GOST 9484 - 81

Trapezoidal thread has a 30 ° profile. Thread pitch measured in millimeters.

Trapezoidal thread it is used in the units of mechanisms for converting rotary motion into translational, for example: lead screws of machine tools, power screws of presses, lifting screws, etc. Carvings of this type can withstand significant loads.

Trapezoidal thread denoted by letters Tr- English. trapezoidal:

• Tr 28 × 5- diameter 28mm, pitch 5mm
• Tr 28 × 5 LH- diameter 28mm pitch 5mm left thread
• Tr 20 × 8 (P4)- diameter 20 mm, pitch 4 mm and stroke 8 mm multi-start thread
• Tr 20 × 8 (P4) LH- diameter 20 mm, pitch 4 mm and stroke 8 mm, multi-start thread left

d- outside diameter external thread(screw)

D- outer diameter of internal thread (nut)

d 2- the average diameter of the external thread

D 2- average diameter of internal thread

d 1- inner diameter of external thread

D 1- internal diameter of an internal thread

P- thread pitch

H- the height of the original triangle

H 1- working height of the profile

The operation of drives of many machines, equipment and mechanisms is based on such a process as the transformation of rotational motion into translational motion. This principle is used, for example, by drives for measuring machines and equipment, gate valves and valves, scanning tables, robots and machine tools.

In order to effectively convert the rotation of a certain part into the translational movement of another part, a screw-nut pair is most often used. Such transmissions are products that have general machine-building applications, and it should be noted that the performance, functionality and reliability of that equipment largely depend on how well they are designed and manufactured. constituent parts which they are.

Due to the fact that the screw-nut gears have an increased smoothness of engagement, they are almost completely silent during operation. Their design is relatively simple, and one of the undoubted advantages is that their use allows you to achieve significant gains in strength. Generally speaking, a screw-nut transmission is no different from a conventional one from a technical point of view. threaded connection however, since they are used to transmit motion, they are manufactured in such a way that the frictional force in the thread is minimal.

In principle, this can be achieved by using a rectangular thread, but it also has its drawbacks. For example, it cannot be cut on standard threading machines, and compared to trapezoidal threads, it has a much lower strength. These factors lead to the fact that in screw-nut gears, rectangular threads are rarely used. In them, the most common trapezoidal thread, having a coarse, medium and fine pitch, as well as a persistent thread.

Most often in gears, a screw-nut can be found trapezoidal thread with an average pitch. Its same, but with a small step, is used when it is necessary to provide a small movement, and with a large step - when the device is operated in difficult conditions. In addition, due to the features of the profile, trapezoidal thread can be successfully used in mechanisms requiring reverse movement. Such threads are single and multi-start, right-hand and left-hand.

The main requirements for those materials that are used in screw-nut gears are wear resistance, strength and good machinability. As for those screws that are not hardened, they are made from steels A50, St50 and St45, and those that are hardened - from steels 40HG, 40X, U65, U10... Nuts are usually made of bronze BrOCS-6-6-3 or BROFYU-1.

Thread profiles and sizes

The standard applies to trapezoidal threads and sets the profiles and dimensions of its elements.

MAIN PROFILE

An example of a symbol for a trapezoidal single-start thread with a nominal diameter of 20 mm, a pitch of 4 mm and a tolerance field of an average diameter of 7e:

Tg 20 x 4 -7e

RATED PROFILES
external and internal thread

h 3 - the height of the profile of the external thread; H 4 - the height of the profile of the internal thread; d 3 - inner diameter of the outer thread; D 4 - outer diameter of the internal thread; R 1 - radius of rounding at the top of the external thread; R 2 - radius of twisting in the cavity of the external and internal threads; a c - clearance at the top of the thread.

DIAMETERS AND STEPS
single-start trapezoidal thread according to GOST 24737-81

Preferred diameters and pitches are specified in GOST 24738-81. Numerical values tolerances of diameters and pitches - according to GOST 9562-81

DIAMETERS AND STEPS
trapezoidal multi-start thread according to GOST 24739-81

Notes:
1. Steps with boxes are preferred.
2. The steps in parentheses are not recommended when developing new designs.
3. Threads for which the stroke value is marked with * have a lead angle of more than 10 o. For these threads, it is necessary to take into account the deviation of the profile shape during manufacture.
4. In technically and economically justified cases, it is allowed to use other values ​​of the nominal thread diameters in accordance with GOST 24738-81.
5. When choosing thread diameters, the first row should be preferred over the second.

