Undercutter: types and main dimensions

The main tools for processing workpieces on lathes are cutters. With their help, you can separate the necessary layer of material from any cylindrical part to give it the required size.

What is a cutting tool used for?

In total, there are 8 types of cutters: straight, boring, cutting, slotted, chamfer, shaped and cutting. Each of them is used in specific operations. For example, cutting tools are used to separate finished products from workpieces, and boring tools are used to bore holes or create internal chamfers. But the cutting tool has wider application. Almost every basic operation on a lathe is performed using this tool. With it, you can trim the ledges at a right or acute angle, create external chamfers, and pierce the end face and any other outer surface of the cylindrical part. Thus, it is one of the most important tools, as it directly affects the initial formation of the finished product.

Types of cutting tools

Firstly, depending on the direction of feed, cutting tools are left and right. Determining the appearance by this principle is quite easy, you just put your hand on the instrument and see which direction the thumb is pointing. If the direction of the thumb to the left is the left, and to the right is the right incisor.

Secondly, depending on the design features, there are:

• Cutting incisor bent. It has cutting edges inclined to one side from the axis of the holder.
• Cutter straight line. It has cutting edges parallel to the axis of the holder.
• Cutter end face (or persistent). This tool also has cutting edges that are parallel to the axis of the holder, but located at a smaller angle.

Thirdly, there is a classification of incisors according to the manufacturing method. Depending on this, they are of two types:

• One-piece - tools whose holder and head are made of the same material.
• Compound - tools whose component parts are made of different materials. For example, the holder is made of T10K5 hard alloy, and the cutting plate located on the head is made of P9 high-speed steel.

Selecting a tool for machining a part

Before choosing a cutting tool for processing, you need to decide on some features:

• First, you need to consider the material of the tool insert. The cutter must be more rigid than the workpiece itself.
• Secondly, you need to consider the geometry and design of the cutter.

These two parameters will affect the further choice of feed rates and cutting speeds, as well as its durability, i.e. the duration of continuous operation until the cutting edges become dull.

Cutter elements and their sizes

The cutting tool consists of two elements:

1. Holders (rods) - the main part of the cutter, which makes it possible to install the tool on the machine.
2. The head or the working part, which, in fact, is the processing of the part. The head consists of several surfaces: the front (along which the chips are discharged), the main back (which supports the cutting insert) and the auxiliary back (allows the tool to move on the work surface). In addition, there are two cutting edges on it - the main and the auxiliary, which are responsible for performing basic turning operations.

Depending on the dimensions of the tool holder of the machine and the workpiece being machined, tool holders and tool heads are manufactured in various sizes. The main dimensions of the tool on the example of a turning right undercutting face tool are shown in the table below.

Marking

As a rule, many turners who choose a tool for machining a part immediately pay attention to the marking and not in vain, because it is there that the steel grade used to create the cutting inserts is indicated. For example, the cutting tessile cutter T5K10 has a carbide plate, which belongs to the titanium-tungsten group of alloys containing titanium carbides and cobalt. Such a tool can only be suitable for rough turning workpieces of carbon and alloy steels at low speeds and at low heating temperatures.

In other cases, you will have to choose cutters made of high speed steel. They run longer at high speeds and are less prone to softening when heated to more than 200 ° C.

Materials used to create the insert

As already known, the cutting tool consists of two parts: holder and head. Both of these elements are important for the tool and each of them performs its function. For example, the holder that is mounted in the tool holder must be solid, resistant to wear and tear, and the cutting insert must not heat up at high temperature. That is why in most cases both parts of the cutter are made of various materials. In addition, this allows you to save on the production of the tool itself, which significantly affects the reduction in the final price.

Thus, the cutting inserts are made of high-speed steel or hard alloys with the addition of cobalt, because, as you know, this material is resistant to wear and works well at high temperatures. Popular materials for the manufacture of cutting inserts for cutters are high-speed steels (R9K5, R9K5F2) and hard alloys (T5K10, T5K6).

If it is necessary to process softer alloys of iron, for example cast iron, then it is recommended to choose a cutter whose cutting plate consists not only of cobalt, but also of tungsten. These include the VK6, VK8, VK10, VK3M and VK6V brands.

List of relevant GOSTs

Due to differences in design, size, and geometry, many cannot select the correct cutter. GOST should get rid of these difficulties. The standard contains all the necessary information about turning tools, their design, geometric parameters and other equally important features that are useful in calculating cutting conditions and selecting a cutter.

In total, there are 4 state standards that mention turning cutting tools:

1. GOST 18880-73 (reprinted as amended in 2003). The standard provides brief information on the basic designations, design, geometric parameters and dimensions of cutting bent cutters having brazed carbide inserts.
2. GOST 18871-73 (reprinted as amended in 2003). The standard contains the necessary information on the design and dimensions of turning cutting tools with brazed plates made of high speed steel.
3. GOST 28980-91 (reprinted as amended in 2004). It is a question of passage and cutting tools with replaceable carbide inserts.
4. GOST 29132-91 (reprinted as amended in 2004) There is information on pass-through and cutting tools with replaceable polyhedral plates, which are used in production together with a special tool, a copier.