Classification of cuts
Cuts
Let us recall the definition given in section 1.1: cut is an image of a part mentally dissected by one or more planes. The section shows everything that is in the cutting plane and located behind it.
Incisions are classified according to several criteria.
According to the type of cutting surface: if the cutting surface is a plane, then the cut is called flat, if cylindrical (Fig. 9), the section is called curvilinear, and the cylindrical surface then unfolds into a plane. This is evidenced by the symbol, the dimensions of which are shown in Fig. 10, b.
Complex cuts are used in cases where a simple cut does not fully reveal the shape of the part and its elements, namely holes located in different planes.
Complex flat cuts based on the position of cutting planes can be broken or stepped. IN broken lines in sections, cutting planes intersect (Fig. 12, A). In this case, parts of the section are depicted combined into one plane, and the elements of the part located behind the cutting plane are depicted as usual when making views. When designating a broken section, additional strokes indicate the places where the cutting planes intersect with each other.
IN stepped In the sections, the planes are located parallel to each other, as shown in Fig. 12, b. To identify the shape of the holes in this part, two cutting planes parallel to each other were used. Their position is marked in the drawing by a section line. The transition point from one cutting plane to another is made with a broken line of the same thickness as the strokes of the section lines. Arrows should be placed on the starting and ending strokes to indicate the direction of view. Arrows are applied at a distance of 2 - 3 mm from the end of the stroke (see Fig. 7), while the initial and final strokes should not intersect the contour of the image.
When making a step cut, parallel cutting planes are combined into one, so the inflection lines of the section lines are not reflected on the cut (a complex cut is designed in the same way as a simple one).
According to the location of the cutting planes relative to horizontal plane projection sections are divided into:
· 
horizontal
- the cutting plane is parallel to the horizontal projection plane. Such a section is shown in Fig. 13;
· vertical - the cutting plane is perpendicular to the horizontal projection plane (Fig. 11);
· inclined - the secant plane makes a certain angle with the horizontal projection plane that is different from a right angle (Fig. 14).
Vertical and inclined cuts must be constructed and positioned in accordance with the direction indicated by the arrows on the section line. It is allowed to place such sections anywhere in the drawing, as shown in Fig. 14, A, as well as with rotation to the position corresponding to that accepted for this part in the main image. In this case, it is necessary to add a sign to the cut designation that replaces the word “rotated” (see Fig. 10, A). An example of the design of an oblique rotated section is shown in Fig. 14, b.
 |  |
| (A) | (b) |
The vertical section, in turn, is called frontal , if the cutting plane is parallel to the frontal plane of projections (for example, a section A-A in Fig. 11), or profile , if the cutting plane is parallel to the profile projection plane (for example, a section A-A in Fig. 8).
Frontal and profile sections can be located in place of the corresponding types (according to GOST 2.305-68). It is precisely these sections that students need to draw when performing RGR, similar to those shown in Fig. 38 example.
According to the position of the cutting plane relative to the part and its elements the incisions are divided into longitudinal (section planes are directed along the length or height of the part) and transverse (section planes are located perpendicular to the length or height of the part).
For execution and design incisions are divided into complete, incomplete, local and extensive. Full section - a section of the entire part (Fig. 11), if the images of the view and the section are asymmetrical figures.
Incomplete section - a section of a part of a part is made in the view, if the view or section does not fully reveal the design of the asymmetrical part (Fig. 15).
In the case of symmetrical (relative to the axes of the figures) view and section, half of the view is shown, combined with half of the section. The boundary between the view and the section is the axis of symmetry, as shown in Fig. 38. The rules for combining a view and a section in one image are discussed in detail in subsection 1.2.2.
It is also possible to separate the view and the section with a thin dash-dotted line (see Fig. 16), which coincides with the plane of symmetry not of the entire part, but only of its part, if this part is a surface of rotation. In Fig. 16 shows a part of the connecting rod, which has a cylindrical element, so the section is made only up to its axis of symmetry.
Expanded cut - a cut of a curved part made by a cylindrical secant surface. The section is aligned with the plane (unfolded) to obtain an undistorted image. In this case, a sign replacing the word “expanded” is placed above the cut (see Fig. 10, b). An example of such a section is shown in Fig. 9.
Many parts have such a shape that when depicting them, it is not enough to show only the view or only the section, since the section sometimes cannot represent the external shape of the part. In Fig. 15 shows an asymmetrical part. If you show its full frontal section, the height and shape of the tide on the outer surface details. When depicting such details, it is necessary to perform two different images - both a view and a section, which takes a lot of time and space. Therefore, GOST 2.305-68 allows the connection of part of the view and part of the section in one image (Fig. 15).
In this case, part of the view and part of the section are separated by a thin solid wavy line 0.3 - 0.5 mm thick, drawn by hand (Fig. 17, b), or a solid thin line with a break (Fig. 17, V). This line must not coincide with any contour lines on the drawing.
So, the left part of the part in Fig. 15 is shown as a view from which one can judge the external shape of the entire part, and the right side of the part is shown in section. The section shows the internal structure of the entire part. The top view clarifies the presence of a second cylindrical hole, not revealed by the cut, and the thickness of the walls of the upper hollow part of the part.
This example shows a rational way to construct a drawing for an asymmetrical part with a complex shape.
Special case connection of view and section - connection of half of the view and half of the section. Such a connection is possible provided that both images (view, section) are symmetrical figures.
In Fig. Figure 18 shows the part, its front view and frontal section. These images require significant time to complete. The part in question is symmetrical with respect to vertical axis. Each image - both the view and the section - are symmetrical figures relative to this vertical axis. From one half of a view or section it is easy to imagine its second, symmetrical half.
Therefore, GOST 2.305-68 recommends, in order to reduce the size of the drawing and graphic work, to connect half the view and half the section, if the view and section are symmetrical figures. The result is the image shown at the top of Fig. 18, from which one can judge both the external and internal design of the part. The left half of the image is external view details, and the right one is its section. The dividing line between half the view and half the section is the axis of symmetry (dash-dotted thin line in Fig. 19), and not a solid wavy one, as when dividing the view and section of an asymmetrical part (in the example of Fig. 15).
There is also no need to draw a contour line, since this image is conditional and there is no line on the part in the place of the depicted section of the view and section. Dashed lines of invisible elements of a part are not drawn in views, as this reduces the quality of the drawing, impairs its visibility, and makes it difficult to apply dimensions and roughness marks. Therefore, invisible elements are replaced with visible ones using cuts.
As a rule, the frontal and profile sections are located to the right of the axis of symmetry, and the horizontal section is located below the axis of symmetry.
The part shown in Fig. 1 and 2, symmetrical relative to the frontal plane G, and the pentagonal prism in Fig. 8 is symmetrical relative to the profile plane A-A. Therefore, full cuts (frontal in Fig. 5 and profile in Fig. 8) are not rational. It is more expedient, according to GOST 2.305-68, to combine half the front view and half the frontal section in the main image (Fig. 20); half of the left view and half of the profile section (Fig. 21).
As noted above, in most versions of tasks for calculation and graphic work, symmetrical parts are presented, therefore, when making a drawing, it is necessary to connect half of the front view with half of the frontal section and half of the left view with half of the profile section.
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The shape of many parts is such that when depicting them, it is not enough to give only a view or just a section, since from a section it is sometimes impossible to imagine the external shape of the part. When depicting such details, it is necessary to give both a view and a section, i.e. perform two different images, which takes a lot of time and space. Therefore, it is allowed to combine part of the view and part of the corresponding section in one image. In this case, the view and the section are separated by a solid wavy line of the same thickness and shape that is used to highlight the local section.
For example, if in Fig. 5.23 give a full frontal section of the part, then there will be no data to determine the height and shape of the tide on its outer surface. Therefore, the left part of the part is shown without a section - its appearance is given, by which one can judge the external shape of the entire part, and the right part of the part is shown in section. The section shows the internal structure of the entire part, since in the top view one can determine the thickness of the walls of the upper hollow part of the part and the presence of a second cylindrical hole, not revealed by the section. This example demonstrates a rational way to construct a drawing.
Rice. 5.23.
Connecting half view and half section
The connection of half the view and half the section, each of which is a symmetrical figure, is a special case of the previous rule.
In Fig. 5.24, A Drawings of the part without a cut and next to the cut are given. These images require significant time to complete.
In Fig. 5.24, b the drawing contains half of the main view and next to it half a section of the same part. Is the shape of the missing half of the view or half of the section clear, in the place of which there are question marks? Since the view and the section are symmetrical figures, using half of the view you can imagine its second half. The same can be said when considering half of the cut. Therefore, GOST 2.305–2008 recommends, in order to reduce the size of the drawing and the time it takes to complete it, to connect half of the view and half of the corresponding section, when the view and section are symmetrical figures. Then you will get an image by which you can judge both the external form and the internal structure details (Fig. 5.24, c).
Rice. 5.24.
When performing images containing a connection of half of the view and half of the corresponding section, it is necessary to observe following rules(Fig. 5.24, c):
- the line dividing half of the view and half of the section should serve as an axis of symmetry, i.e. a dash-dot thin line, and not a solid wavy one, as was the case when dividing asymmetrical figures in view and section; It is also not necessary to draw a contour line at the place of the section, since the image is conditional and there is no line on the part at the place of the imaginary section;
- dimension lines relating to a part element drawn only up to the axis of symmetry are not drawn completely, somewhat further than the axis, the arrow is drawn only on one side, but the size should be drawn in full.
It is also allowed to separate the section and the view with a dash-dotted line coinciding with the trace of the plane of symmetry not of the entire object, but only of its part, if this part is a body of rotation. An example of such a case is shown in Fig. 5.25, which shows part of the connecting rod. It has a cylindrical element (body of rotation), the cut on which is made only up to the axis of symmetry.
Rice. 5.25.
Some details are projected in the form of a symmetrical figure, but when depicting them, you cannot use a combination of half the view and half the section. Examples of such parts are shown in Fig. 5.26, a, b.
Rice. 5.26.
Drawn in Fig. 5.26, A cylindrical part has in addition to other elements square hole. The edge of this hole coincides with the axis of symmetry.
If you connect half of the main view and half of the frontal section, then, due to the fact that the dividing line between them is an axial one, the line representing the edge disappears, and the drawing will become unclear. In such cases, you need to make part of the view (not half) and part of the section, separating them with a solid wavy line (see Fig. 5.23).
This line must be positioned so that the edge about which we're talking about, was shown in the image. If it is located on inner surface, then they give more than half of the cut (see Fig. 5.26, A), and if on the outside - more than half of the view (see Fig. 5.26, b).
Incision- an image of an object mentally dissected by one or more cutting planes.
The mental dissection of an object determines the convention of the image - the cut, and does not entail changes in other images, because the part of the object located between the observer and the projection plane is removed, conditionally.
The section shows the internal structure of the object, making it possible to avoid the use of dashed lines that make it difficult to read complex elements in the drawing. see also
The cuts are divided according to the following criteria:
1. From the position of the secant planes relative to the projection planes:
Horizontal;
- frontal;
- profile;
- inclined.
Horizontal section obtained using a secant plane parallel to the horizontal projection plane. A horizontal section is usually placed in the place of the top view, but it can also be placed in any free space in the drawing.
Spatial picture of the formation of a horizontal section:
1.
The cutting plane must be parallel to the horizontal projection plane. 2.
The cutting plane should be entered in the place of the model where its internal cavity can be most fully identified when projected onto the horizontal projection plane. 3.
The part of the part above the cutting plane is mentally discarded. 4.
The image on the horizontal projection plane is formed in accordance with general rules making cuts.
Vertical section obtained using a secant plane perpendicular to the horizontal projection plane. A vertical section is called frontal if the cutting plane is parallel to the frontal plane, and profile if the cutting plane is parallel to the profile plane of projections.
Spatial picture of the formation of a vertical section:
1.
The cutting plane must be parallel to the frontal projection plane. 2.
The cutting plane should be entered in the place of the model where its internal cavity can be most fully identified when projected onto the frontal projection plane. 3.
The part of the part in front of the cutting plane is mentally discarded. 4.
The image on the frontal plane of projections is formed in accordance with the general rules for making cuts.
2. From the number of cutting planes:
Simple - one cutting plane;
- complex - two or more cutting planes.
Complex cuts are:
Complex stepped;
- complex broken.
3. From the direction of cutting the object:
Longitudinal - along large dimensions of an object;
- transverse - perpendicular to the large dimensions of the object.
4. From the volume of dissection of the object:
Complete, when the entire object is cut;
- local, if part of the object is cut.
Position cutting plane indicated on the drawing by a section line - an open line.
In a complex cut, strokes are also drawn at the places of transition of one secant to another (in a stepped cut) and the intersection of secants with each other (in a broken line).
Arrows are placed on the initial and final strokes, indicating the direction of view (projection). Arrows should be applied at a distance of 2-3 mm from the outer ends of the strokes.
