What does the section on the drawing show? Images - views, sections, sections. Reading Section Drawings
Date of introduction 01.01.71
This standard establishes the rules for depicting objects (products, structures and their constituent elements) on drawings of all industries and construction. The standard fully complies with ST SEV 363-88. (Changed edition, Amendment No. 2).
1. BASIC PROVISIONS AND DEFINITIONS
1.1. Images of objects should be made using the rectangular projection method. In this case, the object is assumed to be located between the observer and the corresponding projection plane (Fig. 1).1.2. The six faces of the cube are taken as the main projection planes; the edges are combined with the plane, as shown in Fig. 2. Face 6 may be placed next to face 4. 1.3 The image on the frontal plane of projections is taken as the main one in the drawing. The object is positioned relative to the frontal plane of projections so that the image on it gives the most complete idea of the shape and size of the object. 1.4. The images in the drawing, depending on their content, are divided into types, sections, sections.
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1.5. View - an image of the visible part of the surface of an object facing the observer. To reduce the number of images, it is allowed to show the necessary invisible parts of the surface of an object in views using dashed lines (Fig. 3).
1.6 Section - an image of an object mentally dissected by one or more planes, while the mental dissection of an object relates only to this section and does not entail changes in other images of the same object. The section shows what is obtained in the secant plane and what is located behind it (Fig. 4). It is allowed to depict not everything that is located behind the cutting plane, if this is not required to understand the design of the object (Fig. 5).
1.7. Section - an image of a figure obtained by mentally dissecting an object with one or more planes (Fig. 6). The section shows only what is obtained directly in the cutting plane. It is allowed to use a cylindrical surface as a secant, which is then developed into a plane (Fig. 7).
(Changed edition, Amendment No. 2). 1.8. The number of images (types, sections, sections) should be the smallest, but providing a complete picture of the subject when using the symbols, signs and inscriptions established in the relevant standards.
2. TYPES
2.1. The following names of views obtained on the main projection planes are established (main views, drawing 2): 1 - front view (main view); 2 - top view; 3 - left view; 4 - right view; 5 - bottom view; 6 - rear view. In construction drawings, if necessary, the corresponding views may be given other names, for example, “facade”. The names of types should not be inscribed on the drawings, except as provided in clause 2.2. In construction drawings it is allowed to inscribe the name of the type and assign it an alphabetic, numerical or other designation. 2.2. If the views from above, left, right, below, behind are not in direct projection connection with the main image (the view or section shown on the frontal plane of projections), then the direction of projection should be indicated by an arrow next to the corresponding image. The same capital letter should be placed above the arrow and above the resulting image (view) (Fig. 8).
Drawings are designed in the same way if the listed views are separated from the main image by other images or are not located on the same sheet with it. When there is no image that can show the direction of view, the name of the species is inscribed. In construction drawings, it is allowed to indicate the direction of view with two arrows (similar to indicating the position of cutting planes in sections). In construction drawings, regardless of the relative position of the views, it is allowed to inscribe the name and designation of the view without indicating the direction of view with an arrow, if the direction of view is determined by the name or designation of the view. 2.3. If any part of an object cannot be shown in the views listed in paragraph 2.1 without distorting the shape and size, then additional views are used, obtained on planes not parallel to the main planes of projections (Fig. 9-11). 2.4. The additional view must be marked on the drawing with a capital letter (Drawings 9, 10), and the image of an object associated with the additional view must have an arrow indicating the direction of view, with a corresponding letter designation (arrow B, Drawings 9, 10).
When an additional view is located in direct projection connection with the corresponding image, the arrow and view designation are not applied (Fig. 11).
2.2-2.4. (Changed edition, Amendment No. 2). 2.5. Additional types are arranged as shown in Fig. 9- 11. Location of additional views along the lines. 9 and 11 are preferable. An additional view can be rotated, but with, as a rule, maintaining the position adopted for a given item in the main image, and the designation of the view must be supplemented with a conventional graphic designation. If necessary, indicate the angle of rotation (Fig. 12). Several identical additional types related to one subject are designated by one letter and one type is drawn. If, in this case, parts of the object associated with an additional type are located at different angles, then a conventional graphic designation is not added to the type designation. (Changed edition, Amendment No. 1, 2). 2.6. The image of a separate, limited area of the surface of an object is called a local view (type D, figure 8; view E, figure 13). Local view may be limited by the break line, if possible in smallest size(type D, drawing 13), or not limited (type D, drawing 13). The local view should be marked on the drawing as additional view. 2.7. The ratio of the sizes of the arrows indicating the direction of view must correspond to those shown in Fig. 14. 2.6, 2.7. (Changed edition, Amendment No. 2).
