The image of a half section in the drawing. Sections in drawings. Construction of sections and cuts in drawings

Details Category: Engineering graphics

SECTIONS

If the part is hollow or has an internal structure in the form of holes, recesses, etc., invisible contours are shown in the views with dashed lines. With a complex internal design of the part, a large number of dashed lines makes it difficult to read the drawing and often leads to an inaccurate idea of ​​the shape of the part. This can be avoided by using conditional images - cuts.

A cut is an image of an object obtained by mentally dissecting it with one or more cutting planes. In this case, the part of the object located between the observer and the cutting plane is mentally removed, and on the projection plane what is obtained in the cutting plane (the figure of the section of the object by the cutting plane) and what is located behind it is depicted.

When cut, the internal contour lines, depicted in the drawing as dashed lines, become visible and are depicted as solid main lines.

Depending on the number of cutting planes, cuts are divided into simple (with one cutting plane) and complex (with several cutting planes).

Depending on the position of the cutting plane relative to the horizontal projection plane, the sections are divided into horizontal, vertical and oblique.

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

In all the examples below, it is conditionally assumed that the objects are metal, and for graphic symbol material in the sections of the part is hatched with thin lines with an inclination at an angle of 45 ° to the lines of the drawing frame.

Hatching on all images of one part is done in the same direction (with right or left tilt).

SIMPLE CUT - VERTICAL AND HORIZONTAL

A vertical section is a section formed by a cutting plane perpendicular to the horizontal projection plane.

A vertical cut is called frontal if the cutting plane is parallel to the frontal projection plane (Fig. 258), and profile if the cutting plane is parallel to the profile projection plane (Fig. 259).

An example of the formation of a frontal cut of a part is given in fig. 258. The detail is dissected by plane A, parallel to the frontal plane of projections. The part of the part located in front of the cutting plane is mentally removed, and the remaining part, completely depicted in the place of the main view, is a frontal section of the part. All contour lines located in the cutting plane and behind it are shown as visible in the section. An example of the formation of a profile cut is given in fig. 259. The part is cut by a cutting plane parallel to the profile plane of projections. The profile section resulting in this case is located in the place of the view on the left.

Horizontal sections are called sections formed by cutting planes parallel to the horizontal projection.

On fig. 260 the detail is cut by a horizontal plane P, parallel to the horizontal projection plane. The upper part of the part is mentally removed, and the remaining lower part is projected onto the horizontal projection plane. Horizontal, frontal and profile sections can be placed in place of the corresponding main views.

DESIGNATION OF SECTIONS

If the cutting plane coincides with the plane of symmetry of the object as a whole and the cut is located in a projection connection with the view and is not separated by any other images, then when performing horizontal, frontal and profile cuts, the position of the cutting plane is not marked on the drawing and the cut is not accompanied by an inscription (see Fig. 258, 259 and 260).

In other cases, the position of the cutting plane is indicated in the drawing by an open line and arrows indicating the direction of view, and a corresponding inscription is made above the cut, indicating the cutting plane used to obtain this cut.

On fig. 261 two vertical sections are made: frontal (A-A) (Fig. 261, a) and profile B) (Fig. 261, c), the secant planes of which do not coincide with the planes of symmetry of the part as a whole. Therefore, the drawing indicates the position of the cutting planes and the corresponding cuts are accompanied by inscriptions.

The strokes of the open line must not cross the outline of the image. On the strokes of the section line, arrows are placed perpendicular to them, indicating the direction of view. The arrows are applied at a distance of 2-3 mm from the outer end of the stroke of the section line.

The dimensions of the arrow are shown in fig. 262.

Near each arrow the same capital letter of the Russian alphabet is applied.

The inscription above the section is underlined by a solid thin line and contains two letters that indicate the cutting plane, written through a dash (Fig. 261, b).

On one image, it is allowed to connect part of the view and part of the section. Hidden contour lines on the connected parts of the view and section are usually not shown.

