Homemade machine for sharpening metal cutters. Sharpening and regrinding of cutters. Making homemade cutters

For metal, it is represented by two elements: a head and a holder.

The head is the performing part, consisting of a number of planes and cutting edges with a certain angle. Depending on the required type of sharpening, the cutter is given a certain angle.

The holder is responsible for fixing the cutter in the holder of the turning device. It has a square or rectangular shape. There are a number of standard section sizes for each shape.

Varieties of design

There are the following for metal lathe:

• Direct. The holder and head are located on the same or parallel axes.
• Curved. The holder has a bent shape when viewed from the side.
• Bent back. The head is curved towards the holder when viewed from above.
• Retracted. The width of the holder is greater than that and is located on the same axis with the holder or is offset relative to it.

If we rely on the well-known classification of devices in accordance with GOST, they are divided into the following types:

• Having a cutting edge based on a monolithic tool. It can be made from tool steel. Currently, its use is extremely rare.
• Filled with soldered hard alloys. The edge plate is soldered to the head. This is the most common type.
• Plates made of hard alloys, fixed by mechanical means. The cutting plate is fixed to the head using screws and clamps. Replaceable cutters are based on metal and metal-ceramics. This is the rarest species.

Classification according to the direction of the feeding movement

• The left model is fed from the left when taken in the left hand. The main working edge is located above the thumb.
• The right model, accordingly, is fed from the right. The main working edge is located under the thumb. In practice it occurs more often.

Methods for installing the device

A cutter for a metal lathe can differ in the method of installation relative to the surface to be processed:

• Radial view. During processing, the cutter takes a right angle to the axis of the workpiece for processing. This method is widely applicable in industrial enterprises. The cutter has a unified design for mounting on machines. It also has a more convenient choice of geometric positions of the cutting part.
• Tangential. During processing, the cutter is positioned to the workpiece axis at an angle other than straight. It has a more complex method of fastening and is used on turning devices that allow high-purity processing.

Difference in processing method

Cutters can also be divided according to the processing method:

• finishing;
• draft;
• semi-finish;
• for work performed with particular finesse.

The unevenness of the workpiece is influenced by the radius of curvature of the tip of the fixture. A smooth surface is achieved by using a cutter sharpened to a large radius.

Types of turning tools

There are many types of cutters for metal lathes. The most common are:

• Passage. It creates the contours of the part during rotation, and also provides turning and trimming when feeding in the transverse and longitudinal direction.
• The boring type creates a variety of grooves, recesses and holes. Can make through holes.
• The scoring model is used only for the transverse feed direction for turning parts with a stepped shape and end parts.
• Cut-off. Its feed is carried out in the transverse direction relative to the axis of rotation. It produces grooves and grooves around the part and is used to separate the finished product.
• Threaded. Cuts threads of any type on parts with any cross-sectional shape. This type can be curved, straight or round.
• Shaped. It turns parts of complex design and can remove various chamfers from the inside and outside.

A set of cutters for a metal lathe can be purchased in specialized stores or ordered online.

Incisor base

The materials from which devices are made are divided into three categories:

• The first is for cutting attachments used at low speeds. These are tool or carbon metals with a hardening hardness of 60-64. When the temperature of a turning tool increases above 200-240 degrees, the quality of its cutting noticeably decreases, so in practice they are used infrequently. This group includes devices based on chrome-tungsten, chrome-silicon and with a temperature resistance level of up to 300 degrees.
• The second category of cutters will be used at a high level of rotation of the lathe head. The basis of such devices is steel with a high cutting category P12 P9 or R9K5F2. After hardening, the material hardens to 62-65 and retains all its properties at a temperature of 650 degrees. Cannot be wiped for a long time.
• The third category consists of cermet-based cutters. These are carbide devices that operate at high machine speeds and can withstand heating temperatures of up to 1000 degrees. Cast iron and some parts made of non-ferrous alloys are sharpened with devices based on tungsten-cobalt (VK6 for finishing and semi-finishing, VK8 for primary processing). The steel is ground with hard titanium-tungsten-cobalt alloy T15K6. This results in clean processing.

Accessories for benchtop lathes

The cutters have a small cross-section of 8 x 8 and 10 x 10 mm. They are used for processing small-sized parts.

Insert-shaped cutters

The cutter for a metal lathe of category T5 K10 is used for primary and intermittent turning. Replaceable inserts are made from cubic boron nitride for processing metals that are particularly hard, including cast iron. Non-ferrous metals are turned using polycrystalline diamond.

The plates can be replaceable. They are inserted into the holder. Some models contain chipbreakers that perfectly crush chips at low feed rates and surface turning. These types of plates are used for high-finish cutting of stainless steel and other types of steel.

Sharpening cutters

Any types of cutters, in addition to replaceable inserts, must be sharpened from time to time. Sharpening cutters for a metal lathe ensures that the required angles and shapes are achieved. In industrial conditions, it is carried out on specialized units.

This process can be done at home using chemical reagents and grinding wheels. Manual sharpening is inferior in quality to industrial sharpening. The main thing here is the correct selection of the grinding wheel.

