Based on the images of an object in the drawing, one can judge its size and the size of its individual parts. The basis for this are dimensional numbers, regardless of what scale and with what accuracy
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images are completed. The rules for applying dimensions on drawings are established by GOST 2.307-68.
Dimensions in the drawing are indicated by dimensional numbers, dimension and extension lines. Dimensional numbers on drawings are usually indicated in millimeters without indicating units of measurement. In cases where it is necessary to use other length units, they are shown after the dimension number.
Dimensional numbers are applied above the dimension line, possibly closer to its middle. The gap between the size number and the size line should be about 1.0 mm. The height of the dimensional numbers is taken to be at least 3.5 mm (Fig. 7).
The dimension line is drawn parallel to the segment whose size is applied above it. It is carried out between extension lines drawn perpendicular to the dimensional lines. It is allowed to draw dimension lines directly to the lines of the visible contour, axial and center. In some cases, the dimension line may not be drawn perpendicular to the extension (Fig. 8). Dimension lines are limited by arrows (Fig. 9). In some cases, they are not carried out completely, but with the arrow broken on one side (Fig. 10). The size of the arrow is chosen based on the thickness of the solid thick main line adopted in the drawing. Within one drawing, the size of the arrows should be the same as possible. It is not recommended to use contour, axial, center and extension lines as dimension lines.
If the length of the dimension line is small to accommodate the arrows, then the dimension line is extended beyond the extension lines, and the dimensions are applied as shown in Fig. eleven.
Extension lines are drawn from the boundaries of measurements; they are auxiliary and serve to place dimension lines between them. If possible, extension lines should be placed outside the image contour, perpendicular to a straight line segment, the size of which must be specified. The extension lines should extend beyond the ends of the arrows of the dimension lines by 1...5 mm (Fig. 12).
The minimum distance from the dimension line to a line parallel to it should be 10 mm, and between parallel dimension lines - 7 mm.
Angular dimensions in drawings are indicated in degrees, minutes and seconds, indicating units of measurement. The size of the angle is applied above the dimension line, which is drawn in the form of an arc with the center at its apex. In this case, extension lines are drawn radially (Fig. 13).
At different inclinations dimension lines dimension numbers linear dimensions positioned as shown in Fig. 14, a, and the angular dimensions are as shown in Fig. 14, b. If the dimension line is located in an area that is shaded in the drawing, dimension numbers are applied on the shelves of leader lines (Fig. 15).
If there is not enough space above the dimension line to write the dimension number or this space is occupied by other image elements and
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It is impossible to enter a dimensional number into it; the dimensional number is applied according to one of the options shown in Fig. 16.
In order to simplify a number of images and create ease of reading of the drawing, the standard provides for the use of symbols in the form of letters of the Latin alphabet and graphic signs that are placed in front of the dimensional numbers. Used in drawings
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signs and letters to indicate diameter and radius, arc and square length, slope and taper, sphere, thickness and length of the part.
The sign 0 is applied before the diameter size number (Fig. 17). Moreover, there are no gaps between the sign and the number. For circles of small diameter, the arrow dimension lines and the dimension itself are drawn according to one of the options shown in Fig. 18.
Before the dimensional number of the arc radius there is always a sign in the form of a capital Latin letter R. In this case, the dimension line is drawn towards the center of the arc and is limited to only one arrow, resting on the arc or its extension (Fig. 19). If the radius in the drawing is less than 6 mm, it is recommended to place the arrow
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lay on the outside of the arc. If it is necessary to specify the position of the center of the arc, it is marked by the intersection of center or extension lines (Fig. 20). In cases where the drawing shows an arc of large radius, for which the center need not be marked, the dimension line is cut off without reaching the center (Fig. 21). If in this case the center needs to be marked, it is allowed to bring it closer to the arc (Fig. 22). The dimension line in this case is shown with a 90° bend, and both sections of the dimension line are drawn parallel. Dimension lines that extend from the same center and are intended to indicate dimensional arcs should not be placed on the same straight line. It is recommended to use radii to denote arcs up to 180°; arcs whose magnitude is more than 180° are designated by diameter.
The arc sign is applied above the dimension number (Fig. 23). The length of the arc is specified in linear units, and the dimension number indicating the arc is plotted above the dimension line in accordance with the usual requirements.
To set the dimensions of a square, use the corresponding sign D, the height of which is equal to 7/10 of the height of the dimension number (Fig. 24, A). If the square is positioned differently, the dimensions of its sides are indicated (Fig. 24, b). It should be noted that the square sign is applied only on the image on which it is projected into a line.
The surface taper sign is applied on the shelf of a leader line located parallel to the cone axis or on the cone axis (Fig. 25, A). The cone sign is positioned so that its acute angle is directed towards the apex of the cone. The amount of taper is determined by the ratio of the difference in diameters of two cross sections of the cone to the distance between these sections, i.e. k= D-
dll, Where D- diameter of large section; d- diameter of smaller section; l- distance between sections. Taper is indicated as a simple fractional number (Fig. 25, b).
The straight slope sign is indicated on the shelf of the leader line. Slope i represents the tangent of the angle between a given line and a horizontal or vertical line (Fig. 26, a). The slope sign is located
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so that its acute angle is directed towards the slope of the straight line (Fig. 26, b). The slope, like the taper, is specified in the drawing as a simple fraction, as a percentage or in ppm.
To designate a sphere in a drawing, use the sign of diameter or radius. In cases where it is difficult to distinguish a sphere from other surfaces in a drawing, the word “Sphere” may be added before the sign of the radius or diameter. The inscription on the drawing is made according to the type “Sphere diameter 17” or “Sphere R 10" (Fig. 27).
Simple flat parts are depicted in a single projection. In these cases, its thickness is indicated by a lowercase letter s and the inscription on the drawing is made according to the type s2 and is located on the shelf of the leader line (Fig. 28, a). The length of the object is indicated by the letter / (Fig. 28, b).
Chamfers in the drawings are applied in two linear dimensions (Fig. 29, A) or one linear and one angular (Fig. 29, b). In case if
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the angle of inclination of the cone generatrix is 45°, a simplified chamfer designation is used when the dimension line is drawn parallel to the axis of the cone, and the inscription is made as “2 x 45” (Fig. 29, c).
The basis for determining the size of the product and its elements are the dimensional numbers printed on the drawing. Dimensions are always true, regardless of the scale and with what accuracy the image is made. Dimensions must be assigned and applied so that they can be used to produce a part without resorting to calculations.
There should be a minimum number of sizes, but sufficient for the manufacture and control of the product. The absence of at least one of the dimensions makes the drawing practically unusable. Dimensions must be marked in such a way that no ambiguities or questions arise when reading them. It should be remembered that the drawing is read in the absence of the author.
According to GOST 2.307-2011 - “Applying dimensions and maximum deviations” linear dimensions in the drawing they are given in millimeters, without indicating the unit of measurement. Angular dimensions indicated in degrees, minutes, seconds with the designation of the unit of measurement. Each dimension is indicated on the drawing, in the main inscription, only once; it is unacceptable to repeat it.
