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How to sharpen a cutter on a lathe. Sharpening of turning tools for metal and finishing. Features of sharpening

The efficiency and safety of turning work directly depend on the type and quality of sharpening of the tool used; in order to avoid mistakes, it is important to be able to select and prepare it correctly. On an industrial scale, these actions are carried out using special machines; in other cases, the cutters have to be sharpened with your own hands. Despite the simple sequence, sharpening work requires experience and consideration of many nuances: from the material of the tool to its type and purpose.

This tool has a simple design and consists of two elements: a rod that holds it in the machine, and a working head with a cutting part that directly processes metals and hard materials and requires periodic sharpening. The fixing part usually has a geometric (square or rectangular) cross-section, which reduces the risk of turning, moving or knocking the cutter out of the lathe, and an elongated shape. The cutting part (working part) is more complex; it is formed from several adjacent edges and planes with different sharpening angles.

The cutter head has 2 surfaces: the front, removing chips, and the rear sides, facing the part and divided into main and auxiliary. The same applies to the cutting edges, the main one of which is formed at the intersection of the front surface and the rear main one. The angles of their sharpening determine the purpose of the cutter and are considered an important characteristic: depending on the location, they are divided into points, the rear main ones and the same front ones, their sum with deviations from the corresponding cutting axis is always equal to 90°. The design of the cutting head is also determined by the angles between the processing plane and the front surface, edge projections, feed direction and display of the main cutting line.

Types of tools for turning equipment

The classification of cutters is conditional, the range includes products with different feed directions (left and right), design (straight, bent with a deviation of the head axis to the left or right, curved, drawn and having a unique shape), cross-section (round, square or rectangular), method manufacturing (solid and composite, with a cutting part in the form of a plate) and installation (radial and tangential). Accordingly, turning cutters are used for different jobs: from roughing to grinding, depending on the intended purpose and method of processing the workpiece, the following varieties are distinguished:

Pass-throughs designed to remove the bulk of the allowance from the surface of the workpiece along its axis of rotation. As a rule, their cutting part is plate-shaped and made of high-speed metal, and the rod is made of 45 or 50 steel.
Scoring, used for roughing parts, turning external surfaces and facing. A special feature of these cutters is the presence of a curved profile of the front part, which promotes curling of chips, and a chamfer, which strengthens the cutting edge. This variety is made from both alloy steels and especially hard metal alloys.
Boring, for processing finished blind or through holes obtained by drilling, casting or stamping. These operations are considered more complex in comparison with external turning; when choosing and sharpening this type, it is taken into account that the cross-sectional size of a turning cutter should always be less than the diameter of the passage.
Grooved or slotted, related to multifunctional, and used when forming grooves on parts with complex configurations (including cylindrical and conical), performing axial grooving, cutting ends and other turning operations. The dimensions and shape of the cutting edge of this variety are selected based on the width of the groove being formed; depending on the required radius of the groove, their sharpening can be straight or curved.
Shaped, non-standard, and installed when high-precision processing of complex parts is necessary; in most cases, they are made to specific sizes and shapes.
Threading machines used to create internal and external threads with different pitches and profiles using lathes. They influence the workpiece at all points of the edge and perform a screw movement relative to it.
Chamfers, designed for chamfering, most often at an angle of 30 and 45°.

Depending on the material of the base and the cutting part, all turning tools are divided into:

Made from different grades of tool steel: carbon (optimal for processing at low speeds), alloy (having average heat resistance and strength) and high-speed (characterized by increased productivity).
Carbide, used at high cutting speeds, and installed on metal lathes, working with particularly hard and durable workpieces or performing high-precision operations.
Metal-ceramic, which are composites based on tungsten, titanium, tantalum or mixtures thereof, cemented with cobalt.
Mineral-ceramic (technical alumina), characterized by increased heat resistance, but due to fragility, are not used when impact work is necessary and mass production of products on turning equipment.
Cermet, which are alloys of minerals, metals and carbides and have higher resistance to mechanical stress compared to the previous variety.
Diamond turning cutters used in automatic lines with large-scale and mass production of homogeneous products with the first and second class of accuracy, and high surface cleanliness. These products have minimal impact on the structure of the workpiece material, regardless of its degree of hardness, and do not require sharpening.
CBN, which are cutters with plates made of super-hard synthetic material.