If the view and section are symmetrical figures (Fig. 263), then you can connect half of the view and half of the section, separating them with a dash-dotted thin line, which is the axis of symmetry.

Part of the section is placed to the right (Fig. 263, a) or below the axis of symmetry (Fig. 263, b), which separates part of the view from part of the section.

When connecting the symmetrical parts of the view and the section, if the projection of a line, for example, an edge (Fig. 264), coincides with the axis of symmetry, then the view is separated from the section by a solid wavy line drawn to the left (Fig. 264, a) or to the right (Fig. 264). 264, b) axes of symmetry.

When connecting on the same image a view and a section representing asymmetrical figures, a part of the view is separated from the part of the section by a solid wavy line (Fig. 264, c).

The vertical sections shown in fig. 258 and 259 are obtained by applying cutting planes parallel to either the frontal or profile projection planes. In practice, there are cases when a vertical cut is made by a cutting plane that is neither parallel nor frontal. nor the profile planes of the projections (Fig. 265), in this case the section is built and located in accordance with the direction of view indicated by the arrows on the section line.

It is allowed to rotate the section to a position corresponding to the position adopted for the object on the main image (Fig. 265). In this case, the word

"turned".

SLOPED SECTION

If the part has oblique hollow elements, an oblique cut is used.

An oblique cut is called a cut by a plane that makes an angle with the horizontal projection plane that is different from the right one. An oblique cut is projected onto an additional plane parallel to the secant, aligning it with the plane of the drawing.

An example of an oblique cut is shown in fig. 266. The position of the cutting plane is marked by a section line with arrows indicating the direction of view.

Inclined cuts should be located in accordance with the direction of view indicated by the arrows on the section line (Fig. 266, b). It is allowed to place oblique cuts anywhere in the drawing field (Fig. 267) outside the projection connection with the view, but taking into account the direction of view. If necessary, inclined cuts can be rotated (section A-A in Fig. 267).

LOCAL SECTIONS

If you want to find out the design of the product only in a separate limited place, you can apply a section called local. The line limiting the local incision is made by a solid wavy line.

On fig. 268, and examples of local cuts are made, thanks to which the shape of some elements of the part is revealed.

If a local cut is made on a part of an object that is a body of revolution (Fig. 268, b) and, therefore, depicted with an axial line, then a local cut with a view can be separated by this axial line.

COMPLEX CUTS - STEP AND BROKEN

In addition to simple cuts, when one plane is used, complex cuts are used with two or more cutting planes.

Complex cuts are divided into stepped and broken.

A complex cut formed by two or more secant parallel planes is called a stepped cut. Stepped cuts can be horizontal, frontal and profile.

An example of a stepped horizontal section is shown in fig. 269, a. The two cutting planes are parallel to the horizontal projection plane. A drawing of a part with such a section is shown in Fig. 269b. The direction of the cutting planes is indicated by open lines (section lines). The start and end strokes of the section line have arrows with the same letter. The section line also has kinks, showing the places of transition from one cutting plane to another. The kinks of the section line are made with the same thickness as the strokes of the open line. The arrows indicate the direction of view.

When performing a stepped cut, the secant planes are combined into one plane, and the stepped cut is drawn up as a simple one. The lines dividing two sections from each other at the places of inflections on a stepped section are not indicated.

On fig. 270, a shows an example of a frontal stepped section made by three cutting planes, the position of which is marked in the top view by a stepped section line (Fig. 270, c).

It is allowed to place complex cuts outside the projection connection with other images (Fig. 270, b).

Profile stepped cuts are performed similarly.

Broken cuts are cuts obtained by cutting an object not with parallel, but with intersecting planes (Fig. 271). In this case, one secant plane is conditionally rotated near the line of intersection of the secant planes until it coincides with another secant plane parallel to any of the main projection planes, i.e., a broken cut is placed in the place of the corresponding view.

