Drawing and reading dimensions in part drawings. Representation of holes and similar elements Designation of thread depth
This has been discussed a lot here. I will repeat in a general sense why it is necessary to show the transition lines conditionally: 1. To make the drawing readable. 2. From the transition lines, shown conditionally, you can set dimensions that are often no longer in any view and section. Here's an example. There is a difference? 1. As now can be displayed in all the listed CAD systems. And here's how to display. The transition lines are shown conditionally and the dimensions are shown, which in other display modes of the transition lines simply cannot be set. Why was this required by the normative controller? Yes, just so that the drawings have a familiar look after many years of work in 2D and are easy to read, especially by the customer who approves them.
This is true :) this is nonsense :) in TF you can do this and so \u003d) there will be no tangible difference in speed, you can even then take any copy to repaint, change holes, delete holes, whatever ... and the array will still remain an array - it will be possible to change the number of copies, direction, etc., cut the video or believe it? :) That's right, but what is the problem? Translate as SW splines by points into splines by poles or what, if you think about this also some change in the original geometry - there are no comments on this? :) as I understand it, TF only 1 to 1 and translates, the rest can already be configured in the TF template before export in DWG - see the figure under the spoiler, or scale it in the form of AC, which, in principle, does not contradict the main methods of working with AutoCAD, and since in view of the prevalence of AC in the early stages of the peak of the popularity of CAD implementation, the age generation is even more familiar with this: And if still to get to the bottom of the export / import capabilities of different CAD systems: 1) how can I export only selected lines from a 2D SW drawing to DWG? (from 3D documents, more or less SW is adapted, but you still have to clean the excess manually in a small preview window). Delete everything that is not needed in advance, and then export-\u003e somehow not modern, not youthful :) 2) And vice versa, as selected lines in AutoCAD, quickly import into SW (for example, for a sketch, or just as a set of lines for drawing)? (for TF: selected a set of necessary lines in AC -ctrl + c and then in TF just ctrl + v - everything)
What detail are we talking about, otherwise it may not be necessary to mirror this detail, but simply tie it differently and it will be just right. A mirror part is the same configuration just created by the machine, you can make the configuration of the part yourself and in some cases it may turn out to be more elegant, it is also easier to edit later.
from 01.01.80
This standard establishes the rules for indicating the tolerances of the shape and location of surfaces on the drawings of products of all industries. Terms and definitions of the tolerances of the shape and location of surfaces - according to GOST 24642-81. The numerical values \u200b\u200bof the tolerances of the shape and location of surfaces are in accordance with GOST 24643-81. The standard is fully consistent with ST SEV 368-76.
1. GENERAL REQUIREMENTS
1.1. The tolerances of the shape and location of surfaces are indicated in the drawings with symbols. The type of tolerance of the shape and location of surfaces must be indicated in the drawing by the signs (graphic symbols) given in the table.|
Tolerance group |
Type of admission |
|
| Shape tolerance | Straightness tolerance | |
| Flatness tolerance | ||
| Roundness tolerance | ||
| Cylindrical tolerance | ||
| Longitudinal profile tolerance | ||
| Location tolerance | Parallelism tolerance | |
| Squareness tolerance | ||
| Tilt tolerance | ||
| Alignment tolerance | ||
| Symmetry tolerance | ||
| Positional tolerance | ||
| Intersection tolerance, axes | ||
| Overall shape and position tolerances | Radial runout tolerance Face runout tolerance Runout tolerance in a given direction | |
| Full radial runout tolerance Full face runout tolerance | ||
| Shape tolerance of a given profile | ||
| Tolerance of the shape of a given surface |
2. APPLICATION OF TOLERANCE LABELS
2.1. With a conventional designation, data on the tolerances of the shape and location of surfaces are indicated in a rectangular frame divided into two or more parts (Fig. 1, 2), in which they place: in the first - the tolerance sign according to the table; in the second - the numerical value of the tolerance in millimeters; in the third and subsequent ones - the letter designation of the base (s) or the letter designation of the surface with which the location tolerance is associated (clauses 3.7; 3.9).Heck. 1
Heck. 2
2.2. Frames should be made with solid thin lines. The height of numbers, letters and signs that fit into the frames must be equal to the font size of the dimension numbers. A graphic representation of the frame is given in the obligatory Appendix 1. 2.3. The frame is placed horizontally. If necessary, the vertical arrangement of the frame is allowed. It is not allowed to cross the frame with any lines. 2.4. The frame is connected to the element to which the tolerance belongs, with a solid thin line ending with an arrow (Fig. 3).
