Reading drawings and symbols. Reading an assembly drawing. Reading order - Technical drawing How to read part drawings correctly

TO category:

Metalwork and tool work

Each working drawing must answer next questions: what part and in what scale is depicted on it, what material is it made of, what are its shape, dimensions as a whole and the dimensions of its individual elements, what deviations from the given dimensions can be allowed, what deviations are allowed in the shape and location of its most important surfaces, with what cleanliness should individual surfaces of the part be processed, etc.

To answer all these questions means reading the drawing. Let's try to get similar answers by referring to Fig. 1. To do this, let's start studying the drawing by reading the stamp of the main inscription, which is always located in the lower right corner of the sheet. First of all, we establish that the drawing shows the body of the combined tool holder, presented in life size, since the stamp indicates a scale of 1:1. The body must be made of 40X steel.

Now let's imagine the shape of the part. To do this, consider the left top part drawing, where the main view of the holder body is drawn. This view should give the most complete picture of it. We establish that the holder consists of a thick part (head), a thin part (tail) and a connecting part. Paying attention to the extended section shown under the main view, we conclude that the tail part of the holder is cylindrical body a flat cut off from the side reading the drawing, as well as a circular chamfer on the right end of the cylinder.

Next you need to establish what the housing head is. From the main view, one can only get the idea that the head has a conical Morse hole No. 4, which then turns into a cylindrical hole with a diameter of 20 mm. It is difficult to judge the external shape of the head by the main appearance alone. To do this, you will obviously have to use the left view and the top view. Referring to the view on the left (in the upper right corner of the drawing), we establish that the head consists of a large cylinder, from which two rectangular protrusions extend to the right and two similar protrusions down. Down side one of the protrusions runs strictly along the central axis of the cylinder. Returning to the main view, we make sure that the protrusions are somewhat shorter than the head cylinder. From the main view and the top view we find two pairs of holes with Ml2 threads on the head. The view on the left clarifies that they are not made in all four, but only in two protrusions.

Rice. 1. Manufacturing drawing of the part.

The shape of the connecting part allows you to set the main view and top view. This part is a cylindrical body (see icon o for size 60C3), through which a through line passes perpendicular to its axis. foramen ovale for knocking out the tool.

So, as the shape of the tail, head and connecting part is studied, the reader of the drawing develops an idea of ​​​​the shape of the holder as a whole.

Now you need to determine the dimensions of the part shown in the drawing. By considering how the dimension lines (lines with arrows) are located and what numbers are in them, you can establish the Dimensions of the part and its individual elements, expressed in millimeter-pax. However, it is important to know not only the size, but also the location of the dimensions on the part. Please note that most of the dimensions are set from one, left end of the part (sizes 250, 135, 98, 88). The surface from which dimensions are set is called the reference base. By putting down the dimensions in this way, the designer thereby instructs the production workers to fulfill precisely these dimensions and maintain them precisely from this surface. These instructions from the designer should be strictly followed, since violation of the reference base during the manufacture of parts leads to deviations from the drawing dimensions and to defects. Therefore, you cannot calculate the dimensions not specified in the drawing yourself and use them in the manufacture of parts.

In addition to the numbers characterizing the dimensions of the part, some dimension lines contain digital and alphabetic symbols. These icons characterize the tolerances for inaccuracy in their implementation. We will get acquainted with the tolerances below. From the data in this drawing, one can also draw a conclusion about the permissible inaccuracy of the position of the surfaces, using already known notations.

From the instructions above the main inscription stamp it is clear that the tail part of the part must be hardened to the hardness indicated in the drawing, and before grinding it must be blued and marked according to the drawing.

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.

As you know, reading is a very exciting and useful activity, and experienced engineers and highly qualified workers knowledgeably claim that not only fiction, newspapers and magazines, but also drawings. They are flat two-dimensional images that reflect the geometric shape, which the parts manufactured from them must have.

In progress reading drawings an idea is formed about the object or device depicted on it, as well as about the principles of operation of components and assemblies.

In many assembly drawings, devices are depicted in such a way that, after studying them, it becomes completely clear to an engineer or worker what parts they consist of, how they relate to each other, and which ones. geometric parameters have.

Assembly drawings in production conditions are read directly at the workplace, already during the assembly process. Concerning design bureaus, then engineers there read them in order to develop various working documentation.

1) First you need to carefully read the information contained in the title block. It indicates the name of the part depicted, the scale, as well as the material of manufacture.

2) Then you need to determine the types of sections and sections, that is, what kind of images the part is represented in the drawing.

