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 optical device This is too large a parameter, so a step 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 like a set of dies (for external thread) 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. Both taps and dies are clamped into special devices– knobs (3), the size of which must be suitable for the tool used.
Tools for cutting threads must be of high quality and sharp. With a dull rusty tap good carving it will be impossible to cut, and there is a high probability that it will break in the first hole, and in this case more problems will be 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 required thread, 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 reverse side. This is how the entire required thread length is passed until the work is completed.
Internal thread cutting
First, a hole is drilled in the workpiece required diameter and chamfer for tool entry. 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 internal thread is required, do not long length, then in this case a hole is drilled that is longer than the thread, 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.
- 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, then you need to make sure that the die easily passes through 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 it cutting edges. Then the fragment is pulled out with tweezers or knocked out from the other side of the hole (if it is through).
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 is outlined in this article.
Before you begin the practical steps of thread cutting, you need to know its basic parameters and types. In the construction and renovation of housing, metric threads are used in most cases. What does it mean? According to the shape of the tooth, the thread can be metric, inch, rectangular, trapezoidal, etc.
Characteristics of metric thread
The thread we are interested in has the shape of a triangle, while the trapezoidal thread has the shape of a trapezoid. In addition, there is such a thing as a thread pitch, that is, the distance between its vertices: in the case of a metric thread, between the vertices of the thread triangle. And, of course, the characteristics of the thread include its diameter.
Let's consider the paragraph described above using the example of the M 12 thread, where the letter “M” indicates that the thread is metric, the number “12” determines the diameter of the thread. Where is the step size? The fact is that metric threads are divided into main and small, and if there is no other digital value after the number, it means the main thread. But if we have a thread M12 x 1.5 or M 12 x 1.25, then this means that the thread pitch is 1.5 and 1.25 mm, respectively. The pitch of the main thread M 12 is 1.75 mm.
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 turn them out 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 of five to 20 mm, and you don’t need more, because it is almost impossible to cut large-diameter threads by hand.
To cut an internal thread on a part, you must first drill a hole. Its size is not equal to the thread diameter, but should be slightly smaller. You can find the diameter of the drill for the thread in a special table, but to do this you also need to know the type of thread.
Main settings
- diameter (D);
- pitch (P) - the distance from one turn to another.
They are determined by GOST 1973257-73. A large step is considered normal, but it corresponds to several smaller ones. A small pitch is used when applying to thin-walled products (pipes with a thin wall). They also make a small turn if the applied thread is a way to adjust any parameters. Also, a small step between turns is made to increase the tightness of the connection and to overcome the phenomenon of self-unscrewing of the part. In other cases, a standard (large) step is cut.
There are many types of threads, since each has its own formation characteristics; the diameter of the hole for the thread is different in each case. All of them are prescribed in GOST standards, but most often they use triangular metric and conical metric threads. We will talk about them further.
We usually see triangular threads on bolts and other similar fasteners, conical threads on most sanitary products, suggesting a detachable connection.
Adaptations
To apply carvings with your own hands, use small devices:
All these devices are made of alloys characterized by increased strength and abrasion resistance. Grooves and grooves are applied to their surfaces, with the help of which their mirror image is obtained on the workpiece.
Any tap or die is marked - they have an inscription on them indicating the type of thread that this device cuts - diameter and pitch. They are inserted into holders - collars and die holders - and secured there with screws. Having clamped the thread cutting device in the holder, it is put on/inserted into the place where you want to make a detachable connection. By turning the device, turns are formed. How correctly the device is positioned at the beginning of work determines whether the turns will “lay down” evenly. Therefore, make the first revolutions, trying to keep the structure level, avoiding shifts and distortions. After a few turns have been made, the process will go easier.
You can cut small or medium diameter threads by hand. Complex types (two- and three-way) or working with large diameters by hand are impossible - too much effort is required. For these purposes, special mechanized equipment is used - lathes with taps and dies attached to them.
How to cut correctly
Threads can be applied to almost any metals and their alloys - steel, copper, aluminum, cast iron, bronze, brass, etc. It is not recommended to do it on hot iron - it is too hard, it will crumble during operation and it will not be possible to achieve high-quality turns, which means the connection will be unreliable.
Tool for the job
Preparation
You need to work on clean metal - remove rust, sand and other contaminants. Then the place where the thread will be applied must be lubricated (except for cast iron and bronze - they must be worked “dry”). There is a special emulsion for lubrication, but if it is not there, you can use soaked soap. You can also use other lubricants:
You can often hear advice to use machine or mineral oil or even lard when cutting threads. They work well, but experts say that it is better not to do this - the chips will stick to the viscous substance, which will lead to rapid wear of the tap or die.
