Building a part in three projections. Building a third view from two known views

The date____

Grade: 9 " "

Topic: Building a third type of object from two data

Purpose: to teach how to build a third type of object according to two data

Tasks:

To consolidate knowledge about the views in the drawing;

Develop spatial representation and thinking, the ability to analyze the geometric shape of an object and skills in working with drawing tools;

To educate: diligence, accuracy, creative attitude to work, independence

Lesson type: combined

Lesson methods: explanatory - illustrative, practical

Form of organization: collective, individual

During the classes

Org moment

Repetition

2 . Test

Message new

First of all, you need to figure out the shape separate parts surface of the depicted object. To do this, both given images must be viewed simultaneously. It is useful to keep in mind which surfaces correspond to the most common images: triangle, quadrilateral, circle, hexagon, etc.

In a top view in the form of a triangle, triangular prism, triangular and quadrangular pyramids, cone of revolution, etc.

Let's analyze the construction of the view on the left according to the main view and the top view

The shape of many objects is complicated by various cuts, cuts, and intersections of the surface components. Then you first need to determine the shape of the intersection lines, and you need to build them by individual points, introducing the designations of the projections of the points, which, after completing the constructions, can be removed from the drawing.

On fig. a left view of an object is constructed, the surface of which is formed by the surface of a vertical cylinder of revolution, with a T-shaped notch in its upper part and a cylindrical hole with a frontally projecting surface. The plane of the lower base and the frontal plane of symmetry F were taken as base planes. M and im symmetrical. When constructing the third type, the symmetry of the object with respect to the F plane was taken into account.

Anchoring

Work on cards (build on two given third view)

Outcome

Construction of the third type by measurement.

opens (fig.9) (technical drawing closed.

If the part is not very complex and for some reason it is impossible to make a projection link with the top view, the third view is delayed using a ruler. If the part is simple and you can imagine it in your mind, you don't need to draw a technical drawing.

Question: Who will build a top view of this part?

The student is called at will and builds a left view of detail 9 on the IAD.

The technical drawing of the part is opened for verification.

Generalization: This method may not always be applicable. For example, if there was no projection relationship between the front view and the top view, would we be able to draw a cutout line? No. Therefore, I still recommend that you adhere to the projection connection in all three types.

4. Now back to our original task. In the lessons we will use the "constant line" method to build a drawing.

You have two types of parts printed on paper on your desk.

Exercise 1: Glue the first task in the notebook so that there is room for building the third view. Position the notebook horizontally Draw a constant straight line. Build the third view.

Students work in notebooks.

The one who completed the task first, performs it at the IAD.

This problem has several solutions.

Question: Who will find another solution?

Students take turns coming to the board and asking

your decisions. open (Fig. 6, 5, 4, 3, 2)

5. Exercises for the eyes.

To rest our eyes, let's do some gymnastics for them.

Hold a pencil in your outstretched hand in front of you. Without taking your eyes off him, bring it to the bridge of your nose, remove it directly from you (so several times), then on an outstretched hand, following the pencil, move it to the right - to the left.

6. Task 2:Glued the second task into the notebook. A third view was built according to two types of details.

opens(Fig. 10) The technical drawing is closed.

The one who first completes it in a notebook draws on the board.

In case of difficulty, a technical drawing of the part is opened or for verification after completing the task.

7. Homework:

A. D. Botvinnikov Section 13.4. At the end of the paragraph, tasks for exercises: fig. 112, 113,114.

Paste task 3 into your notebook.(Fig. 11) For two types of parts, build a third.

Construction of the third type on two known types.

Let the main view and the top view be known. It is necessary to build a view on the left.

Two main methods are used to build a third type according to two known ones.

Building a third view using an auxiliary line.

In order to transfer the size of the width of the part from the top view to the left view, it is convenient to use the auxiliary straight line (Fig. 27a, b). It is more convenient to draw this straight line to the right of the top view at an angle of 45° to the horizontal direction.

