Threaded connections are called connections of parts using threads - alternating protrusions and depressions on the surface of bodies of revolution located along a helix. There are conical and cylindrical threaded connections. Cylindrical, in turn, are divided into connections with fastening and special threads.
Fastening threads include large and small metric threads according to GOST 9150-81, as well as threads with spiral inserts; to special ones - pipe, rectangular, thrust, round, trapezoidal, etc.
A part with an internal thread is called nut, from the outside - bolt(screw, pin).
The thread profile is the contour of a thread section in a plane passing through the axis of the threaded part. GOST 9150-81 and GOST 8724-81 establish a single nominal profile for cylindrical metric threads with a diameter of up to 600 mm, including threads with a diameter of less than 1 mm. The nominal thread profile and its elements are shown in (Fig. 1, a). The cavity of the external thread (Fig. 1, b) can be flat-cut or rounded: R max =0.144P, R min \u003d 0.108P,
Where R- cavity radius;
R- thread pitch.
Threads are defined by the following main parameters:
- outer, middle and inner diameters;
- step;
- profile angle;
- angle of inclination of the sides of the profile.
Outer thread diameter d (see Fig. 1, a) - the diameter of the cylinder described with respect to the tops of the external thread (or the troughs of the internal thread).
Inner diameter d1 - the diameter of the cylinder inscribed in the tops of the internal thread (or the trough of the external thread).
Rated values d And d1 for external and internal threads are the same.
Average diameter d2 - the diameter of an imaginary cylinder, the surface of which intersects the threads in such a way that the width of the threads and the width of the troughs are equal.
thread pitch R - the distance between the parallel sides of two adjacent coils, measured along the axis.
GOST 8724-81 sets diameters in the range of 0.25 ... 600 mm and steps of 0.075 ... 6 mm. Metric threads can have a coarse pitch (with diameters of 0.25 ... 68 mm) and a fine pitch (with diameters of 1 ... 600 mm).
Profile angle α - the angle between the sides of the profile, measured in the axial plane. Angle of inclination of the sides of the profile β - the angle between the profile side and the perpendicular to the thread axis. For threads with a symmetrical profile β=0.5α. For threads with an asymmetric profile, such as thrust or conical threads, the angle of inclination of each side is determined independently.
Height of the original triangle H - the height of the acute-angled profile obtained by continuing the lateral sides of the profile until they intersect. Working profile height H1- the height of the flat-cut theoretical profile, equal to the half-difference of the outer and inner diameters. For metric threads H=0.866025R, H 1 \u003d 0.54126 R.
In reality, the contact height is less, since the tolerance system provides for certain clearances, for example, along the inner diameters of the nut and bolt threads.
Working coil height H1- the highest contact height; the smallest contact height is indicated H 1 min. For flat profile threads H1 And H 1 min determine the largest and smallest overlap of threads and nuts.
Helix angle (helix) 
For multi-start threads, the numerator of this formula should be substituted for R work n 0 P,
Where n 0- number of visits.
Make-up length l(nut height H) - the length (height) of the contact surfaces of the bolt and nut, measured along
Mounting thread is used in the connecting parts of machines, mechanisms and devices, i.e. bolts, screws, studs, nuts. Running and load threads are used in the lifting screws of screw presses, jacks, machine tools to convert rotational motion into translational.
Special Thread it is used in tools for threading in holes - taps and on the rod - dies, as well as in tools for making holes - drills and processing planes, grooves and grooves - cutters.
At present the main industrial way threading on hardware products (bolts, studs, screws) is knurling using high-performance thread rolling machines. The process of thread rolling is carried out as a result of plastic deformation of the rod, without chip removal. By rolling the part between two flat dies or cylindrical rollers with a threaded profile, the thread of the corresponding profile is squeezed out due to the redistribution of the metal.
A thread formed on a cylindrical surface is called cylindrical, and a thread formed on a conical surface is called conical.
An external thread formed on a cylindrical or conical surface of a rod is a male surface (bolt, screw, etc.). The internal thread formed on the cylindrical or conical surface of the hole is the female surface (nut).
According to the number of starts, the threads are divided into single-start and multi-start (two-, three-start, etc.)
The right thread is formed by a contour rotating clockwise and moving along the axis from the observer, and the left thread is formed by a contour rotating counterclockwise.
The thread can be standard and non-standard. For a standard thread, all the main parameters are determined by GOST 11708-82.
The thread is characterized by three diameters fig. 2: outer, inner and middle. In this case, the diameters of the external thread are designated d, d 1, d 2, and the internal - D, D 1, D 2.
The outer diameter of the thread d (D) is the diameter of an imaginary straight circular cylinder described around the tops of the external or troughs of the internal thread. This diameter is defining, calculated and is included in symbol threads
The inner diameter of the thread d 1 (D 1) is the diameter of an imaginary straight circular cylinder inscribed in the troughs of the external or tops of the internal thread.
The average thread diameter d 2 (D 2) is the diameter of an imaginary straight circular cylinder, the generatrix of which intersect the thread profile in such a way that its segments formed at the intersection with the groove are equal to half of its nominal pitch.
Thread profile - the profile of the protrusion and groove and thread in the plane of its axial section.
Thread profile angle - the angle between adjacent thread flanks in the plane of its axial section.
The height of the initial thread triangle H is the distance between the vertex and the base of the initial thread triangle in the direction perpendicular to its axis.
