Tap (for thread cutting): design features, methods of use. Rules for selecting a quality tool

Purpose of taps

Taps are used only for cutting internal threads. Completely different tools are responsible for external threads.

• The tool is capable of making new threads in completely different holes or updating an existing one.
• Work can be carried out with different metals, such as brass, copper, similar metals and plastic.

Typically, a set containing three taps is used to make threads. Some cases require up to five taps.

To use it, you need a special tool - a tap holder. The tap fixed in it is inserted into the hole and turned in the desired direction.

Tap device

This type of thread-cutting tool is a screw with straight and helical grooves necessary for cutting threads and removing chips formed in the process. The working area includes calibrating and cutting parts. For fastening the tool in hand cranks or chucks there is a square tail. The cutting process itself involves turning the tool in a pre-drilled hole (blind or through) through a 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 with sets of roughing, medium and finishing tools. Sets of five tools are available for cutting holes made of particularly tough materials, such as titanium alloy.

Design and characteristics of taps

The tap is a very simple tool, its design consists of two main parts. The first part is the tail of the tap; it is this part of the object that is fixed in the tap holder or on the machine.

The second part is the main one; there is an external thread on it, which in turn consists of two parts:

1. Cutting element. This part of the thread is designed to form thread turns in the hole.
2. Calibration element. The second element is necessary for cleaning the newly cut holes and calibrating them.

On the sides of the tap there are special elements called feathers. It is thanks to them that the thread is formed.

Taps for metric threads of through holes GOST 3266-81

A through-hole tap is a metal-cutting tool designed to create internal metric threads; it looks like a screw with special grooves. The taps are made of high-speed steel M6M5. The design and size of the tools comply with the regulations of GOST 3266-81.

Scope of application of taps for through holes

Products in this category are one of the main thread-cutting tools for semi-professional and professional use, as well as for solving household problems. Tools are used for processing metals, steel, and various alloys.

Design features

A tap for through holes consists of the following elements: • working part: has an intake zone (formation of the first turns) and a calibrating part (bringing the thread to perfection), which can have different types of grooves; • neck; • shank: acts as a fastener; during manual operation, it is fixed in a funnel or tap holder, and during machine use, it is mounted on machines in a specialized chuck. The thread angle in the profile for metric taps is 60 degrees. All mechanical processes occur in the working part.

Types of grooves in through hole taps

• straight: such taps can be of various shapes; they are not intended for creating deep threads, since chip removal practically does not occur; • straight flute with spiral point: presented in shape B (according to DIN standard), chip removal occurs under the hole, directly in the direction of tool movement.

Types of taps for through holes

There are two types of tools: 1. Taps with a through shank: characterized by a larger diameter working part in relation to the shank; 2. Products with a reinforced (impenetrable shank): characterized by a shank of equal or larger diameter in relation to the working part.

The tools are designed for metric threads in accordance with the regulations of GOST 24705-81, are marked “M” and have a numerical indicator of the thread diameter. Standard models have diameters from 1 to 68 mm, thread pitch can vary from 0.25 to 6 mm.

Benefits of Through Hole Tap

The choice of these tools is due to the following advantages: • the possibility of single-pass thread cutting; • high performance; • versatility: due to the reinforced alloy, the tap can be used when working with various materials; • ability to withstand large dynamic loads; • thread accuracy; • variability in the diameter of the resulting holes; • wear resistance; • increased red fastness.

Features of operation

To obtain high-quality internal thread cutting, before using the tool, it is necessary to determine the pitch length, or the thread diameter itself. It is recommended to treat the working surface of the tap with a special lubricant or machine oil or grease. The drilling process must be carried out strictly perpendicular to the plane. In a situation where you need to break off the resulting chips, you should periodically smoothly rotate the tool in the opposite direction during work. A through hole tap is not suitable for making blind holes because they have different chip evacuation systems. The through-hole tool, due to the features of the grooves, removes chips from below or does not remove them at all. If you use this product for blind holes, there is a high risk of the tap breaking or causing incorrect threads due to accumulated chips.

An analysis of the chemical composition of the WOLFSTAR brand tool was carried out in a laboratory at one of the most prestigious narrow-profile universities in Russia: National Research Technological University "Moscow Institute of Steel and Alloys" (NUST "MISiS"), the results of which confirm that the tool from all categories complies according to the chemical composition requirements of GOST.

