Reading mechanical engineering drawings. Designations and technical requirements. How to read a drawing - plumbing and tool work Correct reading of drawings

To obtain information about a part from a drawing, that is, to read its drawing, you must follow a certain procedure.

1. Read the title block of the drawing: find out the name and purpose of the part, the name of the material from which it is made, the scale of the images.
2. Establish what types, other images of parts are given in the drawing, which view is the main one.
3. Study views and other images in their mutual connection, find out the outlines of a detail, mutual arrangement and the shape of its parts. Having imagined the shape of each part of the part from the drawing, mentally combine them into a single holistic image.
4. Determine the dimensions of the part and the dimensions of its elements.

When reading a drawing of a part, you can formulate questions for yourself that give an idea about it: a) what is the name of the part; b) what material it is made of; c) on what scale the drawing is made; d) what types does the drawing contain; e) a combination of which geometric bodies the shape of the part is formed; f) what is its general shape; g) what are dimensions details and dimensions of its individual parts.

Let's look at an example. Figure 113 is a drawing of the part that you need to read. What information can we get about the part from this drawing? Using the sequence of reading the drawing just given, we can establish that the part is called a “plug” and is made of steel. Scale - 1: 1, i.e. the image is made in natural size.

Rice. 113

The drawing contains two views - the main view and the left view. There are no other images. Using views, we determine the shape of the part and its parts.

By comparing the views, it can be established that the shape of the part is formed by several surfaces of rotation - cylinders. One of them has a diameter of 50 mm and a height of 10 (35 - 25) mm. The axes of rotation of the cylinders coincide and are located parallel horizontal plane projections. The second cylinder has a diameter of 42 mm, a height of 20 (25 - 5) mm. Between these cylinders there is a part element - a groove, which has the shape of a cylinder with a diameter of 36 mm and a length of 5 mm. A cylinder with a diameter of 42 mm has a conical chamfer, its dimensions are 3x45°, i.e. the height of the chamfer is 3 mm, and it is made at an angle of 45°.

A recess is located along the axis of rotation of the surfaces that form the shape of the part. It has the shape of a hexagonal prism and is shown in the main view with dashed lines. The depth of the hole is 25 mm, and the distance between two parallel edges is 22 mm. On parts, this size is called the “turnkey” size; it determines the distance between the “jaws” of the key.

Overall dimensions of the part: 35 mm and 050 mm.

Thus, reading a drawing comes down to obtaining all the information about the subject available on the drawing. In this case, both graphic and text information must be taken into account. Only together do they give an unambiguous idea of ​​the shape of the object, its size, material, i.e., they evoke a spatial image of the object from its flat image made on paper or a chalkboard.

• In what order should the part drawing be read?

Task 21. Read the part drawing given in Figure 114.

Rice. 114

Questions about the drawing

1. What is the name of the part?
2. What material is it made of?
3. What is the scale of the images?
4. What types are shown in the drawing?
5. The combination of which geometric bodies forms the shape of the part?
6. Which part element is shown in the main view with dashed lines? What shape is it?
7. What element of the part is represented by a circle Ø50 mm? List all the dimensions of this element.
8. What are the overall dimensions of the part?

Task 22. Figure 115 shows a drawing of a technical detail.

Rice. 115

Tasks for the drawing

1. Read the drawing using the order discussed above.
2. On visible parts the surface of the part in one of the views is given projections of points. Without redrawing the images, find the projections of these points on another view.
3. Determine which of the given points (D, B, etc.) coincides with the vertex; which one lies on the edge, face or surface of rotation of the part.
4. IN workbook write down: the names and material from which the part is made; scale; number of images and their names; the number of geometric bodies that form the shape of the part and their names; overall dimensions of the part.

Read the drawings of the parts (Fig. 116, a and b).

Rice. 116

Make technical drawings of parts according to the drawing in rectangular projections (Fig. 117, a and b). I, 35

Getting to know the product. Using the main inscription, find out the name of the product, the scale of the image, etc.

Reading images. Determine what types, sections, sections are given in the drawing and what is the purpose of each image. Find out the position of the cutting planes with the help of which the cuts and sections are made, and if there are additional and local views, the directions of their projection.