The working height of the profile H 1 is the length of the section of mutual overlap of the profiles of the mating external and internal threads at a perpendicular to the axis of the thread.
Profile height H 3 - the distance between the top and bottom of the thread in the plane of the axial section in the direction perpendicular to the axis of the thread.
The thread pitch P is the distance along a line parallel to the axis of the thread, between the midpoints of the nearest lateral sides of the same name of its profile, lying in the same axial plane.
Thread stroke P h - distance along a line parallel to the axis of the thread, between any original middle point on the side of the thread and the midpoint obtained by moving the origin along the helix through an angle of 360º.
The cutting part of the tool (on taps and dies) for cutting threads has two sections: the intake section - with a thread limited by a conical surface, and the cylindrical section - forming a thread of the required profile, pitch and size.
Image of threads in the drawing
Drawing a thread in the form of a helical surface is laborious work, therefore, in the drawings, regardless of the profile and purpose, it is conventionally depicted in accordance with GOST 2.311 - 68 *.
The external thread is depicted by solid thick main lines along the outer diameter d, and solid thin lines along the inner diameter d 1. on a plane parallel to the axis of the thread, a solid thin line is drawn along the entire length of its full profile, including the chamfer (Fig. 3). The line defining the thread boundary is indicated at the end of its full profile with a solid thick main line if the thread is visible, or dashed if it is invisible.
The internal thread in the sections is shown by solid thick main lines along the inner diameter D 1 and solid thin lines along the outer diameter D (Fig. 4). On a plane perpendicular to the axis of the thread, a solid thin line is drawn in the form of an arc equal to ¾ of a circle. Moreover, the beginning and end of this arc should not coincide with the center lines.
When depicting a thread (both external and internal) on a plane perpendicular to the axis of the rod or hole, chamfers that do not have a special design purpose are not shown.
Hatching in sections and sections of threaded products is applied to a solid main line, i.e. to the line of the outer diameter of the thread on the rod and the line of the inner diameter of the thread in the hole.
In threaded connections, the thread is conditionally drawn on the rod, and only that part of it that is not covered by the thread of the rod is shown in the hole (Fig. 5).
A more conventional designation of the conical thread on the rod and in the hole, respectively, is shown in Fig. 6
Thread designation
| name, standard | View | Designation | Example |
| Metric, GOST 8724-81 * | Coarse pitch Fine pitch Multi-start left hand | M, d (mm) M, d, P (mm) M, d, P h (mm) LH | M20 M20×1.5 M20×3(P1) M20LH, M20×1.5LH, M20×3(P1)LH |
| Inch, OST NKTP 1260 | outer inner | - - | ½’ ½’’ |
| Pipe cylindrical, GOST 6357-81 | Class A (advanced) Class B (normal) Left | G, D y (inch), Class A G, D y (inch), Class B LH | G 1½ - A G 1½ - B G 1½ LH - A G 1½ LH - B |
| Pipe conical, GOST 6211-81 | Outer Inner Inner Cylindrical Left | R, D y (in) R c , D y (in) R p , D y (in) LH | R 1½ R c 1½ - B R p 1½ R 1½LH R c 1½ LH |
| Conical inch, GOST 6111-52 * | Outdoor Internal | K, D y (inch) K, D y (inch) | To 1½'' To 1½'' |
| Metric conical, GOST 25229-82 | Conical Internal Cylindrical Left | MK, d, P (mm) M, d, P (mm) LH GOST … | MK 20×1.5 M20×1.5 GOST 25229-82 MK20×1.5 LH GOST 25229-82 |
| Trapezoidal, GOST 24738-81 | Single start Left | Tr, d, P (mm) LH | Tr40×6 Nr40×6 LH |
| Trapezoidal, GOST 24739-81 * | Multi-start Left | Tr, d, P h , P (mm) LH | Tr20×8(P4) Tr20×8(P4) LH |
| Thrust, GOST 10177-82 | Single start Multi start Left hand | S, d, P (mm) S, d, P h , P (mm) LH | S80×10 S80×20(P10) S80×20 LH; S80×20(P10)LH |
| Round, GOST 13536-68 | Right | Kp, d, P (mm) GOST… | Kp12×2.54 GOST 13536-68 |
For example, the inscription M20 × 1.5 - 6g (fig.) means that the thread is metric, the outer diameter of the thread is 12 mm, the thread with a fine pitch of 1.5 mm and a tolerance field of 6g (6 is the accuracy class, g is the main deviation of the bolt thread ).
Stud connections
A stud connection consists of a stud, nut, washer and parts to be connected and is used when one of these parts has a significant thickness, i.e. when it is impractical to drill a through hole for a long bolt. It is performed as follows (Fig. 7). In part 1, a socket with a diameter of D 1 is drilled and a thread is cut. Thread dimensions of the screw-in end of the stud.
In the drawing of the stud connection (Fig. 8), the dividing line of the parts to be connected must coincide with the thread boundary of the screwed end of the stud. It is technologically impossible to cut the thread to the end of the nest, but it is allowed to depict it on the assembly drawings at its entire depth. Hatching in the section is brought to the main thread line on the stud and in the socket. Three dimensions are indicated on the drawing of the stud connection: the thread diameter, the length of the stud and the diameter of the hole in the attached part. On a simplified image of a stud connection (Fig. 9), the thread is conventionally shown along the entire length of the stud. at the same time, on the fasteners, the end of the hole, including the margin and undercut of the thread, as well as the gap between the hole of the attached part and the stud, are not depicted. the dimensions of the fasteners are determined depending on the diameter of the bolt thread d.