3. CUT
3.1. The cuts are divided depending on the position of the cutting plane relative to horizontal plane projections onto: horizontal - the cutting plane is parallel to the horizontal plane of projections (for example, section A-A, drawing 13; section B-B, crap. 15). In construction drawings, horizontal sections may be given other names, such as "plan"; vertical - the cutting plane is perpendicular to the horizontal plane of projections (for example, a section at the site of the main view, Fig. 13; cuts A-A, V-V, G-G, damn. 15); inclined - the secant plane makes an angle with the horizontal projection plane that is different from a straight line (for example, section B-B, crap. 8). Depending on the number of cutting planes, the sections are divided into: simple - with one cutting plane (for example, Fig. 4, 5); complex - with several cutting planes (for example, section A-A, Fig. 8; section B-B, Fig. 15). 3.2. A vertical section is called frontal if the cutting plane is parallel to the frontal plane of projections (for example, section, Fig. 5; section A-A, Fig. 16), and profile if the cutting plane is parallel to the profile plane of projections (for example, section BB, Fig. 16 .13).
3.3. Complex sections can be stepped if the cutting planes are parallel (for example, a stepped horizontal section B-B, Fig. 15; a stepped frontal section A-A, Fig. 16), and broken if the cutting planes intersect (for example, sections A-A, features 8 and 15). 3.4. The cuts are called longitudinal if the cutting planes are directed along the length or height of the object (Figure 17), and transverse if the cutting planes are directed perpendicular to the length or height of the object (for example, cuts A-A and B-B, Figure 18). 3.5. The position of the cutting plane is indicated in the drawing by a section line. An open line must be used for the section line. In case of a complex cut, strokes are also made at the intersection of the cutting planes. Arrows should be placed on the initial and final strokes indicating the direction of view (Fig. 8-10, 13, 15); arrows should be applied at a distance of 2-3 mm from the end of the stroke. The starting and ending strokes must not intersect the outline of the corresponding image. In cases like the one indicated in Fig. 18, arrows indicating the direction of view are drawn on the same line. 3.1-3.5. (Changed edition, Amendment No. 2). 3.6. At the beginning and end of the section line, and, if necessary, at the intersection of cutting planes, the same capital letter of the Russian alphabet is placed. The letters are placed near the arrows indicating the direction of view, and at the intersection points from the side external corner. The cut must be marked with an inscription like “A-A” (always two letters separated by a dash). In construction drawings, near the section line, it is allowed to use numbers instead of letters, as well as inscribe the name of the section (plan) with an alphanumeric or other designation assigned to it. 3.7. When the secant plane coincides with the plane of symmetry of the object as a whole, and the corresponding images are located on the same sheet in direct projection connection and are not separated by any other images, for horizontal, frontal and profile sections the position of the secant plane is not marked, and the cut is inscribed are not accompanied (for example, a section at the site of the main species, Fig. 13). 3.8. Frontal and profile sections, as a rule, are given a position corresponding to that accepted for a given item in the main image of the drawing (Fig. 12). 3.9. Horizontal, frontal and profile sections can be located in place of the corresponding main views (Fig. 13). 3.10. A vertical section, when the cutting plane is not parallel to the frontal or profile planes of projections, as well as an inclined section must be constructed and located in accordance with the direction indicated by the arrows on the section line. It is allowed to place such sections anywhere in the drawing (section B-B, Fig. 8), as well as with rotation to the position corresponding to that accepted for this item in the main image. In the latter case, a conventional graphic designation should be added to the inscription (section Г-Г, drawing 15). 3.11. For broken cuts, the secant planes are conventionally rotated until they are aligned into one plane, and the direction of rotation may not coincide with the direction of view (Fig. 19). If the combined planes turn out to be parallel to one of the main projection planes, then a broken section can be placed in the place of the corresponding type (sections A-A, drawings 8, 15). When rotating the secant plane, the elements of the object located on it are drawn as they are projected onto the corresponding plane with which the alignment is made (Fig. 20).
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3.12. An incision that serves to clarify the structure of an object only in a separate, limited place is called local. The local section is highlighted in the view by a solid wavy line (Figure 21) or a solid thin line with a break (Figure 22). These lines must not coincide with any other lines in the image.
3.13. Part of the view and part of the corresponding section can be connected by separating them with a solid wavy line or a solid thin line with a break (Fig. 23, 24, 25). If in this case half of the view and half of the section are connected, each of which is a symmetrical figure, then the dividing line is the axis of symmetry (Fig. 26). It is also possible to separate the section and view by a thin dash-dotted line (Fig. 27), coinciding with the trace of the plane of symmetry not of the entire object, but only of its part, if it represents a body of rotation.
