How to choose a tap for a bolt. What is a marker. Construction types and how to use them. Important points for choosing and working with taps

Despite the fact that the cutting of internal threads is not a complex technological operation, 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 Various 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.

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.

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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 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 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.

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 resistance. 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.

• With 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.

2017-06-15

Which tap to choose if the master is faced with the task of drilling holes with internal threads to restore studs, nuts, broken bolts and similar work? We suggest following the recommendations - take into account the parameters described below.

Image #1:

1. Thread standard.

Today they produce dies with two standards: metric and inch. The most common are metric products, the cutting edges of which have a conical blade type.

2. Thread profile.

The profile on the last turns of the triangular blades allows you to wrap nuts on the restored thread.

3. The principle of cutting.

The use of hand-type taps is possible in plumbing. When working with tough alloys (for example, based on titanium), it is better to use machine-type tools.

4. Type of die.

Distribution received dies of split, solid and sliding types. Solid products create threads best quality because they have a high level of rigidity. Sliding ones are used in sets, as they can be used to make threads of various sizes.

Types of taps and their purpose

The purpose of the taps varies, so for each type of work you need your own tool. Let's talk about the main varieties.

Image #2:

1. Manual / machine. Choose the option that is designed for the appropriate type of work. At the same time, pay attention to the device of the product (screw, straight, with shortened grooves).
2. Wrench. Single tool for straight through threads. It is longer than the machine-manual one and has a sharp lead, similar to the first number of the complete tap.
3. With cut thread. The tool is suitable for processing sheets and cutting holes in plate metal.
4. Locksmith. Designed for manual cutting of holes. Supplied in sets consisting of three tools (roughing, finishing, medium). Work begins with a draft, the hole is corrected with a middle one and polished with a finishing element.
5. Conical. Suitable for threading through holes. The intake part of the products has an incomplete thread, and the calibrating part has a full thread.
6. Flat. Suitable for making pre-threads. They have large intake cones.
7. Royal. Used for cleaning threads. The main difference from other types is the presence of a spiral on the right side.
8. Beskanavochnye. Suitable for long-term work with high productivity. The product has a short base of the receiving cone without longitudinal grooves, which reduces the likelihood of breakage.
9. Combined. These are products made up of two parts (roughing and finishing, connected by a neck). The combination tool reduces the time to complete the work. For example, you can buy a tap drill that is suitable for drilling and tapping at the same time.
10. Special. Products are highly specialized. This type includes mounted, ship and tandem taps.

How to choose a drill for a tap?

How to choose a tap drill if you need to cut a thread of a certain size? In order not to be mistaken, remember the principle of creating holes. The fact is that when threading, the metal is removed along with the chips, leaving through the cutting edges of the tool. Therefore, the diameters of the rods are chosen not according to the nominal diameter of the thread, but slightly less. The table below will help guide you.

For cast iron and highly brittle metals, the drill diameter is reduced by 0.1 mm from the table value. For high-quality inch threads, pay attention to the required pitch and hole diameter (see table below).

Table #2:

How to choose a thread tap

• diameter measuring system (inch, metric);
• number of tool passes (one, two, three);
• profile shape (rectangular, trapezoidal, triangular);
• the side in which the screw rotates (left, right);
• thread placement on the part (inside, outside);
• the shape of the part (cone-shaped, cylindrical).

If single products are mainly used to fix a broken thread, then kits are taken to create a new one. In them, the types of taps for threading are defined as rough, medium and finishing.

Image #3:

The first is intended for cutting a rough thread, the second for deepening it, the third for bringing it to the final (finishing) form. To distinguish one product from the rest in the set, pay attention to the shape of the marks on the tail parts.

• The first tap has cut-off tooth tips and is smaller in outer diameter than the rest of the tools in the set.
• The second, with short tooth segments, has elongated ridges. The diameter of the middle tap is slightly larger than the fine tap.
• The third has a full comb of teeth and matches in diameter with the dimensions of the future thread.

When calculating the future diameter of the hole, the formula is useful:

Table #3:

Important points for choosing and working with taps

1. If you decide to buy taps in a set, use them in the desired sequence, from rough to finish. Otherwise, damage to the thread and breakage of the tool may occur.
2. Use the crank after you start working with the finishing tool. Usually, increased resistance indicates that it is necessary to use an additional device.
3. Take a square to check the perpendicularity of the stroke of the tap relative to the surface of the workpiece.
4. Choose the correct coolant. At the same time, please note that blanks made of bronze and cast iron are cut without lubrication. Steel and brass go well with linseed oil, aluminum - with kerosene, copper - with turpentine.

Hello.

This time the review will be devoted to a tool designed to simultaneously make holes and cut threads into them.

The tool is supplied in a regular plastic bag, which, logically, is covered with many small holes during the trip. So you have to be prepared for the fact that as soon as it is in your hands, your hands will be in grease.


What is the advantage of this tool - two operations are done at a time. First, the cutting part of the drill makes a hole in the metal, after which the tap cuts the thread. Using such drills, you can not think about the need to comply with the ratio of the diameter of the drill to the diameter of the tap. But just in case, here is a table of the ratio of those same sizes:


The delivery set includes 6 such taps designed for cutting threads of various diameters (10 * 1.5, 8 * 1.25, 6 * 1, 5 * 0.8, 4 * 0.7 and 3 * 0.5). On the shank of each tap there is a designation of its parameters - the diameter of the thread being cut and its pitch.


The shank is hex, so this tool will also work with non-clamping quick-release chucks. True, the question is whether such a tool has enough power to drill a hole in more or less thick metal.


The cutting part is coated with titanium nitride. Not paint - 100%, it was not subject to battery acid. Metal - Chinese high-speed steel HSS6542 (similar to our 6M5 or European M2). Steel is characterized by low cost in combination with good performance. Chemical composition W:5.50-6.75; Mo:4.50-5.50; Cr:3.80-4.40; V:1.75-2.20.

Flutes for forcing chips have a spiral shape, which is typical for a tool operating at high speeds. If you recall a standard manual tap, then the grooves there are linear.


There are no problems with diameters. Everything exactly corresponds to the declared parameters.


To test the tool in action, a cordless screwdriver, several books and a steel plate 8 mm thick were used :) Due to the frost outside the window, it was impossible to go to the garage, so the test was carried out in extremely unfavorable conditions, which led to the breakdown of one drill: (


But on the fault it is clear that the drill was subjected to heat treatment, that is, it was hardened. The metal is not raw.

And here's what the finished hole looks like:


The bolt is twisted without problems, and it keeps even on several turns.


And this is what the process looked like:

If the plate were clamped in a vise, and the drill was at least a little lubricated, then the action would not look so devastating :) But we managed to make sure that even under such conditions, using this tool, you can achieve the desired result :) And even after doing several holes, appearance drill bits (as well as coatings) haven't changed a bit.


So drills can be considered usable. I think that if the technical process is observed: the use of a core, lubricant and a vice (and ideally a machine tool) the result will be of better quality.

But while working with them, you need to remember that the thickness of the metal should not exceed the length of the cutting part of the drill (the part that makes the hole, that is, from the tip to the start of expansion for the tap). Otherwise, the thread will be uneven due to the increased load.

That's all. Thank you for your attention and your time.

The product was provided for writing a review by the store. The review is published in accordance with clause 18 of the Site Rules.

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