Heck. 3
The connecting line can be straight or broken, but the direction of the segment of the connecting line ending with an arrow must correspond to the direction of the deflection measurement. The connecting line is taken from the frame, as shown in fig. 4.
Heck. 4
If necessary, it is allowed to: draw a connecting line from the second (last) part of the frame (Fig. 5 and); end the connecting line with an arrow and from the side of the material of the part (Fig. 5 b).
Heck. five
2.5. If the tolerance refers to the surface or its profile, then the frame is connected to the contour line of the surface or its continuation, while the connecting line should not be a continuation of the dimension line (Fig. 6, 7).
Heck. 6
Heck. 7
2.6. If the tolerance refers to an axis or plane of symmetry, then the connecting line should be a continuation of the dimension line (Fig. 8 and, b). If there is not enough space, the arrow of the dimension line may be combined with the arrow of the connecting line (Fig. 8 in).
Heck. 8
If the size of the element has already been specified once, then it is not indicated on the other dimension lines of this element used to symbolize the tolerance of the shape and location. Dimension line without dimension should be considered as an integral part of the symbol for the tolerance of the shape or location (Fig. 9).
Heck. nine
Heck. ten
2.7. If the tolerance refers to the lateral sides of the thread, then the frame is connected to the image in accordance with Fig. ten and... If the tolerance refers to the thread axis, then the frame is connected to the image in accordance with Fig. ten b... 2.8. If the tolerance refers to a common axis (plane of symmetry) and it is clear from the drawing for which surfaces this axis (plane of symmetry) is common, then the frame is connected to the axis (plane of symmetry) (Fig. 11 and, b).
Heck. eleven
2.9. Before the numerical value of the tolerance, indicate: the symbol Æ, if the circular or cylindrical tolerance field is indicated with a diameter (Fig. 12 and); symbol R , if the circular or cylindrical tolerance field is indicated by the radius (Fig. 12 b); symbol T,if the tolerances of symmetry, intersection of axes, the shape of a given profile and a given surface, as well as positional tolerances (for the case when the positional tolerance field is limited to two parallel straight lines or planes) are indicated in diametrical terms (Fig. 12 in); symbol T / 2for the same types of tolerances, if they are indicated in radial expression (Fig. 12 r); the word "sphere" and the symbols Æ or R if the tolerance field is spherical (Fig. 12 d).
Heck. 12
2.10. The numerical value of the tolerance of the shape and location of surfaces, indicated in the frame (Fig. 13 and), refers to the entire length of the surface. If the tolerance refers to any part of the surface of a given length (or area), then the specified length (or area) is indicated next to the tolerance and is separated from it by an oblique line (Fig. 13 b, in), which should not touch the frame. If it is necessary to assign a tolerance for the entire surface length and for a given length, then the tolerance for a given length is indicated under the tolerance for the entire length (Fig. 13 r).
Heck. 13
(Modified edition, Amendment No. 1). 2.11. If the tolerance should refer to a section located at a certain place of the element, then this section is indicated by a dash-dot line and limited in size according to the drawing. fourteen.
Heck. fourteen
2.12. If it is necessary to set the protruding tolerance field of the location, then after the numerical value of the tolerance, indicate the symbol. The contour of the protruding part of the normalized element is limited by a thin solid line, and the length and location of the protruding tolerance field - by dimensions (Fig. 15).
