How to cut a thread with a tap: thread cutting technology, size table

Threaded connections are very widely used in mechanical engineering, so the tool for making threads is one of the most common.

Threads are distinguished:

• according to the location of the turns - external and internal;
• in the direction of the helix - right and left;
• according to the profile shape of the grooves - triangular, trapezoidal, rectangular, thrust and special;
• in the direction of the generatrix - cylindrical and conical;
• according to the size system - metric and inch.

Depending on the size of the thread, the type of production and the design of the parts, different types of thread-cutting tools are used:

• thread cutters (rod and shaped single-thread and multi-thread);
• taps (hand, machine, nut, machine, tool, master, etc.);
• round dies;
• threading heads;
• thread cutters.

Types of thread

The carving is:

• Metric
• Inch
• Pipe inch

How they differ can be seen in the picture below; the only thing worth noting is that metric threads are mainly used.

Types of thread

There is also a difference between right and left threads.

Groups and cutting options

Regarding the direction of movement of the guide, there are:

• external;
• internal;
• single-pass;
• multi-pass;
• rights;
• left.

There is a special sizing system for applying threads and determining the size of the hole for the thread. According to it, there are such thread options that are cut using taps, such as:

• Metric.
• Inch, with a different profile. The characteristic angle here is 55°, the diameter designation is shown not in millimeters, but in inches, and the number of threads determines the pitch.
• Pipe is characterized by differences in the initial diameter, based on the size of the pipe opening. Suitable for external cutting only. The dimensions of the hole for the half-inch pipe thread are determined according to the table below.

Classification of leroks

Thread cutting tools are distinguished according to the following characteristics:

1. According to the method of producing threads - machine or manual.
2. According to the materials from which this equipment is made.
3. According to the profile of the threaded part on the final product.
4. According to the characteristics of the thread being cut: its diameter and pitch.

Tools for obtaining internal threads are often called taps, but this is incorrect - such equipment is called taps.

A thread cutting tool is always used in conjunction with a die holder - equipment where the thread-forming tool is secured. The appearance of such devices is determined by the design of the lectern. In particular, for manual thread cutting, die holders are equipped with a handle and three to four gougons that secure the blade, which are evenly distributed along the arc of the seating surface. When machine-forming threaded profiles, the die holders have the form of a flat prism.

To universalize the designs of die holders, tool companies that produce die holders make their outer surface the same for the adjacent group of threads (for example, M10 and M12). The taps, designed to produce threads with the same diameter but different thread pitches, are also unified in their seats.

The standard marking of the lerka includes in its designation a letter that determines the type of thread - inch (D) or metric (M). Rarely, lugs with left-handed threads are also used (for example, in the seats of devices for tying cargo cables and ropes, in heating radiators, etc.). Then the Latin letters LH are added to the designation of lerki.

For trenches that form threads on pipes, the letter G is added to the designation. Such trenches can have a conical profile of the thread-forming part, and are used to produce threaded parts on pipes, in particular, on bends, adapters, etc.

The parameters and characteristics of domestically produced lechers are regulated by the requirements of GOST 9740.

Designation principles

To determine the main qualities, you need to understand its designation. The thread designation in the drawings is slightly different from those used by the manufacturer in the production of products. Thread tables allow you to determine the main characteristics only by designation.

The features of the marking include the following points:

1. Symbol for the thread in question G.
2. The diameter size is indicated after the letter. An example of notation is 1 ½.
3. The symbol L indicates that the turns are left-handed.
4. The next symbol H indicates the accuracy class.
5. The make-up length is represented by numbers at the end of the marking.

The drawing provides an indication of the accuracy class. A symbol indicating the accuracy class may be indicated in the technical documentation. The creation of turns is carried out in compliance with one of three classes. In addition, the letters “A” and “B” may be indicated next to the number: the first indicates an external indicator, the second internal. The first class corresponds to the coarsest threads, the third is the highest quality.

Tools for manual thread cutting

When cutting threads manually, the workpiece (rod, pipe) is stationary, and the tool itself rotates. In this case, there is no peripheral sliding speed, so the thread cutting tools practically do not heat up to high temperatures. To reduce mechanical wear of the thread-forming profile and reduce the effort, the area of ​​the workpiece required for cutting is lubricated. If there are large differences between the diameter of the original workpiece and the diameter of the thread, it is also necessary to lubricate the inner surface of the hole.

