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| What should be the number of images on the drawing. Images in the drawings. Basic requirements for drawing design |
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MACHINE DRAWING The main requirements of ESKD for the design of drawings All drawings must be carried out in strict accordance with the rules established by ESKD. The design of drawings includes standards for formats, scales, lines, drawing fonts, basic inscriptions. Formats When performing drawings for each of them, the main formats established by the standard GOST 2.301-68 are used. The designations and sizes of the sides of the main formats should correspond to the indications in table 1. Table 1 - Formats If necessary, it is allowed to use the A5 format with the side dimensions of 148´210 mm. Inside the outer frame, each drawing is drawn up with the frame of the working field, which is drawn with a solid thick line at a distance of 20 mm from the left side of the format, which is necessary for filing sheets of the design document, and 5 mm from the other three sides of the format. Scale After determining the working field of the drawing, depending on the complexity and size of the product, the image in the drawing is performed in the appropriate scale, established by GOST 2.302-68. Scale- is the ratio of the image size in the drawing to the corresponding actual (natural) dimensions of the product. The scale of the image in the drawings should be selected from the standard range according to table 2. Table 2 - Standard Scale Series The selected scale should provide a clear image of the product and its structural elements. The scale of the images is indicated in the corresponding column of the main inscription of the drawing by type: 1:1; 1:2; 2:1 etc. If the scale of any image in the drawing differs from that indicated in the main inscription, then its designation is placed above the corresponding image by type: M1: 1; M1: 2; M2: 1. Lines To facilitate the reading of the drawings take nine types of lines set GOST 2.303-68. The types of lines and their main purpose are given in table 3. Table 3 - types of lines | Dimensional and remote lines Hatching lines Superimposed contour lines Contour lines, leader shelves and underline labels | ||||||||||||||||||
| Solid wavy | Cliff Lines View and cut demarcation lines | ||||||||||||||||||
| Dashed line |
| Invisible contour lines | |||||||||||||||||
| Dash-dot thin |
 | Lines axial and centering Lines of sections, which are axes of symmetry for imposed or carried out sections | |||||||||||||||||
| Dot-dotted thickened |  | Lines for the image of elements located in front of the secant plane (“superimposed projection”) | |||||||||||||||||
| Open |
 | Section lines | |||||||||||||||||
| Solid thin with kinks | Long break lines | ||||||||||||||||||
| Dot-and-dot with two dots |
 | Sweep Lines | |||||||||||||||||
| Count | Font size | Type of letters | Note |
| Lowercase | For the name of the documents font 5 | ||
| Uppercase | |||
| Lowercase and uppercase | |||
| Uppercase | |||
| 5 and 6 | Uppercase | ||
| 7 and 8 | 3,5 | Uppercase | |
| Lowercase and uppercase | Top line | ||
| 3,5 | Bottom line | ||
| Rest | 3,5 | Lowercase | |
Images on drawings
A correctly executed drawing has clarity and carries a large amount of information that is understandable to a specialist. Therefore, all drawings are carried out in accordance with the established and applicable rules in all areas of activity. They are based on the combined achievements of science, technology and practical experience. The result of this work is standard.
In engineering graphics, standards are presented in the form of documents containing a number of requirements and norms established for universal and repeated use.
In our country, state standards (GOST) apply, established for all products, as well as for norms, rules, requirements, concepts, designations, etc.
To perform this calculation and graphic work, it is necessary, in addition to knowing the standards for the design of drawings, to study and be able to apply standards for the rules for depicting objects and applying dimensions to drawings, the rules for hatching and axonometric projection images.
The rules for the depiction of objects in the drawings are established by GOST 2.305-68 "Images - views, sections, sections."
Images of objects are performed according to the method of rectangular (orthogonal) projection. In this case, the object is located between the observer and the corresponding projection plane. For the main planes of the projections take six faces of the cube, aligned with the plane in accordance with Figure 6.
Figure 6 - Location of the main views in the drawing
The number of images should be the smallest, but providing a complete picture of the subject when applying the symbols, signs and inscriptions established in the relevant standards.
To reduce the number of images, it is allowed to show the necessary invisible parts of the surface of the object with dashed lines in views in accordance with Figure 7.
Figure 7 - Image of an item indicating invisible parts
Kinds
View - called the image facing the observer of the visible part of the surface of the object.
The following are installed the main views obtained on the main planes of projections:
1. Image on the frontal plane of the projections - front view (main view);
2. Image on the horizontal plane of the projections - top view;
3. The image on the profile plane of the projections - left view;
4. Right view;
5. Bottom view;
6. Rear view.
The image of an object on the frontal plane of projections is called main view. This image should give the most complete picture of the shape and size of the subject.
The names of the species in the drawings do not indicate if they are made in projection communication
If the projection connection is broken or the view is not located in the appropriate place, the projection direction should be indicated by the arrow of the corresponding view. Above the resulting image and arrow, the same capital letter of the Russian alphabet should be applied in accordance with Figure 8.