Rules for sharpening turning tools, nuances and diagrams

All cutters require this procedure, with the exception of those with replaceable carbide inserts; in the absence of special machines, the turner carries it out on his own. Among the practiced and time-tested methods are:

Abrasive sharpening of a cutting tool, performed on a machine with a grinding wheel or using a bar. The whetstone material is selected based on the hardness of the metal or composite being processed. It is recommended to sharpen varieties made of hard alloys on green corundum, and from ordinary steels - on white.
Chemical-mechanical treatment, which consists of applying a solution of copper sulfate to the cutting edge, followed by washing it off with abrasive compounds and grinding with a moving element. Such actions allow high-quality and quick sharpening of large tools made of hardened steel and hard alloys while simultaneously increasing its crack resistance; the method is valued for its efficiency and provision of a smooth surface.
Sharpening of cutters on specialized equipment with interchangeable or different wheels, including diamond finishing wheels.

When doing work with your own hands, the abrasive method is most often chosen as it is more accessible and simpler. When implementing it, a clear sequence of actions is followed: the main rear edge should be sharpened first, the rear auxiliary edge should be sharpened next, and only then the front. The work is completed by sharpening the radius of curvature; at all stages, the cutting tool is pressed against the abrasive stone with a constant displacement along the surface, both in order to reduce wear on the wheel and to avoid overheating of the cutter. Regardless of the type of surface being processed, both tearing and excessive pressing are avoided during abrasive sharpening.

Special stencils help you check how well your cutter is sharpened. You can buy them or make them yourself from a sheet of metal, cutting out a template in the right places that matches the running lines and sharpening angles. Subsequently, such a workpiece is recommended to be hardened and used both when checking the correct preparation of the cutter and to assess its condition. All angles are subject to verification; the higher the requirements for the quality of products produced on lathes, the more accurate the template made by yourself should be.

Sharpening a tool with a coarse abrasive is not enough; the final stage is finishing small sections of the cutter surfaces adjacent to its cutting edges. For these purposes, an abrasive paste based on boron carbides or GOI polishing compounds is applied to the edge of the round disk, after which a turning cutter is pressed against it with the desired side and the rotation process is started with the direction towards the plate.

This stage is not difficult to perform independently; with such processing, small grains eliminate the slightest irregularities, which ultimately increases the service life of the tool. When finishing with compounds with low abrasiveness or sharpening carbide cutters, it is recommended to additionally coat the surface of the wheel with kerosene or a similar substance; when using modern pastes or a copper wheel, this is not necessary.

Sharpening lathe cutters requires constant attention, to achieve optimal results it is recommended:

Cool the tool with water or take breaks from working.
For sharpening, use machines with the ability to adjust the height and angle of rotation of the grinding wheel or place special pads under them. Ideally, the level of the cutting edge and the central axis of the sharpener coincide or shift no more than 3-5 mm down.
Monitor sharpening angles, abrasiveness of the grinding wheel and its rotation speed depending on the tool material and type of processing (finishing or roughing) using the corresponding tables of sharpening modes.
Control the direction of movement of the circle. When sharpening turning tools with your own hands, the main danger is flying plates; when pressing them with a sharpener, this risk is minimal, and vice versa.

Articles

Sharpening metal cutters for a lathe is a necessary procedure for efficient and uninterrupted operation of the equipment. The fact is that turning cutting machines are actively used; they are used to process products and cut threads. It is clear that frequent use causes the units to become dull, which leads to samples of poorer quality. In order to perform operations correctly and continue to be actively used throughout its service life, periodic sharpening is required. Of course, this procedure is invariant, depending not only on the type of machine and the units used, but also on the goals and objectives of use.

What parts do cutters for turning units consist of?