Heck. 15
2.13. Inscriptions supplementing the data given in the tolerance frame should be applied above the frame below it or as shown in fig. sixteen.
Heck. sixteen
(Modified edition, Amendment No. 1). 2.14. If for one element it is necessary to set two different types of tolerance, then it is allowed to combine the frames and arrange them according to the features. 17 (upper designation). If for a surface it is required to indicate at the same time the designation of the tolerance of the shape or location and its letter designation used to normalize another tolerance, then frames with both designations can be placed side by side on the connecting line (Fig. 17, lower designation). 2.15. Repeating the same or different types of tolerances, denoted by the same sign, having the same numerical values \u200b\u200band referring to the same bases, are allowed to be indicated once in the frame, from which one connecting line departs, then branched out to all normalized elements (Fig. 18).
Heck. 17
Heck. 18
2.16. The tolerances of the shape and location of symmetrically located elements on symmetrical parts are indicated once.
3. DESIGNATION OF BASES
3.1. The bases are indicated by a blackened triangle, which is connected with a connecting line to the frame. When making drawings with the help of computer output devices, the triangle denoting the base is allowed not to be blackened. The base triangle should be equilateral, with a height approximately equal to the font size of the dimension numbers. 3.2. If the base is a surface or its profile, then the base of the triangle is placed on the contour line of the surface (Fig. 19 and) or on its continuation (Fig. 19 b). In this case, the connecting line should not be a continuation of the dimension line.
Heck. nineteen
3.3. If the base is an axis or plane of symmetry, then the triangle is placed at the end of the dimension line (Fig. 18). In case of lack of space, the arrow of the dimension line may be replaced with a triangle denoting the base (Fig. 20).
Heck. 20
If the base is a common axis (Fig. 21 and) or the plane of symmetry (Fig. 21 b) and from the drawing it is clear for which surfaces the axis (plane of symmetry) is common, then the triangle is placed on the axis.
Heck. 21
(Modified edition, Amendment No. 1). 3.4. If the base is the axis of the center holes, then the inscription "Center axis" is made next to the designation of the base axis (Fig. 22). It is allowed to designate the base axis of the center holes in accordance with the drawing. 23.
Heck. 22
Heck. 23
3.5. If the base is a certain part of the element, then it is indicated by a dash-dot line and limited in size in accordance with the drawing. 24. If the base is a certain place of the element, then it must be determined by the dimensions according to the drawing. 25.
Heck. 24
Heck. 25
3.6. If there is no need to select one of the surfaces as the base pi, then the triangle is replaced with an arrow (Fig. 26 b). 3.7. If the connection of the frame to the base or other surface, to which the deviation of the location belongs, is difficult, the surface is designated by a capital letter inscribed in the third part of the frame. The same letter is inscribed in a frame, which is connected to the designated surface by a line, which is filled with a triangle, if the base is designated (Fig. 27 and), or an arrow if the designated surface is not a base (Fig. 27 b). In this case, the letter should be placed parallel to the main inscription.
Heck. 26
Heck. 27
3.8. If the size of the element has already been specified once, then it is not indicated on the other dimension lines of this element used for the reference designation of the base. Dimension line without size should be considered as an integral part of the base symbol (Fig. 28).
Heck. 28
3.9. If two or more elements form a combined base and their sequence does not matter (for example, they have a common axis or plane of symmetry), then each element is designated independently and all letters are inscribed in a row in the third part of the frame (Fig. 25, 29). 3.10. If it is necessary to set the tolerance of the location relative to the set of bases, then the letter designations of the bases are indicated in the independent parts (third and further) of the frame. In this case, the bases are written in descending order of the number of degrees of freedom deprived by them (Fig. 30).
Heck. 29
Heck. thirty
4. INDICATION OF NOMINAL POSITIONING
4.1. Linear and angular dimensions that determine the nominal location and (or) the nominal shape of the elements limited by the tolerance, when assigning positional tolerance, slope tolerance, tolerance of the shape of a given surface or a given profile, are indicated on the drawings without limit deviations and are enclosed in rectangular frames (Fig. 31 ).
