Rectangular single-thread thread main dimensions GOST. Image and thread designation. Symbolic image of the thread assembly
The rectangular thread (Fig. 85) is non-standard, which means it does not have a symbol. Therefore, the drawing must indicate all the dimensions necessary for its manufacture.
Rice. 85 Rectangular thread
In a threaded connection, one part has an external thread, and the other has an internal thread. External thread in the connection it is a covered surface, and the part that has it is called a “bolt” (screw, stud). Internal thread is a covering surface and is called a "nut" (nest, etc.).
In the drawings, the thread is shown conditionally: the tops of the turns are shown with a solid main line, and the troughs of the turns are shown with a solid thin line (Fig. 86).
Rice. 86 Thread representation in drawings: a- outdoor; b- internal
On sections of a threaded connection in the image on a plane parallel to its axis, only that part of the thread that is not covered by the thread of the rod is shown in the hole (Fig. 87).
Rice. 87 Illustration of the thread in the connection
The correct application of the thread designation in the drawings is given in table. 2.
Fasteners
Fasteners include bolts, screws, studs, nuts, washers, cotter pins.
The shape, dimensions and other characteristics of fasteners (such as material, strength class, coating nature, etc.) are standardized, but without special knowledge they cannot be reasonably assigned. Therefore, in the course "Engineering Graphics" in the symbol of fasteners, some parameters are not indicated. Most fastener threaded products are made with metric threads, coarse or fine pitch. Drawings of fasteners are made according to the actual dimensions, which are established by the relevant standard.
bolts
A bolt is a cylindrical rod, at one end of which there is a head (hexagonal, square, round or special), and at the other end there is a thread for screwing a nut.
table 2
| thread type | Conventional thread designation | Thread designation on images in a plane parallel to the thread axis | Thread designation on images in a plane perpendicular to the thread axis | ||
| on the rod | in the hole | on the rod | in the hole | ||
| Thread metric | M |  |  |  |  |
| Trapezoidal thread - long single thread | Tr |  |  |  |  |
| Thread resistant | S |  |  |  |  |
| Cylindrical pipe thread | G |  |  |  |  |
| Conical pipe thread: external internal | R Rc |  |  |  |  |
Rice. 88 Bolts
An example of a complete symbol for a high-precision bolt with a thread diameter d= 16 mm long l= 60 mm, strength class 5.8, version 2, with fine pitch R=1.5 mm, with tolerance field 69, uncoated:
Bolt 2M16´1,5.6g´60.58 GOST 7798-70.
Bolt designation on training drawings:
Bolt 2M16´1.5´60 GOST 7798-70.
hairpins
hairpin called a cylindrical rod, at both ends of which there is a metric thread (Fig. 89). Studs are used to connect parts when there is no place to accommodate the bolt head or nut, and also when one of the parts to be joined has a significant thickness, which makes it uneconomical to install a long bolt.
Threaded stud end l 1, screwed into the part, is called landing. Its length depends on the strength and ductility of the material from which the part is made.
For durable and ductile materials (steel, bronze, brass, etc.)
l 1 = d(GOST 22032-76, GOST 22033-76).
For gray and ductile iron:
l 1 = 1,25d(GOST 22034-76, GOST 22035-76),
l 1 = 1,6d(GOST 22036-76, GOST 22037-76).
For light alloy parts:
l 1 = 2d(GOST 22038-76, GOST 22039-76),
l 1 = 2,5d(GOST 22040-76, GOST 22041-76).
To the other threaded end of the stud l 0 the nut is screwed on. hairpin length l conditionally consider the length of its rod without the length of the landing end l 1 (see fig. 89).
An example of a symbol for a stud with a thread diameter d= 20 mm, in increments P= 1.5 mm, with tolerance field 6 g, length l= 100 mm, with threaded end screw-in length l 1 =d, normal accuracy, strength class 5.8, uncoated:
Hairpin M20´1.5-6g´100.58 GOST 22032-76.
The designation of the same stud on the training drawings:
Hairpin M20´1.5´100 GOST 22032-76.
screws
A screw is a cylindrical rod, at one end of which there is a head, and at the other end a metric thread is cut. Screws most often have a slot in the head for a screwdriver, but there are screws with hex and square heads for a wrench.