The result of the analysis.

In the online store WOLFSTAR.RU you can buy metal taps of any type, size and purpose, as well as tap sockets, at an affordable price and in a wide range.

Materials

Various materials are used to produce taps, including:

• Alloy steel;
• Tool steel;
• High speed steel.

The most common and optimal option is considered to be high-speed steel. It has many advantages over others:

• High service life;
• Resistance to temperature changes;
• High quality of work performed;
• Ability to work at high speed;
• High strength material.

To work with some materials, special taps with an additional coating are made. This solution increases the service life and efficiency of the tool.

A set of taps - the pros and cons of such a tool

In theory, everything seems simple when working with taps, but this is not entirely true. If we look at the process in more detail, this is a rather expensive undertaking in terms of physical strength, especially if you set to work manually. After all, cutting metal with metal is not easy, the friction forces are enormous, the chips are not as pliable as in wooden products when drilling, they are also very resistant when exiting through the grooves. Due to the presence of grooves in the body of the tap, the strength of the body is somewhat reduced, so these devices are prone to breakage, especially when using a thin size.

But not everything is so depressing, because it’s not for nothing that the tap was used before and has not disappeared from the toolkit to this day. The structure itself is simple, easy to make and use, you don’t have to think long about how to use it and where to attach it. The accuracy of the thread is quite high, and for very demanding parts it can be increased by improving the quality of the tap itself, which is easier than building complex devices to control the cutting process itself. Having made a more perfect tap, you can already count on the same perfect thread.

Types of taps

There are a large number of taps that are used to form a wide variety of threaded holes. All of them are divided according to different parameters. The first division of the equipment is its thread type:

• Metric;
• Inch;
• Pipe.

Taps by thread type differ in the profile angle and the number of turns of the future thread. The differences also lie in the slope of the profile, which is necessary for greater reliability of the threaded connection.

In addition, taps can differ in the type of groove:

• Straight groove;
• Helical groove.

Products with screw groove type are divided into left spiral and right spiral. They are designed to create different holes. The first type is used to create threads in blind holes, the second in through holes.

Taps are divided into single-approach and multi-approach. Depending on the type, they are designed to perform work in one or several approaches. For multi-approach products, it is normal to have a set of several taps, each of which must be used to correctly form the thread.

The main parameter for dividing tags into types is purpose. Tools that differ in their purpose:

• Locksmith. The simplest variation of a tap that can be used without special equipment.
• Machine. The difference from a bench tap lies in the shape of the product and the method of its use. Operation is only possible with a special machine.
• Machine-manual. A universal tool that can be used manually and on a special machine.
• Conical. Due to their special shape, such taps are used to form conical threads. Typically used on special machines.
• Cylindrical. An ordinary tap used to form threads in blind holes.
• Nut. It differs from all other models in its elongated tail and the ability to thread several nuts at once.
• Spot. A one-step type of tool that is used to create threads in dies.
• Uterine. The tap is used as an addition to the die tap. It is designed for stripping formed turns.
• Trapezoidal. One-step tool, resistant to high loads. It is used to create trapezoidal shaped threaded holes.
• Grooveless. Taps characterized by a minimum number of grooves in their structure.
• Screw. Such products are designed for quick processing of dead-end holes.
• Combined. Tools that can perform multiple functions at once. For example, a tap-drill.
• Stepped. Ordinary equipment consisting of two parts. Cutting and calibrating.
• Bells. Used to form large diameter threads.
• Chess. Taps that are designed to reduce friction.
• Broach tap. Such equipment is used when it is necessary to form threads in through holes. Slaves are carried out with the machine.
• Rolling tap. Due to the nature of working with the tool, there is no chips or dust.
• Hollow. Taps that are necessary for creating threads in difficult working conditions.
• Candlesticks. Designed for forming threads in spark plug wells of internal combustion engines.
• Fishing Common in the oil and gas industry.