It is believed that in order to form a full-fledged threaded profile, the diameter of the initial workpiece (for the most popular diameters) must correspond to the following values:

Note : The data given in the table can also be used to determine the diameter of the initial workpiece for subsequent thread shaping on machines with flat dies.

An important element for choosing the right lecher is the material from which it is made. The peculiarity of the thread cutting process - a gradual increase in force, with a sharp decrease towards the end of the process - determines the increased viscosity of the threading material, otherwise the thread profile will intensively chip. Therefore, the optimal choice would be levers made of alloy tool steel X12F1 or 9ХС, with a hardness of 59…61HRC. For cutting threads on heat-resistant and alloy steels, a tool made of high-speed steel grades R6M5 or R9K6, with a hardness of 60...63 HRC, is suitable. The price of such blades will be high, so their use is justified only for large volumes of production of threaded parts. For domestic purposes, it is quite acceptable to use lerks made from carbon tool steels U10 or U12.

Among the enterprises that produce such tooling, the highest ratings are those of Izhevsk, Chelyabinsk, Vladivostok, Samara, Bryansk, Nizhny Novgorod (Russia), Orsha, Minsk (Belarus), and Lvov (Ukraine). Foreign-made lechers from UFC (Italy) and CM Tools (Finland) have proven themselves to be excellent in operation.

Tools for machine thread forming

Unlike hand tools, when producing threads on specialized machines, dies perform a reciprocating movement, while the workpiece moves in a screw manner. Such lechers are divided into movable, which is fixed in the slide of the machine, and stationary, installed on its table.

The working area of ​​the fixed ladders consists of three main parts:

• The intake, with the help of which the rod workpiece is captured;
• Profiling, where the thread rolling itself is carried out;
• Calibrating, in the area of ​​which the basic parameters of the thread are calibrated and the product smoothly exits the thread formation zone.

This design eliminates sharp fluctuations in force, which are inevitable due to the operating characteristics of the equipment: high productivity (up to 400 rpm) and the presence of an idle stage, when the slide with the die holder returns to its original position after the next workpiece.

The movable die has a simpler design. Its receiving part in length is approximately 30...35% of the diameter of the original workpiece, while the rise of the profile to the main level of profiling occurs at an angle of 4...7 °, At the same time, the length of the movable lever is always greater: this eliminates accidental capture of the knurled workpiece during the reverse stroke of the slide .

Machine tools can be used to cut not only ordinary types of threads, but also special profiles, for example, for grease nipple heads, as well as threads for self-tapping screws. For this purpose, a special comb is made on the form-forming part of the lerk, in the grooves of which the necessary sharpening of the end of the fastener is formed.

In order to avoid cracks during long-term use of tools for machine thread shaping, their hardness should be slightly lower than manual ones - within 56...58 HRC.

Machine lerks are usually manufactured by the same companies that produce the thread rolling equipment itself. Tools listed are Italian (from the Sima and Sacma brands), Japanese (Sakamura) and Belgian-made (Malmedie). It is better to avoid commercially available tools made in China and Taiwan: although its price is much lower, the stability of its performance characteristics and mechanical properties are highly questionable.

How is the operation performed and what is its essence?

The main task of the mechanic is to create a hole in the metal thickness with the subsequent formation of hollows from the inside. They need to be made so that the turns fit the bolt, stud or other fastener.

A threaded element may be needed in everyday life for the most durable connection of two parts. Here it is necessary to achieve maximum cleanliness - so that there are no shavings, deformations, or broken threads left. It is also very important to follow GOST standards for the size of the device. The diameter should match the screw that will go inside.

Many parameters are important - the type of material, its density, as well as condition, for example, temperature, the presence of corrosion. First you need to prepare the workpiece - remove excess dirt. Then you need to select the right tool, and only then begin metalworking in two or three stages - from roughing to finishing.

Several parameters matter:

• hole diameter;
• cutting depth;
• number of threads (these are entries, the most common is the presence of three cavities);
• pitch, that is, the distance between two furrows.

