They are equipped with special attachments that directly perform the function of adjusting the cutting elements. The equipment is equipped with sharpeners, which are traditional circular or bowl-shaped discs. Most of these attachments are abrasives made from volcanic substances and other rocky mixtures. But a special place in this family is occupied by the diamond wheel for sharpening tools, which is distinguished by its fine-grained functional surface. It will not be possible to process a rough blade using such equipment, but a diamond blade has no equal when it comes to servicing hard-alloy materials, brazing on drills and circular saws.
General information about sharpening discs
The features of diamond sharpening elements are determined by the nature of their purpose. Craftsmen use this abrasive when working with cutting components of other tools. Only high-strength equipment can cope with chain saws, metal cutting heads and steel cutters. Moreover, for safety reasons, technologists also provide a safety margin for consumables. And the diamond grinding wheel meets high requirements, providing not only strength, but also wear resistance. By the way, some models of such elements are even used in granite processing, which confirms the high productivity of the material.
Even if you do not plan to work with solid-state workpieces, disks are used for reasons of economy due to their high working life. True, alternative use does not always pay off, since the diamond wheel for sharpening tools has a small grain. Theoretically, servicing axes, knives and other devices with relatively modest blade hardness is possible, but the work process will require much more time.
Varieties
The main classification involves dividing diamond elements by shape. As already mentioned, the most common are cup-shaped and flat disc sharpeners, which are used specifically for solid-state cutting and saw parts. There is also a borderline variety, represented by circles in the form of a plate. We can say that this is a universal diamond wheel that is suitable for a wide range of sharpening operations. If you plan targeted processing with certain parameters, then you should choose an abrasive not only by shape, but also by technical characteristics.
Main Features
There are two main parameters by which experienced craftsmen choose grinding wheels - the degree of grain size and the standard size. In labeling, digital symbols are used to indicate these indicators. As for the dimensional parameters, they are represented by width, thickness and fit, that is, the diameter of the hole inside the disk. For example, the standard width is 150 mm, thickness is 10 mm, and fit is 30 mm. The grain size of a diamond wheel is represented by a double figure - for example, 125/100 microns. The higher this value, the coarser the sharpening will be. For ordinary tools in the form of knives and other blades of household devices, coarse grain size is sufficient, but for accurate work with hard high-strength alloys, a fine fraction with a dense structure is required.
Dressing diamond wheels
Over time, diamond abrasives lose their former shape, which affects the quality of sharpening. In such cases, it is necessary to edit using one of the methods recommended by experts. Thus, with the help of processing on the disk, steps and rounding can be achieved. Special devices in the form of consumables with a similar principle of influence on the structure are often used. In particular, it is recommended to edit the wheel with suitable characteristics. Typically, this operation is used when diamond grains appear on the surface of the disk. As alternative ways editing can be called electrochemical methods and the application of a lubricant, which contains micropowder with abrasive inclusions.
Reviews of "Caliber" discs
A domestic manufacturer of tools and components produces diamond consumables for various purposes. Users note that at a low price, such products provide high-quality and precise processing. The wheels use raw materials with optimal properties, which allows for accurate sharpening with minimal time. However, in terms of durability, the “Caliber” brand diamond sharpening wheel is far from the best option. Still, the low cost has an impact, due to which the reliability properties of the material were also reduced. However, if the sharpener is selected for one-time but important tasks, then this option is quite suitable. It can also be preferred when servicing household tools that do not require special loads when sharpening.
Diamond grinding wheel is a type of diamond consumable tool. Used in manual and automatic (including angle) grinders for finishing, sharpening, honing and grinding. It is used for processing difficult-to-cut and hard-alloy materials, ceramic surfaces, glass, precious, semi-precious and semi-precious stones. It has an optimal balance of strength and fragility, is characterized by increased efficiency, a large working reserve and self-sharpening.
Scope of application of diamond grinding tools
Thanks to the capabilities of diamond tools, the areas of its use are very wide. The labor intensity of processing hard alloys is reduced several times compared to working with other abrasive materials. Tools sharpened with diamonds work more efficiently and do not require processing for longer. For single-edged parts with a cutting part made of carbide material, such sharpening increases wear resistance by one and a half times, and for multi-edged tools this figure is even higher.