Design features

The first tools for cutting internal threads were distinguished by a primitive design and consisted of a tetrahedral rod, at the working end of which, sharpened to a shallow cone, cutting teeth were sawn out. When using such a tap, the thread was cut by screwing it into the inside of the nut or into a previously prepared hole in the workpiece. Naturally, such a tool had many disadvantages, the most significant of which include the absence of a rear surface on the cutting part, as well as a negative rake angle. Over time, the design of taps has become more sophisticated, and today they allow you to create accurate and high-quality internal threads.

Any tap for cutting threads on the internal surfaces of workpieces, regardless of its geometric parameters and purpose, contains the following elements:

• side grooves (there can be from 2 to 6);
• conical intake part;
• calibrating part, which has a cylindrical shape.

Tap design

The grooves located on the side surface of the tool along its entire length simultaneously perform two functions: ensuring the removal of chips from the processing zone and facilitating the supply of coolant lubricant (coolant) to such a zone. The shape that the groove of the tap has in cross section is determined by its two surfaces, one of which is the front edge of the cutting tooth of the tool, and the second is its back. Depending on the type of profile, chip flutes are of the following types:

• single-radius (with grooves of this shape, mainly calibration type taps are produced);
• with straight front and back surfaces (tools with grooves of this shape are used for cutting threads inside nuts);
• with a straight front and radius back surfaces (most taps are manufactured with this type of flute).

Tap flute profiles

The grooves can be located in different ways: there are straight grooves, as well as spiral right or left. Universal taps for general use are manufactured with straight-type grooves. Spiral left-handed flutes produce taps used for cutting threads for passages. The chips created by such a tool move ahead of it along the hole being processed, thereby eliminating the risk of damage to the already cut thread. When using taps with the right direction of twisting of the grooves, the chips are removed from the processing zone to the tool shank. For this reason, right-handed taps are ideal for cutting threads in blind holes.

The intake part of the tap, as mentioned above, has a conical shape, which facilitates the process of inserting the tool into the hole being machined. The specific value of the angle of inclination of the intake part, which can be in the range of 3–20°, is selected depending on what type of processing the tool will be used for - roughing, intermediate or finishing.

Tap designs according to GOST

The cylindrical calibration part is made with a reverse reduction of up to 0.1 mm, which is necessary in order to reduce the friction forces arising during the thread cutting process. The friction force between the working part of the tap and the machined surface can also be reduced by backing the back surface of the cutting teeth, carried out from their top to 1/3 of their width. This creates a reduction in the back surface of the cutting teeth, the value of which for tools with a diameter of 12–30 mm is about 0.1 mm.

Geometry of the cutting and calibrating part of the tap

Cost of taps

Prices for taps vary from several hundred to several thousand rubles. All this depends on the materials from which the instrument is made and on its type.

Thus, simple taps, such as metalworking, stepped or screw products, are relatively inexpensive, while the cost of fishing taps starts from four thousand rubles.

To form a high-quality and reliable threaded hole, it is important to choose the right tool. The choice depends on what materials will be used and the characteristics of the required thread.

Basic rules for cutting internal threads

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

• Drill a hole of the required diameter. In fact, this is the main stage, because if you make a mistake, you will either get a loose thread or break the tap due to overload. For the most common, metric threads, the diameter table is given below. For a rough estimate, you need to subtract the thread pitch from the thread diameter. Drilling must be strictly perpendicular to the plane.
• To cut manually, we perform reciprocating movements - two turns forward, one back.
• After passing with a rough tap, we repeat the procedure with a finishing one.
• When cutting in a deep hole, it is necessary to periodically completely unscrew the tool and clean the grooves.
• To tap into a blind hole, its length must be greater than the planned thread length.
• When cutting threads in deep holes, be sure to use a lubricant - emulsion, kerosene or linseed oil.

Photos of taps (for thread cutting)

Types and areas of application of taps

According to the drive method, they are divided into:

• Manual - they are distinguished by a square tail, 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 indicator with one movement.
• Complete. The name speaks for itself. You will need a set of 3 taps, since the internal thread must be made with high precision. First, the coarsest tool is used, then the thinnest, 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 area that 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 section 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.

How to correctly determine the diameter and cut a thread with a tap manually - 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.

The table can be continued, it is large, but we will not do this within the scope of this article. For more detailed values, we recommend that you refer to the document - GOST 19257 - 73.

These are standard sizes, but there are special purposes, unique connections. 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 the international marking system in inches: