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Graphic representation of parts made of thin sheet metal and wire
Parts made of thin sheet metal and wire are depicted in the form technical drawing, drawing, sketch. Drawings of several products are shown in the figures below.
hole diameter, rings are indicated by the sign Ø (see figure on the right). The number next to this sign indicates the diameter of the hole in millimeters.. If there are several holes of the same diameter nearby, then in the drawing, above the extension line (starting at one of the holes), the number of holes and their diameter are written.
Part thickness sheet metal in the drawing is indicated by the letter S, a the number immediately following the letter is the thickness of the part in millimeters.
Radius sign R, put next to it a number indicating the size of the radius.
If the wire diameter is less than 2 mm, then it is depicted in the drawing as a solid thick main line (see the figure on the left).
A wire with a diameter of more than 2 mm is shown by two parallel solid thick main lines with an axial dash-dotted line in the middle (see figure on the right).
Fold lines on the drawing (sketch) it is necessary to show a dash-dotted line with two points,
centers of circles, holes- dash-dotted (center lines) intersecting at right angles.
The center dash-dotted lines must intersect the contour lines.
When calculating the length of a piece of wire, remember that the circumference is 6.28R.
A part of a part that has a specific purpose is called a part element.
Any detail can be represented as a set of elements grouped in a certain way into one whole. The elements of the part are chamfers, grooves, holes, keyways, fillets, grooves, flats, threads, shoulders, etc. (Fig. 1).
Structural and technological elements are diverse. The shape and material of each element of the part is determined by the functions performed.
The shapes of the parts as a whole and in individual elements must be rational and technologically advanced, i.e. should be formed by a combination of elementary geometric bodies that require a minimum number of simple production operations for the manufacture and processing of their surface.
Structural elements of the part ensure that the part performs its working functions.
In addition to structural elements, many parts have technological elements in their composition. They can act as part supports during processing (center holes), provide ease of assembly of parts (chamfers, grooves), create the possibility of a free exit of the tool, for example, when cutting threads, gear teeth.
Elements of parts are divided into simple and complex. The shape of a simple element is formed by a compartment of one surface. The shapes of simple elements often coincide with the shapes of the basic geometric bodies. The image of a complex element is formed from several simple elements.
Examples of simple elements are a cylinder, a cone, a plane, a sphere, a torus; complex - center holes, keyways, T-slots (Fig. 2 a, b), etc.
Detail elements can be divided into single and group (repeating). An example of a single element is a gear hub, a group of elements is its teeth. The hub in the drawing is designated without simplifications, the teeth are conventionally denoted by the circles of protrusions da, depressions df and pitch diameter d (Fig. 3).
Another example would be a plate with a group of holes. The plate is depicted as a whole, and from all the holes it is allowed to depict one with an indication of the size and number of identical holes, the location of the rest is marked by axial lines (Fig. 4).
Detail elements can be divided into standard and non-standard. Standard elements have standard images and sizes. At-
measures of standard elements are keyways, chamfers, grooves, center holes, etc.; non-standard - bosses, flats, etc.
In addition to structural and technological elements, details may contain informational elements, for example: plates, inscriptions of pointers. They are made in the form of separate parts or in the form of protrusions or depressions on the surfaces of the parts. Information elements on the details are depicted accurately, without simplifications (Fig. 5).
In assembly drawings and general arrangement drawings, information elements may be depicted in a simplified way as an outline of the elements to show their relative position.
2.1. Elements of parts such as bodies of revolution Chamfers - conical elements that provide blunting of sharp cuts
mok parts, used to ensure the assembly process (Fig. 1), protect hands from cuts (safety requirements), etc.
The dimensions of the chamfers and the rules for their representation in the drawings are standardized. According to GOST 2.307 - 68, the dimensions of the chamfers are applied as shown in fig. 6. The size of the chamfer leg is chosen, according to GOST 10948 - 64, from the following series of numbers: 0.1; (0.12); 0.16; (0.2); 0.25; (0.3); 0.4; (0.5); 0.6; (0.8); one; (1,2); 1.6; (2); 2.5; (3); four; (5) etc. up to 250 mm. Sizes without brackets are preferred. Sometimes chamfers are replaced by roundings (fillets), the values of the rounding radii are equal to the leg.