Figure 8 - Types and simple cuts, and their designations in the drawing
If any part of the subject cannot be shown on the main planes of the projections without distorting the shape, apply additional typeswhich receive on the planes which are not parallel to the main planes of projections (fig. 9). Additional views are denoted similarly to the views on the main projection planes (Fig. 9). An additional view located in direct projection connection with the corresponding image is not indicated, and the projection direction is not indicated. It is allowed to rotate the additional view to the position accepted for the subject in the main image. At the same time, the type designation must be supplemented with a conventional graphic symbol ã - with the “rotated” sign (Fig. 9). If necessary, indicate the value of the angle of rotation.
Figure 9 - Designation of an additional view
Local viewcalled the image of a separate, limited surface area of the subject.
The local view may be limited by the line of a cliff or not, if it is necessary to read the shape of the protruding part of the object (Fig. 8, 9). A local view should be indicated on the drawing like an additional view.
Cuts
To identify the internal structure of the object in the drawings, cuts and sections are made.
Cutcalled the image of the object, mentally cut one or more planes. In this case, mental dissection refers only to this section and does not entail changes in other images of the same object. The section shows what is produced in the section plane and what is located behind it (Fig. 8). It is allowed to show not everything that is located behind the secant plane, if this is not required for understanding the design of the object.
Depending on the number of cutting planes, the cuts are divided into simple -with one cutting plane (Fig. 8) and complex -with several cutting planes (fig. 10, 11).
Depending on the position of the cutting planes, simple cuts are divided into horizontalif the cut plane is parallel to the horizontal plane of the projections, vertical(fig. 8), inclined, if the cutting plane is not parallel to any of the main planes of the projections. Vertical section called frontalif the cutting plane is parallel to the frontal plane of the projections and profileif the cutting plane is parallel to the frontal plane of the projections.
Complicated cuts include steppedwhen the cutting planes are parallel to each other (Fig. 10), and broken linesif the cutting planes intersect at an angle of more than 90 ° (Fig. 11).
Figure 10 - Step cut
The position of the cutting section plane is indicated on the drawing by means of an open section line according to GOST 2.303-68. The initial and final stroke of the section line are drawn outside the contour of the image. In the case of a stepped section, the strokes are also drawn at the transition points of the cutting planes to another level, on broken sections - at the intersection of the cutting planes. At the initial and final stroke, perpendicular to them, at a distance of 2 ... 3 mm from the outer end of the stroke, the arrows indicate the direction of gaze. Outside of the arrows put the same uppercase letters of the Russian alphabet. At the same time over the corresponding image of the incision is an inscription of the type "AA".
When the cutting 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, the position of the cutting plane is not marked for horizontal, frontal and profile sections, and the section do not accompany (fig. 8)
Horizontal, frontal and profile sections, as a rule, are located on the site of the corresponding main species.
A vertical section, when the cutting plane is not parallel to the frontal or profile planes of projections, as well as an inclined section, should be constructed and positioned in accordance with the direction indicated by the arrows on the section line. It is allowed to place such cuts in any place of the drawing, as well as with rotation to the position corresponding to that adopted for the given object on the main image. In the latter case, the legend must be added to the inscription ã - the “rotated” sign.
In the image of a broken section, the cutting planes are conventionally rotated to fit into one plane, while the direction of rotation may not coincide with the direction of gaze. If the combined planes are parallel to one of the main planes of the projections, then a broken section can be combined in the place of the corresponding type (Fig. 11). When the secant plane is rotated, the elements of the object located behind it are drawn as they are projected onto the corresponding plane with which the alignment is made.
Figure 11 - Broken cut
The section, which serves to clarify the device of the object in a separate, limited place, is called local. The local section is distinguished in the form of a solid wavy line (Fig. 8, 12) or thin with kinks, according to GOST 2.303-68. These lines should not coincide with any other lines of the image.
For symmetrical images, you can combine half of the view and half of the section, and if the axis of symmetry is vertical, then, as a rule, they have a view on the left, and a section on the right (Fig. 12). If the axis of symmetry is horizontal, then the view is from above, the section is from below. The line separating them is the axis of symmetry - a thin dash-dotted line.
Figure 12 - Connection of part of the view and part of the section
If there is no symmetry or if the axis of symmetry of the part coincides with any contour line, for example, with an edge, part of the line and part of the section should be separated by a wavy line or a line with kinks drawn from one side or another from the axis of symmetry (Fig. 13). In this case, the line with a kink should extend beyond the contour of the image.
Figure 13 - Combining part of the view and part of the section
Sections
Section The image of a figure resulting from the mental dissection of an object by one or more planes is called. The section shows only what is obtained directly in the secant plane.
It is allowed to use a cylindrical surface as a secant, then deployed in a plane. The designation of the image is accompanied by a conditional graphic sign ä - “expanded”.
Sections not included in the section are divided into handed down(Fig. 14 b, c) and superimposed(Fig. 14 a).
Figure 14 - Section: a - superimposed; b, c - issued.
Remote sections can be located anywhere in the working field of the drawing, also in the gap between parts of the same type. The axis of symmetry of the taken out or superimposed section is indicated by a dash-dotted line without designation, letters and arrows, and the section line is not drawn (Fig. 14).
For asymmetric sections located in a gap or superimposed (Fig. 15), a section line is drawn and arrows are drawn, but no letters are set. In all other cases, the designation of the section line and the section itself is performed as for the section. The secant planes are chosen so as to obtain normal cross sections.
Figure 15 - Asymmetric section: a - remote; b - in the gap; in - superimposed.