The surface treated with a diamond grinding wheel does not crack, chips or other defects do not form on it. This makes it possible to process glass and ceramic products: car windows, mirrors and much more.
This tool is indispensable when grinding glass for optical instruments, at enterprises producing porcelain, crystal and glassware, and when grinding screens. Diamond grinding is widely used in medicine for sharpening microtome knives, scalpels and injection needles, for dental treatment and prosthetics in dentistry.
In addition, diamond grinding wheels are also used for dressing wheels made from other materials.
However, in order to beneficial properties diamond wheels could be used to the fullest, and the result of the work met expectations, the correct choice of product among many varieties is required.
Design of diamond grinding wheels
The circles represent a body on which a layer of diamonds with different structures is applied. In addition to the diamond elements, the spraying includes a filler and a binder.
All products have various characteristics and differ in:
- the type and shape of the circle;
- case size;
- degree of grain size;
- type of ligament;
- diamond concentrations;
- imbalance class;
- accuracy class;
In addition, they are characterized by strength, hardness, and wear resistance.
Frame
For the manufacture of diamond wheel bodies, steel grades St3, 30, 25 and 20, aluminum alloys grades D16 and AK6 or polymers are used.
For grinding wheels shaped like AGC or A1PP, shanks made of U8 or U7 steel are required.
Diamond concentration
The concentration of the diamond-bearing layer, which is expressed as a percentage, is the number of grains in 1 cubic millimeter of powder used in the abrasive layer. This characteristic affects the efficiency and economy of the tool. The concentration depends on the grit - the higher the grit and the harder the material being processed, the greater the percentage of diamond concentration required for the job.
Diamond grinding wheels are available in 150, 100, 75, 50 and 25 percent concentrations. 100% is taken to be 4.39 carats (1 carat equals 0.2 g) contained in 1 cm3, which corresponds to 0.878 mg/mm³.
This indicator determines the productivity, cutting ability, service life and price of the tool. Optimal performance depends on the area and shape of the material being processed, the type of tool used, bond quality, diamond grit size, and processing conditions.
The choice of circle concentration is based on the following requirements:
- a high concentration is necessary if the contact surface between the workpiece and the grinding wheel is small (for example, during cylindrical grinding), this guarantees a long service life of the tool and increases its wear resistance;
- low concentration is selected for treating large area contact surfaces.
Grain
Grit is the size of a diamond grain or crystal intergrowth (this indicator is determined by thickness, width and height, but usually only width is taken into account). The degree of grain size determines the cleanliness of the surface after processing, work productivity, the amount of material removed per single pass of the wheel, tool wear and other indicators.
The grain size is indicated in accordance with GOST 3647-80 and is indicated in microns by a fraction in which the numerator in microns indicates the size of the upper sieve, and the denominator - the lower one. According to international standards FEPA (and GOST R52381-2005), the characteristic is indicated by the letter F with the corresponding number - the higher it is, the smaller size grains
The grain size is selected depending on the required surface roughness after processing, the type of material, the amount of allowance removed when passing the tool, etc.
The smaller the grain size used, the cleaner the treated surface is. But fine grain size is not always preferable - it gives high cleanliness, but at the same time leads to clogging of the tool and burning of the surface being processed. Using a fine-grained wheel also reduces productivity.
The grain size differs by fraction as follows:
- fine 100/80;
- average 125/100;
- large 160/125;
- larger 200/160.
Wheels with a lower index are used for final finishing of blades, knives, cutters and other products, for final grinding. The middle link allows you to achieve the necessary sharpness of the cutting parts, and coarse grains are used to level and remove part of the surface being processed.
It is advisable to use low-grain wheels to reduce surface roughness, and larger grains when it is necessary to increase productivity and with large allowances. The less viscous and harder the material, the higher the grain size index can be.
Bundles for diamond grinding wheels
Diamond grinding wheels are produced with three types of bonds: metal, designated by the letter M (the base is compositions of tin, zinc, copper, aluminum), ceramic, designated by the letter K (with a base of glass or fireclay and the addition of aluminum) and organic, marked with the letters KB or K (made of carbolite or pulverbakelite). If a filler is used, its role is played by powder made of graphite, copper, alumina, electrocorundum or boron carbide.