To build a third projection A 3 peaks BUT, draw through its frontal projection A 2 horizontal line 1 . It will contain the desired projection A 3. After that, through a horizontal projection A 1 draw a horizontal line 2 until it intersects with the auxiliary line at the point A 0. Through the dot A 0 draw a vertical line 3 to the intersection with the line 1 at the desired point A 3.

The profile projections of the other vertices of the object are constructed similarly.

After an auxiliary straight line is drawn at an angle of 45 °, it is also convenient to construct a third projection using a T-square and a triangle (Fig. 27b). First through frontal projection A 2 draw a horizontal line. Draw a horizontal line through the projection A 1 there is no need, it is enough, by applying a T-square, to make a horizontal notch at the point A 0 on the auxiliary line. After that, having slightly moved the T-square down, we apply the square with one leg to the T-square so that the second leg passes through the point A 0, and mark the position of the profile projection A 3.

Building a third view using baselines.

To construct the third view, it is necessary to determine which lines of the drawing should be taken as the base lines for measuring the dimensions of the object images. As such lines, they usually take axial lines (projections of the planes of symmetry of the object) and projections of the planes of the bases of the object. Let's take an example (Fig. 28) of building a view on the left according to two given projections of an object.

Rice. 27 Building a third projection from two data

Rice. 28. The second way to build a third projection from two data

Comparing both images, we establish that the surface of the object includes surfaces: regular hexagonal 1 and quadrangular 2 prisms, two cylinders 3 and 4 and truncated cone 5 . The object has a frontal plane of symmetry F, which is convenient to take as a base for measuring the width of individual parts of an object when constructing its view on the left. The heights of individual sections of the object are measured from the lower base of the object and are controlled by horizontal communication lines.

The shape of many objects is complicated by various cuts, cutouts, and intersections of the constituent surfaces. Then you first need to determine the shape of the intersection lines, build them on individual points, introducing the notation of the projections of the points, which, after completing the constructions, can be removed from the drawing.

On fig. 29, a left view of an object is constructed, the surface of which is formed by the surface of a vertical cylinder of revolution with T-shaped notch in its upper part and a cylindrical hole occupying a front-projecting position. The plane of the lower base and the frontal plane of symmetry were taken as base planes. F. Image T-shaped notch in the left view built using points A, B, C, D and E contour of the cut, and the line of intersection of cylindrical surfaces - using points K, L, M and they are symmetrical. When constructing the third type, the symmetry of the object relative to the plane is taken into account F.

Rice. 29. Building a view on the left

5.2.3. Construction of transition lines. Many details contain lines of intersection of various geometric surfaces. These lines are called transition lines. On fig. 30 shows a bearing cover, the surface of which is limited by surfaces of rotation: conical and cylindrical.

The intersection line is built using auxiliary cutting planes (see Section 4).

The characteristic points of the intersection line are determined.

Having made the layout of the drawing and having completed two given projections of the part, they proceed to the next stage of work - the construction of the third projection of the part.

Two preset projections can be: frontal and horizontal, frontal and profile. In both cases, the construction is carried out similarly.

On fig. 2 shows the construction of a profile projection according to the given frontal and horizontal projections.

The construction was carried out by the method of rectangular (orthogonal) projection, i.e., all three images (projections) were built without breaking the projection connection, but the coordinate axes and projection connection lines are absent in the drawing. To ensure that the projection connection is not violated during the construction of images, it is necessary to apply a T-square or triangle in the direction of the corresponding projection connection simultaneously to two projections, on which in this moment carry out construction.

According to two given projections, in this case, frontal and horizontal, a profile is constructed by transferring dimensions in height from the frontal projection, and in width - from the horizontal projection. To do this, first determine the position of the profile dimensional rectangle, draw the axis of symmetry and perform construction in the following order. The size a from the frontal projection (part height) and size G from a horizontal projection (part width) is used when constructing a dimensional rectangle. The base of the model is a parallelepiped with a width G (already built) and height in , which is built on a profile projection, taken from the front. To do this, to the frontal projection in height in a T-square is applied, and a thin horizontal line is drawn on the profile within the overall rectangle. The lower base of the model has been built on the profile projection.