Study of the components of the product. Find out their names using the specification, and find out their shape and relative position using the drawing. Study the component parts of the product in order of specification item numbers, and images of parts should first be found in the view on which the item number is indicated, and then on the others. Take into account that in the presence of cuts, the same inclination and frequency of the hatching lines of its sections contribute to identifying the shape of the part.

Study of product design. Find out the nature of the connection of individual parts to each other. For permanent connections (welded, riveted, soldered, etc.), determine each element and their connection points, and for detachable connections, identify all fasteners.

Determining the sequence of assembly and disassembly of the product. This is the final stage of reading the drawing.

Let's consider an example of reading an assembly drawing of a product shown in Fig. 14.4.

The assembly drawing shows an angular cable plug, as can be seen from the main inscription. It is one of two parts of a connector used to connect an electrical cable. The connection of one part of the connector - the plug - to the other part - the socket - occurs using pin 1 and nut 2.

The assembly drawing shows four images: a full section, part of the view on the left, section A-A and local view B.

The incision reveals internal structure product, the left view makes it possible to understand the shape of the nut 2 and the cup 3. Section A - A reveals the connection of the cup 3 and the body 5. Local view B shows part of the nut 7. View B is made in the direction indicated by the corresponding arrow.

According to the specification shown in Fig. 14.5, we determine that the product consists of one assembly unit (contact), nine parts and three standard screws.

Based on the images in the drawing, we determine the shape of the parts. The body is shown in three images: in the main section, in the left view and in section А-А. The external contours of the body are cylindrical in shape with a right angle bend. The internal shape is represented by two threaded and one smooth holes.

The outer contour of the glass 3 consists of three cylindrical surfaces and one conical surface with a through cylindrical hole. In this case, one cylindrical surface has two slots, shown in the view on the left.

Nut 7 has a slot (slot), shown in local view B, which is designed for screwing it into the threaded hole of the housing.

The nut 10 on the outer diameter of the cylindrical surface has a knurl, shown in part in a sectional view of this part.

Nut 2 has a cylindrical shape with an internal thread M16x 1. There are four through holes on its cylindrical surface.

The design of the product is as follows. The cable is inserted into the housing hole 5, soldered to contact 1 through another hole and closed with a plug 6. The cable is secured in the plug using a nut 7, a seal 8 and another nut 10. A contact / is inserted into the inner hole of the glass 3 and sealed with a sleeve 4. The glass 3 passes through the smooth hole of nut 2 and is secured in the housing using three M2 screws, shown in section A-A.

The product is disassembled in the following order: unscrew screws 11, remove cup 3, remove nut 2. Unscrew the plug and nuts from the threaded holes of the housing and remove the cable.

Every technically trained person is required to be able to read any well-drawn drawing.

Read the drawing- this means to clearly imagine the shape and dimensions of the parts depicted in this drawing, to understand the mutual connection of parts and assemblies in their interaction. Without this, it is impossible to detail the assembly drawing or assemble the machine based on it. When reading an assembly drawing, you must become familiar with the design, purpose and operation of the machine; figure it all out technical documentation cars, if available; familiarize yourself with all projections, additional or partial views, sections, sections, etc.; read the specification with the names of the parts and find them on the drawing, starting with the first number, and understand their shape, purpose, interconnection, etc.

For example, consider the assembly drawing of a flange bearing (Fig. 470), which serves as a support for a shaft operating at low speed. The bearing consists of a housing 7 and a bushing 2, connected to it by a set screw 3. The mating surfaces of the shaft and bushing are cleanly machined and lubricated during operation using a grease gun 4.

The bearing is drawn in three projections with sections. The main view is made without a cut. The plan shows a horizontal section, and the side view shows a full section.

The bearing housing, which has a cylindrical hole in the middle for the trunnion, goes into an oval flange on which there are two cylindrical bosses with holes for bolting. On top of the body there is a boss with a hole for the thread of the oil can and an outlet to the lubrication groove. The inner and outer surfaces of the bushing are cylindrical. There is a hole and an lubrication groove at the top of the bushing. The set screw prevents the bushing from turning in the housing. Oil can with auxiliary meaning, drawn with thin lines. Such an image of parts is allowed (see GOST 3456-46),

In fig. 471 shows a plunger pump, which is a more complex structure.

