Graphic work 4 on drawing. Practical and graphic work on drawing. Reinforcement task

a) Construction of the third type based on two given ones.

Construct a third type of part based on two data, put down dimensions, and make a visual representation of the part in an axonometric projection. Take the task from Table 6. Sample of completing the task (Fig. 5.19).

Methodical instructions.

1. The drawing begins with the construction of axes of symmetry of the views. The distance between views, as well as the distance between views and the drawing frame, is taken to be: 30-40 mm. The main view and the top view are constructed. The two constructed views are used to draw the third view - the view on the left. This view is drawn according to the rules for constructing third projections of points for which two other projections are given (see Fig. 5.4 point A). When projecting a part with a complex shape, you have to simultaneously construct all three images. When constructing the third view in this task, as well as in subsequent ones, you can not draw projection axes, but use the “axisless” projection system. One of the faces (Fig. 5.5, plane P) can be taken as the coordinate plane, from which the coordinates are measured. For example, having measured a segment on the horizontal projection for point A, expressing the coordinate Y, we transfer it to the profile projection, we obtain the profile projection A 3. As a coordinate plane, you can also take the plane of symmetry R, ​​the traces of which coincide with the axial line of the horizontal and profile projection, and from it the coordinates Y C, Y A can be measured, as shown in Fig. 5.5, for points A and C.

Rice. 5.4 Fig. 5.5

2. Each detail, no matter how complex it may be, can always be divided into a number of geometric bodies: prism, pyramid, cylinder, cone, sphere, etc. Projecting a part comes down to projecting these geometric bodies.

3. The dimensions of objects should be applied only after constructing the view on the left, since in many cases it is in this view that it is advisable to apply part of the dimensions.

4. For a visual representation of products or their components, axonometric projections are used in technology. It is recommended to first study the chapter “Axonometric projections” in the descriptive geometry course.

For a rectangular axonometric projection, the sum of the squares of the distortion coefficients (indicators) is equal to 2, i.e.

k 2 + m 2 + n 2 =2,

where k, m, n are coefficients (indicators) of distortion along the axes. In isometric

projections, all three distortion coefficients are equal to each other, i.e.

k = m = n = 0.82

In practice, for the simplicity of constructing an isometric projection, the distortion coefficient (indicator) equal to 0.82 is replaced by the reduced distortion coefficient equal to 1, i.e. build an image of an object, enlarged by 1/0.82 = 1.22 times. The X, Y, Z axes in an isometric projection make 120° angles with each other, while the Z axis is directed perpendicular to the horizontal line (Fig. 5.6).

In a dimetric projection, two distortion coefficients are equal to each other, and the third in a particular case is taken equal to 1/2 of them, i.e.,

k = n = 0.94; and m =1/2 k = 0.47

In practice, for the simplicity of constructing a dimetric projection, the distortion coefficients (indicators) equal to 0.94 and 0.47 are replaced with the given distortion coefficients equal to 1 and 0.5, i.e. construct an image of an object, enlarged by 1/0.94 = 1.06 times. The Z axis in rectangular diameter is directed perpendicular to the horizontal line, the X axis is at an angle of 7°10", the Y axis is at an angle of 41°25". Since tg 7°10" ≈ 1/8, and tg 41°25" ≈ 7/8, these angles can be constructed without a protractor, as shown in Fig. 5.7. In rectangular dimetry, natural dimensions are laid out along the X and Z axes, and with a reduction factor of 0.5 along the Y axis.

The axonometric projection of a circle is generally an ellipse. If the circle lies in a plane parallel to one of the projection planes, then the minor axis of the ellipse is always parallel to the axonometric rectangular projection of the axis that is perpendicular to the plane of the depicted circle, while the major axis of the ellipse is always perpendicular to the minor one.

In this task, it is recommended to visualize the part in an isometric projection.

b) Simple cuts.

Construct the third type of part based on two data, make simple cuts (horizontal and vertical planes), put down dimensions, make a visual representation of the part in an axonometric projection with a 1/4 part cut out. Take the task from Table 7. Sample of completing the task (Fig. 5.20).

Complete the graphic work on a sheet of drawing paper in A3 format.

Methodical instructions.

1. When completing the task, pay attention to the fact that if the part is symmetrical, then it is necessary to combine half the view and half the section in one image. At the same time, in sight don't show invisible contour lines. The boundary between the appearance and the section is the dash-dot axis of symmetry. Section image details located from the vertical axis of symmetry to the right(Fig. 5.8), and from the horizontal axis of symmetry – from below(Fig. 5.9, 5.10) regardless of which projection plane it is depicted on.