Parameters for selecting a drill for threading: table

If you need to drill a hole with a large diameter, you will need to take a special machine, where the drills are equipped with conical tails, but ordinary drills are equipped with cylindrical tails. On a large drill, the cone has a fifth size. Thus, the parameters of the cone directly depend on the diameter of the drill; the larger the diameter of the drill, the larger the cone is needed. For example:

• diameter from 6 to 10 mm;
• the required cone size is from 11 to 22 mm.

You can select the drill diameter for a particular thread as accurately as possible using a special size selection table.

If there is a need to create an internal thread, the hole diameter should be selected according to the thread diameter and thread pitch parameters. These data in the tables are designated as M8×1, where:

• M is a metric thread;
• the number is the thread pitch;
• if it is simply M8 and without numbers, then you need to use a standard large step. This parameter step is the most common and is adjusted according to standards for most drill sizes.

Diameters require selection of the appropriate hole size. The table includes a list of the most common sizes that you usually have to deal with in everyday life when performing certain jobs.

How internal threads are cut - general information

The device is called a tap. It can be of two varieties - manual and machine, in accordance with the methods of making furrows. The material that is processed is metal, but not only it. There are also lightweight models that cut into plastic or wood. The last option cannot be called the most common.

Factories use mechanized technology - metal drills make through holes (or a blind cavity), and after the blade, several turns are applied with a predetermined pitch. The advantage of this processing is high accuracy. Calculations are made using computer-aided design programs, then the data is entered into the control module - manually or using CNC. The second advantage is that skew of the spiral angle and errors are virtually impossible.

But at home and in small industries, a simpler, but less accurate procedure is often used - manually cutting internal threads with a tap. The work can be carried out on site; for this you need to buy the device itself and a drill to make a preliminary hole.

The tool resembles a herringbone shape due to the fact that the working surface is a ribbed blade. Structurally, the product is a rather complex configuration made of tool steel. This material is used because of its strength and ability to process most alloys, even cast iron. It is not very good to work only with hardened metal - it has internal stresses, therefore it is considered fragile and can crumble during the cutting process.

Hole parameters

Threads are distinguished according to the following characteristics:

1. Unit of measurement. Throughout the country, the metric system is predominantly used. Inch values ​​were used in the pipe industry.

1. Thread pitch and number of thread starts. Non-standard parameters are used in the automotive and machine tool industries.
2. Profile form. The figures differ in the type of cutting. There are elements of triangular, rectangular, trapezoidal and round shapes.
3. Direction of turns. There are right- and left-handed cuts.
4. View. External or internal.
5. Surface type. It can be cylindrical or conical.

The main condition for a high-quality connection is the correspondence of the indicators of the external and internal threads. If one of the parameters does not match, the fastening will be unreliable.

Drilling depth is one of the most important indicators. When calculating, the following factors must be taken into account:

• screw-in depth of the threaded element;
• the size of the external thread;
• presence and chamfer parameters.

To calculate the screw depth, the type of material being processed must be taken into account. For steel, titanium, bronze and brass no corrections are needed, but for gray and ductile cast iron a multiplying factor of 1.25 is used. For light alloys this figure is even higher - it is doubled.

Types and areas of application of taps

According to the drive method, they are divided into:

• Manual - they have a square tail, which is inserted into the knob. There are two handles that make it convenient to turn the product. It is important not to allow distortion. This result can only be corrected by drilling and cutting a larger diameter.
• Machine - used on metal-cutting machines. They are firmly fixed in the holder, accurate, and do not allow deviations.

By cutting method:

• Universal. Their design can be called classic. A tool with a running gear (its length determines the depth of insertion of the screw later if the hole is not through), which is divided into sections. Each of them has certain geometric parameters - angle, direction, distance, step. There are usually three of them, each designed for rough metalworking, intermediate and finishing. Thus, you can achieve the most accurate result with one movement.
• Complete. The name speaks for itself. You will need a set of 3 taps, since the internal thread must be made with high precision. First, the coarsest tool is used, then a finer one, and finally - with grinding and sharpening of the smallest corners. Buying a set is more expensive, but the result is much higher quality.

By hole type:

• For through. They are distinguished by a long working part. It gradually expands, moving into the working area, which is responsible for precise cutting.
• For the deaf. On the cutting section, calibrating turns immediately begin. Therefore, it is very important to sharpen them or promptly change the set as they wear out.

