Where can I sharpen a cylindrical cutter? Sharpening and production of hob cutters. Hardware requirements

Milling cutter sharpening operations maintain the technical and physical characteristics of parts, thereby extending their working life. There are many approaches to performing such activities, the choice among which is determined by the nature of operation and the design of the element. The wear rate of a cutter largely depends on its design, based on which the technician selects maintenance regimes.

For example, the selection of a method for regrinding high-speed parts is based on the wear of the front surface. On the other hand, flank sharpening of cutters is more suitable for shaped elements. Therefore, it is important to take into account as many operational factors as possible that will allow you to right choice processing techniques.

Types of cutters

Such elements are widely used in the processing of parts on copying, moulding, tenoning, milling and other machines. As a rule, this is woodworking equipment, although there are also parts for working with metal workpieces. Milling cutters vary in size, shape and purpose.

In general, there are two categories of elements - end and mounted. The first ones are distinguished by the presence of a shank, which is fixed in a special spindle niche. Products of the second group have a central hole, which allows them to be mounted on the working spindle and securely fixed. Accordingly, such sharpening of cutters differs more high level quality, not to mention ease of handling of parts for the operator. Attachment elements can be composite, solid or prefabricated.

A feature of this group is the ability to form a cutting tool from several milling parts. It is also worth noting the category of end mills, which can be prefabricated or solid. Elements are also divided according to the quality of the backed processing. Thus, sharpening of cutters with backed surfaces is carried out along the front edge in order to maintain the basic angular parameters.

Milling cutter maintenance

Despite the use of high-strength alloys in the manufacture of cutters, long time operation leads to abrasion and deformation of the edges. Over time, worn-out elements are disposed of, but before the expiration of the working life, the master can restore the characteristics of the part using maintenance measures. It is important to consider that sharpening cutters allows not only to give them the same geometry, which ensures high-quality work. This procedure also increases the durability of the element, reducing tool consumption. But this does not mean that any cutter can be restored in this way.

Technologists do not recommend bringing the tool to a state of complete wear. Manufacturers of cutters indicate in the markings technical and operational values ​​that are limiting for a specific element, and after they are overcome, the cutting edges cannot be restored.

sharpening process

To perform sharpening, special milling machines, equipped with spindles with an average rotation speed of up to 24,000 rpm. Before starting work on them, the master balances the cutters. It can be carried out in two ways - dynamic and static. In the first case, the procedure is performed on a special machine, which provides not only balancing of the force, but also the moment acting on the cutter during rotation. This technique is especially relevant for cases when sharpening a cutter for metal.

Balancing machines using the static method only involves balancing the force acting on the cutter. The element is fixed in the frame, after which it is balanced through a device consisting of two horizontal guide knives. Direct sharpening is carried out on special high-precision equipment.

The machines are produced in different configurations, involving both manual and automatic control. Common to all units of this type is the presence on the guides work surface. This design solution makes it possible to achieve high accuracy of element movement, usually with an error of 0.005 mm.

Hardware requirements

To provide high-quality sharpening cutters, you should not only use equipment suitable for this task, but also prepare it correctly. First of all, equipment spindles must have sufficient vibration resistance, rotate freely and have minimal runout. Next, the feed mechanism must operate stably in all directions provided for by the design without delays and with minimal gaps. The elevation angle settings are of great importance - this parameter should also have high accuracy. For example, sharpening a hob cutter, which is performed on automatic machines, requires setting both a certain helix angle and a helical groove pitch. If grinding wheels are used, it is important to ensure a reliable fit of the replaceable washers and spindles, due to which the working element is accurately seated.

End mill machining

Processing of end elements is most often done manually using universal sharpening equipment. Typically, this technique is used to update the performance of a helical tooth tool. In many ways, sharpening end mills resembles a similar update cylindrical cutters using a cup circle. This applies to operations that involve installing the end mill in the center of the seat. Also, similar sharpening is performed on semi-automatic models. In this case, end mills with a diameter of 14 to 50 mm can be serviced. In this case, the treatment is suitable for both the back and front surfaces.

Sharpening end mills

Mills made of and some elements equipped with carbide plates are sharpened in assembled form. The main flank surface of the end mill is sharpened with a grinding cup wheel. Before performing the same operation on the plane of the auxiliary rear side, the element is first installed so that its cutting edge is in a horizontal position. After this, the cutter axis rotates horizontally and at the same time tilts in the vertical plane. Unlike the scheme for sharpening end mills, in this case the position of the workpiece is changed several times. Work with the front surface of the tooth can be carried out with the end part of the grinding disc wheel or with a disk wheel from the peripheral side.