The cutters of any mechanism include two parts. The first is a rod, it is necessary to fix the object in a special holder. The second is the head itself, which is driven into rotation. The rake surface is where the part is chipped and processed. The back surface is usually called the reverse side of the process. It is to the back bar that the product that is currently being processed is addressed.

With the help of the main edge - the rusting surface - sharpening of tools and workpieces occurs. The element is located at the intersection of the front and back. If the main rake surface intersects with the secondary one and a cutter is installed in place, an additional edge is created. With its help, a slightly different processing of mechanism parts is carried out. The apex denotes precisely the suppression of the latter.

The angles of the mechanism are the most important characteristics that allow us to distinguish the main and auxiliary components of the lathe assembly. The main ones produce movement along the plane, the projection of the main one onto the main axis. Please note that the axes:

the main one is superimposed on the lower part of the mechanism - parallel feed stroke of the equipment;
cutting is an intersection with the main one, at a certain angle to the processing surface.

Depending on the intersection of the axes, the resulting angles are distinguished. If they are located between the front incisor and the main one, then this is the sharpening angle. Spruce between the processing surface and the rear main, then the rear main. By analogy with the last example given, the front main ones are formed, located between the feed and the cutting projection, the processing area and the front, the auxiliary and main projections.

The sum of the angles of the point, rear main and front main never exceeds 90 degrees.

How to choose a sharpening method depending on the type of cutter?

The main part consists of their cutting part for metal or wood - structural similarity. There is a mount. But controlled removal of part of a part is possible in various ways, the type of tooling depends on this.

The type of cutter is determined by the number of surfaces (there can be two or more). Surface characteristics are determined by the width of the blade and its shape; there are also variations depending on the possibility of adjustment (the direction is chosen arbitrarily). The edge is an integral design feature.

The choice of the type of cutter, that is, a specific model with technical characteristics, depends on the type of work to be done. For example, for the simplest processing of the external shape of a wooden part, one option will be needed, but for a standardized scheme for making metal carvings, a completely different one will be needed. Not only the type of cutter changes, but also the method of sharpening it.

Flat straight

Depending on whether metal or wood is used, the features of creating flat straight incisors change. The main purpose is surface treatment. But these variations are used to create small, simple holes, recesses and grooves in products. Flat straight cutters have the following characteristics:

the ability to quickly create rectangular holes;
blade width variations - from 4 to 40 millimeters;
sharpening angle variations - from 25 to 40 degrees.

Sharpening occurs according to a simplified algorithm. The technician will be required to level the end damaged from use. To do this, you will need to take a careful sharpener and work the end with it, while avoiding oversaturation of the area. The handle is placed last. 2-3 direct flat variations must be installed in the lathe - this will improve productivity indicators. Be sure to sharpen each sample.

Oblique straight

The functionality of skew lines is intuitive by analogy with plane lines. Sharpening occurs on both sides of the cutter, while the instructions look simplified. Required:

select the required width parameters (from 4 to 40 millimeters, but may vary);
choose the optimal thickness - convenient for the operation of the instrument and its efficiency;
cut off one corner, while achieving a ratio of 70 to 75 degrees;
carry out high-quality sharpening at an angle of 25 degrees.

It is important to periodically check the position of the edge. It is necessary that the cutter lies flat on both surfaces and that the edge has no flaws. If you don't follow this rule, you will end up with an unsatisfactory quality cutter.

Cut-off

Cut-offs are models designed to form an angular cutter. Sharpening is carried out only in one direction, but this does not mean that a specialist will save 50 percent of the processing time. Using a trimming cutter, various kinds of workpieces are made and rough finishing of wood or metal products is carried out. Step-by-step execution algorithm:

cutting the corner of the end at an angle of up to 45 degrees - no more;
sharpening from 30 to 40 degrees (no more, since it will be inconvenient to use the tool and no less, since it will be ineffective).

There are no options to select length characteristics. The specialist selects the option that is in demand in his work profile.