Flats are performed on shafts, axles, etc. in the form of platforms parallel to the axis of rotation, mainly to prevent rotation of parts during assembly
Collars. On shafts and axles, thrust shoulders (ledges) are often used, against the ends of which the parts mounted on the shaft rest. To improve the quality
The two connections on the shaft make a fillet with a radius smaller than the fillet radius of the mounted part, or they make a groove on the shaft in this place for the grinding wheel to exit, and a chamfer on the mounted part (Fig. 7).
Rice. 8 Grooves (grooves) are used to install locking parts in them,
sealing gaskets (Fig. 8), exit of cutting tools, for example, when grinding the outer cylindrical surface (Fig. 1). To avoid the formation of a thread run x, which has an incomplete profile (Fig. 9a, d), external (Fig. 9c) or internal (Fig. 9e) grooves are made on the parts before threading. The dimensions of the run x, undercut a (Fig. 9b, e), the shape and dimensions of the grooves for
thread outlets of various types are established by GOST 27148 - 86. The appendix contains the relevant data.
The corrugation is performed on the surfaces of the parts so that they do not slip in the hands when turning. According to GOST 21474 - 75, the drawings indicate the type of corrugation (straight, mesh), its pitch (0.5; 0.6; 0.8; 1.0; 1.2; 1.6; 2.0) and number GOST (Fig. 10).
center hole. When processing or testing parts such as bodies of revolution, the center holes of the part include the centers of the machine or fixture on which the part is installed. Center holes are made and designated in accordance with GOST 14034 - 74 (Fig. 11a). If the center holes in the finished product are unacceptable, then the sign shown in Fig. 11b.
- Is it possible to make a product according to a drawing?
- What data do you need to know to make a product?
- What is a design document?
- From which document can you find out about the shape and dimensions of the product?
- Remember what parts are called symmetrical.
- Which line is called the axis of symmetry?
For the manufacture of any product, it is necessary to determine its shape, dimensions, materials from which it will be made, methods for connecting individual parts, provide for what tools are needed for this, etc. Such work at the enterprise is performed by a designer. They draw up their ideas in special documents, the constituent elements of which are graphic images.
A graphic is an image consisting of lines, strokes, dots and performed with a pencil or ballpoint pen. The main graphic images are a drawing and a sketch (Fig. 36).
Rice. 36. Graphic images: a - drawing of the part; b - sketch
Detail drawing- this is a document containing a graphic image of a part made using drawing tools on paper, and the information necessary for its manufacture and control (Fig. 36, a). In practice, graphic images are also used, made in a simplified way - by hand, without the use of drawing tools, but in compliance with the proportions between the parts of the depicted part (Fig. 36, b). They are called sketches.
Sketches used in the design of new and improvement of existing products. It is with the help of a sketch that an architect, designer, designer, innovator embodies his idea, his creative idea on paper. Sketches are also performed when there is an urgent need to manufacture a part instead of the one that failed, and its drawing is missing.
When performing graphic images, different types of lines are used, each of which has a specific name and purpose. Information about the lines of the drawing is presented in table 2.
Table 2. Drawing lines
In order to be able to use graphic images in any sector of the economy, each country adheres to uniform rules for their implementation. They are defined by a document called the Unified System for Design Documentation (abbreviated as ESKD).
To facilitate the sketch and maintain proportionality between the individual elements of the part, when making a graphic image, it is better to use checkered paper.
In order to draw a conclusion about the size of the depicted product or any part of it from the drawing, dimensions are applied to the drawing. There are linear and angular dimensions.
Linear dimensions characterize the length, width, thickness, height, diameter or radius of the product. The angular dimension characterizes the magnitude of the angle. The linear dimensions in the drawings are put down in millimeters, but the designations of the units of measurement are not applied. Angular dimensions are noted in degrees, indicating the units of measurement. The numerical value on the horizontal dimension lines is applied from above the line, and on the vertical dimension lines - to the left (Fig. 37).
Rice. 37. Application of numerical dimensions: a - linear; b - corner
When performing a graphic image, it is necessary that the total number of dimensions in the drawing be the smallest, but sufficient for the manufacture and control of the product.
When making drawings and sketches, certain conventions are used. So, the diameter of parts or holes is marked with the Ø icon, to indicate the radius, a capital Latin letter R is written in front of the dimension number. The thickness of flat parts made of plywood, fiberboard, thin sheet metal is marked with the Latin letter S. You will familiarize yourself with other features of the drawings in high school .