Working with disc cutters

On the rear main surface, the processing of the disk elements is carried out using a cup circle. The auxiliary back surface is made by analogy with end mills, that is, by turning the cutting edges horizontally. At the same time, the peculiarities of processing the end teeth of such a tool are noted. In this case, sharpening disk cutters is performed along the front surface so that the teeth being processed are directed upward. The cutter itself at this moment should occupy a vertical position. The vertical inclination angle of the element axis must correspond to the position of the main cutting edge.

Features of sharpening wood cutters

End shaped parts are sharpened without special tools, usually using a thin diamond whetstone. This element either lies on the edge of the work table, or, if the cutter has a deep recess, is fixed additional tool. The cutter is inserted along a fixed block. During processing, the block is periodically moistened with water. When the procedure is completed, the master thoroughly washes and dries the product. As the front surfaces grind down, the edge becomes sharper, but the diameter of the tool decreases. If the cutter has a guide bearing, it must first be removed and then the operation can be continued. The fact is that sharpening a wood cutter together with a ruined bearing can lead to damage to the element. It is also necessary to clean the tool from any remaining wood resins using a special solvent.

Features of sharpening cutters for metal

Such elements are less common and at the same time require less effort in the preparation process. Processing is carried out using grinding wheels of suitable grain size. The materials may be different, in particular, it is common to use parts made of ordinary or white electrocorundum. If you plan to sharpen end mills for metal made from tool steel, then it is recommended to choose electrocorundum discs. For products with more high performance It is advisable to use CBN wheels. The most productive and efficient sharpening parts are made of silicon carbide. They are used to service cutters made of hard alloys. Before work, the abrasive is cooled, since high temperature loads during the operation can negatively affect the structure of the wheel.

Processing of backed cutters

Relief elements are used in cases where it is necessary to increase the stability of the cutting part and reduce surface roughness. The teeth of the backed cutter are processed along the front surface in such a way that after regrinding in the radial section, the profile of the functional edge retains its original parameters until the part is fully used. Sharpening of such cutters is also carried out in compliance with a strictly established rake angle. When processing sharpened elements, it is necessary to maintain a constant sharpening angle.

Finishing of cutters

In essence, this is an operation designed to correct the result obtained during the main sharpening process. As a rule, finishing is carried out in order to ensure optimal roughness indicators or in cases where it is necessary to adjust the sharpening angle of a cutter with working edges. Abrasive and diamond finishing techniques are quite common. In the first case, it is assumed that fine-grained wheels made of silicon carbide will be used, and in the second case, diamond discs on a bakelite bond will be used. Both techniques can handle, among other things, carbide tools.

Sharpening quality control

During the inspection process, the master evaluates the geometric parameters cutting surfaces for compliance technical requirements. In particular, the runout of the cutter is determined, as well as the degree of roughness of the finished or sharpened planes. Auxiliary devices can be used to control parameters directly at the workplace. For example, if you sharpened an end mill according to wood material, then the specialist can measure the angles along the working edges. For this purpose, a protractor is used, the scale of which is presented in the shape of an arc. Special ones are also used to evaluate other parameters; again, most of them are focused on checking the geometric data of the cutter.

Conclusion

Need for machining cutting tool is preserved even in centuries high technology. The only change in this regard has been with the milling equipment control systems. Automatic devices have appeared that make it possible to optimize the process of handling workpieces. However, cutters, bits and other processing metal elements still done with abrasives. Of course, there are alternative technologies that make it possible to restore the geometry of parts, but we cannot talk about their widespread use yet. This applies to laser technologies, hydrodynamic machines, as well as installations that have a thermal effect. At this stage of their development, for economic reasons, many enterprises still give preference traditional methods sharpening.

Milling cutter is a tool used for processing various products. Milling cutters of various types are used, which allow changing external and internal surfaces with the required accuracy. To achieve high productivity, the cutter must be of high quality - be sharply sharpened. Sharpening of ends, wood, plastic, glass is carried out using special machines and equipment.

Tool sharpening

Sharpening is carried out to restore cutting ability, with operations performed contour-wise and separately.

