Domestic and foreign manufacturers Hundreds of types and thousands of standard sizes of all kinds of cutters are produced, 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 become. 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. For example, they may be from 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 main point in question cutting edge and a tangent to the circle of rotation of a given 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. For 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 special device 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 surface cleanliness. 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 hardwood strip or a strip of steel).
Wood end mills can also be sharpened sharpening 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 can sharpen cutters made of high-speed steel 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 the 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 grinding productivity abrasive wheels and reducing 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
Considering the most complex cases- spiral teeth, the machine for sharpening cutters must provide rotational and forward movement sharpened cutter. 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 copier needle is installed in a position where it is in the very high position, and its tip touches the outer 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 necessary so that the edge being sharpened 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 of the sharpening 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, cracks is checked visually with the naked eye or using 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. Valid values The radial and end 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. The cutting edges of the 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.
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Proper sharpening of a tool reduces its consumption and accordingly increases its service life. Therefore, it is necessary to carefully monitor the condition of the cutting edges and sharpen the tool in a timely manner, avoiding excessive wear and especially breakage.
Sharpening and manufacturing of hobs
The production complex of the Spetsstanmash plant offers a full range of services for the manufacture and repair of metal parts and structures, including: production and sharpening of cutters for metal, wood, cast iron, aluminum, graphite or plastic.
The cutter is important tool in industry and workshops. It is a part of different shapes, with distinctive feature sharp teeth. Its main function is mechanical restoration prepared material.
The operating principle of milling is progressive rotational movement cutter teeth.
Depending on the type of tool used, the result is:
- small grooves or grooves when using end mills;
- milling large surfaces;
- milling baguettes, window frames, gears, etc. using spiral cutters,
- cutting using a disc cutter (plinth, paneling, lining, wall beams, etc.).
An important characteristic of a cutter is the material it is made of, in particular the cutting part. These can be teeth made of high-speed steel, mineral-ceramic, metal-ceramic or diamond.
Diamond cutters are considered the most durable due to their natural physical characteristics. But, they are the most expensive. All other materials become dull after some time during use, especially if used incorrectly. Purchasing new tools requires high costs, but our qualified craftsmen and high-precision modern equipment allow quality to perform this type of repair, such as sharpening knives for cutters of any geometry:
- hob sharpening
- sharpening of disc cutters
- core cutters and other types.
Professional work on sharpening cutters increases the durability of the part and significantly reduces the consumption of cutting teeth.
Sharpening hob cutters: from 600 rub. / PC. (depending on wear)
Minimum sharpening time: from 10 working days
Minimum order amount: 3500 rub.
* The exact cost can be found using the form or by phone
In the modern variety of services presented on the market building materials, it’s easy to find help in sharpening cutters.
But don't rush this work you can do it yourself. This is typical not only for work on sharpening cutters, but also for other types of work.
In a machine for sharpening cutters standard there are two chuck different configurations. One of them is for three feather cutters, and the second is for two and four feather cutters. Make a mistake in in this case difficult, since if the number of cutter feathers is not set correctly, it will not be possible to insert the cutter into the chuck.
Having decided on the choice of chuck, you can proceed to the immediate stages of sharpening the cutters:
- sharpening on a ribbon;
- end sharpening.
Sharpening on a ribbon
You must use one of the corresponding cup sockets. From standard set collet, select the appropriate collet size (8 mm, 10 mm, 12 mm).
We insert the collet into the chuck and secure it with a clamping nut. This procedure is done without any effort; the clamping nut rotates freely and does not need to be tightened.
- In the socket of the glass we set the length of the ribbon to be sharpened. As a rule, this distance is adjusted by unscrewing the screws located in the cup socket. By moving the bottom of the socket up or down, we select the length, and then fix the screws back.
- We install the cutter into the chuck through the upper hole, while pre-setting the diameter of the cutter and the sharpening angle on the adjusting screw. We fix the prepared chuck in the glass, while correctly setting the lines of the cutter in relation to the element being sharpened. That is, the cutter should cling to the pin with its grooves.
- Then turn on the machine and use the feed regulator to move the cutter to grinding wheel before the sound of contact begins, we sharpen the cutter strip on all sides. The metal removal from the cutter being sharpened can be reduced or increased using the regulators installed on the machine. This adjustment is necessary when changing the diameter of the cutter and correcting existing irregularities in the cutter being processed.
Sharpening the end cutter
To sharpen the cutter along the end, you must use the second chuck socket located on the machine.
In this case, you need to perform the previously described steps to set the diameter and length.
- Depending on the hardness of the metal being processed, the settings on the socket are set. How harder metal, the more the socket ring rotates towards the “+” sign.
- Next, turn on the machine, insert the prepared chuck with the cutter into the socket and process the part until the characteristic noise stops. Each groove of the cutter is machined.
- In the additional slot of the machine, the cutter is sharpened from the end, for which the above steps are performed.
- The last operation is processing the rear wall of the cutter, which is performed by inserting a chuck with a cutter into the corresponding slot of the machine.
- Thus, the cutter was sharpened in compliance with all the required geometric features separately and in relation to each other. The sharpening is uniform on all sides.
Do-it-yourself sharpening of cutters
You can perform this procedure yourself and use available tools.
This feature will save money and, if used repeatedly, save valuable time.
- First, we clean the cutter from carbon deposits, for which we use a special liquid, similar to those used to clean car engines. You need to fill the cutter and wait about three minutes, then clean the cutter on all sides with a brush.
