How to cut internal threads

How to cut a left-hand thread with a tap

It can be difficult to find the right fastener or part to replace a worn item when servicing and repairing equipment or a vehicle.

Let's give a simple example from practice: a Soviet-made chain saw requires a nut with a left-hand thread; it is impossible to get an original spare part, because such equipment is no longer produced. You will have to go around more than one store to find a nut of the appropriate size with a left-hand thread.

But there is an easier way out - take a nut with a hole diameter smaller than required, even with a right-hand thread, which is much easier to find, and use a hand tap to make the necessary threads in it.

The tap is a metal rod with cutting edges notched at the end. It is made from high speed steel or carbide metal alloys and is typically heat treated to make it strong enough to cut grooves into the metal base when screwed into place.

Using a tap is a quick and convenient way to cut threads. With this tool you can make carvings both in individual parts and in parts that are part of the product without removing them. To get exactly the thread that is required for the fastening connection, you need to choose the right type of tap.

The following information will be useful to you.

What types of taps are there?

As is known, in the mechanisms of machines, equipment, and technology there are various threaded connections, and they differ not only in basic parameters, such as diameter, thread pitch and depth, but also in the shape, direction and type of thread. In accordance with this, a tap must be selected for each specific element for applying internal threads. So, we list the main parameters by which they differ.

By thread direction:

• Right-handed - make a groove in a clockwise direction (right-handed threads predominate in most fasteners).
• Left-handed - cut threads in a counterclockwise direction (fasteners with left-handed threads are usually installed on rotating parts so that the connection does not loosen when rotating).

By profile shape:

• Conical - used to create threads in places where fasteners are installed where a tight connection is required, for example, on parts under liquid or gas pressure.
• Trapezoidal - used for cutting the so-called running thread, which is usually present in parts that convert rotational motion into translational motion.

In addition, there are metric and inch taps (depending on the units of measurement in which the characteristics of the diameter and thread pitch are indicated).

As for their purpose, there are universal tools and highly specialized ones designed to work with one type of parts, for example, pipes , nuts , spark plugs .

Knowing all these parameters, you can easily select a tap for cutting threads in a specific part or fastener.

For example, if you need to re-thread a spark plug in a car engine, you will need a conical spark plug tap like the Jonnesway AI060001.

Carving according to all rules

To make it easier for you to understand the principle of working with a tap, we will tell you about the stages of cutting a thread in a through hole.

Stage 1.

Knowing the diameter of the hole, you need to select a drill and taps suitable for these parameters. For example, you need to get a threaded hole with a diameter of 8 mm, which means that a tap with an M8 thread will do. Moreover, you need to drill a hole of a smaller diameter.

Stage 2.

Drill a hole into which the tap will be screwed. Recommended indicators for selecting a drill are given in the table:

Thread diameter, mm	Diameter of drilled hole, mm
In parts made of soft metals (brass, steel)	In parts made of hard metals (cast iron, bronze)
3	2,5	2,5
4	3,3	3,3
5	4,2	4,1
6	4,9	5
7	6	5,9
8	6,7	6,6
9	7,7	7,7
10	8,4	8,3

Stage 3.

rough into the prepared hole , then a finishing one . The first has larger cutters on the working part, therefore, when screwing in, it removes up to 75% of the material, and the second is necessary for the final removal of 25% of the remaining metal and obtaining a neat thread.

The tap shank is fixed in a tap holder , a special device with the help of which a rotational movement will be created. The T-shaped handle makes it easier to rotate the threading tool in the body of the part, while the tap itself is securely fixed in the mounting hole.

The tap holder must be selected based on what taps you use, for example, STAYER 28039-T4 is suitable for working with tools with a diameter of M6-M12, and STAYER 28039-T2 is suitable for M3-M6.

When rotating the handle of the tap holder, you should not make sudden movements; the movement of the tool should be smooth . Therefore, before screwing the threading tool into the hole, do not forget to lubricate its working part with oil or kerosene.