Heck. 31
5. IDENTIFICATION OF DEPENDENT TOLERANCES
5.1. The dependent tolerances of the shape and location are indicated by a conventional sign, which is placed: after the numerical value of the tolerance, if the dependent tolerance is associated with the actual dimensions of the element in question (Fig. 32 and); after the letter designation of the base (Fig. 32 b) or without letter designation in the third part of the frame (Fig. 32 r), if the dependent tolerance is related to the actual dimensions of the base feature; after the numerical value of the tolerance and the letter designation of the base (Fig. 32 in) or without letter designation (Fig. 32 d), if the dependent tolerance is related to the actual dimensions of the considered and base elements. 5.2. If the location or shape tolerance is not specified as dependent, then it is considered independent.
Heck. 32
APPENDIX 1
Mandatory
SHAPE AND SIZE OF SIGNS
APPENDIX 2
Reference
EXAMPLES OF INDICATION ON THE DRAWINGS OF TOLERANCES FOR THE SHAPE AND POSITION OF SURFACES
|
Type of admission |
Indication of tolerances of form and location by symbol |
Explanation |
| 1. Straightness tolerance | The straightness tolerance of the generatrix of the cone is 0.01 mm. | |
|
|
Straightness tolerance of the hole axis Æ 0.08 mm (dependent tolerance). | |
|
|
The surface straightness tolerance is 0.25 mm over the entire length and 0.1 mm over a length of 100 mm. | |
|
|
The surface straightness tolerance in the transverse direction is 0.06 mm, in the longitudinal direction is 0.1 mm. | |
| 2. Flatness tolerance |
|
The surface flatness tolerance is 0.1 mm. |
|
|
The surface flatness tolerance is 0.1 mm on an area of \u200b\u200b100 ´ 100 mm. | |
|
|
The flatness tolerance of surfaces relative to the common adjacent plane is 0.1 mm. | |
|
|
The flatness tolerance of each surface is 0.01 mm. | |
| 3. Roundness tolerance |
|
Shaft roundness tolerance 0.02 mm. |
| The roundness tolerance of the cone is 0.02 mm. | ||
| 4. Cylindrical tolerance |
|
Shaft cylindricity tolerance 0.04 mm. |
|
|
Shaft cylindricity tolerance 0.01 mm over a length of 50 mm. Shaft roundness tolerance 0.004 mm. | |
| 5. Tolerance of the profile of the longitudinal section |
|
Shaft roundness tolerance 0.01 mm. The tolerance of the profile of the longitudinal section of the shaft is 0.016 mm. |
|
|
The tolerance of the profile of the longitudinal section of the shaft is 0.1 mm. | |
| 6. Parallelism tolerance |
|
Surface parallelism tolerance relative to surface AND0.02 mm. |
|
|
Tolerance of parallelism of the common adjacent plane of surfaces relative to the surface AND0.1 mm. | |
|
|
Parallelism tolerance of each surface relative to the surface AND0.1 mm. | |
|
|
The tolerance of parallelism to the axis of the hole relative to the base is 0.05 mm. | |
|
|
The tolerance of parallelism of the axes of the holes in the common plane is 0.1 mm. The misalignment of the axes of the holes is 0.2 mm. Base - hole axis AND. | |
|
|
Tolerance of parallelism of the hole axis relative to the hole axis AND00.2 mm. | |
| 7. Perpendicularity tolerance |
|
Surface perpendicularity tolerance to surface AND0.02 mm. |
|
|
Perpendicularity tolerance of the hole axis relative to the hole axis AND0.06 mm. | |
|
|
Tolerance of perpendicularity of the axis of the protrusion relative to the surface AND Æ 0.02 mm. | |
| The perpendicularity tolerance of the smallpox protrusion relative to the base is 0, l mm. | ||
|
|
The perpendicularity tolerance of the axis of the protrusion in the transverse direction is 0.2 mm, in the longitudinal direction is 0.1 mm. Base - base | |
|
|
The perpendicularity tolerance of the hole axis relative to the surface is Æ 0.1 mm (dependent tolerance). | |
| 8. Tilt tolerance |
|
Surface slope tolerance relative to surface AND0.08 mm. |
|
|
Hole axis tilt tolerance relative to surface AND0.08 mm. | |
| 9. Alignment tolerance |
|
Alignment tolerance of the hole relative to the hole Æ 0.08 mm. |
|
|
The alignment tolerance of the two holes relative to their common axis is Æ 0.01 mm (dependent tolerance). | |
| 10. Tolerance of symmetry |
|
Symmetry tolerance of the groove T0.05 mm. Base - plane of symmetry of surfaces AND |
