How to cut external threads correctly

How to cut a thread with a die or tap, incl. on pipes

A threaded connection is one of the most common methods of fastening various parts. Today there are many varieties of bolts, nuts, screws, etc., but sometimes there are situations in which you need to cut threads yourself, for example, in a hole made in metal or on a metal water pipe.

There are several tools and thread cutting methods for this, let's look at them.

:
1. Types of thread.
2. Educational program: what you need to know when cutting threads by hand.
3. How to cut external threads using a die.
3.1 The principle of cutting threads with a die.
3.

3 Cut the thread with a die with your own hands (video).
4. Cutting internal threads with a tap.
4.1 Manual cutting of internal threads with a tap (video).
5. Cutting threads on a metal pipe with your own hands.
5.1 Cutting external threads on a pipe using a die (die).
5.2 What is a clamp and how to use it (video).

5.3 Cutting internal threads on a pipe with a tap.

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.

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.

Source: https://chonemuzhik.ru/kak-narezat-rezbu-plashkoj-ili-metchikom-vt-ch-na-trubax.html

How to properly cut a thread with a tap: algorithm, recommendations, size tables

The question of how to cut a thread with a tap arises in cases where a pre-made hole needs to be prepared to accommodate a bolt, screw, stud or any other type of threaded fastener. In such situations, it is the tap that is the main tool that allows you to quickly and accurately cut an internal thread with the required geometric parameters.

Manual cutting of internal threads is performed using metalworking taps complete with a wrench

Types and areas of application of taps

Internal thread cutting can be done manually or using various types of machines (drilling, lathe, etc.). The working tools that perform the main work of cutting internal threads are machine-hand or machine taps.

Taps are divided into different types depending on a number of parameters. The following principles for classifying taps are generally accepted.

1. According to the method of rotation, a distinction is made between machine-manual and machine taps, with the help of which internal threads are cut. Machine-hand taps equipped with a square shank are used in conjunction with a special device with two handles (this is the so-called tap holder). With the help of such a device, the tap is rotated and cuts the thread. Thread cutting with a machine tap is carried out on metal-cutting machines of various types, in the chuck of which such a tool is fixed.
2. Based on the method by which internal threads are cut, a distinction is made between universal (through) taps and complete taps. The working part of the former is divided into several sections, each of which differs from the others in its geometric parameters. The section of the working part that first begins to interact with the surface being processed performs rough processing, the second - intermediate, and the third, located closer to the shank - finishing. Cutting threads with complete taps requires the use of several tools. So, if a set consists of three taps, then the first of them is intended for roughing, the second for intermediate, and the third for finishing. As a rule, a set of taps for cutting threads of a certain diameter includes three tools, but in some cases, when products made of particularly hard material are processed, sets consisting of five tools can be used.
3. Based on the type of hole on the inner surface of which it is necessary to cut a thread, taps for through and blind holes are distinguished. A tool for processing through holes is characterized by an elongated conical tip (approach), which smoothly passes into the working part. Universal type taps most often have this design. The process of cutting internal threads in blind holes is carried out using taps, the conical tip of which is cut off and performs the function of a simple milling cutter. This design of the tap allows it to cut threads to the full depth of a blind hole. To cut a thread of this type, as a rule, a set of taps is used, driven manually using a wrench.
4. According to the design of the working part, taps can have straight, helical or shortened chip removal grooves. It should be borne in mind that taps with grooves of various types can be used for cutting threads in products made of relatively soft materials - carbon, low-alloy steel alloys, etc. If threads need to be cut in parts made of very hard or viscous materials (stainless, heat-resistant steels, etc.), then for these purposes taps are used, the cutting elements of which are arranged in a checkerboard pattern.

A good tap is made of high-quality tool steel, looks neat and has smoothly machined turns and grooves

Taps are usually used for cutting metric threads, but there are tools that can be used to cut pipe and inch internal threads. In addition, taps also differ in the shape of their working surface, which can be cylindrical or conical.

Preparing to cut internal threads

In order for the process of cutting internal threads using a tap to not cause any particular difficulties and result in a high-quality result, it is necessary to properly prepare for this technological operation.

All methods of cutting threads using a tap assume that a hole with the appropriate diameter has already been made in the workpiece.

If the internal thread that needs to be cut has a standard size, then a special table with data in accordance with GOST can be used to determine the diameter of the preparation hole.

Table 1. Diameters of holes drilled for standard metric threads

If the thread that needs to be cut does not belong to the standard category, you can calculate the diameter of the hole to make it using a universal formula. First of all, it is necessary to study the marking of the tap, which must indicate the type of thread being cut, its diameter and pitch, measured in millimeters (for metric).

Then, to determine the cross-sectional size of the hole that needs to be drilled for the thread, it is enough to subtract the pitch from its diameter. For example, if a tool marked M6x0.75 is used to cut a non-standard internal thread, then the diameter of the preparation hole is calculated as follows: 6 – 0.75 = 5.25 mm.

For standard threads belonging to the inch category, there is also a table that allows you to choose the right drill with which to carry out the preparatory work.

Table 2. Diameters of holes drilled for inch threads

An important question to obtain a high-quality result is not only the question of what is used to cut the thread, but also what drill to use to make the preparation hole. When choosing a drill, you need to pay attention to the parameters and quality of its sharpening, as well as to ensure that it rotates in the chuck of the equipment used without runout.

The sharpening angle of the cutting part is selected depending on the hardness of the material that needs to be drilled. The higher the hardness of the material, the greater the sharpening angle of the drill should be, but this value should not exceed 140°.