Depending on the purpose, the screws are divided into fixing, adjusting, adjusting, etc. Set screws are used to adjust the gaps and fix parts during assembly. The most widespread in mechanical engineering are fastening screws for metal. These screws, depending on the working conditions, are made with a cylindrical, GOST 1491-80 (Fig. 90, a), semicircular, GOST 17473-80 (Fig. 90, b), semi-hidden, GOST 17474-80 (Fig. 90, in) and secret, GOST 17475-80 (Fig. 90, G) heads. The defining dimensions for all screws are the thread diameter d and length l. Per length l most machine screws take the length of their shank (without head).
For countersunk screws, the value l includes stem length and head height (see fig. 90, G).
nuts
A nut is a part that has a threaded hole for screwing onto a bolt or stud with the same thread. Standard nuts can be hexagonal (Fig. 91, a), slotted and crowned (Fig. 91, b), round (Fig. 91, in), lamb (Fig. 91, G) and etc.
 |
 |
 |  |
| a | b | in | G |
| Rice. 91 Nuts |
Hex nuts are classified according to height as normal, low, high and extra high.
Nuts are manufactured with normal and increased accuracy. Some hex nuts are made in two versions (Fig. 92): version 1 - with two chamfers; execution 2 - with one chamfer.
An example of a symbol for a hexagonal nut (normal accuracy), version 1 (with two chamfers), thread diameter d= 30 mm, fine pitch P = 2 mm , with tolerance field 7 H, strength class 5, uncoated:
Nut M30´2.5 GOST 5915-70.
The same in the training drawings:
Rice. 92 Nuts
washers
A washer is a stamped or turned ring that is placed under the nuts or heads of bolts and screws.
Round washers (GOST 11371-78) have 2 versions (Fig. 93): version 1 - without chamfer; execution 2 - with a chamfer.
An example of the conventional designation of a normal washer, version 2 for a fastener with a thread diameter of 30 mm, a specified thickness, from a material of group 01, with a coating of 01, 9 microns thick:
Washer 2.30.01.019 GOST 11371-78.
The same in the training drawings:
Washer 2.30 GOST 11371-78.
Rice. 93 Washer designs
Thread profiles
To category:
Threading
Thread profiles
The thread profile depends on the shape of the cutting part of the tool with which the thread is cut. Most often, a cylindrical triangular thread (sawtooth) is used, it is usually called a fastener; such a thread is cut on fasteners, for example, on studs, bolts and nuts.
In addition to cylindrical triangular threads, there are conical triangular threads, which make it possible to obtain a tight connection, such threads are found on conical plugs, and fittings are sometimes found in oilers.
Rectangular threads have a rectangular profile (square). It is not standardized, difficult to manufacture, fragile and rarely used.
Trapezoidal tape thread has a cross section in the form of a trapezoid with a profile angle of 30°. It has a low coefficient of friction, and therefore this thread is used to transmit movements or large forces: in metal-cutting machines (lead screws), jacks, presses, etc. The coils of this thread have a large cross section at the base, which ensures its high strength and convenience when cutting. The main elements of the trapezoidal thread are standardized.
The thrust thread has a profile in the form of an unequal trapezoid with a working angle at the top of 30°. The bases of the turns are rounded, which provides a strong profile in a dangerous section. Therefore, this thread is used in cases where the screw must transmit a large one-sided force (in screw presses, jacks, etc.).
A round thread has a profile formed by two arcs conjugated with small straight sections and an angle of 30; rarely used in engineering. It is used in joints subjected to heavy wear, in a polluted environment (fittings of fire pipelines, wagon ties, hooks of hoisting machines, etc.). This thread is not standardized.
According to the number of threads, threads are divided into single-thread (single-thread) and multi-thread (multi-thread).
The thread stroke is the axial movement of the screw for one of its revolutions. For example, when screwing in, the nut will move in one revolution by an amount equal to the lead of the thread. For single start threads, the pitch is equal to the lead. For multi-start screws, the thread lead is obtained by multiplying the pitch (distance between adjacent turns) by the number of starts. The number of entries can be determined by looking at the end of the screw (nut), which usually clearly shows how many threads originate from the end of the three-start, eight-start (Fig. 259, a, b).