|
|
Hole symmetry tolerance T0.05 mm (dependent tolerance). The base is the plane of symmetry of the surface A. | |
|
|
Symmetry tolerance of smallpox holes relative to the general plane of symmetry of the grooves AB T 0.2 mm and relative to the general plane of symmetry of the grooves VG T0.1 mm. | |
| 11. Positional tolerance |
|
Positional tolerance of the hole axis Æ 9.06 mm. |
|
|
Positional tolerance of hole axes отверст 0.2 mm (dependent tolerance). | |
|
|
Positional tolerance of axes of 4 holes Æ 0.1 mm (dependent tolerance). Base - hole axis AND(tolerance dependent). | |
|
|
Positional tolerance of 4 holes Æ 0.1 mm (dependent tolerance). | |
|
|
Positional tolerance of 3 threaded holes Æ 0.1 mm (dependent tolerance) in the area located outside the part and protruding 30 mm from the surface. | |
| 12. Axis intersection tolerance |
|
Hole Intersection Tolerance T0.06 mm |
| 13. Radial runout tolerance |
|
The radial runout tolerance of the shaft relative to the cone axis is 0.01 mm. |
|
|
Radial runout tolerance of the surface relative to the common axis is superficial AND and B 0.1 mm | |
|
|
Radial runout tolerance of a surface area relative to the hole axis AND0.2 mm | |
|
|
Hole radial runout tolerance 0.01 mm First base - surface L.The second base is the axis of surface B. The tolerance of end runout relative to the same bases is 0.016 mm. | |
| 14. Tolerance of face runout |
|
End runout tolerance at a diameter of 20 mm relative to the surface axis AND0.1 mm |
| 15. Runout tolerance in a given direction |
|
Runout tolerance of the cone relative to the hole axis ANDin the direction perpendicular to the generatrix of the cone 0.01 mm. |
| 16. Tolerance of full radial runout |
|
Radial runout tolerance relative to the common axis is superficial ANDand B0.1 mm. |
| 17. Tolerance of full face runout |
|
The tolerance of the full face runout of the surface relative to the surface axis is 0.1 mm. |
| 18. Tolerance of the shape of a given profile |
|
Shape tolerance of a given profile T0.04 mm. |
| 19. Tolerance of the shape of a given surface |
|
Tolerance of the shape of a given surface relative to surfaces A, B, C, T 0.1 mm. |
| 20. Total tolerance of parallelism and flatness |
|
The total tolerance of parallelism and flatness of the surface relative to the base is 0.1 mm. |
| 21. Total perpendicularity and flatness tolerance |
|
The total tolerance of squareness and flatness of the surface relative to the base is 0.02 mm. |
| 22. Total slope and flatness tolerance |
|
The total tolerance of the slope and flatness of the surface relative to the base 0.05 mi |
In previously issued documentation, the tolerances of alignment, symmetry, and displacement of the axes from the nominal position (positional tolerance), indicated by signs, respectively 
or text in the specification should be understood as radial tolerances. 2. An indication of the tolerances of the shape and location of surfaces in text documents or in the technical requirements of the drawing should be given by analogy with the text of the explanation to the symbols for the tolerances of the shape and location given in this annex. In this case, the surfaces to which the tolerances of the shape and location belong or which are taken as a base should be designated by letters or their design names should be carried out. It is allowed to indicate a sign instead of the words "tolerance dependent" and instead of indications before the numerical value of symbols Æ; R ; T; T / 2 notation in text, for example, "axis positional tolerance of 0.1 mm in diametric terms" or "symmetry tolerance of 0.12 mm in radial terms". 3. In the newly developed documentation, an entry in the technical requirements for the tolerances of ovality, taper, barrel and saddle shape should be, for example, the following: “Tolerance of ovality of the surface AND0.2 mm (half difference of diameters). In the technical documentation developed before 01.01.80, the limiting values \u200b\u200bof ovality, taper, barrel and saddle shape are defined as the difference between the largest and smallest diameters. (Modified edition, Amendment No. 1).