3.10-3.13. (Changed edition, Rev. № 2). 3.14. It is allowed to combine a quarter of a view and quarters of three sections: a quarter of a view, a quarter of one section and half of another, etc., provided that each of these images is individually symmetrical.
4. SECTIONS
4.1. Sections that are not part of the section are divided into: external sections (Fig. 6, 28); superimposed (Fig. 29).
Extended sections are preferable and can be placed in a section between parts of the same type (Fig. 30).
(Changed edition, Amendment No. 2). 4.2. The contour of the extended section, as well as the section included in the section, is depicted with solid main lines, and the contour of the superimposed section is depicted with solid thin lines, and the contour of the image at the location of the superimposed section is not interrupted (Fig. 13, 28, 29). 4.3. The axis of symmetry of the extended or superimposed section (Fig. 6, 29) is indicated by a thin dash-dotted line without letters and arrows, and the section line is not drawn. In cases like the one indicated in Fig. 30, with a symmetrical sectional figure, the section line is not drawn. In all other cases, an open line is used for the section line, indicating the direction of view with arrows and denoted by the same capital letters of the Russian alphabet (in construction drawings - uppercase or lowercase letters of the Russian alphabet or numbers). The section is accompanied by an inscription like “AA” (Fig. 28). In construction drawings it is allowed to inscribe the name of the section. For asymmetrical sections located in a gap (Fig. 31) or superimposed (Fig. 32), the section line is drawn with arrows, but not marked with letters.
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In construction drawings, for symmetrical sections, an open line is used with its designation, but without arrows indicating the direction of view. 4.4. The section in construction and location must correspond to the direction indicated by the arrows (Fig. 28). It is allowed to place the section anywhere in the drawing field, as well as with a rotation with the addition of a conventional graphic designation 4.5. For several identical sections related to one object, the section line is designated by one letter and one section is drawn (Fig. 33, 34). If the cutting planes are directed at different angles (Fig. 35), then the conventional graphic designation is not applied. When the location of identical sections is precisely determined by the image or dimensions, it is allowed to draw one section line, and indicate the number of sections above the section image.
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4.6 Cutting planes are chosen so as to obtain normal cross sections (Fig. 36). 4.7. If the secant plane passes through the axis of the surface of rotation that bounds the hole or recess, then the contour of the hole or recess in the section is shown in full (Fig. 37). 4.8. If the section turns out to consist of separate independent parts, then cuts should be used (Fig. 38).
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4.4-4.8. (Changed edition, Amendment No. 2).
5. REMOTE ELEMENTS
5.1. A detachable element is an additional separate image (usually enlarged) of any part of an object that requires graphic and other explanations regarding shape, size and other data. The detail element may contain details not indicated on the corresponding image, and may differ from it in content (for example, the image may be a view, and the detail element may be a section). 5.2. When using a callout element, the corresponding place is marked on the view, section or section with a closed solid thin line - a circle, an oval, etc. with the designation of the callout element in a capital letter or a combination of a capital letter and an Arabic numeral on the shelf of the leader line. Above the image of the extension element, indicate the designation and scale in which it is made (Fig. 39).
In construction drawings, the extension element in the image can also be marked with a curly or square bracket or not marked graphically. On the image from which the element is being taken out, and on the callout element, it is also allowed to apply the alphabetic or numeric number assigned to the callout element ( Arabic numerals) designation and name. (Changed edition, Amendment No. 2). 5.3. The remote element is placed as close as possible to the corresponding place in the image of the object.
6. CONVENTIONS AND SIMPLIFICATIONS
6.1. If the view, section or section represents a symmetrical figure, it is allowed to draw half of the image (View B, Drawing 13) or slightly more than half of the image, drawing a break line in the latter case (Drawing 25). 6.2. If an object has several identical, evenly spaced elements, then the image of this object shows one or two such elements in full (for example, one or two holes, Fig. 15), and the remaining elements are shown in a simplified or conditional manner (Fig. 40). It is allowed to depict a part of an object (Fig. 41, 42) with appropriate instructions on the number of elements, their location, etc.
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6.3. In views and sections, it is allowed to depict in a simplified manner the projections of the lines of intersection of surfaces, if their precise construction is not required. For example, instead of pattern curves, circular arcs and straight lines are drawn (Fig. 43, 44).
6.4. A smooth transition from one surface to another is shown conditionally (Fig. 45-47) or not shown at all (Fig. 48-50).
Simplifications similar to those indicated in Fig. 51, 52.
6.5. Parts such as screws, rivets, keys, non-hollow shafts and spindles, connecting rods, handles, etc. are shown uncut in a longitudinal section. The balls are always shown uncut. As a rule, nuts and washers are shown uncut on assembly drawings. Elements such as spokes of flywheels, pulleys, gears, thin walls such as stiffeners, etc. are shown unshaded if the cutting plane is directed along the axis or long side of such an element. If in such elements of a part there is a local drilling, recess, etc., then a local cut is made, as shown in Fig. 21, 22, 53. (Changed edition, Amendment No. 2).
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6.6. Plates, as well as elements of parts (holes, chamfers, grooves, recesses, etc.) with a size (or difference in size) in the drawing of 2 mm or less are depicted with a deviation from the scale adopted for the entire image, in the direction of enlargement. 6.7. It is permissible to depict a slight taper or slope with magnification. In those images in which the slope or taper is not clearly visible, for example, the main view of the devil. 54a or top view of the devil. 54b, draw only one line corresponding to the smaller size of the element with a slope or the smaller base of the cone. 6.8. If it is necessary to highlight the flat surfaces of an object in the drawing, diagonals are drawn on them with solid thin lines (Drawing 55). 6.9. Objects or elements that have a constant or naturally changing cross section(shafts, chains, rods, shaped steel, connecting rods, etc.), may be depicted with breaks. Partial images and images with breaks are limited in one of the following ways: a) a continuous thin line with a break, which can extend beyond the contour of the image by a length of 2 to 4 mm. This line may be inclined relative to the contour line (Fig. 56a);
B) a solid wavy line connecting the corresponding contour lines (Fig. 56b);
C) hatching lines (Fig. 5bv).
(Changed edition, Rev. № 2). 6.10. In drawings of objects with a continuous mesh, braiding, ornament, relief, knurling, etc., it is allowed to depict these elements partially, with possible simplification (Drawing 57).
6.11. To simplify drawings or reduce the number of images, it is allowed: a) the part of the object located between the observer and the cutting plane is depicted with a dash-dot thick line directly on the section (superimposed projection, Fig. 58); b) use complex cuts (Fig. 59);
C) to show holes in the hubs of gear wheels, pulleys, etc., as well as for keyways, instead of a full image of the part, give only the outline of the hole (Fig. 60) or groove (Fig. 52); d) depict in section the holes located on the round flange when they do not fall into the secant plane (Fig. 15). 6.12. If a top view is not necessary and the drawing is compiled from images on the frontal and profile planes of projections, then with a stepped section, the section line and inscriptions related to the section are applied as shown in the drawing. 61.
6.11, 6.12. (Changed edition, Amendment No. 2). 6.13. Conventions and simplifications allowed in permanent connections, in drawings of electrical and radio engineering devices, gears, etc., are established by the relevant standards. 6.14. The conventional graphic designation “rotated” must correspond to the line. 62 and “expanded” - damn. 63.
(Introduced additionally, Amendment No. 2). APPENDIX according to GOST 2.317-69.
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Committee of Standards, Measures and Measuring Instruments under the Council of Ministers of the USSR DEVELOPERS V.R. Verchenko, Yu.I. Stepanov, Ya.G. Old-timer, B.Ya. Kabakov, V.K. Anopova 2. APPROVED AND ENTERED INTO EFFECT by the Resolution of the Committee of Standards, Measures and measuring instruments at the Council of Ministers of the USSR in December 1967 3. The standard fully complies with ST SEV 363-88 4. INSTEAD GOST 3453-59 in terms of section. I - V, VII and appendices 5. EDITION (April 2000) with Amendments No. 1, 2, approved in September 1987, August 1989 (IUS 12-87, 12-89)
| 1. Basic provisions and definitions. 1 2. Types.. 3 3. Sections.. 6 4. Sections. 9 5. Detailed elements.. 11 6. Conventions and simplifications. 12 |
In previous chapters we talked about images called views. However, the shape of many details is not revealed with sufficient completeness by views-images of the visible surface of the object facing the observer, therefore, in drawing, images such as sections and sections are also used.
The shape of the handle of the pliers (Fig. 186) cannot be determined from a drawing containing only views. To identify the transverse shape of the handle, which is curved, it is necessary to apply sections.
Section they call the image of a figure obtained by mentally dissecting an object with one or more planes (see Fig. 188). The section shows only what is in the cutting plane.
Cutting plane called the auxiliary plane, which is used to mentally dissect the part.
Sections are used mainly to show the transverse shape of an object.
Construction of sections. To reveal the transverse shape of the shaft (Fig. 187, a), it is mentally dissected by three cutting planes A, B and C. Flat figures are formed (Fig. 187, b): on the first, the shape of the part is revealed in the place where the flat is removed and drilled blind hole; the second shows the transverse shape and dimensions of the keyway; on the third - the location and depth of the three holes. By constructing these figures on the drawing, a section is obtained (Fig. 188).
The sections show only what is in the cutting plane itself; what is located behind the cutting plane is not shown. The sectional figure in the drawing is highlighted by shading in order to distinguish mentally formed surfaces on the part from existing ones. Hatching is applied with thin lines. Oblique parallel lines hatching is carried out at an angle of 45 to the lines of the drawing frame. The distance between the lines should be 1-10 mm (for metal) (Fig. 189, b) and the same for all sections of one part in a given drawing. The tilt of the hatching is allowed both to the left and to the right (Fig. 189, a).
More details about shading are discussed in § 33.
According to their location, sections are divided into extended and superimposed.
Sent called sections located outside the contour of the images of the part (see Fig. 188).
Superimposed called sections located directly on the drawing views (Fig. 190, a).
The contour of the extended section is outlined with a solid thick main line of the same thickness (s) as the line chosen to outline the visible contour of the image.
The contour of the superimposed section is outlined with a solid thin line (from s/2 to s/3). If the section closes contour lines kind, then they are not interrupted.
The extended section can be placed anywhere in the drawing field. It can be placed directly on the continuation of the section line (Fig. 190, b) or away from this line, in particular in the place intended for one of the views (Fig. 190, c), as well as in the gap between parts of the view (Fig. . 190, g).
Exposed sections should be given preference over superimposed ones, since the latter obscure the views of the drawing and are inconvenient for drawing dimensions.
Designation of sections. To determine where the part has the shape shown in the section, the place where the cutting plane is located and the section itself are designated.
The position of the cutting plane is indicated in the drawing by a section line. The axis of symmetry of the superimposed or extended section is indicated by a thin dash-dot line without letters or arrows, and the section line is not drawn (Fig. 190, a and b, 191, b). In all other cases, an open line is used for the section line (Fig. 191, a-f), the initial and final strokes of which should not intersect the contour of the corresponding image. The thickness of the strokes of an open line is taken from s to 1.5s, and the length from 8 to 20 mm. On the initial and final strokes, perpendicular to them, at a distance of 2-3 mm from the end of the stroke, arrows are placed indicating the direction of view. The shape, size ratio of the arrows and the relative position of the arrows and the open line are shown in Fig. 192.
The same capital letter of the Russian alphabet is placed at the beginning and end of the section line; in this case, the initial letters are chosen - A, B, C, D, D, etc. The letters are applied on the outside of the arrows indicating the direction of view (see Fig. 191, a and c). An inscription is made above the section according to type A-A, i.e. the section is denoted by two identical letters separated by a dash with a thin line at the bottom.
For asymmetrical sections located in a break in the view (see Fig. 191, e) or superimposed (see Fig. 191, f), the section line is drawn with arrows, but it is not marked with letters.
If the section is in a gap between parts of the same section, the section line is not drawn (see Fig. 190, d).
For several identical sections related to the same object, the section line is marked with the same letter and one section is drawn (Fig. 193).
Rules for making sections. The section in construction and location must correspond to the direction indicated by the arrows (see Fig. 188, 190, c and 191, a). In Fig. 194 shows how the sectional figure is aligned with the drawing plane. Therefore, in Fig. 190, in the keyway located on the front of the part is shown in the section on the right. The section in Fig. is also combined with the drawing plane. 191, d. Why in section A-A (see Fig. 191, a) the keyway is located on top, and on section B-B- from below? Check your answer against the answer given at the end of the book.
It is allowed to rotate the section relative to the section line. In this case, after the designation the word is added "rotated"(see Fig. 191, c).
If the cutting plane passes through the axis of the surface of rotation that bounds the hole or recess, then the contour of the hole or recess in the section is shown in full (Fig. 195). It should be noted that this applies to cylindrical, conical and spherical recesses and does not apply to other sections, such as keyway sections.
If the cutting plane passes through a non-circular hole and the section turns out to consist of separate independent parts, then cuts should be used. They will be discussed below.
For parts similar to those shown in Fig. 191, d, the cutting planes are placed at right angles to the depicted elements and normal sections are obtained that correctly convey the shape of the object.
Dimensions are usually indicated on sections, surface roughness is indicated, etc.
For example, the section of the roller (Fig. 196) shows the width and depth of the keyway, maximum deviations sizes, surface roughness.
Answer the questions
1. What image is called a section?
2. For. what are sections used for?
3. How are sections divided depending on their location in the drawing?
4. What thickness of lines are used to outline the contour of the superimposed and extended section?
5. How and why are sections hatched?
6. Do the sections show what is located behind the cutting plane?
7. In what cases is the section accompanied by an inscription? What letters are used for this?
8. How is a section line drawn? What is the outline of an open line?
9. How is the contour of a hole shown in a section if the cutting plane passes through the axis of a body of rotation?
10. How are several identical sections related to one object designated?
11. Where in relation to the designation of the section is the word “rotated” written when performing a section with a rotation?