Rice. 1. Profiles and thread elements: a - cylindrical triangular, b - rectangular, c - trapezoidal, d - thrust, d - round
Rice. 2. Threads with a different number of leads (moves): a - three-start, b - eight-start
For a single-start (single-start) thread, only one end of the coil is visible at the end of the screw or nut, and for multi-start (multi-pass) threads, two, three or more turns.
Single start threads have small helix angles and greater friction (low efficiency). They are used where a reliable connection is required - for fastening threads.
In multi-start threads, compared to single-start threads, the helix angle of helix is much larger (steeper rise). Such threads are used in cases where it is necessary to move quickly along the thread with the least friction, while in one revolution of the screw (or nut), the nut (or screw) will move by the amount of the helix of the thread. Multi-start threads are used in mechanisms that serve to transmit movement.
Main thread types and their designation
In mechanical engineering, as a rule, three thread systems are used: metric, inch and pipe.
The metric thread has a triangular profile with flat-cut tops (Fig. 3, a) and is characterized by the following main elements: the profile angle is 60 °, the diameters and the pitch are expressed in the metric system of measures - in millimeters.
Metric threads are divided into coarse pitch threads (for outer diameters 1-68 mm) and fine pitch threads (for diameters 1-600 mm); steps for large threads - 0.25 - 6 mm, for small threads - 0.2 - 6 mm.
Metric threads with a large pitch denote: M20 (the number is the outer diameter of the thread); with small steps: M20x 1.5 (the first number is the outer diameter, and the second is the step).
Metric threads are used mainly as fasteners: with a large pitch - with significant loads and for fasteners (bolts, nuts, screws), with small pitches - with small loads and fine adjustments.
An inch thread (Fig. 3, b, c, d) has a triangular overcut profile with an angle of 55 ° (Whitworth thread) or 60 ° (Sellers thread). All dimensions of this thread are given in inches (1” = 25.4 mm). The pitch is expressed as the number of threads (turns) on the length of one inch.
Inch threads are standardized with diameters from 3/16 to 4 "and the number of threads per 1" -24 - 3. Its outer diameter is indicated in inches. It differs from the metric by a large step.
In the USSR, when designing new structures, the use of inch threads is not allowed. It is used in the manufacture of spare parts for machinery and equipment obtained from countries where inch threads are used.
The cylindrical pipe thread is standardized, it is a small inch thread. Unlike an inch thread, it mates without gaps (to increase the tightness of the connection) and has rounded tops.
Rice. 3. Thread systems: a - metric, 6 - inch, c - pipe, d - part with inch thread
For the nominal diameter of the pipe thread, the inner diameter of the pipe is used (the diameter of the hole, or, as they say, “pipe diameter in the clear”), i.e. the outer diameter of the pipe thread will be larger than the nominal diameter by twice the thickness of the pipe walls.
Pipe cylindrical thread is used for outer diameters 1/8 - 6” with the number of threads per 1” from 28 to 11. Profile angle 55°.
Cylindrical pipe threads are used on pipes for their connection, as well as on fittings for pipelines and other thin-walled parts.
Pipe cylindrical thread is designated: Pipe 3/4 "(numbers - nominal thread diameter in inches).
Pipe threads are standardized from 2/8 to 6” in diameter with 28-11 threads per 1”.
10.1.4. Image and designation of threads in the drawings
The image and designation of the thread in the drawings is standardized. In accordance with GOST 2.311-68, the external thread is depicted with solid main lines along the diameter D and solid thin lines along the diameter D 1 . On images obtained by projecting onto a plane perpendicular to the axis of the thread, a solid thin line is not brought to 1/4 . Chamfer lines are not shown (figure 10.6).
A solid thin line when depicting a thread is drawn at a distance of at least 0.8 mm from the main line and not more than the pitch. A solid thin line of the image of the thread on the bar must intersect the line of the chamfer boundary.
The internal thread is shown by solid main lines - along the inner diameter d and solid thin - in diameter d 1 . The thread boundary is applied at the end of the full profile, before the start of the run. It is carried out to the line of the outer diameter and is depicted as a solid thick line if the thread is visible, and dashed if it is invisible. Hatching in sections and sections is carried out to a solid thick line.
