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There are situations where a reliable connection cannot be made using welding machine. In such cases, threaded connections are used. It allows you to assemble and disassemble metal structures without deformation. However, to create a connection you need to know how to properly cut a thread with a tap.
Types of instruments
The tool that is used to create threads is called a tap. These are cylindrical metal rods, on the edges of which there are sharp incisors located in a certain sequence. Taps are divided according to several factors:
- Method of use. A special wrench for carrying out the work is supplied with hand tools. Tooling for machine tools is secured in the chuck thanks to a cylindrical shank.
- According to the type of holes being machined. Devices are divided into two groups. Some are used for processing through holes, others for the deaf.
- For cutting internal, metric and pipe threads.
The shape of the taps can be either cylindrical or conical.
Design features of the tool
If you need to cut a thread, before doing this you need to understand what types of taps can be found in a hardware store:
- Straight and screw devices are distinguished. A separate group are cylindrical rods, on which special grooves are cut to remove metal shavings from the hole.
- Another division by design is universal, complete tools. The first option consists of taps, the working part of which is divided into three zones. They are needed for sequential coarse, medium, and finishing processing of the inside of the hole. The second option consists of sets of metal cylinders, each of which is responsible for its own type of thread cutting.
To obtain a better connection, you need to choose a set of taps. Separate devices allow you to process metal more accurately and are less vulnerable to high force. They are distinguished by reliability, durability, and high accuracy.
How to correctly determine the hole diameter?
If you take a large-diameter drill, make a hole, and take a tap of the same diameter, problems may arise. Before you start cutting threads, you need to select the size of the equipment and the required hole diameter. For classic sizes drills if there is a special table that indicates the size ratios. You can find it on the Internet.
How to cut a thread with a tap?
Cutting internal thread the tap is accurate technological process which is carried out in a certain sequence.
Preparation
Initially, you need to prepare tools and additional devices for the work:
- Small vice.
- Electric drill with speed controller, metal drills.
- Set of taps.
- Metal brush.
- Core with a hammer.
Thread cutting with a tap is carried out manually at low speeds of the power tool.
Slicing process
Step-by-step thread cutting instructions:
- Drill the hole with a core and a hammer.
- Drill a hole with an electric drill. Hold the equipment exactly perpendicular to the surface being processed. Additionally, lubricate the drill with special oil.
- Chamfer 1 mm in depth. To do this, use a drill of a larger diameter.
- 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 a fragment is to grind the area around the hole using grinder. 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.
A variety of tools can be used for cutting threads, among which we highlight a tap. It is used to create a threaded surface designed to accommodate a screw, stud, bolt, or other fastener. Relatively low cost and ease of use determined wide use the subject hand tools. Let's take a closer look at how to properly cut a thread with a tap at home.
Classification of taps and their scope of application
Lathes or drilling machines have been used for cutting threads for quite a long period. They are designed to rotate 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:
As a rule, high-quality tool steel is used in the manufacture of tools. She can withstand long-term operation, do not heat up during operation. Tap High Quality It has a strict geometric shape and looks neat. A similar tool is often used for cutting metric threads, but there are versions for producing inch threads. The shape of the base can be cylindrical or conical.
Preparatory stage
To ensure that the work of obtaining threads does not cause many difficulties, careful preparation should be made for such a technological operation. All applied methods related with internal threading, provide that a hole of the required diameter has already been obtained in advance. Get standard size thread is possible when creating a hole according to the correspondence table. For example, for an M10 thread, a hole with a diameter of 8.5 mm is created.
There is often a situation where you should get a thread custom size. In this case, the required hole diameter is calculated using a universal formula. Calculations are carried out as follows:
- The marking of the tool used is studied. You need to pay attention to the type of thread being cut, pitch and diameter.
- The required hole diameter when using an M5X0.75 tap can be determined as follows: 5−0.75=5.25 mm.
The easiest way to carry out the work is when you need to get a standard thread, since all necessary information can be taken from various tables of regulatory documentation.
To get a quality hole, you need to choose the right drill. When drilling, it is recommended to use equipment that prevents runout during operation. When choosing a drill, it is worth remembering that it must have high-quality sharpening. Experts recommend selecting the sharpening angle depending on the hardness of the material being processed. With increasing hardness The recommended sharpening angle also increases, but it should not exceed 140 degrees.