An example of a symbol for a trapezoidal multi-start thread with a nominal diameter of 20 mm, a stroke of 8 mm, a pitch of 4 mm and a tolerance field of 8e:

Tg 20-8 (P4) - 8e

The same, left:

Tg 20-8 (P4) LH - 8e

The make-up length, if it differs from the thread length, is indicated in millimeters at the end of the thread designation, for example:

Tg 20-8 (P4) LH - 8e - 180

The numerical values ​​of the make-up lengths related to the N and L groups are in accordance with GOST 9562-81.

Landing in a threaded connection is indicated by a fraction

Tg 20-8 (P4) LH - 8Н / 8е - 180

Numerical values ​​of tolerances of diameters d and D 1 - according to GOST 9562-81.
Numerical values ​​of tolerances of diameters d 2, d 3 and D 2 - according to GOST 24739-81.

Application of trapezoidal thread

A trapezoidal screw thread is a lead thread that has a relatively great strength friction, it is self-braking. The advantage for lifting technology - in the resting position does not require additional fixation.

Trapezoidal thread is used to convert rotary motion into translational motion and is used primarily for straight motion. It also finds its application as a lead screw in lathes or as a drive thread for screw presses on tables or vehicle bridges.

Application examples for trapezoidal spindle threads:

Feed movement on machine tools (eg adjusting screws and lead screws);
- movement on the manipulator;
- regulation of movement on lifting mechanisms and forklift trucks;
- movement of the shutter when locking the injection molding machines;
- movement of movement on collection containers;
- vertical movement when working with a press.

Related documents:

GOST 3469-91: Microscopes. Lens thread. Dimensions (edit)
GOST 4608-81: Metric thread. Interference landings
GOST 5359-77: Eyepiece thread for optical instruments. Profile and dimensions
GOST 6042-83: Round Edison thread. Profiles, sizes and limit sizes
GOST 6111-52 - Conical inch thread with a profile angle of 60 degrees
GOST 6211-81: Conical pipe thread
GOST 6357-81: Cylindrical pipe thread
GOST 8762-75: Round thread with a diameter of 40 mm for gas masks and gauges for it. Basic dimensions
GOST 9000-81 - Metric thread for diameters less than 1 mm. Tolerances
GOST 9484-81: Trapezoidal thread. Profiles
GOST 9562-81: Single-start trapezoidal thread. Tolerances
GOST 9909-81: Thread of tapered valves and cylinders for gases
GOST 10177-82: Threaded thread. Profile and main dimensions
GOST 11708-82: Thread. Terms and Definitions
GOST 11709-81: Metric thread for plastic parts
GOST 13535-87: Threaded reinforced thread 45 degrees
GOST 13536-68: Round thread for sanitary fittings. Profile, main dimensions, tolerances
GOST 16093-2004: Metric thread. Tolerances. Clearance fits
GOST 16967-81: Metric thread for instrument making. Diameters and steps
GOST 24737-81: Single-start trapezoidal thread. Basic dimensions
GOST 24739-81: Trapezoidal multi-start thread
GOST 25096-82: Threaded thread. Tolerances
GOST 25229-82: Metric tapered thread
GOST 28487-90: Tapered tool joint thread for drill string elements. Profile. Dimensions. Tolerances

The thread profile is an isosceles trapezoid with an angle of 30 ° between the sides (Figure 3, c). Trapezoidal thread can be single-start and multi-start, right-hand and left-hand.

The diameters and steps of a single-start trapezoidal thread in the range of diameters from 12 to 50 mm are given in table. 2. The same dimensions and number of starts for multi-start threads are given in table. 3.

Examples of thread designation:

trapezoidal single-thread with a nominal diameter of 36 mm and a pitch of 6 mm:

TgZbhb; the same, left-hand thread:

Tg 36x6 LH;

trapezoidal, three-way with a nominal diameter of 40 mm, a pitch of 3 mm and a stroke of 9 mm:

Tg 40 NS 9 (RZ)

Examples of thread designations in the drawing are shown in Fig. 5. at

Table 2. Diameters and steps of a trapezoidal single-start thread according to GOST 24738 81, mm

Note: 1. When choosing a thread, the first row should be preferred to the second;

2. Preferred steps are marked with *.

Table 3. The main dimensions of the trapezoidal multi-start thread according to GOST 24739 81, mm

Note: Threads with travel in parentheses have a lead angle greater than 10 °.

The thread is persistent.

The main purpose of the thread is to transfer axial load by means of a screw in one direction, for example, in jacks, presses, etc. The thread profile is an unequal trapezoid (Fig. 3, d).

:> v Diameters and steps of the thrust thread in the range of diameters from 16 to 42 mm are given in table. 4.