For all types of threads, excluding conical and pipe cylindrical, the designation refers to the outer diameter and is put down above the dimension line, on its continuation and on the shelf - leader (Figure 10.6).
Figure 10.6 - Symbol for internal and external threads
The designation of a conical thread and a cylindrical pipe thread is related to the thread contour and is applied only on the shelf of the leader line (Figure 10.7).
Figure 10.7 - Designation of conical and cylindrical pipe threads
Table 1 - Thread types and designation
|
Profile |
Designation |
|
|
Metric GOST 9150-81 - for profile GOST 24705-81 - for diameters GOST 8724-81 - for diameters and pitches |
Equilateral triangle. The tops of the protrusions and depressions of the profile are cut along a straight line or an arc of a circle, which facilitates the manufacture of threads, reduces stress concentration and protects the thread from damage during operation. |
M20-6g - metric thread with a diameter of 20 mm, coarse pitch 2.5 mm, tolerance field 6g, right; M20×2- metric thread with a diameter of 20 mm, fine pitch 2 mm, right; M20×2LH - metric thread with a diameter of 20 mm, fine pitch 2 mm, left hand. The thread has one large and several small pitches for each nominal diameter. A large step in the thread designation is not indicated, but a small one is required. LH is added to the designation of the left thread. |
|
Metric thread is the most widely used in engineering. This thread is used on bolts, studs, screws, nuts, etc. Mostly right hand thread is used. |
||
|
Inch GOST 6111-52 |
An isosceles triangle with a 55° apex angle (for a tapered thread, a profile angle of 60). The peaks and troughs are flat cut. |
1" - inch cylindrical thread with an outer diameter of 1 inch; K 1 3 / 4 "GOST 6111-52- thread inch conical. |
|
Trubnaya cylindrical GOST 6357-81 Trubnaya conical GOST 6211-81 |
An isosceles triangle with an apex angle of 55°. Tops and troughs are rounded, which makes the thread more airtight than metric threads. |
G1- A - cylindrical pipe thread with a diameter of 1 inch, accuracy class A; R1 - external conical pipe thread; Rc1 - pipe thread conical internal. Size 1 "=25.4 mm corresponds to the inner diameter of the pipe (nominal bore). The outside diameter of the pipe thread will be 1"=25.4mm+2 pipe thicknesses=33.25mm. |
|
Cylindrical pipe threads are used on water and gas pipes, on parts for their connection - fittings (couplings, elbows, tees, etc.), pipe fittings(gate valves, valves), etc. Tapered pipe threads are used in pipe joints at high pressures and temperatures. |
||
|
Trapezoidal GOST 9484-81 - for profile, GOST 24738-81 - for diameters and pitches |
|
Tr40×6-8e- trapezoidal thread, single-start, with a nominal diameter of 40 mm, a pitch of 6 mm, accuracy class 8e; Tr48×9(RZ)LH- trapezoidal thread, three-start, with a nominal diameter of 49 mm, a stroke of 9 mm, a pitch of 3 mm, left |
|
It is used on screws that transmit reciprocating motion. |
||
|
stubborn GOST 10177-82 for the profile and main dimensions |
An unequal trapezoid with angles of 3° and 30° at the sides |
S80×5- thrust thread, with a nominal diameter of 80 mm, single-start, with a pitch of 5 mm; S80×20(P5)LH- thread persistent, four-start, with a nominal diameter of 80 mm, a stroke of 20 mm, a pitch of 5 mm, left. |
|
It is used on screws subject to unilaterally directed forces, for example, in jacks. |
||
|
Rectangular |
The profile is not standardized, the drawing contains all the data necessary for its manufacture. |
|
|
It is used in connections where there should be no self-unscrewing under the action of an applied load. |
||
|
The profile is standard, but the dimensions of the diameter or pitch are different from those accepted according to the standard. |
Cn is added to the designation of any thread with a standard profile: |
|
Profile thread is established by GOST 9150-81 and is a triangle with an angle at the top of 60 o.
This is the main type of fastening thread. Designed for connecting parts directly to each other or using standard products with metric threads - bolts, screws, studs, nuts.
Its main elements and parameters are set in millimeters (GOST 24705-81).