Cutters received for sharpening are usually pre-ground on a cylindrical surface using a cylindrical grinding machine to eliminate damage, followed by further sharpening of the back or front of the teeth.

End mills with pointed teeth are sharpened along the back surface with a special disk- or cup-shaped wheel. To do this, install the circle relative to the axis at an angle of 89°, which allows you to achieve the required contact between the contacting surfaces.
When sharpening the back surfaces of end mills, 2 main methods are used:

• polyelement;
• contour.

When using the multi-element method, the cutting edges are sharpened separately. First, the main surfaces of all teeth are sharpened, then the auxiliary and transitional ones.
At contour method– sharpening is performed sequentially on each tooth in one operation. A single-turn sharpening method is also used, when the cutting edges are processed in one operation. All teeth are sharpened in one revolution and the allowance is removed using a grinding operation.

Types of Tools Used

Used in industrial enterprises various types tool:

1. Cylindrical - for processing workpieces using machines equipped with a horizontal spindle.
2. Face - for milling workpieces on machines with a vertical spindle.
3. End - for driving ledges, recesses, contours (curvilinear). Used on installations for vertical milling.
4. Disc - for driving grooves and grooves on horizontal machines.
5. Keyed – for making grooves on machines with a vertical spindle.
6. Angular – for milling planes (inclined), grooves, bevels.
7. Shaped – when processing shaped surfaces.

To process workpieces, equipment is used that is designed for the following work:

• for metal;
• on wood.

Milling cutters with appropriate equipment are usually produced as sets with mounting dimensions for fasteners of different diameters. In order for the cutter to be used for a long period, it must always be sharpened, and when carrying out a working operation it is necessary temperature regime, preventing overheating, which reduces their strength characteristics.

Using hob sharpening equipment

When processing workpieces, hobs are most often used.

The characteristics of hob cutters are strictly regulated by GOST 9324-60 and are produced:

• whole;
• prefabricated (welded, plug-in).

Prefabricated hobs (for modules from 10 to 16) are used with insert combs, which are made of high-speed cast steel or forged.
Hobs (for modules 18 to 30) are manufactured by welding and mounting carbon steel teeth on a base.

When using hobs for cutting cylindrical gear wheels the working parts of the tooth wear unevenly.

To increase the service life of hob cutters, a height correction method is proposed by changing the shape of the spatial curve characterizing the working process. The method of axial displacement of the tool is also used, which increases the speed of operations with an increase in the service life of hob cutters.

The process of sharpening backed hob cutters is carried out along the front part, and sharpened ones are carried out along the back surface of the tooth. After finishing the sharpening process, measurements are taken:

• front surface profile;
• circumferential pitch;
• compliance of chip flutes.

Types of equipment used for fixing tools

The equipment used to fasten the tool is divided into 2 types:

• nozzle;
• end

The end equipment is attached using a collet and a chuck, and the attachment equipment is used by installing it on a spindle using a special mandrel.
To fasten the tool, 2 types of mandrels are produced:

• center;
• terminal

Center mandrels are produced with a conical shank, which has dimensions corresponding to the hole in the spindle, and are produced in 2 types 7:24 and Morse taper.
When using this type of mandrel, it is allowed to install several cutting tools with fixation with special rings.
When using a cylindrical end mill, a chuck with a collet is required. Typically, the equipment includes 7-11 collets, allowing you to select the required size for reliable fixation.

Equipment for fixing the workpiece

To carry out the milling process, it is necessary to fix the workpiece, for which the following are used:

• rotary tables;
• vice;
• clamps.

Round rotary tables are used for milling operations on workpieces with a curved surface.
This type of table has a wide range of offsets:

• rotation;
• changing the angle of the table plane;
• Possibility of processing products in a vertical position.

Clamps or clamps allow you to fix products using special elements, which in turn are attached to the table using bolts and nuts. To fix small-sized workpieces, a simple vice with a rotating mechanism is used.

Using Accessories

To fix cylindrical parts, a three-jaw chuck and special centers are used, which, with the help of clamps and steady rests, carry out fixation, as well as use dividing heads. These devices are used to process parts at a given angle during rotation.
The dividing head consists of the following elements:

• housings;
• rotary pads;
• spindle.

A three-jaw chuck is attached to the spindle, designed to fix the workpiece; the other end rests against the headstock. The block can rotate and lock at the required angle. When processing a long workpiece, steady rests are used for fixation.

