Trapezoidal thread is widely used for the manufacture of various screws, which serve for various production equipment. For example, for machine tools, lifting devices, presses. Such a thread has the form of an isosceles trapezium, and the profile angle can have different values: 15, 24, 30, 40 °. During the work of the screw, on which the trapezoidal thread is cut, frictional forces appear that are caused by the natural way. That is, due to the presence of lubricant, surface roughness, and the profile angle.
Types of thread
For today there are such types:
- Metric. It serves to fasten several elements. Cutting conditions are set in the normative documentation. The profile is a triangle with equilateral angles. This figure is 60 °. Screws with metric thread are made with small and large steps. The first type is used to fasten thin sheet elements to create increased tightness. This type of connection can be found in precise optical instruments.
- Conical. It is also manufactured as the previous type, but the twisting is carried out to a depth of 0.8 mm.
- Inch. To date, there is no regulatory document, which would indicate the size of the thread. Inch threads are used for repair of various equipment. As a rule, these are old devices and devices. Its main indicators are the external diameter and pitch.
- Tubular cylindrical. This species is an isosceles triangle with an upper angle of 55 °. Such an internal thread is used to connect pipelines, as well as parts made of thin sheet material. It is recommended in the case when special requirements are imposed on the tightness of the connection.
- Pipe conical. The internal thread must comply with all requirements of regulatory documents. The dimensions are fully standardized. It is used to connect various types of pipelines.
- Stubborn. This type represents an unequal trapezoid, where one side is inclined by 3 ° and the other by 30 °. The first party is working. The form of the profile, as well as the diameter of the steps, are determined by regulatory documents. In accordance with them, the thread is made from 10 to 600 mm in diameter, with the maximum step value being 24 mm. They are used where increased holding forces are required.
- Round. The thread profile is a different arc, connected by a straight line. The profile angle is 30 °. This type of thread is used for those compounds that are affected by aggressive media.
- Rectangular. It is not fixed by any normative documents. Its main advantage is high efficiency. In comparison with the trapezoidal view, it is less durable, and also causes a lot of incomprehensible moments in its production. The main place of application - jacks and various types of screws.
- Trapezoidal. It has the shape of an equilateral trapezoid with a profile angle of 30 °. Trapezoidal thread, the dimensions of which are fixed in the documentation, is used to connect various elements of production equipment.
Compared to other types of trapezoidal thread is much easier to manufacture.That is why it is often used in various spheres. The most popular screw is a trapezoidal thread with a profile angle of 30 °. The technology of production is very similar to that used for cutting rectangular threads. But nevertheless there are essential differences, concerning accuracy and cleanliness of manufacturing. Cutting trapezoidal thread is no different from the same procedure with a rectangular view. At the moment there are several such ways.
Manufacture of a single-cutter screw
The trapezoidal single-thread thread is manufactured in this way:
- prepares the workpiece and guides the sharpening channels;
- the tool is sharpened according to a special prepared template;
- installation and fastening of the sharpened element are made. It should be arranged so that the centers coincide and are parallel to the axis of the cutting;
- the equipment is turned on and the workpiece is fed for threading;
- the finished part is checked in accordance with the ready-made template.
Cutting with three incisors
This method consists in the following:
- a blank is prepared;
- sharpening of three incisors - straight, narrow and profile;
- the installation and fixing of the prepared elements is carried out. They can be arranged both perpendicularly and parallel to the thread axis. It all depends on the angle of inclination.
A common production method
It is at the workplace that the cutting of the trapezoidal thread takes place in this way:
- the working equipment is checked and adjusted;
- thanks to the slotted cutter small depressions are made on the screw;
- with the help of a narrow slotted element, the screw is cut to a certain diameter;
- with the help of the profile slotting element, the final manufacture of the trapezoidal thread is made;
- the finished part is checked in accordance with the prepared templates.
Trapezoidal thread: dimensions
As mentioned before, this type of thread has the form of a trapezoid, in which the angle between the sides can have different values. All basic dimensions are installed in accordance with GOST.For a single-pass type, the trapezoidal thread (dimensions - GOST 9481-81) has dimensions and steps of different diameters - from 10 to 640 mm. In addition, it can be multi-threaded, as well as twisted to the left or right side. These indicators are normalized GOST 24738-81.
Where to use
For the functioning of any element, for example a machine or mechanism, it is necessary to fulfill the obligatory condition: rotational movements must be transformed into translational ones.This principle is used to manufacture various machines, devices, control systems used in the industrial field.
The advantages of threading
The effectiveness of the work on turning rotary movements into translational movements is carried out with the help of a nut and a screw. Despite the fact that these details look simple, they require care in their manufacture. It is from these parts that the performance and reliability of not only the constituent elements but also the entire working equipment depend.
Trapezoidal thread has proved itself only from the positive side. That is why it is used in various devices.
Features of multi-thread
To give the screw strength characteristics and increase its stroke, use a multi-threaded trapezoidal thread. In this case, all parameters, such as the height of the thread, its diameter - are exactly the same, with a one-way view. The only difference is the number of moves per step. For example, three-way threads have a stroke three times their pitch. All this can be seen in the pictures.
Let's give an example to make this species understandable to everyone. All use conventional caps for canning fruits and vegetables. To open them, you need to make minimum efforts. When using cylinders of large diameters to get into the grooves of one-way threads is much more difficult. That's why they use multi-pass.
This kind of thread can be determined visually, just look at the picture.It can be seen how many turns it is from the beginning of the screw. Multi-thread threads are manufactured using sophisticated technologies, and therefore cost more.
Trapezoidal connections have many positive qualities. That is why they are used in various manufacturing industries. The most common field is engineering. So, their advantages include the following:
- the ability to collect and disassemble various devices an unlimited number of times;
- a convenient process of parsing and assembling;
- reliability of threaded connection;
- easy manufacturing process;
- independent regulation of compression force;
- manufacturing of parts in various designs.
Disadvantages of connections
Negative aspects of this type of connection is not so much. One of them is the occurrence of great tension in the depressions. In addition, they can not be used in devices and mechanisms that have high vibration, since the screws can self-unscrew, which is not a good sign.Therefore, it is necessary to monitor this, and in the event of such a situation - to correct the position of the screws.
This quality, like value, can be attributed to both positive and negative sides.One-way threads are much lower than multi-way threads. Here, everyone chooses according to personal preferences. Many design organizations use multi-way threads, because they are reliable and durable.
So, we found out what kind of connection such as trapezoidal thread, its dimensions, advantages and disadvantages is.