The section by construction and location should correspond to the direction indicated by the arrows. It is allowed to place the section on any field of the drawing, as well as with rotation with the addition of a sign (for example, AA).
If the secant plane passes through the axis of the surface of revolution bounding the hole or recess, then the contour of the hole or recess in the section is shown completely (Fig. 14).
The contour of the extended section, as well as the section included in the section, is surrounded by solid main lines, and the contour of the superimposed section by solid thin lines.
If the section is obtained consisting of separate independent parts, the section should be drawn.
On images of sections and cross-sections at the places where the plane cuts the material of the part, depending on the type of material, hatching is performed in accordance with GOST 2.306-68. If the part is made of metal, then hatching is applied by solid thin parallel lines at an angle of 45 ° to the lines of the drawing frame in the same direction on all sections of the same part. If the contour lines of the part or center lines are located at an angle of 45 ° to the lines of the drawing frame, then the angle of inclination of the hatching lines should be taken 30 ° or 60 °. The distance between the hatching lines should be the same for all sections of the given part and can be selected in the range from 1 to 3 mm depending on the hatching area.
If the secant plane passes along a thin wall or stiffener, then such a wall or rib does not conditionally hatch (Fig. 8).
The height of the letters in the designations of types, sections and sections should be one or two sizes greater than the height of the dimensional numbers adopted in this drawing. The minimum diameter of the signs "rotated" and "deployed" is 5 mm.
Dimensioning
All images are dimensioned. When applying dimensions, one should be guided by the main provisions of GOST 2.307-68 “Dimensioning and maximum deviations”.
In the drawing, the dimensions of the true value of the part and its elements are affixed, regardless of the image scale.
Linear dimensions are indicated on the drawing in millimeters without a unit of measurement, angular - in degrees, minutes.
Dimensions in the drawings indicate dimensional numbers, extension and dimension lines (solid thin).
When drawing the size of a straight segment, the dimension line is drawn parallel to this segment, extension lines are perpendicular to the dimension (Fig. 16).
Figure 16 - Drawing rectilinear and angular dimensions
When applying the size of the angle, the dimension line is drawn in the form of an arc with the center at its apex, and extension lines - radially (Fig. 21).
Dimension lines are preferably applied outside the contour of the image. It is not allowed to use contour lines, axial, center and extension lines as dimensional. Avoid intersecting dimension and extension lines.
The dimension line at both ends is limited by arrows resting on extension lines (Fig. 17). The values of the arrow elements of the dimension lines are selected depending on the thickness of the lines of the visible contour and draw them approximately the same throughout the drawing. The shape of the arrow and the approximate ratio of its elements are shown in Figure 17.
Figure 17 - Shapes and sizes of arrow elements
Extension lines are drawn from the lines of the visible contour. Extension lines should extend beyond the ends of the arrows of the dimension line by 1 ... 5 mm (Fig. 16).
The distance between the contour line and the dimension line is selected depending on the size of the image and the saturation of the drawing. The minimum distance between the dimension line and the contour line should be 10 mm, and the minimum distance between parallel dimension lines should be 7 mm (Fig. 16).
Dimensional numbers are applied over the dimension line as close as possible to its middle. When applying several parallel dimension lines, the dimension numbers should be staggered (Fig. 16).
Linear dimensions for various inclined dimension lines and angular dimensions, for different positions of the angles, are applied as shown in Figure 21. If the dimension number of a linear or angular dimension applied above the middle of the dimension line falls into shaded areas (within an angle of 30 °), then it is carried out on a horizontally located shelf of the leader line. For angles of small sizes with a lack of space, dimensional numbers are placed on the shelves of leader lines in any zone.
If there is not enough space for the application of arrows and dimension numbers, they are applied using one of the methods shown in fig. 18. If there is a lack of space for the arrows on the dimension lines arranged in a chain, the arrows can be replaced with serifs plotted at an angle of 45 ° to the dimension lines or clearly marked points (Fig. 18). If there is not enough space for an arrow due to a closely located contour or extension line, the latter can be interrupted.
Figure 18 - Drawing dimension lines with insufficient space for arrows
Dimension numbers are not allowed to be divided or intersected by any lines of the drawing. In the place where the dimension number is applied, the axial, center lines and lines of the hatching interrupt (Fig. 19). Contour lines are not allowed to interrupt.
Figure 19 - Drawing dimension lines and numbers when drawing contour lines and hatching lines.
It is recommended to group the dimensions related to the same structural element (groove, protrusion, hole, etc.) in one place, placing them on the same image in which the geometric shape of this element is shown most fully (Fig. 20) .
Figure 20 - Dimensioning the hole in the cut
A capital letter is placed in front of the radius dimension number. R, (eg, R20), before the size number of the diameter - the sign ñ (for example, ñ 20 ).
With a large radius, the center of the arc of a circle is allowed to approach the arc. In this case, the dimensional line of the radius is shown with a break at an angle of 90Å. If you do not need to specify dimensions that determine the position of the center of a circular arc, then the dimension line of the radius is allowed not to bring to the center and to shift relative to the center. When conducting several radii from one center, the dimension lines of any two radii do not fit on one straight line.