3) After this, you should mentally imagine the shape that the part has.

During reading drawings it is necessary to take into account the fact that all projections of parts on them are interconnected. It is accepted that the same sectional part in all its images is hatched in the same direction, and the intervals between the hatching lines are always the same. On adjacent parts, the direction of hatching is different.

Read drawings It becomes much easier if, before starting this lesson, you study the principle of operation of products using any documents (for example, device descriptions, explanatory notes, etc.).

Reading blueprints, you need to remember that according to the assembly ones or those depicted general form, the production of parts is not carried out, since they can be presented in a simplified form.

Detailing is the process of making working drawings based on assembly drawings or general view drawings.

In the process of detailing drawings under production conditions, they must contain both images of parts and all the information necessary for their production, as well as control of various parameters (for example, dimensions, etc.). To create working drawings, standard paper sizes must be used.

Compliance with all norms and requirements state standards is a prerequisite for the execution of both drawings and any other design documentation.

Reading blueprints allows you to determine what shape and geometric dimensions the parts depicted on them have, as well as what specific technologies need to be used for their manufacture (milling, turning, casting, stamping, etc.).

Blueprints, which are made in accordance with GOST-s, are easy to read, eliminate double interpretation of the shape and size of parts, provide them correct production and assembly.

In this small theoretical article I would like to talk about the basic concepts of construction drawings. Since many masters and not only craftsmen, in the course of their lives, quite often come across sketches, plans, diagrams, etc.
After all, everyone knows that in our sub-Soviet countries people need to know almost everything and understand all the laws, rules and strategies. In general, everything so that you are not deceived along the way in resolving this or that issue.
A simple example.
You have been to the technical interiorization office regarding the plan of your home. And they drew something for you there that would break the devil’s leg. It's good if everything is correct, but if it's not. Therefore, it is necessary to understand at least a little about drawing so that you can simply navigate the documents a little.
Our officials have a good saying: “Not knowing the law does not relieve you of responsibility.” On my own behalf, I would add that this is in everything you point at.
It’s clear that all the rules are in one post construction drawing not to cover. But at least you can try to tell the basics and main things.
Main difference drawing from drawing the fact that the drawing is done to scale, and the drawing is done in proportions.
In a drawing made in proportions, they try to maintain the relative sizes of the depicted objects. For example, a sofa in such a picture will be larger than, say, a stool.
In a drawing indicating dimensions, which is used in construction and interior design, images of objects are usually smaller than the actual ones; such a drawing is made on a certain scale.
Since once upon a time there were no huge sheets of paper on which it was possible to depict a life-size house, they came up with drawings drawn to scale, where objects are shown at a 100-fold reduction, i.e. 1 meter on the ground corresponds to 1 cm in the drawing.
In other words, scale M=1:100.
M is the scale, and the number 1: indicates the degree of reduction.
note, the larger the number after the colon, the greater the degree of reduction.
When creating interior drawings, scales are most often used.
M=1:50(items are reduced by 50 times) and M=1:25(25 times). For example, a bed measuring 2x1 m in the drawing will be 4x2 cm if reduced by 50 times and 8x4 cm if reduced by 25 times.
During the organization of the interior, the need often arises for individual fragments in more detail. Then they make a drawing on a scale of M=1:20 (one meter on the ground corresponds to 5 cm in the drawing) and even M=1:10.
When constructing a drawing, its scale is chosen depending on the actual dimensions of objects and their parts, so that the drawing is not overloaded with unnecessary details, and a sufficiently high accuracy of the image is achieved.
The drawing is carried out according to generally accepted international standards and understandable to specialists different countries, even if they don't know each other's language.
A drawing made to scale always has dimensions indicated.

Please note that the drawing gives a very economical representation of the object and contains only the information that is really necessary. Therefore, you should use the appropriate symbols, apply the correct dimensions and be sure to indicate the scale. All this, of course, is directly related to the general

Each skilled worker must understand the drawings in his specialty.

This drafting course teaches gypsum workers how to read blueprints, make sketches and drawings of simple parts, and formulate improvement suggestions or improvements.

§ 1. DRAWING AND ITS SIGNIFICANCE

A drawing of an object (product) is its image on paper, defining the shape, internal organization, dimensions and other technical data necessary for a clear presentation of the item.

Each machine or mechanism consists of individual parts connected to each other by bolts, pins, keys, rivets, etc. In order to produce individual parts, drawings of these parts are drawn up, and in order to correctly connect them into one whole, assembly drawings are drawn up units, mechanisms, machines and other products. Thus, part drawings and assembly drawings serve as technical documents according to which parts are manufactured and the corresponding products are assembled from them.