Semicircular flat

Using this type of cutter, notches are made in a semicircle. But they will also be needed to ensure processing of the roughing field. The scope of application is wide, although at the beginning of use it seems the opposite. The sharpening process occurs as follows:

turning the element using the necessary materials, such as sandpaper;
fitting the end - it must match the shape;
sharpening the edge from 20 to 45 degrees.

Please note that you will need several options for semicircular flat parts for those who are going to actively make shaped recesses and decorative variations.

Grooved

Grooved ones have a number of features that make them stand out from the crowd. First of all, these elements are in the form of a gutter, while the width varies, but does not exceed 3 centimeters. They are used not only to create a concave type shape where wood is used, but also for processing wood (rough).

Grooved cutters are quite difficult to make yourself at home. But if it is not possible to buy the required configuration in a store, then they make it themselves. You will need to leave the worn-out frame - it will act as a blank and a sample. After that:

process the end up to 10 centimeters to form a semicircle (remove the rest by trimming);
to make a deepening - you need a special tool;
sharpen the lower part, which is on the convex surface (up to 40 degrees).

An employee without work experience can make the first versions - no specific knowledge and skills are required. But the production of a gutter will require skill and even craftsmanship.

The sharpening angle is not fundamentally important. If it fluctuates by 5-7 degrees, it will have a slight effect on operating efficiency.

How does cutting force depend on the sharpening angle?

The rake angle has the greatest influence. The cutting force changes upward if the number of degrees of the indicator increases. But don’t think that by increasing the maximum angle you will be able to achieve the greatest effect. Everything turns out the other way around - increasing the angle decreases reliability.

Optimal sharpening angle values are achieved. It should not be increased or decreased. Only in this case can high efficiency rates be achieved without compromising reliability.

Sharpening angles: types and characteristics

Incorrect selection of sharpening angles determines the ineffectiveness of the procedure. If you do not realize the mistake and continue the action, the cutter will be damaged and you will have to buy a new one.

The cutter has several types of angles. Two main, two auxiliary and angles in projection or plan. The characteristics of each are determined depending on the shape indicators, processing quality, product typology, edge material and many other parameters.

Principal angles

There are two main angles - front and back. The front one determines the quality of work and how much chips will be produced. As the degrees increase, a greater deformation of the product results. If you increase the indicators of the second, the amplitude of vibrations increases, which negatively affects the holder.

Auxiliary angles

The auxiliaries are located on the auxiliary platform. The main auxiliary is between the direction and the cutting edge. The second auxiliary is the angle between a straight line segment that runs through the top of the plan and intersects at the edge area.

Plan angles

Angles in plan are represented by the main, auxiliary and the one located at the apex. The main one is the plane near the projection and the main line. Auxiliary - continuation of the projection in the direction of work. Located at the top - near the plane with the intersection of the main one. Moreover, if the indicators of the first and second cannot be less than zero, then this is possible for the third. Minus values are achieved if the vertex is at the highest point of the projection, while the maximum plus will be when it is at the bottom.

Measuring cutter angles

The measurement is carried out using a table goniometer, which consists of a base, a measurement sector, a moving template and a screw for fixation. The measurement is carried out according to the algorithm:

placement on the base;
contact between edge and plane;
the direction of the measuring part is parallel to the edge;
laying the template to the site.

The value is measured using a special ruler. A vernier is also used, which is combined with the side platform of the equipment. It shows more accurate measurements.

Device for sharpening turning tools

Musats are an effective and simple way. The device is a metal rod with a ridge. Processing is carried out using the handle.

Sharpening stones

The whetstones are also a manual method. The part is applied and carried out on each side 10 times. It requires some skill.

Mechanical sharpeners

Automated method. You will need to set the necessary parameters and actively operate the tool depending on the required parameters.

Electric sharpeners

Convenient to use. It looks like a metal bar with holes of different sizes.

Description of sharpening technique

Safety precautions

Sharpening is carried out in compliance with safety regulations. The specialist puts on protective equipment for the face and gloves. Depending on the chosen technique, security methods vary. Do not touch the device or sample until it has completely cooled down.