According to the groove design:

• straight – I work well with soft alloys;
• screw, their working area is staggered, they can easily pass even through cast iron;
• shortened - removes chips well.

The shape of the product resembles a cone (full or truncated) or a cylinder. They also all differ in diameter.

How to correctly determine the hole diameter?

Before cutting a thread, a hole is made, the diameter of which is determined according to standardized tables. If you prepare a hole whose cross-section is smaller than the recommended size, the tool will fail; if it is larger, the result will be of poor quality.

Correspondence table for metric threads and hole diameters for them

Correspondence table for inch threads and hole diameters for them

Selecting drill size

The diameter of the drill for a hole for a metric thread is also determined by formula (2), taking into account its main parameters.

It is worth noting that when cutting in ductile materials, such as steel or brass, the turns increase, so it is necessary to choose a larger drill diameter for the thread than for brittle materials, such as cast iron or bronze.

In practice, drill sizes are usually slightly smaller than the required hole. Thus, Table 2 shows the ratio of the nominal and outer thread diameters, the pitch, the diameters of the hole and the drill for cutting metric threads.

Table 2. The relationship between the main parameters of metric threads with normal pitch and the diameters of the hole and drill

As can be seen from the table, there is a certain dimensional limit, which is calculated taking into account thread tolerances.

The size of the drill is much smaller than the hole. So, for example, for an M6 thread, the outer diameter of which is 5.88 mm, and its largest hole value should not exceed 5.153 mm, you should use a 5 mm drill.

A hole for an M8 thread with an outer diameter of 7.87 mm will be only 6.912 mm, which means the drill for it will be 6.8 mm.

The quality of the thread depends on many factors when cutting it: from the choice of tool to the correctly calculated and prepared hole. Too little will lead to increased roughness and even breakage of the tap. Large forces applied to the tap contribute to non-compliance with tolerances and, as a result, dimensions are not maintained.

Stages of thread cutting with a machine-hand tap

Work order:

• The first step is marking in accordance with the drawings.
• According to the marks, punching is carried out with a sharply sharpened core.
• Drill with medium pressure at low speeds. The drill should be at right angles to the surface. Before starting work, the drill is lubricated. If the hole depth is large, then lubrication is carried out not only before starting, but also during operation. The depth of the blind hole should be slightly greater than the length being cut. If there is no reserve, the thread may be incomplete.
• The quality of the result can be improved by countersink processing, which reduces the taper and ensures parallelism of the side surfaces.
• The tap is secured in the driver, its tip is lubricated and inserted into the hole strictly at right angles to the surface. Make the first turn, lightly pressing the knob from above. After the first turn forward, make a half turn back to remove chips. Particular care is taken when using a multi-tool - it is fragile and easy to damage. It's easier to work with complete models.

Preparatory procedures

The beginning of any work is the choice of material and tools. The workpiece must have a hole. Those produced by casting or stamping are the worst to undergo transformation. It is better if pressure or melting was applied. But in any case, the most suitable conditions are created during fresh metalworking using drilling or countersinking.

The drill and its cross-section are selected in accordance with the required result according to the regulatory document - GOST 19257 - 73. This is a Russian standard, but it complies with international standards. It must be new or well sharpened. It is important to secure it tightly in the working tool (or in the machine chuck) so that there is no beating or wobbling.

How to cut external threads using a die

To cut external threads manually, a special tool is used - a die holder with dies of various diameters.

Die holder with dies for different diameters

In hard-to-reach places, for example near walls, a die holder with a ratchet is used.

Selection of dies

Nominal thread diameter is the diameter at the vertices of the thread triangles. The die cuts the metal, forming depressions and leaving the tops intact, thus both the rod and the die must be the same diameter. The diameter of the thread, for example, is M3 - this is “M” - metric thread, and the number is the nominal diameter of the thread in mm. Accordingly, to cut a thread on a 3 mm rod, we take an M3 die. Measurements of the rod are made with a caliper.

To make the die cut better into the rod, a chamfer is cut off from its end.

Principle of thread cutting with a die

To secure the workpiece you will need a vice. The workpiece is firmly fixed in a vice and lubricated with machine oil for easier movement of the die, reducing friction and tool wear.