Before proceeding with the sketch of the product, you need to follow two stages.
Stage one:
- prepare a sheet of paper, a pencil, an elastic band, a ruler;
- carefully inspect the existing product, determine the location of holes, recesses, protrusions; determine the approximate (eye) overall dimensions;
- find out what graphic image needs to be made for a complete idea of the shape of the product and the possibility of its manufacture;
- measure the overall dimensions of the existing product.
Stage two(Fig. 38):
- on a sheet of paper in a box, draw a frame with thin lines in which a sketch of the product will be performed. Its dimensions must correspond to the overall dimensions of the product, while maintaining proportionality between its elements. Apply axial and center lines (Fig. 38, a); circle with thin lines the shape of the overall outline of the product (Fig. 38, b);
- circle the detailed outlines of the product with thin lines: holes, protrusions, other elements, wipe off the excess (Fig. 38, c);
- circle the contour of the product with thick lines, put down the dimensions necessary for the manufacture of the product, according to ESKD (Fig. 38, d).
You will get acquainted with other features of the drawings in high school.
Rice. 38. The sequence of the sketch of the part
To complete the drawings, you need to have the appropriate drawing tools: a drawing ruler, drawing compasses, squares, a pattern, a protractor, an elastic band, pencils of various hardness. See their purpose in Table 3.
Table 3. Drawing tools
For high-quality performance of graphic images, it is necessary to skillfully organize the workplace, observe the following rules of safe work.
Laboratory and practical work No. 7. Reading drawings
Equipment and materials: workbook, ruler, compasses, pencil.
Work sequence
- Check out the detail drawings shown in Figure 40.
- Complete their sketches in your workbook.
- Determine the following dimensions specific to each drawing:
- the length and width of the square;
- the thickness of each part;
- round hole diameter;
- ring radius;
- ring width;
- square hole size.
- Record certain data in the table according to the form below.
Rice. 40. Detail drawing
New terms
useful thing, graphic image, design documents, constructor, drawing, detail, product, sketch, symbols, drawing tools.
Basic concepts
- Image- Recreation (display) of something using a drawing, drawing, sketch.
- design document- a graphic document containing all the information for the manufacture of the product and its control.
- markup- drawing on the surface of the workpiece the contours of the future part in accordance with the drawing.
- Symbol- an accepted graphic sign, symbol or letter that marks some real object of images.
Fixing the material
- What graphics do you know?
- What is a detail sketch?
- What lines are used in the product drawing?
- What are the main lines?
- How to properly dimension a drawing?
Test tasks
1. Establish a correspondence between the designations of the lines of the drawing and their names and purpose.
- solid thin (dimensional) line
- solid thin (leading) line
- dash-dotted (axial) line
- dashed (line of invisible contour)
- solid thick (visible contour line)
- dot-dash center line
2. Which image shows a product with rectangular elements?
3. On which drawings are the dimensional numbers correctly applied?
4. Which drawing correctly shows the size of the hole diameter?
5. An image of an object made by hand, “by eye”, without a drawing tool, is called ...
- A graphic document
B sketch
In the project
G technical drawing
D technical drawing
6. What line is used to indicate the invisible contour?
- And a solid thin
B dash-dotted
In dashed
7. What line is used to indicate the axis of symmetry of the part in the drawing?
- And dash-dotted
B dashed
In a solid thin
G solid thick
D no correct answer
Often the detail is so large that its life-size image does not fit on a sheet of paper. It is also difficult to depict a very small detail life-size. To do this, use a reduced or enlarged image of the part.
The number that shows how many times the actual dimensions of the part are reduced or increased is called the scale. The scale cannot be arbitrary. Strictly defined scales are established: for example, to reduce - 1:2, 1:4, 1:50000, etc., and to increase 2:1, 4:1, 10:1, etc. In the drawing, made in any scale, give actual dimensions.
A technical drawing is a three-dimensional image of an object, made by hand with the same lines as the drawing, indicating the dimensions and material from which the product is made. It is built approximately, by eye, maintaining the relationship between the individual parts of the object. The sign "Ø12" in the figure indicates that the diameter of the hole is 12 mm.
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