Diamond wheels, which use a metal bond in their construction, are characterized by increased heat resistance and strength, retain their geometric shape for a long time and have a long service life, but quickly become greasy. They are used for grinding large volumes of material and pre-processing them. The result is a surface with an eighth to ninth roughness class. Filler is not used in such circles, and the working layer can be fixed to a transition steel ring, which is attached to the body.
Properties of circles with metal bond:
- high hardness;
- high speed and productivity;
- good heat resistance and thermal conductivity;
- high removal productivity.
An organic binder requires the use of filler. It has low hardness, heat resistance and thermal conductivity, but fairly high productivity and processing speed.
Wheels with an organic bond are used for finishing and finishing work, for finishing and finishing sharpening of products made of super-hard materials and hard alloys, for processing medical and measuring instruments. Allows you to obtain a surface of the eleventh and twelfth roughness classes. Unlike wheels with a metal bond, they are less greasy, but they consume diamonds three times more.
Tools with a ceramic bond are characterized by a diamond-nickel coating, which can be applied in one or several layers. The thickness of the bond is two-thirds the size of the diamond grains. Thanks to this, the crystals protrude above the surface of the ligament, but are securely fixed. As a result, the resulting chips are easily removed from the treated area.
Properties of ceramic bonded wheels:
- high cutting ability;
- affordable price;
- any geometry;
- high thermal conductivity.
Used for grinding and cutting germanium, silicon, sital, other semiconductor materials, technical glass and ceramics, and stone processing. It is also used for finishing products made of alloy steels, hard alloys, and in the manufacture of hand tools.
Diamond wheels with a metal bond are used only with water cooling; those with an organic bond can be used both with and without cooling, and the use of alkaline solutions is not allowed.
Hardness of grinding wheels
The hardness of the wheel does not depend on the hardness of the diamond coating. This characteristic means the ability to hold diamond grains in a binder when in contact with the surface being processed. Hardness depends on the technology used in manufacturing, the shape and grain size of the grain, and the quality of the binder.
The self-sharpening ability of a wheel - its ability to restore cutting characteristics after removal or destruction of diamond elements - largely depends on hardness. During operation, the cutting grains split and fall out, and new diamonds begin to act, which prevents the appearance of cracks and burns on the surface being processed. The possibility of self-sharpening decreases with increasing wheel hardness.
The wheels are divided according to hardness into 8 groups, designated according to GOST 19202-80 and R 52587-2006 with the following signs:
- VM1, VM2 F, G - very soft;
- H, I, J, M1, M2, M3 - soft;
- K, L, SM1, SM2 - medium soft;
- M, N, C1, C2 - medium;
- O, P, Q, ST1, ST2, ST3 - medium-hard;
- R, S, T1, T2 – solid;
- T, U, VT - very hard;
- X, Y, Z, V, W, CT - extremely hard.
The choice of hardness is determined by the shape of the part and the required grinding accuracy, the type of processing, the type of tool used, and the properties of the material. Deviations from the optimal characteristics can lead to the appearance of cracks and burns (if the hardness is higher than necessary) or to changes in the geometry of the wheel and its wear (if the hardness is insufficient). It is especially important to follow the rules for selecting a wheel based on hardness when working with products made of hard alloys.
Increased hardness of the wheel will be required if high precision of dimensions and shapes is required. If cutting fluids are used during operation, the hardness may be higher than when dry grinding.
Accuracy class
The accuracy of the geometric shapes and sizes of diamond wheels corresponds to three classes and is designated as: B, A or AA. Less critical operations are carried out with tools of class B; class A refers to higher quality and precision. And high-precision AA wheels are intended for use on multi-circuit and high-precision machines or automatic lines. It corresponds to wheels characterized by uniformity of grain composition, accuracy of geometric parameters and high balance of diamond composition, in the manufacture of which the best grades of materials are used.
Unbalance class
The indicator of mass imbalance of a diamond grinding wheel depends on the uniformity of the abrasive mass, shape accuracy, pressing quality and other parameters acquired during manufacturing. Instruments are produced in four classes of imbalance (indicated by numbers from 1 to 4). This indicator does not relate to the accuracy of the balancing assembly.