Required Equipment
Tapping threads by hand only possible with the following tools:
After finding everything you need, you can begin the actual work.
Features of the technology used
Carry out the work in question you can do it yourself living conditions. To do this, you need to consider the recommendations below:
It is not recommended to apply a large load to the handle by using a lever or a gas wrench. Do not forget that the tap may burst due to high load, then remove the remaining the inside part will be quite difficult. IN While working, the master must feel how the tool moves: easily or with great effort. The shape of the cutting edge does not allow removal of chips from the working part at the moment of rotation along the thread.
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. The cross-section of a metric thread is an equilateral triangle, and an inch thread is an isosceles one.
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, affecting the process of cutting connecting elements.
- If the thread is intended to be connected to a finished part, its geometric dimensions must be appropriate.
- When manufacturing complete fasteners, it is recommended to use the metric type.
- 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. She may be various shapes- round, square or hexagonal. If the work is carried out at home, you will need a vice to fix the part.
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.
- Having secured the workpiece in a vice, the correctness of its location is checked.
- Installing the die into the die holder. Its surface must be in the same plane as the surface of the workpiece end.
- The first turn is performed with little effort. It is important to make turns in the right direction.
- Having reached the lower limit, the die must be turned in the opposite direction.
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 manual view tap. For large sizes mechanical processing is required using .
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. This way you can avoid mechanical damage details. The formed thread must have the same geometry along its entire length. Otherwise, the connection strength may be lost.
— actual question, because this is the main method for connecting structural elements.
This can be done manually using a special device.
External and internal cutting of the part is separated, thanks to which the thread can be installed in holes of different types.
The cutting method depends on the type of material you will be working with.
You will find the features of the process, as well as a description of the tools that are needed for this, in the article, and the video will help you cope with the task.
Tapping tap
A tap is a metalworking and turning cutting device made in the form of a rod with a cutting element mounted on it.
The cutter is used to create internal threads in various metal parts, pipes, and it can also be used to restore previously damaged threads.
The cutter has a working part and a tail part. The working part includes two sections: for cutting and for calibration.
The cutting section is usually cone-shaped and is responsible for direct thread cutting.
In this area, cutting teeth are also installed, which cover the area along the entire circumference. The calibration section is responsible for the final formation of the part.
It looks like a cylinder equipped with teeth and continues as a cutting area.
It is longer, and its working element is divided by grooves needed to create cutters and remove chips.
The number of grooves depends on the size of the tap with the clamp - in devices not exceeding 22 mm, there are usually three of them. There are also special taps that do not have grooves.
In those devices where they are, the grooves can be straight or helical.
The back of the tap has a cylindrical shape, at the end there is a square, which is necessary for the possibility of fixing to the fastening tool.
This part of the tap is responsible for attaching the device to the hand holder or machine chuck.
Taps with clamps come in two types: manual or machine. Handheld devices attached to hand holders and are designed to create internal threads.
Machine tools are installed on chuck holders of lathes.
Before you learn how to cut a thread with a tap, you need to decide on its type. The threads that can be made may vary depending on the type of device.
The most common form of thread is metric - it is made using a metric tool.
To create threads with inside In a water pipe, as well as in a heating pipe, specialized pipe taps are used; they can also be used to make reinforced threads in metal parts, and not just in heating elements.
To create a tapered or inch thread, you need to use a special inch tap, which allows you to make threads of the smallest size.
Most often you can find durable steel devices with a clamp - they are the most efficient, strong and durable.
In addition to the type of thread, taps differ in design: they can be single or complete.
The latter are used to create threads in several passes. Typically, the kit includes two taps, one of which is called finishing, and the second is called rough.
In some cases, a tap is added here for medium processing. The number of parts in the kit is always indicated on the back, on the tail part.
The complete taps are not the same; they have different tooth shapes: the rough tap has the shape of a trapezoidal tooth, the middle tap has a triangular shape with a rounded apex, and the finishing tap has a standard triangle with a sharp tip.
Threading involves creating a protrusion in a hole, and the protrusion line should have a helical shape.