If the nominal thread diameter is equal to or less than 2 mm, a symbolic representation of a stud connection is allowed (Fig. 10).
Rice. 8 Fig. 9 Fig. 10
Bolted connections
On the drawing of a bolted connection (Fig. 11), at least two images are made: on the projection plane parallel to the bolt axis and on the projection plane perpendicular to its axis (from the side of the nut). When depicting a bolted connection in a section, standard parts (bolt, nut, washer) are shown uncut. It is customary to depict the head of a bolt and nut in the main view with three faces. Hatching of adjacent parts is performed at an angle of 45 0 to the horizontal lines of the drawing in different directions, while for each part in all images the same direction and frequency of hatching are maintained.
Three dimensions are indicated on the drawing of a bolted connection: thread diameter, bolt length and diameter of the bolt hole in the parts to be joined.
 |
Rice. 11 Fig. 12
With a simplified image of a bolted connection, the dimensions of the elements of the fasteners are determined by conditional ratios depending on the diameter of the bolt thread d (Fig. 12). depict.
The most common elements of parts are shown in fig. 7.1.
Rice. 7.1. Various elements of a detail
Reference data for standard elements is given in this chapter of the manual.
§ 7.1. Carving and its elements
Many details of modern machines, mechanisms, devices are threaded (Chapter 4). The thread is widely used for connecting parts. This is due to the ease of assembly of products.
The thread, depending on the material (metal, plastic, glass) and some other conditions, is made:
– cutting tool with the removal of a layer of material (Fig. 7.2a);
– knurling - by extruding screw protrusions (Fig. 7.2b);
- casting;
- pressing;
- stamping.
Rice. 7.3. Thread elements: a, b, d - external; c, e - internal
If the thread is made to a certain surface that does not allow
push the tool all the way to it, then it forms |
n e d o v o d |
||
7.3b, c). Escape together with a shortfall form |
n e w o r e s |
||
If it is required to make a thread of a full profile, without a run-off, then to output the thread-cutting tool, they make a hole, the diameter of which for the external thread should be slightly smaller than the internal diameter of the thread (Fig. 7.3d), and for the internal thread - a little greater than the outer diameter of the thread
would (Fig. 7.3d).
At the beginning of the thread, as a rule, a conical chamfer is performed, which protects the extreme turns from damage and serves as a guide when connecting parts to the thread (Fig. 7.8). Chamfering is performed before threading.
Corresponding GOSTs are installed on the thread and its elements (Table 7.2).
7.1.1. Thread image
Building an accurate image of the thread is time-consuming, so it is used in rare cases. According to GOST 2.311-68 "The image of the thread in the drawings", the thread is depicted conditionally, regardless of the thread profile.
IN in accordance with GOST 2.311–68, the carving is depicted:
- on the rod - with solid main lines along the outer diameter and solid thin lines along the inner diameter (Fig. 7.4a, b). On the views obtained by projecting onto a plane perpendicular to the axis of the rod along the inner diameter of the thread, an arc is drawn equal to ¾ of a circle, open anywhere;
In the hole - solid main lines along the inner diameter
And solid thin lines along the outer (Fig. 7.4c, d). On the pictures
obtained on a plane perpendicular to the axis of the hole along the outer diameter, an arc is drawn equal to ¾ of a circle, open anywhere.
Chamfers on a threaded rod and in a threaded hole that do not have a special design purpose, in projection onto a plane perpendicular to the axis of the rod or hole, are not shown.
A solid thin line when depicting a thread is applied at a distance of at least 0.8 mm from the main line and not more than the thread pitch.
Rice. 7.4. The image of the thread on the rod (a, b) and in the hole (c, d)
Parts in machines and mechanisms are somehow connected to each other. These connections perform various functions. Connections are divided into two types: movable and fixed, which, in turn, are divided into detachable and one-piece.
Detachable are called connections, the reassembly and disassembly of which is possible without damage (destruction) of their components. These include threaded, keyed, pin, slotted and other types of connections.
5.1 Threads
Thread- a surface formed during the helical movement of a flat contour along a cylindrical or conical surface.
5.1.1 Classification
By appointment threads are divided into fixing(in fixed connection) and running or kinematic (in mobile connection). Often fastening threads have a second function - sealing the threaded connection, ensuring its tightness.
depending from surface shapes, on which the thread is cut, it can be cylindrical or conical.
depending from the location of the surface carving can be outdoor(cut on a rod) or internal(cut into the hole).
depending from profile form distinguish thread triangular, trapezoidal, rectangular , round , special .
The triangular thread is subdivided into metric , pipe , conical inch, trapezoidal thread - on trapezoidal , stubborn , stubborn enhanced .
By step size distinguish between large, small and special threads.
By number of visits threads are divided into single pass And multiple .
In the direction of the helix distinguish thread right(the thread is cut clockwise) and left(the thread is cut counterclockwise).
Figure 5.1 - Classification of threads
5.1.2 Thread profiles and parameters
5.1.2.1 Thread profiles
The thread is formed during the helical movement of a certain flat figure that defines the so-called thread profile, located in the same plane with the axis of the surface of rotation (thread axis).