Conducting fine-tuning

Finishing of slotting tools is carried out according to the chosen method. Used manual methods, automated machines. It should be understood that:

the incisors are not immersed in water - they break;
during finishing, water is supplied for cooling;
First, the back edge is processed, and then the main and auxiliary faces;

Carbide versions are finished with copper deposits (impregnated with boron carbides). Other types are finished with whetstone soaked in kerosene, with minimal abrasiveness.

Mandatory grinding

Sanding is carried out with an emery wheel. Choose fine-grained variations. Ordinary bars are also used. Sharpening cutters is a complex process. goes into detail, then he can process it on his own.

Turning cutters are used on various turning units, being a working tool for them for processing shaped and other products, planes; they can be used to cut threads, as well as many other operations.

1 What parts do cutters for turning units consist of?

Turning cutters include two key elements - a rod for fixation in a special machine holder and a head. The surface intended for chip removal from the part is called the front surface. By rear (either auxiliary or main) we mean the surfaces to which the product subjected to metalworking is facing.

Metal processing of workpieces is carried out by the cutting main edge, formed by the rear (main) and front surfaces of the devices. Turning cutters also have an additional edge. It is created by the intersection of the auxiliary and main surfaces. Moreover, the place of this intersection is called the top of the tool.

Of great importance for the technical capabilities of a machine working with cutters are their angles, which are usually divided into auxiliary and main. The last of these are measured in a plane that is a projection of the main edge onto the secant (that is, main) plane.

Angles are described by the following planes:

Basic. It is superimposed on the supporting lower surface of the tool and is parallel to the feed directions of the machine.
Cutting plane. It intersects the main cutting edge and is placed tangentially in relation to the processing surface.

There are sharpening angles (between the rear main and front surfaces of the cutter), rear main ones (between the processing plane and the rear main surface), and front main angles (between the perpendicular plane and the front part of the tool). All these angles add up to 90 degrees.

In addition, the cutters for the machine describe the following angles:

between the feed direction and the projection of the cutting main edge;
between the processing plane and the anterior incisal surface;
between the projections of the secondary and main edges.

2 Classification of cutters for turning equipment

Turning cutters are divided into different types. By type of processing they can be:

boring - used to produce holes (manufactured according to GOST 10044, 9795, 18872, 18063, 18062, 28981, etc.);
pass-through – for processing parts along their axis of rotation (GOST 18869, 18878, 18868, 18877, 18870);
groove - for forming grooves on surfaces (internal and external) of a cylindrical shape (GOST 18874 and 28978);
chamfering - they are used to remove chamfers from workpieces (GOST 18875);
trimming - for trimming or reducing ledges (GOST 29132, 28980, 18871, 26611, 18880);
thread-cutting - they are designed for using a lathe (GOST 18885 and 18876);
shaped – used when performing specific and individual metalworking work.

They are also widely used, which allow you to make narrow grooves on workpieces and cut parts at right angles. They are produced in accordance with GOST 28987 (prefabricated plate) and GOST 18874 (made of high-speed steel). According to the feed, the cutting tool is classified as left or right. The left cutters carry out processing towards the tailstock of the machine, the right cutters - towards the front.

The cutting part of the turning tool we are interested in can be made of ceramic-metal, high-speed cutting, diamond or carbide material. Turning cutters made of hard alloys are used for processing non-ferrous and ferrous metals on units with high feed rates. High-speed cutting machines are more suitable for turning equipment of relatively low power.

In the absence of shock load, it is recommended to use instruments with metal-ceramic plates. They usually process steel and cast iron workpieces. And diamond devices are intended for boring and fine turning of parts made of alloys based on non-ferrous metals. The heads of metal turning cutters have two different shapes. Based on this, the instrument is divided into bent and straight.

For bent cutting devices (for example, for pass-through devices according to GOST 18868), the axis is tilted to one side. For straight cutters (for example, through cutters according to GOST 18878), the axis has no deviations.