According to GOST 8724-81, metric threads are made with large and fine pitch on surfaces with a diameter of 1 to 68 mm, over 68 mm the thread has only a fine pitch, and the fine thread pitch can be different for the same diameter, and the large thread has only one meaning. The coarse pitch in the thread symbol is not indicated. So, for a thread with a diameter of 10 mm, a coarse thread pitch is 1.5 mm, a fine- 1.25; one; 0.75; 0.5 mm.
M18-6g metric external thread, nominal diameter 18 mm, coarse pitch, thread tolerance 6g;
M18x0.5-6g the same, small step R=0,5;
M18LH-6g the same, but left;
M18-6H metric internal thread, nominal diameter 18 mm, coarse pitch, thread tolerance 6H.
Currently, there is no standard that regulates the main dimensions of an inch thread. The previously existing OST NKTP 1260 was canceled, and the use of inch threads in new developments is not allowed.
Triangular profile thread with an angle at the top of 55 o.
Thread tubular cylindrical
In accordance with GOST 6311-81, cylindrical pipe thread has an inch thread profile, i.e. an isosceles triangle with an apex angle of 55°.
Threads are standardized for diameters from 1/16" to 6" in number of pitches z from 28 to 11. The nominal thread size is conditionally related to the inner diameter of the pipe (to the nominal bore). So, a thread with a nominal diameter of 1 mm has a nominal diameter of 25 mm, and an outer diameter of 33.249 mm.
Symbol examples:
G1 1/2 -A cylindrical pipe thread, 1 1/2 conditional pass in inches, accuracy class A;
G1 1 / 2 LH-B-40 the same, but left hand, accuracy class B, make-up length 40 mm.
 Thread resistant |
Thread with a profile in the form of an isosceles trapezoid with an angle of 30 o. It is used to transmit reciprocating motion or rotation in heavily loaded movable threaded connections. Often used in the manufacture of lead screws, according to GOST 24738-81, it is performed on surfaces with a diameter of 8 to 640 mm.
Trapezoidal thread can be single pass(GOST 24738-81, GOST 24737-81) and multiple(GOST 24739-81). GOST 9484-81 establishes the profile of a trapezoidal thread.
Tr40 X 6 -trapezoidal single-start thread with an outer diameter of 40 mm, a pitch of 6 mm.
R thread with a profile in the form of an unequal trapezoid with an angle of the working side of 3 ° and non-working-30 o. Thrust thread, like trapezoidal, may be single pass and multiple. It is carried out on surfaces with a diameter of 10 to 640 mm (GOST 10177-82). It is used to transfer large forces acting in one direction: in jacks, presses, etc.
Symbol example:
S80x 10 -persistent single-start thread with an outer diameter of 80 mm, a pitch of 10 mm;
S80x 20(P10)-persistent multi-start thread with an outer diameter of 80 mm, a stroke of 20 mm, a pitch of 10 mm.
This r The thread has a rectangular (or square) non-standard profile, so all its dimensions are indicated on the drawing. It is used to transfer the movement of heavily loaded movable threaded joints. Usually performed on load and lead screws.
A thread with a round profile (GOST 6242-83) has a relatively long service life and increased resistance under significant loads. It is used in the manufacture of frequently screwed connections (spindles, valves, etc.) operating in a polluted environment, as well as thin-walled parts with knurled or stamped threads (electric lamp base, etc.).
Symbol example:
Rd16-round thread with an outer diameter of 16 mm.
If a round thread is used in connections of sanitary fittings, then its designation will be as follows: Kr12x2.54 (GOST 13536-68).
Consider general purpose standard threads.
Thread metric is the main mounting thread. This is a single-start thread, mostly right-handed, with a large or small pitch. Profile metric thread serves as an equilateral triangle. The protrusions and notches of the thread are blunted (Fig. 204) (GOST 9150-81).
Rice. 204 Metric thread
Cylindrical pipe thread has a profile in the form of an isosceles triangle with an angle at the top of 55 ° (Fig. 205), tops and troughs are rounded. This thread is used in pipelines and pipe connections (GOST 6351-81).
Rice. 205 Pipe thread cylindrical
Trapezoidal thread serves to convey movement and effort. The profile of the trapezoidal thread is an isosceles trapezoid with an angle between the sides of 30 ° (Fig. 206). For each diameter, the thread can be single-start and multi-start, right-hand and left-hand (GOST 9484-81).