Thread profiles are characterized by the following features:
- metric thread has a profile in the form of an equilateral triangle with an angle at the apex 60 0 (Figure 5.2). Metric threads are cylindrical and conical;
- pipe thread has a profile in the form of an isosceles triangle with an angle at the apex 55 0 (Figure 5.2). Pipe threads can also be cylindrical and conical;
- conicalinch thread has a profile in the form of an equilateral triangle (Figure 5.2);
- round thread has a profile in the form of a semicircle;
- trapezoidal thread has a profile in the form of an isosceles trapezoid with an angle 30 0 between the sides (Figure 5.2);
- thrust thread has a profile of an unequal trapezoid with an angle of inclination of the working side 3 0 and non-working 30 0 (Figure 5.2);
- rectangular thread has a profile in the form of a rectangle (Figure 5.2). The thread is not standardized.
 |
 Thread metric (triangular) |
 |
 Cylindrical pipe thread |
 Conical pipe thread |
|
 Thread inch conical |
|
 |
 Round thread |
 Trapezoidal thread |
|
 Thread resistant |
|
 Rectangular non-standard thread |
Figure 5.2 - Types and parameters of threads
5.1.2.2 Thread parameters
Thread diameter (d) is the diameter of the surface on which the thread will be formed.
thread pitch(P) - distance along a line parallel to the axis of the thread between the midpoints of the nearest flanks of the same name of the thread profile, lying in the same axial plane on one side of the axis of rotation (GOST 11708-82).
Thread stroke- relative axial movement of a part with a thread in one revolution, equal to the product nP, Where n- the number of thread starts. For a single-start thread, the lead is equal to the lead.
A thread formed by the movement of one profile is called single pass , formed by the movement of two, three or more identical profiles is called multiple (two-, three-way, etc.).
5.1.3 Purpose of the thread and its elements
| thread type | Letter designation | Purpose |
|---|---|---|
| Metric | M… | Thread general purpose, standard fasteners |
| Metric conical | MK… | Instrumentation |
| Trapezoidal | Tr… | Lead screws transmitting reciprocating motion |
| stubborn | S… | Mechanisms with high axial force (screw presses, jacks) |
| Pipe cylindrical | G… | Pipe connection, fittings, valves |
| Pipe conical | R… (outer) Rc… (internal) |
Connection of pipes at high pressures and temperatures (increased tightness) |
| Round for electrical fittings | E… | Cartridges, plinths |
Depending on the conditions and nature of production, threading can be carried out in various ways and tools. For the manufacture of most standardized threads, threading with dies or taps is widely used.
The die is used for cutting external threads on a pre-prepared workpiece, the diameter of which is determined by the diameter and pitch of the thread being cut.
The working (cutting) surface of the die has a conical chamfer (chamfer) and a cylindrical gauge part, which ensures threading of the required size. As a result of the presence of the intake part on the threaded rod, at the end of the thread, there remains a section l 1 with a profile gradually decreasing in height (Figure 5.3, c). This section with incomplete thread is called thread run . The full profile thread, defined by the gauge portion of the die, ends on the shank where the thread starts to run. In the case when the cut part of the rod is limited by some supporting surface (shoulder, head, shoulder, etc.), when threading, the die (to avoid breakage) is usually not brought all the way to this surface.
In this case, a region remains on the rod, called thread failure. Escape plus underdrawing form thread undercut l 2 (Figure 5.3, c).
 |
||
| A | b | V |
Figure 5.3 - Threading a rod
The tap (Figure 5.4) is used for cutting internal threads in a pre-drilled hole, the diameter d 1 of which is selected depending on the pitch and diameter of the thread being cut (see table 5.2. (GOST 19257-73. Holes for cutting metric threads)).