The model is based on a quadrangular prism with two inclined faces. Its upper base is located at a height a from the bottom base of the part and is already built as the height of the bounding rectangle. It remains to build the width of the upper and lower bases. They are the same size and are the same size. d , which is taken on a horizontal projection. To do this, on a horizontal projection, measure half the distance d and lay it on the profile projection on both sides of the axis of symmetry. Two vertical lines are drawn through the constructed points, limiting the image of this prism. The prism standing on the base of the part is built.

The part has two slots: left and right. On the frontal projection, they are depicted by lines of an invisible contour, and on a horizontal projection, by a line of a visible contour. To build them on a horizontal projection from the center line, measure half the distance e and, accordingly, lay on the lower base of the profile projection. From the constructed points, two thin lines parallel to the axis of symmetry are drawn upwards. They will limit the distance along the width of the slot. Its height (distance b ) are built according to the frontal projection, for which to the upper point of the distance b a T-square is applied and at this height, a thin horizontal line is drawn on the profile projection, limiting the slot from above.

The image of the visible part of the surface of the object facing the observer is called the view.

GOST 2.305-68 establishes the following name for the main views obtained on the main projection planes (see Fig. 1.1.1): 7 - front view (main view); 2 - top view; 3 - left side view; 4 - right side view; 5 - bottom view; b - rear view. In practice, three views are more widely used: front view, top view and left view.

The main views are usually located in a projection relationship with each other. In this case, the name of the views on the drawing does not need to be inscribed.

If any view is displaced relative to the main image, its projection connection with the main view is broken, then an “A” type inscription is made above this view (Fig. 1.2.1).

The direction of view should be indicated by an arrow marked with the same capital letter of the Russian alphabet as in the inscription above the view. The ratio of the sizes of the arrows indicating the direction of view should correspond to those shown in fig. 1.2.2.

If the views are in a projection relationship with each other, but are separated by any images or are located on more than one sheet, then an inscription of the “A” type is also made above them. An additional view is obtained by projecting an object or part of it onto an additional projection plane that is not parallel to the main planes (Fig. 1.2.3). Such an image must be performed in the case when any part of the object is not depicted without distorting the shape or size on the main projection planes.

An additional projection plane in this case can be located perpendicular to one of the main projection planes.

When an additional view is located in direct projection connection with the corresponding main view, it is not necessary to designate it (Fig. 1.2.3, a). In other cases, an additional view should be marked on the drawing with an inscription of type "A" (Fig. 1.2.3, b),

and for the image associated with the additional view, you need to put an arrow indicating the direction of the view, with the corresponding letter designation.

The secondary view can be rotated while maintaining the position adopted for this item in the main image. In this case, a sign must be added to the inscription (Fig. 1.2.3, c).

A local view is an image of a separate, limited place on the surface of an object (Fig. 1.2.4).

If a local view is located in direct projection connection with the corresponding images, then it is not indicated. In other cases, local views are designated similarly to additional types; a local view can be limited by a cliff line (“B” in Fig. 1.2.4).

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Topic 3. Construction of the third type of object according to two data

First of all, you need to find out the shape of the individual parts of the surface of the depicted object. To do this, both given images must be viewed simultaneously. It is useful to keep in mind which surfaces correspond to the most common images: triangle, quadrilateral, circle, hexagon, etc.

On the top view in the form of a triangle, they can be depicted (Fig. 1.3.1, a): triangular prism 1, triangular 2 and quadrangular 3 pyramids, cone of revolution 4.

An image in the form of a quadrangle (square) can be seen from above (Fig. 1.3.1, b): a cylinder of rotation 6, a triangular prism 8, quadrangular prisms 7 and 10, as well as other objects limited by planes or cylindrical surfaces 9.

The shape of a circle can be seen from above (Fig. 1.3.1, c): ball 11, cone 12 and cylinder 13 of rotation, other surfaces of rotation 14.

The top view in the form of a regular hexagon has a regular hexagonal prism (Fig. 1.3.1, d), which limits the surfaces of nuts, bolts and other parts.