In the case of an image with a sphere, if it is difficult to distinguish it from other surfaces, it is allowed when applying the diameter (radius) size, the sphere is allowed to put the word "Sphere" or sign ?? (eg, Sphere R15,ñ 40 ).
The square in the drawing is determined by two sizes of its sides or one size with the sign ò (Fig. 21). Diagonals drawn by thin lines, conventionally denote a plane.
The dimensions of the chamfers at an angle of 45Å are plotted as shown in Fig. 21. The dimensions of the chamfers at different angles are indicated by linear and angular dimensions or by two linear dimensions.
Figure 21 - Dimensioning of detail elements.
In the case of execution in the drawing of an image in which the view is combined with a cut (top view or left), as well as when drawing a symmetrical figure to the axis of symmetry or with a break, the dimension line is drawn with a break, which is made further than the axis or break line of the image (Fig. . 22).
Figure 22 - Drawing dimension lines with a break
The total number of sizes should be minimal, but sufficient to manufacture and control the product. The dimensions of the same element in the drawing are not allowed to be repeated. The dimensions of several identical elements of the product, as a rule, are applied once with the number of these elements on the shelf or below it (Fig. 23). Moreover, for elements evenly spaced around the circumference (for example, holes), the angular dimensions between them are not set, provided that one of these elements lies on one of the axes of symmetry (Fig. 23 a). Only the size of the diameter of the circle on which the centers of the holes are located (ñ 32 on fig.23 a). If none of the holes lies on the axis of symmetry, then you should set the angle to the first element (Fig. 23 b).
Figure 23 - Dimensioning the size and location of the holes on the circle: a - on the axes of symmetry; b - outside the axis of symmetry
The rules for the image of objects (products, structures and their constituent elements) on drawings for all industries and construction are established by GOST 2.305 - 2008 * "Images - types, sections, sections".
Images of objects should be performed using the method of rectangular (orthogonal) projection. In this case, the object is placed between the observer and the corresponding projection plane. When constructing images of objects, the standard allows the use of conventions and simplifications, as a result of which the indicated correspondence is violated. Therefore, the figures produced during the projection of the object are called not projections, but images. As the main planes of the projections take the faces of the hollow cube, in which the object is mentally placed and projected it onto the inner surfaces of the faces. The edges are aligned with the plane (Figure 2.1). As a result of this projection, the following images are obtained: front view, top view, left view, right view, rear view, bottom view.
The image on the frontal plane is taken on the drawing as the main one. The object is positioned relative to the frontal plane of the projections so that the image on it gives the most complete picture of the design features of the object and its functional purpose.
Will consider main image selection on the example of such an object as a chair. We depict its projections schematically:
We speculate: the functional purpose of the subject - the subject serves to sit on it. In which of the drawings this assignment is most understandable - probably this is Figure 1 or 2, the 3rd is the least informative.
The design features of the object - there is a seat, a back, for the convenience of sitting on a chair, located at a certain angle relative to the seat, legs, having the seat at a certain distance from the floor. On which of the figures are these features most clearly presented? Obviously, this is Figure 1.
Conclusion - as the main view, we select the projection number 1, as the most informative and most comprehensive information about the functional purpose of the chair and its design features.
Similarly, it is necessary to argue when choosing the main image of any object!
Images in the drawing, depending on their content are divided into types, sections, sections.
View - image of the visible part of the surface of the object facing the observer.
Views are divided into basic, local and optional.
Main types — images are produced by projecting an object on a projection plane. There are six of them, but most often I use the main three for getting information about the item: horizontal π 1, frontal π 2 and profile π 3 (Figure 2.1). With this projection receive: front view, top view, left view.
The names of views on the drawings are not inscribed, if they are located in a projection connection (Figure 2.1). If the top, left and right views are not in projection connection with the main image, then they are marked on the drawing with an “A” type lettering. The direction of sight is indicated by an arrow, indicated by the capital letter of the Russian alphabet. When there is no image on which the gaze can be shown, the name of the species is labeled.
Figure 2.1 Formation of the main species
Local view - the image of a separate limited place on the surface of an object on one of the main projection planes. The local view can be placed on any free space of the drawing, marking type “A”, and the associated image should have an arrow indicating the direction of gaze, with a corresponding letter designation (Figure 2.2 a, b).
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| but |
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| b |
Figure 2.2 - Local species
The local view may be limited by the line of breakage, if possible in the smallest size (Figure 2.2, a), or not limited (Figure 2.2, b).
Additional views - images obtained on planes that are not parallel to the main projection planes. Additional views are performed in those cases if any part of the item cannot be shown on the main views without distorting the shape and size. An additional view is marked on the line with an “A” type inscription (Figure 2.3, a), and an arrow associated with an additional image of the subject is marked with an appropriate letter designation (Figure 2.3, a) indicating the direction of sight.
When the additional view is located in a direct projection link with the corresponding image, the arrow and the inscription above the view are not applied (Figure 2.3, b). The additional view can be rotated while maintaining the position adopted for the item in the main image. At the same time, a sign (“Rotated”) is added to the inscription “A” (Figure 2.3, c).