Rice. 5.9 Fig. 5.10

If the projection of an edge belonging to the external outline of the object falls on the axis of symmetry, then the incision is made as shown in Fig. 5.11, and if an edge belonging to the internal outline of the object falls on the axis of symmetry, then the cut is made as shown in Fig. 5.12, i.e. in both cases, the projection of the edge is preserved. The boundary between the section and the view is shown with a solid wavy line.

Rice. 5.11 Fig. 5.12

2. On images of symmetrical parts, in order to show the internal structure in an axonometric projection, a cutout is made of 1/4 of the part (the most illuminated and closest to the observer, Fig. 5.8). This cut is not associated with the incision on orthogonal views. So, for example, on a horizontal projection (Fig. 5.8), the axes of symmetry (vertical and horizontal) divide the image into four quarters. By making an incision on the frontal projection, it is as if the lower right quarter of the horizontal projection is removed, and in the axonometric image the lower left quarter of the model is removed. The stiffening ribs (Fig. 5.8), which fall into the longitudinal section on orthogonal projections, are not shaded, but shaded in axonometry.

3. The construction of the model in axonometry with a one-quarter cutout is shown in Fig. 5.13. The model constructed in thin lines is mentally cut by the frontal and profile planes passing through the Ox and Oy axes. The quarter of the model enclosed between them is removed, revealing the internal structure of the model. When cutting the model, the planes leave a mark on its surface. One such trace lies in the frontal, the other in the profile plane of the section. Each of these traces is a closed broken line consisting of segments along which the cut plane intersects with the faces of the model and the surface of the cylindrical hole. Figures lying in the section plane are shaded in axonometric projections. In Fig. Figure 5.6 shows the direction of the hatch lines in isometric projection, and Fig. 5.7 – in dimetric projection. Hatching lines are drawn parallel to the segments that cut off identical segments on the axonometric axes Ox, Oy and Oz from point O in an isometric projection, and in a dimetric projection on the Ox and Oz axes - identical segments and on the Oy axis - a segment equal to 0.5 segments on the axis Ox or Oz.

4. In this task, it is recommended to visualize the part in a dimetric projection.

5. When determining the true type of section, one must use one of the methods of descriptive geometry: rotation, alignment, plane-parallel movement (rotation without specifying the position of the axes) or changing projection planes.

In Fig. 5.14 shows the construction of projections and the true view of the section of a quadrangular prism by the frontally projecting plane G by changing the projection planes. The frontal projection of the section will be a line coinciding with the trace of the plane. To find the horizontal projection of the section, we find the points of intersection of the edges of the prism with the plane (points A, B, C, D), connecting them, we get a flat figure, the horizontal projection of which will be A 1, B 1, C 1, D 1.

symmetry, parallel to the axis x 12, will also be parallel to the new axis and be at a distance from it equal to b 1.In the new system of projection planes, the distances of points to the axis of symmetry are kept the same, as in the previous system, so to find them you can set aside distances ( b 2) from the axis of symmetry. By connecting the obtained points A 4 B 4 C 4 D 4, we obtain the true view of the section by plane G of the given body.

In Fig. Figure 5.16 shows the construction of the true cross-section of a truncated cone. The major axis of the ellipse is determined by points 1 and 2, the minor axis of the ellipse is perpendicular to the major axis and passes through its middle, i.e. point O. The minor axis lies in the horizontal plane of the base of the cone and is equal to the chord of the circle of the base of the cone passing through point O.

The ellipse is limited by the straight line of intersection of the cutting plane with the base of the cone, i.e. a straight line passing through points 5 and 6. Intermediate points 3 and 4 are constructed using the horizontal plane G. In Fig. Figure 5.17 shows the construction of a section of a part consisting of geometric bodies: a cone, a cylinder, a prism.

Rice. 5.16

Rice. 5.17

c) Complex cuts (complex step cut).

Construct the third type of part based on two data, make the indicated complex cuts, construct an inclined section using the plane specified in the drawing, put down dimensions, and make a visual representation of the part in an axonometric projection (rectangular isometry or dimetry). Take the task from Table 8. Sample of completing the task (Fig. 5.21). Complete the graphic work on two sheets of A3 drawing paper.

Methodical instructions.