Slicing process
When cutting external threads, the die is placed strictly perpendicular to the surface of the pipe or rod. During operation, it should not wiggle, otherwise the turns will turn out uneven and the connection will be ugly and unreliable. The first turns are especially important. How they “lay down” determines whether the connection will then be skewed.
By applying the internal thread, the part is fixed motionless. If it is a small piece, you can clamp it in a vice. If the plate is large, ensure its immobility using available methods, for example, by fixing it with bars. M
The tap is inserted into the hole so that its axis is parallel to the axis of the hole. With little effort, little by little, they begin to twist in the given direction. As soon as you feel that the resistance has increased, unscrew the tap back and clear it of chips. After cleaning, the process continues.
Photo cutting process
When cutting a thread in a blind hole, its depth should be slightly greater than required - this excess should include the tip of the tap. If this is structurally impossible, the tip of the tap is cut off. At the same time, it is not suitable for further use, but there is no other way out.
In order for the turns to be of high quality, two taps or dies are used - rough and finishing. The first pass is done as a rough pass, the second as a finishing pass. There is also combined devices for threading. They allow you to do everything in one pass.
Another practical advice: to prevent chips from falling into work area, when cutting, make one full turn clockwise, then half a turn counterclockwise. After this, return the tool to the place where you stopped and make one revolution again. Continue this way until the required length.
Tables for selecting the diameter of a drill for threading
When making an internal thread, a hole is pre-drilled for it. It is not equal to the diameter of the thread, since when cutting, part of the material is not removed in the form of chips, but is squeezed out, increasing the size of the protrusions. Therefore, before application, it is necessary to select the diameter of the drill bit for the thread. This can be done using tables. They are available for every type of thread, but here are the most popular ones - metric, inch, pipe.
| Metric thread | Inch thread | Pipe thread | |||||
|---|---|---|---|---|---|---|---|
| Thread diameter, inches | Thread pitch, mm | Drill diameter, mm | Thread diameter, inches | Thread pitch, mm | Drill diameter, mm | Thread diameter, inches | Threaded hole diameter, mm |
| M1 | 0.25 | 0,75 | 3/16 | 1.058 | 3.6 | 1/8 | 8,8 |
| M1.4 | 0,3 | 1,1 | 1/4 | 1.270 | 5.0 | 1/4 | 11,7 |
| M1.7 | 0,35 | 1,3 | 5/16 | 1.411 | 6.4 | 3/8 | 15,2 |
| M2 | 0,4 | 1,6 | 3/8 | 1.588 | 7.8 | 1/2 | 18,6 |
| M2.6 | 0,4 | 2,2 | 7/16 | 1.814 | 9.2 | 3/4 | 24,3 |
| M3 | 0,5 | 2,5 | 1/2 | 2,117 | 10,4 | 1 | 30,5 |
| M3.5 | 0,6 | 2,8 | 9/16 | 2,117 | 11,8 | - | - |
| M4 | 0,7 | 3,3 | 5/8 | 2,309 | 13,3 | 11/4 | 39,2 |
| M5 | 0,8 | 4,2 | 3/4 | 2,540 | 16,3 | 13/8 | 41,6 |
| M6 | 1,0 | 5,0 | 7/8 | 2,822 | 19,1 | 11/2 | 45,1 |
| M8 | 1,25 | 6,75 | 1 | 3,175 | 21,3 | - | - |
| M10 | 1,5 | 8,5 | 11/8 | 3,629 | 24,6 | - | - |
| M12 | 1,75 | 10,25 | 11/4 | 3,629 | 27,6 | - | - |
| M14 | 2,0 | 11,5 | 13/8 | 4,233 | 30,1 | - | - |
| M16 | 2,0 | 13,5 | - | - | - | - | - |
| M18 | 2,5 | 15,25 | 11/2 | 4,33 | 33,2 | - | - |
| M20 | 2,5 | 17,25 | 15/8 | 6,080 | 35,2 | - | - |
| M22 | 2,6 | 19 | 13/4 | 5,080 | 34,0 | - | - |
| M24 | 3,0 | 20,5 | 17/8 | 5,644 | 41,1 | - | - |
Once again, please note that the diameter of the drill bit for the thread is given for large (standard thread).
Table of rod diameters for external threads
When working with external threads, the situation is very similar - part of the metal is extruded rather than cut off. Therefore, the diameter of the rod or pipe on which the thread is applied should be slightly smaller. How accurate - see the table below.
| Thread diameter, mm | 5,0 | 6 | 8 | 10 | 12 | 16 | 20 | 24 |
|---|---|---|---|---|---|---|---|---|
| Rod diameter, mm | 4,92 | 5,92 | 7,9 | 9,9 | 11,88 | 15,88 | 19,86 | 23,86 |
The main task of the mechanic is to create a hole in the metal thickness with the subsequent formation of hollows from the inside. They need to be made so that the turns fit the bolt, stud or other fastener.