When drilling blind holes, control the drilling depth

How to cut threads correctly? First you need to select tools and consumables:

1. an electric drill or drilling machine capable of operating at low speeds;
2. a drill whose diameter is calculated or selected using reference tables;
3. a drill or countersink, with the help of which a chamfer will be removed from the edge of the prepared hole;
4. a set of taps of the appropriate size;
5. manual holder for taps (drives);
6. bench vice (if the product in which the thread needs to be cut needs to be fixed);
7. core;
8. hammer;
9. machine oil or other composition, which during the processing process must be used to lubricate both the tap and the thread section being cut by it;
10. rags.

Diagram of thread cutting with a tap

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.

Source: http://met-all.org/obrabotka/prochie/kak-narezat-rezbu-metchikom-tablitsa.html

How to cut a thread with a die?

If it is necessary to manually cut external threads for a pipe connection, make a stud or bolt for a nut with a metric thread, a simple but quite effective tool is most often used - a die. The thread preparation process is quite simple if you follow the instructions below exactly.

Preparing to cut threads with a die

Before cutting a thread with a die on a rod or pipe, you need to select a tool of the required diameter and pitch. The die itself is a nut with conical cutting teeth with holes for fastening in the collar.

The dies can be solid, split, sliding, round, square or hexagonal.   

First of all, you need to select the material and tool of the required diameter.

Below is a table of correspondence between the most popular diameters for metric, imperial and pipe threads with an example of selecting a workpiece for an M6 thread

 

As we can see from the table, to cut an M6 thread we need a rod with a diameter of 5.8 mm. For larger thread diameters, there is an acceptable minimum and maximum value for the rod thickness. You cannot violate it - if the diameter is exceeded, you risk breaking the die; if the value is less than the minimum, you will get a weak thread.  

Before you start cutting external threads with a die, in addition to the tool itself and the workpiece, you need a driver suitable in shape and size, as well as machine oil. After this, you can proceed directly to the cutting itself.

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.

 

Further actions:

• 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.

Source: https://mekkain.ru/stati/kak-narezat-rezbu-plashkoj.html

How to cut threads

Threads are one of the most convenient detachable connections, and therefore information on how to cut threads may be useful in the household. There are inch and metric threads, so it happens that a screw that seems suitable at first glance turns out to be unsuitable - the diameter is not the same and the thread pitch is different. Even the profiles of metric and inch threads are different: the apex angle in a metric thread is 60 degrees, and in an inch thread it is 55 degrees.

Any threaded connection consists of two parts, one of which has an internal thread in the hole, and the second has an external thread on a cylindrical surface. Mostly they use right-handed threads, in which rotation occurs clockwise, but sometimes left-handed threads with counterclockwise rotation are also found.

For a thread, the main dimensions are the pitch - the distance between its turns) and the outer diameter. They are interconnected and are standard. Both internal and external threads are determined by the size of the diameter of the rod, that is, if an M10 thread is indicated, then this thread is metric, right-handed, with a screw diameter of 10 mm and a thread pitch of 1.5 mm.

Sometimes non-standardized threads are used, for example, camera lenses are mounted on threads with a diameter of 42 mm. According to the standard, the pitch for this thread is 4.5 mm, but for an optical device this is too large a parameter, so a pitch of 1 mm is used. There are special standards for small threads.

Basic thread sizes can be found in reference books and standards.

Any threads are cut using special tools and machines, and at home you can cut internal and external threads on fasteners with a diameter of up to ten millimeters. To do this, use a simple tool such as sets of dies (for external threads) or taps (1) (for internal threads). The dies (2) are a carbide tool, similar to a nut with cutting grooves.

Taps (1) are also made of carbide; this tool is similar to a screw with cutting grooves. Typically, not one tap is used, but a set of two or three tools that are used for roughing and finishing passes, and have different depths for cutting thread grooves. When cutting threads, both taps and dies are clamped into special devices - cranks (3), the size of which must be suitable for the tool used.

Tools for cutting threads must be of high quality and sharp. It will be impossible to cut a good thread with a dull rusty tap, and there is a high probability that it will break in the first hole, and in this case there will be more problems with its removal from the workpiece. Low quality metal taps are only suitable for working with plastic. As for dies, a blunt tool will cut uneven threads, and then the nut can only be screwed on with great effort.

External thread cutting

A round metal rod with a diameter equal to the diameter of the required thread is firmly clamped in a vice in a vertical position. At the end of the workpiece, use a file or a velvet file to chamfer the tool and generously lubricate the workpiece with machine oil to facilitate thread cutting.

A suitable die is secured in a special driver and begins to be put on the end of the workpiece. The tool is screwed onto the workpiece, making sure that there are no distortions. With a right-hand thread, after one or one and a half turns clockwise, the die must be turned half a turn in the opposite direction.

This is how the entire required thread length is passed until the work is completed.

Internal thread cutting

First, a hole of the required diameter is drilled in the workpiece and a chamfer is removed to allow the tool to fit in. The drill diameter is selected according to reference data. The holes in the workpiece can be through (throughout the entire thickness of the part) or blind. If a hole with an internal thread of a short length is required, then in this case a hole of a greater length than the thread is drilled, since the taper of the tap in the lower part must be taken into account. Allowances for drilling depth should also be taken into account.

For greater profile cleanliness, internal threads are formed using three taps. The first of them forms a preliminary passage; it is indicated by a mark in the upper smooth part of the tool. The second tap from the set completes the thread formation (it is indicated by two marks), and the third tool finally forms the thread profile, it is indicated by three marks. In this way, the thread is cut gradually, resulting in a clear profile.

