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

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.

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.

Preparatory stage

To ensure that the work of obtaining threads does not cause many difficulties, careful preparation should be made for such a technological operation. All methods used related to cutting internal threads assume that a hole of the required diameter has already been obtained in advance. You can obtain the standard thread size when creating a hole according to the correspondence table. For example, for an M10 thread, a hole with a diameter of 8.5 mm is created.

There is often a situation where it is necessary to obtain a thread of a non-standard size. In this case, the required hole diameter is calculated using a universal formula. Calculations are carried out as follows:

The required hole diameter when using an M5X0.75 tap can be determined as follows: 5−0.75=5.25 mm.
The easiest way to carry out the work is when you need to get a standard thread, since all the necessary information can be taken from various tables of regulatory documentation.

To get a quality hole, you need to choose the right drill. When drilling, it is recommended to use equipment that prevents runout during operation. When choosing a drill, it is worth remembering that it must have high-quality sharpening. Experts recommend selecting the sharpening angle depending on the hardness of the material being processed. As the hardness increases, the recommended sharpening angle also increases, but it should not exceed 140 degrees.

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.

Existing threading options

Pipe threads are divided into five types, but the most popular options are conical and cylindrical. Household members often encounter such types of pipe threads. There are two methods for threading a water pipe:

• Automatic, which involves cutting threads on water supply pipes using special machines and power tools.
• Manual. For this, special hand tools are used.

If, as part of his job, a person needs to cut threads on a large number of pipes, then it is appropriate to purchase a special power tool, which will facilitate manual labor.

When the need to obtain a threaded connection is an isolated case, then manual technology is suitable for such purposes. On water pipelines, as well as pipes of heating systems, thread cutting is performed using a die.

The die is a steel disk, and its inner diameter has axial holes in different numbers, which depends on the size of the product. The edges of these holes form cutters, with the help of which thread cutting is performed. To ensure the reliability of such a tool, it is made of alloy steel or hard alloys.

Dies can have different shapes (round, square, hexagonal or prismatic), but most often disc options are used. Disc dies are intended for making threaded connections on water pipes. To make it convenient to work with the die, they are equipped with additional knobs, as well as clamps in the form of screws. Dies are also solid, split and sliding.

Solid dies for threading pipes have one significant drawback - rapid wear of the cutters. This is due to the rigidity of the product’s own design. Split or spring-loaded dies have a less rigid design, which significantly increases the service life of the product. Due to the spring-loaded mechanism, such a tool for cutting threads on pipes allows you to vary the diameter of the resulting threaded connections in the range from 0.1 to 0.3 mm. A device of this type is highly resistant to cutter wear, but is not capable of providing high accuracy.

Sliding dies are 2 working parts intended for installation in a mounting module. A die with a special fastening module forms a tool called a pipe clamp. The die is fixed in the die using a cracker and an adjusting screw. It is with the help of the adjusting screw that the thread diameter is adjusted.

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.

Video description

This video shows how to cut an internal thread using a machine and a tap:
Tapping with an electric die is similar to the conventional process, but this tool requires more space and additional fixation to operate. Its advantage is that the labor intensity of the process for the mechanic is reduced. For any type of cutting, it is recommended to add lubricant during operation to the places where the cutting edge is located.

Thread cutting can also be done using a lathe. This type of work is most often used for large volumes of production. Using such a device, you can make both external and internal threads, but you need a trained specialist to work with them. Without proper knowledge, operating the machine can cause injury.

Example of plumbing fittings with thread Source static-eu.insales.ru

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.

What is a tap? Design types and how to use them

The difference between die taps and nut taps is that the former has a large intake cone and its purpose is to cut threads in one pass in the dies. Well, the last type, the master type, is usually used to clean the threads in dies after it has been cut with a die tap, and for a similar process with threads in working dies. The grooves of the master taps are made with a spiral to the right.

Fluteless swords differ from conventional machine tools, as the name implies, by the complete absence of longitudinal grooves, and the receiving cone on them is much shorter. At the tip of the threaded part there is a pair of small grooves, with the axis inclined towards the center of the tool. Grooveless taps are an order of magnitude stronger than others, rarely break, and do not produce defects. Since they have a longer thread, they can be re-sharpened many times, so they have a longer service life.

The main advantage of fluteless taps is undoubtedly their high productivity during thread cutting, especially considering their use in through and blind holes, and not just in one. Combined taps are represented by two parts and a neck separating them, and they are divided into grooveless, two-stage and drill-tapping taps. Using them saves a lot of time, because here you need to use only one tool, and not a whole set.

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.

What is a thread and why is it needed?

Threading is one of the most popular types of fastening parts or mounting structures. It is used to connect several parts, such as pipes, into one structure. To do this, grooves are cut out on their side or inner part, which have a certain shape, angle of inclination and distance between the recesses (turn pitch).