Having determined the shape of individual parts of the surface of an object, one must mentally imagine their image in the left view and the entire object as a whole.

To construct the third view, it is necessary to determine which lines of the drawing should be taken as the base for reporting the dimensions of the object image. As such lines, axial lines are usually used (projections of the planes of symmetry of the object and projections of the planes of the bases of the object). Let's analyze the construction of the view on the left using an example (Fig. 1.3.2): according to the main view and the top view, construct a left view of the depicted object.

Comparing both images, we establish that the surface of the object includes surfaces: regular hexagonal 1 and quadrangular 2 prisms, two cylinders 3 and 4 of rotation and a truncated cone 5 of rotation. The object has a frontal plane of symmetry Ф, which is convenient to take as the basis for reporting the dimensions of the width of individual parts of the object when constructing its view on the left. The heights of individual sections of the object are measured from the lower base of the object and are controlled by horizontal communication lines.

On fig. 1.3.3, a left-hand view of an object is constructed, the surface of which is formed by the surface of a vertical cylinder of revolution, with a T-shaped notch in its upper part and a cylindrical hole with a frontally projecting surface. The plane of the lower base and the frontal plane of symmetry F were taken as base planes. M and im symmetrical. When constructing the third type, the symmetry of the object with respect to the F plane was taken into account.

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The main element in solving graphic problems in engineering graphics is the drawing. A drawing is a graphic representation of objects or their parts. The drawings are made in strict accordance with the rules of projection in compliance with the established requirements and conventions. Moreover, the rules for depicting objects or their constituent elements in the drawings remain the same in all industries and construction.

The image of the object in the drawing should be such that it can be used to establish its shape as a whole, the shape of its individual surfaces, the combination and relative position of its individual surfaces. In other words, the image of an object should give a complete picture of its shape, device, dimensions, as well as the material from which the object is made, and in some cases include information about the methods of making the object. A characteristic of the size of the object in the drawing and its parts are their dimensions, which are applied to the drawing. The image of objects in the drawings is performed, as a rule, "on a given scale.

Images of objects in the drawing should be placed so that its field is evenly filled. The number of images in the drawing should be sufficient to obtain a complete and unambiguous idea of it. At the same time, the drawing should only have required amount images, it should be minimal, i.e. the drawing should be concise and contain a minimum amount of graphic images and text sufficient for free reading of the drawing, as well as its production and control.

The visible contours of objects and their faces in the drawings are made with a solid thick main line. The necessary invisible parts of the object are performed using dashed lines. If the depicted object has constant or regularly changing cross-sections, is performed on the required scale and does not fit on the drawing field of a given format, it can be shown with breaks.

The rules for constructing images on drawings and drawing up drawings are given and regulated by a set of standards " unified system design documentation" (ESKD).

Image on drawings can be done different ways. For example, using rectangular (orthogonal) projection, axonometric projections, linear perspective. When performing engineering drawings in engineering graphics, the drawings are performed using the rectangular projection method. The rules for depicting objects, in this case, products, structures or corresponding constituent elements in the drawings, are established by GOST 2.305-68.

When constructing images of objects by the method of rectangular projection, the object is placed between the observer and the corresponding projection plane. For the main projection planes, six faces of the cube are taken, inside which the depicted object is located (Fig. 1.1.1, a). Faces 1,2 and 3 correspond to the frontal, horizontal and profile projection planes. The faces of the cube with the images obtained on them are combined with the plane of the drawing (Fig. 1.1.1, b). In this case, face 6 can be placed next to face 4.

The image on the frontal projection plane (on face 1) is considered the main one. The object is positioned relative to the frontal plane of projections so that the image gives the most complete idea of the shape and size of the object, carries the most information about it. This image is called the main image. Depending on their content, images of objects are divided into types, sections, sections.

The image of the visible part of the surface of the object facing the observer is called the view.

The main views are usually located in a projection relationship with each other. In this case, the name of the views on the drawing does not need to be inscribed.

If any view is displaced relative to the main image, its projection connection with the main view is broken, then an “A” type inscription is made above this view (Fig. 1.2.1).