Basic, local and additional types are used to image the shape of the external surfaces of the object. The successful combination of them allows you to avoid the dashed lines, or reduce their number to a minimum. To reduce the number of images, it is allowed to display the necessary invisible parts of the surface with the help of dashed lines. However, identifying the shape of the internal surfaces of the subject with the help of dashed lines greatly complicates the reading of the outline, creates the prerequisites for its incorrect interpretation, complicates the size and symbols, therefore, their use should be limited and justified. To identify the internal (invisible) configuration of the item, apply conditional images - sections and sections.
Figure 2.3
2.2 Cuts
The section is the image of the object mentally dissected by one or several planes..
On a section showing what is located in the cutting plane and what is located behind it.
2.2.1 Classification of cuts
Depending on the the number of cutting planes Sections are divided into (Figure 2.4):
- simple - at one cutting plane (Figure 2.6);
- complicated - with several cutting planes (Figure 2.9, 2.10).
Figure 2.4 - Classification of cuts
The position of the cutting plane is shown on the main image with a thick open line (1,5 s, where s- thickness of the main line). The length of each stroke is from 8 to 20 mm. The direction of the view is shown by arrows perpendicular to the strokes. Arrows depict at a distance of 2-3 mm from the outer ends of the strokes. The name of the cutting plane is indicated by capital letters of the Russian alphabet. The letters are applied parallel to the horizontal lines of the main inscription, regardless of the position of the arrows (Figures 2.5, 2.6, 2.9, 2.10, 2.11).
If, when making a simple section, which is in projection connection with the main image, the section plane coincides with the plane of symmetry, then the section plane is not drawn, and the section is not signed.
Figure 2.5 - Designations of cuts in the drawing
Figure 2.6 - A simple section: a) - frontal; b) - local
Depending on the cutting plane positions relative to the horizontal plane of the projections, the sections are divided into:
- horizontal - the cutting plane of the parallel horizontal plane of the projections (Figure 2.7, b);
- vertical - the cutting plane is perpendicular to the horizontal plane of the projections (Figure 2.7, c, d);
- inclined - the cutting plane is with the horizontal plane of the projections an angle other than the straight line (Figure 2.8).
Figure 2.7 a - model details "Crank"
Figure 2.7 b - Simple horizontal section
Vertical the sections are called:
- frontal if the cutting plane is parallel to the frontal plane of the projections (Figure 2.7, c);
- profile if the cutting plane is parallel to the profile plane of the projections (Figure 2.7, d).
Figure 2.7 c - Simple frontal section
Figure 2.7 g - Simple profile section
Figure 2.8 - Inclined cut
Challenging Sections are divided into:
- stepped if the cutting planes are parallel (horizontal, horizontal, horizontal) (Figure 2.9);
- broken lines if the cutting planes intersect (Figure 2.10).
Figure 2.9 - Complicated - Step cut
Figure 2.10 - Difficult - Broken incision
Sections are called:
- longitudinal if the cutting planes are directed along the length or height of the object (Figure 2.7, c);
- lateral if the cutting planes are directed perpendicular to the length or height of the object (Figure 2.7, d).
Sections that serve to clarify the device of an item only in certain, limited places are called by local .
Figure 2.11 a - Examples of cuts
Figure 2.11 b - Examples of cuts combined with species
2.2.2 Making cuts
Horizontal, horizontal and profile cuts can be located at the site of the respective main species (Figure 2.11, a, b).
A part of the species and a part of the corresponding section can be joined by separating them with a solid wavy line or a line with a break (Figure 2.11, b). It should not coincide with any other image lines.
If half of the view and half of the section are joined, each of which is a symmetrical figure, then the separation line is the axis of symmetry (Figures 2.11, b; 2.12). It is impossible to combine half of the view with half of the section, if any image line coincides with the axial one (for example, ridge). In this case, the majority of the species is connected with the smaller part of the species, or most of the species with the smaller part of the species.
It is allowed to separate the section and the type of fine-punched thin line that coincides with the trace of the plane of symmetry of not the whole subject, but only its part, if it represents the body of rotation. When half of the species is joined with half of the corresponding section, the right side of the vertical axis and the bottom of the horizontal one are located (Figure 2.12).
Figure 2.12
Figure 2.13
Local The sections are highlighted in the form of solid wavy lines. These lines should not coincide with any other image lines (Figure 2.13).
Section shapes obtained by different cutting planes when performing complex Split, do not separate one from the other by any lines.
A complex stepped section is placed on the site of the corresponding main view (Figure 2.9) or in any place of the drawing.
For broken sections, the cutting planes are conventionally rotated to fit into one plane, while the direction of rotation may not coincide with the direction of gaze. If the combined planes turn out to be parallel to one of the main projection planes, the broken section is allowed to be placed in the place of the corresponding type (Figure 2.10).
When the cutting plane is rotated, the elements of the object located behind it are drawn as they are projected onto the corresponding plane with which the combination is made. It is allowed to connect a stepped section with a broken line in the form of one complex section.
2.3 Sections
Cross section the image of the figure, which is obtained when the object is thought to be intersected by the section plane, is called (Figure 2.14).
On the cross section, only that which falls directly into the cutting plane is shown.
The secant planes are chosen so as to obtain normal cross sections.
Sections are divided into:
- sections that are part of the section (Figure 2.15, a);
- sections that are not part of the Figure 2.15.b).