Today, a fairly large number of milling cutters of various sizes are produced. They can be classified according to functional and design qualities.

Sharpening of end mills is carried out using special devices for such tools. In some cases, sharpening can be done manually.

The cutters have a relatively large length and uneven teeth for cutting. During the sharpening process, you will need to take care of the movement of the base of the wheel along the edge. In this case, you will need to sharpen shaped cutters that have a backed corner. You should know that sharpening is quite difficult. To preserve the profile of the structure and facilitate the sharpening process, the backed teeth will need to be sharpened exclusively along the front base. Sharp teeth, which have a straight or curved shape, must be sharpened exclusively along the rear base. Slotting and parting cutters can be sharpened along the front and back bases of the teeth.

Geometry of cutter teeth

Geometry of the cutter teeth: a - sharpened tooth, b - backed tooth.

To sharpen correctly, you will need to know the geometry of the cutter teeth. The design of the teeth distinguishes between cutters with backed and sharp teeth. In the latter, the part of the rear base, which is adjacent to the cutting edge, is a plane. Teeth with sharp ends are in most cases sharpened along the back base, but they can also be sharpened along the front base of the tooth.

The backed teeth that come with the end mills have a back base that follows an Archimedes spiral. It is quite difficult to process a shaped base technologically, so you can sharpen cutters with backed teeth exclusively on the front base.

Regardless of the number of teeth in the cutter, each of them can be considered as a separate tooth, which is characterized by typical parameters for a tooth - the angles of the front and back, the size of the sharpening area, and the angle of inclination of the teeth.

The sharpening platform is an element of the rear base of the tooth, which is subjected to grinding during the sharpening process along the rear base. The maximum wear of the teeth will occur along this base. Its size affects the magnitude of the friction force between the tool and the workpiece, so the base must be maintained in a specific range.

Scheme for sharpening prefabricated cutters on a universal sharpening machine.

The main rake angle is the angle between the tangent to the front base and the base of the axis. It can be measured in a plane that will pass through this point perpendicular to the main cutting edge.

The main relief angle is the angle between the tangent to the rear base at a given point of the main cutting edge and the tangent to the plane of rotation of this point. This angle helps reduce friction between the tool and the workpiece.

Using the auxiliary relief angle, you can characterize the large gap between the milled base and the body of the tooth. It is necessary to sharpen a tool at an additional angle when there is a specific amount of damage to the tool and an increase in the sharpening area. The purpose of this action is to reduce friction between the tooth and the workpiece being milled. You should be aware that not all tools of this type have this angle.

Return to contents

How to sharpen end mills for woodworking?

The shape of the teeth can be straight or helical. The inclination of the tool teeth can be characterized as the angle between the developed edge of the screw type and the axial part of the tool.

The values ​​of the tooth angles will depend on the type of tool, the grade of alloy and steel from which it is made, as well as the type of material for which the tool is intended for milling.

When milling viscous materials, the main rake angle should be selected in the range of 15-20° or more. Carbide tools for milling steel will have an angle of 0° or -5°. The clearance angle varies over a wide range.

Items you will need:

1. Diamond beam.
2. Table.
3. Water or soap and water.
4. Solvent.
5. Abrasive paper.
6. Hardwood plank or steel strip.
7. Abrasive wheel.

It is possible to sharpen shaped end mills without special sharpening devices, along the front base, with a thin diamond bar. The beam must be installed on the extreme part of the table. If the tool has a large recess, then the tool must be secured along the table.

Table of heat resistance of various materials, °C.

When sharpening, the beam will need to be wetted clean water or a solution with soap. After sharpening, the tool will need to be washed and dried.

As the front base is sharpened, the edge will become sharper, but the diameter of the tool will not decrease much.

If a bearing is installed on the tool, then the first step is to dismantle it and then sharpen it. An attempt to save time in this case may result in a damaged bearing and a non-functional cutter.

It is imperative to clean the cutter from excess resin from the trees. It is best to use a solvent for this.

Return to contents

In the process of sharpening tools, you will need to use bars of different grain sizes. The grain size will depend on the thickness of the layer of material being removed and the required cleanliness of the base. Before sharpening, you will need to make sure that the beam has the appropriate shape.

Figure 1. Shapes of grinding wheels.

If the cutter teeth are made of relatively soft material, instead of timber, you can use abrasive paper, which is glued to a flat base. As a base, you can use a hardwood plank or a steel strip.