| Thread pitch, R | Drill diameter, d 1 | Nominal thread diameter, d | Thread pitch, R | Drill diameter, d 1 | |
|---|---|---|---|---|---|
| 1 | 0,2 | 0,80 | 10 | 0,5 | 9,50 |
| 0,25 | 0,75 | 0,75 | 9,25 | ||
| 1,1 | 0,2 | 0,90 | 1 | 9,00 | |
| 0,25 | 0,85 | 1,25 | 8,80 | ||
| 1,2 | 0,2 | 1,00 | 1,5 | 8,50 | |
| 0,25 | 0,95 | 11 | 0,5 | 10,50 | |
| 1,4 | 0,2 | 1,20 | 0,75 | 10,25 | |
| 0,3 | 1,10 | 1 | 10,00 | ||
| 1,6 | 0,2 | 1,40 | 1,25 | 9,50 | |
| 0,35 | 1,25 | 12 | 0,5 | 11,50 | |
| 1,8 | 0,2 | 1,60 | 0,75 | 11,25 | |
| 0,35 | 1,45 | 1 | 11,00 | ||
| 2 | 0,25 | 1,75 | 1,25 | 10,80 | |
| 0,4 | 1,60 | 1,5 | 10,50 | ||
| 2,2 | 0,25 | 1,95 | 1,75 | 10,20 | |
| 0,45 | 1,75 | 14 | 0,5 | 13,50 | |
| 2,5 | 0,35 | 2,15 | 0,75 | 13,25 | |
| 0,45 | 2,05 | 1 | 13,00 | ||
| 3 | 0,35 | 2,65 | 1,25 | 12,80 | |
| 0,5 | 2,50 | 1,5 | 12,50 | ||
| 3,5 | 0,35 | 3,15 | 2 | 12,00 | |
| 0,6 | 2,90 | 15 | 1 | 14,00 | |
| 4 | 0,5 | 3,50 | 1,5 | 13,50 | |
| 0,7 | 3,30 | 16 | 0,5 | 15,50 | |
| 4,5 | 0,5 | 4,00 | 0,75 | 15,25 | |
| 0,75 | 3,75 | 1 | 15,00 | ||
| 5 | 0,5 | 4,5 | 1,5 | 14,50 | |
| 0,8 | 4,20 | 2 | 14,00 | ||
| 5,5 | 0,5 | 5,00 | 17 | 1 | 16,00 |
| 6 | 0,5 | 5,50 | 1,5 | 15,50 | |
| 0,75 | 5,25 | 18 | 0,5 | 17,50 | |
| 1 | 5,00 | 0,75 | 17,25 | ||
| 7 | 0,5 | 6,50 | 1 | 17,00 | |
| 0,75 | 6,25 | 1,5 | 16,50 | ||
| 1 | 6,00 | 2 | 16,00 | ||
| 8 | 0,5 | 7,50 | 2,5 | 15,50 | |
| 0,75 | 7,25 | 20 | 0,5 | 19,50 | |
| 1 | 7,00 | 0,75 | 19,25 | ||
| 1,25 | 6,80 | 1 | 19,00 | ||
| 9 | 0,5 | 8,50 | 1,5 | 18,50 | |
| 0,75 | 8,25 | 2 | 18,00 | ||
| 1 | 8,00 | 2,5 | 17,50 | ||
| 1,25 | 7,80 |
 |
||
| A | b | V |
Figure 5.4 - Threading a hole
Figure 5.4 shows a blind (blind) hole. At its bottom there is a conical recess left by the drill. The angle at the apex of the cone is conditionally taken equal to 120 0 , and its dimensions are not applied on the drawings.
Before threading at the end of the rod (with an external thread) and at the beginning of the hole (with an internal thread), chamfers , the conical surface of which forms an angle of 45 0 with the axis. The chamfer protects the extreme turns from damage, simplifies the process of threading, facilitates the connection of threaded parts. The amount of chamfers is determined by the amount of thread pitch (Table 5.3).
The tap, like the die, has a conical intake part and a calibrating part. When threading with a tap, there will be a thread run-out, determined by the tap's chamfer, and a full profile thread. When threading in a blind hole, the tap (in order to avoid its breakage) is not brought all the way to the bottom of the hole, therefore, there will be an undercut of the thread and, consequently, an undercut of the thread as the sum of the run-out and the undercut of the thread.
If it is required to make a thread of a full profile, without a run-off, then to withdraw the thread-forming tool, a groove is made, the diameter of which for the external thread should be slightly less than the internal diameter of the thread (Figure 5.5, a), and for the internal thread - slightly larger than the outer diameter of the thread (Figure 5.5 , b).
The dimensions of chamfers, runaways, undercuts, grooves are standardized by GOST 10549-80 * - Thread exit. Runs, undercuts, grooves and chamfers and GOST 27148-86 - Fasteners. Thread outlet. Run away, undercuts, grooves. Dimensions.
 |
|
| A | b |
Figure 5.5 - External and internal grooves
|
|||||||||||
| thread pitch P | groove | Chamfer z | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Type 1 | Type 2 | df | when mating with an internal thread with a groove type 2 | for all other cases | |||||||
| normal | narrow | ||||||||||
| f | R | R 1 | f | R | R 1 | f | R 2 | ||||
| 0 ,2 | — | — | — | — | — | — | — | — | — | — | 0 ,2 |
| 0 ,25 | |||||||||||
| 0 ,3 | |||||||||||
| 0 ,35 | d — 0 ,6 | 0 ,3 | |||||||||
| 0 ,4 | 1 ,0 | 0 ,3 | 0 ,2 | ||||||||
| 0 ,45 | d — 0 ,7 | ||||||||||
| 0 ,5 | 1 ,6 | 0 ,5 | 0,3 | 1 ,0 | 0 ,3 | 0 ,2 | d — 0 ,8 | 0 ,5 | |||
| 0 ,6 | d — 0 ,9 | ||||||||||
| 0 ,7 | 2 ,0 | 1 ,6 | 0,5 | 0,3 | d — 1,0 | ||||||
| 0 ,75 | d — 1,2 | 1 ,0 | |||||||||
| 0 ,8 | 3,0 | 1 ,0 | 0 ,5 | ||||||||
| 1 | 2 ,0 | 3 ,6 | 2 ,0 | d — 1,5 | 2 ,0 | ||||||
| 1,25 | 4 ,0 | 2 ,5 | 1 ,0 | 0 ,5 | 4 ,4 | 2 ,5 | d — 1,8 | 2 ,5 | 1 ,6 | ||
| 1 ,5 | 4,6 | d — 2 ,2 | 3 ,0 | ||||||||
| 1,75 | 5 ,4 | 3 ,0 | d — 2 ,5 | 3 ,5 | |||||||
| 2 | 5 ,0 | 1 ,6 | 3,0 | 5 ,6 | d — 3 ,0 | 2 ,0 | |||||
| 2 ,5 | 6 ,0 | 1 ,0 | 4 ,0 | 7 ,3 | 4 ,0 | d — 3 ,5 | 5 ,0 | 2 ,5 | |||
| 3 | 7 ,6 | d — 4 ,5 | 6 ,5 | ||||||||
| 3 ,5 | 8 ,0 | 2 ,0 | 5 ,0 | 1 ,6 | 10 ,2 | 5 ,5 | d — 5 ,0 | 7,5 | |||
| 4 | 10,3 | d — 6 ,0 | 8,0 | 3,0 | |||||||
| 4 ,5 | 10 ,0 | 3 ,0 | 6 ,0 | 1 ,0 | 12 ,9 | 7 ,0 | d — 6 ,5 | 9 ,5 | |||
| 5 | 13 ,1 | d — 7 ,0 | 10 ,5 | 4 ,0 | |||||||
| 5 ,5 | 12 ,0 | 8 ,0 | 2 ,0 | 15,0 | 8 ,0 | d — 8 ,0 | |||||
| 6 | 16 ,0 | 8 ,5 | d — 9 ,0 | ||||||||
5.1.4 Image and designation of threads in the drawings
The rules for the image and application of the thread designation in the drawings are established by GOST 2.311-68 *.