1. When performing graphic work, you need to pay attention to the fact that a complex step section is depicted according to the following rule: the cutting planes are, as it were, combined into one plane. The boundaries between the cutting planes are not indicated, and this section is designed in the same way as a simple section made not along the axis of symmetry.

2. In the assignment, some of the dimensions, due to the lack of a third image, are not placed appropriately, so the dimensions must be applied in accordance with the instructions given in the “Applying Dimensions” section, and not copied from the assignment.

3. In Fig. 5.21. shows an example of making a part image in rectangular isometry with a complex cutout.

d) Complex cuts (complex broken cut).

Construct the third type of part based on two data, make the indicated complex broken section, and add dimensions. Take the task from Table 9. Sample of completing the task (Fig. 5.22).

Complete the graphic work on a sheet of A4 drawing paper.

Methodical instructions.

In Fig. Figure 5.18 shows an image of a complex broken section obtained by two intersecting profile-projecting planes. To obtain a section in an undistorted form when cutting an object with inclined planes, these planes, together with the section figures belonging to them, are rotated around the line of intersection of the planes to a position parallel to the plane of projections (in Fig. 5.18 - to a position parallel to the frontal plane of projections). The construction of a complex broken section is based on the method of rotation around a projecting straight line (see the course on descriptive geometry). The presence of kinks in the section line does not affect the graphic design of a complex section - it is designed as a simple section.

Options for individual assignments. Table 6 (Construction of the third type).

Examples of task completion.

Rice. 5.22

1. a) According to the teacher’s instructions, construct an axonometric projection of one of the parts (Fig. 98). On the axonometric projection, draw images of points A, B and C; label them. b) Answer the questions:

Rice. 98. Tasks for graphic work No. 4

1. What types of parts are shown in the drawing?
2. What geometric bodies combine to form each part?
3. Are there holes in the part? If so, what geometric shape does the hole have?
4. Find on each of the views all flat surfaces perpendicular to the frontal and then to the horizontal planes of projection.
1. Based on the visual representation of the parts (Fig. 99), complete the drawing in the required number of views. Draw on all views and mark points A, B and C.

Rice. 99. Tasks for graphic work No. 4

§ 13. The procedure for constructing images in drawings

13.1. A method for constructing images based on analysis of the shape of an object. As you already know, most objects can be represented as a combination of geometric bodies. Investigator, to read and execute drawings you need to know. how these geometric bodies are depicted.

Now that you know how such geometric bodies are depicted in a drawing, and have learned how vertices, edges and faces are projected, it will be easier for you to read drawings of objects.

Figure 100 shows a part of the machine - the counterweight. Let's analyze its shape. What geometric bodies do you know that it can be divided into? To answer this question, let us recall the characteristic features inherent in the images of these geometric bodies.

Rice. 100. Part projections

In Figure 101, a. one of them is highlighted in blue. What geometric body has such projections?

Projections in the form of rectangles are characteristic of a parallelepiped. Three projections and a visual image of the parallelepiped, highlighted in Figure 101, a in blue, are given in Figure 101, b.

In Figure 101, another geometric body is conventionally highlighted in gray. What geometric body has such projections?

Rice. 101. Part shape analysis

You encountered such projections when considering images of a triangular prism. Three projections and a visual image of the prism, highlighted in gray in Figure 101, c, are given in Figure 101, d. Thus, the counterweight consists of a rectangular parallelepiped and a triangular prism.

But a part has been removed from the parallelepiped, the surface of which is conventionally highlighted in blue in Figure 101, d. What geometric body has such projections?

You encountered projections in the form of a circle and two rectangles when considering images of a cylinder. Consequently, the counterweight contains a hole in the shape of a cylinder, three projections and a visual image of which are given in Figure 101. f.

Analysis of the shape of an object is necessary not only when reading, but also when making drawings. Thus, having determined the shape of which geometric bodies the parts of the counterweight shown in Figure 100 have, it is possible to establish an appropriate sequence for constructing its drawing.

For example, a drawing of a counterweight is built like this:

1. on all views, a parallelepiped is drawn, which is the basis of the counterweight;
2. a triangular prism is added to the parallelepiped;
3. draw an element in the form of a cylinder. In the top and left views it is shown with dashed lines, since the hole is invisible.

Draw the description of a part called a bushing. It consists of a truncated cone and a regular quadrangular prism. The total length of the part is 60 mm. The diameter of one base of the cone is 30 mm, the other is 50 mm. The prism is attached to a larger cone base, which is located in the middle of its base measuring 50X50 mm. The height of the prism is 10 mm. A through cylindrical hole with a diameter of 20 mm is drilled along the axis of the bushing.

