The smallest marker. Types and sizes of taps for threading. With helical flutes

Many technical devices, as well as most household items have threaded connections that mankind has begun to use since ancient times. The main tools with which the elements of such connections are made include a tap. Its use allows you to quickly and without much difficulty cut an accurate and high-quality thread on the inner surface of the hole.

Design features

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

In any tap for threading on the internal surfaces of workpieces, regardless of its geometric parameters and purpose, there are the following elements:

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

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 cutting fluid (coolant) to such a zone. The shape that the tap groove has in cross section is determined by its two surfaces, one of which is the front face of the cutting tooth of the tool, and the second is its back. According to the type of profile, chip grooves are of the following types:

• single-radius (with grooves of this shape, mainly gauge-type taps are produced);
• with straight front and back surfaces (tools with grooves of this shape are used for threading inside nuts);
• with a straight front and a radius back surfaces (most taps are made with chip grooves of this type).

The grooves can be arranged in different ways: straight, as well as spiral right or left. With straight-line grooves, general-purpose taps are made. With helical left-hand grooves, taps are produced that are used for threading a pass. The chips created by such a tool move ahead of it along the hole being machined, thereby eliminating the risk of damage to an already cut thread. When using taps with the right direction of twisting of the grooves, the chips are removed from the machining zone to the tool shank. For this reason, right-hand taps are ideal for tapping blind holes.

The intaking part of the tap, as mentioned above, has a conical shape, which facilitates the process of entering 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 chosen depending on what type of processing the tool will be used for - roughing, intermediate or finishing.

The cylindrical calibration part is made with a reverse underestimation of up to 0.1 mm, which is necessary in order to reduce the friction forces that occur during the threading process. To reduce the friction force between the working part of the tap and the surface being machined, the back surface of the cutting teeth, performed from their top by 1/3 of their width, also allows. Thus, an underestimation of the back surface of the cutting teeth is created, the value of which for tools with a diameter of 12–30 mm is about 0.1 mm.

Species by purpose

Modern industry produces different kinds taps that differ from each other in design and functionality. So, according to their purpose, taps can be one of the following types.

These tools are most often hand-held and are used in conjunction with a special wrench, with which the tap is given rotation. As a rule, they are produced and used in sets consisting of two or three tools, each of which removes only part of the allowance from the treated surface. The dimensions of the taps included in such a kit (in particular, their working diameters) differ. The first of the tools, on the shank of which a designation in the form of one dash is applied, is used for roughing, the second (with two dashes on the shank) for intermediate, and the third (respectively, with three dashes) for finishing the thread being cut.

These are tools with which threads can be cut both manually and on machines of various types (lathes, drilling, modular, etc.). Such taps differ from metalwork taps only in a slightly shortened intake part and higher resistance to mechanical stress.

spanner

With the help of such tools, as their name implies, they perform threading in nuts. Nuts, in which threads are already cut with such a tap, do not twist off the tool, but move to its elongated tail. Shanks of nut taps, with which threads are cut into drilling machines, have a rectilinear shape. Nuts with already threaded threads, moved to such a shank, are simply shaken off after removing the tool from the machine chuck. For cutting nuts on threading machines, taps are used, the shanks of which have a curved shape. When threading in this way, the nuts, under pressure from each other, are pushed along the curved shank of the tool, reach its end part and fall into the prepared container.

Requirements for the design and dimensions of both manual and machine taps for cutting metric threads are stipulated by GOST 3266-81, which is called: “Machine and manual taps. Design and dimensions.

You can get acquainted with the GOST requirements for manual and machine taps by downloading the document in pdf format from the link below.

Types by design

According to their design, taps are also divided into various types. So, depending on this parameter, tools are distinguished:

• with shortened flutes, which are also called fluteless (the design of such taps is specially designed to cut threads in parts made of ductile low-carbon steels, aluminum alloys, and high-strength alloy steels);
• with grooves located along a helical line (install such tools on machining centers and use them for cutting blind threads);
• with cutting teeth placed in a checkerboard pattern (due to the fact that the cutting teeth on the calibration part of such a tool are cut through one, it is possible to reduce the friction force during processing);
• stepped type with a working part divided into two sections, each of which performs its own function (for example, there are stepped taps, the first section of which works according to the generator circuit, and the second - according to the profile; for other types of stepped tools, the first section performs the cutting function, and the second - smoothing);
• combined (these are actually two tools in one: their cutting part, made in a single design, starts with a drill and ends with a tap);
• broach taps used for cutting threads in a through hole of any diameter (with their help, threads are cut on lathes, in the chuck of which the workpiece is fixed, and in the tool holder - the shank of the tool used; the movement of the tap during threading is ensured by the automatic feed of the machine support, and the rotation of the workpiece - the rotation of the spindle);
• with an internal cavity, due to which the tool is cooled during processing (the use of such taps installed on specialized or multi-operational equipment can significantly increase the productivity of threading);
• bell taps (such taps are used for cutting internal threads of large diameter (50–400 mm) and have a prefabricated structure consisting of individual cutting elements).

Structurally, all the taps listed above are so different from each other that you can even tell them apart from each other by the photo.

Thread types

Using taps of different categories, as well as different types of dies, it is possible to form threads on the inner surfaces of parts various types. Depending on the type of thread being cut, taps are divided into the following categories.

These are taps with which metric threads are cut. The cut thread element in such cases has the shape of an isosceles triangle, and all its parameters are measured in millimeters. The marking of such taps contains the letter "M". For the selection of metric taps and the diameter of the preparatory hole, a special reference table is used.

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 size, quality and approximate prices.

1. Metric taps

Metric

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 step 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

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

3. Left tap.

4. Pipe taps.

With "G"

5. Pipe conical taps.

Pipe conical

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

excellent quality

Quality mark

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