A threaded element may be needed in everyday life for the most durable connection of two parts. Here it is necessary to achieve maximum cleanliness - so that there are no shavings, deformations, or broken threads left. It is also very important to follow GOST standards for the size of the device. The diameter should match the screw that will go inside.
Many parameters are important - the type of material, its density, as well as condition, for example, temperature, the presence of corrosion. First you need to prepare the workpiece - remove excess dirt. Then you need to select the right tool, and only then begin metalworking in two or three stages - from roughing to finishing.
Several parameters matter:
- hole diameter;
- cutting depth;
- number of threads (these are entries, the most common is the presence of three cavities);
- pitch, that is, the distance between two furrows.
How internal threads are cut - general information
The device is called a tap. It can be of two varieties - manual and machine, in accordance with the methods of making furrows. The material that is processed is metal, but not only it. There are also lightweight models that cut into plastic or wood. The last option cannot be called the most common.
Factories use mechanized technology - metal drills make through holes (or a blind cavity), and after the blade, several turns are applied with a predetermined pitch. The advantage of this processing is high accuracy. Calculations are made using computer programs for computer-aided design, the data is then entered into the control module - manually or using CNC. The second advantage is that skew of the spiral angle and errors are virtually impossible.
But at home and in small industries, a simpler, but less accurate procedure is often used - manually cutting internal threads with a tap. The work can be carried out on site; for this you need to buy the device itself and a drill to make a preliminary hole.
The instrument resembles a Christmas tree in shape due to the fact that working surface– ribbed blade. Structurally, the product is a rather complex configuration made of tool steel. This material is used because of its strength and ability to process most alloys, even cast iron. It is not very good to work only with hardened metal - it has internal stresses, therefore it is considered fragile and can crumble during the cutting process.
Types and areas of application of taps
According to the drive method, they are divided into:
- Tame - they have a tail square section, which is inserted into the knob. There are two handles that make it convenient to turn the product. It is important not to allow distortion. This result can only be corrected by drilling and cutting a larger diameter.
- Machine - used on metal cutting machines. They are firmly fixed in the holder, accurate, and do not allow deviations.
By cutting method:
- Universal. Their design can be called classic. A tool with a running gear (its length determines the depth of insertion of the screw later if the hole is not through), which is divided into sections. Each of them has certain geometric parameters - angle, direction, distance, step. There are usually three of them, each designed for rough metalworking, intermediate and finishing. Thus, you can achieve the most accurate result with one movement.
- Complete. The name speaks for itself. You will need a set of 3 taps, since you need to make an internal thread with high accuracy. First, the coarsest tool is used, then a finer one, and finally - with grinding and sharpening of the smallest corners. Buying a set is more expensive, but the result is much higher quality.
By hole type:
- For through. They are distinguished by a long working part. It gradually expands, moving into the working area, which is responsible for precise cutting.
- For the deaf. On the cutting section, calibrating turns immediately begin. Therefore, it is very important to sharpen them or promptly change the set as they wear out.
According to the groove design:
- straight – I work well with soft alloys;
- screw, their working area is staggered, they can easily pass even through cast iron;
- shortened - removes chips well.
The shape of the product resembles a cone (full or truncated) or a cylinder. They also all differ in diameter.
Technology: how to use a thread tap
There are several stages, each of which is important. These are preparatory procedures, 1, 2, 3 or more approaches of rotation, finishing grinding. We'll talk more about preparation below. The manipulation of the tool itself is relatively simple. It is necessary to direct the tip, set it level, and then use the wrench to make rotational movements.
- We do not recommend starting to cut unprepared workpieces. If you already have a sheet of metal, where through hole obtained by stamping or other metalworking, it is necessary to drill it out and then countersink it - cut off the edges.
- Remove the top 0.5 cm of chamfer from the sample. This must be done at an angle of 60 degrees.
- The tool must be lubricated and cooled during the process, otherwise additional heat treatment will result, during which metal surface may gain additional strength.
- Make a reverse move every 1-2 turns. This allows you to clear the working area from chips sticking to it.
Let's watch the video. It shows not only working with a tap for cutting internal threads, but also with a die for external threads:
Preparatory procedures
The beginning of any work is the choice of material and tools. The workpiece must have a hole. The worst processing options are those obtained by casting or stamping. It is better if pressure or melting was applied. But in any case the most suitable conditions are created during fresh metalworking using drilling or countersinking.
The drill and its cross-section are selected in accordance with the required result according to regulatory document– GOST 19257 – 73. This is a Russian standard, but it complies with international standards. It must be new or have good sharpening. It must be firmly secured in the working tool (or in the machine chuck) so that there is no beating or wobbling.