13.2. The sequence of constructing views in a detail drawing. Let's consider an example of constructing views of a part - support (Fig. 102).

Rice. 102. Visual representation of the support

Before you start constructing images, you need to clearly imagine the general initial geometric shape of the part (whether it will be a cube, cylinder, parallelepiped, etc.). This form must be kept in mind when constructing views.

The general shape of the object shown in Figure 102 is a rectangular parallelepiped. It has rectangular cutouts and a triangular prism cutout. Let's start depicting the part with its general shape - a parallelepiped (Fig. 103, a).

Rice. 103. Sequence of constructing part views

By projecting the parallelepiped onto the planes V, H, W, we obtain rectangles on all three projection planes. On the frontal plane of projections the height and length of the part will be reflected, i.e. dimensions 30 and 34. On the horizontal plane of projections - the width and length of the part, i.e. dimensions 26 and 34. On the profile plane - width and height, i.e. dimensions 26 and 30.

Each dimension of the part is shown without distortion twice: height - on the frontal and profile planes, length - on the frontal and horizontal planes, width - on the horizontal and profile planes of projections. However, you cannot apply the same dimension twice in a drawing.

All constructions will be done first with thin lines. Since the main view and the top view are symmetrical, axes of symmetry are marked on them.

Now we will show the cutouts on the projections of the parallelepiped (Fig. 103, b). It makes more sense to show them first in the main view. To do this, you need to set aside 12 mm to the left and to the right from the axis of symmetry and draw vertical lines through the resulting points. Then, at a distance of 14 mm from the top edge of the part, draw horizontal straight segments.

Let's construct projections of these cutouts on other views. This can be done using communication lines. After this, in the top and left views you need to show the segments that limit the projections of the cutouts.

In conclusion, the images are outlined with the lines established by the standard and the dimensions are applied (Fig. 103, c).

1. Name the sequence of actions that make up the process of constructing types of an object.
2. What purpose are projection lines used for?

13.3. Constructing cuts on geometric bodies. Figure 104 shows images of geometric bodies, the shape of which is complicated by various kinds of cutouts.

Rice. 104. Geometric bodies containing cutouts

Parts of this shape are widely used in technology. To draw or read their drawing, you need to imagine the shape of the workpiece from which the part is made, and the shape of the cutout. Let's look at examples.

Example 1. Figure 105 shows a drawing of the gasket. What shape does the removed part have? What was the shape of the workpiece?

Rice. 105. Gasket shape analysis

Having analyzed the drawing of the gasket, we can come to the conclusion that it was obtained as a result of removing the fourth part of the cylinder from a rectangular parallelepiped (blank).

Example 2. Figure 106a shows a drawing of a plug. What is the shape of its blank? What resulted in the shape of the part?

Rice. 106. Constructing projections of a part with a cutout

After analyzing the drawing, we can come to the conclusion that the part is made from a cylindrical blank. There is a cutout in it, the shape of which is clear from Figure 106, b.

How to construct a projection of the cutout in the view on the left?

First, a rectangle is drawn - a view of the cylinder on the left, which is the original shape of the part. Then a projection of the cutout is constructed. Its dimensions are known, therefore, points a", b" and a, b, defining the projections of the cutout, can be considered as given.

The construction of profile projections a, b" of these points is shown by connection lines with arrows (Fig. 106, c).

Having established the shape of the cutout, it is easy to decide which lines in the left view should be outlined with solid thick main lines, which with dashed lines, and which to delete altogether.

1. Look at the images in Figure 107 and determine what shape the parts are removed from the blanks to obtain parts. Make technical drawings of these parts.

Rice. 107. Exercise tasks

1. Construct the missing projections of the points, lines and cuts specified by the teacher on the drawings you completed earlier.

13.4. Construction of the third type. Sometimes you will have to complete tasks in which you need to build a third using two existing types.

In Figure 108 you see an image of a block with a cutout. There are two views: front and top. You need to build a view on the left. To do this, you must first imagine the shape of the depicted part.

Rice. 108. Drawing of a block with a cutout

Having compared the views in the drawing, we conclude that the block has the shape of a parallelepiped measuring 10x35x20 mm. A rectangular cutout is made in the parallelepiped, its size is 12x12x10 mm.