When cutting threads with a die, you must avoid large accumulations of chips in the chip removal holes.

The die is installed on the end of the part perpendicularly. With slight pressure, they begin to rotate the die holder clockwise if the thread is right-handed, respectively, if it is left-handed, then counterclockwise.

Cut the thread as follows:

1. First make 2-3 turns.
2. Then half a turn back to remove chips.
3. Lubricate after every 3-4 turns, using a syringe.
4. Etc.

Ring gauge

Cutting a thread with a die with your own hands (video)

DIY thread cutting on a metal pipe

When installing metal pipes for water supply or heating, they have to be threaded. The threaded connection of pipes is quite reliable and can withstand significant pressure (if done correctly), so let's look at how to cut threads on metal. pipe with your own hands.

First of all, we cut off the required section using a grinder or a hacksaw, making sure to control the evenness of the cut so that one part of the pipe is not larger than the other - the cut must be perpendicular to the walls of the pipe.

The pipe must be cleaned of rust, old paint, etc., if there is anything on it. Next, we cut a chamfer from the pipe (internal or external, depending on what thread you are cutting) for easier movement of the cutting tool. The chamfer can be cut with a grinder with a metal disc (→ how to work with a grinder) or with a flap disk or file.

Beveled metal pipes

Cutting external threads on a pipe using a die (die)

Everything is the same as with the rods described above, but now with a larger diameter, which most likely will require some practice and you should practice or be extremely careful the first time. Also, to obtain high-quality threads and subsequent good pipe connections, you need to work first with a rough die, then with a finishing die (such kits are sold).

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The choice of die metal is also important. To work with hard alloys, you should use the appropriate dies made of certain alloys; please check this when purchasing.

But, a die is not such a good and powerful tool for cutting threads on pipes with your own hands; it is much more convenient to use clamps.

The die holder is practically the same die holder, only with a guide for smooth movement and thread cutting. The clamp is placed on the pipe of this particular guide.

We put on and attach the clamp to the pipe, screwing it in a little by hand, then you need to use either a special tool - a ratchet, which is convenient for twisting the clamp, but for household needs a large adjustable wrench or gas wrench is also suitable.

One part of the pipe must, of course, be fixed in a vice. If the pipe is cut locally, then make sure that it is not torn out somewhere due to the force applied to the clamp. The pipe can be fixed using a second gas wrench, but it is better for a second person to do this, because cutting threads with one hand is problematic.

What is a clamp and how to use it (video)

Cutting internal threads on a pipe with a tap

Sometimes you have to cut into meth. pipes and internal threads. This is done in the same way using a tap, only with a larger diameter.

To cut a good thread, you should use at least 2 taps - roughing and finishing. It is important to select the correct tap for the pipe diameter. So, the internal diameter of the pipe should be larger by the length of the tap turn (more precisely, by the thickness of the cut), this is indicated on the tap itself.

Cutting is done first with one tap, then with a second.
The main thing is to strictly observe the perpendicularity of the tap stroke and control it. That's all, good luck with your threading! Leave your tips and comments below. Subscribe to our newsletter. Good luck to you and good luck to your family!

Features of the technology

When cutting internal threads with a tap, the following algorithm is used.

• In the place on the surface of the workpiece where the hole for threading will be drilled, it is necessary to form a recess for a more accurate entry of the drill, using a core and a regular hammer. The drill is fixed in the chuck of an electric drill or drilling machine, on which low rotation speeds of the tool are set. Before starting drilling, the cutting part of the drill must be treated with a lubricating compound: a lubricated tool enters more easily into the structure of the material being processed and creates less friction in the processing area. You can lubricate the drill with a piece of ordinary lard or grease, and when processing viscous materials, machine oil is used for these purposes.
• If it is necessary to cut threads in small parts, they should first be fixed using a bench vice. When starting drilling, the tool fixed in the equipment chuck must be positioned strictly perpendicular to the surface of the workpiece. You should lubricate the tap regularly and ensure that it does not warp and moves strictly in the given direction.
• At the entrance to the hole, as mentioned above, it is necessary to remove the chamfer, the depth of which should be 0.5–1 mm (depending on the diameter of the hole). For this purpose, you can use a larger diameter drill or countersink, installing them in the chuck of drilling equipment.
• The process of cutting internal threads begins with tap No. 1, which is the first to be installed in the driver. We should not forget about the lubricant, which must be applied to the tap for threading. The position of the tap relative to the hole being machined must be set at the very beginning of the work, since later, when the tool is already inside the hole, this will not be possible. When cutting a thread with a tap, you must adhere to the following rule: 2 turns of the tap are made in the direction of cutting the thread, 1 - against the direction. When the tap makes one revolution back, chips are thrown off its cutting part and the load on it is reduced. Thread cutting with a die is performed using a similar technique.
• After cutting the thread with tap No. 1, tool No. 2 is installed in the driver, and after it – No. 3. They are processed according to the method described above. When cutting threads with taps and dies, you need to feel when the tool begins to rotate with force. As soon as such a moment occurs, you should turn the knob in the opposite direction to throw the chips off the cutting part of the tool.