This will make it easier to enter the material and help obtain a better thread; in addition, the lubricant will prevent corrosion on the working part.

Do not forget to remove any metal shavings that form from the hole , this will allow you to achieve more accurate thread cutting and reduce the likelihood of breakage of the tap.

As you can see, there is nothing complicated in using a tap. The main thing is to follow the rules and over time the skill will come. But that's not all there is to know. Indeed, in practice you will have to deal with cutting threads not only in through holes, but also in blind ones, and work with workpieces of various shapes and from various materials. To ensure that you are prepared for such work, we will give you some tips.

Simple solutions to complex problems

We found out what problems novice users most often encounter when cutting internal threads. The most common is the breakage of the tap during screwing.

What to do if the rod breaks off and the working part of the tool gets stuck in the body of the part? There are several options to solve this problem. If a small piece of debris protrudes from the hole, you can grab it with pliers and unscrew it.

If the rod breaks off inside the hole, it can be removed with an extractor (a special tool that is screwed into the body of the broken tap), but finding a suitable extractor can be difficult. Therefore, some craftsmen resort to a simpler method: drop nitric acid onto the fragment so that it corrodes the cutting edges.

If none of the methods helps, you will have to take the part to a workshop where there is a lathe.

As you know, it is better to prevent a problem than to waste time solving it. Therefore, to avoid breakage of the tap, before use you need to make sure that it is of high quality .

As practice shows, thread-cutting tools made of low-quality metal or those whose working part is rusty most often break. It is better to use branded taps, which are made of durable steel and do not break.

This way you will be able to get a neat thread the first time, and you won’t have to redo anything.  

You can purchase taps and tap holders in our online store. They are sold both individually and in sets; you can easily select the necessary set for the job. We offer only branded hand tools from such manufacturers as Jonnesway, FIT, MATRIX, STAYER, Zubr, so you can be sure of their quality and reliability. Don’t delay your purchase, order a thread-cutting tool right now, because you may need it at any moment!

Source: http://ooo-asteko.ru/kak-narezat-levuyu-rezbu-metchikom/

How to cut internal threads in metal - Metalworker's Guide

Perhaps the most reliable means of connection is a threaded connection.

When something breaks, the first thought that comes to mind is to secure the broken part with a bolt.

In addition to the durability and strength of the threaded connection, it has the property of being removable, which often plays a decisive role when choosing this type of connection.

So, before we figure out how to cut a thread with a tap, let's figure out the types of threads.

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Types of helix

A thread is a helical surface applied to bodies of rotation, such as a cylinder, as is the case with a bolt. There are two types of thread:

• right: the helix rises counterclockwise;
• left: the helix rises clockwise.

Thus, the name of the thread corresponds to the direction of twisting. It should be noted that in addition to the direction of twisting, threads are divided into the following two types:

• internal: used in holes;
• external: used on rods.

Also, each thread is characterized by the following parameters:

• profile;
• profile angle;
• step(P);
• outer and inner diameters (d2 and d1);
• thread depth (t).

Figure 1 – Diagram of the general appearance of the thread

In everyday life, right-handed rectangular and thrust threads, shown in the figure below, are most often used.

Figure 2 – Scheme of rectangular and thrust threads

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Thread cutting tool

Since we are faced with the task of cutting the thread ourselves at home, we will use a hand tap for the work.

Figure 3 – Hand tap for internal threading

The working part of the tap is directly used for cutting threads. It is a structure of two elements: intake and calibrating parts. The intake part is made in the form of a cone and performs the main work of cutting threads, while the calibrating part cleans the thread and guides the tap.

Figure 4 – Design of a hand tap

Dies are used to cut external threads.

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Internal thread cutting

The first step in how to tap a thread is to drill the hole. This stage is essentially the most important, because if you make a mistake with the choice of diameter, the bolt will either dangle, or the tap may simply break from overload.

The diameter of the holes is best selected from tables, but a rough estimate can be made: the diameter of the hole should be equal to the difference between the diameter of the thread and its pitch.