The starting and ending strokes must not intersect the outline of the corresponding image.
At the beginning and end of the section line, and, if necessary, at the places of transitions and intersections of cutting planes, place the same capital letter of the Russian alphabet, and the letter is always placed horizontally and with outside arrows.
The font size for these letters is taken 1-2 sizes larger than the font size for drawing sizes.
The same letters are placed above the cut and are not underlined. The appropriate cuts are made in a similar way after the process of drawing dimensions on the drawing.
Cases of cuts.
When making simple horizontal, frontal, profile sections in cases where 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 image, then the position of the cutting plane they are not marked and the incision is not accompanied by an inscription.
When making cuts obtained by one cutting plane, but having the opposite direction of projection, it is recommended to use one section line, and the arrows are directed according to the selected projection directions and are marked with different in capital letters Russian alphabet.
If a local cut is made on a part of an object representing a body of revolution, then such a cut can be separated from the view by a thin dash-dotted line, which is the axis of this part of the object.
It is allowed to connect part of the view and part of the section, separating them with a solid wavy line or a solid thin line with breaks (like a local section). In this case, it does not matter which of the images (view or section) will occupy a larger or smaller part of the projection. Such a cut is not indicated.
If half of the view and half of the section are connected, each of which is a symmetrical figure, then the dividing line is the axis of symmetry. In this case, half of the incision is usually placed on the right with a vertical and below with a horizontal axis of symmetry (dash-dotted thin line).
In this case, the statement that one quarter of the object was cut out here with two supposedly secant planes is not true. Drawing dashed lines for invisible elements on half of the view may be unnecessary.
If at possible combination half of the view and half of the section coincide with the axis of symmetry by a solid main line, then it must be shown, but the view and section are separated by a solid wavy line, showing more view, if the solid main line is external or larger than the section, if the solid line is internal.
Connecting half a view with half a section is possible not only for simple cuts, but for complex ones, when independent images (view and section) are symmetrical.
It is allowed to use a cylindrical surface and a cut as a secant deploy. In this case, the “expanded” sign is placed above the cut.
It is allowed to combine a quarter of a view and a quarter of three sections (and other combinations), provided that each of these images is individually symmetrical.
At complex broken cuts The cutting planes are conventionally rotated until they are aligned into one plane parallel to the projection plane. Such a section may be placed in place of the corresponding main view. Complex polygonal cuts can be made using more than two cutting planes. When rotating the secant plane, the elements of the object located behind it are drawn as they are projected onto the corresponding plane with which the alignment is made. The rotation direction may not be the same as the viewing (projection) direction. 
Broken cut is formed when a part is cut by planes intersecting at an angle greater than 90. As a rule, one of the cutting planes is placed parallel to one of the main projection planes. When constructing an image, the inclined plane is combined (rotated) to the plane parallel to the plane projections. Next, a broken section is constructed by analogy with a simple one, while the line of intersection of the cutting planes is not shown on the section. It is allowed to place a broken cut in place of the corresponding type, i.e. on the projection plane to which one of the cutting planes is parallel.
Grade 9 “Connecting half of the view and half of the section”
Topic: Connection of view and section.
The purpose of the lesson
:
Educational - introducing students to the rules for connecting half a view with half a section, the features of designating sections and the conventions adopted in such cases.
Educational – instilling the desire to conscientiously and rationally carry out educational tasks.
Developmental – development logical thinking students.
Tasks:
Assist in developing students' interest in the topic being studied.
Form a clear idea of the need and feasibility of connecting the view and the section.
To assist in the development of spatial understanding and spatial thinking in schoolchildren.
Skill acquisition teamwork during frontal work in the classroom.
Cultivating accuracy in work.
Lesson type - combined
Organization of work in the lesson – frontal and individual.
Methods : Conversation, explanation, demonstration, independent work.
Equipment : Textbook, “Sections” posters, drawing tools, computer for showing the presentation..
Lesson structure
Org. moment – 1 - 2 min.
Repetition – 5 min
New material - 15 - min.
Consolidation - 20 min.
Final part – 2 min.
Progress of the lesson
1. Organizational moment
2. Checking homework. ^
Hello, please sit down.
Today in the lesson we will get acquainted with a new species for you graphic constructions, which combine the types and sections familiar to us.
Introduction to the lesson objective.
Recording the topic in your workbook.
While you are writing down the topic of the lesson, I would like to see your homework. That's it - has it been done? What problems have arisen?