Examples of thread designation: "

thrust one-start right-hand with a diameter of 32 mm with a step of 6 mm:

the same, left-hand thread:

S32x6LH. In the drawing, the thread is indicated as shown in fig. 6.

Rice. 6

Table 4. Diameters and steps of thrust thread according to GOST 10177 82, mm.

Note ^. When choosing thread diameters, the first row should be preferred over the second.

Steps to be preferred when developing new designs.

Pipe cylindrical thread.

This thread is used in cylindrical pipe connections and connections of an internal cylindrical thread with an external tapered thread.

The profile (Fig. 3, b) and the main dimensions are established by GOST 6357 81. The values ​​of the main dimensions of the cylindrical pipe thread are given in table. 5.

The pipe thread designation (Fig. 7, a, b) consists of the letter G and the thread size in inches, for example:

This designation is conditional, since indicates the diameter not of the thread, but of the hole in the pipe (nominal bore DN at a certain wall thickness). The outer diameter of the pipe thread will be larger than that indicated in the drawing. For example, the notation G1 corresponds to pipe thread having an outer diameter d = 33.25m for pipes with an inner diameter of 1 "(25.4 mm).

Parallel pipe thread of the same diameter ( conditional pass DN) can be made on pipes with different wall thicknesses and even on a solid rod.

Rice. 7. Symbols cylindrical and tapered pipe threads: a) cylindrical pipe threads G 1 1/2;

b) left-hand internal thread of the same size; c) external pipe tapered thread; d) inner tube conical

Table 5. Main dimensions of straight pipe thread

Trapezoidal thread is widely used to make various screws, which are used for various production equipment. For example, for machine tools, lifting devices, presses. Such a thread has the form of an isosceles trapezoid, while the profile angle can have different values: 15, 24, 30, 40 °. During the operation of the screw on which it is cut trapezoidal thread, natural frictional forces appear. That is, due to the presence of lubricant, surface roughness, as well as the profile angle.

Thread types

Today there are such types:

1. Metric. It serves to secure several elements. The slicing conditions are set in regulatory documents... The profile is a triangle with equilateral corners. This indicator is 60 °. Metric screws are available in small and large pitches. The first type is used to fix thin-sheet elements to create increased tightness. This type of connection can be found in precision optical instruments.
2. Conical. It is made in the same way as the previous type, but twisting is performed to a depth of 0.8 mm.
3. Inch. To date, there is no normative document that would indicate the dimensions of the thread. Inch thread is used for repair various equipment... As a rule, these are old devices and devices. Its main indicators are the outer diameter and pitch.
4. Tubular cylindrical. This view is an isosceles triangle, top corner which is 55 °. Such an internal thread is used to connect pipelines, as well as parts made of thin sheet material. It is recommended when there are special requirements for the tightness of the connection.
5. Tubular conical. The internal thread must meet all the requirements of the regulatory documents. The sizes are completely standardized. It is used to connect various types of pipelines.
6. Persistent. This view is an unequal trapezoid, where one of the sides is inclined by 3 °, and the other - by 30 °. The first side is working. The shape of the profile as well as the diameter of the steps are determined regulatory documents... In accordance with them, the thread is made with a diameter of 10 to 600 mm, while the maximum value of the pitch is 24 mm. They are used where higher holding forces are required.
7. Round. A thread profile is represented by various arcs connected by straight lines. The profile angle is 30 °. This type of thread is used for those connections that are exposed to aggressive media.
8. Rectangular. It is not enshrined in any normative documents. Its main advantage is its high efficiency. Compared to the trapezoidal view, it is less durable, and also causes a lot of confusing moments in its production. The main place of application is jacks and different kinds screws.
9. Trapezoidal. Has the shape of an isosceles trapezoid with a profile angle of 30 °. Trapezoidal thread, the dimensions of which are fixed in the documentation, are used to connect various elements of production equipment.

Manufacturing conditions

Compared to other types, trapezoidal threads are much easier to manufacture.

That is why it is often used in various fields. The most popular is the trapezoidal screw with a 30 ° profile angle. The production technology is very similar to that used for cutting rectangular threads. But there are still significant differences in terms of precision and cleanliness. Cutting trapezoidal threads is no different from the same procedure with a rectangular look. At the moment, there are several such methods.

Making a screw with one cutter

Single-start trapezoidal thread is made as follows:

• the workpiece is prepared and the channels for sharpening are guided;
• sharpening of the cutter is performed according to a special prepared template;
• installation and fastening of the sharpened element are made. It should be located so that the centers coincide and are parallel to the cutting axis;
• the equipment turns on and the workpiece is fed for threading;
• the finished part is checked according to the finished template.