When indicating the dimensions of straight segments, dimension lines are drawn parallel to these segments at a distance of at least 10 mm from the contour line and 7 mm from each other, and extension lines are drawn perpendicular to the dimension lines. Extension lines should extend beyond the ends of the arrows of the dimension line by 1...5 mm. The arrow of the dimension line must have a length of at least 2.5 mm and an apex angle of about 20° (Figure 3.1). The dimensions and shape of the arrows must be the same throughout the drawing.
3.2. Applying dimensions
In the drawings of parts, dimensions are indicated based on the manufacturing technology of the part and the surfaces on which the part comes into contact with other parts of the assembly unit.
This affects the choice of design base.
Based is called giving the workpiece the required position relative to the selected coordinate system.
Base called a surface or combination of surfaces, an axis or a point belonging to a product or workpiece and used for reference.
Design base— a base used to determine the position of a part or assembly unit in a product.
The basic rule for applying dimensions- grouping of sizes related to one geometric element in one image, in the one in which this element is most clearly represented. It is not always possible to achieve this, but we always strive for this.
When indicating the size of an angle, the dimension line is drawn in the form of an arc with the center at its vertex, and the extension lines are drawn radially (Figure 3.2).
Figure 3.3
As you can see, smaller dimensions should be placed closer to the contour of the part; the number of intersections of dimension and extension lines will be reduced, which will make the drawing easier to read.
The dimension line is drawn with a break if it is not possible to draw an extension line on one side of the image, for example, in the case of combining a view and a section (Figure 3.4, A), and also if the view or section of a symmetrical object is depicted only up to the axis or with a break (Figure 3.4, b). The break of the dimension line is made further than the axis or break line of the object.
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| A | b |
Figure 3.4
Dimension lines may be drawn with breaks in the following cases:
- when indicating the size of the circle diameter; in this case, the break of the dimension line is made further than the center of the circle (Figure 3.5);
- when drawing dimensions from a base not shown in this drawing (Figure 3.6).
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| Figure 3.5 | Figure 3.6 |
The main line must be broken if it intersects with the arrow (Figure 3.5).
When depicting a product with a gap, the dimension line is not interrupted (Figure 3.7). The dimensional number must correspond to the full length of the part.
Figure 3.7
If it is not possible to place dimensional numbers and arrows between closely spaced solid main or thin lines, they are applied outside (Figure 3.8). Do the same when applying the radius size if the arrow does not fit between the curve and the center of the radius (Figure 3.9).
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| Figure 3.8 | Figure 3.9 |
It is allowed to replace arrows with dots or serifs, applied at an angle of 45° to the dimension lines, if it is impossible to place an arrow between the extension lines (Figure 3.10).
Figure 3.10
Dimensional numbers must not be divided or crossed by any drawing lines. At the place where the dimension number is applied, the axial, center lines or hatch lines are interrupted (Figure 3.11).
Figure 3.11
Dimension numbers should be placed above the dimension line, as close to its middle as possible (Figure 3.12).
Figure 3.12
Dimensional numbers of linear dimensions with different slopes of dimension lines are placed as shown in Figure 3.13.
If it is necessary to apply dimensions to the shaded area, the corresponding dimensional number is applied on the shelf of the line - leader.
Figure 3.13
Angular dimensions are applied as shown in Figure 3.14.
Figure 3.14
In the area located above the horizontal center line, dimensional numbers are placed above the dimension lines on the side of their convexity, in the area located below the horizontal center line - on the concavity side of the dimension line.
Dimension numbers above parallel dimension lines should be placed in a checkerboard pattern (Figure 3.15).
Figure 3.15
When indicating the diameter size, in all cases the Ø sign is placed before the size number. Before the dimensional number of the diameter (radius) of the sphere, the sign “O” Ø (R) is also applied without the inscription “Sphere” (Figure 3.16).
Figure 3.16
If it is difficult to distinguish a sphere from other surfaces in the drawing, it is allowed to write the word “Sphere” or the sign “O”, for example, “Sphere Ø 18, OR12”. The diameter of the sphere sign is equal to the height of the dimensional numbers in the drawing.
The dimensions of the square are applied as shown in the drawing (Figure 3.17).
Figure 3.17
The height of the sign must be equal to the height of the dimensional numbers in the drawing.
When applying the radius size, place a capital letter in front of the size number R. With a larger radius, the center can be brought closer to the arc; in this case, the radius dimension line is shown with a bend at an angle of 90° (Figure 3.18). If it is not necessary to indicate the dimensions that determine the position of the center of the circular arc, then the radius dimension line may not be brought to the center and may be shifted relative to the center (Figure 3.19).
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| Figure 3.18 | Figure 3.19 |
Rounding radii, the size of which on the drawing scale is 1 mm or less, are not shown in the drawing and their dimensions are indicated as shown in Figure 3.20.
When applying the size of a circular arc, the dimension line is drawn concentrically to the arc, and the extension lines are parallel to the bisector of the angle, and the sign “” is placed above the dimension number (Figure 3.21).
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| Figure 3.20 | Figure 3.21 |
The dimensions of the 45° chamfers are applied as shown in Figure 3.22, A. A chamfer at an angle of 45° is allowed, the size of which in the drawing scale is 1 mm or less, not to be depicted and its dimensions indicated on the shelf of the leader line, as shown in Figure 3.22, b.
The dimensions of chamfers with other angles are applied according to general rules– two linear dimensions or linear and angular dimensions (Figure 3.23).
The question of what dimensions should be plotted on the drawing is decided taking into account the manufacturing technology of the parts and manufacturing control.
As a rule, the dimensions of complete circles are given by the diameter, and of partial circles by the radius.
When you need to set the distances between circles, for example, representing holes, set the distances between the centers of the circles and the distance from the center of any circle to one of the surfaces of the part.
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| A | b |
Figure 3.22
Figure 3.23
The surfaces from which the dimensions of other elements of the part are set are called base surfaces or bases.
There are several ways to apply dimensions:
- from the total base (Figure 3.24); as base surface The left surface of the plank is selected, from which the dimensions of all holes are indicated.
Such a system has an advantage, but the dimensions are independent of each other, the error of one of them does not affect the others.
- from several bases (Figure 3.25);
- chain (Figure 3.26).
Figure 3.24
Figure 3.25
Figure 3.26
When applying dimensions that determine the distance between evenly spaced identical elements of a product (for example, holes), it is recommended, instead of dimensional chains, to apply the size between adjacent elements and the size between extreme elements in the form of the product of the number of spaces between the elements and the size of the space (Figure 3.27).
With a large number of dimensions applied from a common base, it is allowed to apply linear and angular dimensions, as shown in Figure 3.28, while drawing a common dimension line from the “0” mark and dimensional numbers are applied in the direction of the extension lines at their ends.
Figure 3.27
Figure 3.28
It is allowed not to indicate on the drawing the dimensions of the conjugation radius of parallel lines (Figure 3.29).