For holes up to three millimeters in diameter, use a set of two taps. The process of cutting threads is the same as when working with dies - repeating forward and backward movements to break chips from the tool using lubricant. If the thread is cut in blind holes, then it is advisable to periodically turn the tap out to completely remove metal filings from its surface.

They are removed with an old toothbrush or cloth, and then you need to lubricate the tool again and continue cutting the thread until it stops.

Adviсe

• If the thread accidentally becomes dented during work, it can be restored by holding the part in a vice and driving the thread again with a tap or die.
• If you need to further lengthen the surface of a threaded screw, you must ensure that the die easily fits along the existing threads and does not spoil its profile.
• To prevent the thread from corrosion, it can be lubricated with petroleum jelly.
• If during cutting there is a skew and the external thread “goes” to the side, then you can cut off a piece of the rod and start the process again.
• If the tap breaks in a hole, and it is not possible to drill another hole nearby, you can remove the broken tool in several ways. If part of the tap remains sticking out, then its end is ground into the shape of a spatula and turned out with pliers. And if part of the tap remains inside, then use nitric acid and a wooden stick: a drop of acid is applied to the broken tap and wait until the acid destroys its cutting edges. Then the fragment is pulled out with tweezers or knocked out from the other side of the hole (if it is through).

Evaluate the manufacturing method:

Source: http://sdelai-sam.pp.ua/?p=8375

How to cut a thread. Internal and external thread cutting

Threaded connections are simple, reliable, and make it possible to adjust the tightening, as well as disassemble and assemble parts and mechanisms. They are widely used in various mechanisms, devices, and devices.

 Threads can be external (screw) or internal (nut). There are cylindrical triangular (sawtooth), conical triangular, rectangular, trapezoidal, thrust, and round threads. The most widely used is the cylindrical triangular or, as it is also called, fastening thread, figure No. 1.

Figure No. 1 – Thread elements on a bolt

1 - depth;

2 - top; 3 - step;

4 — depression;

5 - outer diameter;

6—inner diameter.

Internal thread cutting:

First of all, you need to choose the right drill bit for drilling the hole.

You should know that if you drill a hole for a thread with a diameter that exactly matches the internal diameter of the thread, then the metal squeezed out during cutting will put pressure on the teeth of the tap, which can cause the thread to end up with torn threads, and the tap may break.

If you drill a hole that is too large in diameter, the thread depth will be incomplete and the connection will be weak.
When drilling a blind hole for a thread, its depth must be made slightly larger than the part being cut, otherwise the thread will be incomplete in length.

Thread cutting is carried out in the following sequence: mark the drilling location with a center punch; secure the part in a vice; drill a hole; insert the tap into the hole (Figure 2) strictly vertically (along the square); put a crank on the tap, press it against the tap with your left hand, and turn it to the right with your right hand until the tap cuts into the metal on several threads and takes a stable position; take the knob by the handles with both hands and rotate it with the hands intercepted every 1-2 turns. Thread cutting is greatly facilitated if you use a tap to make 1-2 working turns to the right and 1-2 turns to the left; Having finished cutting, the tap is unscrewed from the hole, then once again driven along the resulting thread.

Figure No. 2 - Cutting internal threads with a tap:

a — installation of the tap in the hole;

b - thread cutting.

Rules for working with taps:

When cutting threads in deep holes, in soft and tough metals (copper, aluminum, bronze, etc.), the tap must be periodically unscrewed from the hole and the grooves must be cleared of chips; You need to cut a thread with a full set of taps - rough, medium and finishing.

The middle and finishing taps are inserted into the hole without a driver and only after the tap follows the thread correctly, a driver is put on the head and threading continues;
during the cutting process, you need to use a square to carefully ensure that there is no skew of the tap; The thread cutting area should be lubricated with oil.

External thread cutting:

At home, it is done with dies by hand.
The diameter of the rod for external threads should be 0.3-0.4 mm less than the outer diameter of the thread being cut. Deviations from this rule are not permitted.

Cutting an external thread with a round die is done in the following order:
a chamfer is removed at the upper end of the rod, which ensures that the die cuts into the metal;

The rod is clamped vertically in a vice so that its protruding end is 20-25 mm longer than the length of the part being cut (Figure No. 3); Place a die fixed in a knob on the rod and rotate it with slight pressure so that the die cuts into about 1-2 threads without distortion. After this, lubricate the rod with oil and smoothly rotate the knob 1-2 turns to the right and 1/2 turn to the left.

Thread cutting with sliding prismatic dies (Figure No. 3) is performed as follows: a chamfer is filed at the end of the rod; install dies into the die; clamp the rod in a vice; put the clamp on the rod and move the nuts tightly with a clamping screw; lubricate the dies and the rod with oil; The die is turned 1 - 1.5 turns clockwise, then 1-4, 1-2 turns back, and so on until the end of the thread; Having cut the thread, screw the die to the end of the rod, tighten the dies with a screw and pass the thread a second time; check the thread with a nut of the appropriate diameter; at the end of the work, the dies are removed from the die, cleaned of chips, wiped and lubricated with oil; wipe the clutch.

Figure No. 3 - Cutting threads using a die

a — Cutting threads with a round die
b — Cutting threads with prismatic dies

Source: https://bip-mip.com/narezanie-rezby.html

How to properly cut threads with dies and taps - instructions

Often, when performing home repairs, it becomes necessary to make threads - external or internal. In order not to involve specialists in this, but to do it yourself, you need to purchase a special tool. Cutting with dies and taps does not require any special skills or abilities. It is enough to know their types and technical parameters.

A little about the features of the tool

The first step is to decide on the type of thread. It is divided into 2 main types: metric and inch. The first one with the left direction is most often used. In order not to measure the distance between the grooves, you can find out the type by the shape. A metric thread in cross-section is an equilateral triangle, and an inch thread is an isosceles one.

