The old-fashioned method of how to easily restore threads in aluminum

Rules for cutting threads with a tap:

1) when cutting threads in deep holes, in soft and tough metals (copper, aluminum, babbitts, etc.), the tap must be periodically unscrewed from the hole and the tap grooves must be cleared of chips;

2) thread cutting should be carried out with a full set of taps. Cutting a thread immediately with a medium tap without going through a rough tap and then a finishing one does not speed up, but, on the contrary, complicates the work, leads to poor-quality threads, and sometimes to breakage of the tap. The second and third taps are inserted into the hole without a driver and only after the tap passes correctly along the thread, the driver is applied and threading continues;

3) blind holes for threads must be made to a depth slightly greater than the length of the part being cut, so that the working part of the tap extends slightly beyond the part being cut. If there is no such reserve, the thread will be incomplete;

4) during the cutting process, it is necessary to carefully ensure that there is no misalignment of the tap; To do this, every 2-3 threads you need to check the position of the tap in relation to the upper cut plane of the product using a square. Particular care must be taken when cutting threads in small and blind holes;

5) Cooling and lubrication are used to reduce heat on the tap and produce smoother, cleaner threads. A tap without lubrication heats up quickly and can jam and strip the thread. Emulsions, drying oil or oil (boiled, linseed) are used as lubricating and cooling liquids when cutting threads in steel products; kerosene is used in aluminum products; turpentine is used in copper products;

6) thread cutting in bronze and cast iron parts can be done dry.

It has been noticed that on many Golfs the rear engine mount (or gearbox) mount is a problem area, namely the internal thread in the aluminum gearbox housing.

So I haven’t had a thread for a long time, I noticed even from the purchase that it wasn’t screwed

, but the pin at 12 is clogged)) Recently it made itself felt, unpleasant sounds appeared when starting and braking, and when I reached out to replace the pillow, the bolts simply wouldn’t screw back in.

Types of instruments

The appropriate tool is selected depending on the characteristics of the material being processed, the required productivity and other parameters. Using different types of taps, you can cut metric or inch internal threads with a cylindrical or conical profile.

According to the method of conducting the process, models are distinguished:

• Pass-through (universal) . Their working part consists of three zones. The first performs rough cutting, the second – intermediate, and the third – finishing.
• Complete . To perform a full range of work, several tools are used - for roughing, intermediate and finishing cutting. The sets consist of three taps, less often of two (for roughing and finishing). For processing particularly strong metals, kits with 5 tools are used.

The tool is made of two types: for processing holes manually or using metal-cutting equipment.

• Machine-manual . Has a square shank. Works complete with a holder with two handles - a knob.
• Machine . Installed in the chuck of metalworking machines of various types.

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).

Image gallery

Photo from

Tapping with a fixed tap

Die cutting of external threads

Manual thread cutting machine

Working side of the thread cutting die

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:

Image gallery

Photo from

Selecting the appropriate drill diameter

Processing the workpiece with a file before cutting

Tapping in several stages

Parts with external and internal threads

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

Internal threading

To cut internal threads, taps are used - tools like a screw with cutting grooves. Generally, cutting requires two taps for rough and finishing passes. The difference is in the depth of cutting the grooves. There are also three-pass taps and other cutting options. To work with them, special wrenches are required, which can be different in design, but must be suitable in size for the working tool.

Before cutting a thread, it is very important to prepare a hole of the required diameter. Otherwise, you will either break the tap (with a hole diameter less than required) or get a poor-quality thread. So, if an M10 internal thread is required, i.e. 10 mm in groove diameter, then the hole diameter should be 8.5 mm. This is determined based on the thread pitch. For M10 it is 1.5 mm and, accordingly, the required hole diameter will be 10-1.5 = 8.5 mm. Thread pitches can be found out using special formulas, although a simpler option would be not to calculate the diameter, but to find out its value from the table.

After preparing the hole, we proceed directly to considering the issue of how to properly cut the thread. We attach the tap to the holder and slowly begin to screw it into the hole, paying special attention to maintaining the accuracy of the direction. Cutting is done clockwise with the application of certain forces.

For successful cutting, the tap must be sharp and of high quality. The duration of its operation and the likelihood of breakdown depend on the use of lubricant. A few drops of oil will not only make cutting easier, but will also improve the quality of the carving. This is especially important for cutting blind holes. Naturally, it doesn’t hurt to have certain skills that come with practice. However, this operation is relatively simple and skills are acquired after 3-4 threads.

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.

What should you know about carving?