Figure 3.29
External and internal contours parts are measured separately during production and control, so their dimensions should be plotted separately on the drawing (Figure 3.30).
Figure 3.30
Dimensions related to the same structural element(groove, protrusion, hole, etc.), it is recommended to group them in one place, placing them on the image in which geometric shape of this element is shown most fully (Figure 3.31).
Figure 3.31
If a part has roundings, the dimensions of the parts of the part are applied without taking into account the roundings, indicating the radii of the roundings (Figure 3.32).
Figure 3.32
The dimensions of symmetrically located elements of the product (except for holes) are applied once without indicating their number, grouping, as a rule, all dimensions in one place (Figure 3.33).
Figure 3.33
Identical elements located in different parts products (for example, holes) are considered as one element if there is no gap between them (Figure 3.34, A) or, if these elements are connected by thin solid lines (Figure 3.34, b). In the absence of these conditions, indicate the full number of elements (Figure 3.34, V).
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| A | b | V |
Figure 3.34 The dimensions of several identical elements of the product, as a rule, are applied once, with a line indicating the number of these elements on the shelf (Figure 3.35).
Figure 3.35
When applying dimensions of elements evenly spaced around the circumference (for example, holes), instead of angular dimensions, defining mutual arrangement elements, indicate only their number (Figure 3.36 - 3.38).
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| Figure 3.36 | Figure 3.37 | Figure 3.38 |
When depicting a part in one projection, the size of its thickness or length is applied, as shown in Figure 3.39.
Figure 3.39
Dimensions on the drawing are not allowed to be shown in the form closed circuit, except when one of the sizes is specified as reference.
Reference sizes– dimensions that cannot be made according to this drawing and are indicated for greater ease of use of the drawing.
Reference dimensions in the drawing are marked with a “*” sign, and in technical requirements write down “* Dimensions for reference.” If all the dimensions in the drawing are for reference, they are not marked with the “*” sign, and “Dimensions for reference” are written in the technical requirements.
TO reference sizes The following sizes apply:
- one of the sizes of a closed dimensional chain (Figure 3.40);
- dimensions transferred from drawings - blanks (Figure 3.41);
- dimensions that determine the position of part elements to be processed on another part (Figure 3.42);
Figure 3.40
Figure 3.41
Figure 3.42
- dimensions on the assembly drawing, which determine the limiting positions of individual structural elements, for example, piston stroke, engine valve rod stroke internal combustion and so on.;
- dimensions on the assembly drawing, parts transferred from the drawing and used as installation and connecting parts;
- dimensions on the assembly drawing, transferred from the drawings of parts or being the sum of the dimensions of several parts;
- dimensions of parts (elements) made of long, shaped, sheet and other rolled products, if they are fully determined by the designation of the material given in the corresponding column of the main inscription (Figure 3.43).
Figure 3.43
Notes:
- Installation and connecting dimensions are dimensions that determine the dimensions of the elements by which this product is installed at the installation site or connected to another product.
- Dimensions are dimensions that determine the maximum external (or internal) contours of the product.
| Ra5 | Ra10 | Ra20 | Ra40 | Ra5 | Ra10 | Ra20 | Ra40 | Ra5 | Ra10 | Ra20 | Ra40 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0,100 | 0,100 | 0,100 | 0,100 | 1,0 | 1,0 | 1,0 | 1,0 | 10 | 10 | 10 | 10 |
| 0,10 5 | 1,05 | 10,5 | |||||||||
| 0,110 | 0,110 | 1,1 | 1,1 | 11 | 11 | ||||||
| 0,115 | 1,15 | 11,5 | |||||||||
| 0,120 | 0,120 | 0,120 | 1,2 | 1,2 | 1,2 | 12 | 12 | 12 | |||
| 0,130 | 1,3 | 13 | |||||||||
| 0,140 | 0,140 | 1,4 | 1,4 | 14 | 14 | ||||||
| 0,150 | 1,5 | 15 | |||||||||
| 0,160 | 0,160 | 0,160 | 0,160 | 1,6 | 1 ,6 | 1,6 | 1,6 | 16 | 16 | 16 | 16 |
| 0,170 | 1,7 | 17 | |||||||||
| 0,1 80 | 0,180 | 1,8 | 1,8 | 18 | 18 | ||||||
| 0,190 | 1,9 | 19 | |||||||||
| 0,200 | 0,200 | 0,200 | 2,0 | 2,0 | 2,0 | 20 | 20 | 20 | |||
| 0,210 | 2,1 | 21 | |||||||||
| 0,220 | 0 ,220 | 2,2 | 2,2 | 22 | 22 | ||||||
| 0,240 | 2,4 | 24 | |||||||||
| 0,250 | 0,250 | 0,2 50 | 0,250 | 2,5 | 2,5 | 2,5 | 2,5 | 25 | 25 | 25 | 25 |
| 0,260 | 2,6 | 26 | |||||||||
| 0,280 | 0,280 | 2,8 | 2,8 | 28 | 28 | ||||||
| 0,300 | 3,0 | 30 | |||||||||
| 0,320 | 0,320 | 0,320 | 3,2 | 3,2 | 3,2 | 32 | 32 | 32 | |||
| 0,340 | 3,4 | 34 | |||||||||
| 0,360 | 0,360 | 3,6 | 3,6 | 36 | 36 | ||||||
| 0,380 | 3,8 | 38 | |||||||||
| 0,400 | 0,400 | 0,400 | 0,400 | 4,0 | 4,0 | 4,0 | 4,0 | 40 | 40 | 40 | 40 |
| 0,420 | 4,2 | 42 | |||||||||
| 0,450 | 0,450 | 4, 5 | 4,5 | 45 | 4 5 | ||||||
| 0,480 | 4,8 | 48 | |||||||||
| 0,500 | 0,500 | 0,500 | 5,0 | 5,0 | 5,0 | 50 | 50 | 50 | |||
| 0,530 | 5,3 | 53 | |||||||||
| 0,560 | 0,560 | 5,6 | 5,6 | 56 | 56 | ||||||
| 0,600 | 6,0 | 60 | |||||||||
| 0,630 | 0,630 | 0,630 | 0,630 | 6,3 | 6,3 | 6,3 | 6,3 | 63 | 63 | 63 | 63 |
| 0,670 | 6,7 | 67 | |||||||||
| 0,710 | 0,710 | 7,1 | 7,1 | 71 | 71 | ||||||
| 0,750 | 7, 8 | 75 | |||||||||
| 0,800 | 0,800 | 0,800 | 8,0 | 8,0 | 8,0 | 80 | 80 | 80 | |||
| 0,850 | 8,5 | 85 | |||||||||
| 0,900 | 0,900 | 9,0 | 9,0 | 90 | 90 | ||||||
| 0,950 | 9,5 | 95 | |||||||||
| 100 | 100 | 100 | 100 | 160 | 160 | 160 | 160 | 250 | 250 | 250 | 250 |
| 105 | 170 | 260 | |||||||||
| 110 | 110 | 180 | 280 | 280 | |||||||
| 120 | 190 | 300 | |||||||||
| 125 | 125 | 125 | 200 | 200 | 200 | 320 | 320 | 320 | |||
| 130 | 210 | 340 | |||||||||
| 140 | 140 | 220 | 220 | 360 | 360 | ||||||
| 150 | 240 | 380 |
In cases where it is necessary to indicate the diameter size, use a sign in the form of a circle with a line “Ø”. This symbol is placed before the size number.