An additional projection plane in this case can be located perpendicular to one of the main projection planes.

and for the image associated with the additional view, you need to put an arrow indicating the direction of the view, with the corresponding letter designation.

The secondary view can be rotated while maintaining the position adopted for this item in the main image. In this case, a sign must be added to the inscription (Fig. 1.2.3, c).

A local view is an image of a separate, limited place on the surface of an object (Fig. 1.2.4).

If the local view is located in direct projection connection with the corresponding images, then it is not indicated. In other cases, local views are designated similarly to additional types; a local view can be limited by a cliff line (“B” in Fig. 1.2.4).

On the top view in the form of a triangle, they can be depicted (Fig. 1.3.1, a): triangular prism 1, triangular 2 and quadrangular 3 pyramids, cone of revolution 4.

The shape of a circle can be seen from above (Fig. 1.3.1, c): ball 11, cone 12 and cylinder 13 of rotation, other surfaces of rotation 14.

The top view in the form of a regular hexagon has a regular hexagonal prism (Fig. 1.3.1, d), which limits the surfaces of nuts, bolts and other parts.

Having determined the shape of individual parts of the surface of an object, one must mentally imagine their image in the left view and the entire object as a whole.

The image of an object mentally dissected by one or more planes is called a cut. Mental dissection of an object refers only to this section and does not entail changes in other images of the same object. The section shows what is obtained in the cutting plane and what is located behind it.

Sections are used to depict the internal surfaces of an object in order to avoid a large number dashed lines that can overlap each other with a complex internal structure of the object and make it difficult to read the drawing.

To make a cut, you must: mentally draw a cutting plane in the right place on the object (Fig. 1.4.1, a); mentally discard the part of the object located between the observer and the cutting plane (Fig. 1.4.1, b), project the remaining part of the object onto the corresponding projection plane, perform the image either in place of the corresponding view, or in the free field of the drawing (Fig. 1.4.1 , in); shade a flat figure lying in a cutting plane; if necessary, give the designation of the section.

Depending on the number of secant planes, the cuts are divided into simple - with one secant plane, complex - with several secant planes.

Depending on the position of the cutting plane relative to the horizontal projection plane, the sections are divided into:
horizontal - cutting plane is parallel to the horizontal projection plane;
vertical - cutting plane is perpendicular to the horizontal projection plane;
inclined - the cutting plane makes an angle with the horizontal projection plane that is different from the right one.

A vertical section is called frontal if the cutting plane is parallel to the frontal projection plane, and profile if the cutting plane is parallel to the profile projection plane.

Complex cuts are stepped if the secant planes are parallel to each other, and broken, if the secant planes intersect with each other.

The cuts are called longitudinal if the cutting planes are directed along the length or height of the object, or transverse if the cutting planes are directed perpendicular to the length or height of the object.

Local incisions are used to identify internal structure object in a separate limited place. The local section is highlighted in the view by a solid wavy thin line.

The rules provide for the designation of cuts.

The position of the cutting plane is indicated by an open section line. The start and end strokes of the section line must not cross the contour of the corresponding image. On the initial and final strokes, you need to put arrows indicating the direction of the gaze (Fig. 1.4.2). Arrows should be applied at a distance of 2 ... 3 mm from the outer end of the stroke. With a complex cut, the strokes of an open section line are also carried out at the kinks of the section line.

Near the arrows indicating the direction of view from outside the angle formed by the arrow and the stroke of the section line, capital letters of the Russian alphabet are applied on the horizontal line (Fig. 1.4.2). Letter designations are assigned in alphabetical order without repetition and without gaps, with the exception of the letters I, O, X, b, s, b.

The cut itself must be marked with an inscription of the type "A - A" (always in two letters, through a dash).

If the cutting plane coincides with the plane of symmetry of the object, and the cut is made in the place of the corresponding view in the projection connection and is not separated by any other image, then for horizontal, vertical and profile cuts it is not necessary to mark the position of the cutting plane and the cut should not be accompanied by an inscription. On fig. 1.4.1 the frontal section is not marked.

Simple oblique cuts and complex cuts are always indicated.

