projection onto a plane perpendicular to the axis of the rod or hole (Fig. 8.18). The thread boundary on the rod and in the hole is drawn at the end of the full thread profile (before the start of the run) with the main line (or dashed if the thread is depicted as invisible, Fig. 8.19), bringing it to the lines of the outer diameter of the thread. If necessary, the thread run is depicted with thin lines , carried out at approximately an angle of 30° to the axis (Fig. 8.18, a, b).

A thread shown as invisible is depicted with dashed lines of the same thickness along the outer and inner diameters (Fig. 8.19). The length of the thread is the length of the section of the part on which the thread is formed, including the run-out and chamfer. Usually, the drawings indicate only the length l of the thread with a full profile (Fig. 8.20, a). If there is a groove, external (see Fig. 8.16, d) or internal (see Fig. 8.17), then its width is also included in the length of the thread. If it is necessary to indicate the run or length of the thread with a run, the dimensions are applied as shown in Fig. 8.20, b, c. The undercut of the thread, made all the way, is depicted as shown in Fig. 8.21, a, b. Options “c” and “d” are acceptable.

On drawings in which threads are not made (on assembly drawings), the end of a blind hole can be drawn as shown in Fig. 8.22 On sections of a threaded connection in the image on a plane parallel to its axis, only that part of the thread that is not covered by the thread of the rod is shown in the hole (Fig. 8.23).

There are threads: general purpose and special ones intended for use on products certain types; fasteners, intended, as a rule, for a fixed detachable connection components products, and running gear - to transmit movement. Right-hand threads are predominantly used; LH is added to the designation of left-hand threads. In the designation of multi-start threads, the stroke is indicated, and in brackets - the pitch and its value

In accordance with GOST 2.311-68, the thread in the drawing is depicted conditionally. Moreover, the image of the external thread (on the rod) differs from the image of the internal thread (in the hole).

The thread on the rod along the outer diameter is depicted by the main solid line, and along the inner diameter - by a solid thin line. The thread in the hole along the inner diameter is depicted as a main solid line, and along the outer diameter as a solid thin line (Fig. 7). The distance between the main solid line and the thin solid line should be approximately equal to the thread pitch, but not less than 0.8 mm.

In images obtained by projecting the helical surface of a thread onto a plane perpendicular to its axis, a solid thin line is drawn with an arc 3/4 of the length of the circle, open at any point.

When making cuts, hatch lines are drawn to the main solid line.

The visible thread boundary is drawn as a solid base line at the end of the full thread profile to the line of the outer diameter of the thread. If necessary, the thread run-out is depicted as a solid thin line, as shown in Fig. 7a, b.

1.4. Designation of threads in the drawings: metric thread

The designation of a metric cylindrical thread includes: type of thread (letter), outer diameter of the thread, number of starts, thread pitch, thread direction, for example:
- metric thread with an outer diameter of 20 mm, two-start, with a pitch of 1.5 mm, left.

In the case of a right-hand thread, nothing is added at the end of the designation, for example:
- metric thread with an outer diameter of 20 mm, two-start, with a pitch of 1.5 mm, right.

In the case of a single-start thread, the number of starts is not indicated in the designation, for example:
.

Each outer diameter of a metric thread corresponds to several pitches. One of them, the largest, is called a large step. If the thread has a large pitch, then the pitch is not indicated in the thread designation, for example:
.

The designation of a metric cylindrical thread in the drawing is indicated as shown in Fig. 8a.

The designation of metric tapered threads includes: type of thread (letters
), nominal thread diameter, thread pitch, thread direction, for example:
.

The nominal diameter of a tapered thread is taken to be the diameter of the thread in the main plane (Fig. 9). The main plane of a tapered thread is the plane perpendicular to the thread axis, in which the nominal dimensions of the thread diameters are specified.

The plane perpendicular to the thread axis and used to determine the axial position of the main plane of the tapered thread is called base plane of tapered thread. As a rule, the base plane is taken to be the end surface limiting the conical thread: on the side of the smaller base of the cone - for external threads, on the side of the larger base - for internal threads.

The designation of a metric tapered thread in the drawing is indicated as shown in Fig. 8th century

Pipe thread

The designation of pipe threads includes: type of thread (letter for cylindrical pipe threads; letter
for external pipe conical threads; letters for internal pipe threads) and thread size designation, for example:
;
, Where 1, 1/4 – diameters of the nominal diameter of the pipe on which the thread is cut, in inches.

The designation of pipe threads in the drawing is indicated as shown in Fig. 8 g, d.