The view on the left, as we know, is placed at the same height as the main view to the right of it. We draw one horizontal line at the level of the lower base of the parallelepiped, and the other at the level of the upper base (Fig. 109, a). These lines limit the height of the view on the left. Draw a vertical line anywhere between them. It will be the projection of the back face of the block onto the profile projection plane. From it to the right we will set aside a segment equal to 20 mm, i.e. we will limit the width of the bar, and we will draw another vertical line - the projection of the front face (Fig. 109, b).

Rice. 109. Construction of the third projection

Let us now show in the view on the left the cutout in the part. To do this, put a 12 mm segment to the left of the right vertical line, which is the projection of the front edge of the block, and draw another vertical line (Fig. 109, c). After this, we delete all auxiliary construction lines and outline the drawing (Fig. 109, d).

The third projection can be constructed based on an analysis of the geometric shape of the object. Let's look at how this is done. Figure 110a shows two projections of the part. We need to build a third one.

Rice. 110. Construction of the third projection from two data

Judging by these projections, the part is composed of a hexagonal prism, a parallelepiped and a cylinder. Mentally combining them into a single whole, let’s imagine the shape of the part (Fig. 110, c).

We draw an auxiliary straight line in the drawing at an angle of 45° and proceed to construct the third projection. You know what the third projections of a hexagonal prism, parallelepiped and cylinder look like. We draw sequentially the third projection of each of these bodies, using connection lines and axes of symmetry (Fig. 110, b).

Please note that in many cases there is no need to construct a third projection in the drawing, since rational execution of images involves constructing only the necessary (minimum) number of views sufficient to identify the shape of the object. In this case, the construction of the third projection of the object is only an educational task.

1. You have become familiar with different ways to construct the third projection of an object. How are they different from each other?
2. What is the purpose of using a constant line? How is it carried out?

1. In the drawing of the part (Fig. 111, a) the view on the left is not drawn - it does not show images of a semicircular cutout and a rectangular hole. As instructed by the teacher, redraw or transfer the drawing onto tracing paper and complete it with the missing lines. What lines (solid main or dashed) do you use for this purpose? Draw the missing lines also in Figures 111, b, c, d.

Rice. 111. Tasks for drawing missing lines

1. Redraw or transfer onto tracing paper the data in Figure 112 of the projection and construct profile projections of the parts.

Rice. 112. Exercise tasks

1. Redraw or transfer onto tracing paper the projections indicated to you in Figure 113 or 114 by your teacher. Construct the missing projections in place of the question marks. Perform technical drawings of parts.

Rice. 113. Exercise tasks

Rice. 114. Exercise tasks

2.1. The concept of ESKD standards. If each engineer or draftsman executed and designed drawings in his own way, without following the same rules, then such drawings would not be understandable to others. To avoid this, the USSR adopted and operates state standards of the Unified System of Design Documentation (ESKD).

ESKD standards are regulatory documents that establish uniform rules for the implementation and execution of design documents in all industries. Design documents include drawings of parts, assembly drawings, diagrams, some text documents, etc.

Standards are established not only for design documents, but also for certain types of products manufactured by our enterprises. State standards (GOST) are mandatory for all enterprises and individuals.

Each standard is assigned its own number along with the year of its registration.

The standards are revised from time to time. Changes in standards are associated with the development of industry and the improvement of engineering graphics.

For the first time in our country, standards for drawings were introduced in 1928 under the title “Drawings for all types of mechanical engineering.” Later they were replaced with new ones.

2.2. Formats. The main inscription of the drawing. Drawings and other design documents for industry and construction are performed on sheets of certain sizes.

For economical use of paper, ease of storage and use of drawings, the standard establishes certain sheet formats, which are outlined with a thin line. At school you will use a format whose sides measure 297X210 mm. It is designated A4.

Each drawing must have a frame that limits its field (Fig. 18). The frame lines are solid thick basic ones. They are carried out from above, to the right and below at a distance of 5 mm from the outer frame, made by a continuous thin line along which the sheets are cut. On the left side - at a distance of 20 mm from it. This strip is left for filing drawings.

Rice. 18. Design of A4 sheet

On the drawings, the main inscription is placed in the lower right corner (see Fig. 18). Its shape, size and content are established by the standard. On educational school drawings you will make the main inscription in the form of a rectangle with sides 22X145 mm (Fig. 19, a). A sample of the completed title block is shown in Figure 19, b.

Rice. 19. The main inscription of the educational drawing

Production drawings made on A4 sheets are placed only vertically, and the main inscription on them is only along the short side. On drawings of other formats, the title block can be placed along both the long and short sides.