For example, with an outer diameter of 20 mm and a pitch of 1 mm, it is necessary to drill a hole with a diameter of 19 mm.

Attention! When drilling, make sure that the hole is strictly perpendicular to the plane. Any deviations can lead to marriage.

Having drilled a hole with a drill of a suitable diameter, we proceed directly to cutting the thread with a tap. To fix the tap, it is recommended to use the “wrench” shown in the figure below. If there is no wrench, use a regular adjustable wrench.

Figure 5 – Tap driver

Figure 6 – Drivers for taps and round dies

We fix the part in a vice, add a little lubricant to the hole.

Next, to cut the thread with a tap manually, we perform reciprocating movements: two turns clockwise, one or half a turn back.

Turning in the opposite direction is necessary to remove chips generated when cutting threads. Having passed the hole with a rough tap, we perform the steps described above with a second tap.

It is worth noting that situations often arise when it is necessary to make a thread in a fairly thin plate of soft metal, about 3-4 mm thick. In this case, you can mechanize the process using a screwdriver or drill. In this case, instead of attaching the tap to the driver, we clamp it into the screwdriver.

Rules for cutting internal threads using a tap:

1. If the hole in which the thread is being cut is deep enough, then you should periodically turn the tap out of the hole. Following this rule is necessary to clean the grooves, otherwise the tap can easily become warped. This applies more to soft metals such as copper and aluminum.

2. Use all the taps from the set in sequence: first rough, then medium and finally finishing. Otherwise, the thread may turn out to be of poor quality, and the taps may burst due to fragility.

Figure 6 – Set of taps

3. If it is necessary to cut a thread in a blind hole, the depth of the hole should be slightly greater than the planned length of the thread.

4. When machining deep holes, lubrication plays an important role. Experts recommend using emulsion, kerosene or linseed oil rather than machine oil.

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Table of drill diameters for holes for cutting metric threads (GOST 19257-73)

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We bring to your attention a video that shows how to properly cut a thread with a tap.

And another video about how to cut an external thread on a rod.

Healthy? Save it to your wall! Thank you for like!

Source: https://ssk2121.com/kak-narezat-vnutrennyuyu-rezbu-v-metalle/

How to cut threads on a pipe with your own hands

• What tool do you need?
• Do-it-yourself thread cutting
• Thread cutting using a die
• Cutting threads using a die
• Cutting internal threads on pipes
• How to cut a thread on a pipe with your own hands
• How to cut threads on a pipe near a wall

To assemble modern pipelines, pipes made of plastic or metal can be used, and a welding machine is used to connect plastic pipes. As for metal products, their assembly involves the presence of threaded fittings: this ensures maximum connection strength. To implement this method, threads will need to be cut on the pipes themselves.

What tool do you need?

Threading pipes will require the following equipment:

1. Tape measure, pencil, caliper . To assemble the pipeline, it is necessary to develop a diagram in advance. First, a pipe with the specified length is taken: markings are made with a tape measure and a pencil. Using a caliper, the diameter is measured and suitable devices are selected. When marking, it is important to maintain considerable precision and accuracy, since any deviation from the specified size leads to a violation of the correctness of the entire structure. As a result, in such cases it is often necessary to redo the entire pipeline.
2. Bulgarian . Using this tool, pipes are cut according to the marked marks. A simple hacksaw for metal can perform the same functions.
3. Vise . During operation, the pipe must be securely fixed in a strictly horizontal position.
4. Machine oil or other lubricant . To facilitate manual thread cutting, it is practiced to lubricate the tool and the area being processed with a special substance.
5. Thread cutting tools . Pipe threads can be cut with a die, a die or a tap. Which tool to use depends on the type of thread being cut and the preferences of the performer. For different jobs, different pipe threading kits are used, depending on the situation. The external thread is cut with a die, which is held by a die or die holder. To apply internal threads you will need taps.

