Basic rules for drawing up drawings

Modern society in its development and economic activity is actively using the graphical language, which to date there is no alternative (holographic technology is still at the development stage). Graphic language finds its technological application by drawing the projections of three-dimensional objects in a two-dimensional plane. This method has an interesting history, but not it is the subject of this article. Our goal is to provide the reader with an overview of drafting as an accurate and universal tool for the engineer and architect, in terms of its overall regulatory framework.

A specialist who knows the rules for drawing up drawings must also competently guide in his work the relevant GOSTs that define the basic mandatory requirements for the drawings. Also important is its qualification, which allows even for complex shapes to represent geometric constructions on drawings with optimal visibility.

What you need to know and be able to do drawings

First, it is assumed that the luggage of the knowledge of the architect or the design engineer includes ESDC - the rules for drawing up drawings and the practical skills of optimal geometric representations of the projections of the part for its display in the drawings.

At present, modern productive specialized programs - computer-aided design systems have replaced the traditional "manual" drawing. However, automation still requires a solid knowledge of the following GOSTs:

- 2.301-68 - the formatting of sheets of drawings in paper or electronic forms;

- 2.302-68 - determining the ratio of the dimensions of the object depicted in the drawing to its actual dimensions (scale);

- 2.303-68 - regulating the line drawing on the drawings recommended by the current industry standards;

- 2.304-81 - setting the actual drawing fonts;

-2.307-68 - determining the drawing on the drawing of both dimensions and limiting deviations.

Important qualification requirements for the executor of the drawings are:

- Practical ability to use ESKD - drawing rules for applied tasks;

- the skills of geometric constructions for the optimal execution of drawings, which are then conveniently used in marking for the manufacture of specific parts.

Basics of creating drawings

Development of design documentation (the creation of which is regulated by ESKD - the rules for drawing up drawings) is an obligatory stage preceding the immediate production of the part.

At the same time, the specifics of what is made and what is what is fundamentally important; What is the standard name of the product; Its exact dimensions, shape, from what materials it is made. All this is important, since later the design documentation will become the main guarantor of the identity of the workpiece and, if necessary, its interchangeability with an analog produced by other manufacturers. From the point of view of the use of a single tool (rules and norms) by different manufacturers, the ESKD rules they hold are important - the rules for drawing up drawings.

GOST, regulating the drafting

We have already mentioned in this article the terms ESKD, GOSTs in the context of their normative role for the engineer. Let us determine their relationship.

The role of the regulatory regulator in the design of various drawings and schemes for design documents is played by specially developed at the state level uniform technological standards - GOSTs. These standards are organizationally united by a single system of design documentation, or ESKD.

The rules of the ESKD regulate the execution of drawings, relevant to the stages of creation, finalization and organization of their proper document circulation as a type of documentation within the framework of specialized enterprises and organizations, as well as in the institutions of the Ministry of Education. ESKD - rules for drawing up drawings - are consistent with the current international ISO standards (i.e., approved by the International Standardizing Organization), and also comply with the requirements of the permanent international standardization commission.

It should be noted that compliance with state standards is mandatory in all areas of industry, as well as in scientific and design institutions. Accordingly, GOST - the rules for the drawing up of drawings - are compulsory when studying engineering graphics in educational institutions.

Thus, despite the progress of automation in the creation of drawings, GOSTs should be known. However, we have a presentiment of the main line of objections of our computer-literate opponents, that all the rules have already been observed in the drawings, which should simply be found on the Internet.

Is it possible, by drawing, not to know GOSTs? No!

However, we will work on the lead, noting that yes, indeed at the present time on the Internet any PC user can choose from thousands and thousands of photo drawings the right one. And then he, using a special program for recognition, gets the required drawing.

However, here our opponents are cunning. In fact, the programs for recognizing drawings are imperfect, accordingly, the drawing obtained with their help obviously contains significant errors. Of course, they will have to be corrected further, using knowledge of GOSTs.

It is much more reasonable in this situation to creatively use photo drawings as an example, really recreating them with the help of a specialized program - the computer aided design system. Leading representative of CAD for several decades now is AutoCAD development company with a world-class "Autodesk". This program is now actively used by leading design bureaus. Kulmans have gone down in history!

Formats. State Standard 2.301-68

Drawings are performed on a paper sheet having certain, clearly defined by the current GOST, dimensions, and the frame for the drawing is measured (A4 has dimensions of 210 by 297 mm, see table 1).

Table 1. Formats.

Format А4	Smaller side 210 mm	Large side 297 mm
A3 format	Smaller side 297 mm	Large side 420 mm
Format A2	Smaller side 420 mm	Large side 594 mm
Format A1	Smaller side 594 mm	Large side 841 mm
Format A0	Smaller side 841 mm	Large side 1189 mm

Note that sometimes the frame for A4 drawing limits the known excess space, which exceeds the image size. In this case, a smaller format is appropriate - A5, whose sides dimensions are 148 by 210 mm.