Not included in the section are divided into:
- handed down (Figures 2.14, a; 2.14, c; 2.15, b; 2.16, a; 2.17, a; 2.18);
- superimposed (Figures 2.14, b; 2.16, b; 2.17, b).
The removed sections are preferable and are allowed to be arranged in a gap between parts of the same type, along the trace of the section plane with a symmetrical figure of the section, anywhere on the field of rotation, as well as rotation (Figures 2.14, a, c; 2.15, b; 2.16, a; 2.17, a; 2.18, a).
For the image of the trace of the section plane, the thick open line with the arrows indicating the direction of gaze is used on the image, and the cutting plane is designated by written letters of the Russian alphabet. The section is accompanied by an AA-type inscription (Figure 2.14).
The ratio of the dimensions of the arrows and the breaks of the open line must correspond to Figure 2.14. The initial and final touch should not cross the contour of the image.
The letter designations are given in alphabetical order without repetition and, as a rule, without permissions. The size of the font of letters should be larger than the size of the dimensional numbers approximately two times. The letter designation is parallel to the title block, regardless of the position of the section plane.
In the general case, when the section is located on any free space in the drawing, the position of the trace of the section plane is depicted as above, and the section image is accompanied by an inscription corresponding to the name of the section plane (Figure 2.14, a; 2.15, b).
In the cases shown in Figures: 2.14, b, c; 2.17, a, b; 2.18, a (superimposed sections; sections made in a type break; sections made on the continuation of the section of the section plane) - for symmetrical sections the trace of the cutting plane is not shown and the section is not accompanied by an inscription.
Figure 2.14 but
Figure 2.14 b
Figure 2.14 at
For unbalanced sections , located in a gap, or superimposed, the trace of the section plane is depicted, but not accompanied by letters (Figure 2.16). The section is also not accompanied by the inscription.
The contour of the removed section is made with a thick solid line (the main line), and the contour of the superimposed section with a thin solid line, while the contour of the view is not interrupted.
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Figure 2.15
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Figure 2.16
Figure 2.17 but,b
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| but | b |
Figure 2.18
For several identical sections of the same item, the section lines are denoted by one letter and one section is scribed. If in this case the cutting planes are directed at different angles, then the “Rotated” sign is not applied (Figure 2.19).
It all depends on many factors, but is primarily determined by the complexity of the geometric shape of the product, its size, as well as the requirements placed on it. You should strive for the minimum number of images and their simplicity, not at the expense of ease of reading the drawing - the most important production requirement.
Thus, the geometric shape of a part bounded by surfaces of revolution or the simplest combinations of them can be determined by a single image (see Fig. 7.5 and 7.86). Here the question may arise: what is appropriate to apply - a section, a connection of a part of a view with a part of a corresponding section, a view with drawing lines of an invisible outline?
Practice shows that the most comprehensive, but also the most laborious, is a full cut (Fig. 7.87, a), less clear, but also less laborious - connecting part of the species with the corresponding part of the cut (Fig. 7.87,6,0), even less clear , but also less labor-consuming - the view with the lines of an invisible contour printed on it (Fig. 7.87, d). All the wider use of plotters makes the design of the drawing in Fig. 7.87, g is admissible, but it should be applied, in particular, in cases when it is possible to avoid using lines of invisible contour for dimensioning, roughness signs, marking of bases, etc. (Fig. 7.88).
It is possible to use local (partial) species more widely (fig. 7.89), remote elements and sections (see fig. 7.19), breaks (fig. 7.90), half of the symmetric images (fig 7.91).
However, it is impractical, for example, symmetric views from above in fig. 2.56 and 7.91 to replace them with halves, as this will make it difficult for the model maker to understand the drawing.
The rational solution of the drawing largely depends on the correct choice of the main image. But the main image (correctly selected) can be differently oriented on the plane of the drawing. Therefore, with its orientation, it is necessary to think about other necessary images so that, if possible, they do not need to draw the lines of an invisible contour (Fig. 7.92, a, b), so that it is convenient to dimension, apply signs of roughness.
In fig. 7.93 two solutions of the roller drawing are given: on A4 format and A3 format. Both solutions do not contradict clause 1.3 of GOST 2.305-68. The solution “a” may even be preferable to the solution “b” if the roller is made on a vertical lathe. Execution according to the scheme “a” of the training drawings of the parts bounded by the surfaces of rotation is quite acceptable, if it allows to significantly reduce the consumption of drawing paper. However, it must be remembered that long drawings are more convenient to read when the title block is located along the larger side of the format.
Casting housings, bearing housings, racks and other similar parts are usually depicted so that the main machined plane (design base) gets a horizontal position in the drawing. From this base, dimensions are put down (taking into account the auxiliary design bases) to the surfaces formed with the removal of a layer of material (by machining). The dimensions that determine the casting before it is processed are stamped from their foundry bases, the main and auxiliary ones.