As an exception, on educational drawings in A4 format, the main inscription is allowed to be placed both along the long and short sides of the sheet.

Before starting the drawing, the sheet is applied to the drawing board. To do this, attach it with one button, for example, in the upper left corner. Then a crossbar is placed on the board and the upper edge of the sheet is placed parallel to its edge, as shown in Figure 20. Pressing the sheet of paper to the board, attach it with buttons, first in the lower right corner, and then in the remaining corners.

Rice. 20. Preparing the sheet for work

The frame and columns of the main inscription are made with a solid thick line.

What are the dimensions of an A4 sheet? At what distance from the outer frame should the drawing frame lines be drawn? Where is the title block placed on the drawing? Name its dimensions. Look at Figure 19 and list what information it contains.

2.3. Lines. When making drawings, lines of various thicknesses and styles are used. Each of them has its own purpose.

Rice. 21. Drawing lines

Figure 21 shows an image of a part called a roller. As you can see, the part drawing contains different lines. In order for the image to be clear to everyone, the state standard establishes the outline of lines and indicates their main purpose for all industrial and construction drawings. In technical and maintenance lessons you have already used various lines. Let's remember them.

In conclusion, the thickness of lines of the same type should be the same for all images in a given drawing.

Information about the drawing lines is given on the first flyleaf.

1. What is the purpose of a solid thick main line?
2. Which line is called a dashed line? Where is it used? How thick is this line?
3. Where is the dash-dotted thin line used in the drawing? What is its thickness?
4. In what cases is a solid thin line used in a drawing? How thick should it be?
5. Which line shows the fold line on a development?

In Figure 23 you see an image of the part. Various lines are marked on it with numbers 1,2, etc. Make a table based on this example in your workbook and fill it out.

Rice. 23. Exercise task

Graphic work No. 1

Prepare a sheet of A4 drawing paper. Draw the frame and columns of the main inscription according to the dimensions indicated in Figure 19. Draw various lines, as shown in Figure 24. You can choose another arrangement of groups of lines on the sheet.

Rice. 24. Assignment for graphic work No. 1

The main inscription can be placed both along the short and along the long side of the sheet.

2.4. Drawing fonts. Sizes of letters and numbers of a drawing font. All inscriptions on the drawings must be made in drawing font (Fig. 25). The style of letters and numbers of a drawing font is established by the standard. The standard determines the height and width of letters and numbers, the thickness of stroke lines, the distance between letters, words and lines.

Rice. 25. Inscriptions on drawings

An example of constructing one of the letters in the auxiliary grid is shown in Figure 26.

Rice. 26. Example of letter construction

The font can be either slanted (about 75°) or without slanting.

The standard sets the following font sizes: 1.8 (not recommended, but allowed); 2.5; 3.5; 5; 7; 10; 14; 20; 28; 40. The size (h) of a font is taken to be the value determined by the height of capital letters in millimeters. The height of the letter is measured perpendicular to the base of the line. The lower elements of the letters D, Ts, Shch and the upper element of the letter Y are made due to the spaces between the lines.

The thickness (d) of the font line is determined depending on the height of the font. It is equal to 0.1h;. The width (g) of the letter is chosen to be 0.6h or 6d. The width of the letters A, D, Ж, М, ​​Ф, X, Ц, Ш, Ш, Ъ, ы, У is greater than this value by 1 or 2d (including the lower and upper elements), and the width of the letters Г, 3, С is less by d.

The height of lowercase letters is approximately the same as the height of the next smaller font size. So, the height of lowercase letters of size 10 is 7, size 7 is 5, etc. The upper and lower elements of lowercase letters are made due to the distances between the lines and extend beyond the line in 3d. Most lowercase letters are 5d wide. The width of the letters a, m, c, ъ is 6d, the letters zh, t, f, w, shch, s, yu are 7d, and the letters z, s are 4d.

The distance between letters and numbers in words is taken to be 0.2h or 2d, between words and numbers -0.6h or 6d. The distance between the lower lines of the lines is taken equal to 1.7h or 17d.

The standard also establishes another type of font - type A, narrower than the one just discussed.

The height of letters and numbers in pencil drawings must be at least 3.5 mm.

The layout of the Latin alphabet according to GOST is shown in Figure 27.

Rice. 27. Latin font

How to write in drawing font. It is necessary to draw up drawings with inscriptions carefully. Poorly written inscriptions or carelessly applied digits of different numbers may be misunderstood when reading the drawing.