Also, turning cutters are classified as prefabricated or brazed (welded on) according to the type of connection between their rod and the metal-cutting part. It is easier to make welded lathe tools, but their working potential is usually less than that of welded cutters. Note that high-speed tools are always made using welding, and other turning tools can be either prefabricated or welded.

3 How to sharpen a cutting tool for a lathe?

Any turning cutters, with the exception of those made with disposable replaceable inserts, are periodically sharpened. This operation provides them with the required angles and the shape required by the technological process. Sharpening of turning tools at large enterprises is carried out using special units. Such work in factories is carried out by separate departments.

At home, as well as in small enterprises, sharpening of cutters is carried out using different types of devices, chemical reagents and grinding wheels. The simplest and most inexpensive way to return a tool to its operating parameters is to sharpen it on a simple sharpening unit or on a manual sharpener using abrasive wheels.

Manual sharpening is significantly inferior in quality to machine sharpening, but if there is no other option, it is quite possible to use a manual sharpener. The main thing here is to choose the right grinding wheel. Green carborundum wheels are optimal for sharpening carbide tools. It is advisable to sharpen turning cutters made of ordinary carbon or high-speed alloys with medium-hard corundum wheels.

We recommend performing the sharpening process with cooling (you need to evenly supply cold water to the place where the wheel comes into contact with the tool being processed). Dry sharpening is also allowed, but then after the operation the cutter cannot be immersed in cold water due to the high risk of cracks, leading to increased fragility of the cutting turning device.

The standard sharpening scheme is as follows: first the rear main edge is processed, then the rear auxiliary edge and then the front. At the final stage, the tip of the cutter (the radius of its curvature) is sharpened. It is important to constantly move the tool being sharpened along the surface of the grinding wheel, trying to lightly press it against the abrasive.

A mandatory operation after sharpening is the finishing of the cutter, or rather its cutting edges - areas near the edge up to four millimeters wide. Carbide turning tools are finished using copper whetstones lubricated with a special paste or a composition of kerosene and boron carbide. Other types of cutters are treated with a low level of abrasive whetstone soaked in machine oil or kerosene.

Sharpening the cutter is necessary to give the required shape and angle to the working surface. It is performed when the permissible wear parameters of the cutter are exceeded, or before starting work with a new tool. This operation allows you to significantly extend the life of the equipment, but requires strict adherence to the work technology.

When is sharpening necessary?

During the turning process, friction occurs between chips on the front surface of the tool and the workpiece against the rear surface in the cutting zone. With a simultaneous significant increase in temperature, gradual wear of the part occurs.

If the maximum permissible wear value is exceeded, the cutter cannot be used for further work and requires sharpening and finishing on the front and rear surfaces.

The permissible amount of wear is indicated in the table below

Sharpening tool

For abrasive sharpening of the cutter, a sharpening machine or lathe can be used. For carbide tools, green carborundum of medium hardness is used. For initial processing, the abrasive value of the wheel should be 36-46, at the end of the process - 60-80. For high quality sharpening, a whole circle is required, without defects and geometry violations.

Diamond wheels are also widely used for sharpening turning tools, which ensures high cleanliness of cutting surfaces. In comparison with carborundum wheels, the surface cleanliness of the cutter increases by two classes, and work productivity increases. The use of diamond wheels also increases the service life of the tool - the possible number of cutter regrinds increases by 20-30%. But it should be taken into account that it is economically feasible to use sharpening with a diamond tool with an allowance of no more than 0.2 mm. For larger values, preliminary sharpening with a carborundum wheel is recommended.

Order and features

Depending on the nature of wear and the design of the equipment, sharpening is carried out on the front, back or both surfaces. The figure below shows all the surfaces of a turning tool

For standard cutters, as a rule, sharpening is used on all cutting surfaces. With minor wear, only the geometry of the rear surface is restored. Equipment for multi-cutting machines is restored only on the back surface, shaped – only on the front.

Standard sharpening order:

Main back surface.
Auxiliary back surface.
Front surface.
End radius.

The back surface sharpening parameters are shown in the figure below.