Types of work: with and without cooling
Water-cooled grinding is preferable because stronger machining conditions can be applied and the wheel wears less. This also reduces the possibility of burns and other thermal damage to the treated surface. Not water, but 1-5% emulsion is used as a coolant for grinding wheels.
For wheels with a metal binder, it is recommended to use BV lubricant, a 1.5-3% emulsion obtained from the NGL-205 emulsion, or from the “Akvol 10” emulsion. For wheels with an organic binder, use a 3% emulsion from industrial oil, soda ash in the form of a 0.5:1.0% solution, 0.1% wetting agent OP10 or OP7, or an emulsion obtained from borax, sodium nitrate, triethanolamine and trisodium phosphate.
Geometric parameters of circles
Grinding wheels are characterized by dimensions, including: hole and outer diameters, profile height, diamond layer width, etc. The geometric parameters of diamond grinding wheels are designated in accordance with FEPA standards related to tools made from diamond powder. Each piece of equipment has its own letter designation:
- outer diameter of the product - D;
- thickness of the base part of the body - E;
- bore diameter - H;
- diameter of the supporting end - J;
- diameter of the internal groove - K;
- total length of the bar -L;
- shank length - L1;
- length of the diamond-bearing layer - L2;
- radius - R;
- outer corner of the body cone - S;
- total height of the circle - T;
- working part thickness - T1;
- height of the diamond-bearing layer (if T=1 or
- width of the working part of the diamond-bearing layer – U1;
- working angle - V;
- layer width - W;
- thickness of the diamond-bearing layer - X;
- shank diameter - Y;
- concavity of the working layer - P.
This product is certified in accordance with GOST R 50460-92, and described in accordance with GOST 24747-90.
Types of Diamond Grinding Wheels
Diamond grinding wheels are manufactured in accordance with the requirements of GOST 2424, which includes more than 30 types that differ in geometry. The circle can be straight profile, conical, annular, with one- or two-sided undercut, with one-sided hub, disc-shaped, etc. Each of the main types is designated by its identification number:
Straight profile wheels are made in the form of flat discs with a diamond layer at the end. They are used for processing surfaces that require a consistent plane.
Cup wheels are made in the shape of a cup and are used for grinding and final finishing of materials that are poorly amenable to conventional processing: glass, stone, ceramics, hard alloys.
Disc discs (with a small recess) are used when processing steel, cast iron, art glass, for removing paint and varnish coatings, sharpening carbide-tipped saws, etc.
Descriptions of some of the most common grinding wheels:
- 14A1(A1PP) – flat cylindrical, with dimensions D 6-13 H 6-10 S 2-4, designed for grinding conical and cylindrical blind and through holes;
- 1A1(APP) - flat straight profile, with dimensions D 16-500, H 2-50, S 2-5, for grinding, sharpening and finishing of conical and cylindrical surfaces, carbide parts;
- 6A2(APV) - flat with recess, with dimensions D 80-300, H 18-32, S 1.5-5, for flat sharpening, grinding and finishing;
- 9A3(APVD) - with double-sided groove, with dimensions D 100-250, H 6-25, S 1-5 for finishing, sharpening and grinding cutting parts of carbide tools;
- 12V5-45(AChK) - conical cup, with dimensions D 50-250, H 20-52, S 1.5-5, for grinding, finishing and sharpening carbide tools;
- 11V9-70(A1ChK) - conical cup, with dimensions D 50-150, H 20-40, S1.5-5, for grinding corners of parts and working with carbide tools, stone and glass;
- 1EE1(A2PP) - with a conical double-sided profile, with dimensions D 125-250, H 6-20, S 2-4, for processing protrusions of the ends of cylindrical surfaces, grinding grooves and splines;
- 1F6V 1FF6V(A5P) - with a semicircular-convex profile, with dimensions D 50-150, H 2-32, S 2-7, for grinding round-concave grooves and surfaces;
- 1A1R(AOK) - diamond cutting wheel, with dimensions D 50-400, H 0.5-2.5, S2.5-5, for cutting parts and workpieces made of ceramics, hardened steels and hard alloys.
What the geometric shapes of various diamond discs look like can be seen in the table:
The type and size of the wheel are selected based on the type and configuration of the surfaces being ground, as well as the characteristics of the equipment or tool used.