Types of thread

Which products use a certain type of thread? Fasteners use metric, while water pipes use inch. In addition, you need to take into account the following factors that influence the process of cutting connecting elements.

1. If the thread is intended to be connected to a finished part, its geometric dimensions must be appropriate.
2. When manufacturing complete fasteners, it is recommended to use the metric type.
3. The diameter of the workpiece must be different from the thread size. For the outside - to a lesser extent, for the inside - to a greater extent.

Self-cutting of threaded connections is carried out using dies and taps. They are made of high-strength steel with a standardized working fluid size.

Outdoor

The die is a nut with internal slots and external clamps for turning the tool. It can be of various shapes - round, square or hexagonal. If the work is carried out at home, you will need a vice to fix the part.

Die holder and dies

Before performing work, the main thing is to choose the correct diameter of the workpiece. It should be 0.2-0.3 mm smaller than the size of the future thread. For metric, you can use the data from the table.

The workpiece should be prepared in advance. If its cross-section is not a circle, you need to turn it. Then a conical chamfer is removed from the end part to mark the first turn of the thread.

Next you need to follow the instructions exactly:

1. Having secured the workpiece in a vice, the correctness of its location is checked.
2. Installing the die into the die holder. Its surface must be in the same plane as the surface of the workpiece end.
3. The first turn is performed with little effort. It is important to make turns in the right direction.
4. Having reached the lower limit, the die must be turned in the opposite direction.

External thread cutting

One such pass will not be enough to form a thread with good geometry. It is recommended to repeat the procedure 3-4 times until the die is freely screwed onto the workpiece. To check the quality, tighten a nut of the appropriate diameter. If force is observed, you can treat the outer part of the workpiece with fine-grained sandpaper.

Internal

Taps must be used to form internal threads. They are a cylinder with an external notch. If you need to process small parts with a diameter of up to 20 mm, you can use a manual type of tap. Larger sizes require machining using a machine.

Working with a tap

It is best to use a complete set of taps. It includes three parts that are designed for roughing, intermediate and finishing threaded holes. If you have a drill in your home kit, it is recommended to purchase taps with a tail mount.

The workpiece should be fixed. If this is a large-sized part, this can be done using clamps. For small products, a vice is used. Having secured the part, its location relative to the tap is checked.

The axis of the latter must be strictly perpendicular to the plane of the workpiece. The first pass will be made with great effort. Do not forget that for this you need to use a rough cutting tap. Having formed the primary thread, a tap is used for the intermediate thread.

And only after it can you begin final processing.

To reduce friction, specialists use solid oil or a similar product. In this way, mechanical damage to the part can be avoided. The formed thread must have the same geometry along its entire length. Otherwise, the connection strength may be lost.

Source: https://ismith.ru/metalworking/narezanie-rezby/

Thread cutting methods

Thread cutting is required for the manufacture of fasteners or fasteners of various designs from blanks. This requires a minimum number of tools, the technology is easy to implement, and experience is not required. Strict adherence to the basic cutting rules will allow you to create high-quality threads.

Thread cutting machine

Basic cutting methods

Threading methods:

• cutters or combs;
• dies, taps;
• rolling with round or flat dies;
• on a milling machine using special cutters;
• grinding with special wheels.

To cut external threads, cutters, dies, cutters, circles are used, and internal threads are used with taps.

To obtain a part with an accurate internal or external thread, when cutting with the tool holder, it is necessary to make one revolution around the axis by 1800, and the second - in the opposite direction by 900. This rule will allow you to get rid of long chips that have accumulated in the die and reduce the amount of applied rotational force.

How to cut threads

To cut threads, you will need the following tools:

• tap, set of thread-cutting tools, dies;
• drilling machine with speed control;
• electric drill with low speed operating mode;
• a set of drills for creating holes in parts;
• vice for fixing the workpiece;

Machine-hand taps are designed for manual use or for mounting in a drill chuck. For machine use, the designs are distinguished by an extended shank. It will not be possible to install a tap holder for manual threading on it.

• hammer;
• core for creating marks for drilling holes;
• a lubricant that prevents the tool or workpiece from overheating during processing;
• rags to remove oil after work.

Dies and taps for cutting

How to correctly determine the hole diameter

Before cutting internal threads, it is necessary to make a hole in the workpiece in advance. Its dimensions must be selected strictly, since exceeding the optimal value will not allow you to create a strong bolt connection, and reducing it will increase the likelihood of damage to the tool during operation.

To determine the diameter of the hole for a standard thread, you will need to use reference books. To create non-standard threads, you need to make simple calculations: subtract the pitch size from the diameter.

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 from 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. Thread cutting. Set of tools. Dies, lerks, runs, taps

Thread cutting methods Link to main publication

Source: https://metalloy.ru/obrabotka/rezba/narezka-rezby

Thread cutting. Tools, thread cutting methods

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

Threads are distinguished:

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

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

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

1. Thread cutting tool

An axial multi-edged tool for forming and processing internal threads is called a tap, and external threads are called a die.

Hand taps are used for cutting internal threads.

The working part of the tap with length f is divided into cutting (taking) and guiding (calibrating) parts with lengths l1 and l2, respectively (Fig. 1, a). The cutters of the cutting part have main edges located on the conical surface and auxiliary edges that are part of the threaded profile (Fig. 1, b).

The guide part serves to guide the tap and self-feed by screwing in, and also serves as a reserve for regrinding. The cone angle of the cutting part depends on the angle φ, which is set equal to 5° for hand taps, 3°30′ for nut taps and 6°30′ for machine taps.