The harder the material being processed, the more abundantly the tap must be lubricated during the thread cutting process.

Before making internal threads with a tap or cutting threads with a die on external surfaces, you should thoroughly study these procedures and strictly follow the rules for their implementation. Only in this case can you count on the result satisfying you with its quality and accuracy.

Adaptations

To apply carvings with your own hands, use small devices:

• dies (they are also called dies) for applying turns from the outside (usually onto a pipe or metal rod (pin);
• taps - for internal ones (you first need to make a hole for them).

All these devices are made of alloys characterized by increased strength and abrasion resistance. Grooves and grooves are applied to their surfaces, with the help of which their mirror image is obtained on the workpiece.

Any tap or die is marked - they have an inscription indicating the type of thread that this device cuts - diameter and pitch. They are inserted into holders - collars and die holders - and secured there with screws. Having clamped the thread cutting device in the holder, it is put on/inserted into the place where you want to make a detachable connection. By turning the device, turns are formed. How correctly the device is positioned at the beginning of work determines whether the turns will “lay down” evenly. Therefore, make the first revolutions, trying to keep the structure level, avoiding shifts and distortions. After a few turns, the process will become easier.

You can cut small or medium diameter threads by hand. Complex types (two- and three-way) or working with large diameters by hand are impossible - too much effort is required. For these purposes, special mechanized equipment is used - lathes with taps and dies attached to them.

Basic cutting methods

You can cut threads on pipes in one of two ways:

• automatic - on machines, power tools;
• manually - using hand tools.

For living conditions, of course, manual technology is more relevant. Cutting threads on water pipes or other pipes by hand is often done using a die.

Solid dies for pipe threads, made of strong alloy steel, are available with a body diameter of up to 65 mm. Dies with a body diameter of up to 120 mm are available for metric threads. On the body of metric products there is a symbol “M”

A die is a simple device for cutting threads on pipes at home. The same tool is successfully used on industrial machines.

The device looks like a disk with several axial holes drilled along its inner diameter. The edges of these holes form several incisors (usually 8-10). The material for the dies is alloy steel or other hard alloys.

There are several types of such devices:

• solid;
• spring-loaded (split);
• clamp (sliding).

According to the design, the die is produced in the form of a circle, square, hexagon, or prism. The most common are disc (round) instruments. They are used for threading water pipes up to a diameter of 36 mm.

For ease of working with dies, use:

• simple knobs with locking screws - hand tools;
• threading chucks on lathes.

Cutting threads (metric, conical) of the best quality on pipes manually or on machines is provided by solid dies.

However, this type of tool, due to the rigidity of its own design, has its negative sides. The cutters wear out quickly.

A spring-loaded thread cutting tool is distinguished by the presence of a cut in the area of ​​one of the axial holes. The presence of a cut reduces the load on the cutters, but at the same time the degree of rigidity required to achieve high cutting quality is reduced.

Spring-loaded (split) dies have a less rigid design, which makes it possible to cut threads on pipes and at the same time change the thread diameter in the range of 0.1-0.3 mm.

Such devices are characterized by increased wear resistance of the cutters, but do not provide high accuracy and cleanliness of thread cutting.

Sliding dies consist of two working parts. They are designed for installation in a fastening module - a clamp.