End mills for milling wood are sharpened on a special device with a low rotation speed of the wheel. In this case, you will need to use a suitable abrasive wheel.

Return to contents

Sharpening wheels

Sharpening of modular cutters can be done with wheels made of white or ordinary electrocorundum, diamond and others. For example, using electrocorundum wheels, you can perform high-quality sharpening of cutters for working with metal and wood, which are made from tool steel or other steel of standard performance. CBN wheels make it possible to sharpen high-performance steel structures. Silicon carbide and diamond wheels are used for sharpening cutters made of hard metals.

By increasing the temperature, the hardness of such a device decreases. A temperature of 1000°C can reduce the hardness by almost 2 times. At a temperature of 1300°C, this figure will decrease by about 6 times.

Figure 2. Sharpening the end mill: a - the main cutting edge, b - the auxiliary cutting edge, c - installation diagram of the cutter for sharpening the teeth of the auxiliary cutting edge.

Using water to reduce the temperature in most cases leads to rust on the workpieces and corners of the machine. To eliminate corrosion, you need to add soap and some electrolytes to the water, which can form films for protection. When sanding, a solution with soap or soda is almost always used. If fine grinding is performed, a low-concentration emulsion should be used.

To increase the quality of grinding with an abrasive wheel and reduce significant damage, it is recommended to select the maximum grain size that can provide the required cleanliness class for the base of the cutter used.

The peripheral speed of the wheel when sharpening hard metal teeth should be approximately 15-18 m/s. For example, when using a wheel with a diameter of 12.5 cm, the engine rotation speed should be approximately 1600-2700 rpm. If you need to sharpen more brittle materials, the actions need to be performed at a lower speed. When using hard metal tools, harsh conditions result in high stresses and cracks, and in some cases, damage to the cutting edges. In this case, wheel wear will increase.

The shape of the wheel for sharpening the back angle of teeth on a cylindrical base should be cup or disc-shaped. To sharpen the front corner, you need to use a disc-shaped or flat-shaped wheel.

Existing forms of grinding wheels can be seen in (Fig. 1).

Domestic and foreign manufacturers produce hundreds of types and thousands of standard sizes of all kinds of milling cutters, which are classified according to technological characteristics and design features.

Sharpening is carried out on specialized and universal machines for sharpening cutters, less often by hand.

Milling cutter material

For the manufacture of cutters they use various materials: carbon and alloy tool steels, high-speed tool steels, hard alloys, mineral ceramics, CBN, diamonds.

The types of tool steels used are U7A, U8A, U9A, KhG, KhV5, 9KhS, KhVG, etc.

High-speed tool steel used for the manufacture of cutters is divided into steel of normal productivity (R6M5, R9, R12, R18, etc.) and increased productivity. The last category includes steels alloyed with cobalt, vanadium, tungsten and molybdenum (R6M3, R18F2K5, R9F2K10, R9F2K5, etc.).

Carbide alloys from which cutter teeth are made are produced in the form of plates standard sizes and forms attached to the cutter body by high-temperature soldering (for example, PSR-40 silver solder) or using threaded connections (prefabricated cutters). They consist of tungsten, titanium and tantalum carbides bonded with cobalt. Cutters made from tungsten-cobalt alloys (VK2, VK3, VK6, VK6M, VK8, etc.) are used for processing cast iron, non-ferrous metals, and non-metallic materials. Titanium-tungsten-cobalt alloys (T5K10, T15K6, T14K8, T30K4, etc.) are less durable than VK type alloys, but they have higher wear resistance when processing parts made of various types steel. Three-carbide alloys, consisting of tungsten, tantalum, titanium and cobalt carbides (TT7K12, etc.), are also mainly used for processing steels.

If a cutter has cutters made of soldered plates, this does not mean that they are made of hard alloy. They, for example, can be made of high-speed steel.

Based on the design of the teeth, cutters with pointed (sharpened) and backed teeth are distinguished. For pointed teeth, the part of the rear surface with width f adjacent to the cutting edge is a plane. Pointed teeth are sharpened along the back surface. Although, if necessary, they can be sharpened along the front surface of the tooth.

Geometry of cutter teeth: a - sharpened tooth, b - backed tooth

The back surface of the backed teeth, which are equipped with shaped cutters, follows an Archimedean spiral. Since processing a shaped surface is very difficult technologically, sharpening of cutters with backed teeth is carried out along the front surface.

