How to determine which tap is needed. Types and sizes of taps for threading. Allowance and cutting pattern when working with a tap

Any technical product consists of individual parts fastened together with fasteners. Although threaded connections were known in ancient Rome, China, as well as the Maya civilization, the tap began to be used as a thread-forming tool only at the end of the Middle Ages (XV-XVI century). Prior to this, the inner spiral of the nut was made in other ways, including using a lathe.

Device Features

Initially, a three- or four-sided rod was used, on which cloves were sawn out. The end was sharpened into a gentle cone. When screwing such an artifact into the hole of the nut or housing, the toothed jumpers cut the internal thread. It is clear that such a tool was far from perfect, since the cutting teeth did not have a back angle, and the front angle was negative. However, gradually its design was improved until it became more rational. Today, any tap for threading has similar structural elements:

• Grooves for chip exit and coolant supply. Their number is usually from 2 to 6.

• The profile of the depressions can be different: single-radius, rectilinear front and rear surfaces, rectilinear front and radius back.

• Groove direction: straight, spiral right and left. The former are used in conventional universal taps. Grooves with a left-handed helix are used for threading a passage. In this case, the chips go in front of the tap so as not to spoil the cut. The right recesses are used for blind holes so that the chips are brought back, otherwise, when pressed, they will break the tool.

• The chamfer is made conical in order to facilitate the penetration of the cutting teeth into the material of the part.. The angle of inclination is performed from 3 to 20 degrees, depending on the purpose of the tap (roughing, intermediate, finishing).

• The calibrating part is cylindrical, has a reverse underestimation of up to 0.1 mm, which serves to reduce the friction force. For the same purpose, the calibrating teeth are backed up at a distance of 1/3 of the width of the feather from the top of the tooth. The underestimation is about one tenth of a millimeter for threads with a diameter of 12 to 30 mm.

Types of taps

By appointment

• Locksmith (manual) taps used to make threads with a wrench. In order to reduce effort, they are made in a set, which includes 2–3 tools, each of which removes only a part of the machining allowance. The first tap is a rough tap, the last tap is a finish tap. To distinguish them from each other, the shank is marked in the form of dashes (one, two, three dashes). Locksmith taps are mainly used for cutting threads in body parts.

• Machine (machine-manual). They are used for mechanized threading on machines: drilling, turning, aggregate, such as a machining center. Structurally, they do not differ from metalwork, except that they have a shortened intake part and higher durability. The main purpose is cutting threads in parts.

• spanner. As the name implies, they are used for cutting nuts. They always consist of one tap with an elongated intake cone. During operation, the tap is not unscrewed from the nut, and the finished nuts are strung on an elongated shank, which has 2 versions: straight and radius (curved). The first is used on drilling and turning machines. After filling the accumulative part of the shank, the tool is removed from the keyless chuck and the finished nuts are shaken off. A curved tap is used on thread-cutting machines. In this case, the nuts move under the pressure of each other to the end of the tool, where they fall into the container.

Design options

• Taps with short flutes (fluteless). Used for threading aluminum alloys, tough low carbon or high strength alloy steels.

• FROM helical grooves. Used on machining centers, when cutting blind threads.

• With staggered teeth. The latter on the calibrating part are cut through one, thereby reducing the friction force, which is important for viscous materials.

• Stepped. The cutting part of the tool is divided into two sections, each of which works according to its own shaping scheme. For example, the 1st section cuts according to the generator circuit, the 2nd - according to the profile. Or, the 1st one works as a cutting tool, the 2nd one - as a smoothing one.

• Combined. 1st step is a drill, 2nd tap. As they say - two in one.

• Draw tap. With its help, threads of any diameter and pitch are cut in parts with a through hole on lathe. The part is put on the tool shank, after which it is clamped into the machine chuck, and the shank is fixed in the tool holder. Set the automatic feed equal to the cutting step and turn on the corresponding spindle rotation. After the broach exits the workpiece, the thread is ready.

• With internal coolant supply. Used on specialized or multi-operation machines to increase productivity.

• Bell type. Used when cutting through threads of large diameter (50–400 mm). The tool is made composite, consisting of separate cutting sectors. Coolant is supplied inside, the number of feathers reaches 16, and spacious flutes can accommodate a large amount of chips.

By type of thread being cut

• Metric, denoted by the letter M. Dimensions, including the thread pitch, are measured in millimeters. Below is a table of parameters for taps with a basic (large) pitch. For each standard size, GOST 8724–2002 establishes several additional (small) steps. Three millimeters is the maximum, which can be cut with a crank.