Examples of using the diameter sign:
Diameter signs on cylindrical and conical rotating parts
Dimensions to be applied when there is not enough space
on the dimension line
Designation of dimensions when there is not enough space
for arrows
Diameter is the length of a straight segment connecting the surface of a circle. The diameter segment, in any case, passes only through the center of the circle. It is usually designated by the Latin letter “D” or the sign “Ø”. If the radius of a circle is multiplied by two, the sum is the diameter. All volumetric bodies that have a spherical shape, as well as those where at least one of the possible sections is a circle, are designated by diameter symbols. Word " diameter" comes from Greek word « diametros" - diameter.
Example of four hole designation
with diameter indication
On technical drawings, diameters are indicated by a symbol in the form of a crossed out circle “Ø”. This sign is placed in front of the dimensional numbers of parts, which can be either cylindrical or conical.
In cross-section, the cone is a right triangle, one of the legs of which is parallel or parallel to the body of rotation. Its parameters are designated as follows: “D” – larger diameter, “d” – smaller diameter, “L” – length. In the drawing, the diameters of the cone are indicated by numbers, preceded by the signs “Ø” and the numerical value of the length without letter designations.
To the most common parts with cylindrical surfaces, include shafts for various purposes. Cylindrical bodies formed by rotating a rectangle around one of its sides are designated by diameter. Smooth shafts have some design features, and are divided into varieties: straight, stepped one-sided, stepped double-sided and heavy. For example, the shafts of asynchronous motors, in which the rotor is mated to the shaft by pressing to its largest diameter, and on both sides there are steps for bearings, fans, and pulleys. Double-sided stepped shafts can also be found in various mechanisms where any other design features are required. Cylindrical parts, as a rule, have a common maximum length And outside diameter. Depending on the specific configuration of a particular product, its composition may include such elements as internal and external grooves, steps, recesses, etc. different diameters the values of which are preceded by the signs “Ø”.
An example of applying a diameter sign
on a spherical surface
Parts with conical surfaces include tool adapter bushings, in which the outer and inner surface conical These bushings provide high accuracy centering and high-speed tool changing with sufficient rigidity when used on machine tools. Adapter sleeves come in short and long versions.
Tapered tool parts of this type are called " Morse cone"and are divided into numbers. The angles, lengths and diameters of adapter bushings can be taken from special tables. Tabular data uses letter designations such as – “d” smaller diameter, “D” large diameter, “L” is the length of the part. In the drawings, diameters and lengths are indicated digital values, and the “Ø” sign is placed before the diameter numbers.
« Morse cone» – in addition to adapter bushings, it is used in the manufacture of twist drill shanks, end mills, fixtures and mandrels. Tool cones are fixed due to elastic and plastic deformation. To implement such connections in the spindles of milling and turning machines, there are conical holes for installation auxiliary tool. In addition, lathe The tailstock quill has the same conical hole.
Used in technology a large number of parts and their elements are designated by the diameter sign. For standard diameter sizes, a parametric series is used, which includes standard sizes. During development technical products calculated diameters are rounded to their nearest values. When indicated on technical drawings, the diameter sign must be accompanied by the axis designation with a dash-dotted line, which indicates round section part area.
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ESKD GOST 2.307-68 Drawing dimensions and maximum deviations
In order to rationally apply and correctly read dimensions, you need to study some conventions established by GOST 2.307-68 “Applying dimensions and maximum deviations”. Let's consider some of the main provisions of this standard and recommendations of reference and educational literature:
Primary requirements
Applying dimensions
Drawing limit deviations
Primary requirements
To determine the size of the depicted product and its elements, use the dimensional numbers printed on the drawing.
The exception is the cases provided for in GOST 2.414-75; GOST 2.417-78; GOST 2.419-68, when the size of a product or its elements is determined from images made with a sufficient degree of accuracy
The required accuracy of the product during manufacturing is specified by indicating on the drawing the maximum deviations of dimensions, as well as the maximum deviations of shape and Total The dimensions in the drawing should be minimal, but sufficient for the manufacture and control of the product.
Reference dimensions in the drawing are marked with a “*” sign, and in the technical requirements they write: “* Dimensions for reference.” If all the dimensions in the drawing are for reference, they are not marked with the “*” sign, but in the technical requirements they write: “Dimensions for reference.”
On the drawings of products in sizes that are technically difficult to control; put the “*” sign, and in the technical requirements the inscription “Provision dimensions” is placed. instr." This inscription means that the execution of the size specified in the drawing with a maximum deviation must be guaranteed by the size of the tool or the corresponding technological process.
It is not allowed to repeat the dimensions of the same element in different images, technical requirements, title block and specifications. The exception is reference dimensions (transferred from drawings of blank products, dimensions of parts (elements) from long, shaped, sheet, etc. rolled products).
If in the technical requirements it is necessary to provide a reference to the size printed on the image, then this size or the corresponding element is designated by a letter, and in the technical requirements an entry similar to that shown in Figure 1 is placed.
Linear dimensions and their maximum deviations in drawings and specifications are indicated in millimeters, without indicating a unit of measurement. If the dimensions in the drawing must be indicated not in millimeters, but in other units of measurement (centimeters, meters, etc.), then the corresponding dimensional numbers are written down with the designation of the unit of measurement (cm, m) or indicated in the technical requirements.
For dimensions and maximum deviations given in the technical requirements and explanatory notes on the drawing field, units of measurement must be indicated.
Angular dimensions and maximum deviations angular dimensions are indicated in degrees, minutes and seconds with the designation of the unit of measurement, for example: 4°; 4°30?; 12°50?30??; 0°30?40??; 0°18?; 0°5?25??; 0°0?30??; 30°±1°; 30°±10?.
For dimensional numbers use simple fractions not permitted except in inch sizes.
The dimensions that determine the location of the mating surfaces are set, as a rule, from the structural bases, taking into account the possibilities of making and controlling these dimensions.
When the elements of an object (holes, grooves, teeth, etc.) are located on the same axis or on the same circle, the dimensions that determine their relative position are applied in the following ways:
from the common base (surface, axis) - fig. 2a and b;setting the sizes of several groups of elements from several common bases - Fig. 3;setting the dimensions between adjacent elements (chain) - Fig. 4.
Figure 3. Setting the sizes of several groups of elements from several bases
Figure 4. Setting dimensions between adjacent elements (chain)
Dimensions on drawings are not allowed to be drawn in the form of a closed chain, except in cases where one of the dimensions is indicated as a reference.