To learn how to write beautifully in a drawing font, first draw a grid for each letter (Fig. 28). After mastering the skills of writing letters and numbers, you can only draw the top and bottom lines of the line.

Rice. 28. Examples of making inscriptions in drawing font

The outlines of the letters are outlined with thin lines. After making sure that the letters are written correctly, trace them with a soft pencil.

For the letters G, D, I, Ya, L, M, P, T, X, C, Ш, Ш, you can only draw two auxiliary lines at a distance equal to their height A.

For the letters B, V, E, N. R, U, CH, Ъ, И, ь. Between the two horizontal lines, another one should be added in the middle, but which is filled with their middle elements. And for the letters 3, O, F, Yu, four lines are drawn, where the middle lines indicate the boundaries of the roundings.

To quickly write inscriptions in a drawing font, various stencils are sometimes used. You will fill out the main inscription in 3.5 font, the title of the drawing in 7 or 5 font.

1. What is the font size?
2. What is the width of capital letters?
3. What is the height of size 14 lowercase letters? What is their width?

1. Complete several inscriptions in your workbook according to the teacher’s instructions. For example, you can write your last name, first name, and home address.
2. Fill in the main inscription on sheet of graphic work No. 1 with the following text: drew (last name), checked (teacher's last name), school, class, drawing No. 1, title of the work “Lines”.

2.5. How to apply dimensions. To determine the size of the depicted product or any part of it, dimensions are applied to the drawing. Dimensions are divided into linear and angular. Linear dimensions characterize the length, width, thickness, height, diameter or radius of the measured part of the product. Angular size characterizes the size of the angle.

Linear dimensions in the drawings are indicated in millimeters, but the unit of measurement is not indicated. Angular dimensions are indicated in degrees, minutes and seconds with the designation of the unit of measurement.

The total number of dimensions in the drawing should be the smallest, but sufficient for the manufacture and control of the product.

The rules for applying dimensions are established by the standard. You already know some of them. Let's remind them.

1. Dimensions in the drawings are indicated by dimensional numbers and dimensional lines. To do this, first draw extension lines perpendicular to the segment, the size of which is indicated (Fig. 29, a). Then, at a distance of at least 10 mm from the contour of the part, draw a dimension line parallel to it. The dimension line is limited on both sides by arrows. What the arrow should be is shown in Figure 29, b. Extension lines extend beyond the ends of the arrows of the dimension line by 1...5 mm. Extension and dimension lines are drawn as a solid thin line. Above the dimension line, closer to its middle, the dimension number is applied.

Rice. 29. Applying linear dimensions

2. If there are several dimension lines parallel to each other in the drawing, then a smaller dimension is applied closer to the image. So, in Figure 29, first dimension 5 is applied, and then 26, so that the extension and dimension lines in the drawing do not intersect. The distance between parallel dimension lines must be at least 7 mm.

3. To indicate the diameter, a special sign is applied in front of the size number - a circle crossed out by a line (Fig. 30). If the dimensional number does not fit inside the circle, it is taken outside the circle, as shown in Figure 30, c and d. The same is done when applying the size of a straight segment (see Figure 29, c).

Rice. 30. Sizing circles

4. To indicate the radius, write the capital Latin letter R in front of the dimension number (Fig. 31, a). The dimension line to indicate the radius is drawn, as a rule, from the center of the arc and ends with an arrow on one side, abutting the point of the arc of the circle.

Rice. 31. Applying dimensions of arcs and angles

5. When indicating the size of an angle, the dimension line is drawn in the form of a circular arc with the center at the vertex of the angle (Fig. 31, b).

6. Before the dimensional number indicating the side of the square element, a “square” sign is applied (Fig. 32). In this case, the height of the sign is equal to the height of the numbers.

Rice. 32. Applying the size of the square

7. If the dimension line is located vertically or obliquely, then the dimension numbers are placed as shown in Figure 29, c; thirty; 31.

8. If a part has several identical elements, then it is recommended to indicate on the drawing the size of only one of them with an indication of the quantity. For example, an entry on the drawing “3 holes. 0 10" means that the part has three identical holes with a diameter of 10 mm.

9. When depicting flat parts in one projection, the thickness of the part is indicated as shown in Figure 29, c. Please note that the dimensional number indicating the thickness of the part is preceded by the Latin small letter 5.

10. It is allowed to indicate the length of the part in a similar way (Fig. 33), but in this case a Latin letter is written before the dimension number l.