Designation Dimensions, mm Basic pitch Drilling for tapping

• Inch conical. Diameter is expressed in English length units - inches (25.4 mm), and instead of a step, the reciprocal is written - the number of turns per 1 ”, or in the technical lexicon - the number of threads. The more threads, the smaller the thread pitch. The middle surface of the thread has a slope of 1° 47' 24", so the tap reaches the stop at the end of the cut, which must be taken into account so as not to break it.

• Pipe cylindrical. A variety of inch threads, limited to an assortment of standard metal pipes. The pitch is also expressed in threads per 1 inch.

• Pipe conical. The same as cylindrical, but with a slope. The diameter of drilling for threading is several tens less. The thread is cut to the stop.

The summary table contains the parameters of taps with an inch thread pitch

conical

Designation Thread pitch (threads per inch) Hole diameter, mm

K 1/16” 27 6.0

K 1/4” 18 10.7

K 3/8” 18 14.3

K 1/2” 14 17.5

K 3/4” 14 23.0

K 1” 11.5 28.7

Pipe cylindrical

G 1/4” 19 11.5

G 3/8” 19 15.0

G 1/2” 14 18.7

G 5/8” 14 20.6

G 3/4” 13 24.2

G 7/8” 12 27.9

Pipe conical

Rc 1/8” 28 8.2

Rc 1/4” 19 11.0

Rc 3/8” 16 14.5

Rc 1/2” 14 18.1

Rc 3/4” 12 23.6

tool material

Hand taps heat up slightly during operation, so they are made of high-carbon tool steels U10A, U12A. For machine taps operating at high speeds, high-speed steels R6M5, R6M5K5, R6M5K8 are used. The best quick cutter is P18. Finally, high-performance machines are equipped with carbide tools. Small taps are made entirely of carbide, medium taps are soldered, and large taps are usually prefabricated.

When working with metal, it often becomes necessary not only to solder it, but also to drill it. In this case, the right tools play a huge role, and how they fit together. And here the moment arises, how to choose a drill for a tap so that the work is of high quality.

But first, let's take a look at each tool separately.

Drills: their purpose and varieties

A drill is a universal tool, as it is used everywhere. Depending on what material to deal with, you can use a conical, spiral, centering or feather look.

The most common option is twist drills. With their help, deep holes are created, and during the working process itself, the design of the part allows you to extract waste chips, which helps not to clog the work surface.

If it is necessary to machine center holes, then choose the centering type. They can be double-sided with a "tail" or with a safety cone.

When drilling pipes, steel sheets or plastic, it is best to use conical models. In addition to drilling, such a device performs deburring and develops various holes. Due to this tip, there is no slippage of the product.

But for work related to wood, the selection of the drill is carried out in the direction of cylindrical options. It will help to drill holes for hinges when assembling furniture, in addition, it is possible to make blind holes with a large cross section.

Separately, it is worth noting the products that are designed for threading, that is, you can safely tighten the screws into the holes after them. Although a tap is also a similar tool with such a purpose. But that doesn't mean they're incomparable. Just under the tap, drills of the appropriate diameters are selected.

Back to index

Using a tap: features

A set of metal-cutting tools: a - drills, b - countersinks, c - reamers, d - taps, d - dies.

A tap is a cutting tool that creates holes with an internal thread. Some kind of it performs the function of threading.

The design of the tap is represented by two parts: cutting and tail. The first part has a calibrating and intake fragment. The "tail" is designed to be fixed in the cartridge. With the help of the working part (a screw with grooves), the hole is drilled, while the intake part performs the notching of the thread, and due to the calibrating part, the hole is cleaned.

The material is cut by means of cutting feathers, which are located on the threaded part of the tap.

Grooves on the base help remove waste material. The non-circular shape of the back helps the parts avoid friction.

The tap can be used to make trapezoidal, metric, pipe and cylindrical threads. Such a process is feasible both by hand and with the help of machines. Depending on the purpose, the thread is made in one, two or four times. This moment is affected by:

• hole type;
• thread pitch;
• required roughness;
• mechanical properties of the processed metal.