The guide part has a reverse taper to reduce friction and eliminate dangerous jamming of the tap in the hole.

Rice. 1. Structural elements (a), thread profile (b) and geometric parameters (c) of the tap

The length of the tap portion of the tap is taken to be 45 S for a rough tap, 2.55 S for a medium tap, and (1.5–2.0) S for a finishing tap, where S is the pitch of the thread being cut. Machine taps are made with a short taper equal to (1.5–2) S.

The rake angles of the taps are selected depending on the material being processed according to the following data:

• for soft steel γ = 12–15°;
• steel of medium hardness γ = 8–10°;
• hard steel γ = 5°;
• cast iron and bronze γ = 0–5°;
• light alloys γ = 25–30° (Fig. 1, c).

The tail part of the tap is designed to secure it in a driver or chuck and to transmit torque.

Hand taps are produced in sets. The kit includes three taps, which are divided according to their purpose into rough, medium and finishing. Chernovoy cuts the thread, removing up to 60% of the metal; the middle one gives more accurate threads, removing up to 30% of the metal; the third (finishing) tap performs final cutting and calibration of the thread, removing up to 10% of the metal.

For cutting pipe and small metric threads, use a set of two taps.

The taps included in the set differ from each other in thread profile and length of the intake part.

According to the design of the cutting part, two types of taps are distinguished - cylindrical and conical (Fig. 2; a, b).

Rice. 2. Formation of a cutting surface in a set of taps: a – cylindrical design, b – conical design

With a cylindrical tap design, all three tools in the set have different diameters. The finishing tap has a full thread profile. The diameter of the average tap is less than normal by 0.6 of the cutting depth, and the diameter of the rough tap is less than the thread diameter by the full cutting depth.

The length of the intake part, taking into account the distribution of thread cutting work between the three taps of the set, is set in the ratio 4:2:1. Thus, for a rough tap, the length of the intake part is 6–7 threads, for a medium tap – 3–3.5, and for a finishing tap – 1.5–2 threads.

The cylindrical design of the tap ensures that the tips of the teeth cut chips in the form of wide platforms.

With a tapered tap design, all three tools in the set have the same diameter and full thread profile with varying tap lengths.

The thread within the intake part is made conical and additionally cut along the tops of the teeth into a cone.

For conical taps, the cutting part is equal: for a rough tap - the entire length of the working part, for a medium tap - half of this length, for a finishing tap - two threads.

Tapered taps are usually used when cutting through holes. Blind holes are cut with cylindrical taps.

The rear (back) surface (Fig. 1, c) of the cutting teeth is backed up in a spiral, which allows maintaining a constant profile of the teeth after they have been sharpened.

Collars and clamps . Threading with hand taps is carried out using cranks that fit onto the square ends of the shanks.

The most common are simple double-sided knobs (Fig. 3).

Rice. 3. Double-sided driver: a, a1, a2 – holes for tap shanks

Universal gates (Fig. 4) are a frame 1 with two crackers - movable 3 and fixed 4, forming a square hole. One of the handles 2 ends with a screw for clamping the square of the tap.

Rice. 4. Universal driver: a – hole for the tap shank

Another version of the universal driver is shown in Fig. 5. This driver allows you to work with taps whose square sizes range from 5x5 to 25x25 mm.

Rice. 5. Universal wrench

Round dies are used for cutting fastening threads on bolts, screws and studs when working manually and on machines (revolving, automatic, etc.).

The round die on each tooth 2 (Fig. 6, a) has a rear 1 and front 5 surface, a back of the tooth 3 and a cutting edge 6 formed by a chip hole 4. The round die has a cutting and guide part with lengths l1 and l2, respectively (Fig. 6 , b). The length of the cutting part is equal to one and a half threads of thread, and the thickness of the die is seven to eight threads.

Rice. 6. Structural elements (a), main parts (b) and shapes of chip holes (c) of a round die

Rake angles are taken for hard materials being processed γ = 10–12°; for materials of medium hardness γ = 15–20°; for soft materials γ = 22–50°.

Dies are used (Fig. 7) solid (a), split (b) and sliding.

Rice. 7. Dies

When cutting manually, round and sliding dies are installed in special cranks and clamps.

The collars for round dies are made of a frame into the hole of which the die is placed (Fig. 8).

Rice. 8. Driver for a round die

The die is kept from turning by three locking screws (1, 2 and 3), the conical ends of which fit into recesses on the side surface of the die. The fourth screw fits into the slot of the adjustable die and secures the correct thread size.

The clamps for sliding dies (Fig. 9, a) are an oblique frame with two handles. In the central hole of the frame with dimensions A and C, sliding dies are installed and centered. Installation of the sliding dies to the required size is carried out using a pressure screw 1 acting on the movable part of the sliding dies.

Clusters for cutting threads on pipes differ from conventional ones in that four steel combs 2 fit into the slots of the clamp holder (Fig. 9, b).

Rice. 9. Dies: a – for sliding dies; b – for cutting threads on pipes

By turning the upper handle 1, you can bring the dies closer together or move apart, and thanks to this, use the same die for cutting threads on pipes of different diameters. The pipe die is equipped with guides 3, which are adjusted in the same way as the dies, by a lower handle 4. This ensures the correct position of the die on the pipe when cutting threads.

2. Technology and techniques for manual thread cutting

When cutting threads with taps and dies, part of the metal is not removed along with the chips, but is squeezed out along the cutting edges of the tool, forming a thread profile on the part. Taking this into account, the diameters of holes and threaded rods should not be made according to the nominal thread size, but slightly lower than it. For metric threads with a diameter of 6–10 mm, this difference is 0.1–0.2 mm; with a diameter of 11–18 mm – 0.12–0.24 mm; with a diameter of 20–30 mm – 0.14–0.28 mm.