Consider typical examples of the construction and designation of cuts in the drawings.

On fig. 1.4.3 made a horizontal section "A - A" in place of the top view. A flat figure lying in a secant plane, - figure sections are shaded, and visible surfaces,

located under the cutting plane, are limited by contour lines and are not shaded.

On fig. 1.4.4, a profile section is made in place of the left view in projection connection with the main view. The cutting plane is the profile plane of symmetry of the object, so the cut is not indicated.

On fig. 1.4.5, a vertical section "A - A" is made, obtained by a secant plane that is not parallel to either the frontal or profile projection planes. Such sections can be built in accordance with the direction indicated by the arrows (Fig. 1.4.5), or placed in any convenient location drawing, as well as with a rotation to the position corresponding to that adopted for this subject in the main image. In this case, the sign O is added to the section designation.

The inclined section is made in fig. 1.4.6.

It can be drawn in a projection relationship in accordance with the direction indicated by the arrows (Fig. 1.4.6, a), or placed anywhere in the drawing (Fig. 1.4.6, b).

In the same figure, in the main view, a local section is made showing through cylindrical holes on the base of the part.

On fig. 1.4.7, in place of the main view, a complex frontal stepped section is drawn, made by three frontal parallel planes. When performing a stepped cut, all parallel cutting planes are mentally combined into one, i.e., a complex cut is drawn up as a simple one. On a complex section, the transition from one cutting plane to another is not reflected.

When constructing broken sections (Fig. 1.4.8), one secant plane is placed parallel to any main projection plane, and the second secant plane is rotated to coincide with the first.

Together with the cutting plane, the section figure located in it is rotated and the cut is made in the rotated position of the section figure.

The connection of a part of a view with a part of a section in one image of an object according to GOST 2.305-68 is allowed. In this case, the boundary between the view and the section is a solid wavy line or a thin line with a break (Fig. 1.4.9).

If half of the view and half of the section are connected, each of which is a symmetrical figure, then the line separating them is the axis of symmetry. On fig. 1.4.10, four images of the part are made, and on each of them half of the view is connected to the half of the corresponding section. In the main view and the left view, the section is located to the right of the vertical axis of symmetry, and in the top and bottom views - to the right of the vertical or below the horizontal axis of symmetry.

If the contour line of the object coincides with the axis of symmetry (Fig. 1.4.11), then the boundary between the view and the section is indicated by a wavy line, which is drawn in such a way as to preserve the image of the edge.

Hatching of the section figure included in the section must be carried out in accordance with GOST 2.306-68. Non-ferrous, ferrous metals and their alloys are indicated in cross-section by hatching with solid thin lines with a thickness from S / 3 to S / 2, which are drawn parallel to each other at an angle of 45 ° to the lines of the drawing frame (Fig. 1.4.12, a). Hatching lines can be applied with an inclination to the left or right, but in the same direction on all images of the same part. If the hatching lines are drawn at an angle of 45° to the lines of the drawing frame, then the hatching lines can be placed at an angle of 30° or 60° (Fig. 1.4.12, b). The distance between parallel hatching lines is chosen in the range from 1 to 10 mm, depending on the hatching area and the need to diversify the hatching.

Non-metallic materials (plastics, rubber, etc.) are indicated by hatching by intersecting mutually perpendicular lines (hatching "in a cage"), inclined at an angle of 45 ° to the frame lines (Fig. 1.4.12, c).

Consider an example. Having completed the frontal section, we will connect half of the profile section with the half of the left view of the object given in Fig. 1.4.13, a.

Analyzing this image of the object, we come to the conclusion that the object is a cylinder with two through prismatic horizontal and two vertical internal holes,

of which one has the surface of a regular hexagonal prism, and the second has a cylindrical surface. The lower prismatic hole intersects the surface of the outer and inner cylinder, and the upper tetrahedral prismatic hole intersects the outer surface of the cylinder and the inner surface of the hexagonal prismatic hole.