On fig. 271 the lever is dissected by two intersecting cutting planes, one of which is the frontal plane. The secant plane, located to the left, is mentally rotated around the line of intersection of the secant planes until it coincides with the frontal secant plane. Together with the cutting plane, the figure of the section of the part located in it rotates. The front view shows an image of the dissected part after performing the indicated rotation. On fig. 271 for clarity, lines of communication and the position of a part of the part after rotation are plotted. These constructions are not shown in the drawing.

A broken cut can be obtained by cutting through three intersecting planes (Fig. 272).

When performing a broken cut, when one cutting plane is rotated to coincide with another, the elements of the object located behind it are not rotated: they are depicted as they are projected onto the corresponding projection plane, provided that the cut is not performed. Ledge B (Fig. 273, a), located behind the rotated cutting plane, does not participate in the rotation: its images are made on the drawing in a projection relationship.

An exception to this rule may be cases where the elements of the object are located symmetrically with respect to the rotating cutting plane. In these cases, such elements of the object are rotated along with the cutting plane. The lever (Fig. 273, b) has two lugs located symmetrically with respect to the secant plane. The tab rotates with the cutting plane when it is aligned with the profile plane.

The direction of rotation of the cutting plane may not coincide with the direction of view (Fig. 273, c).

The theoretical material that gives the concepts of views, sections and sections is considered in GOST 2305-81. Before proceeding with the execution of the drawings, it is necessary to learn the terms and definitions given in GOST 2305-81.

Projection - the image of an object on the projection plane with all visible and invisible details.

A view is an image of the visible part of the surface of an object. Types are divided into three groups: basic, additional, local.

The main views are the types of the object obtained by projecting into place the main projection planes established by GOST 2305-81 (Fig. 11).

Figure 11

There are six main types in total:

1) front view (main). Projection onto p 2 ;

2) top view. Projection onto p 1 ;

3) view from the left. Projection on p 3 ;

4) right side view. Projection on p 3 ;

5) bottom view. Projection onto p 2 ;

6) rear view. Projection onto p 1 .

In practice, the first three types are more often used, the remaining three - if necessary. It is quite rare to find a detail that requires all six types to be completed.

When drawing a part, it is important to choose main view(front view). When choosing the main view, it must be taken into account that it should give the most complete idea of ​​the shape of the model. The top and left views should be located in a projection relationship with the front view, but it is not necessary to draw projection axes, communication lines and a complex drawing constant in the drawing.

An additional view is an image on a plane that is not parallel to any of the main planes, but perpendicular to one of them (Fig. 12a). In the drawing, on the projection of the detail plane, to which the additional view is perpendicular, the direction of view is marked with an arrow and a capital letter of the Russian alphabet is placed next to the arrow. The additional view itself must have a title with the corresponding letter, for example: "ViewA".

Figure 12

A local view is an image of a limited part of an object (Fig. 12b). Part of the subject is limited by a thin wavy line.

In addition to the image of the visible part of the object, it often becomes necessary to show the inside of the object. For this purpose, cuts and sections are made in the drawings.

A cut is a mental dissection of an object by one or more planes. The section shows what is obtained in the cutting plane and what is located behind it. Sections are divided into simple and complex.

Simple cuts - the cutting plane is parallel to some basic projection plane. The incision can be horizontal, frontal, profile, vertical and transverse.

If the part is symmetrical, then half of the view and half of the simple cut is performed. Such a cut is called combined- combination of part of the view and part of the section (Fig. 13 a, b).

When combined, the dividing line is the axis of symmetry (i.e., a dash-dotted line). If on the image of the object the axis of symmetry coincides with the edge, then to reveal the design of the detail, the line is drawn a little more or a little less than half of the cut (depending on where the edge is: in the form or in the cut). The boundary between the view and the section in this case is a thin wavy line (Fig. 13 b).