Do-it-yourself thread cutting

Self-threading begins with a number of preparatory measures:

1. Cutting a piece of pipe to size . When replacing a damaged section of a pipeline, the first step is to carefully cut out this section in a direction strictly perpendicular to the wall. If this condition is not met.
2. Cleaning the thread area . From the place where the pipe thread will be cut, all paint and corrosion must be completely removed: if this is not done, the work can be clearly difficult.
3. Chamfering . To make the work easier, you need to remove the chamfer from the ends of the pipe.

Thread cutting using a die

The die is used for cutting external threads, which requires the following operations:

• Select a die with the required diameter. To make the selection correctly, you must definitely check it with a caliper.
• Lubricating the internal cavity of the clamp and the prepared area on the pipe using machine oil.

Source: https://the-master.ru/truby/kak-narezat-rezbu-na-trube-svoimi-rukami

How and with what to cut internal threads. Required tool, process description | Mashkrepezh

In the stages preceding the assembly of threaded connections using fasteners, there is often a need to cut internal threads in finished products and workpieces. For bolts, screws and studs, a hole of the required diameter is pre-drilled in them, then the internal thread is cut with the specified parameters.

Thread cutting tool

In drilled through or blind holes, the internal thread is cut with a special tool - taps . According to their purpose, such tools are divided into hand, machine-hand, machine and nut taps.

The design of the tap includes a working part and a shank, the end of which has a square cross-section for attaching the driver. Hand taps for cutting metric and inch threads are produced in sets (sets) of two or three products.

For cutting internal threads with a pitch of no more than 3 mm, sets of two taps are used, and for threads with a pitch of more than 3 mm, sets of three are used. The set of three tools includes roughing , medium and finishing taps , differing in the length of the taper cone.

Rough and medium - have smaller diameters than finishing, which is made with a full profile. On the shank of each tap there are one, two or three marks, which determine the order of use of each of them when cutting internal threads in one hole.

Tapping holes

For drilling a hole for cutting internal metric threads. choose a drill whose diameter is approximately calculated by the formula: D = d – P , where d is the diameter of the internal thread, P is its pitch. For example, cutting metric M10 threads with pitches of 0.5, 0.75, 1.0, 1.25 and 1.

5 millimeters (for bolts, screws or studs) will require the use of a drill with a diameter of 9.5, 9.25, 9.00, 8.80 and 8.50 mm, respectively. And drilling holes for cutting ¼-inch cylindrical pipe threads

In blind holes, drilling is performed to a depth exceeding the length of the threaded part of the fastener by 5-6 mm.

Internal thread cutting is performed as follows. The part with the finished hole is rigidly fixed, for example, in a vice.

Then the working part of the rough tap is coated with lubricant, the tool is inserted with the chamfer part into the hole and by smoothly turning the driver, they begin to cut the thread inside the part.

After one or two turns clockwise, make a half turn in the opposite direction to crush the chips and then continue cutting until the tap fully enters the hole. The same operation is performed with a middle and finishing tool.

Source: https://www.rusbolt.ru/articles/11419/

How to cut internal threads in metal

remontoni.guru > Tools and equipment > How to cut internal threads - types of taps, technology, tips

There are many ways to connect parts, but the most common and accessible is still screw (bolt) fasteners. It is this type of fastener that we will talk about. More precisely, we will look at the types of taps, the technology for cutting threads in holes for screws and bolts of different diameters.

• Types of taps
• Specification for cutting method
• Specification by hole type
• Marking of taps
• How to cut a thread with a tap - technology
• Some useful tips
• Let's sum it up

Types of taps

Taps are divided depending on the method of making the thread , as well as depending on the hole for which they are intended.

Specification for cutting method

According to the cutting method they are distinguished:

1. Go-through taps. A special feature of this tool is that it has both marking cutting teeth and teeth for finishing thread cutting. Most often, such tools are used when working with parts made of soft metals, for example, aluminum, copper, brass.
2. Complete taps. In this case we are talking about several tools for carving. The minimum set consists of three taps for different stages of cutting: the first is intended for roughing, the second for intermediate, and the third for final. Of course, doing the job with such a kit takes more time compared to using one through tap, but the quality of the turns is much higher.