The protrusion near the wall in the hole must meet the specified parameters in order for the thread to be used: it must have the correct pitch, lifting angle, outer and inner diameter, etc.
Another important parameter is the depth, which is determined based on the diameter of the threads inside and outside the pipe.
There may be several options for how to cut a thread correctly.
The direction of the thread in the pipe can be different, depending on the need: it can be directed to the right, in which case the protrusion develops clockwise, or it can be left-directed, in which case the protrusion will follow counterclockwise.
There are two possible profile shapes: rectangular or triangular, as well as special additional shapes, but they are used mainly in production, and almost never at home.
Tap selection and cutting
A tap is selected depending on the thread that is needed, as well as its purpose (the thread may differ in profile shape, thread pitch, tolerances).
To select a tap, there is a table that shows the accuracy classes - in accordance with them, you need to choose what type of tap to purchase - a set or a single tool.
An important factor to consider when choosing a tap is the required accuracy of profile cutting.
Different tools have different finishes on the cutting element, and this also needs to be taken into account.
The metal you will be working with will directly affect the tap you will need for it.
On aluminum, a sharpening angle of at least 25 degrees will be required, on cast iron and copper up to 5 degrees will be enough, and on steel – up to 10 degrees.
For the manufacture of the tap itself, ordinary or high-strength steel is most often used. When choosing, you need to focus on the diameter of the hole in which the thread will be made.
Before creating threads in aluminum, cast iron or other metal part you need to make a hole. It can be through or blind, depending on the need.
The hole can have any diameter, it is only important that it be smaller than the future cutting. It is best to choose a drill bit for the hole based on the thread size.
There is a special table that shows the recommended drill diameter in accordance with the thread size; it is recommended that you familiarize yourself with it before starting work.
If you need to make a large wall thread on cast iron or aluminum, then you should choose the diameter for the hole by multiplying the thread diameter by 0.8, so you will get a value that will be closest to the required size.
Creating a hole for an internal thread is not done manually, but using a special drilling machine, or electric drill.
If using a drill, the workpiece must first be clamped in a vice so that the drilling location is exactly where it is needed.
When drilling, the drill must be positioned strictly vertically and not deviate from the specified plane.
To make it easier to work with a tap, you can chamfer the top edge - then the device will fit easier.
This can be done using a drill with a larger diameter or a file. After finishing the work, the hole must be cleared of chips.
This must be done especially carefully in a blind hole, otherwise cutting will not work well.
Before drilling, the part you will be working with must be firmly secured using a vice, with the chamfer on top, and the axis of the hole you made must be perpendicular to the table.
The tap must be fixed into the socket of the driver, and then inserted into the chamfer of the workpiece hole. The device is always inserted vertically.
After this, you need to press the tap firmly against the workpiece (preferably with both hands) and begin to rotate it clockwise.
Sudden movements or stops should not be allowed: the device must be rotated slowly and evenly, but at the same time work with pressure.
You need to work with the tap in the following sequence: first two turns forward, then half a turn back and then forward again. This method involves processing the entire hole in the pipe.
The tap needs to be cooled from time to time while cutting.
For different metals are used different ways cooling: kerosene will be effective for aluminum, turpentine for copper, a special emulsion for other metals, and when cutting in cast iron, cooling the device is not required.
For internal threading, it is best to use tap sets.
The work is as follows: first you need to make a rough thread, then use a medium tap, which is passed through the hole, and then the final cut is formed using a finishing tap.
This sequence is optimal for best quality processing, so it is recommended not to skip any of the three devices, otherwise the quality of the thread in the pipe will be noticeably worse.
You can see all the stages of the cutting process in the video - there is nothing complicated in this process, the most important thing is to choose the right diameter and follow the sequence of work, and also remember how to work with this or that type of metal.
In this case, you will receive high-quality threads in the pipe, which can be used to connect any parts.
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The question of how to cut the thread of a bolt or nut is far from idle. During repairs, apartment and house owners are faced with the need to restore old threads of anchors, bolts, nuts, or simply threads found in metal plates.
Or you may even need to cut a new thread on the bolt or nut. For professional turners or mechanics, this task does not present any difficulties, but those who have never encountered such a process need to arm themselves with some theoretical knowledge which are presented in this article.