Figure (a) shows the back surface with one sharpening plane, figure (b) shows several. When brazing carbide inserts, the rear surface has three planes:

along a chamfer with a height of not less than 1.5 mm at an angle a;
along the remaining height at an angle a+3°;
along the holder at an angle a+5°.

Sharpening the front surface of carbide cutters has many more varieties (see figure below).

Basic forms:

Flat with a positive rake angle (a).
Flat with a negative angle (b).
Curvilinear with a negative angle (c).
Flat with negative angle for roughing (d).
Curved with a negative angle for stainless steels (d), and other materials (e)

During the sharpening process, it is necessary that the cutting edge of the tool being processed is located on the line of the center of the sharpening machine or below by no more than 3-5 mm. The direction of rotation of the circle should ensure that the plate is pressed against the holder, i.e., it should go towards the plate. During operation, a continuous supply of coolant is desirable. With periodic cooling, overstressing of the material structure and the appearance of microcracks is possible.

When sharpening, light pressure and constant movement along the surface of the wheel are required to form a smooth surface. After sharpening is completed, the geometry of the tool is checked using templates or special instruments.

Tool finishing

After sharpening, sequential grinding of the working surfaces is necessary in the same order as sharpening was carried out. When finishing, it is necessary to remove all roughness and polish the surface to a mirror shine. The cleaner the surface, the lower the friction during turning and the higher the tool life.

Finishing is carried out using boron carbide abrasive pastes on a rotating cast iron disk (no more than 2 m/s). GOI paste or other special polishing materials can be used. For polishing, paste is applied to the disc. Further, when the disk rotates, the cutter is pressed and the grains of the abrasive paste smooth out the existing roughness. Thus, the geometry and original cleanliness of the working surface of the cutter are completely restored, and its suitability for further use is ensured.

The cutter is the main working element of any lathe, through which part of the metal is removed from the workpiece, which is necessary to obtain the part of the required size and shape. In the industrial sector, the most common are turning tools, which we will discuss in this article.

The publication examines the structure and dimensions of turning cutters, studies their classification and varieties, and also provides recommendations for sharpening cutting tools at home.

1 Design features

Any turning cutter consists of two elements - the head and the rod that holds it. The rod is used to secure the cutting head in the seat of the lathe; it can have a square or rectangular cross-section.

Let's look at the most common rod sizes:

square: 40, 32, 25, 20, 16, 10, 8, 6, 4 mm;
rectangular: 63*50, 50*32, 40*25, 32*20, 25*20, 25*16, 20*16, 20*12, 15*10.

The main working part of the cutter is its head. This design consists of several planes that are brought together at a strictly specified angle, which allows the same cutter to perform many metalworking operations.

You can see the standard device of a turning cutter in the diagram; its typical design consists of the following main components:

back angle (a);
rake angle (Y);
taper angle (B);
cutting angle (Q);
leading angle (F)

The main clearance angle is designated by the nomenclature “Alpha”, it is the angle between the cutting plane and the back side of the cutter. This element performs an important functional task - it reduces the friction force of the back side of the cutter on the workpiece, which ensures minimal surface roughness of the part. The smaller the relief angle, the more the cutter wears out and the worse the processing accuracy. In practice, the relief angle is reduced when working with hard steel and increased when working on soft metals.

Rake angle (Y - gamma) is the angle between the front side of the cutter and the main cutting edge. A correctly selected rake angle ensures subtle removal of the layer of metal being removed, without crushing the underlying layer of steel. When this angle is exceeded by 5 degrees or more from the norm, the strength of the cutting edge is significantly reduced, which leads to a reduction in its service life by 3-4 times.

The main angle in the plan (F - phi) is the edge whose parameters influence the nature of metal cutting the most. When this angle changes, the thickness of the layer of cut metal changes, which makes it possible to achieve different types of cuts with the same force and feed speed of the cutter. The smaller the angle F, the stronger the edge, but this requires a significant increase in feed force, which can lead to vibration during processing.