Tasks for § 26
Exercise 86
Redraw the figure. 190, a-c and give written explanations to it, in which you state the following: what sections are, why they are used, how they are hatched, what types of sections there are, what line is used to outline their outline, when and how the sections are designated. Above the outline write the heading “Sections”.
Exercise 87
Determine and write down in your notebook in which cases the superimposed sections were applied successfully, and in which cases it would be better to give extended sections (Fig. 197).
Exercise 88
Two types of parts are given (Fig. 198). Instead of the left view, you need to do section А-А. Four sections are given, which are answer options. Write down the number of the correct answer in your workbook. Point out what is wrong with the other answers.
Exercise 89
Write down in your notebook which sections are aligned with the drawing plane correctly in accordance with the viewing direction indicated by the arrows (Fig. 199).
Exercise 90
In Fig. 200, a-d positions sections of cutting planes and sections are not marked. Write down in your notebook in which cases you need to indicate the position of the cutting planes, the direction of view and give inscriptions above the sections. Place on rice. 200 transparent paper and mark on it, where necessary, the designation of sections in accordance with the standard.
Exercise 91
Drawing in Fig. 201 is made irrationally, since the symmetrical section is located away from the section line. Draw a drawing in your notebook so that the section is located rationally. What will change?
Exercise 92
Write down in your notebook the numbers of sections performed correctly (Fig. 202). Indicate what is incorrect in other sections.
Exercise 93
Write down in your notebook which of the sections (Fig. 203) corresponds to the direction of view, the shape of the object, and the rules for making sections.
Manufacturing drawings contain various types images - views, sections and sections. We have already met with the drawing...
Sections and cuts allow us to identify the external and internal shape of the part (Fig. 1, a, b). These images are obtained as a result of mental dissection of a part with a cutting plane, the position of which is chosen depending on the shape of the part being depicted.
Rice. 1. Section (a) and section (b)
Sections and cuts complement and clarify geometric information about an object and thereby increase the possibility of identifying the shape of the depicted object in the drawing. In some cases, they have greater information capacity than species. Sections and sections are projection images and are performed according to the rules of rectangular projection.
Section — image of a figure resulting from mental dissection of an object with a secant plane.
Section formation
The part is mentally dissected with a cutting plane in the place where it is necessary to clarify the shape of the product. A sectional figure is obtained in the cutting plane (Fig. 2).
Rice. 2. Formation of a section
Section image
After this, the cutting plane (together with the section figure) is mentally removed, rotated around the vertical axis, moved parallel to the projection plane and combined with the frontal plane so that the images of the front view and the section figure do not obscure each other. The section shows only what is in the cutting plane.
Location of sections
Depending on their location in the drawing, sections are divided into:
A) issued when sections are placed anywhere in the drawing;
b) superimposed , when they are placed directly on the view of the object;
IN) in the gap - placed in the image gap.
The extended and superimposed section is shown in Fig. 3.
Fig.3. Construction of sections
Issuedthe section can be performed in two ways:
1. if the front view is in projection connection with the section, then the resulting image of the section figure is called a section made in projection connection(Fig. 4).
Rice. 4.Section made in projection connection.
2. the cutting plane with the section figure can be moved in any direction, combining it with the projection plane, without taking into account the projection connection. Such a section is called a section made in the free space of the drawing(Fig. 5).
Rice. 5.Section made in the free space of the drawing.
Designation of sections
Establishes rules for depicting and designating sections.
At taken out section the position of the cutting plane is indicated in the drawing by a section line - open line, which is carried out in the form of separate strokes that do not intersect the contour of the corresponding image. The thickness of the strokes is taken in the range from S to 1.5 S, and their length from 8 to 20 mm. On the initial and final strokes, perpendicular to them, at a distance of 2-3 mm from the end of the stroke, place arrows, indicating the direction of view (Fig. 6).
Rice. 6. The relative position of the open line strokes and arrows
The same capital letter is placed at the beginning and end of the section line letter of the Russian alphabet. Letter designations are assigned in alphabetical order without repetitions and without gaps, with the exception of the letters I, O, X, Ъ, ы, ь(Fig. 4). If several sections are required to identify the shape of parts, then several open lines are drawn, which in the drawing continue to be designated by the following letters of the Russian alphabet (B, V, D, etc.) (Fig. 7).
Rice. 7. Designation of several sections
The contour of the extended section is outlined by a solid main line of the same thickness S as the visible contour of the image. The sectional figure in the drawing is highlighted hatching, according to (graphic symbol). Dashed lines are applied in accordance with the general ones (mostly thin lines at an angle of 45° to the main inscription, in any direction after 2-3 mm). The same letters are written above the section with a dash (type A - A).