3. Front graphic poll
1) Repetition of theoretical material from the previous lesson on the topic “Sections, cuts”, updating the acquired knowledge.
^ What is the name of the image of a figure obtained by mentally dissecting an object with a cutting plane?
What is a cut?
^ How does an incision differ from a section?
Why are sections used by designers, artists, archaeologists, doctors, biologists and other specialists?
2) Fill in the missing words.
3) Carrying out tasks to match the main view and section of the part (oral).
What is the algorithm for constructing a section?
Depending on the design (on the design of the part, its shape), one or another cut is chosen, and the cut should be expedient those. should not follow the main contour of the part without revealing its internal structure.
What cut is advisable to make if the part has 1 plane of symmetry?
4 . Posting new material.
The topic of our lesson: Connecting a view with a section: connecting half a view and half a section
^ Connecting part of the view and part of the section. The shape of many parts cannot be revealed only by a section or view.
It is irrational to perform two images - a view and a section. Therefore, it is allowed to combine part of the view and part of the corresponding section in one image (Fig. 191). They are separated by a solid wavy line, which is drawn by hand.
If a full frontal section is made in Figure 191, then it will not be possible to judge the shape and height of the upper ear from the top view alone. It will not be shown on the frontal section. In this case, it is advisable to connect part of the view and part of the section. That's an example rational choice images in the drawing. (presentation show)
^ Connecting half the view and half the section.
The connection of half the view and half the section (Fig. 192), each of which is a symmetrical figure, is a special case
previous one.
In Figure 192, A are given main view and top view. From these images, one can judge mainly the external shape of the part. Figure 192, b contains a section and top view. From these images it is easier to judge the internal structure of the part.
In Figure 192, V given only. half of the main view, and in the figure 192, G - only half of the cut of the same part. Is the shape of the missing halves of the view and section clear, with question marks in their place? Since the view and the section in this case are symmetrical figures, we can imagine the second half of the image.
In such cases, it is recommended to connect half of the view and half of the corresponding section in the drawing. From it you can judge both the external and internal shape of the part (Fig. 192, d).
When performing images containing a connection of half of the view and half of the corresponding section, it is necessary to observe
the following rules:
the boundary between the view and the section should be the axis of symmetry, a thin dash-dotted line;
the section in the drawing is located to the right of the axis of symmetry or below it;
on half of the view, dashed lines depicting the outline of the internal outlines are not drawn;
dimension lines relating to a part element drawn only up to the axis of symmetry (for example, a hole) are drawn slightly further than the axis and limited by an arrow on one side. The size indicated is full.
If the contour line coincides with the axis of symmetry, then connect part of the view and part of the section, separating them with a solid thin wavy line so that the contour line in question does not disappear from the drawing.
Consolidation
To consolidate and control the acquired knowledge, it is proposed to take a test - choose the correct answer from those proposed (Appendix 1)
^ 5. Graphic work
Frontal practical work : making drawings with sections - “Making an expedient cut of a part” p. 149 exercise 56 fig. 194
Complete the task in Figure 194 - connecting half the view and half the section, enlarging the image twice. Do not draw the view on the left. Show with the help of symbols printed on the dimension lines that all the external shapes of the parts are cylindrical, the internal ones - in examples a and c - are also cylindrical, but in the example b the right and left holes are square.
^ 6. Lesson summary:
- What did you like about today's lesson?
- Difficult – was there any work in today’s lesson, did everyone cope?
- What would you like to change in the lesson if it could be held again?
I would like to note the active work in the lesson:
_____________________________________________
_____________________________________________
^ 7. Homework:
Textbook: paragraph 25; pp. 147-151
Rear 57, p. 151, (Fig. 195 a)
Annex 1
Choose the correct answer from those given.
1. Nursery cutting plane coincides with the axis of symmetry , she
a) not indicated b) indicated.
2. If the part is symmetrical, it is advisable
a) simple full cut
b) connecting half the view and half the section
c) connecting part of the view and part of the section
3. If the axis of symmetry is vertical, then half of the incision is placed:
a) left b) right
4. The boundary between half the view and half the section is the line:
a) slip thin b) dashed c) dash-dotted
5.
If an element (for example: a hole) is drawn only up to the axis of symmetry
(as in the case of connecting half of the view and half of the section), then the dimension lines are drawn:
a) one arrow indicating the full size
b) one arrow indicating half the size
c) two arrows indicating the size