Shape and width of diamond layer
Each circle has a diamond layer of a certain shape and width. A larger width will be required when working “on the aisle”. Grinding using the “plunge” method requires a width commensurate with the width of the surface to which the forces will be applied, otherwise ledges will appear after processing.
The choice of section shape also depends on the tasks set and the shape of the surface being processed. The cross-section of the diamond layer is designated by a specific letter, which can be found in the table:
Grinding wheels also differ in diameter, but the choice of diameter depends both on the tool used, and on the workpiece and the desired result. Also, when working with diamond grinding tools, it is necessary to take into account the number of spindle revolutions on specific equipment.
Marking of diamond grinding wheels
Diamond wheel 12A2-45 (AChK) 150x20x5x32 AC4 160/125 B2-01 100%
With the correct selection of the wheel and compliance with the requirements for a specific type of work, such a tool will significantly increase the speed and productivity of work, save money, and the tool itself will remain operational for a long time.
Processing hard materials such as asphalt, concrete, stone and others requires the use of specialized equipment. And most often the choice is made on a diamond cutting wheel. Moreover, such a tool has superiority over an abrasive one. Among its advantages, the ability to maintain cutting depth, diameter and rotation speed should be highlighted. This feature allows diamond blades to demonstrate higher productivity in situations where a large volume of work is planned.
Making diamond sharpening wheels
The production technology of such a tool requires the use particles of artificial materials, which are processed on special pressing equipment in forms containing, in addition to the main raw materials, a binder. Cutting hard materials can be done using different grades of diamond segments, with the specific choice determined by the size of the diamond particles that were used in their production, as well as the type of binder and the quality and percentage of artificial diamonds.
The finished segments must be fixed to a metal body. This is done using two methods:
- laser welding;
- silver soldering.
The first method is used for tools intended for dry cutting, and the second for wet cutting. Considering that silver melts at a temperature approximately 700 degrees, a similar fastening method is used in the manufacture of high-quality diamond wheels. At this stage, a high-quality diamond disc is created, which is still devoid of cutting ability.
Preparing a diamond wheel for sharpening to perform the tasks for which it was created requires grinding down its segments. To do this, a ceramic sharpener is used, and the operation itself is performed until pieces of diamonds begin to be visible. It is at this moment that diamond cutting wheels turn into a cutting tool. Moreover, on their body there must be an arrow applied by the manufacturer, which shows the correct direction of rotation. This must be remembered when the time comes to install the disk on the shaft of the cutting equipment.
Choosing the Right Diamond Wheel
Choosing a specific tool such as a diamond cutting wheel for sharpening requires taking into account various parameters, among which the following are important:
Even before making a decision in favor of a particular diamond wheel option, you should take into account other important points.
- First of all, you need to pay attention to the capabilities and technical characteristics of the selected diamond wheel.
- When a diamond wheel that meets the requirements is purchased, you need to approach its installation on the shaft of the cutting machine with the same thoroughness.
- Particular care should be taken to ensure that the machine shaft rotates in the same direction as the disc. A hint here will be the arrow on the body, which is pre-applied by the manufacturer.
What else should you pay attention to?
Certain types of similar instruments may not have arrows on the body. If you happen to have just such a diamond sharpening wheel in your hands, then in order to avoid mistakes, it is advisable to read the documentation before installing it. Please note that the diamond cutting wheel must rotate at the same speed as the cutting tool. It should be borne in mind that different brands of diamond blades will differ from each other and in their rotation speed limits. Information about this characteristic can be obtained from the documentation supplied with the cutting tool.
If the operation or installation of a diamond cutting wheel is carried out in violation of the manufacturer's recommendations, then in addition to ineffective processing, risk of damage to incisors. For this reason, even before choosing a particular diamond cutting wheel, you should get acquainted with technical characteristics the machine on which it is planned to be installed.
If you take into account all the nuances at the stage of choosing a diamond wheel, then it will not be difficult for you to select components for it that are ideal for the cutting machine and the material being processed. By acting in this way, you can easily create the optimal cut, and also ensure the safety of operation and high efficiency of the tool.