Fastening in the clamp is carried out by a mechanism consisting of a cracker and an adjusting screw. The screw adjusts the diameter size for thread cutting. Usually the die is equipped with a set of dies for several different diameters.

Method #1 - making pipe threads with dies

The process of creating a thread on a pipe with a die or die requires the mechanic to perform some preliminary actions:

1. The surface of the pipe in the cutting area must be thoroughly cleaned.
2. The end part of the pipe should be processed with a file (make an entrance chamfer).
3. Apply lubricant to the surface to be treated to reduce resistance.

If possible, it is advisable to secure the pipe vertically, for example, in a bench vice, leaving free access to the upper part - the cutting area. The fastening force must be correctly calculated so as not to deform the pipe body.

Then take a pre-prepared driver with a roughing die (No. 1) of the required diameter and suitable thread characteristics.

An example of cutting a thread on a water pipe using a hand wrench. A die is inserted into the working cylinder of the driver and secured with two (four) bolts located opposite each other

The tool is held horizontally - perpendicular to the end area of ​​the pipe. Place the roughing die onto the chamfer of the edge using the internal hole. Light pressure and successive short turns of 25-30° make the initial cut.

This work should be done carefully, slowly, constantly monitoring the right angle between the horizon of the ram and the vertical of the pipe.

Using this technique, the first two or three threads are carefully cut. Usually, after cutting the first two or three threads, the tool is firmly in its working position. Further, the right angle can no longer be controlled.

But the technology of cutting with short (without particularly strong traction) circular movements should be maintained until the end of the cut. It is recommended to periodically add lubricant at the cutting point.

After the first pass, twist the device and then repeat one or two more times with a finishing die (No. 2).

Method #2 - clump cutting technique

The die is a variation of the same die for cutting threads, including on pipes. A distinctive feature of the die is the ability to adjust the cutters.

A set of clamps for different sizes of pipe threads. Each of these devices is equipped with screws for fastening blocks with cutters. These screws can additionally change the thread diameter within small limits

There are clamps for manual use, as well as similar devices with an electric drive.

Option #1 - cutting with a hand clamp . Manual cutting of pipes is usually done with a clamp, which is installed in a ratchet holder. This holder makes the work of cutting pipe threads convenient and less complicated.

Of course, depending on the conditions of plumbing work, you can use other types of hand holders. For example, a standard locking knob with two handles.

The principle of creating a thread with a die is almost the same as the method of working with traditional dies:

1. Clean the working surface of the pipe and make sure there are no defects.
2. Sand the cut area until it has a distinct metallic sheen.
3. Process the outer working part of the end edge at an angle of 45-60º (chamfer).
4. Lubricate the prepared surface with technical petroleum jelly.
5. Secure the pipe in a mechanical vice or hold it with a gas wrench.

After these procedures, the cutting tool (blank) is placed with the internal hole on the pipe chamfer and, with moderate, uniform pressure, they begin to rotate it with short reciprocating movements.

A convenient tool for working with a clamp is the so-called “ratchet” - a lever with idle reverse. Using such a hand tool, it is easy to cut threads on a pipe under different installation or repair conditions.

If a ratchet clamp is used as a holder, only forward cutting is carried out. It should be noted that the ratchet clamp is convenient to use when working in cramped conditions.

For example, when it is necessary to process a pipe laid in close proximity to a wall.

Option #2 - cutting with an electric clamp . Along with hand tools, electrically driven devices are widely used. The obvious advantage for the mechanic is a significant reduction in labor intensity.

But on the other hand, not all electric machines are capable of performing work in cramped conditions. In addition, when working with hand tools, it is possible to obtain a better result.

To obtain a similar result from electrical sockets, extensive experience with this tool is required.

Equipment for the clamp, supplemented with an electric drive. A modern, effective tool that significantly reduces the physical load of a mechanic. True, electric sockets are more often used in the professional sphere than in everyday life

Working with an electric clamp:

1. Preparation of the pipe surface in the cutting area - cleaning, chamfering, lubrication.
2. Fastening the pipe with devices capable of providing rigid fixation.
3. Fixation at the starting point of the die holder with the clamp included in the kit.
4. Checking the stroke and direction of rotation of the die.
5. Cutting the first two or three turns in the jog mode.