Rice. 33. Applying the part length dimension

1. In what units are linear dimensions expressed in mechanical engineering drawings?
2. How thick should extension and dimension lines be?
3. What distance is left between the outline of the image and the dimension lines? between size lines?
4. How are dimensional numbers applied on inclined dimensional lines?
5. What signs and letters are placed before the dimensional number when indicating the values ​​of diameters and radii?

Rice. 34. Exercise task

1. Draw into your workbook, maintaining the proportions, the image of the part given in Figure 34, enlarging it by 2 times. Apply the required dimensions, indicate the thickness of the part (it is 4 mm).
2. Draw circles in your workbook with diameters of 40, 30, 20 and 10 mm. Add their dimensions. Draw circular arcs with radii of 40, 30, 20 and 10 mm and mark the dimensions.

2.6. Scale. In practice, it is necessary to create images of very large parts, for example parts of an airplane, ship, car, and very small ones - parts of a clock mechanism, some instruments, etc. Images of large parts may not fit on sheets of standard format. Small details that are barely visible to the naked eye cannot be drawn in full size using existing drawing tools. Therefore, when drawing large parts, their image is reduced, and small ones are increased in comparison with the actual dimensions.

Scale is the ratio of the linear dimensions of the image of an object to the actual ones. The scale of images and their designation on drawings sets the standard.

Reduction scale - 1:2; 1:2.5; 1:4; 1:5; 1:10, etc.
Natural size - 1:1.
Magnification scale - 2:1; 2.5:1; 4:1; 5:1; 10:1, etc.

The most desirable scale is 1:1. In this case, when creating an image, there is no need to recalculate the dimensions.

The scales are written as follows: M1:1; M1:2; M5:1, etc. If the scale is indicated on the drawing in a specially designated column of the main inscription, then the letter M is not written before the scale designation.

It should be remembered that, no matter what scale the image is made, the dimensions on the drawing are actual, i.e. those that the part should have in kind (Fig. 35).

The angular dimensions do not change when the image is reduced or enlarged.

1. What is the scale used for?
2. What is scale?
3. What are the magnification scales established by the standard? What scale of reduction do you know?
4. What do the entries mean: M1:5; M1:1; M10:1?

Rice. 35. Drawing of the gasket, made in various scales

Graphic work No. 2
Flat part drawing

Make drawings of the “Gasket” parts using the existing halves of the images, separated by an axis of symmetry (Fig. 36). Add dimensions, indicate the thickness of the part (5 mm).

Complete the work on an A4 sheet. Image scale 2:1.

Directions for use. Figure 36 shows only half of the image of the part. You need to imagine what the complete part will look like, keeping in mind symmetry, and sketch it on a separate sheet. Then you should proceed to the drawing.

A frame is drawn on an A4 sheet and space is allocated for the main inscription (22X145 mm). The center of the working field of the drawing is determined and the image is constructed from it.

First, draw the axes of symmetry and build a rectangle with thin lines that corresponds to the general shape of the part. After this, images of the rectangular elements of the part are marked.

Rice. 36. Tasks for graphic work No. 2

Having determined the position of the centers of the circle and semicircle, draw them. The dimensions of the elements and overall, i.e., the largest in length and height, dimensions of the part are indicated, and its thickness is indicated.

Outline the drawing with the lines established by the standard: first - circles, then - horizontal and vertical straight lines. Fill out the title block and check the drawing.

The course examines the sequence of performing some exercises from the textbook "Drawing" edited by A.D. Botvinnikova.

Stages of completing graphic work No. 4 of the first and second tasks, Fig. 98 and 99.

These types of exercises help develop spatial thinking. Graphic work No. 4 is a summary, generalization and consolidation of the skills acquired in the process of studying the topics “Vertexes, edges and faces of an object”, “Analysis of the geometric shape of an object”. Quality control of knowledge, skills and abilities acquired during practical exercises to determine the projections of a point on the surface of an object shown in a drawing and visual image.

This type of activity can be used both in technology and drawing lessons. Similar tasks can be assigned at home as independent work.

Requirements for the trainee

This course is designed for students in the 7th grade of a general education school; it can also be useful for students of technical specialties, for the simple reason that it contains elements of descriptive geometry. It also trains spatial imagination.

Necessary requirements for trainees: knowledge of the rules of orthogonal projection; oblique parallel projection.

The student must be able to: analyze the geometric shapes of an object; determine projections of edges, faces, vertices of an object; determine projections of points on the surface of an object; build an image along the axes of isometric and frontal dimetric projection of ribs, faces, ovals.