In fig. 7.91 main design and foundry bases for clarity conventionally marked with blackened triangles. To increase the strength of castings, in order not to increase the wall thickness, stiffening ribs are used (in Fig. 7.91 there are two, right and left, b mm thick) .Technical requirements placed on the drawings parts made by casting (most of them for cast iron are shown in Fig. 7.91), in training drawings they are usually limited to the requirements of clauses 2 and 3. Molding slopes are attached to surfaces if there are no constructive slopes in the castings, baking easy removal of the model from the mold. Instead of referring to GOST 3212-80 *, they can be specified in the drawing with degree values (10 ... 30) depending on the size of the surface height and the method of casting. On the drawings, as a rule, only structural slopes are depicted (as, for example, at a cone 0 34 in Fig. 7.91), noting the requirements for molding slopes in TT. For cast parts, smooth gradual transitions from one surface to another are also characteristic (Fig. 7.94). in expanded form do not give. If necessary, a drawing of a scan can be issued by a technological document and is not included in the design documentation. However, if the image of a part made flexible does not give an idea of the shape and size of its individual elements, a full or partial scan of the detail showing it is impossible to indicate the details on the image (fig. 7.95, a). If all three holes are cut down during punching, then a full scan is required (Fig. 7.95,6). It is allowed to combine the image of a part of the scan with a view (see Fig. 2.8, a and 7.96). When choosing the scale of images, one should be guided by the convenience of their reading, prevent thickening of the dimension lines, surface roughness symbols and other signs, given that the larger the drawing format, the less convenient it is to use it. Fig. 7.97 shows the working drawing. The anchor wheel is depicted in M 20: 1, the teeth in M 200: 1, A3 format. The drawing is user friendly. (The HV 460-510 record indicates the required Vickers hardness.) The inscriptions and signs applied to the flat surface of the object, regardless of the method of their application, are depicted in a completely appropriate form (Fig. 7.98). 
If the inscriptions and signs should be applied on a cylindrical or conical surface, then an image of the inscription is placed in the drawing in the form of a scan. Indicate the method of inscriptions and signs (engraving, stamping, embossing, etc.), background coating, inscriptions and signs, and other information (Fig. 7.99).
In fig. 7.100 is a drawing of a stamped part with folds, flanging (holes with concave sides) and extrusions (rifts). When making drawings of such parts, it is necessary to use GOST 17040-80 * containing the size ranges of these elements (D, R, etc.). So, the question of the number of images, their content, relative position, scale, etc. is decided in a comprehensive manner from the terms of convenience of the drawing. 
Properly executed drawing has clarity and carries a large amount of information that is clear to the expert. Therefore, all drawings are carried out in accordance with established and applicable rules in all areas of activity. They are based on the combined achievements of science, technology and practical experience. The result of this work is standard.
In engineering graphics, standards are presented in the form of documents containing a number of requirements and standards established for universal and reusable use.
In our country, there are state standards (GOST) established for all products, as well as for norms, rules, requirements, concepts, designations, etc.
To perform this design and graphic work it is necessary, in addition to knowing the standards for drawing design, to learn and apply the standards for the rules for the image of objects and drawing dimensions on drawings, rules for hatching and axonometric images.
The rules for depicting objects on drawings are set by GOST 2.305-68 "Images - views, sections, sections".
Images of objects are performed by the method of rectangular (orthogonal) projection. In this case, the object is located between the observer and the corresponding projection plane. For the main planes of projections take six faces of the cube, combined with the plane in accordance with Figure 6.
Figure 6 - The location of the main species in the drawing
The number of images should be the smallest, but providing a complete picture of the subject when applying the conventions, signs and inscriptions established in the relevant standards.
To reduce the number of images, it is allowed to show the necessary invisible parts of the surface of an object using dashed lines in accordance with Figure 7.
Figure 7 - The image of the object showing the invisible parts
Kinds
View - called the image facing the observer visible part of the surface of the object.
The following are installed the main species obtained on the main projection planes:
The image on the frontal plane of the projections - front view (main view);
The image on the horizontal plane of the projections is a top view;
The image on the profile plane of the projections - left view;
Right view;
Bottom view;
Back view.
The image of the object on the frontal plane of the projections is called the main view. This image should give the most complete picture of the shape and size of the subject.
The names of views in the drawings are not inscribed, if they are made in a projection connection
If the projection connection is broken or the view is not located at the appropriate place, then the direction of projection should be indicated by an arrow in the corresponding view. Above the image and the arrow should be applied the same uppercase letter of the Russian alphabet in accordance with Figure 8.
Figure 8 - Views and simple cuts, and their designations in the drawing
If any part of the object cannot be shown on the main planes of the projections without distorting the form, apply additional viewswhich receive on the planes which are not parallel to the main planes of projections. Additional views are designated similarly to views on the main planes of projections. The additional view, located in direct projection connection with the corresponding image, is not indicated, and the direction of projection is not indicated. Allowed to turn an additional view to the position adopted for the subject in the main image. At the same time, the type designation must be supplemented by a conventional graphic symbol - the “rotated” sign (Fig. 9). If necessary, indicate the value of the angle of rotation.
Figure 9 - Designation of an additional type
Local viewcalled the image of a separate, limited space surface of the object.
The local view may be limited by the line of a cliff or not, if it is necessary to read the shape of the protruding part of the object (Fig. 8). Local view should be marked on the drawing like an additional view.
28.1. Selection on the drawing of the main image. When constructing drawings, it is important to choose a number of images that allows you to obtain sufficient information about the product. At the same time, one should strive for the smallest number of images giving the necessary characteristics to the depicted object.