The thread is made with a cutting tool with the removal of a layer of material, knurling - by extrusion of screw protrusions, casting, pressing, stamping, depending on the material (metal, plastic, glass) and other conditions.
Due to the device of the thread-cutting tool (for example, a tap, Fig. 8.14; dies, Fig. 8.15) or when the cutter is retracted, when moving from a surface section with a thread of a full profile (sections l) to a smooth one, a section is formed on which the thread seems to descend to no (sections l1), a thread runaway is formed (Fig. 8.16). If the thread is made to a certain surface that does not allow bringing the tool to the stop to it, then a thread undercut is formed (Fig. 8.16.6, c). Runaway plus undercut form a thread undercut. If it is required to make a thread of a full profile, without a runaway, then a groove is made to withdraw the thread-forming tool, the diameter of which for the external thread should be slightly less than the internal thread diameter (Figure 8.16, d), and for the internal thread - slightly larger than the external thread diameter (Fig. 8.17). At the beginning of the thread, as a rule, a conical chamfer is made, which protects the extreme turns from damage and serves as a guide when connecting parts with a thread (see Fig. 8.16). The chamfer is performed prior to threading. The dimensions of chamfers, escapes, undercuts and grooves are standardized, see GOST 10549-80 * and 27148-86 (ST SEV 214-86). Fasteners. Thread exit. Run away, undercuts and grooves. Dimensions.
The creation of an accurate image of thread turns is time-consuming, so it is used in rare cases. According to GOST 2.311 - 68 * (ST SEV 284-76), in the drawings, the thread is depicted conditionally, regardless of the thread profile: on the rod - with solid main lines along the outer diameter of the thread and solid thin lines along the inner thread, for the entire length of the thread, including the chamfer ( Fig. 8.18, a). On images obtained by projection onto a plane perpendicular to the axis of the rod, an arc is drawn along the inner diameter of the thread with a solid thin line equal to 3/4 of the circle and open anywhere. In the images of the thread in the hole, the solid main and solid thin lines seem to change places (Fig. 8.18.6).
A solid thin line is applied at a distance of at least 0.8 mm from the main line (Figure 8.18), but not more than the thread pitch. The hatching in the cuts is brought to the line of the outer diameter of the thread on the rod (Figure 8.18, d) and to the line of the inner diameter in the hole (Figure 8.18.6). Chamfers on a threaded rod and in a threaded hole, which do not have a special design purpose, in projection onto a plane perpendicular to the axis of the rod or hole, are not shown (Figure 8.18). The thread boundary on the rod and in the hole is drawn at the end of the full thread profile (before the start of the runaway) with the main line (or dashed, if the thread is shown as invisible, Fig. 8.19), bringing it to the lines of the outer diameter of the thread. If necessary, the runout of the thread is depicted with thin lines , held approximately at an angle of 30 ° to the axis (Fig. 8.18, a, b).