A visual display of the claimed formats, which define the basic rules for drawing up drawings, is shown in Fig. 1:

Fig. 1. Format ratio

The main inscription

The main inscription is placed on all drawings, except for A4, both along the long side and along the short one. For A4, it is shown exclusively along the short side, since this format is vertical.

The additional column (also excluding A4) is placed on the long side

(The location of the main inscription is shown in Figure 2.)

Fig.2. Placing the title block

Drawing of the frame of the drawing is regulated by its distance from the edge of the sheet: on all sides (except for the left) - 5 mm. On the left, the distance from the frame to the edge of the sheet is 20 mm. In this case, the line that surrounds the frame of the drawing should not be already 0.7 mm.

The main inscriptions are made in accordance with GOST No. 2.104-68, which determines the dimensions, shape, and the order of filling. It is characteristic that it is an indispensable element of any kind of drawings and schemes. As an example, we give the main inscription recommended for use in training drawings (see Figure 3).

Figure 3. The main inscription recommended for training drawings

The figures in the figure indicate the following graphs of the main inscription:

1 - the name of the product;

2 - how the document is designated;

3 - what material is chosen for manufacturing the part;

4 - the props of the enterprise - the index.

Often the drawing is performed on several sheets. In this case, on the second and all subsequent ones, the title block is executed in a different form than the first one. Its image is shown in Fig. 4.

Figure 4. The main inscription for the second and subsequent sheets of the drawing

Its graphs (in the figure they are numbered) are filled in according to the above decoding of these figures for the main inscription of the first sheet.

Designations on drawings

By definition, a drawing is a scaled graphic representation of a product, where the dimensions and specifications are indicated . The information that the drawing contains is sufficient for the manufacture of the product mentioned in the definition.

The rules for applying dimensional values to drawings in industry are regulated by GOST No. 2.307-68. This is a fairly subtle point in the design of drawings. After all, only one missed size turns a complex drawing into unclaimed empty work.

The sizes in drafting are subdivided into several types. The first group is the size of the workers. This is the information that is used directly in the manufacture. The second is the reference dimensions (they are indicated by the symbol (*)). They are used in engineering work with a drawing.

Dimension the drawing using dimensional lines. Designations are drawn on the drawing in accordance with the adopted scale. Its meaning is found in the main inscription - in a separate box. We define the notion of scale: it is identified with the ratio of the actual dimensions of the object to the dimensions of its image. If possible, the scale is one-to-one, however, as you understand, for different sizes of the part it is necessary either to reduce or increase. Acceptable scales of the image are determined by GOST 2.302-68 cm (see table 2).

Table 2. Scale used in drawing

The criterion for selecting a scale is the further convenience of working with the drawing.

Lines

The drawings show different types of lines, each of which has a specific purpose. The use of lines in the drawings is determined by GOST 2.303-68.

The solid solid line serves to draw the visible outlines of the displayed object. The thickness for it is determined in the range of 0.5-1.4 mm and in the future the selected value is denoted by the letter S. Why is this value assigned to a conditional variable? The fact is that in the future the thicknesses of all other lines will be commensurate with the thickness of the main one.

The dashed line depicts its invisible contours. Its thickness lies within s / 3-s / 2. In this case, the length of one stroke is within 3-8 mm, and the distance between them is 3-4 mm, in addition, the length of all strokes in the drawing should be equal, however, the same applies to the intervals separating them.

A continuous thin line is in demand for displaying either extension lines or dimensional lines. Its thickness is the same as the thickness of the dashed line: s / 3-s / 2.

The continuous wavy line is applied to the place of the drawing of the part where, due to the considerable size and uniform shape of a certain part of the part, it is expedient to designate the rupture of such a fragment. Its thickness is also s / 3 - s / 2.

Line thin dot-and-dashed line designates lines of symmetry - axial and centric. (It is stipulated that if such a line passes through the center of a circle, then in the center there should be a stroke, not a point.)

Drawing assembly

Registration of the assembly drawing has its own peculiarities. Often, a part or mechanism has a rather complex structure, consists of several parts joined together by riveting, welding, and other rigid connections. In the drawings, such 1-3 joints are formed as the main assembly drawing, where only the dimensions of the main part are given. To it are attached separate drawings of all the other parts to be connected with their dimensions.

Sketches of technological documentation

Diversified and informative technological drawing. Assembly drawings are not the only element of technological documentation. It also includes technological sketches. It is guided by them, you can determine the material from which the product is manufactured, as well as familiarize yourself with the methods of its assembly and installation.

Dimensional tolerances in the drawings

The dimensional designations in the drawings are accompanied by an indication of the tolerable marginal deviations in the processing of the part. Such deviations may be indicated either by numbers, for example 19 + 0.014, or by qualification. ("Qualities" - in English "quality").