For hard alloys, a circle of green carborundum is taken. Turning cutters made of carbon materials are sharpened with corundum wheels.

It is recommended to carry out sharpening by means of cooling (uniform supply of cold water to the point of contact of the wheel with the cutter being processed). You can also dry sharpen, but after this the part should not be immersed in cold water, as it may crack.

Standard sharpening process diagram

First of all, the main back face is subject to processing, then the back auxiliary and only then the front part. At the very end of the process, the top of the fixture (radius of curvature) is processed. The cutter to be sharpened should be constantly moved on the surface of the grinding wheel and lightly pressed against the workpiece.

An obligatory component of the process is the finishing of the cutter, or rather the cutting edges (areas near the edge, the width of which reaches 4 mm).

Devices made of hard alloys are sharpened using copper whetstones, which are lubricated with a special composition in the form of a paste or a mixture of kerosene and boron carbide.

Other types of cutters are sharpened with a low-abrasive whetstone moistened with machine oil or kerosene.

Making homemade cutters

You can also make homemade cutters for a metal lathe. Such devices are based on unnecessary broken drills.

Drill-based alignments do not break. They are especially suitable for older lathes. They are subject to repeated sharpening. Their service life reaches 30 years.

Homemade cutters for a mini metal lathe are made from a segment of a Geller saw. It is cut with a cutting disc.

How to choose the right cutter?

When choosing a cutter, you need to take into account a number of recommendations.

Determine what type of metal you will be working with, what processing operations you are planning and what degree of load the cutter will experience.

Decide what is most important - the accuracy of the geometry of the product or the level of surface treatment. Depending on this, the cutter is selected in accordance with the classifying characteristics and geometric proportions.

Determine for yourself how important it is to ensure the wear resistance of the device and how long it should remain unchanged.

Sharpening turning tools is the processing of the working surface, which consists of giving the required shape and angle to a new or dull tool.

At the end of sharpening, a finishing procedure is carried out, during which the tool is sharpened and the working surface is finally cleaned.

1 Sharpening turning tools and its types

The geometric features of a cutting tool for wood or metal predetermined its most vulnerable cutting tool. But despite this, they are widely used in practice. The process of manufacturing parts on machines, first of all, involves cutting blanks to the required size.

Sharpening the cutting tool must be done carefully so as not to damage the cutting part of the tool.

Large metalworking plants always have sharpeners. In addition, large-scale production includes the presence of boring machines to give the cutters a working condition. In small workshops do it themselves.

Sharpening can be:

• abrasive (grinding wheels);
• chemical-mechanical (metal processing with special compounds);
• using special devices.

For abrasive sharpening, use a jig boring lathe or independently using a grinding stone. Manual sharpening does not allow for high-quality processing of the tool, taking into account the required angles. The complexity of the process is that the heated metal loses its properties. The final result depends on the skill of the turner.

Carbide tools are sharpened using green carborundum. To process steel cutters, use a medium-hard grinding wheel. For primary processing, abrasive whetstones are used (marking 36-46; for the final procedure marking 60-80). Before installing the wheel on the work machine, make sure that it is intact.

Sharpening using the chemical-mechanical method is very effective and fast. The tool acquires a clean, smooth surface without chips or cracks. Used for sharpening large carbide cutters.

Before sharpening, the cutters are treated with a solution of copper sulfate. Thanks to the reagent, a protective layer is formed, which is washed off by abrasive grains from the solution. The process involves using a machine which has a container and a movable grinder. The movements of the fixed cutter are reciprocating, and the pressing pressure on the abrasive surface is 0.15 kg/cm².

On a specialized machine, sharpening is carried out with a white wheel made of electrocorundum (for high-speed tools), a green wheel made of silicon carbide (for carbide tools) and a diamond wheel for final finishing.

1.1 Characteristics of grinding wheels

The diamond wheel can be used for sharpening carbide saw, brazing and parting cutter.

The very small grain structure allows the use of diamond wheels for finishing purposes.

Grain:

• 100/80;
• 125/100;
• 160/125;
• 200/160.

The higher the number, the larger the grain of the circle. Grit 125/100 is one of the most common. Great for and incisors.

The diamond wheel can be in the shape of a bowl, plate or straight profile. When choosing, it is necessary to take into account the shape of the workpiece, area and ease of use of one or another form. For processing circular saws It’s better to take a plate-shaped circle. This type can easily penetrate between teeth and has a pointed edge. To work with a knife blade, a regular circle or cup-shaped one is suitable.

Circles can have a diameter from 125mm-300mm. You need to select it according to your sandpaper, taking into account the fit and outer diameter.

The wide diamond layer is suitable for sharpening large diameter drill bits and wide workpieces. The thicker the layer, the longer the diamond wheel will wear out.

• layer width – 3-20mm;
• layer thickness – 2-5mm.

Grinding wheel markings include:

• device type;
• size;
• abrasive material;
• grain;
• hardness;
• structure;
• bunch;
• speed;
• accuracy;
• imbalance.