The dimensions that determine the position of symmetrically located surfaces for symmetrical products are applied as shown in Figures 5 and 6.
Figure 5. An example of setting dimensions that determine the position of symmetrically located surfaces for symmetrical products
Figure 6. An example of setting dimensions that determine the position of symmetrically located surfaces for symmetrical products
For all dimensions marked on the working drawings, maximum deviations are indicated.
It is allowed not to indicate maximum deviations:
a) for dimensions that define zones of different roughness of the same surface, zones of heat treatment, coating, finishing, knurling, notches, as well as the diameters of knurled and notched surfaces. In these cases, is a sign applied directly to these dimensions? ;
b) for dimensions of product parts single production specified with an allowance for fit.
On such drawings, the “*” sign is placed in close proximity to the indicated dimensions, and in the technical requirements the following is indicated:
“* Dimensions with allowance for fit up to detail. ……..”,
“* Dimensions with allowance for fit according to drawing. ……..”,
“* Dimensions with allowance for fit on the mating part.”
Applying dimensions
To apply dimensions, extension and dimension lines and dimensional numbers are used (Fig. 7).
Figure 7. Size components
Dimension and extension lines should be made with solid thin lines. Dimension lines are limited by arrows. The size of the arrows is selected depending on the thickness of the S line of the visible contour of the object (Fig. 8) and should be approximately the same for all dimension lines of the drawing.
When applying the size of a straight segment, the dimension line is drawn parallel to this segment, and extension lines are drawn perpendicular to the dimensions (Fig. 9).
When drawing dimensions of parts similar to those shown in Figure 10, dimension lines should be drawn in the radial direction, and extension lines along circular arcs.
Figure 10. An example of a part in which dimension lines should be drawn in the radius direction, and extension lines should be drawn along circular arcs
When applying the size of an angle, the dimension line is drawn in the form of an arc with the center at its apex, and the extension lines are drawn radially (Fig. 11).
When applying dimensions, you must remember that all drawings, regardless of scale, indicate the actual dimensions of the product.
Figure 11. Example of applying an angle size
Dimensional numbers within one drawing are written in the same font size.
Dimensional numbers are applied above the dimension line, as close as possible to its middle. When drawing several parallel or concentric dimensional lines at a short distance from each other, it is recommended to place the dimensional numbers above them in a checkerboard pattern (Fig. 16).
When applying a diameter size inside a circle, the dimensional numbers are shifted relative to the middle of the dimensional lines.
Dimensional numbers of linear dimensions with different inclinations of dimension lines are placed as shown in Figure 12. If it is necessary to apply a dimension in a shaded area, the corresponding dimensional number is applied on the shelf of the leader line (Figure 13).
Angular dimensions are applied as shown in Figure 14. In the area located above the horizontal center line, dimensional numbers are placed above the dimensional lines on the side of their convexity; in the area located below the horizontal center line - from the side of the concavity of the dimension lines. It is not recommended to apply dimensional numbers in the shaded area. In this case, the dimensional numbers are indicated on horizontally applied shelves (Fig. 15).
Arrows limiting dimension lines should rest with their tip against the corresponding contour lines, or extension, or center lines.
Extension lines should extend beyond the ends of the dimensional arrows by 1...5 mm (Fig. 16).
The minimum distance between parallel dimension lines should be 7 mm, and between the dimension and contour line - 10 mm and selected depending on the size of the image and the saturation of the drawing (Fig. 16).
Figure 16. Dimensioning requirements
In the cases shown in Figure 17, dimension and extension lines are drawn so that they, together with the measured segment, form a parallelogram.
It is necessary to avoid intersections of dimension and extension lines.
It is not allowed to use contour lines, axial, center and extension lines as dimension lines.
It is allowed to draw dimension lines directly to the lines of the visible contour, axial, center and other lines.
Figure 17. An example of applying a dimension, when dimension and extension lines are drawn so that they, together with the measured segment, form a parallelogram
Extension lines are drawn from the line of the visible contour, except for cases when when drawing dimensions on an invisible contour, there is no need to draw an additional image. If a view or section of a symmetrical object or individual symmetrically located elements is depicted only up to the axis of symmetry or with a break, then the dimension lines related to these elements are drawn with a break, and the break of the dimension line is made further than the axis or break line of the object (Fig. 18).
Figure 18. Example of applying a dimension with a broken dimension line
Dimension lines may be drawn with breaks in the following cases:
a) when indicating the size of the diameter of a circle, regardless of whether the circle is depicted in full or in part, while the break in the dimension line is made further than the center of the circle (Fig. 19);
b) when drawing dimensions from a base not shown in this drawing (Fig. 20).
|
|
Figure 19. Example of plotting the diameter of a circle | Figure 20. An example of applying a size from a base not shown in this drawing |
When depicting a product with a gap, the dimension line is not interrupted (Fig. 21)
Figure 21. Applying dimensions when depicting a product with a gap
If the length of the dimension line is not sufficient to place arrows on it, then the dimension line continues to be taken out beyond the extension lines (or, accordingly, beyond the contour, axial, center, etc.) and the arrows are drawn as shown in Fig. 22.
Figure 22. Example of drawing dimension lines
If there is not enough space for arrows on dimension lines located in a chain, the arrows can be replaced with serifs applied at an angle of 45° to the dimension lines or clearly marked dots.
If there is not enough space for the arrow due to a closely located contour or extension line, the latter can be interrupted.
If there is not enough space above the dimension line to write the dimension number, then the dimensions are applied as shown in Fig. 23; if there is not enough space to apply the arrows, then they are applied as shown in Fig. 24.
Figure 23. Examples of applying dimensional numbers
Figure 24. Examples of applying dimensional numbers
The method of applying the dimensional number at different positions of the dimensional lines (arrows) in the drawing is determined the greatest convenience reading.
Dimensional numbers and maximum deviations are not allowed to be divided or crossed by any drawing lines.
It is not allowed to break the contour line to apply the dimensional number and apply dimensional numbers at the intersection of dimensional, center or center lines.
At the place where the dimensional number is applied, the axial, center lines and hatch lines are interrupted (Fig. 25 and 26).
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Figure 25. Applying dimensions on hatching | Figure 26. Example of dimensioning |
It is recommended to group dimensions related to the same structural element (groove, protrusion, hole, etc.) in one place, placing them on the image in which the geometric shape of this element is shown most fully (Fig. 27).
Figure 27. Applying dimensions related to the same structural element
When applying a radius size, place a capital letter R in front of the size number.
If, when drawing the size of the radius of an arc of a circle, it is necessary to indicate the size that determines the position of its center, then the latter is depicted as the intersection of center or extension lines.
If the radius is large, the center can be brought closer to the arc; in this case, the radius dimension line is shown with a bend at an angle of 90° (Fig. 28).
If it is not necessary to indicate the dimensions that determine the position of the center of the arc of a circle, then the radius dimension line may not be brought to the center and may be shifted relative to the center (Fig. 29).
When drawing several radii from one center, the dimension lines of any two radii are not placed on the same straight line (Fig. 30a). If the centers of several radii coincide, their dimension lines may not be brought to the center, except for the extreme ones (Fig. 30b).
The dimensions of the radii of external roundings are applied as shown in Fig. 31, internal roundings - in Fig. 32.
Rounding radii, the size of which on the drawing scale is 1 mm or less, are not shown in the drawing and their dimensions are indicated as shown in Fig. 33.
The method of applying dimensional numbers at different positions of dimensional lines (arrows) in the drawing is determined by the greatest ease of reading. Dimensions of identical radii may be indicated on common shelf, as shown in Fig. 34.
If the radii of fillets, bends, etc. are the same throughout the entire drawing or one radius is predominant, then instead of plotting the dimensions of these radii directly on the image, it is recommended to make an entry in the technical requirements like: “Fillet radii 4 mm”; “Internal bend radii 10mm”; “Unspecified radii 8 mm”, etc.
When indicating the diameter size (in all cases), the sign “? "
Before the dimensional number of the diameter (radius) of the sphere, the sign “? "(R) without the inscription "Sphere" (Fig. 35).
If it is difficult to distinguish a sphere from other surfaces in a drawing, then the word “Sphere” or the sign “? ", for example, "Sphere ? 18, ? R12".
The diameter of the sphere sign is equal to the size of the dimensional numbers in the drawing.
Figure 35. Example of applying the size of a sphere
The dimensions of the square are applied as shown in Figure 36. The height of the “ ” sign should be equal to the height of the dimensional numbers in the drawing.
Figure 36. Example of applying the size of a square
In front of the dimensional number characterizing the taper, a “ ” sign is applied, the acute angle of which should be directed towards the top of the cone (Fig. 37).
The cone sign and taper as a ratio should be marked above the center line or on the shelf of the leader line.
Figure 37. Example of taper size application
The slope of the surface should be indicated directly next to the image of the slope surface or on the shelf of the leader line in the form of a ratio (Fig. 38a), as a percentage (Fig. 38b) or in ppm (Fig. 38c). Before the dimensional number that determines the slope, the sign “
Markings of levels (height, depth) of a structure or its element from any reference level, taken as “zero” in the view and section, are placed on extension lines (or on contour lines) and are indicated by the sign “? ", made in solid thin lines, the length of the strokes is 2-4 mm at an angle of 45° to the extension line or contour line (Fig. 39a), in the top view they should be applied in a frame directly on the image or on the leader line (Fig. 39b) , or as shown in Figure 39c. Level marks are indicated in meters accurate to the third decimal place without indicating units of measurement.
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| |
A) | b) | V) |
| Figure 39. Example of drawing a level mark | ||
The dimensions of the chamfers at an angle of 45° are applied as shown in Fig. 40a.
It is allowed to indicate the dimensions of a chamfer not shown in the drawing at an angle of 45°, the size of which in the drawing scale is 1 mm or less, on the shelf of a leader line drawn from the edge (Fig. 40b).
DIMENSIONING
AND LIMIT DEVIATIONS
GOST 2.307-68
(ST SEV 1976-79, ST SEV 2180-80)
STATE STANDARD OF THE USSR UNION
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Unified system of design documentation APPLICATION OF DIMENSIONS AND LIMIT DEVIATIONS Unified system for design documentation. |
GOST (ST SEV 1976-79, |
Date of introduction 01.01.71
This standard establishes the rules for drawing dimensions and maximum deviations on drawings and other technical documents for products from all sectors of industry and construction.
1. BASIC REQUIREMENTS
The exception is the cases provided for in GOST 2.414-75; GOST 2.417-78; GOST 2.419-68, when the size of a product or its elements is determined from images made with a sufficient degree of accuracy.
The basis for determining the required accuracy of a product during manufacturing is the maximum dimensional deviations indicated in the drawing, as well as the maximum deviations of the shape and location of surfaces.
1.2. The total number of dimensions in the drawing should be minimal, but sufficient for the manufacture and control of the product.
1.3. Dimensions that cannot be made according to this drawing and are indicated for greater convenience in using the drawing are called reference.
1.4. Reference dimensions in the drawing are marked with a “*” sign, and in the technical requirements they write: “* Dimensions for reference.” If all the dimensions in the drawing are for reference, they are not marked with the “*” sign, but in the technical requirements they write: “Dimensions for reference.”
On construction drawings, reference dimensions are noted and specified only in cases provided for in the relevant documents approved in the prescribed manner.
a) one of the sizes of a closed dimensional chain. Maximum deviations of such dimensions are not indicated in the drawing (Fig.);
___________
*Dimensions for reference.
Crap. 1
b) dimensions transferred from the drawings of blank products (drawings);
___________
*Dimensions for reference.
Crap. 2
c) dimensions that determine the position of the elements of a part to be processed on another part (Fig.);
___________
1* Dimensions for reference.
2** Process on the mating part (or on the part...).
Crap. 3
d) dimensions on the assembly drawing, which determine the limiting positions of individual structural elements, for example, piston stroke, valve rod stroke of an internal combustion engine, etc.;
e) dimensions on the assembly drawing, transferred from the drawings of parts and used as installation and connecting ones;
f) overall dimensions on the assembly drawing, transferred from the drawings of parts or being the sum of the dimensions of several parts:
g) dimensions of parts (elements) made of long, shaped, sheet and other rolled products, if they are fully determined by the designation of the material given in column 3 of the main inscription.
Notes:
1. The reference dimensions specified in subparagraphs b, c, d, f, g of this paragraph may be applied both with maximum deviations and without them
2. Installation and connecting dimensions are dimensions that determine the dimensions of the elements by which this product is installed at the installation site or connected to another product.
3. Dimensions are dimensions that determine the maximum external (or internal) outline of the product.
1.6. On the drawings of products with dimensions that are technically difficult to control; put the “*” sign, and in the technical requirements the inscription “Provision dimensions” is placed. instr."
Note. This inscription means that the execution of the size specified in the drawing with a maximum deviation must be guaranteed by the size of the tool or the corresponding technological process.
In this case, the dimensions of the tool or the technological process are checked periodically during the manufacturing process of products.
Tool inspection frequency or technological process installed by the manufacturer together with the customer’s representative.
1.7. It is not allowed to repeat the dimensions of the same element in different images, technical requirements, title block and specifications. The exception is the reference dimensions given in paragraphs b and and.
If in the technical requirements it is necessary to give reference to the size marked on the image, then this size or the corresponding element is indicated by a letter, and in the technical requirements an entry similar to that shown in the drawing is placed. .
___________
1. Parallelism tolerance of the hole axes. A And B 0.05 mm.
2. Size difference IN on both sides no more than 0.1 mm.
Crap. 4
Dimensions may be repeated on construction drawings.
1.5-1.7.
1.8. Linear dimensions and their maximum deviations in drawings and specifications are indicated in millimeters, without indicating a unit of measurement.
For dimensions and maximum deviations given in the technical requirements and explanatory notes on the drawing field, units of measurement must be indicated.
(Changed edition, Amendment No. 3).
1.9. If the dimensions in the drawing must be indicated not in millimeters, but in other units of measurement (centimeters, meters, etc.), then the corresponding dimensional numbers are written down with the designation of the unit of measurement (cm, m) or indicated in the technical requirements.
In these cases, units of measurement may not be indicated on construction drawings if they are specified in the relevant documents approved in the prescribed manner
1.10. Angular dimensions and maximum deviations of angular dimensions are indicated in degrees, minutes and seconds with the designation of the unit of measurement, for example - 4°; 4°30 " ; 12°45 " 30" ; 0°30 " 40" ; 0 ° 18" ; 0 ° 5" 25" ; 0°0 " 30" ; 30°± l°; 30°±10 " .
Crap. 5
Crap. 6
1.11. For dimensional numbers, simple fractions are not allowed, with the exception of sizes in inches.
1.12. The dimensions that determine the location of the mating surfaces are set, as a rule, from the structural bases, taking into account the possibilities of making and controlling these dimensions.
1.13. When the elements of an object (holes, grooves, teeth, etc.) are located on the same axis or on the same circle, the dimensions that determine their relative position are applied in the following ways:
from the common base (surface, axis) - according to the line. a and b;
specifying the sizes of several groups of elements from several common bases - according to the drawing. V;
setting the dimensions between adjacent elements (chain) - according to the drawing. .
1.14. Dimensions on drawings are not allowed to be applied in the form of a closed chain, except in cases where one of the dimensions is indicated as a reference (see drawing).
On construction drawings, dimensions are applied in the form of a closed circuit, except for cases provided for in the relevant documents approved in the prescribed manner.
The dimensions that determine the position of symmetrically located surfaces of symmetrical products are applied as shown in Fig. And .
Crap. 7
___________
*Dimensions for reference.
Crap. 8
(Changed edition, Amendment No. 2).
1.15. For all dimensions marked on the working drawings, maximum deviations are indicated.
It is allowed not to indicate maximum deviations:
a) for dimensions that define zones of different roughness of the same surface, zones of heat treatment, coating, finishing, knurling, notches, as well as the diameters of knurled and notched surfaces. In these cases, a sign is applied directly to these dimensions » ;
b) for the dimensions of parts of individually produced products specified with an allowance for fit.
On such drawings, the “*” sign is placed in close proximity to the indicated dimensions, and in the technical requirements the following is indicated:
“* Dimensions with allowance for fit up to detail. . . . . ",
“* Dimensions with allowance for fit according to drawing. . . . . ",
“* Dimensions with allowance for fit, according to the mating part.”
On construction drawings, maximum dimensional deviations are indicated only in cases provided for in the relevant documents approved in the prescribed manner.
1.16. When making working drawings of parts manufactured by casting, stamping, forging or rolling with subsequent machining parts of the surface of the part, indicate no more than one size in each coordinate direction, connecting mechanically machined surfaces with surfaces that are not machined (drawings and ).
Crap. 9
Crap. 10
(Changed edition, Amendment No. 2).
1.17. If an element is depicted at a deviation from the image scale, then the size number should be emphasized (Fig. a).
Crap. 10a
2. DIMENSIONING
2.1. Dimensions in the drawings are indicated by dimensional numbers and dimension lines.
2.2. When applying the size of a straight segment, the dimension line is drawn parallel to this segment, and the extension lines are drawn perpendicular to the dimension lines (Fig. ).
Crap. eleven
2.3. When applying the size of an angle, the dimension line is drawn in the form of an arc with the center at its vertex, and the extension lines are drawn radially (Fig. ).
Crap. 12
2.4. When applying the size of a circular arc, the dimension line is drawn concentrically to the arc, and the extension lines are parallel to the bisector of the angle, and the sign “Ç " (crap. ).
Crap. 13
It is allowed to place extension lines of the arc size radially, and if there are also concentric arcs, it is necessary to indicate which arc the size belongs to (Fig. ).
Crap. 14
2.4a. When drawing dimensions of parts similar to those shown in Fig. a, dimension lines should be drawn in the radial direction, and extension lines should be drawn along circular arcs (Fig. a).
Crap. 14a
(Introduced additionally, Amendment No. 2).
2.5. The dimension line at both ends is limited by arrows resting on the corresponding lines, except for the cases given in paragraphs. , , and , and when drawing a radius line limited by an arrow on the side of the defined arc or fillet.
In construction drawings, instead of arrows, it is allowed to use serifs at the intersection of dimension and extension lines, and the dimension lines must protrude beyond the outer extension lines by 1 . . . 3 mm.
2.6. In the cases shown in Fig. , dimension and extension lines are drawn so that they, together with the measured segment, form a parallelogram.
Crap. 15
2.7. It is allowed to draw dimension lines directly to the lines of the visible contour, axial, center and other lines (drawing and ).
Crap. 16
Crap. 17
2.8. It is preferable to apply dimension lines outside the outline of the image.
2.9. Extension lines should extend beyond the ends of the dimension line arrows by 1. . 5 mm.
2.10. The minimum distances between parallel dimension lines should be 7 mm, and between the dimension and contour lines - 10 mm and are selected depending on the size of the image and the saturation of the drawing.
(Changed edition, Amendment No. 2).
2.11. It is necessary to avoid intersections of dimension and extension lines (see drawing).
2.12. It is not allowed to use contour lines, axial, center and extension lines as dimension lines.
2.13. Extension lines are drawn from the lines of the visible contour, except for the cases specified in paragraphs. and, and cases when, when drawing dimensions on an invisible contour, there is no need to draw an additional image.
a) when indicating the size of the diameter of a circle, regardless of whether the circle is depicted completely or partially, while the break in the dimension line is made further than the center of the circle (Fig.);
Crap. 20
b) when drawing dimensions from a base not shown in this drawing (Fig. ).
Crap. 21
2.18. When depicting a product with a gap, the dimension line is not interrupted (Fig.).
Crap. 22
2.19. The values of the elements of the dimension line arrows are selected depending on the thickness of the lines of the visible contour and they are drawn approximately the same throughout the entire drawing. The shape of the arrow and the approximate relationship of its elements are shown in Fig. .
Crap. 23
(Changed edition, Amendment No. 2).
Crap. 43b
If the radii of fillets, bends, etc. are the same throughout the entire drawing or one radius is predominant, then instead of plotting the dimensions of these radii directly on the image, it is recommended to make an entry in the technical requirements like: “Fillet radii 4 mm”; “Internal bend radii 10 mm”; “Unspecified radii 8 mm”, etc.
2.35, 2.36. (Changed edition, Amendment No. 2).
2.37. When indicating the diameter size (in all cases), the sign “Æ ».
2.38. Before the dimensional number of the diameter (radius) of the sphere, the sign is also appliedÆ (R) without the inscription “Sphere” (drawing). If it is difficult to distinguish a sphere from other surfaces in the drawing, then before the dimension number of the diameter (radius) it is allowed to put the word “Sphere” or the sign O, for example, “SphereÆ 18, OR12."
The diameter of the sphere sign is equal to the size of the dimensional numbers in the drawing.
Crap. 44
2.39. The dimensions of the square are applied as shown in Fig. , and a.
Crap. 45
Crap. 46
Crap. 46a
The height of the □ sign must be equal to the height of the dimensional numbers on the drawing.
2.38, 2.39 (Changed edition, Amendment No. 2).
2.40. Before the dimensional number characterizing the taper, the sign “< ", the acute angle of which should be directed towards the top of the cone (Fig. ).
Crap. 47
The cone sign and taper as a ratio should be marked above the center line or on the shelf of the leader line.
2.41. The slope of the surface should be indicated directly next to the image of the slope surface or on the shelf of the leader line in the form of a ratio (Fig. a), as a percentage (Fig. b) or in ppm (Fig. c). Before the dimensional number that determines the slope, the sign “< ", the acute angle of which should be directed towards the slope.
Crap. 48
2.42. Markings of levels (height, depth) of a structure or its element from any reference level, taken as “zero” in the view and section, are placed on extension lines (or on contour lines) and are indicated by the sign “¯ ", made in solid thin lines, the length of the strokes is 2 - 4 mm at an angle of 45° to the extension line or contour line (Fig. a), in the top view they should be applied in a frame directly on the image or on the leader line (Fig. b) , or as shown in fig. A.
Crap. 49
Level marks are indicated in meters accurate to the third decimal place without indicating the unit of measurement.
2.43. The dimensions of the chamfers at an angle of 45° are applied as shown in Fig. .
Crap. 50
It is allowed to indicate the dimensions of a chamfer not shown in the drawing at an angle of 45°, the size of which in the drawing scale is 1 mm or less, on the shelf of a leader line drawn from the edge (Fig. a).
Crap. 50a
The dimensions of chamfers at other angles are indicated according to the general rules - linear and angular dimensions (drawings a and b) or two linear dimensions (drawing c).
Crap. 51
2.40-2.43. (Changed edition, Amendment No. 2).
2.44. The dimensions of several identical elements of the product, as a rule, are applied once, indicating the number of these elements on the shelf with a leader line (Fig. a).
It is allowed to indicate the number of elements, as shown in Fig. b.
Crap. 52
2.45. When applying the dimensions of elements evenly spaced around the circumference of the product (for example, holes), instead of the angular dimensions that determine the relative position of the elements, only their number is indicated (Fig. -).
Crap. 53
Crap. 54
Crap. 55
2.46. The dimensions of two symmetrically located elements of the product (except for holes) are applied once without indicating their number, grouping, as a rule, all dimensions in one place (drawings and ).
Crap. 56
___________
*Dimensions for reference.
Crap. 57
The number of identical holes is always indicated in full, and their dimensions are indicated only once.
(Changed edition, Amendment No. 2).
2.47. When applying dimensions that determine the distance between evenly spaced identical elements of a product (for example, holes), it is recommended, instead of dimensional chains, to apply the size between adjacent elements and the size between extreme elements in the form of the product of the number of spaces between the elements and the size of the gap (Fig.).
Crap. 58
2.47a. It is allowed not to indicate on the drawing the dimensions of the radius of the circular arc of mating parallel lines (Fig. a).
Crap. 58a
(Introduced additionally, Amendment No. 2).
2.48. With a large number of dimensions applied from a common base, it is allowed to apply linear and angular dimensions, as shown in Fig. and , in this case, a general dimension line is drawn from the “0” mark and dimension numbers are applied in the direction of the extension lines at their ends.
Crap. 59
Crap. 60
2.48a. Dimensions of diameters of a cylindrical product complex configuration may be applied as shown in Fig. A.
Crap. 60a
(Introduced additionally, Amendment No. 2).
2.49. If there are a large number of similar elements of the product, unevenly located on the surface, it is allowed to indicate their dimensions in a summary table, using the coordinate method of drawing holes with their designation in Arabic numerals (drawing), or the designation of elements of the same type in capital letters(Fig. a).
Crap. 61
Crap. 61 a
|
Hole designation |
Size, mm |
|
2.50. Identical elements located in different parts of the product (for example, holes) are considered as one element if there is no gap between them (Fig. a) or if these elements are connected by thin solid lines (Fig. b).
In the absence of these conditions, indicate the total number of elements (Fig. c).
Crap. 62
2.51. If identical product elements (for example, holes) are located on different surfaces and shown in different images, the number of these elements is recorded separately for each surface (Fig. ).
Crap. 63
It is allowed to repeat the dimensions of identical elements of a product or their groups (including holes) lying on the same surface only if they are significantly removed from each other and are not related to each other by size (Fig. and ).
Crap. 64
Crap. 65
2.49-2.51. (Changed edition, Amendment No. 2).
2.52. If the drawing shows several groups of holes of similar sizes, it is recommended to mark the same holes with one of the symbols shown in the drawing. . It is allowed to use other symbols.
Crap. 66
Holes indicate conventional signs in the image that shows the dimensions that determine the position of these holes.
On construction drawings, it is allowed to outline identical groups of holes with a solid thin line with an explanatory inscription.
2.53 When designating identical holes with conventional signs, the number of holes and their sizes may be indicated in the table (Fig. ).
Crap. 67
(Changed edition, Amendment No. 2).
2.54. When depicting a part in one projection, the size of its thickness or length is applied as shown in Fig. .
Crap. 68
2.55. Part or hole dimensions rectangular section can be indicated on the shelf by leader lines with the dimensions of the sides through the multiplication sign. In this case, in the first place the size of the side of the rectangle from which the leader line is drawn should be indicated (Fig. a).
Crap. 68a
(Changed edition, Amendment No. 2).
3. APPLICATION OF LIMITED DIMENSIONS
A general record of maximum deviations of dimensions with unspecified tolerances must contain symbols of maximum deviations of linear dimensions in accordance with GOST 25346-89 (for deviations by qualifications) or in accordance with GOST 25670-83 (for deviations by accuracy classes). Symmetrical maximum deviations assigned according to qualifications should be designated indicating the qualification number.
Designations of one-sided maximum deviations for qualifications assigned only to round holes and shafts (option 4 according to GOST 25670-83) are supplemented with a diameter sign (Æ ).
Examples of general records corresponding to options in accordance with GOST 25670-83 for grade 14 and (or) accuracy class “medium” are given in table. :
Table 1
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Example entry symbols |
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N 14, h 14, or N 14, h 14, |
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+t 2 , -t 2, |
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Æ N 14, Æ h 14, or Æ N 14, Æ h 14, |
Notes:
1. It is allowed to supplement entries about unspecified maximum deviations of dimensions with explanatory words, for example, “Unspecified maximum deviations of dimensions: N 14, h 14, ".