Also, the notch can be on connecting parts, for example, taps or tees. Using this installation method, you can make collapsible or permanent structures, such as water supply, sewerage and other types of pipe systems. You can cut threads only on round or conical parts, since for other surfaces it will be inconvenient and impractical.

The most common thread profile option is triangular. It is very simple and affordable, but is not suitable for frequent system disassembly. If you need to frequently disconnect pipes or other parts, a round profile is used. It is most often used in plumbing. Other types of profiles are used in kinematic systems (for example, transmissions), but are not used in plumbing.

A type of kinematic cutting Source findpatent.ru

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.

Video description

This video shows how to make inch cutting with a die and die:

• Conical (R) - designated as BSPT and also has British roots. It has a pitch and profile angle similar to cylindrical threads. It is used for cutting notches into cone-shaped parts. In some cases, it is possible to connect parts with R and G notches. By creating additional tension on the turns during the joining process, the conical notch provides additional reliability of the docking units.
• Round (R) is a very rare type of pipe connection, which is used in places where it is necessary to frequently assemble and disassemble the joint. Even after frequent dismantling, such a mount does not lose its shape, reliability and tightness. The disadvantage of such a thread is that it cannot be combined with other types of notches. The round variety has a profile in the form of a circular arc with an angle of 30°.

There is an American standard for conical and cylindrical parts, which is labeled NPSM or NPTF. It has an angle not of 55°, but of 60°, similar to the metric one. This type of thread has its own thread size and profile height, but is found almost nowhere, since it is being replaced on the market by the British standard.

Example of American NPSM Source www.staniosind.com

See also: Catalog of companies that specialize in the installation of utilities: water supply, sewerage and heating

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

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.

Useful tips

• In order to correctly cut threads in metals with low hardness and high viscosity, such as aluminum, alloys based on it, copper, babbitt, it is recommended to periodically remove the tap to clean the channels from adhering chips.
• When using complete models, the complete set should be used. Skipping the roughing tool does not speed up, but slows down cutting. Such a violation of technology leads to a decrease in the quality of the result, and sometimes to failure of the tap.
• To prevent the tap from skewing, check the verticality of its position after 2-3 threads using a square. This precaution is especially important for blind and small holes.

The process must be carried out using liquids intended for lubrication and cooling:

• emulsions, linseed oil, and drying oil are used in steel elements;
• in products made of aluminum and its alloys - kerosene;
• when processing copper - turpentine.

It is possible to cut threads in parts made of cast iron or bronze without the use of lubricant.

Source: metallz.ru

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).

I recommend: Basics of metalworking at home: making a clamp and crowbar-nail puller with your own hands

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.

Tool selection

Let us note in advance that threads can be cut You can work either manually or by machine. In the first case, as we noted above, you need to have a set of tools with you for creating threads, in the second, the work is carried out on a lathe.

Manual threading is recommended if your task is to machine only a few parts. For example, when assembling plumbing equipment, creating household pipelines, etc.

Processing parts on a lathe involves performing large-scale tasks. A person with experience with this type of equipment is able to cut threads on an industrial scale, up to a hundred parts per hour, and sometimes more. However, you are unlikely to need such performance.

Most often, a set of hand tools covers all the household needs of home craftsmen. With their help, you will also be able to cut threads correctly and efficiently, but it will only take more time and effort.

The set of equipment mentioned above is mainly represented by taps and dies, as well as various additional parts.

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:

instrument classification and basic recommendations

A variety of tools can be used for cutting threads, among which we highlight a tap. It is used to create a threaded surface designed to accommodate a screw, stud, bolt, or other fastener. Relatively low cost and ease of use determined the widespread use of the hand tool in question. Let's take a closer look at how to properly cut a thread with a tap at home.

Depending on the method of driving them into rotation, they can be divided into machine or machine-hand taps. A special feature of the machine-manual variety of the tool is the presence of a square shank, which is suitable for a holder with two handles. Thanks to such a holder, you can rotate the tool and cut threads. As for the machine variety of the tool in question, it is installed in the chuck of various machines and can have a shank of various shapes and sizes.

• There are universal and complete taps based on characteristics related to the specific application. The universal version has a working part, which is divided into several sections. They differ from each other in geometric shape, the first is intended for roughing, the second and subsequent ones are for bringing the surface to a suitable state. The complete version is designed for the phased use of several taps. As a rule, a set for cutting threads in ordinary metal is represented by three tools, and for processing hard alloys - five.
• Taps are classified based on the type of hole being machined: blind or through. To work with through holes, a tool with an elongated conical tip is used, which is a continuation of the working part. Universal taps often have this type of shape. If you need to cut a thread in a blind hole, then use a tool that has a cut tip resembling a milling cutter. Due to this shape, it is possible to cut threads along the entire length of the hole.