The diameters of holes for the most common metric thread sizes are given in table. 1.

To form a thread entry at the end of the part, it is necessary to chamfer according to the height of the thread profile.

Table 1. Diameters of holes for cutting metric threads

Material	Metric thread diameter, mm
5	6	8	10	12	16	20	24
Steel and brass	4,2	5,0	6,7	8,4	10,1	13,8	17,3	20,7
Cast iron and bronze	4,1	4,9	6,6	8,3	10,0	13,7	17,1	20,5

A tap lubricated with grease is inserted into the drilled hole and, lightly pressing it against the part with the left hand, carefully turn the driver with the right hand until the tap grips the metal and its position in the hole becomes stable. After this, the knob is taken with both hands and rotated with the hands intercepted every half turn (Fig. 10, a).

Rice. 10. Movements when cutting threads: a – with a tap, b – with a die, c – with a die

After one to one and a half turns, the tap, shaking in a horizontal plane, is rotated in the opposite direction by about a quarter or half a turn. This is necessary so that the chips break and move out of the hole along the grooves of the tap without jamming the tap. Having finished cutting, pass it through or turn the knob in the opposite direction to unscrew the tap from the hole.

The second and third taps are lubricated with oil and inserted into the hole without a driver; Only after the tap is correctly installed on the thread, apply the driver and continue threading.

Thread cutting with dies should be done in the same way. Here, however, in addition to circular movements along arrow a (Fig. 10, b), the knob should also apply some downward pressure along arrow c. During the cutting process, it is necessary to ensure that the pressure on both handles is the same.

At the first stage of thread cutting, you should ensure the correct position of the tap and die in relation to the axes of the hole and the rod. The non-parallelism of the axes and their non-perpendicularity to the end of the part are controlled by a square and are eliminated by changing the position of the tool.

It is necessary to cut threads in small and blind holes of small diameter especially carefully, without overloading the tap and often clearing it of chips.

When cutting threads in deep holes, remove the tap from the hole for cleaning (2-3 times).

If it is necessary to obtain accurate and clean threads on rods, then cutting them should be done with roughing and finishing dies.

If thread cutting is performed with dies with sliding dies, then their compression (feed) should be done only at the beginning of the pass. After each pass along the entire length of the threaded rod, the die is driven in the opposite direction and then the dies are again tightened with a screw and the thread is again cut along the entire length of the rod to be cut until the desired thread diameter is obtained. You should not press the dies in the middle of the rod. Using sliding dies, threads are cut in several passes.

To cut pipe threads with a clamp, the pipe must be securely secured in a special pipe clamp (Fig. 10, c).

The cut end of the pipe is lubricated with oil (linseed oil), and then a die is installed at a length of no more than 2–3 threads, bringing the dies closer together so that the thread is cut to the full depth in 2–3 passes. For diameters up to 1” are limited to two passes; with diameters greater than 1”, a good thread can be obtained in only 3–4 passes. Before each repeated pass, the surface of the thread being cut and the thread of the dies must be thoroughly cleaned with a brush from chips and re-lubricated with oil.

The rotation of the clamp around the pipe is usually carried out with a rocking motion in four steps; For each step you need to turn the clamp 1/4 turn.

Threads up to 1½” in ​​diameter are cut by one mechanic; For large thread diameters, two people work together. When working in tandem, a full rotation of the die must also be done in four steps.

Source: https://extxe.com/19086/narezanie-rezby-instrumenty-sposoby-narezanija-rezby/

Thread cutting on a lathe: classification, diagrams

Thread cutting on a universal lathe is a common operation, especially in repair departments. The presence of a lead screw and a large feed range make it possible to cover basic needs without readjustments and special tools - a few threaded cutters are enough. The possibility of mechanized cutting with manual, machine taps, and lechers simplifies setup and speeds up the process while maintaining acceptable quality of fasteners.

Classification

In practice, cutters for external and internal threads with a rectangular section holder are used. Less common are disc, prismatic, sharpened along the front surface. The working profile of all corresponds to the dimensions of the screw groove. In the direction of the cut spiral, left and right ones are released.

There are solid and prefabricated instruments. The first ones are mainly made of high-speed steel, small section or disk. The bulk is equipped with cutting plates secured by soldering with refractory solder or mechanically, allowing replacement when worn.

Threaded cutters: external (Fig. 1), internal (Fig. 2)

Materials

For the manufacture of the cutting part are used:

• high-speed steels;
• hard alloys;
• mineral ceramics;
• superhard tool materials (STM).

The former are used for thread cutting of steels, non-ferrous metal alloys, and plastics. They are distinguished by high strength, thermal conductivity, but lower, compared to others, hardness, red-hardness, wear resistance, which limit the cutting speed.

The largest proportion of thread cutters used are those equipped with carbide inserts. This is due to high durability, hardness, sufficient strength and rigidity, and reasonable cost. Processing productivity is 2-3 times higher than with rapid.

A wide range allows you to select the optimal grade for processing in most cases.

Ceramics are relatively cheap, quite fragile, and are used for processing fine pitch threads of steel and cast iron parts, with a rigid AIDS system, with limited allowance removal per pass.

STMs based on polycrystalline diamond (PCD) or cubic boron nitride (CBN) are extremely hard, heat-resistant, but expensive. Indispensable for precision work on difficult-to-cut materials. PCD is used for cutting copper, aluminum, and tungsten carbide. CBN work on hardened steels and hardened cast irons. Successful application requires high rigidity and smooth running of the equipment.