Options for dressing diamond sharpening wheels
The method of processing products made from high-strength materials using diamond wheels is superior to most others in its effectiveness. However, as you use this tool, it surfaces gradually wear out, which negatively affects the cutting ability of diamond grains.
The cutting characteristics of diamond wheels can be restored using various methods. Moreover, each of them has its own characteristics. The editing procedure involves performing several stages.
Electrolytic straightening
First, you need to electrolytically dress the sharpening wheel. It consists of filling the gap formed by a circle of electrodes with electrolyte. The binder must be oxidized. This provides creating an insulating layer. Thanks to it, the circle will demonstrate lower electrical conductivity and it will be possible to control the consumption of the number of grains. The presence of an insulating layer allows polishing of the surface being treated. But over time, this layer will also be subject to destructive processes. At the first sign of this, the editing cycle is repeated.
Electrochemical straightening
The method of electrochemical dressing of sharpening wheels is in many ways similar to the electrolytic method. Its peculiarity is that there is no need to create an insulating layer. The oxide removal effect ensures the supply of electrolyte. Using this dressing method allows you to create conditions for the continuous removal of abrasive grains. Moreover grain projection size can reach about 110% of the average diameter.
A conventional grinding machine is used as equipment for permanent electrochemical straightening. The operation itself boils down to placing a copper electrode on the grinding wheel. In this case, electrolyte will flow into the gap formed by the electrode and the circle.
In order not to make a mistake when choosing a diamond wheel, you need to make a decision taking into account the size of the internal hole, the diameter of which should be the same as that of the cutting tool. To obtain a high-quality result, it is important to eliminate the occurrence of gaps between the internal hole and the disk shaft.
Conclusion
The use of diamond wheels for sharpening can significantly simplify the work of cutting products made from particularly durable materials. However, it must be remembered that this cutting tool has its own characteristics in terms of its choice. A decision in favor of one option or another should be made from the perspective of the characteristics that the cutting equipment on which it will be installed must meet.
No less important point The choice also includes taking into account the characteristics of the material for which the diamond wheel will be used. At the same time, in order for such a cutting tool to cope with its task for as long as possible, it is necessary not only to follow the rules for its use, but also to know how to correctly restore its cutting ability. All this will allow you to turn it into a reliable assistant when cutting a variety of products with minimal investment of time and money.
Of all the technological procedures performed on metal parts, turning is considered the most popular. In view of this, sharpening metal turning tools is of great importance. It needs to be done correctly. The procedure for sharpening turning cutters depends on the material from which the tool is made, the purpose of the cutter (shaped, through, for cutting threads, for boring).
How does cutting force depend on the sharpening angle?
The cutting force depends on the sharpening angles, especially the front angle. The larger this angle, the lower the cutting force and the easier it is to separate metal chips. However, this does not mean that the rake angle can be increased indefinitely. If the increase is excessive, the reliability of the metal cutter decreases. Its edge is subject to severe wear and chipping. In view of this, when selecting the value of the rake angle, they try not only to reduce the cutting force, but also to obtain a strong edge, a wear-resistant metal-cutting tool.
Sometimes turning cutters with a negative rake angle (from -5 to -10 degrees) are used. Typically, such tools are used when turning hard or hardened metals.
Features of sharpening
There are some features that need to be taken into account when sharpening cutters for lathe with your own hands. The back of the tool is processed in 3 steps:
- First, the rear part is machined at an angle that is equal to the rear angle of the holder. It is usually greater than the clearance angle (about 5 degrees).
- In the second step, the rear part of the cutting blade is processed. It is sharpened at an angle that exceeds the rear cutting angle by 2 degrees.
- Now the desired angle is formed through finishing. The procedure is performed on a narrow chamfer that is adjacent to the working edge.
The front part of the lathe tool is also sharpened in a few steps. First, sharpening is carried out at an angle that is equal to the angle of the cutting blade. The cutting angle formed at the front of the tool is created by finishing sharpening or finishing.
Sharpening the cutter is made easier if you use special pads installed between the supporting surface and the machine table. In order to accurately and efficiently sharpen a tool, you can change the design of the table and add the ability to adjust it in height and rotation angle. After such a change, there will be no need to use overlays.