Rice. 206 Trapezoidal thread
Thread resistant has a profile of an unequal trapezoid (Fig. 207). The profile cavities are rounded, there are three different pitches for each diameter. Serves for transmission of movement with large axial loads (GOST. 10177-82).
Rice. 207 Thrust thread
Round thread for socles and cartridges, for safety glasses and lamps, for sanitary fittings (GOST 13536-68) has a profile obtained by pairing two arcs of the same radius (Fig. 208) (GOST 13536-68).
Rice. 208 Round thread
Thread conical inch with a profile angle of 60° (GOST 6111-52) is used for hermetic connections in pipelines of machines and machine tools; cut on a conical surface with a taper of 1: 16 (Fig. 209).
Rice. 209 Tapered inch
Conical pipe thread has a profile similar to that of a cylindrical pipe thread; used in valves and gas cylinders. It is possible to connect pipes with a conical thread (taper 1: 16) with products having a cylindrical pipe thread (GOST 6211-81).
Special Threads- these are threads with a standard profile, but different from the standard dimensions of the diameter or thread pitch, and threads with a non-standard profile.
Non-standard threads - square and rectangular(Fig. 210) - are made according to individual drawings, on which all thread parameters are specified.
Rice. 210 Non-standard threads
Thread image on the drawing is performed in accordance with GOST 2.311-68. On the rod, the thread is depicted with solid main lines along the outer diameter and solid thin lines along the inner diameter. On fig. 211, a shows the thread on the cylinder, and in fig. 211, b - on a cone.
Rice. 211 Drawing thread image
In the hole, the thread is depicted by solid main lines along the inner diameter and solid thin lines along the outer diameter. On fig. 212, and the thread is shown in a cylindrical hole, and in fig. 212, b - in the conical.
Rice. 212 Illustration of the thread in the hole
On images obtained by projection threaded surface on a plane perpendicular to its axis, a solid thin line is drawn by an arc of 3/4 of the circumference, open anywhere, but not ending on the axes. A solid thin line when depicting a thread is drawn at a distance of at least 0.8 mm from the main line and not more than the thread pitch. The visible thread boundary is drawn by a solid main line at the end of the full thread profile to the thread outer diameter line. The thread run is depicted as a solid thin line, as shown in Fig. 213.
Rice. 213 Thread run
Chamfers on a threaded rod or in a threaded hole that do not have a special design purpose are not shown in projection onto a plane perpendicular to the axis of the rod or hole. A solid thin line of the thread image must cross the chamfer boundary line (Fig. 213, 214). Hatching in cuts and sections is brought to a solid main line.
Rice. 214 The thread image line must intersect the chamfer boundary line
A thread with a non-standard profile is depicted as shown in Fig. 215, with all dimensions and additional data with the addition of the word "thread".
Rice. 215 Thread image with non-standard profile
In threaded connections, the thread is conditionally drawn on the rod, and in the hole - only that part of the thread that is not closed by the rod (Fig. 216).
Rice. 216 Threaded connections
The thread designation includes: thread type, size, thread pitch and lead, tolerance field, accuracy class, thread direction, standard number.
The type of thread is conditionally indicated:
M- metric thread (GOST 9150-81);
G- cylindrical pipe thread (GOST 6357-81);
T g- trapezoidal thread (GOST 9484-81);
S- thrust thread (GOST 10177-82);
Rd- round thread (GOST 13536-68);
R- pipe conical outer (GOST 6211-81);
Rr- internal conical (GOST 6211-81);
Rp- internal cylindrical (GOST 6211-81);
To- conical inch thread (GOST 6111-52).
Size of Tapered Threads and Parallel Pipe Threads conventionally indicated in inches (1 "= 25.4 mm), for all other threads, the outer diameter of the thread is affixed in millimeters.
thread pitch do not indicate for metric threads with a large pitch and for inch threads, in other cases it is indicated. For multi-start threads, the thread designation includes the thread lead, and the pitch is affixed in brackets.
thread direction indicated for left-hand thread (LH) only.
The tolerance field and the accuracy class of the thread on the training drawings can be omitted.