Specification by hole type

Technological holes can be blind or through. For each type of hole, the appropriate type of tap should be used. Through holes are processed with a tool with a sharp end, and blind holes with a tool with a cut end. Working with a tap for a blind hole is more difficult, since very often when it reaches the bottom of the hole it can stall and break, but with successful cutting, a high-quality thread is obtained along the entire length of the hole.

Separately, it should be noted that, in addition to what was mentioned above, taps are divided into machine and machine-manual. The first ones have an elongated shank and can be installed in any electric machine, with the help of which the threads will be cut. The latter can be used both when performing work manually and when performing work using a power tool.

Marking of taps

Taps for cutting internal metric threads are marked with the letter “M”. In this case, the letter “M” is followed by the value of the diameter of the thread being cut. In addition to the diameter, the thread pitch is also indicated on the tool.

For example, the marking M4 × 1 means that the tool can make threads in a hole with a diameter of 4 mm in increments of 1 mm. In the case of a cutting tool for left-hand threads, the tool is marked LH.

The diameter and pitch of the thread are indicated in a manner similar to that described above.

How to cut a thread with a tap - technology

Internal thread cutting looks like this:

1. The workpiece is drilled. Drilling is best done using a drilling machine, because in this case the hole is strictly perpendicular. The diameter of the drill is selected according to the table.
2. After drilling, the hole is countersinked on a machine or using an electric drill. A countersink is necessary to obtain a small cylindrical recess at the end of the hole.
3. The workpiece is fixed in a bench vice. A tap pre-lubricated with machine oil is installed in the hole to be machined. The cutting tool must be installed strictly vertically; skew in one direction or another is not allowed.
4. A crank is put on the tap, and, pressing it against the workpiece with the left hand, the right hand carefully turns it until the tap cuts into the metal and takes an even position.
5. The driver is smoothly rotated with both hands, while making two full turns, it is turned in the opposite direction, thereby breaking off the chips. This way the entire hole goes through. Remember, if you do not break off the chips, the tool may jam, and this, in turn, can lead to its breakage.
6. After cutting, the tap is unscrewed and the thread is checked. Checking is carried out using a screw or bolt of suitable diameter. Screwing in and out should occur without much effort.

For maximum clarity, we invite you to watch a short video that discusses in detail the process of cutting internal threads.

Some useful tips

• If you need to cut threads in stainless steel, it is best to use oleic acid or an emulsion based on it as a tap lubricant. You can get such an acid or emulsion from turners;
• Drilling for subsequent processing should be done with a sharp drill. If you use a dull drill, during the drilling process there is a risk of “losing” the metal, as a result of which the fastener will not be so strong;
• if it is necessary to cut a small diameter thread in an aluminum workpiece, it is best to use ethyl alcohol as a lubricant;
• If a drill of the required diameter is not available, it is better to use a drill with a smaller rather than a larger diameter for drilling.

Let's sum it up

In order to really cut a high-quality thread in a workpiece made of a particular metal, you do not need to have any special knowledge or experience. As practice shows, even a master who is far from plumbing can cope with such work.

The main advice is to avoid haste and approach all operations, including preparatory ones, responsibly . No less important is the choice of tool to complete the job - there is no need to skimp. Remember: cheap, low-quality taps often break off during operation, and removing a piece of tool from a hole is extremely problematic.

Tapping internal threads

Source: https://respect-kovka.com/kak-narezat-vnutrennyuyu-rezbu-v-metalle/

Proper internal thread cutting

Threaded connections are considered one of the most popular. They are used in different areas of human life. Compared to welding seams, they are detachable, which makes it possible to simply dismantle structures. In addition, there is no deformation of parts, and the amount of scrap is reduced. To make a reliable connection, you need to know how to cut an internal thread and what tool to use.