Decoding the writing of threads

Regulatory documents: GOST, OST, MN for a specific type contain samples of conditional recording.

Graphic materials are designed in accordance with the instructions of GOST 2.311-68 “Image of threads”.

A typical designation structure contains:

• the literal part defining the type;
• numbers corresponding to the nominal size in millimeters or inches;
• pitch (mm) is indicated only as fine, after the “×” sign;
• for multi-start ones, instead of the previous paragraph, the stroke (mm) is given, then the step in parentheses;
• direction: right is the default, left is LH;
• tolerance range or accuracy class;
• make-up length other than normal.

Example 1: М16×1.5LH–6H. Explanation:

• M – metric cylindrical;
• 16 – nominal diameter, mm;
• 1.5 – fine pitch, mm;
• LH – left;
• 6Н – tolerance range, where 6 – degree of accuracy; H – main deviation. Capital letters are used for internal (nuts), hence the threads in the hole.

The screw-in length is not indicated, which means it is normal.

Example 2: G1/2–A

• G – cylindrical pipe;
• 1/2 – thread size, inches; corresponds to the internal diameter of the pipe;
• A – accuracy class.

The designation options are illustrated below.

Thread cutting using lathe equipment

Shaping on the machine is carried out by copying the working profile of the tool onto the part along a helical line. Translational movement is transmitted to the cutter, tap, die, comb. In combination with the rotation of the workpiece, a screw movement is obtained, the tool surface coincides with the cut surface.

Source: https://VseOChpu.ru/nareznye-rezby-na-tokarnom-stanke/

How to cut a thread manually with a tap correctly: tool classification and basic recommendations - Machine

Lathes or drilling machines have been used for cutting threads for quite a long period. They are designed to rotate a workpiece or tool. In almost all cases, the working tool is a tap.

The classification of such a tool is carried out according to a number of different characteristics:

1. 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.
2. 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.
3. 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.
4. Thread cutting tools are also classified according to the type of working surface. Examples include helical, straight or shortened grooves. On sale you can find a version that also has a combined surface. It is suitable for processing metals with low hardness. For hard alloys, a tool with cutting elements arranged in a checkerboard pattern is used.

: Gray color in the interior - let's analyze it thoroughly

Drill selection

An electric drill is necessary to perform internal threading work.

Before cutting a thread with a tap, you must first drill a hole for it. It is absolutely clear that the diameter of the hole should be smaller than the size of the tap, but how much? There is a universal way to calculate this difference. Any thread is characterized by two parameters:

• diameter, indicated on instruments with a capital letter M in front, for example, M6;
• The pitch of turns is written as a number after the first parameter, for example, M6x1.

By looking at the markings on the tap, it is easy to select the drill for the job. It is necessary to subtract the thread pitch from the diameter value; in the given example, M6x1, you will need a hole measuring 6 - 1 = 5 mm.

The drill should be a regular cylindrical one; for metal processing, these are made from high-speed steel R6M5.

In order to facilitate the selection of sizes, Table 1 presents the recommended diameters for the holes of the most common metric profile threads.

Table 1

Marking	M3	M4	M5	M6	M8	M10
Hole D, mm	2,5	3,3	4,2	5	6,75	8,5

Since we are talking about manual metal processing, one feature should be taken into account when selecting drills.

When working with an electric drill, no matter how hard you try to keep it level and motionless, the hole will break and its size will be slightly larger than necessary. As a result, after passing with a tap, the thread turns will have a cut profile.

When the bolt is screwed in, there will be some play, and if the tightening torque is high, the coils may simply become deformed. The size of the hole depends on two factors:

Countersinks are needed for chamfering when cutting internal threads.

1. The larger the diameter, the more the hole unfolds. For example, with D = 5 mm there is an increase of 0.08 mm, and with D = 10 mm there is already an increase of 0.12 mm.
2. Working conditions. The mechanic may be in an awkward position or at a height, this will cause increased hole breakdown, which will then affect the quality of the connection.

The problem is solved as follows: to make the internal thread full-profile, you must initially take a drill whose diameter is 0.1 mm less than the required one. It is possible that in some cases it will be difficult to rotate the tap, but usually no difficulties arise.

Preparation of tools

To perform internal thread cutting you will need:

• marking tools (tape measure, ruler, pencil);
• electric drill with a set of drills;
• countersink for chamfering;
• set of taps with hand crank;
• hammer;
• core

Drills should be threaded (sharpened) in accordance with the hardness of the material being processed. The harder it is, the greater the sharpening angle needs to be maintained. During drilling and cutting, the working parts of drills and taps must be lubricated. The choice of lubricant type depends on the viscosity of the steel. For regular and carbon steel, old lard or grease is suitable, for stainless steel - machine oil.

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?

Tapping internal threads is a precise technological process that is carried out in a certain sequence.

Preparation

Initially, you need to prepare tools and additional devices for the work:

1. Small vice.
2. Electric drill with speed controller, metal drills.
3. Set of taps.
4. Metal brush.
5. Core with a hammer.

• Thread cutting with a tap is carried out manually at low speeds of the power tool.
• Tapping internal threads

Slicing process

Step-by-step thread cutting instructions:

1. Drill the hole with a core and a hammer.
2. Drill a hole with an electric drill. Hold the equipment exactly perpendicular to the surface being processed. Additionally, lubricate the drill with special oil.
3. Chamfer 1 mm in depth. To do this, use a drill of a larger diameter.
4. Secure the equipment in the collar. Perform two movements forward, one movement back. This way the metal shavings will come out of the hole and there will be no problems with cutting. Movements should be smooth.