The carving is depicted:
a) on the rod - with solid main lines along the outer diameter of the thread and solid thin lines - along the inner diameter for the entire length of the thread, including the chamfer. 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, open anywhere, but not along the axes (Figure 5.6, a);
b) in the hole - with solid main lines along the inner diameter of the thread and solid thin lines - along the outer diameter. On images obtained by projecting onto a plane perpendicular to the axis of the hole, an arc is drawn along the outer diameter of the thread with a solid thin line equal to 3/4 of the circle, open anywhere (Figure 5.6, b).
 |
|
| A | b |
Figure 5.6 - Image of the thread in the drawings: external - on the rod (a), internal - in the hole (b)
A solid thin line on the image of the thread is applied at a distance of at least 0.8 mm from the main line and not more than the thread pitch. The line defining the thread boundary is applied on the rod and in the threaded hole at the end of the full thread profile (before the start of the run). The thread boundary is drawn to the line of the outer diameter of the thread and is depicted as a solid main or dashed line if the thread is shown as invisible (Figure 5.7, 5.8), where l st- the length of the rod on which the thread is cut, l sv- drilling depth of the threaded hole.
Figure 5.7 - Image of the visible thread boundary
Figure 5.8 - Image of the invisible thread boundary
Hatching in sections and sections is carried out to the line of the outer diameter of the thread on the rods and to the line of the inner diameter in the hole, i.e. in both cases to a solid main line.
Thread length dimension with full profile (without run-out l) on the rod and in the hole are indicated as shown in Figure 5.7, 5.9.
If it is necessary to indicate the amount of run-off on the rod, the dimensions are applied, as shown in Figure 5.9, c. The thread run is depicted as a solid thin line drawn either along the radius or as a segment approximately at an angle of 30 0 (Figures 5.9, b).
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| A | b | V |
Figure 5.9 - Image of the thread run, thread length dimension
The undercut of the thread, made to the stop, is depicted as shown in Figure 5.7. Chamfers on a threaded rod and in a threaded hole that do not have a special design purpose, in projection onto a plane perpendicular to the axis of the rod or hole, are not depicted (Figures 5.6, a, b). A solid thin line of the image of the thread on the bar must intersect the line of the chamfer boundary.
On sections of a threaded connection in the image on a plane parallel to its axis, only the part of the thread that is not covered by the thread of the rod is shown in the hole (Figures 5.10).
Figure 5.10 - Image of a threaded connection
Thread designations indicate, according to the relevant standards, the dimensions and limit deviations of the thread and apply them to all threads, except conical and tubular cylindrical, to the outer diameter, as shown in Figures 5.4, 5.11.
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| A | b |
Figure 5.11 - Dimensioning threads
The designation of tapered threads and cylindrical pipe threads is applied as shown in Figure 5.12.
Figure 5.12 - Dimensioning pipe and tapered threads
5.1.5 Mounting threads
5.1.5.1 Metric thread
Metric thread is the most widely used in engineering.
The thread profile (Figure 5.2) is set in GOST 9150-81; the main dimensions (nominal values) of the outer, middle and inner thread diameters are in GOST 24705-2004; diameters and steps - GOST 8724-81 (Appendix A) - see table 5.6.
M.Metric threads are made with large(the only one for a given thread diameter) and small steps, which for a given diameter can be several. Therefore, in the designation of a metric thread, a large pitch is not indicated, but a small pitch is required.
Designation: M20x1.5-6g - metric external thread(on a rod) with a diameter of 20 mm with a fine pitch of 1.5 mm (Fig. 5.11, a); M20 LH-6g - the same left, with a large step; M20x1.5 LH-6g - the same with a small step; M20-6N - internal thread (in the hole) with a large pitch (Fig. 5.11, b). It is mandatory to specify the thread tolerance field.
5.1.5.2 Metric conical thread
Metric conical thread (GOST 25229-82) is used to connect pipelines.
Designation: MK8 * 1 - metric conical with a diameter of 8 mm, measured in the main plane and a step of 1 mm (Fig. 5.12, b).