As a rule, high-quality tool steel is used in the manufacture of tools. It can withstand long-term use and does not heat up during operation. A high quality tap has a strict geometric shape and looks neat. A similar tool is often used for cutting metric threads, but there are versions for producing inch threads. The shape of the base can be cylindrical or conical.

Tapping threads by hand

Thread cutting with a tap occurs as follows. The part to be threaded is secured in a vice or other device. The main thing is that the part is securely fixed in the device, since when cutting a thread with a tap you will need to apply a lot of force.

Then a hole is drilled in the part for threading with a tap, depending on the type of thread - blind or through. The diameter of the hole being drilled should be slightly smaller than the diameter of the cutting elements of the tap.

Be sure to chamfer the top edge of the hole for cutting threads with a tap. After this, the tap and installed in the drilled hole, which should be located in the vice with the chamfer facing up.

Threading with a tap is done clockwise, all the time pressing the tap into the hole. The tap must be pressed in smoothly, without unnecessary jerks, gradually turning it until a clean and even thread is obtained.

READ Thread the carbine barrel

Having made several turns with the tap clockwise, it is returned in the opposite direction, thereby getting rid of the accumulated metal shavings.

During thread cutting, it is necessary to cool the tap in a timely manner, otherwise the tool can easily be damaged. If an aluminum thread , then the tap is cooled with kerosene; if a thread on a copper part, then with turpentine; when cutting a steel thread, it is best the tap

Thread cutting order

Before cutting, it is necessary to chamfer the outer part of the pipe or workpiece at an angle of 45°. This is necessary to facilitate the first turns and fix the die.

• Secure the pipe or workpiece in a strictly vertical position. The best option to avoid distortions is a bench vise, but you can also use a gas wrench.
• Lubricate the tool with oil.
• Place the die on the head of the rod in a strictly horizontal position and start with the first few circles.
• If there is obvious misalignment in the first laps, remove the die, tap the workpiece and start again.
• When rotating on the first turns, simultaneously press evenly on the handles of the driver to begin the cutting process.
• After the first few turns, check that the thread is cut correctly. This can be done by checking the horizontality of the dies and the knob, which can be checked with a level. Next, with the correct position of the tool, you can continue cutting the pipe thread with a die to the entire required length.
• When approximately the middle of the length is reached, the pressing force can be weakened, then the self-tightening process begins.
• After one or two turns, it is necessary to turn the die half a turn back to remove chips.
• After cutting to the desired length, simply return the tool back along the finished thread.

It is necessary to take into account that the die can have several numbers, most often 2. In this case, after cutting the rough thread, it is necessary to go through each of the numbers in turn to finally form the thread profile.

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.

How to restore a thread with a tap while maintaining its diameter and location

If you need to restore the thread while maintaining its diameter, use one of the following methods.

Welding the hole and then cutting a new thread

This method is rarely used due to the fact that the strength of the new thread obtained using this technology will be lower. This method is also chosen in the absence of special devices (screws and spiral inserts).

This method of thread restoration includes the following steps.

Removing old threads by drilling.

Welding the hole. The choice of technologies depends on the materials of the parts.

To weld holes in steel products, electric arc or gas welding is used in protective environments.

When working with cast iron parts, gas or electric arc welding is used in a cold state or with general/local heating.

Electrodes (MNCh-1, OZCh-1, TsCh-1), cast iron rods with a high silicon content and other materials are used as additives.

Machining the hole flush with the base metal.

Cutting a new thread.

Note! When working with aluminum products, this method of thread restoration is usually not used. This is due to the fact that the metal actively absorbs gases during welding. Pores form in the deposited layers. With severe shrinkage, cracks appear.

Restoring threads using a screwdriver

Screwdrivers are special cylindrical devices that have threads of the required diameter and pitch on the inside and large threads on the outside. Such products are made from steel, brass, bronze, copper and other materials. At the final stages of production, the screws are hardened and further strengthened.

Photo No. 2: screwdriver for thread restoration

If you need to restore the thread while maintaining the diameter using a screwdriver, proceed as follows.

Drill out the hole. The drill must be selected in such a way that the diameter of the resulting hole allows cutting a thread for screwing in the screw.

Cut the thread with a tap. Follow the rules listed above.

Screw in the screwdriver. It needs to be installed flush. If this is not possible, mill the part and remove the protruding part of the fixture.

At the border of the new thread and the screw, apply notches using a core. This will prevent the device from unscrewing spontaneously.

Repairing threads using a spiral insert

Spiral (also called wire and spring) inserts are also often used to restore damaged threads.

Photo No. 3: spiral inserts for thread restoration

These devices have high-precision rhombic threaded profiles on the inside. Almost all models are equipped with special driving tongues designed for screwing in devices.

For the manufacture of such products, especially durable high-quality stainless steel is used. This guarantees the resistance of the restored thread to deformation and corrosion.