If the section is a symmetrical figure and is located on the continuation of the section line (dash-dotted), then the arrow and letters do not apply(see Fig. 5).
Superimposed called a section that is placed directly on the view of the object in the place where the cutting plane passed, that is, as if superimposed on the image. The superimposed section is performed when. The contour of the superimposed section is outlined with a solid thin line (from S/3 to S/2). The section figure is placed in the place of the main view where the cutting plane passes and is shaded.
The superimposed section also comes in two types:
1. if the superimposed section symmetrically relative to the cutting plane, then only the axis is indicated on the section by a dash-dotted line without letters and arrows (Fig. 8, a).
2. if the superimposed section is asymmetrical figure, then draw an open line indicating the direction of view with arrows, but do not indicate it with letters (Fig. 8, b).
Rice. 8. Superimposed section: a) symmetrical; b) asymmetrical.
If the section is in the gap between parts of the same type, then it is made with a solid main line (Fig. 9). The rules for designating sections located in a gap are similar to the rules for designating superimposed sections: for symmetrical sections only the axis is indicated (Fig. 9, a), and asymmetric sections are accompanied by an indication of an open line and arrows indicating the direction of view (Fig. 9, b).
Rice. 9. Sections in the gap: a) symmetrical; b) asymmetrical
Execution Features
When performing sections, the following conventions apply:
1. The sections taken out should be given preference before superimposed, since the latter darken the drawing and are inconvenient for drawing dimensions.
2. When a cutting plane passes through axis of rotation , limiting the hole or recess, the contour of the hole or recess is shown in full in cross-section (Fig. 10).
Rice. 10. Section passing through the axes of surfaces of revolution
3. If the cutting plane passes through prismatic through hole and the section figure breaks up into several parts, the section is not executed (Fig. 11).
Rice. 11. Section passing through a prismatic through hole.
4. Section, disintegrating into separate parts , replaced with a cut (Fig. 12).
Rice. 12. Replacing a section with a cut
5. Sections with a contour line at an angle of 45° hatched at an angle 30°or 60° (Fig. 13).
Rice. 13. Hatching at an angle of 60°.
6. For several identical sections , relating to one object, the section line is denoted by the same letters and one section is drawn (Fig. 14).
Rice. 14. Making several identical sections
7. The section can be positioned with a turn, then the rotated symbol must be added to the inscription A - A, that is, A - A. If the cutting planes of several identical sections not parallel each other, then the icon is not applied.
You have already encountered sections when making cuts. That part of the section that is shaded is the section included in the section. However, the section often has an independent meaning. Figure 8.10 shows a file. More from working hours in school workshops you have heard the phrase: file t recangular section. Indeed, the shape of a file is primarily characterized by the flat figure (a) that is obtained by mentally cutting the file transversely. This figure tells us more simply and clearly about the shape of the object than its view on the left (b).
So, a section is a flat figure obtained by mentally dissecting an object with a plane.
Rice. 8.10
Depending on the location, the section can be extended or superimposed.
An extended section is a section located outside the contour of other images of an object (Fig. 8.11a), and a superimposed section is a section located directly on one of the views of an object (Fig. 8.116).
Since the extended section can be located anywhere in the drawing field, one hundred is designated by the type of cuts. Naturally, the thickness of the outline of the section figure in this case is the value s (thickness of the line of the visible contour). On the contrary, the superimposed section is outlined a thin line, because otherwise his figure will “argue” with the view. No special designation is required, since the section is directly combined with the view.
Let's turn to Fig. 8.1 !c. The object depicted on it consists of cylindrical and prismatic parts. The cylinder shape is indicated by the sign 0, and the prism shape by the sign ?. Additionally, the prism is highlighted with thin transverse lines. The cylindrical part of the object is mentally dissected by planes in three characteristic places. Let's look at the resulting images.
Image A-A is a section, the outline of which consists of a circle with a segment cut off at the top. It is natural that
the diameter of the circle is equal to the diameter of the cylinder, however, this warning is not superfluous: the majority of errors in constructing sections are associated precisely with these dimensional discrepancies.
If we strictly follow the definition of a section, image B-B should have consisted of two separate segments, but GOST does not allow the construction of sections, the figure of which breaks into parts. In this regard, in such cases, the following rule is followed:
if the cutting plane passes through the axis of the surface of rotation that bounds the hole or recess, then the contour of the hole or recess in the section is shown in full.
The resulting image can no longer be a section in its “pure form.” It is more correct to consider it an incomplete section or a section constructed according to the type of section.
Finally, image B-B, the rule formulated above does not fall within iodine (since the secant plane passes through the prismatic window), there is an ordinary section.