5.1.5.3 Pipe thread, cylindrical
Cylindrical pipe threads according to GOST 6357-81 are used on water and gas pipes, parts for their connection (couplings, elbows, crosses, etc.), pipeline fittings (gate valves, valves, etc.).
The profile of a cylindrical pipe thread is shown in Figure 5.2.
The symbol includes the letter G, thread size in inches, accuracy class of the average thread diameter - A or B (less accurate) and make-up length in mm, if it exceeds the normal one established by the standard.
Example: G 1/2 (Fig. 5.12, a), G 1/4-A, G 1/2 LH-A, G 3/8-A-20.
If for a metric thread the size of the diameter indicated in the designation corresponds to its actual size (excluding tolerance), then in a pipe thread its size in inches indicated in the designation is approximately equal to nominal diameter of the pipe(nominal inside diameter, from which its throughput is calculated), converted to inches.
For example, G1 denotes the size of a pipe thread cut on the outer surface of a pipe having a nominal bore of 25 mm, i.e. approximately 1 inch. In fact, the outer diameter of the pipe is 33.249 mm, i.e. more than two pipe wall thicknesses - table 5.5.
Therefore, the designation of the size of the pipe thread is applied on the shelf of the leader line (Figure 5.13).
Figure 5.13 - Designation of pipe thread
| thread size, inch | 1/4 | 3/8 | 1/2 | 3/4 | 1 | 1 ¼ |
|---|---|---|---|---|---|---|
| Conditional pass , mm | 9 | 10 | 15 | 20 | 25 | 40 |
| Pipe outside diameter, mm | 13,5 | 17,0 | 21,3 | 26,8 | 33,5 | 48,0 |
| Outer thread diameter, mm | 13,16 | 16,67 | 20,96 | 26,44 | 33,25 | 47,80 |
5.1.5.4 Conical pipe thread
Tapered pipe threads according to GOST 6211-81 are used in pipe connections at high pressures and temperatures, when increased tightness of the connection is required.
See Figure 5.2 for the thread profile. Since the diameter of the tapered thread is constantly changing, its size is referred to the section in the main plane (approximately in the middle of the length of the external thread). In this section, the diameter of the conical thread is equal to the diameter of the cylindrical pipe thread (Figure 5.14). The position of the main plane is indicated on the working drawing (taken from the standard).
Figure 5.14 - Designation of pipe conical thread
External thread is indicated by the letter R, internal - Rc.
The designation of pipe tapered threads includes the letter R (Rc) and the size in inches without specifying the dimension.
Example: R 1 1/2 LH - outer left, Rc 1/8 - inner (Fig. 5.12, c).
5.1.5.5 Conical inch thread
conical inch thread(GOST 6111-52) is used in connections of fuel, oil, water, air pipelines of machines and machine tools at low pressures.
The designation consists of a letter TO and the thread size in inches, indicating the dimension, is applied on the leader line shelf, as with pipe threads.
Example: K 3/4″ GOST 6111-52.
5.1.5.6 Round thread
Round threads are used for mixer valve spindles in accordance with GOST 19681-94 (sanitary fittings for water folding) and water taps in accordance with GOST 20275-74.
The designation of a round thread includes letters Cr, nominal thread diameter in mm, thread pitch in mm and GOST 13536-68.
Example: Kr 12x2.54 GOST 13536-68, where 2.54 is the thread pitch in mm, 12 is the nominal thread diameter in mm. GOST 13536-68 defines the profile, basic dimensions and tolerances of round threads.
5.1.6 Lead threads
5.1.6.1 Trapezoidal thread
It is used on screws that transmit reciprocating motion and axial force. Carving happens single pass And multiple .
The thread profile is shown in Figure 5.2.
The main dimensions, diameters, pitches, tolerances of a single-start thread are standardized according to GOST 24737-81, 24738-81, 9562-81.
For multi-start threads, these parameters are in GOST 24739-81 *.
Conventional designation of a single-start thread consists of letters Tr, values of the nominal thread diameter, pitch, tolerance field.
Example: Tr 40x6-8e - trapezoidal single-start external thread with a diameter of 40 mm with a pitch of 6 mm, Tr 40x6-8e-85 - the same make-up length 85 mm, Tr 40x6LH-7H - the same for the inner left.
IN multi-start thread symbol the numerical value of the stroke is added: Tr 20x8 (P4) -8e - trapezoidal multi-start external thread with a diameter of 20 mm with a stroke of 8 mm and a pitch of 4 mm.
5.1.6.2 Thrust thread
It is used on screws subject to unilaterally directed forces, for example in jacks.
4.1 MAIN THREAD FEATURES
For any thread, the following main elements are distinguished: profile; profile angle and height; step; outer, middle and inner thread diameters.
The thread profile (Fig. 257) is considered in a section passing through the axis of the bolt or nut. A thread (coil) is a part of the thread formed during one complete revolution of the profile.
Angle α profile - the angle between the sides (faces) of the thread profile, measured in a plane passing through the axis of the bolt. In a metric thread, this angle is 60 °, in an inch - 55 °.
Height (depth, threads) H Profile - the distance from the top of the thread to the bottom of the profile, measured perpendicular to the axis of the bolt.
Pitch P thread - the distance between parallel sides or tops of two adjacent turns, measured along the axis of the thread. Rice. 257. The main elements of the thread
In metric threads, the pitch is expressed in millimeters; inch thread is characterized by the number of threads (turns) per inch.
The outer diameter d of the thread is the diameter of the cylinder described near the threaded surface. The outer diameter is measured for bolts along the tops of the thread profile, for nuts - along the troughs.
The inner diameter of the thread is the diameter of the cylinder inscribed in the threaded surface. The inner diameter is measured for bolts along the hollows, for nuts - along the tops of the thread profile.
The average thread diameter d is the diameter of a cylinder coaxial with a thread, the generatrix of which is divided by the sides of the profile into equal segments.
4.2 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 is used (Fig. 258, a); usually it is called fastener, as it is cut into fasteners, such as studs, bolts and nuts.
Tapered triangular threads make it possible to obtain a tight connection. Such threads are found on conical plugs, sometimes in oilers.
Rectangular thread (Fig. 258,b) has a rectangular (square) profile. It is not standardized, difficult to manufacture, fragile and rarely used.
Trapezoidal tape thread (Fig. 258, c) has a cross section in the form of a trapezoid with a profile angle of 30 °. Its coefficient of friction is small, so it is used to transmit movements or large forces in machine tools(lead screws), jacks, presses, etc. The coils of this thread have a large section at the base, which ensures its high strength and ease of cutting. The main elements of the trapezoidal thread are standardized.
The thrust thread (Fig. 258, d) has a profile in the form of an unequal trapezoid with a working angle at the top equal to 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.).
Round thread (Fig. 258, e) has a profile formed by two arcs, conjugated with small straight sections, and an angle of 30 °. In mechanical engineering, this thread is rarely used. It is mainly used in joints subjected to heavy wear, in a polluted environment (fire pipeline fittings, wagon ties, hooks lifting machines and so on.). 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 in one revolution. For single-start threads, the lead is equal to the pitch (the distance between adjacent turns), and for multi-start threads, it is the product of the lead by the number of starts.
The latter can be determined by looking at the end of the screw (nut); it is usually clearly visible how many threads originate from the end (Fig. 259, a, b). For a single-start thread, only one end of the coil is visible at the end of the screw or nut, while for multi-start threads, two, three or more.
Drawing. 259. Types of threads depending on the number of entries: a - three-start,
b - eight-way
Single-start threads have small helix angles and greater friction (low efficiency). They are used where a reliable connection is required (in fasteners).
In multi-start threads, compared to single-start threads, the helix angle is much larger. 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.
4.3 Main types of threads and their designation
In mechanical engineering, as a rule, three thread systems are used - metric, inch and pipe.
Metric thread (Fig. 260, a) has a triangular profile with flat-cut tops; profile angle is 60°, diameters and pitch are expressed in millimeters.
Metric threads are divided into threads with a normal pitch (for outer diameters 1 .... 68 mm) and fine pitch threads (for outer diameters 1 ... 600 mm).
Metric threads with a normal pitch denote M20 (the number is the outer diameter of the thread), with small pitches - M20X1.5 (the first number is the outer diameter, the second is the pitch).
Metric threads are used mainly as fasteners: with a normal pitch - with significant loads and for fasteners (bolts, nuts, screws), with small pitches - with small loads and fine adjustments.
An inch thread (Fig. 260, b, d) has a triangular flat-cut profile with an angle of 55 ° (Whitworth thread) or 60 ° (Sellers thread). All dimensions of this thread are expressed in inches (1 "= 25.4 mm). The pitch is expressed as the number of threads (turns) in the length of one inch.
Inch threads are standardized with diameters from 3/16 to 4 "and the number of threads per 1", equal to 24 ... 3. The outside diameter of the thread is expressed in inches. The inch thread differs from the metric one in a large pitch.
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.
Cylindrical pipe thread (Fig. 260, c) is standardized, is a small inch thread, but unlike the latter, it mates without gaps (to increase the tightness of the connection) and has rounded tops.
The nominal diameter of a pipe thread is taken to be the internal diameter of the pipe (hole diameter, or, as they say, "pipe clear diameter"), i.e. the outer diameter of the pipe thread will be larger than the nominal diameter by twice the pipe wall thickness.
Cylindrical pipe thread is used for outer diameters 1/8 ... 6 "with the number of threads per inch from 28 to 11; the profile angle is 55 °. It is used on pipes for their connection, as well as on pipeline fittings and other thin-walled parts.
Cylindrical pipe threads are designated as follows: Pipes 3/4 "(numbers are the nominal diameter of the thread in inches). Pipe threads are standardized with diameters from 1/8 to 6" with the number of threads per inch from 28 to 11
Conclusion
In this essay, it was considered: the device of a vertical milling machine, the principle of its operation; some types of cutters for processing shaped surfaces, classification of bench vise; one of the types of metal processing is sawing.
References
1. N.I. Makienko. General plumbing course. M. 1984
2. P.M. Money, G.M. Stiskin, I.E. Thor. Turning business. M. 1976
3. B.G. Zaitsev, S.B. Rytsev. Handbook of a young turner. M. 1988
4. V.A. Slepinin. Manual for training metal turners. M. 1974
5. Milling business: Textbook for secondary vocational technical schools - 3rd ed., Revised. and additional - M.: Higher school, 1980.-208 p., ill. (Professional education. Machining).