Standard Diamond Wheel for emery (marking 125*40*10*3*32):

1. The internal hole size is 32mm.
2. The diameter of the outer circle is 125mm.
3. Depth (cup-shaped circle) – 40mm.
4. Diamond layer – 10mm.
5. Thickness – 3mm.
6. Landing – 32mm.

The grain size is indicated on a separate line.

2 Device for sharpening turning tools

Sharpening tools involves not only wheels, but also the use of additional devices - boring machines.

Jig boring machines bore, drill, countersink, cut internal and external threads, grind cylindrical surfaces and trim ends.

A distinctive feature of the machines is a horizontal (or vertical) spindle, which makes axial feed movements. The necessary tool is fixed into the spindle hole - a boring bar with a cutter, a reamer, a drill, a milling cutter, etc.

Machine types:

• horizontal boring;
• coordinate boring;
• diamond boring;
• vertical boring.

Specialized models of jig boring machines:

1. Jig boring machine 2D450.
2. Jig boring machine 2V440A.
3. Jig boring machine 2431.
4. Jig boring machine 2421.

2.1 Sharpening technology

Sharpening sequence:

1. Main back surface.
2. Auxiliary back surface.
3. Front surface.
4. The radius of curvature of the ring.

At the end, the sharpening angles are checked using a template.

To obtain an even and smooth edge, the tool must be constantly in motion along the grinding surface. With this kind of work, the circles will last longer.

The tool can be processed dry or with water. The flow of water must be sufficient and continuous. A dry tool should not be immersed in water, as this may cause destruction of the working edge.

Finishing is carried out:

• fine-grained whetstone (technical oil is also used);
• copper wheel (boron carbide paste and technical oil are also used).

Finishing can only be done on cutting tools (edge ​​width up to 3mm).

2.2 Safety precautions

1. Do not use grinding wheels whose operation is accompanied by beating.
2. The tool rest should be securely fixed closer to the circle.
3. Use a tool rest to support the cutter.
4. Do not press the cutter too hard (uneven heating can cause cracks; under high pressure the wheel can quickly deteriorate).
5. Do not sharpen without a protective guard.
6. Wear safety glasses.
7. The workplace must have local ventilation.

2.3 Diamond wheel for sharpening tools (video)

Sharpening the cutter consists of giving the shape and the required angle to the working surface. Sharpen new or dull tools. After sharpening, finishing is carried out, during which the tool is sharpened and the working surfaces are finally cleaned.

Types of sharpening

Large metalworking plants specifically maintain a staff of sharpeners and special machines for bringing cutters into working condition. Employees of small workshops have to do this themselves.

Sharpening can be done in several ways:

• abrasive (on grinding wheels);
• chemical-mechanical (metal is treated with special compounds);
• using special devices.

Abrasive sharpening can be carried out on a sharpening machine, lathe or manually on a grinding block. It is very difficult to sharpen a tool manually at the required angles. The process is complicated by the fact that the metal heats up and loses its properties. Therefore, the result directly depends on the skills of the turner and his knowledge of sharpening angles.

Carbide tools are sharpened on green carborundum. Cutters made of various types of steel are processed with grinding wheels made of medium-hard corundum. Primary processing is carried out with whetstones with an abrasive of 36-46, final - 60-80. Before installing the wheel on the lathe, it is necessary to check the integrity. During operation, it can split and injure the worker, as well as ruin the sharpening angle.

The chemical-mechanical method is very effective and fast, provides a clean, smooth surface, and prevents the formation of chips and cracks. Used for sharpening large carbide cutters. They are treated with a solution of copper sulfate. The reagent forms a thin protective layer, which is washed off by the abrasive grains present in the solution. The process takes place in a machine equipped with a container with a movable grinder. The fixed cutter moves back and forth and with a pressure of about 0.15 kg per square meter. the centimeter is pressed against the abrasive surface.

On specialized machines, sharpening of cutters is carried out with white wheels made of electrocorundum (high-speed tools), green wheels made of silicon carbide (carbide), and diamond wheels (for finishing).

Sharpening process

The main flank surface is sharpened first, then the secondary flank surface, the front surface and then the end radius. At the end of the work, the sharpening angles are checked against the template.

To ensure an even and smooth edge, the tool must be constantly moved along the grinding surface. With this type of work, the wheel lasts longer and wears out evenly.

The tool can be processed dry or with constant water cooling. The water flow must be sufficient and continuous. If the tool is sharpened dry, there is no need to periodically water it or dip it in a container of water. This causes cracking of the surface and destruction of the working edge.

Manual finishing is carried out:

• fine-grained whetstone using technical oil, kerosene or - tools made of various types of steel;
• circle made of copper using boron carbide paste and technical oil.

Only the cutting surfaces of the tool are adjusted with an edge width of up to 3 millimeters. It is more efficient to finish the cutters on a machine with a cast iron touchstone. The procedure is simple and does not require much time, but significantly extends the service life and productivity of the instrument. It is important to maintain the required angles!

Videos about sharpening different types of cutters:

Detailed diagrams and sharpening instructions

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.

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 back 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.