Cutting with three incisors

This method is as follows:

• a blank is being prepared;
• sharpening of three cutters is performed - straight, narrow and profile;
• the installation and fastening of the prepared elements is carried out. They can be located both perpendicular and parallel to the thread axis. It all depends on the angle of inclination.

Common manufacturing method

It is in production that trapezoidal threading takes place in this way:

• working equipment is checked and adjusted;
• thanks to the slotted cutter, small indentations are made on the screw;
• using a narrow slotted element, the screw is cut to a certain diameter;
• with the help of a profile slotted element, the final production of the trapezoidal thread is carried out;
• the finished part is checked in accordance with the ready-made templates.

Trapezoidal thread: dimensions

As stated earlier, given view the thread has the shape of a trapezoid, in which the angle between the sides can have different values. All basic dimensions are set in accordance with GOST.

For a single-start type, the trapezoidal thread (dimensions - GOST 9481-81) has dimensions and pitches of various diameters - from 10 to 640 mm. In addition, it can be multi-way, as well as twisted to the left or right side. These indicators are standardized by GOST 24738-81.

Where is used

For the functioning of any element, for example a machine or mechanism, it is necessary to fulfill a prerequisite: rotational movements must be transformed into translational ones.

This principle is used for the manufacture of various machine tools, devices, control systems used in the industrial field.

Thread advantages

The efficiency of work on converting rotary movements into translational ones is carried out with the help of a nut and a screw. While these parts look simple, they require care in their manufacture. It is on these parts that performance and reliability depend, not only constituent elements but also all working equipment.

Features of multi-start thread

To endow the screw with strength characteristics and increase its stroke, a multi-start trapezoidal thread is used. In this case, all parameters, such as the height of the thread, its diameter are absolutely the same, with a single-start view. The only difference is the number of moves per step. For example, three-way types of threads have a stroke three times their pitch. All this can be seen in the figures.

Let's give an example so that this view becomes understandable to every person. Everyone uses regular lids for canning fruits and vegetables. To open them, you need to make a minimum of effort. When using cylinders large diameters getting into the grooves of a one-way thread is much more difficult. That is why they use multi-way.

This type of thread can be identified visually, just look at the picture.

You can see exactly how many turns go from the beginning of the screw. Multi-lead threads are manufactured using complex technologies, and, accordingly, are more expensive.

Other advantages

Trapezoidal joints have many positive qualities... That is why they are used in various manufacturing industries. The most common area is mechanical engineering. So, their advantages include the following:

• the ability to assemble and disassemble various devices unlimited number of times;
• convenient process of disassembly and assembly;
• reliability of the threaded connection;
• easy manufacturing process;
• independent regulation of the compression force;
• production of parts in various designs.

Disadvantages of connections

There are not so many negative sides of this type of connection. One of them is the occurrence of great tension in the valleys. In addition, they cannot be used in devices and mechanisms that have high vibration, since the screws can unscrew themselves, which is not a good sign.

Therefore, it is necessary to monitor this, and in case of such a situation - to correct the position of the screws.

Such quality as cost can be attributed to both positive and negative sides.

Single-lead threads cost significantly less than multi-lead threads. Here everyone chooses according to personal preference. Many design organizations use precisely multi-lead threads, since they are distinguished by their reliability and strength.

So, we found out what this type of connection is, such as a trapezoidal thread, its dimensions, advantages and disadvantages.

In mechanisms where it is necessary to convert rotation into translational movement, they are used. In addition to its transformation function, this thread can withstand increased loads. This is a demanded type of thread in important units of mechanisms, machine tools. You can observe the principle of operation of this thread when tightening the screws, when the rotation of the screw makes it move in a linear direction. The force applied to transform motion depends on the profile angle, thread pitch and part material.

The name of the thread is from the resemblance to the trapezoid.

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Main characteristics of trapezoidal thread

The trapezoid shape is formed by the angle of the thread profile. In this type, the profile angle can be in the range of 15 - 40 degrees.

In the work process, threads can cause excessive friction. This factor is influenced by the profile angle, the type of lubricant and the material used. Radial gaps in a trapezoidal thread can be identified by positioning the thread in the middle of the diameter.

Trapezoidal thread is quite simple to manufacture. In most cases, the profile angle is set to 30 degrees. The quality of the thread depends largely on the accuracy of the workpiece used, as well as the material.

Trapezoidal thread cutting methods

The production of this type of thread can be divided into two categories - one cutter and three cutters.

As an example, consider this designation: Tr 26 × 4 LH - trapezoidal thread, single-start, with a diameter of 26 and a pitch of 4, left.

GOST 9484-81 is used as the main standard.