When installing shut-off valves, adapter tees or couplings on a metal pipe, a thread must be made, which is characterized by the following parameters:

• Depth
  - the distance from the base of the thread to the end of the pipe.
• The profile and its angle
  - the cross section of the coil, which is made in the form of a triangle, rectangle and other shapes. When the side edges of the coils intersect, an angle is formed.
• Pitch
  - the distance that is formed between the tops of the pipe or nearby turns.

The determination of the profile and pitch should be treated with maximum attention, since the type of thread depends on this:

• Inch
  - appears as a triangle and is used when assembling elements of a water pipe, and sometimes a heating pipe.
• Cylindrical
  is a version of an inch thread that has a smaller pitch. The smoothed top edge of the profile resembles a cylinder. An example of an external cylindrical thread diagram is presented below:
• Conical
  - the type allows you to obtain a hermetically sealed connection, which is especially important when using sealing materials.
• Metric
  - this type is used for small diameter pipes. It can be trapezoidal - the outer angle is 30 degrees, and the sides of the coil resemble a trapezoid. For bolted connections, rectangular threads can also be used, since they make the fixation more reliable. Here is a diagram of a metric thread, which looks like an equilateral triangle:

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.

External thread cutting with a die

To cut external threads, you will need the following tools and materials: a die or pipe clamp, a die holder, a file, a vice, a caliper, and machine oil.

The most widespread are round dies (lerks). They are either solid or split. The diameters of solid round dies are standardized. This allows you to choose the appropriate option from a large range of sizes, for example, M10, M12, M14, M16.

A special feature of split dies is the ability to adjust the diameter of the thread being cut within 0.1…0.25 mm. However, they have reduced rigidity, which affects the accuracy of the resulting profile.

Characteristics of metric thread

Before you begin the practical steps of thread cutting, you need to know its basic parameters and types. In the construction and renovation of housing, metric threads are used in most cases. What does it mean? According to the shape of the tooth, the thread can be metric, inch, rectangular, trapezoidal, etc.

Characteristics of metric thread

The thread we are interested in has the shape of a triangle, while the trapezoidal thread has the shape of a trapezoid. In addition, there is such a thing as a thread pitch, that is, the distance between its vertices: in the case of a metric thread, between the vertices of the thread triangle. And, of course, the characteristics of the thread include its diameter.

Let's consider the paragraph described above using the example of the M 12 thread, where the letter “M” indicates that the thread is metric, the number “12” determines the diameter of the thread. Where is the step size? The fact is that metric threads are divided into main and small, and if there is no other digital value after the number, it means the main thread. But if we have a thread M12 x 1.5 or M 12 x 1.25, then this means that the thread pitch is 1.5 and 1.25 mm, respectively. The pitch of the main thread M 12 is 1.75 mm.

Recommended drill diameters (in mm) for cutting metric threads

All these values ​​for any type of thread can be found in reference books or on the pages of the corresponding websites on the Internet. For internal threads (nuts), there is another reference value - the diameter of the thread hole, which can be found there. For our M12 bolt, the internal diameter of the nut should be 12 mm minus the height of the tooth profile, that is, according to the reference books, 10.2 mm. For small thread M 12 x1.25, the diameter will be correspondingly smaller - 10.4 mm.

It is worth noting that something similar applies to a bolt or, as it is called in reference books, a rod. Again, for an M 12 thread, the diameter of the rod should be slightly less than 11.7 mm, but for an M 12 X 1.25 thread - 11.9 mm. If you do not comply with the dimensional tolerances for the threads for both the nut and the bolt, the thread will be of poor quality, weakened on one side, and on the other, if the tolerance is larger, it will simply break.

Gutter cutting machine

A machine for cutting threads on pipes is unlikely to be needed by a person who is equipping his home. It's more of a working tool. In design, it is somewhat reminiscent of vertical drilling machines.

The diameter of the workpiece and the cutting pitch are adjustable. The operation of the spindle can be carefully debugged by adjusting the number and speed of revolutions. In principle, such a machine does almost all the work. Also, unlike manual lechers, the machine can make not only external threads, but also internal ones. More modern machines can process the smallest parts and products with thin walls.

In the following video you can clearly see how the machine works without distortions:

Threaded hole repair (restoring damaged threads)

Our company does not restore threads. This article is intended solely to introduce you to the thread restoration process. In our stores you can buy fittings (threaded inserts), drills, taps, thread restoration kits.

The information is intended for persons carrying out repairs in a personal garage and car repair shops. In accordance with this, the text is structured and recommendations are given. The use of this method in manufacturing enterprises involves the use of specific tools and devices, and other technology.