How to correctly determine the diameter and cut a thread with a tap - table
There are special standards for determining the cross-section. Let's present all the data in the form of tabular values. Let’s say right away that they are not suitable for all tasks, but only for standard ones. These include all nuts on sale that fit the screws. Therefore, if you require a connection with a specific fastener, pay attention to its markings.
| Marking | Turn pitch | Drill diameter | ||||
| 2 | 0,4 | 1,6 | 0,25 | 1,75 | — | — |
| 3 | 0,5 | 2,5 | 0,35 | 2,65 | — | — |
| 4 | 0,7 | 3,3 | 0,5 | 3,5 | — | — |
| 5 | 0,8 | 4,2 | 0,5 | 4,5 | — | — |
| 6 | 1 | 5 | 0,75 | 5,2 | 0,5 | 5,5 |
| 7 | 1 | 6 | 0,75 | 6,2 | 0,5 | 6,5 |
This standard sizes, but there are special purposes, unique compounds. For them, everything is very simple to calculate independently. If the thread is marked M10 and the pitch is 0.3, then 0.3 mm must be subtracted from 10 mm. The result will be equal to the hole diameter - 9.7 mm.
If it is made smaller, it will be difficult for the tap to pass, and areas with poor processing will form. And if it is more, then the grooves will be shallow, the screw will wobble inside or even fall out over time.
Let's also imagine international system markings in inches:
| Designation, inches | External | Interior | Thread, mm | Step |
| G 1/8 | 9,37 | 8,858,8 | 28 | 28 |
| G 1/4 | 13,16 | 11,89 | 11,8 | 19 |
| G 3/8 | 16,66 | 15,39 | 15,25 | 19 |
| G 1/2 | 20,95 | 19,17 | 19,00 | 14 |
| G 5/8 | 22,91 | 21,13 | 21,00 | 14 |
| G 3/4 | 26,44 | 24,66 | 24,50 | 14 |
| G 7/8 | 30,20 | 28,42 | 28,25 | 14 |
| G 1 | 33,25 | 30,93 | 30,75 | 11 |
| G 1, 1/8 | 37,90 | 35,58 | 35,30 | 11 |
| G 1, 1/4 | 41,91 | 25,59 | 39,25 | 11 |
| G 1, 3/8 | 44,32 | 45,00 | 41,70 | 11 |
| G 1, 1/2 | 47,80 | 45,48 | 45,25 | 11 |
| G 1, 3/4 | 53,74 | 51,43 | 51,10 | 11 |
| G 2 | 29,61 | 57,29 | 57,00 | 11 |
| G 2, 1/4 | 25,17 | 62,96 | 63,10 | 11 |
| G 2, 1/2 | 75,18 | 72,86 | 72,60 | 11 |
| G 2, 3/4 | 81,53 | 79,21 | 78,90 | 11 |
| G 3 | 87,88 | 58,56 | 85,30 | 11 |
| G 3, 1/4 | 93,98 | 91,66 | 91,50 | 11 |
| G 3, 1/2 | 100,33 | 98,01 | 97,70 | 11 |
| G 3, 3/4 | 106,68 | 104,3 | 104,00 | 11 |
| G 4 | 113,03 | 110,71 | 110,40 | 11 |
Manual cutting steps
- Preparing the metal (cleaning it, drilling a hole).
- Selecting a tool. It is very important which tap you use to cut the thread, the purity of the result depends on it.
- Selection of other devices in one place (electric drill, drill, chamfer cutter, wrench, vice, machine oil or grease for lubrication).
- Rotation.
- Final sanding – as needed.
Features of the technology
Myself technological process consists of at least two approaches – draft and final. Follow the algorithm:
- using a hammer and a core, make a hole or recess into the workpiece;
- drill a hole;
- use lubricant;
- make rotational movements using the cranks.
We suggest you watch the video:
Precautionary measures
There are self-taught craftsmen who insert a tap into a drill. This is absolutely impossible to do, especially if the tool is not intended for machine rotation. This will only damage the electric drill.
It happens that due to excessive hardness of the metal or due to improper use of the drill, it may get stuck in the opening. This can only be corrected manually by clamping the fragment in a vice and turning it inside out.
- Determine the level angle and check the square after each turn for the first 3-4 rotations.
- Make turns in the opposite direction. to get rid of metal shavings. It may stick.
- Use for lubrication linseed oil or drying oil, kerosene, turpentine, tallow or ordinary soap. But if you are working with cast iron or bronze, it is better to carry out the procedure dry.
In the article we talked about manually cutting internal threads with a tap and presented a table. To complete the topic, watch a video on how to make hardware using a die:
Often during execution home renovation there is a need to make a thread - 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. Metric thread in cross section is equilateral triangle, and inch is isosceles.
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.
- If the thread is intended to connect to an already finished part- her 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 threaded connections performed 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 effort is observed, it can be processed outer part blanks sandpaper fine grain.
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 necessary mechanical restoration 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 in home set If you have a drill, 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.