Arrangement of views in drawings. To have a clear idea of ​​an object and its size, the object is viewed from all sides: front, top, left or right, bottom or back. To have an idea of ​​an object and its dimensions according to the drawing, it is necessary to show in the drawing images of this object from the front, top, left or right.

Such images of an object in a drawing are called views or projections. How views should be arranged in a drawing is established by the State All-Union Standard (GOST 3453-59) “Drawings in Mechanical Engineering”.

Images of an object are obtained by the method of rectangular projection of it on the projection plane, assuming that the object is always located between the observer’s eye and the projection plane. The faces of the cube are taken as the main projection planes, onto which the object is projected (Fig. 1). .Then all the faces of the cube (projection planes) with the projections of the object are combined with frontal plane projections and obtain all views (projections) of an object on one plane (Fig. 2). In this order I arrange the types of the object in the drawing. Front view

howl edges (for stitching drawings). In the lower right corner of the drawing frame, a corner stamp of the organization drawing up the drawings is applied, with the signatures of the performers and other data.

In drawings, solid, dashed, dot-dotted and wavy lines of a certain thickness are used. In Fig. 3 shows the lines of the drawings. The thickness of these lines is conventionally designated by the letter b ы2 b/3, while the thickness of the main line

drawing b is taken in the range from 0.6 to 1.6 mm depending on the size of the image.

Explanatory inscriptions on the drawings are made in drawing font (GOST 3463-59). Sample of this font (size 7)

shown in Fig. 4 for uppercase (capital) and lowercase letters and numbers

Scales of drawings. Scale is the ratio of the size of the product in the drawing to its actual size. Large objects: flywheels, machine bodies, engine shafts, etc. cannot be depicted on a sheet of paper in full size, so they are drawn in a reduced form using a reduction scale. Many small parts, on the contrary, you have to draw in an enlarged size to get an image that is convenient for use. The scale of the drawings is established by the State All-Union Standard (GOST 3451-59) and is given below.

Magnification ratio: 1:1; 2:1; (2.5:1); 5:1; 10:1.

The scales indicated in brackets apply in exceptional cases.

The scales in the drawings are indicated as follows: Ml: 1; Ml: 2; M2: I, etc. The drawing of the product can be made on any scale, but the dimensions are those that the product has in kind.

Applying dimensions. An error in size leads to defects in production. Part dimensions after final processing indicated in the drawings in millimeters, with the exception of pipe and inch thread sizes, which are indicated in inches

max (1 inch equals 25.4 mm).

The word millimeter is not written on the drawing. Each size in the drawing is indicated only once and only in one view. Dimensional numbers are applied above the dimension line and, as an exception, in the gap in the dimension line (Fig. 5). Dimension lines are drawn both in views of the part (inside the outline) and outside the outline of the part. The arrows of dimension lines should rest with their tips on the contour lines or extension lines. If there is limited space for arrows, they can be replaced with dots or dashes (see Fig. 5). Radii of fillets and other rounded parts - 8

it is marked with the Latin letter R (Fig. 6). Diameter size indicate conventional sign 0> he explains that the part shown in the drawing has round shape. In Fig. 6 shown

(see Fig. 6). Details of a symmetrical shape can be depicted - not completely in the views, but a little more than half; in such cases, an arrow is placed on the dimension line at one end

(Fig. 7). When applying dimensions from the general base of a part, it is recommended to apply dimension lines as shown in Fig. 8.

The base is the original surface of the part, in relation to which all dimensions are oriented. IN practical work There are different conventions for applying dimensions; they must be studied in GOST 3458-59.

Limit deviations allowed in the manufacture and processing of parts. In mechanical engineering, very small deviations from specified dimensions are allowed to ensure the interchangeability of parts of the same name included in a mechanism or unit. To allow the shaft to rotate freely, there is a gap in the cylindrical bore of the bearing between the shaft and the bore in which the lubricant is placed. The gap between the parts is equal to fractions of a millimeter. The specified size in the drawing, around which the dimensions of the hole and shaft diameters fluctuate, is called nominal size. The upper and lower permissible deviations from the nominal size determine the tolerance for the manufacture of the part. Maximum deviations are indicated by a plus sign (+) or minus sign (-) and are written on the drawings following the size of the part in small numbers. For example, on the shaft, after the nominal size 20, it is written (Fig - 9)” this means

It is expected that all shafts with a diameter between 20.1 and 19.8 mm are suitable for use in machines. Maximum deviations equal to zero are not indicated on the drawings.