During manual cutting, you must not apply pressure or continue to rotate the tool after it gets stuck. If it breaks, you need to drill out the tap using a drill or various metal drills. Another option for removing the fragment is to grind the area around the hole using a grinding machine. Then you need to remove it with pliers.

To create threaded connections, you need to buy the appropriate documents and learn how to work with them. By carrying out the work carefully, without haste, you can get a reliable connection in a short period of time.

Source: https://regionvtormet.ru/prochee/kak-narezat-rezbu-metchikom-vruchnuyu-pravilno-klassifikatsiya-instrumenta-i-osnovnye-rekomendatsii.html

How to cut threads by hand

Threaded connections are widely used in various mechanisms and machines. Bolts, studs, screws, nuts are universal, interchangeable fasteners. However, there are times when it is necessary to cut threads by hand. A specialized tool will help you do this job efficiently.

• External thread cutting with a die
• Tapping internal threads

In mechanical engineering, there are three main systems of fastening threads: metric, inch and pipe.

Metric thread has become the most widespread. It has a triangular profile with an angle of 60˚. Its main parameters, diameter and pitch, are expressed in millimeters. Designation example: M16. This means that the thread is metric, has a diameter of 16 mm with a coarse pitch of 2.0 mm. If the step is small, then its value is indicated, for example, M16 * 1.5.

The diameters of inch and pipe threads are expressed in inches. The pitch is characterized by the number of threads per inch. The specified parameters are standardized, so it is always possible to select the necessary tool.

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 cut thread within 0.10.25 mm. However, they have reduced rigidity, which affects the accuracy of the resulting profile.

Operating procedure

The die is installed in a die holder of a suitable size. After this, it is secured with screws. In the case of external pipe threads, die holders with a ratchet are often used. They provide convenience for working in hard-to-reach places, such as near a wall.

The thickness of the rod is chosen to be 0.10.25 mm less than the diameter of the external thread. For example, for M6 with a large pitch it is 5.805.90 mm; M8 – 7.807.90 mm; M10 – 9.759.85 mm. Measurements are taken using a caliper. The diameters of rods for cutting metric threads of average accuracy class 6g are presented in the table.

To ensure better insertion of the die, a chamfer is filed at the end of the rod. Its width should be 1 - 1.5 mm for M6 M18. The workpiece is lubricated with machine oil, which makes subsequent work easier and allows you to obtain a better surface.

The die is placed on the end of the rod so that its plane is perpendicular to the axis of the bolt being cut. Next, with slight pressure, rotate the die holder clockwise (if the thread is left-handed, then counterclockwise). When the die cuts into the rod by one or two threads, it should be turned back half a turn for better removal of chips. After this, they again make 1-2 turns along the thread and 0.5 in the opposite direction. Using this scheme, the bolt is cut to the required length.

The diameter of the external thread is checked with a regular nut or ring gauge. If necessary, the pitch is controlled with a thread gauge.

Tapping internal threads

To form an internal thread, the following tools and materials are required:

• hammer, center punch, drill, drill bits;
• a set of taps, a driver, a bench vice;
• machine oil.

Tapping technology

The first step is to mark the workpiece and core the center of the future hole. Select a drill corresponding to the required thread diameter. This can be done using lookup tables or approximately using the formula d = D – P. Here D is the thread diameter, P is its pitch, d is the drill diameter. For example, for M10 d = 10 – 1.5 = 8.5 mm.

Step, P

2	0,4	1,6
3	0,5	2,5
3,5	0,6	2,9
4	0,7	3,3
5	0,8	4,2
6	1	5,0
0,75	5,25
0,5	5,5
8	1,25	6,8
1	7,0
0,75	7,25
0,5	7,5
10	1,5	8,5
1,25	8,8
1	9,0
0,75	9,25
0,5	9,5
12	1,75	10,2
1,5	10,5
1,25	10,8
1	11
0,75	11,25
0,5	11,5
14	2	12,0
1,5	12,5
1,25	12,8
1	13,0
0,75	13,25
0,5	13,5
16	2	14,0
1,5	14,5
1	15,0
0,75	15,25
0,5	15,5
18	2,5	15,5
2	16,0
1,5	16,5
1	17,0
0,75	17,25
0,5	17,5
20	2,5	17,5
22	2,5	19,5
24	3	21
27	3	24
30	3,5	26,5

A hole is drilled into the part to the required depth, which must exceed the length of the part being cut. Using a drill with a diameter larger than d, a chamfer is made on the edge of the hole. It serves for centering and better entry of the tap.

The cutting tool is selected based on the main parameters of the thread - diameter and pitch. As a rule, a set of two taps is used. One of them is rough, the other is finishing. The driver is selected according to the size of the square of the tail part of the taps.

The part is securely secured in a vice. The rough tap and hole are lubricated with machine oil. After this, install the tap strictly perpendicular to the surface of the part and, pressing along its axis, rotate the knob by the handles.

After cutting one or two threads, make a quarter turn in the opposite direction. This promotes chip crushing and removal and prevents tool jamming. The work continues, carrying out alternating rotation: ½ turn forward, ¼ turn back. In this case, it is necessary to ensure that there is no skew of the tap. You should also not apply excessive force to it. To prevent jamming, the cutting tool is periodically removed and the hole is cleared of chips.

After cutting the internal thread to the required depth, a finishing tap is installed in the hole. When it goes in the given direction, a crank is put on it and work continues. Add lubricant periodically.

The thread is checked using a plug gauge or bolt. It should screw in effortlessly and not wobble. If necessary, make an additional pass with a finishing tap.

Source: https://tehnouzel.ru/tehnologii-remonta/kak-narezat-rezbu.html