If you need to work with large threads, then pick up several taps. Focusing on the type of work, the tool can be:

1. Machine-manual or just machine. Accordingly, it is used for manual or machine carving. In this case, the selection is carried out among the following types: straight, helical or with shortened grooves through which chips are removed.
2. Wrench. Designed for work under nuts. To select a tap, pay attention to straight models or with a curved “tail”, to elongated ones.
3. With cut thread. This is used in the processing of sheet metal parts or when working with ductile metal.
4. Locksmith. The main purpose is manual cutting. They are part of a set that includes a fine, rough and medium tap. Roughing is used if the cutting accuracy is not important, the middle one corrects it, and the finishing one completes all the work. The choice of such a tap is rational in the case when a thread with a diameter of 0.8 to 1.8 cm is required.
5. Conical. The intake part is not equipped with a full thread, but the calibrating part is full. With this type of thread is applied to the through holes.
6. Flat. The intake cone is large. Used to create pre-threads in dies.
7. Royal. They have a spiral on the right side in the grooves. With their help, the thread is cleaned.
8. Beskanavochnye. The receiving cone has a shorter base, and there are no longitudinal grooves. Using this view, productivity increases, and the tool itself breaks less often.
9. Combined. Through the "neck" two parts are connected - roughing and finishing. With the use of such a tap, the time for performing carving work is significantly reduced. One such example is a tap drill. They can perform both drilling and cutting.
10. Special. These are narrow tools. This includes mounted, ship and tandem taps.

Even though cutting internal thread does not apply to complex technological operations, there are some features of the preparation for this procedure. So, you should accurately determine the dimensions of the preparatory hole for threading, as well as choose the right tool, for which special tables of drill diameters for threading are used. For each type of thread, you must use the appropriate tool and calculate the diameter of the preparation hole.

Varieties and parameters of thread

The parameters by which the thread is divided into different types, are:

• diameter units (metric, inch, etc.);
• number of thread entries (one-, two- or three-way);
• the shape in which the profile elements are made (triangular, rectangular, round, trapezoidal);
• the direction of the rise of the turns (right or left);
• location on the product (external or internal);
• surface shape (cylindrical or conical);
• purpose (fixing, fixing and sealing, running).

Depending on the above parameters, the following types of thread are distinguished:

• cylindrical, which is indicated by the letters MJ;
• metric and conical, denoted respectively by M and MK;
• pipe, for which the letters G and R are used;
• with a round profile, named after Edison and marked with the letter E;
• trapezoidal, designated Tr;
• round, used for the installation of sanitary fittings, - Kr;
• persistent and persistent reinforced, marked as S and S45, respectively;
• inch thread, which can also be cylindrical and conical - BSW, UTS, NPT;
• used to connect pipes installed in oil wells.

Application of the tap

Before you start threading, you need to determine the diameter of the preparatory hole and drill it. To facilitate this task, the corresponding GOST was developed, which contains tables that allow you to accurately determine the diameter of the threaded hole. This information makes it easy to choose the size of the drill.

To cut metric threads on the inner walls of a hole made with a drill, a tap is used - a helical tool with cutting grooves, made in the form of a rod, which can have a cylindrical or conical shape. On its lateral surface there are special grooves located along its axis and dividing the working part into separate segments, which are called combs. The sharp edges of the combs are precisely the working surfaces of the tap.

In order for the turns of the internal thread to turn out to be clean and neat, and its geometric parameters to correspond to the required values, it must be cut gradually, by gradually removing thin layers of metal from the surface being machined. That is why, for this purpose, either taps are used, the working part of which is divided along the length into sections with different geometric parameters, or sets of such tools. Single taps, the working part of which has the same geometric parameters along its entire length, are needed in cases where it is necessary to restore the parameters of an existing thread.

The minimum set, with which you can perform the processing of threaded holes with sufficient quality, is a set consisting of two taps - roughing and finishing. The first cuts off a thin layer of metal from the walls of the hole for cutting metric threads and forms a shallow groove on them, the second not only deepens the formed groove, but also cleans it.

Combination two-pass taps or sets consisting of two tools are used for threading in holes with small diameters (up to 3 mm). Larger metric holes require a combination 3-pass tool or a set of 3 taps.

To manipulate the tap, a special device is used - a crank. The main parameter of such devices, which can have different designs, is the size of the mounting hole, which must exactly match the size of the tool shank.

When using a set of three taps that differ both in their design and geometric parameters, the sequence of their application should be strictly observed. You can distinguish them from each other both by special risks applied to the shanks, and by design features.

1. The tap, with which the hole for cutting metric threads is processed in the first place, is distinguished by the smallest diameter among all tools in the set and cutting teeth, the upper part of which is heavily cut off.
2. The second tap has a shorter chamfer and longer combs. Its working diameter occupies an intermediate value between the diameters of other tools from the set.
3. The third tap, with which the hole for cutting metric threads is finished last, is characterized by full ridges of cutting teeth and a diameter that must exactly match the size of the thread being formed.