The qualification (or the degree of deviation that can be allowed) is called the conditional level of accuracy. There are only 19 such levels. Within each quality class, as the linear dimensions of products increase, the tolerances for them, expressed in millimeters, also increase. The most accurate qualify number 01, and the least accurate - number 17 (except for the 01th qualitat, there are also "zero", and the 1st.). A qualifier from a nominal size is denoted by the letter H if it has a positive value and, accordingly, h if it has a negative value. The figure following the letter, just indicates the number of the qualification used. For example, designation 28H7 should be read as: nominal size 28 mm, tolerance - + 7.

Drawing up of working drawings

The working drawing is characterized by the minimum number of projections of the part that gives an idea of its shape and elements. The working drawing also carries information about the material, and in construction, for example, usually on a scale of either 1 to 10 or 1 to 15. Table 3 contains the symbols for such materials.

Table 3. Notation

The rules for drawing up working drawings contain specific organizational recommendations that make it possible to arrange technological documentation in the best possible way. Of course, the engineer, when carrying out the drawings, should strive (of course, if possible) to execute them in a single format. Choosing the scale of the image, it is the main criterion that makes the perception of the detail image convenient.

It should be taken into account that the scale is not the basis to determine the dimensions of the working drawing.

The execution of working drawings of large elements having a lattice structure has its own characteristics. Two types of sizes appear in it: the general geometric structure of the grid is drawn on a smaller scale, and the lattice elements themselves are drawn on a larger scale.

Concerning the working drawings of curvilinear elements, an important point is important, answering the question: "Dimensions are represented by which marking line?". For bent sheets, for example, such a guide is a neutral line. And the folds in this case are shown not in a degree dimension, but by representing them with rectangular triangles with the length of the legs indicated in the working drawing.

In the working drawing of each part is assigned its own number. Uniform parts are always denoted by the same number. However, in the latter case, one should be careful, since the mirror-symmetric parts can also meet. They can not be designated with the same number.

Architectural and construction drawings

According to the procedure, which is regulated by the rules of drawing up of construction drawings (GOST 21.501-93), the main building structures, its steps and spans on architectural drawings are tied to the coordinate axes. The same axes are carried out with dash-dot lines and are numbered.

The left side of the drawing takes out the longitudinal axis, and the right side - the transverse. The numbering of the transverse axes is made by Arabic numerals, and the longitudinal ones by Russian letters.

Remote and dimensional lines are used for the dimension of the architectural drawing. Dimensions of the smallest sections of the floor are applied on the first dimension line from the drawing (rules for the design of architectural drawings, GOST 21.501-93). Next - in ascending order. The last dimensional line visualizes information about the dimensions between the extreme axes of the building.

The lengths of the dimensional lines of the outer walls, corresponding to the location of the doors and windows, limit the lines to the outline, displaced towards the drawing by 3-4 mm.

For the convenience of reading the architectural drawing, internal extension lines are used. Their purpose is to show the width of the doors, the thickness of partitions and walls, and the size of the rooms.

The number of floors is displayed on architectural drawings with the help of marks (levels). They are usually applied to the facade section. They are indicated by arrows with "feathering" at 45 ⁰ . The zero mark is usually taken to the level of the clean floor or the floor of the first floor. The marks of the remaining floors are denoted by a numerical value.

The slope in the architectural drawings is indicated by a specific "angled" sign pointing toward the slope itself, and a numerical value indicating the ratio of the legs of a right-angled triangle to the similar slope of the hypotenuse (see Figure 4).

Figure 4. Designation of gradients in architectural drawings

The rules of registration of architectural and construction drawings are visually observed when performing a special type of drawing, called a floor plan.

Elements of the floor plan

The floor plan is made according to the type of its cut by a horizontal plane at a height of one third of the height of the room (just above the level of the window sill). On it, individual rooms are depicted by a thin line, and similar to the mezzanine of the structure, placed above the plane of the cut, is a dashed line.

With such a display of the floor, the indication of the mark to which it refers applies. The following basic elements are distinguished on the floor plan:

- coordinate axes corresponding to the main structural elements;

- internal and external dimensions;

- marks corresponding to the levels of clean floors;

- lines of cuts (for visual display of window and door openings);

- fragments and nodes of the plan;

- the name of the premises, as well as their area.

Conclusion

Drawing is a special graphical language for displaying spatial forms and images of objects. Exhaustive information about various products, thanks to drafting, becomes publicly available in the form of file records, not only for one enterprise, but for whole industries of different countries. And from this point of view, the role of drawing in the development of industry is obvious.

With its help, according to the trends of the scientific and technological revolution, new creative ideas are generated that transform the material world around us.

Today, to find a similar example of drawing design, it is enough to download the PC and enter the Internet. Modern design automation systems have made it possible to increase the efficiency of drawing design tens of times, by comparison with the last century, by reducing labor intensity. This, in turn, shortens the process of creating new products in time, provides it with a large amount of necessary graphic information.