Before you start practical actions When cutting threads, you need to know its basic parameters and types. In the construction and renovation of housing, metric threads are used in most cases. What does it mean? According to the shape of the tooth, the thread can be metric, inch, rectangular, trapezoidal, etc.
Characteristics of metric thread
The thread we are interested in has the shape of a triangle, while the trapezoidal thread has the shape of a trapezoid. In addition, there is such a thing as a thread pitch, that is, the distance between its vertices: in the case of a metric thread, between the vertices of the thread triangle. And, of course, the characteristics of the thread include its diameter.
Let's look at the paragraph described above using the M 12 thread as an example, where the letter “M” indicates that the thread is metric, the number “12” determines the diameter of the thread. Where is the step size? The fact is that metric threads are divided into main and small, and if there is no other digital value after the number, it means the main thread. But if we have a thread M12 x 1.5 or M 12 x 1.25, then this means that the thread pitch is 1.5 and 1.25 mm, respectively. The pitch of the main thread M 12 is 1.75 mm.
All these values for any type of thread can be found in reference books or on the pages of the corresponding websites on the Internet. For internal threads (nuts), there is another reference value - the diameter of the thread hole, which can be found there. For our M12 bolt, the internal diameter of the nut should be 12 mm minus the height of the tooth profile, that is, according to the reference books, 10.2 mm. For small thread M 12 x1.25, the diameter will be correspondingly smaller - 10.4 mm.
It is worth noting that something similar applies to a bolt or, as it is called in reference books, a rod. Again, for an M 12 thread, the diameter of the rod should be slightly less than 11.7 mm, but for an M 12 X 1.25 thread - 11.9 mm. If you do not comply with the dimensional tolerances for the threads for both the nut and the bolt, the thread will be of poor quality, weakened on one side, and on the other, if the tolerance is larger, it will simply break.
Accessories and tools for thread cutting
Don’t be afraid of the word “equipment” because, in fact, this is a device where it is attached cutting tool: taps and die (die). The old name of the die is given in parentheses, but it can still be found. The equipment includes wrenches of a fairly simple design into which a tap is inserted for cutting threads in nuts and another type of device where a die for cutting bolt threads is attached.
Accessories and cutting tools for thread cutting
Taps, as well as dies, are made of high-carbon cast iron, so they are fragile and susceptible to heavy loads. Threading in nuts is mainly carried out by two taps: N 1 and N 2. The first has an incomplete thread for preliminary penetration, following which the second tap makes the cut.
Taps for thread cutting
As a result, the thread is full and of high quality, which means it will firmly hold the connection with the nut. Another type of tap is used, called a "machine" tap, which combines two tap numbers.
Die holder and die set
It would seem convenient, but this type of tap is long and inconvenient to use. Used for cutting long threads. As for the dies, they have one number.
Another type of equipment, without which the thread cutting process is almost impossible, is a medium-sized bench vise. What this is, probably, no one needs to explain. The only thing to remember is that the vice must be securely fastened.
Threading techniques
It is immediately necessary to make a reservation that the rod at the end and the threaded hole in the nut must be chamfered using any in an accessible way. Chamfers are necessary for precise entry without distortion of the cutting tool, that is, the tap and die. Next, we clamp the thread cutting object into the driver, clamp the rod or workpiece under the nut from a vice and proceed to thread cutting.
Thread cutting with a die
This is done without the use of excessive force and always with a lubricant, for which sulfo-fresol is ideal. However, if this is not available, you can use an emulsion (a solution of mineral oil in water) or simply vegetable oils.
By the way, if you decide to cut the thread of a bolt made of stainless steel or copper, there is no better lubricant than ordinary lard, which has been tested more than once in practice.
When cutting a thread, you need to feel the tap or die: if they begin to spring a little, that is, resist strongly, you need to unscrew them and clear them of chips. If this is neglected, the cutting tool may simply crack and you will have to prepare a new rod or blank for the nut again.
And finally: if you do not have the opportunity to order blanks for a bolt or nut from a turner, purchase (rolled metal in the form of a circle), which can have a diameter from five to 20 mm, and you don’t need more, because it is almost impossible to cut large-diameter threads by hand.