Taps are used primarily for threading metric threads. Much less frequently than metric taps are used for processing the inner walls of pipes. They are called pipe pipes in accordance with their purpose, and they can be distinguished by the letter G present in their marking.

Thread cutting technology

As mentioned above, before starting work, it is necessary to drill a hole, the diameter of which must exactly fit the thread of a certain size. It should be borne in mind: if the diameters of the holes intended for cutting metric threads are chosen incorrectly, this can lead not only to its poor quality, but also to breakage of the tap.

Given the fact that the tap, forming threaded grooves, not only cuts off the metal, but also pushes it through, the diameter of the drill for threading should be somewhat smaller than its nominal diameter. For example, a drill for threading M3 should have a diameter of 2.5 mm, for M4 - 3.3 mm, for M5 you should choose a drill with a diameter of 4.2 mm, for M6 thread - 5 mm, M8 - 6.7 mm, M10 - 8.5 mm, and for M12 - 10.2.

Table 1. Main hole diameters for metric threads

All diameters of drills for GOST thread are given in special tables. Such tables indicate the diameters of drills for making threads with both standard and reduced pitch, while it should be borne in mind that holes of different diameters are drilled for these purposes. In addition, if threads are cut in brittle metals (such as cast iron), the diameter of the drill bit obtained from the table must be reduced by one tenth of a millimeter.

You can familiarize yourself with the provisions of GOST governing the cutting of metric threads by downloading the document in pdf format from the link below.

The diameters of drills for metric threads can be calculated independently. From the diameter of the thread to be cut, subtract the value of its pitch. The thread pitch itself, the size of which is used when performing such calculations, can be found in special correspondence tables. In order to determine what diameter the hole must be made with a drill if a three-start tap is used for threading, the following formula must be used:

D o \u003d D m x 0.8, where:

Before- this is the diameter of the hole to be made with a drill,

D m- the diameter of the tap with which the drilled element will be processed.

A tap is a metal-cutting tool for cutting internal threads. Used for structures with threaded connection. There are a lot of types of them, consider the main and most commonly used both in everyday life and in production, their dimensions, quality and approximate prices.

1. Metric taps

Metric

They are measured in millimeters metric system measurements, not like pipe ones - in inches. In the marking they have the letter "M", which means metric. For example, if there is an M8 or M18 marking, this means that you can cut the thread into 8mm and 18mm.

Sizes of metric taps: from 2mm to 60mm, the size range is very wide, you can get almost any thread.

thread pitch. Distance between threads. It can be different, both small and large.
Each tap size has its own basic pitch. The larger the size, the larger the main step. In addition to the main one, there are several types of additional steps, but they cannot be larger than the main one, only smaller. I will give an example: the M10 tap has a main pitch of 1.5, it also happens (M10 * 1) (M10 * 0.75) (M10 * 0.5), note that all additional steps are less than the main one (i.e. the turns are very frequent )
Threads are cut using a wrench (machine-manual tap or manual), for which a square is provided on the shank for clamping into the wrench.

Clamped in tap holder

A purely machine tool does not provide for a grip under the collar, it will not work to cut it manually, only on the machine.

Taps are sold mainly in sets of 2 pieces (first and second numbers). First they pass first, it has a sharper entry, then the second (finish), its entry is more blunt.

If you just need to fix the thread, then you can buy not a complete one, but a single one (piece). It will cost twice as much for sure.

2. Nut tap.

Always longer than normal manual

He is always alone. It is used, as a rule, for a through carving. It is quite easy to recognize it, it is noticeably longer than the machine-manual one. His approach is sharp, like the first number of the complete one.

3. Left tap.

Its purpose is to cut left-hand threads. They have the Latin letters "LH" in the marking. It is used quite rarely. For example, a screw on a drill chuck. If it was with a right-hand thread, then it could well get out on its own over time, since the cartridge rotates to the right, which is why they make a left-hand thread.
Also, such taps are used to unscrew a fragment of a bolt in the workpiece, a hole is drilled in the bolt and the left tap is driven in, when it reaches the stop, the bolt is unscrewed. It turns out that it is used as an extractor.