- Next, we take a diamond stone and begin to sharpen the cutter along the leading edge (movement of the cutter channel along the diamond stone).
- The block is moistened with ordinary water. After sharpening, you need to wipe the cutter with a cloth.
Quality manual sharpening differs significantly from sharpening using a special machine, but in manual version time is saved.
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. For achievement high performance 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.
With the 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
On industrial enterprises apply Various types tool:
- Cylindrical - for processing workpieces using machines equipped with a horizontal spindle.
- Face - for milling workpieces on machines with a vertical spindle.
- End - for driving ledges, recesses, contours (curvilinear). Used on installations for vertical milling.
- Disc - for driving grooves and grooves on horizontal machines.
- Keyed – for making grooves on machines with a vertical spindle.
- Angular – for milling planes (inclined), grooves, bevels.
- 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 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 to cut cylindrical gears, 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 performed along the front surface, and sharpened ones 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.
Allowed when used of this type install several mandrels 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
For fixing parts having cylindrical shape use a three-jaw chuck and special centers, which, with the help of clamps and steady rests, carry out fixation, as well as the 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.
All photos from the article
Manufacturers now produce many types and sizes of cutters designed for processing different materials, including wood. You can sharpen a dull device with your own hands using a universal or special machine, as well as manually.
Features of cutters
For the production of cutters they are used different materials. Tool steels suitable for wood are: high-speed, alloy and carbon. For processing metal, plastic, ceramics, and stone-like materials, hard alloys, diamonds, CBN, and mineral ceramics are used.
Steel for wood cutters
- The following grades of tool steels are used for cutting wood: U-9-A, U-8-A, U-7-A, KhV-5, 9-KhS, KhG, KhVG.
- High speed steel can be of normal performance. These are brands R-18, R-6-M-5, R-9, R-12, etc. The high-performance metal is alloyed with vanadium, cobalt, molybdenum and tungsten. These are brands R-6-M-3, R-18-F-2-K-5, R-9-F-2-K-10, R-9-F-2-K-5, etc.
Note!
If a cutter has soldered teeth, this does not always mean that they are made of carbide.
It can also be high-speed steel.
Teeth geometry
According to their design, the cutters of milling cutters are divided into sharpened (pointed) and backed.
- For sharply sharpened teeth, the area of the rear surface (width n) adjacent to cutting part, is a plane. Such incisors are sharpened along the back surface. However, if necessary, you can sharpen them along the front edge.
- In backed cutters of shaped cutters, the back surface has the shape of an Archimedes spiral. Processing it is technically very difficult. Therefore, such teeth are sharpened exclusively along the front edge.
Each tooth is a separate incisor.
He has standard parameters: rear (a) and front (y) angles, area of the sharpened surface (n), slope angle (l).
- Platform n is a section of the rear surface of the cutter that is ground during turning. This is where the teeth wear out the most; their size affects the friction force between the cutter and the workpiece. Because of this, this surface should be maintained within the normalized range.
- The leading edge angle (y) is measured between the tangent to the leading edge and the radius of the cutter.
- The main back angle (a) is measured between the tangent to the back edge at the normalized point of the main sawing edge and the tangent to the rotation circle of this point. When this angle decreases, it reduces friction between the workpiece and the cutter.
- Not all cutters have an additional clearance angle (a1). It describes the expanded gap between the cut surface and the body of the cutter. The instructions indicate the need to sharpen this gap with a certain wear of the cutter and expansion of the area n. The purpose of the operation is to reduce friction between the tooth and the workpiece.
- Based on the direction and configuration of the cutting edge, helical or straight teeth are distinguished. Their slope describes the angle (l) between the axis of the tool and the deployed helical edge.
The size of the angle depends on the type of cutter, the grade of its material and the type of workpiece being processed. When cutting wood, the main rake sharpening angle is selected in the range of 10-20 degrees, sometimes more. The back angle also fluctuates within a wide range of values.
Methods for sharpening "wooden" end mills
Wood end shaping tools can be sharpened by hand using a fine diamond stone. The cost of performing this operation by a specialist is also low.
Manual work
- The block should be placed on the edge of the workbench. If the cutter has a deep recess, it must be fixed. The cutter should be driven along the already secured sandpaper.
- During operation, the bar must be cooled with soap or clean water.
- The front part of the cutter is gradually ground down, its edge becomes sharper, and the diameter decreases slightly.
Note!
When the jig has a removable guide bearing, it should be removed before sharpening.
In an attempt to save time, you can ruin it and the entire cutter.
By changing the position of the copier needle so that its end touches various points of the tooth groove (for example, the center, edge), you can change the values of the rear angles a and a1.
Now about sharpening the end cutters.
- For this purpose, the shaped cutter should be placed in a position in which the tooth being sharpened will be in an exactly horizontal position.
- The sharpening system of the E-90 machine has a graduated ring. It makes it possible to very simply position the end cutters strictly horizontally.
- When to use sharpening machine, which does not come with such a device, you can use a square to set the teeth.
- When the cutter has reached the desired position, work can begin. It is carried out by shifting the edge of the sharpening disk along the edge of the tooth.
- The turning angle value can be changed by moving the wheel vertically or tilting the spindle with the cutter.
Conclusion
Sharpening is a fairly complex operation. You should be extremely careful about the process. After all, the further effectiveness of working with wooden blanks. The video in this article will continue to introduce you to the nuances of sharpening.