The frontal section of the object (Fig. 1.4.13, b) is performed by the frontal plane of symmetry of the object and is drawn in place of the main view, and the profile section is made by the profile plane of the symmetry of the object, therefore, neither one nor the other needs to be designated. The left view and the profile section are symmetrical figures, their halves could be delimited by the axis of symmetry, if not for the image of the edge of the hexagonal hole coinciding with the axial line. Therefore, we separate the part of the view to the left of the profile section with a wavy line, depicting most incision.

The image of a figure obtained by mentally dissecting one or more planes, provided that only what is in the cutting plane is shown in the drawing, is called a section. The section differs from the section in that it depicts only what directly falls into the cutting plane (Fig. 1.5.1, a). The section, like the section, is a conditional image, since the figure of the section does not exist separately from the object: it is mentally torn off and depicted in the free field of the drawing. Sections are part of the section and exist as independent images.

Sections that are not part of the section are divided into removed (Fig. 1.5.1, b) and superimposed (Fig. 1.5.2, a). Preference should be given to rendered sections, which can be placed in a section between parts of the same image (Fig. 1.5.2, b).

According to the shape of the section, they are divided into symmetrical (Fig. 1.5.2, a, b) and asymmetrical (Fig. 1.5.1, b).

The contour of the rendered section is drawn with solid main lines, and the contour of the superimposed one is drawn with solid thin ones, and the contour of the main image at the location of the superimposed section is not interrupted.

The designation of sections in the general case is similar to the designation of cuts, i.e., the position of the cutting plane is displayed by the section lines, on which arrows are applied that give the direction of view and are designated by the same capital letters Russian alphabet. In this case, an inscription of the type "A - A" is made above the section (see Fig. 1.5.2, b).

For asymmetric superimposed sections or made in a gap in the main image, the section line with arrows is drawn, but they are not marked with letters (Fig. 1.5.3, a, b). Superimposed symmetrical section (see Fig. 1.5.2, a), symmetrical section made in the break of the main image (see Fig. 1.5.2, b), remote symmetrical section made along the trace of the secant plane (see Fig. 1.5 .1, a), are drawn up without drawing a section line.

If the cutting plane passes through the axis of the surface of revolution that bounds the hole or recess, then the contour of the hole or recess is drawn completely (Fig. 1.5.4, a).

If the cutting plane passes through a through non-circular hole and the section is obtained consisting of individual independent parts, then cuts should be applied (Fig. 1.5.4, b).

Inclined sections are obtained from the intersection of an object with an inclined plane, which makes an angle other than a right angle with the horizontal projection plane. In the drawing, inclined sections are performed according to the type of extended sections. The oblique section of an object must be built as a set of oblique sections of its constituent geometric bodies. The construction of inclined sections is based on the use of the method of replacing projection planes.

When drawing an oblique section, it is necessary to determine which surfaces that bound the object are cut by the cutting plane, and which lines are obtained from the intersection of these surfaces with this cutting plane. On fig. 1.5.5 the inclined section "A - A" is built. The cutting plane crosses the base of the object along a trapezoid, the inner and outer cylindrical surfaces - along ellipses, the centers of which lie on the main vertical axis of the object. Reading the shape of an oblique section is made easier if you plot the plan view of the oblique section as an overlay section.

When making drawings, in some cases it becomes necessary to construct an additional separate image of any part of the object that requires explanations regarding the shape, dimensions or other data. Such an image is called a callout. It is usually performed enlarged. A callout can be laid out as a view or as a section.

When constructing a remote element, the corresponding place in the main image is marked with a closed solid thin line, usually an oval or a circle, and denoted capital letter Russian alphabet on the shelf of the leader line. The external element is recorded according to type A (5: 1). On fig. 1.6.1 shows an example of a remote element. It is placed as close as possible to the corresponding place on the image of the subject.

When performing various images of an object, GOST 2.305-68 recommends using some conventions and simplifications, which, while maintaining the clarity and clarity of the image, reduce the amount of graphic work.

If the view, section or section are symmetrical figures, then only half of the image or slightly more than half of the image can be drawn, limiting it with a wavy line (Fig. 1.7.1).