4. Pipe taps.

With "G"

They are measured not in millimeters, but in inches, a different measuring system is used.
In the marking, these have the letter "G". Used for pipe threads.
For example, G 1/2, G 3/4, G1, this means that they are intended for threads of half an inch, three quarters of an inch and one inch.
Sizes are available from 1/8 to 2 inches, there are such as 5/8 7/8 5/6 3/8 - these sizes are quite rare, the most popular are 1/2 3/4 and 1 inch, these are most often used for systems water supply of residential pulps.
They are sold, as a rule, in sets of 2 pieces: with a sharp and blunt entry.

5. Pipe conical taps.

Needed for taper cutting.

Pipe conical

These have the letter "K" in the marking - conical.

As for the quality. Steel is mainly high-speed: P6M5 (the most commonly used), HSS. Preferably of course P18,

excellent quality

but they are rarely found in our time, such taps since the days of the USSR, sometimes with a quality mark,

Quality mark

if you find one, feel free to take it - a great thing.
They are also made of U7 carbon steel (for example, Rekos). In terms of quality, they noticeably lose to the fast cutter. They can be used for soft metal, such as aluminum, or non-ferrous metal, or just to fix the thread, but I don’t advise taking this for responsible work, they are quite fragile and can simply break off when working, especially in hard steel. It will not be easy to get such a chip, you will have to drill it, plus buy a left tap or extractor.
Their only plus is the price, they are noticeably cheaper than a quick cutter, about 2.5 times.
Approximate price for 2012: M8 - 80 rubles, M10 - 85 rubles, M18 - 125 rubles, M27 - 200 rubles.

Price for high-speed R6M5 Lviv plant, Ukraine: M8 - 200 rubles, M10 - 250 rubles, M18 - 540 rubles, M27 - 750 rubles.
As you can see, the difference is very noticeable.

Taps are the main tool for cutting internal threads in blind and through holes by hand or machine. From the point of view of accessibility, a tap for threading refers to relatively simple tools, the use of which is available to both amateurs and professionals, which makes it possible to obtain a standard thread that meets the requirements of GOST in an ordinary workshop.

Tap device

This type of threading tool is a screw with straight and helical grooves necessary for cutting threads and removing chips generated in the process. The working area includes the calibrating and cutting parts. There is a square tail section for fixing the tool in manual wrenches or chucks. The cutting process itself is a rotation of the tool in a preliminary drilled hole(deaf or through) by reciprocating motion.

Depending on the version, the tap device allows you to cut threads in one, two or three passes. Preparation of threads in more than one pass is carried out by sets of roughing, medium and finishing tools. For tapping holes in particularly tough materials such as titanium alloy, sets of five tools are available.

Application

Taps for threading are the main threading tool for household, semi-professional and professional use. They can be used to prepare almost all types of threads - metric, inch, trapezoidal, etc.

Main characteristics of taps:

• Manufacturing material. Best Option– alloyed steels providing high durability of the tool.
• Cutting method - for manual or machine-manual use.
• Hole diameter - determined according to the corresponding table.
• The parameters of the thread being cut - metric, inch, main or fine pitch, etc.

Basic rules for cutting internal threads

To properly cut a thread with a tap, you must adhere to the following recommendations:

Types of taps for threading

Depending on the cutting method, there are the following types of taps - manual, machine-manual and machine. Manual ones are equipped with a square tail for fixing in the collar, they are produced in 2 and 3 sets. Machine-manual taps can be installed both in the collar and in the chuck of the machine. For threading in a through hole, they are produced with six threads on the working part, for blind holes - with three. Machine taps are designed exclusively for installation in a machine chuck, they have helical and shortened flutes.

We briefly list some special types taps:

• Nut - have a long tail for stringing nuts, which allows you to cut threads in several products without turning the tool out. Designed for machine cutting.
• Taps for left-hand threads - indicated by the letters LH, have the same pitch and diameter as a tool with a metric thread.
• Inch taps - a tool for cutting threads in the inch measurement system. Available in 2 or 3 sets in three accuracy classes.
• Pipe taps - allow you to cut pipe threads with an inch measuring system in the range from 1/8 to 2 inches. They are produced in manual and machine-manual versions, in two sets with sharp and blunt entry.
• Conical taps - used to prepare the appropriate type of metric (K) and pipe (Rc) threads. They are distinguished by the presence of an elongated initial intake part with an incomplete thread, gradually turning into a full one.

Current Standards

The design of machine and hand taps is regulated by GOST 3266-81. Specifications - GOST 3449-84. Also, each type of tool has its own standard that determines its design.

Video

You can get visual information about the tool in the video below.