Regardless of how many teeth there are on the cutter, each of them can be considered as a separate cutter, characterized by standard parameters for any cutter - front (γ) and back (α) angles, the size of the ground area (f), the angle of inclination of the teeth (λ) .

Site f is a part of the back surface of the tooth that is subjected to grinding when sharpening along the back surface. The main wear of the teeth occurs along this surface; its size affects the magnitude of the friction force between the cutter and the workpiece, so it must be maintained within a certain range.

Main rake angle γ- the angle between the tangent to the front surface and the axial plane. It is measured in a plane that passes through a given point perpendicular to the main cutting edge.

Main relief angle α- the angle between the tangent to the rear surface at the point in question of the main cutting edge and the tangent to the circle of rotation of this point. The function of angle α is to reduce friction between the cutter and the workpiece.

Auxiliary relief angle α 1 characterizes the increased clearance between the treated surface and the body of the tooth. The need to sharpen cutters at an auxiliary angle arises with a certain amount of cutter wear and an increase in the area f. Its purpose is to reduce friction between the tooth and the material being processed. Not all cutters have this angle.

Depending on the shape and direction of the cutting edge, the teeth can be straight or helical. The inclination of the cutter teeth is characterized by angle λ between the deployed helical edge and the axis of the cutter.

The angle values ​​depend on the type of cutter, the grade of alloy or steel from which it is made, and the type of material it is intended for processing.

When processing viscous materials, the main rake angle is selected within 10-20° or more. U carbide cutters for processing steels it is close to zero or even negative. The clearance angle can also vary widely.

Shaped end mills can be sharpened without a special tool for sharpening cutters, along the front surface, with a thin diamond stone. The block either lies on the edge of the table, or, if the cutter has a deep recess, it is secured as shown in the photo below. The cutter is driven along a fixed block.

During the sharpening process, the block is moistened with clean or soapy water. After sharpening, it is washed and dried.

As the front surface grinds down, the edge will become sharper and the diameter of the cutter will decrease slightly.

If the cutter has a guide bearing, it must first be removed (if possible) and only then sharpened. An attempt to save a minute will end in a ruined bearing and a damaged cutter. You also need to clean the cutter from any remaining wood resin using a solvent.

As when sharpening any other tool, you need to use bars of different grain sizes, depending on the thickness of the layer of material being removed and the required cleanliness of the surface. Before sharpening, you need to make sure that the block has the correct shape.

When sharpening each cutter, to maintain symmetry, you should try to make the same number of sharpening movements and with the same pressure.

If the material of the cutter cutters is soft enough, instead of a block, you can use abrasive paper glued to a flat surface (a strip of solid wood or a strip of steel).

Wood end mills can also be sharpened on a grinding machine at low wheel speed using an appropriate abrasive wheel.

Sharpening wheels

Depending on the material from which the cutters are made, they can be sharpened with white or normal alumina wheels, CBN wheels, green silicon carbide wheels, or diamond wheels (PCD). For example, electrocorundum wheels can provide high-quality sharpening of cutters for wood or metal made only from tool or high-speed steel of normal productivity, while CBN wheels are capable of sharpening cutters made of high-speed steel with increased productivity. diamond wheels and green silicon carbide wheels - carbide cutters.

When using abrasive wheels (especially diamond ones), it is advisable to cool them with coolant.

One of the significant disadvantages of diamond is its relatively low temperature stability - at a temperature of about 900°C, diamond burns.

With increasing temperature, the microhardness of abrasive materials decreases. Increasing the temperature to 1000°C reduces the microhardness by almost 2-2.5 times compared to microhardness at room temperature. An increase in temperature to 1300°C causes a decrease in the hardness of abrasive materials by almost 4-6 times.

Using water for cooling can lead to rust on machine parts and components. To eliminate corrosion, soap and certain electrolytes (sodium carbonate, soda ash, trisodium phosphate, sodium nitrite, sodium silicate, etc.) are added to water, which form protective films. For regular sanding, soap and water are most often used. soda solutions, and during finishing grinding - with low-concentrated emulsions.

To increase the productivity of grinding with abrasive wheels and reduce specific wear, you should choose the largest grain size that provides the required class of surface cleanliness of the tool being sharpened.

To select the abrasive grain size, in accordance with the stage of sharpening, you can use the table in the article about sharpening stones.