Internal thread cutting

Types of instruments

Craftsmen cut threaded connections using hand tools and industrial equipment. Cutting steel is done using taps that are attached to special handles or spindles of machine tools. To apply threads to the inner side of different diameters, you need to select dies of the required sizes. They are divided according to various factors, which include:

1. By method of use - manual, machine. The first option is equipped with a knob and a handle for holding. The second option is tools that are fixed in the chucks of industrial equipment.
2. According to the method of cutting internal turns on metal, complete, universal taps are distinguished. The first are tools, the working part of which is divided into 3 zones. The first one does rough processing, the second one bores the grooves, the third one brings the surfaces to the final state. The second option is a set of individual taps, each of which is designed for specific types of processing.
3. Separation by hole type. There are tools for working with blind and through holes. The first option has a long rod, which has an oblong conical shape called a lead.

Taps are divided by design. They can be straight, screw, with cut grooves for removing metal chips.

Taps are used to create metric threads. Additionally, they can be used to apply inch and pipe threads. In this case, the shape of the tool can be conical or cylindrical.

How to correctly determine the hole size?

The quality of cutting internal threads depends on the correct choice of the diameter of the device for the work. In order to process a hole according to standard drill sizes, you can use a special table that is available on the Internet. It was created specifically in accordance with GOST standards in order to obtain high-quality connections without damaging the workpieces. The table contains the relationship between diameter and pitch, thread length.

Preparing for thread cutting

After determining the size of the holes and the pitch of the manufactured turns, it is necessary to prepare tools and devices for the work:

1. Electric drill with the ability to change speed. An excellent option is a drill press with a setting panel. Work must be carried out at low speeds.
2. Set of taps.
3. Vise for clamping workpieces. Their size depends on the dimensions of the parts being processed.
4. Hand crank.
5. Core, hammer.
6. Drill for metal.
7. Rags, wire brush.

After preparing the tools, you can begin work.

Execution of work

Internal thread cutting is a technological process that is carried out in several stages. Step-by-step instruction:

1. Before you can properly cut a thread with a tap, you need to prepare your power tool. Attach the drill bit to the chuck of a drill or machine tool. Set the speed to low. Apply special lubricant to the surface of the drill.
2. Make a recess at the site of the future hole using a hammer or core to more accurately position the drill. Small workpieces must be held motionless using a vice. Before starting drilling, you need to make sure that the drill is perpendicular to the working surface.
3. After creating the hole, you need to make a chamfer. For this, a drill of a slightly larger diameter is used. It is enough to lower it by 1 mm.
4. When the chamfered hole is ready, you can start cutting threads. For this, tap 1 is initially used. With its help, the master carries out rough processing. Movements should not be fast or chaotic. You need to make 2 turns along the thread, one against. Reverse movements are required. They are needed to remove metal shavings.

After carrying out the work with tap 1, you need to move on to 2, 3. The procedure is repeated. Do not move forward once you have difficulty turning the tool.

Tapping internal threads

Precautionary measures

There are several rules for carrying out work:

1. Do not attempt to cut threads with a tap mounted in the chuck of an electric drill. With this power tool it is impossible to set the exact angle or force.
2. You cannot continue moving forward if difficulties arise. If you apply excessive pressure, the equipment will break and remain in the hole. It will be extremely difficult to get her out of there. To do this, you need to drill it out with different drills or clean the area around it with a grinder. After cleaning, try to pull out the fragment with pliers.
3. Check the drilling angle of the hole. It must be level to maintain the integrity of the equipment.
4. Use safety glasses to avoid metal shavings getting into your eyes.
5. After work, clean the holes from chips.
6. Movements should be smooth, without pressure.
7. Don't forget about chamfering.

Craftsmen recommend buying several devices for carrying out work, instead of one universal one.

Threaded connections can be made by anyone without practical experience. To do this, you need to buy a set of taps for internal threads and dies for external threads. Study the technological process, learn how to use tools.

Proper internal threading Link to main publication

Source: https://metalloy.ru/obrabotka/rezba/narezat-vnutrennyuyu-rezbu