The pump consists of a housing 1 with two connecting flanges, an air cap 8, a plunger 12 and two valves - suction 3 and discharge 6.

The pump plunger moves back and forth. When the plunger extends, a vacuum is created in the resulting space and water rushes into the housing through the inlet? 25.

Inlet valve 3 will open under water pressure, but outlet valve 6 remains closed. Water will fill the freed space, and valve 3 will close under the action of spring 4. When the plunger moves back, water pressure will open valve 6, and water will rush into the discharge hole. The direction of movement of injected water is shown by an arrow. After the plunger pushes some of the water out of the cavity, valve 6 closes under the action of the spring, and valve 3 opens. Then the process is repeated. The uniformity of water supply is ensured by the air cap 8, in which some air always remains, the elastic compression of which smoothes out the pulsations created by the movement of the plunger. To prevent leakage, a gland seal is installed between the walls of the plunger and the housing, consisting of a packing 13, a gland ring 14 and a union nut 15. The pump plunger is connected to the connecting rod head of the crank mechanism using pin 18. The pump is connected to the receiving and discharge pipelines with studs 9 and 11. Movable valves 3 and 6 are shown in two extreme operating positions. Contour lines show the position of the valves during discharge, thin lines - during suction.

The pump is depicted in three projections with sections: full and partial. In addition, views have been added to clarify some design elements.

The drawing is equipped with a main inscription and a specification for the form

No. 3 (for drawings of products of main production).

Having familiarized ourselves with the description of the design of the pump and the principle of its operation, we will consider the procedure for reading the drawing on one of its most complex parts - the housing.

To imagine the shape of any part indicated on the assembly drawing, you need to find it in all projections and visually walk around all the elements belonging to it along the outer contour. Let's set the starting point N on the main view and the direction of the traversal counterclockwise. We move along the contour in the direction indicated by the arrow to point A. Using the horizontal projection, we are convinced that the oval part protruding to the right belongs to the same part. The correctness of this is confirmed by the shading of the material, which in all projections is made in the same direction; therefore, we make the further path from point A to point B around the oval part as shown in the drawing. At point B, a curve of radius 30 mm is formed by a frontal secant plane, the trace of which on the profile projection merges with the profile axis of the body. As you can see, the profile projection gives a more clear idea of ​​the shape. This projection shows that the cylindrical part of the body to the left of the profile axis goes from a diameter of 60 mm to a diameter of 64 mm, and then again goes to a diameter of 60 mm. Consequently, the outer outline in the main view will not be indicated by a curve of radius 30 mm, but by a curve of radius 32 mm. Therefore, the transition from point B to point C must be made as indicated in the drawing. Having gone around the cylindrical part of the body along a curve, we come further, bypassing the studs, to point C. Mentally considering that the cap is unscrewed, we move from point C to point E. To correctly exit from point E to point N, let’s turn to other projections. On the horizontal projection it can be seen that the protrusions represent four cylindrical tides and each of them has through hole? 18 mm. This is confirmed in the profile projection. Therefore, the path from point E must be made around the tides and thus arrive at the starting point N.

Visually walking around the contour of the body on the horizontal plane of projections does not present any difficulties. On the profile projection at point P at the intersection of the inclined straight line and the dash-dotted line, which, as we know, indicates in the drawings the parts that have fallen off after the cut (superimposed projections), we go around the tide, which is also depicted on the horizontal plane of the projections.

The inclined straight line represents a stiffening rib with a thickness of 18 mm, which can be seen in the horizontal projection. Therefore, the boss and the edge belong to the same part.

The transition from point P to R is similar to the transition from point C to E. The curve behind point L refers to the outline of the stiffener, which is indicated by dashed lines on the horizontal projection under the cylindrical part of the body. Therefore, this rib also belongs to the body. The rib on the profile projection is not shaded, although the plane of the cut passed through it, since the ribs are not cut along. The further path from point L to point P is clear from the drawing.

From the above it follows that in order to understand the outlines of any part from an assembly drawing, it is necessary to find an image of it in all projections, and in difficult cases resort to comparing these images, using additional sections, extension sections and other auxiliary images .