A local cut is a cut made on a limited part of the part (Fig. 13 c). Limited to a thin wavy line.

Figure 13

Complex cuts - the part is cut by several planes. There are two types of complex cuts: broken and stepped.

Broken cut - there are usually two secant planes, and these planes intersect at an angle to each other (Fig. 14 a).

A feature of the broken cut is the combination of cutting planes. In connection with this feature, the view on which the broken cut is made does not always coincide with the visible contour, sometimes the visible contour is distorted.

On one of the views, a line of a broken section is indicated - the exit point of the secant planes and the place of their intersection. To indicate the line of a broken cut, an open line is used. Arrows are attached to the strokes of this line to indicate the direction of view and the letter designation of the cut. The view on which the broken section is made is titled with the letters of an open line (for example, "A-A"). The intersection of the planes on the section does not give any additional line or border.

Figure 14

Stepped cut - there are at least two secant planes, and they are parallel to each other (Fig. 14 b). Just as when performing a broken cut, the cut line is indicated. The transition point of the cut from one plane to another looks like steps in the drawing (hence the name of the cut). In the section, the place of transition from one plane to another is not indicated in any way. Just like a polygonal section, a stepped section must have a title in the form of a letter designation of the section line (for example, "B-B").

A section is an image of a figure obtained by mentally dissecting an object with one or more planes. The section shows only what falls into the cutting plane (Fig. 15). The section can be superimposed - if the image of the object is combined with the view; or remote - if the image of the section is taken out of the view of the part. When performing a detailed section, it is necessary to designate the line of the section, and the section itself must have a title.

Figure 15

GOST 2305-81 contains a number of features and conventions that must be taken into account when making cuts and sections.

If the cutting plane is directed along a thin wall or stiffener, then the wall cut by this plane is shown unhatched and is limited by a solid line of the visible contour. If there is a local drilling or recess in such elements of the part, then a local cut is made to open it (Fig. 16).

Figure 16

A cross section of a thin wall is depicted according to the general rules, i.e. the part that falls into the cutting plane is shaded.

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 in the section is shown in full. In the event that the cutting plane passes through a non-circular hole and the section is obtained consisting of separate parts, not a section should be used, but a cut.

The image of an object mentally dissected by one or more planes is called incision. 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, it is necessary: ​​in the right place of the object, mentally draw a cutting plane (Fig. 173, a); mentally discard the part of the object located between the observer and the cutting plane (Fig. 173, b) project the rest 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. 173, c); 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.

Rice. 174

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. 174). 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 the outside of the angle formed by the arrow and the stroke of the section line, capital letters of the Russian alphabet are applied on a horizontal line (Fig. 174). Letter designations are assigned in alphabetical order without repetitions and without gaps, except for letters And, 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. 173 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. 175 made a horizontal section "A - A" in place of the top view. flat figure, lying in the secant plane - the figure of the section - is shaded, and the visible surfaces located

Rice. 176

below the cutting plane, bounded by contour lines and not hatched.

On fig. 176, 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. 177, 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 cuts can be built in accordance with the direction indicated by the arrows (Fig. 177), or placed in any convenient place on the drawing, as well as rotated to the position corresponding to that adopted for this object in the main image. In this case, the sign O is added to the section designation.

The inclined section is made in fig. 178. It can be drawn in

projection connection in accordance with the direction indicated by the arrows (Fig. 178, a), or placed anywhere in the drawing (Fig. 178, 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. 179, 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. 180), one secant plane is placed parallel to any main projection plane, and the second secant plane is rotated to coincide with

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. 181).

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. 182, four images of the detail 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. 183), 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 of S/3 before S/2, which are carried out parallel to each other at an angle of 45 ° to the lines of the drawing frame (Fig. 184, 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 hatch lines are drawn at an angle of 45 ° to the lines of the drawing frame, then you can place the hatch lines at an angle of 30 ° or 60 ° (Fig. 184, 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. 184, in).