The number of images in the drawing depends on the complexity of the constructive shape of the object. Often, to provide a complete picture of the shape of a part, a single image is sufficient — a type or section using established signs and inscriptions (for example, signs of diameter, square, indicating the thickness and length of the part, etc.). Examples of such images were given in the manual earlier.
To identify the shape of the parts in the drawing is of great importance the correct choice of the main image. Such an image can be a view, a slit or their connection.
The main image should give the most complete picture of the shape of the part, the shape of its parts and their sizes, that is, the most complete information. From the correct choice of the main image depends on the number of images in the drawing. For this purpose, the object is tried to be positioned relative to the projection planes so that most of its elements are depicted as visible on the main view.
Usually in the drawing, the detail is shown in the position that it occupies during processing. For example, the axis of the parts obtained on the machine turning, in the drawing have horizontally (bushes, shafts and other parts).
- Remember which image is called the main one and why.
- What principles should guide the choice of the main image?
28.2. Incomplete images. When making views and cuts in the drawing, it is allowed to use incomplete images. So, if a view or section is a symmetrical figure, then it is allowed to draw half of the part to the centerline (top view in Fig. 173, a) or slightly more than half with drawing a break line (Fig. 173, b).
Fig. 173
Instead of the full view, it is allowed to show only the individual elements of the detail in the drawing, if its shape is well read. Figure 174 instead of the top view shows an image of only the keyway.
Fig. 174
If there are symmetrically or evenly spaced elements on the part (for example, holes), then it is allowed to show one or two of them in the drawings, and for the others, only centers should be marked (Fig. 175 and 176). Before the size number indicate their number.
Fig. 175
Fig. 176
Figure 177 shows a drawing in which only a few elements (teeth) of a gear are conventionally shown, and the rest are not shown.
Fig. 177
When depicting an object in one projection, it is allowed to conditionally designate its length. In this case, a Latin lowercase letter l is written in front of the size number (fig. 178).
Fig. 178
Long parts that have a constant (Fig. 179, a) or regularly changing (Fig. 179, b) cross-section can be shown with a gap. The dimension line is not interrupted, the dimension number must correspond to the actual size of the part.
It should be borne in mind that partial images with a gap are limited either by a solid wavy line (as in Fig. 179, a and b), or by a solid thin line with a break that extends beyond the contour of the image by a length of 2 ... 4 mm (Fig. 179, c).
Fig. 179
- What image can be called incomplete and why?
- What incomplete images can be used on drawings? Give examples.
28.3. Additional views. The standard allows to use, besides the main planes of the projections (the faces of the cube) and additional ones, to depict such detail elements that are projected onto the main planes with distortion (Fig. 180 a). An additional plane is placed parallel to the surface of the part element, the image of which must be executed (Fig. 180, b). Then it is combined with the main plane of projections. The image obtained on this plane is called additional view.
In Figure 180, to the left of the part in the top view it is conventionally not shown, since when projected on a horizontal plane, it is depicted distorted. The additional view gives an undistorted view of the shape and size of this part of the part.
Fig. 180
In the drawing, an additional view is marked with type A inscription, and the direction of the sight is indicated by an arrow with the same letter designation in the drawing.
It is allowed to rotate an additional view (Fig. 180, d).
In this case, the sign is added to the inscription - "turned", placing it next to the letter.
In the case when the additional view is located in the projection connection, as it is done in Figure 180, c, it is not designated and not signed.
- When do they use an extra view?
- How to choose a plane to build an additional view?
28.4. Image smooth transitions. The lines of mutual intersection of the surfaces (Fig. 181, a) on technical drawings are allowed to be shown in a simplified way (unless their exact construction is required). Thus, the line of intersection of two cylinders in the drawing can not be built by points for carrying it along the curve, but can be performed using a compass (fig. 181, b). In this case, the curve curve is replaced by an arc of a circle. In some cases, the curved lines are replaced by straight lines (Fig. 181, c).
Fig. 181
In the drawing, a smooth transition of one surface to another can be represented by a solid thin line, not bringing it up to the contour of the surface (see. Fig. 181, c). A smooth transition can sometimes not be shown at all (Fig. 182).
Fig. 182
- Why do you think smooth transition lines are allowed to be simplified?
- What lines in the drawing are allowed to replace curved curved lines?
28.5. Text and sign information on drawings. The drawing, as established earlier, is a collection of graphic and iconic components that provide complete information about the product. In addition to the image, the dimensions of the part, the names of the material on some drawings put and data on its processing.
It is known that in any method of manufacturing parts its surface will not be completely smooth. The combination of all the irregularities that form the surface relief is called roughness. The degree of surface roughness in the drawing is indicated by special signs. Together with the sign indicate the value of the parameter or the numerical value of the roughness (see Fig. 2).
On the technical drawings, you can notice the dimensional numbers with additional entries: +0.5; Ø60 ± 0.02, etc. What do they mean?
To manufacture a part with absolutely accurate dimensions is almost impossible. As a result, the dimensions will be slightly different than the specified. Therefore, in the drawing, next to the dimension number, indicate the deviation of the size from the given or limiting numbers between which the dimensions may vary.
GOST also establishes other signs that give the characteristic details or explaining its geometric shape.
- What inscriptions can be contained in the drawings?
- What conventional signs are used on drawings to indicate surface roughness?
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