Simplification is allowed to depict cut lines and transition lines; instead of curved curves, arcs of a circle and straight lines are drawn (Fig. 1.7.2, a), and a smooth transition from one surface to another should be shown conditionally (Fig. 1.7.2, b) or not shown at all (Fig. 1.7.2, c ).

It is allowed to depict a slight taper or slope enlarged. On those images where the slope or taper is not clearly detected, only one line is drawn, corresponding to the smaller size of the element with a slope (Fig. 1.7.3, a) or the smaller base of the cone (Fig. 1.7.3, b).

When making cuts, non-hollow shafts, handles, screws, dowels, and rivets are shown undissected. Balls are always depicted uncut.

Elements such as spokes, thin walls, stiffeners are shown unshaded in the section if the cutting plane is directed along the axis or long side of such an element (Fig. 1.7.4). If there is a hole or recess in such elements, then a local incision is made (Fig. 1.7.5, a).

Holes located on a round flange and not falling into the cutting plane are shown in section as if they were in the cutting plane (Fig. 1.7.5, b).

To reduce the number of images, it is allowed to depict the part of the object located between the observer and the cutting plane as a thickened dash-dotted line (Fig. 1.7.6). In more detail, the rules for the image of objects are set out in GOST 2.305-68.

To build a visual image of the object, we use axonometric projections. It can be done according to its complex drawing. Using Fig. 1.3.3, let's build a standard rectangular isometry of the object depicted on it. Let's use the given distortion coefficients. Let's take the location of the origin of coordinates (point O) - in the center of the lower base of the object (Fig. 1.8.1). Having drawn the isometric axes and set the image scale (MA 1.22: 1), we mark the centers of the circles of the upper and lower bases of the cylinder, as well as the circles that bound the T-shaped cutout. We draw ellipses, which are isometries of circles. Then we draw lines parallel to the coordinate axes that limit the cutout in the cylinder. Isometry of the line of intersection of a through cylindrical hole,

whose axis is parallel to the Oy axis with the surface of the main cylinder, we build on separate points, using the same points (K, L, M and symmetrical to them) as when constructing the view on the left. Then we remove the auxiliary lines and finally outline the image, taking into account the visibility of individual parts of the object.

To construct an axonometric image of an object, taking into account the cut, we will use the conditions of the problem, the solution of which is shown in Fig. 1.4.13, a. On a given drawing, to build a visual image, we mark the position of the projections of the coordinate axes and on soy Oz we mark the centers 1,2, ..., 7 of the figures of the object located in the horizontal planes G1", T "2, ..., G7", this is the upper and the lower base of the subject, the base internal holes. To transfer the internal forms of the object, we will cut out 1/4 of the part of the object coordinate planes xOz and yOz.

The flat figures obtained in this case have already been built on a complex drawing, since they are halves of the frontal and profile sections of objects (Fig. 1.4.13, b).

We begin the construction of a visual image by drawing the axes of dimetry and indicating the scale MA 1.06: 1. On the z axis, we mark the position of the centers 1, 2, ..., 7 (Fig. 1.8.2, a); we take the distances between them from the main view of the object. Through the marked points we draw the axes of dimetry. Then we build in dimetry the figures of the section, first in the xOz plane, and then in the yOz plane. We take the dimensions of the coordinate segments from the integrated drawing (Fig. 1.4.13); at the same time, the dimensions along the y-axis are halved. We carry out hatching of sections. The angle of inclination of hatching lines in axonometry is determined by the diagonals of parallelograms built on axonometric axes, taking into account the distortion coefficients. On fig. 1.8.3, but an example of choosing the direction of hatching in isometry is given, and in fig. 1.8.3, b - in dimetry. Next, we build ellipses - the dimetry of circles located in horizontal planes (see Fig. 1.8.2, b). We spend contour lines outer cylinder, inner vertical holes, we build the base of these holes (Fig. 1.8.2, c); draw visible lines intersections horizontal holes with outer and inner surfaces.

Then we remove the auxiliary construction lines, check the correctness of the drawing and outline the drawing with lines of the required thickness (Fig. 1.8.2, d).

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