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. 185, 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 crosses the surface of the outer and inner cylinder, and the upper tetrahedral prismatic hole crosses the outer surface of the cylinder and inner surface hexagonal prismatic hole.

The frontal section of the object (Fig. 185, 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 of the section.

The inner outline of hollow objects in the drawings can be shown with dashed lines, but the shape of the parts often requires a significant number of such lines, which, intersecting with the contour lines and with each other, make it difficult to understand the drawing. To avoid this, to more clearly show the internal structure of the part, images are used, called a cut.

Incision- this is an image of an object mentally dissected by one or more planes. Mental dissection applies only to this image and does not entail changes in other images. The section shows what is in the cutting plane (hatching is superimposed on this part of the image, in accordance with the material from which the part is made) and that part of the part that is located behind the cutting plane.

When making cuts in drawings:

1. Invisible internal outlines, represented by dashed lines, are outlined with solid main lines.
2. Solid main lines depicting the elements of the part located on the part of the part located in front of the cutting plane are not drawn.
3. The section figure included in the section is shaded.
4. Mental dissection of an object should apply only to this section and does not entail changes in other images of the same object.

Depending on the number of cutting planes, the cuts are divided into simple and complex.

Simple is called a cut with one secant plane.

complex called a cut with two or more secant planes.

Depending on the position of the cutting plane relative to the horizontal projection plane, the sections are divided into vertical, horizontal and oblique.

Complex cuts are divided into broken and stepped.

Vertical cuts (frontal)

Frontal cut - an image obtained as a result of a mental dissection of a part by a cutting plane parallel to the frontal plane of projections, and consisting of a sectional figure and an image of a part of the part located behind the cutting plane.

The part is placed in a system of projection planes (V, H or V, H, W) and is mentally dissected by a secant plane parallel to the frontal projection plane. The figure of the section and what is located behind the cutting plane are projected onto the plane V, obtaining an image of the frontal section

Vertical sections (profile)

Profile cut called an image obtained by mentally dissecting a part with a cutting plane parallel to the profile plane of projections, and consisting of a section figure and an image of a part of the part located behind it.

The part is placed in the system of projection planes (V, H or V, H, W) and mentally cut by a secant plane parallel to the profile projection plane. The section figure and what is located behind the cutting plane are projected onto the W plane, obtaining an image of the profile section.

horizontal section

horizontal section - an image obtained by mentally dissecting a part with a cutting plane parallel to the horizontal plane of projections, and consisting of a section figure and an image of a part of the part located behind the cutting plane.

The section figure and what is located behind the cutting plane are projected onto the H plane, obtaining an image of a horizontal section.

oblique cut

Oblique cuts - the cutting plane makes an angle other than a right angle with the horizontal projection plane. An oblique cut is recommended to be used to display the shape of an element (elements) of a part or part of it in the following cases:

An element of a part or part of it has a plane of symmetry, which makes an acute angle with the frontal (horizontal) plane of projections. The secant plane of the cut is combined with the specified plane of symmetry;

The axes of adjacent elements (holes) are parallel and located in the same plane, perpendicular to the horizontal (frontal) projection plane and inclined to another projection plane. The cutting plane is combined with the axes of the elements (holes);

The general shape of the prismatic element of the part makes an acute angle with the horizontal projection plane. The secant plane of the section is drawn perpendicular to the line of the element.

An inclined section is built and placed on the drawing in accordance with the direction indicated by the arrows on the section line. It is allowed to place these cuts anywhere in the drawing field, and also rotate them to the position corresponding to that adopted for this part on the main image. In this case, the sign "rotated" should be added to the inscription above the section.

local cut

Local called incision , which serves to clarify the device of a part in a separate limited place.

The local section is limited in the view by a wavy line or a line with a break. These lines must not overlap with any other lines in the image.