It should also be recalled that the shading of sections of parts is one of the signs by which one can judge the boundary separating one part from another, since parts in contact with each other are shaded differently in sections.

The skills of reading drawings fluently are acquired through the process of systematically and persistently performing exercises, analyzing detailed and assembly drawings in order of increasing complexity, as well as by studying the standards “Drawings in Mechanical Engineering”.

Normal 0 false false false RU X-NONE X-NONE

further, bypassing the studs, to point C. Mentally considering that the cap is unscrewed, we move from point C to pointE. To correctly exit from the pointEto the pointN, Let's turn to other projections. The horizontal projection shows that the protrusions are four cylindrical bosses and each of them has a through hole? 18 mm.This is confirmed in the profile projection. Therefore, the path from the pointEneed to travel around the tides and thus arrive at the starting pointN.

Visually walking around the contour of the body on the horizontal plane of projections does not present any difficulties. On the profile projection at the pointPAt the intersection of the inclined straight line and the dash-dotted line, which, as we know, indicates in the drawings the parts that have fallen off after the cut (superimposed projections), we go around the tide, which is also depicted on the horizontal plane of the projections.

The inclined straight line represents a stiffening rib with a thickness of 18mm,as can be seen in the horizontal projection. Therefore, the boss and the edge belong to the same part.

Transition from pointPToRsimilar to the transition from a pointFrom toE. Curve by pointLrefers to the outline of the stiffener, which is indicated by dashed lines on the horizontal projection under the cylindrical part of the body. Therefore, this rib also belongs to the body. The rib on the profile projection is not shaded, although the plane of the cut passed through it, since the ribs are not cut along. Further path from the pointLto the pointPis clear from the drawing.

From the above it follows that in order to understand the outlines of any part from an assembly drawing, it is necessary to find an image of it in all projections, and in difficult cases resort to comparing these images, using additional sections, extension sections and other auxiliary images .

It should also be recalled that the shading of sections of parts is one of the signs by which one can judge the boundary separating one part from another, since parts in contact with each other are shaded differently in sections.

The skills of reading drawings fluently are acquired through the process of systematically and persistently performing exercises, analyzing detailed and assembly drawings in order of increasing complexity, as well as by studying the standards “Drawings in Mechanical Engineering”.

Instructions

When reading a drawing, look at the frame in which it is framed. In the main frame, find information about the name of the part or assembly unit, its number and the material from which it is made (if it is a part). In the case of an image of an assembly unit, you will see in the “Name” column of the main inscription a line in which there will be “Assembly drawing”.

Pay attention to the scale of the image, which should be indicated in the title block of the drawing. It shows how many times the image in the drawing is reduced or enlarged relative to the real object. When designing, magnification scales are used (for example, 2:1, 4:1), which means that the image in the drawing is enlarged compared to the real object. The reduction scale (for example, 1:2, 1:10), in turn, shows how much the image in the drawing is reduced compared to the object.

Find the main view of the depicted object. Most likely, the number of sizes (including overall dimensions) will be printed on it. Take a close look at this view. Pay attention to the cuts and sections, if any, as they give an idea of internal form details. The area of ​​the part or assembly that falls within the plane of the cut or section is shown as shaded in the drawings. Some cuts and sections are presented separately, and they are designated in capital letters with a hyphen (for example, A-A, B-B).

For a more accurate representation of the object, use other views shown in the drawing. Most likely it will be a left view and a top view. Additional views are indicated by capital letters (for example, D or G).

Please pay attention to the dimensions provided. They are usually indicated with tolerances that characterize the accuracy of manufacturing a part or assembly unit. The drawing of the part must also include surface roughness symbols.

Read technical requirements. This is the text located above the main title of the drawing. It carries information about the manufacture, storage and operation of the object.

Technological documentation includes route and operational maps. When reading the route map, pay attention to General requirements, presented to a part or assembly. Next you will see the sequence of operations that are necessary to manufacture a particular object. The numbers before the name of the operation characterize the number of the workshop, workplace and the number of the operation itself. Then the sequence of actions is listed, and at the end of the operation the tools and devices used are indicated.