The thread, shown as invisible, is depicted by dashed lines of the same thickness along the outer and inner diameters (Fig. 8.19). Thread length is the length of the part of the part on which the thread is formed, including the runway and chamfer. Usually, only the length l of the thread with a full profile is indicated in the drawings (Fig. 8.20, a). If there is a groove, external (see Fig. 8.16, d) or internal (see Fig. 8.17), then its width is also included in the length of the thread. If it is necessary to indicate the runway or the length of the thread with the runway, the dimensions are applied as shown in Fig. 8.17. 8.20, b, c. An undercut of the thread, made to the stop, is depicted, as shown in Fig. 8.21, a, b. Variants "c" and "d" are acceptable.
In the drawings, according to which the thread is not performed (on the assembly drawings), the end of the blind hole may be depicted in Fig. 8.22 On the sections of the threaded connection in the image on a plane parallel to its axis, only that part of the thread is shown in the hole that is not closed by the thread of the rod (Figure 8.23).
Distinguish threads: general purpose and special designed for use on certain types of products; fasteners, designed, as a rule, for a fixed detachable connection of the component parts of the product, and running gear - for the transmission of motion. Right-hand threads are predominantly used, LH is added to the designation of left-hand threads. In the designations of multi-start threads, the stroke is indicated, and in brackets - the pitch and its value
A blind tapped hole is made in the following order: first, a hole of diameter is drilled d1 under the thread, then a lead-in chamfer is performed Sx45º (fig. 8, and) and finally the internal thread is cut d(fig. 8, b). The bottom of the hole for the thread has a tapered shape, and the angle at the top of the taper φ depends on the sharpening of the drill. When designing, φ \u003d 120º (nominal angle of sharpening of drills) is taken. It is quite obvious that the depth of the thread must be greater than the length of the screwed-in threaded end of the fastener. There is also some distance between the end of the thread and the bottom of the hole. andcalled "undercut".
Fig. 9, the approach to dimensioning blind tapped holes becomes clear: thread depth h defined as the difference in clamping length Lthreaded part and total thickness H attracted parts (maybe
be one, or maybe several), plus a small margin of thread k, usually taken equal to 2-3 steps R carvings
h = L – H + k,
where k = (2…3) R.
Figure: 8. Sequence of execution of blind tapped holes
Figure: 9. Screw fixing assembly
Tie length L fastener is indicated in its component designation. For example: "Bolt М6х20.46 GOST 7798-70" - its tightening length L \u003d 20 mm. Total thickness of attracted parts H calculated from the general arrangement drawing (the thickness of the washer placed under the head of the fastener should also be added to this amount). Thread pitch R also indicated in the component designator of the fastener. For example: "Screw М12х1.25х40.58 GOST 11738-72" - its thread has a fine pitch R \u003d 1.25 mm. If the step is not specified, then by default it is the main (large). Lead-in chamfer leg S usually taken equal to the thread pitch R... Depth N threaded holes greater than value h by the size of the undercut and:
N \u003d h + a.
Some difference in calculating the size of the threaded hole for the stud is that the screwed-in threaded end of the stud does not depend on its tightening length and the thickness of the parts being attracted. For the studs presented in the assignment GOST 22032-76, the screwed-in "hairpin" end is equal to the thread diameter d, so
h \u003d d + k.
The resulting dimensions should be rounded to the nearest higher whole number.
The final image of a blind threaded hole with the required dimensions is shown in Fig. 10. The diameter of the hole for the thread and the angle of sharpening of the drill are not indicated in the drawing.
Figure: 10. Image of a blind threaded hole in the drawing
The tables of the handbook show the values \u200b\u200bof all calculated values \u200b\u200b(diameters of holes for threads, undercuts, thickness of washers, etc.).
Necessary note: the use of a short undercut must be justified. For example, if the part at the location of the threaded hole in it is not thick enough, and the through hole for the thread can break the tightness of the hydraulic or pneumatic system, then the designer has to "squeeze", incl. shortening the undercut.
PARTS SUBJECT TO JOINT MECHANICAL PROCESSING
In the manufacture of machines, some surfaces of parts are not processed individually, but together with the surfaces of counterparts. Drawings of such products have features. Without pretending to be a complete overview of possible options, we will consider two varieties of such details found in tasks on the topic.