1.1 Classification and types of incisors

According to the provisions of current GOSTs, turning cutters are classified into varieties according to such parameters as type of design, build quality, installation method, feed direction and processing method. Let's consider the types of cutters depending on their design:

Solid - cutters in which the shaft and head are monolithic; this is the most expensive type of cutting tools. For their production, carbon types of steel are used, which ensures maximum wear resistance of the structure.
Welded - the head is fixed to the rod by welding. The quality of the tool directly depends on the correctness of welding, non-compliance with which technology causes microcracks to appear in the connecting seam, leading to rapid deformation of the cutter.
With mechanical connection. This fixation method is mainly used in the production of cutters made of ceramic materials, but there are also mechanical cutters made of adjustable steel, the design of which allows you to change the position of the head in relation to the rod.

Depending on the quality of metalworking, there are 3 types of cutters - rough, semi-finish and finishing. Roughing tools allow processing at high speeds, and they are also capable of removing the thickest layer of metal. Such cutters are distinguished by high mechanical strength, they are resistant to heat and wear, but the quality of processing is quite low. Semi-finishing and finishing cutters are used for finishing the workpiece after roughing. They are designed for feeding at low speed and removing a layer of chips of minimal thickness.

The cutting tool is also classified according to the method of installation in the lathe, depending on which the cutters are radial and tangential:

radial ones are mounted at an angle of 90 degrees to the plane of the workpiece, which makes it possible to use types of cutting edges that are more convenient to sharpen;
tangential cutters are mounted at an angle that differs from a right angle; they are characterized by a complicated installation pattern, but at the same time they make it possible to obtain the highest quality chip removal.

Depending on which side in relation to the surface being processed the cutting edge of the head is located, the cutters are classified into right and left. Tools are also divided into types according to the placement of the cutting edge relative to the holder (rod) into straight, drawn, curved and bent.

However, the main parameter for classifying cutting tools for lathes is the processing method, according to which the cutter can be:

pass-through - designed to perform such technological operations as turning and trimming, mounted on machines with longitudinal and transverse feed;
scoring - installed exclusively on machines with cross feed;
cutting - for machines with cross feed, used for processing the ends and turning annular grooves;
boring - used for processing blind and through holes;
shaped - designed for chamfering and processing shaped surfaces;
threaded - can be round, straight or curved, used for cutting external and internal threads.

Also, the classification of cutters is carried out based on the material of their manufacture. There are three groups - from hard alloys (tungsten, titanium-tungsten and tantalum-tungsten), from high-speed and carbon steel. Titanium-tungsten cutters are universal and are suitable for processing any type of metal.

1.2 Device for sharpening turning tools (video)

The key parameters characterizing the performance capabilities of any set of metal turning tools are:

geometry of cutting edges;
resistance to deformation and vibration of edges and rod;
material of manufacture;
method of installing the structure in the tool holder;
method of removing chips;
geometric dimensions of the tool;
quality of processing.

It is the ratio of these factors that determines the suitability of a cutter for a specific processing mode. When choosing a set of metal turning tools, first decide which grade of steel you will process most often.

Then you need to determine the priority requirements for processing - this can be the accuracy of removal (thickness of the chip layer and compliance with the geometric dimensions of the processed parts) or its quality (lack of roughness, smoothness of the surface). Understanding these parameters allows you to correctly determine the required type of cutters in accordance with their characteristics specified by the manufacturer in the product passport.

Sharpening of cutters during their operation is required regularly, since even products made from the most durable grades of steel wear out over time. For sharpening, it is necessary to use special equipment - a sharpening and grinding machine, and the unit must be equipped with a constant cooling system.

Such machines are equipped with two working wheels: the first is made of silicon carbide (used for sharpening high-speed steel products), the second is made of electrocorundum (for working with carbide tools). When sharpening a cutter with your own hands, you first need to process the main surface, after which the rear and auxiliary planes are sharpened, and lastly the front surface is removed until a perfectly smooth cutting edge is obtained. Checking sharpening angles is carried out using standard templates, which can be purchased at specialized stores.