The peripheral speed of the wheel when sharpening carbide teeth should be about 10-18 m/s. This means that when using a 125mm diameter wheel, the motor speed should be around 1500-2700 rpm. Sharpening of more brittle alloys is carried out at a lower speed from this range. When sharpening carbide tools, the use of harsh conditions leads to the formation of increased stresses and cracks, and sometimes to chipping of cutting edges, which increases wheel wear.

The shape of the circle for sharpening the rear angle of teeth on a cylindrical surface is cup (ChTs or ChK) or disc-shaped (1T, 2T, 3T), the front angle is disc-shaped or flat.

Mill sharpening machine

Taking into account the most difficult cases - spiral teeth, a machine for sharpening cutters must provide rotational and translational movement of the cutter being sharpened. The figure below shows a machine for sharpening end mills E-90 DAREX.

The essence of sharpening an end mill is that when it moves longitudinally relative to the circle, it simultaneously rotates synchronized around its axis. Thanks to this, the sharpened edge is always in contact with the wheel at the same height (the same sharpening angle is ensured). Synchronization of translational and rotational movements is achieved using a copier needle resting on the cavity on the front surface of the tooth. By pressing the tooth to be sharpened against the needle and smoothly moving the cutter in the axial direction, the operator sharpens the tooth to its entire length in one movement.

Sharpening side teeth. In a simplified form, sharpening screw teeth looks like this. The cutter is installed in the collet.

The tracer needle is set to a position where it is at its highest position and its tip touches the outside edge of the end mill flute.

The cutter is installed in its original (extended) position, in which the needle is located near the shank, resting against the tooth groove.

The grinding wheel is moved using the side shift knob to a position where its outer edge coincides with the needle.

The engine is turned on, and the direct feed handle slowly moves the circle towards the cutter until sparking begins. After which, using the feed scale, the thickness of the metal being removed is set (usually 25-50 microns).

Sharpening a tooth to its entire length is done by retracting the spindle with the cutter until the latter comes off the needle. In this case, you need to ensure that the cutter is constantly in contact with the needle. This ensures the rotation of the cutter, which is necessary so that the sharpened edge is in contact with the wheel at the same relative position.

To ensure clean processing, the cutter pass is repeated one more time without changing the thickness of the metal being removed. This completes the processing of one tooth, and a similar operation is repeated for all other teeth. To ensure that all teeth are sharpened equally, you should not change the thickness of the metal being removed, which was initially set using the direct feed knob.

By changing the position of the needle so that its tip rests on different points on the tooth groove (on the edge or in the middle, for example), you can change the values ​​of the angle α and α 1 .

Grinding of end teeth. To sharpen the end teeth, the end mill must be set in a position in which the tooth being sharpened would be positioned strictly horizontally. The E-90 sharpening system is equipped with a graduated ring that allows you to easily and simply install the end teeth horizontally. If you are using a machine for sharpening cutters that is not equipped with a similar mechanism, you can set the horizontality of the teeth using a square.

Sharpening a tooth set horizontally is done by moving the edge grinding wheel along the edge of the tooth. The sharpening angle is adjusted by moving the wheel vertically or by tilting the spindle with the cutter (if possible).

Sharpening quality control

After sharpening, the cutter must be inspected. The presence of chips, scratches, and cracks is checked visually with the naked eye or with a magnifying glass; with the help of instruments, the runout of teeth, angle values, and surface roughness are checked.

The permissible deviations of the front and rear sharpening angles of all cutters are ±1°. Angles can be measured with a special 2URI inclinometer or a pendulum inclinometer.

For standard cutters, the radial runout of two adjacent (σcm) and two opposite (σpr) teeth, as well as the axial runout, is regulated. The permissible values ​​of the radial and face runout of the cutter teeth are given in the table below (for cutters that do not have end teeth, the permissible runout of the supporting ends is indicated).

The quality of sharpening or finishing is checked by external inspection using a magnifying glass. Cutting edges cutters must be free of nicks and gouges.

If there are jagged marks on the surface of the tooth, the protrusions will chip away when the cutter is used, and it will become dull very quickly. You should strive to keep the surface of the tooth very smooth.

The presence of cracks on hard alloy plates is determined using a magnifying glass and wetting the plates with kerosene. In this case, if there are cracks, kerosene comes out.

Video:

When using the content of this site, you need to put active links to this site, visible to users and search robots.