Pin connections
If in an assembly unit two parts are joined along a common plane and there is a need to accurately fix their relative position, then the parts are connected by pins. The pins make it possible not only to fix the parts, but also to easily restore their previous position after disassembly for repair purposes. For example, assembling two body parts 1 and 2 (see Fig. 11) it is necessary to ensure the alignment of Ø48 and Ø40 bores for the bearing units. The flanges are clamped using bolts 3 , and once adjusted the alignment of the bores is ensured by two pins 6 ... A pin is a precision cylindrical or tapered rod; the hole for the pin is also very accurate, with a surface roughness not worse than Ra 0.8. It is obvious that a complete coincidence of the pin hole, the halves of which are located in different parts, is easiest to accomplish if the two parts are pre-set in the required position, bolted together and a hole for the pin is made in one pass of the tool in both flanges at once. This is called co-processing. But such a technique must be stipulated in the design documentation so that the technologist takes it into account when forming the technological process of manufacturing the unit. The indication of joint machining of pin holes is performed in the design documentation in the following way.
On the ASSEMBLY drawing, the dimensions of the holes for the pin, the dimensions of their location are specified and the roughness of the hole processing is indicated. The named dimensions are marked with "*", and in the technical requirements of the drawing an entry is made: "All dimensions for reference, except those indicated by *". This means that the dimensions according to which the holes are made on the assembled unit are executive and they are subject to control. And in the drawings of the DETAILS, the holes for the pin are not shown (and therefore not performed).
Connected bores
In some machines, bore holes for bearings are located simultaneously in two parts, with the plane of their joint positioned along the bearing axis (most often found in gearbox designs - the case-cover connection). Bearing bores - precise surfaces with a roughness not worse than Ra 2.5, they are made by joint processing, and in the drawings this is specified as follows (see Fig. 12 and 13).
In the drawings of EACH of the two parts, the numerical values \u200b\u200bof the dimensions of the surfaces processed together are indicated in square brackets. In the technical requirements of the drawing, an entry is made: “Processing in size in square brackets should be done in conjunction with children. No.… ". The number means the designation of the drawing of the counterpart.
Figure: 11. Specifying the pin hole in the drawing
Figure: 12. Boring with connector. Assembly drawing
Figure: 13. Defining a split boring in part drawings
CONCLUSION
After reading the process of creating a drawing of a part described above, a doubt may arise: do professional designers work out every little detail so carefully? I dare to assure - exactly so! It's just that when making drawings of simple and typical parts, all this is done in the designer's head instantly, but in complex products - only in this way, step by step.
BIBLIOGRAPHIC LIST
1. GOST 2.102-68 ESKD... Types and completeness of design documents. M.: IPK Publishing house of standards, 2004.
2. GOST 2.103-68 ESKD... Development stages. M.: IPK Publishing house of standards, 2004.
3. GOST 2.109-73 ESKD... Basic requirements for drawings. M.: IPK Publishing house of standards, 2004.
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5. GOST 2.118-73 ESKD... Technical Proposal. M.: IPK Publishing house of standards, 2004.
6. GOST 2.119-73 ESKD... Preliminary design. M.: IPK Publishing house of standards, 2004.
7. GOST 2.120-73 ESKD... Technical project. M.: IPK Publishing house of standards, 2004.
8. GOST 2.305-68 ESKD... Images - views, sections, sections. M.: IPK Publishing house of standards, 2004.
9. Levitsky VS Machine-building drawing: textbook. for universities / V.S. Levitsky. M.: Higher. shk., 1994.
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11. Reference manual for drawing / V. I. Bogdanov. [and etc.]. M.:
Mechanical engineering, 1989.
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/ A. M. Kauzov. Ekaterinburg: USTU-UPI, 2009.
ANNEXES
Appendix 1
Assignment on topic 3106 and an example of its execution
Task number 26
An example of the execution of task number 26
Appendix 2
Typical mistakes of students when performing detailing