When performing local cuts in the view, they are not indicated.

stepped cut

stepped cut It is formed when a part is cut by two or more parallel planes. When constructing an image, the secant planes are conditionally combined. Just like simple cuts, they can be frontal, horizontal and profile.

broken cut

broken cut formed when a part is cut by intersecting planes. When constructing an image, the secant planes are conditionally rotated until they coincide in one plane, while the direction of rotation may not coincide with the direction of view.

Cutting plane (cutting planes) and consisting of an image of a sectional figure and that part of the part that is located behind the cutting plane (cutting planes).

Rice. 153. Drawing of the first steam locomotive in Russia of the father and son of the Cherepanovs

Rice. 154. Classification of cuts

In Russia, cuts have long been used to display the internal shape of products. Images of cuts are found on the drawings of I. I. Polzunov, I. P. Kulibin, E. A. n M. E. Cherepanovs and other mechanics (Fig. 153).

Depending on the number of cutting planes, there are simple (obtained as a result of mental dissection of the part by one cutting plane) and complex (obtained as a result of mental dissection of the part by several secant planes) cuts (Fig. 154).

Consider simple cuts.

Frontal cut - an image obtained as a result of a mental dissection of a part by a cutting plane parallel to the frontal projection plane, and consisting of a section figure and an image of a part of the part located behind the cutting plane.

The part is placed in a system of projection planes (V, H or V, H, W) and is mentally dissected by a secant plane parallel to the frontal projection plane. The figure of the section and what is located behind the cutting plane are projected onto the plane V, obtaining an image of the frontal section (Fig. 155).

Profile cut called an image obtained by mentally dissecting a part with a cutting plane parallel to the profile plane of projections, and consisting of a section figure and an image of a part of the part located behind it.

The part is placed in the system of projection planes (V, H or V, H, W) and mentally cut by a secant plane parallel to the profile projection plane. The section figure and what is located behind the cutting plane are projected onto the W plane, obtaining an image of the profile section (Fig. 156).

horizontal section - an image obtained by mentally dissecting a part with a cutting plane parallel to the horizontal plane of projections, and consisting of a section figure and an image of a part of the part located behind the cutting plane.

The section figure and what is located behind the cutting plane are projected onto the H plane, obtaining an image of a horizontal section (Fig. 157).

The construction of cuts does not entail changes in other types, since all actions (dissection of a part by a plane, conditional removal of a part of a part that is in front of the cutting plane, projection) are carried out mentally.

Cuts allow you to reduce the number of invisible contour lines that make it difficult to read the complex shape of the part.

Rice. 155. Frontal cut

Rice. 156. Profile cut

Rice. 157. Horizontal cut

GOST 2.305-68 establishes the rules for making and designating cuts: if the cutting plane coincides with the plane of symmetry of the part, and the images of the drawing are in projection relationship, then the cut is not indicated in the drawing (see Fig. 157);

if the cutting plane does not coincide with the plane of symmetry (horizontal section B - B) or the image of the section is not in projection connection with the corresponding images of the drawing, then the position of the cutting plane is indicated on the drawing by an open line (thickness from S to 5/2). Arrows are drawn perpendicular to the open line, indicating the direction of view, which are applied at a distance of 2-3 mm from the outer end of the line. The open line must not cross the contours of the image. On the outside of the arrows, the letter designation of the cuts is applied. The image of the section is marked with an inscription like "A - A" (Fig. 158).

Consider complex cuts.

stepped called a complex cut formed by two or more secant parallel planes (Fig. 159, a). Stepped cuts can be frontal, profile and horizontal.

Rice. 158. Designation of cuts

Rice. 159. Stepped (a) and broken (b) cuts

The above rules apply to all simple cuts.

Rice. 160. Image of stiffeners on cuts

Broken a cut is a complex cut formed by two intersecting planes (Fig. 159, b).

On sections, thin walls, stiffeners, spokes are shown not shaded if the cutting plane runs along the axis or long side of the part element (Fig. 160).