In Figure 8.11d, the extended section is built on the continuation of the trace of the cutting plane and therefore does not need to be designated. Such a section cannot be moved to the right or left of the trace, but can only be raised or lowered. The trace of the cutting plane is represented by a dash-dotted line. Sections of this kind are usually said to be given “in a projection connection.”
For educational purposes, to understand the geometric components of the shape of an object, inclined sections are sometimes constructed. An example of constructing an inclined section is shown in Fig. 8.12a. When performing this kind of sections, you need to remember that if the direction of the hatching coincides with the contour lines of the section figure, then, as shown in Fig. 8.126, instead of a 45° slope, hatching is performed at angles of 30° or 60° to the main line of the drawing (see Appendix 7).
Let's summarize briefly.
A section is a flat figure obtained by mental
cutting an object with a plane. A section differs from a section in that it does not show the elements of an object located behind the cutting plane;
- - sections can be taken out and superimposed:
- - the section figure should not be broken into unconnected parts. If
If this happens, then depending on the shape of the object, the section should be replaced with an incomplete or complete cut;
Sections may or may not have symbols. Classification
sections but this feature is shown in Fig. 8.11.
Details Category: Engineering graphics
SECTIONS
In Fig. 274, and a drawing of the lever is shown. Main view and the top view with two local sections do not reveal the shape of its middle part. The shape of the middle part can be shown using a profile section (Fig. 274, b), but the elements located behind the cutting plane do not provide additional information about the shape of the part and are superfluous. In such cases, it is convenient to use an image called a section (Fig. 274, c).
A section is an image of a figure obtained by mentally dissecting an object with one or more planes; the section shows only what is located directly in the cutting plane.
In the case shown in Fig. 274, instead of a profile cut, it is enough to make a section (Fig. 274, c). The use of sections reduces graphic work when making a drawing.
Unlike a section, a section shows only what is located directly in the cutting plane; everything that lies behind it is not depicted. In Fig. 275 clearly shows the difference between a section and a section.
Sections, depending on their location in the drawing, are divided into extended and superimposed. The removed sections are placed in a free space in the drawing field (Fig. 276, a) or in a gap in the image of the object (Fig. 276, c). The superimposed sections are placed on the corresponding image of the object (Fig. 276, b).
Extended sections are preferred. Their outline is drawn with solid thick lines (Fig. 276, a). The contours of the superimposed sections are drawn with solid thin lines.
In cases similar to those shown in Fig. 276, at symmetrical figure section, the position of the cutting plane is not indicated.
For asymmetrical sections located in a gap or superimposed, the position of the cutting plane is indicated by a section line with arrows, but is not indicated by letters (Fig. 277, a and b).
In all other cases of making sections, the position of the cutting plane should be shown by a section line indicating the direction of view with arrows, and an inscription should be made above the sections themselves (Fig. 278, a and b).
When the secant plane coincides with the axis of the surface of revolution, limiting the hole or recess, the contour of the hole or recess in the section is shown in full, although this contour is not located in the secant plane (Fig. 277, c, see arrows K), i.e. the section is formed as a cut. If the cutting plane passes through non-circular holes (Fig. 279, a) and the section turns out to consist of separate parts (Fig. 279, b), then the section must be replaced by a section (Fig. 279, c).
When making several identical sections of the same part, only one section is depicted, and the section lines are designated by the same letter (Fig. 278, b). If necessary, the section can be rotated by adding the word “rotated” to the inscription above it (Fig. 278, b, section. If the cutting planes are not parallel to each other, then the inscription “rotated” is not applied (Fig. 278, section B-B).
The section can be performed using several cutting planes, as in Fig. 279, city
Instead of secant planes, it is allowed to use secant cylindrical surfaces, which are then developed into a plane. In Fig. 280 part has various holes. It is convenient to identify the shape of these holes by using a unfolded section of the secant part cylindrical surface, indicated by a section line with arrows and letters. Above the expanded section, an inscription is made in the same letters with the addition of the word “expanded”.
REMOTE ELEMENTS
In cases where it is impossible to depict small elements of the product in all detail on the main image, callout elements are used.
A remote element is an additional separate image in an enlarged form of any part of the product that requires graphic and other explanations regarding the shape, dimensions and other data.
When using a callout element, the corresponding place in the image is marked with a closed solid thin line (circle or oval) with a Roman numeral designation serial number extension element on the shelf of the leader line (Fig. 281).
Above the extension element the same number and scale in which the extension element is made is indicated (the scales may be different).
The remote element should be placed as close as possible to the corresponding place in the image of the object. The callout may contain details not shown in the corresponding image and may differ in content from it. For example, the image can be a view, and the detail element can be a section.