Next, pipe threads are cut automatically. The cutting length is considered optimal when the upper edge of the die cutting heads reaches the leading edge of the pipe.

At this point, the operation of the device is stopped, the reverse rotation function is turned on, and the bug is twisted from the pipe with a push feed. Be sure to periodically moisten the cut area with oil throughout the process.

Method #3 - using lathes

Large-scale construction and repair work, as a rule, excludes the use of hand tools. Here, lathes are usually used to process the pipes accordingly.

Threading functions are supported by many universal lathes.

Lathes are used to produce threaded parts on pipes of different diameters. You can make threads of any configuration on a lathe

Using the machines, both internal and external pipe threads are made efficiently and easily. The pneumatic (or mechanical) fastening module of the lathe ensures high-quality reliable fastening of the pipe and precise supply of the workpiece to the cutter.

To perform thread-cutting functions, different types of cutters are used:

• rod,
• lamellar,
• intercalary

Work on lathes is carried out by specialists trained in this field and having the appropriate qualifications. Without experience and professional skills, trying to cut threads with your own hands on a machine is not recommended.

For home craftsmen who decide to take up plumbing and carve metal workpieces, the following tips will help them in their work:

How to cut threads

Thread cutting is quite simple, but requires special care when working and a precise sequence of actions. The choice of cutting method will determine the list of tools used and the features of preparing the part for processing.

You will need a technical reference book with data on the sizes of the tools used. The thread pitch can be found on the tap used.

Preparing for thread cutting

Cut the thread only after completing the preparatory work:

• in the directory they look for the necessary information on the diameters of cutting tools for further selection;
• collect the tools needed for work;
• use a core to mark the location of the hole for the internal thread, then drill it with a drill;
• for external cutting, prepare a workpiece of the required diameter on a milling machine and cut a chamfer;
• clean the surface of the workpiece from dirt and oil stains, then apply lubricant to it and the tool.

Thread cutting tool

Work order

Only after the preparatory work should you start processing the workpiece, since otherwise it will not be possible to cut the thread correctly. Step by step cutting is done like this:

1. It is necessary to firmly fix the workpiece in a vice to prevent rotational or translational movements deviating from the original position.
2. Depending on the type of thread, chamfer (external) or drill a through or blind hole using a drill. Drills with sharpening angles are used, depending on the hardness of the material, but not more than 1400.
3. The hole needs to be chamfered with a countersink. The depth should be in the range of 0.5-1 mm, selected based on the dimensions of the part and the thread diameter.
4. Cutting is performed with a tap or die. The cutting part must be lubricated.
5. Cleaning the surface from chips using brushes.

When cutting, you need to sequentially use tools numbered 1 to 3, included in the kit. To increase the speed of work, it is not allowed to use large numbers without using the previous ones. The last number is used to form the finishing turns, without which the screw may jam when screwed in.

Cutting process

Before you start cutting, you should use drills to make a hole in the workpiece. The diameter of the drill hole must match the internal thread size. When the size of the hole made with drills is chosen incorrectly, the tool can break or the grooves will turn out to be of poor quality.

For example, when cutting M5 (groove diameter is 5 mm), you should choose a drill for a 4.2 mm hole. To cut M4, the diameter of the drill must be 3.3 millimeters, and before working with an M6 tap, a hole is first made with a 5 mm drill. This indicator is calculated taking into account the thread pitch. The pitch can be calculated mathematically, but in practice they resort to correspondence tables, where for an M5 tap the pitch is 0.8, for M4 this figure is 0.7, for M6 - 1. We subtract the pitch index from the diameter and get the required diameter of the drill. When working with brittle metals, such as cast iron, the drill diameter should be reduced by 0.1 mm compared to the size recommended in the table.

The formula for calculating the hole diameter when working with three-pass taps:

Up=Dm * 0.8;

here: Dm is the diameter of the tap.

Table 1. Correspondence between thread diameters and preparation hole

Before starting work, the tap is inserted into a square shank - a knob. The collars can be regular or ratchet. The carving is carried out carefully, the first pass is made with a tap No. 1 to the end

Particular attention must be paid to the direction of movement: only clockwise, and some effort must be applied. It is done like this: 12 turns along the stroke alternate with 14 turns against the screw stroke to destroy the chips

Table 2. Hole diameters for inch threads