To sharpen the cutter, the working edge must be located in line with the middle of the abrasive wheel. It is worth taking into account in which direction the sharpener rotates. This will minimize the chance of the cutting insert coming off the tool holder. When rotating the sharpener, the plate should be pressed against the holder, and not torn away from it.
Of course, after sharpening the cutter, you need to check the correct execution. The easiest way to do this is with a special template. You can make it or buy it in the store. If you make the template yourself, use sheet steel.
The great hardness of such a stencil, which it will acquire after hardening, will allow it to be used for a long time. When making a template, you need to cut holes on it that correspond to the running sharpening angles. Only after creating the holes is the stencil hardened. It is worth considering that the correct sharpening of the cutting tool depends on how accurately such a template is made.
Copper chips and filler elements are used to perform finishing. To polish tools made of hard alloys, a special paste is used, boron carbide, which is moistened with kerosene. For tools made of other metals, whetstones with a low level of abrasiveness are used. They are moistened with automobile oil or kerosene.
Types of sharpening
Large enterprises engaged in metal processing necessarily have the specialists and equipment necessary for sharpening tools. Owners of small workshops carry out sharpening themselves.
Sharpening of cutters can be done using one of the following methods:
- Abrasive (on a grinding wheel).
- Mechanical-chemical (processing is carried out with special means).
- Using special devices.
Abrasive sharpening is performed on a sharpening, turning device or on a grinding block. It is difficult to sharpen the cutter by hand, maintaining the required angles. Additional complexity is created by heating the metal, leading to loss of properties. In view of this, the quality of sharpening directly depends on the skills of the worker.
Carbide cutters are sharpened on green carborundum. Tools made from different types of steel are processed using grinding wheels made of medium-hard corundum. Initial processing is carried out with sandstones with abrasive 36-46, final processing - 60-80. Before installing the circle on the machine tool, you need to make sure that it is intact. During processing, it can break, injure the turner, and change the angles of the turning tool.
The mechanical-chemical method makes it possible to sharpen the cutter effectively and quickly, preventing the formation of chips and cracks. This method Used for sharpening large carbide tools. They are treated with vitriol solution. As a result of a chemical reaction, the finest protective film, washed off by abrasive particles present in the solution. The procedure is performed in a machine device, which is equipped with a reservoir with a movable grinder. The fixed tool moves back and forth. In addition, the cutter is pressed against the abrasive (150 g per sq. cm).
Sharpening of diamond cutters is carried out on special equipment using electrocorundum/silicon wheels.
The following is a list of sharpening angles for all common materials. The first fraction indicates the relief angle during roughing, the second - the relief angle during finishing. The third fraction shows the size of the front angle. The numerator indicates the angles for cutters that sharpen and bore parts, and the denominator indicates the angles for tools that plane workpieces.
- Steel (hardness less than eight hundred Megapascals) – 8/6, 12/8, 15/12.
- Steel (hardness more than eight hundred Megapascals) – 8/6, 12/8, 10/10.
- Steel (hardness more than a thousand Megapascals) – 8/6, 12/10, 10/8.
- Gray cast iron (Brinnel hardness less than two hundred and twenty) – 6/6, 10/10, 12/8.
- Gray cast iron (Brinnell hardness more than two hundred and twenty) – 6/6, 10/10, 8/5.
- Malleable cast iron – 8/8, 10/10, 8/8.
The main plan angle should be 30 - 45 degrees. The width of the chamfer depends on the cross-section of the cutting rods.
What abrasive wheels are used for sharpening turning tools?
Sharpening of the tool through the holder and at an angle of 5 degrees is carried out with a circle of electrocorundum, having a grain size of forty - fifty, hardness CM1/2. The peripheral speed of the circle is 25 m/s.
Preparatory sharpening is carried out with products made of black silicon carbide, having a grain size of twenty-five to forty, hardness M3-SM1. The final sharpening of the cutting tool is carried out with wheels made of green silicon carbide, having a grain size of sixteen - twenty-five, hardness M3-CM1.
The parameters of grinding wheels for steel and carbide cutters are specified in the table of sharpening modes. There you can also see the circumferential torsion speeds.
Currently, final sharpening is recommended to be done using a diamond wheel. This is especially true for inserts made of hard alloys. The peripheral speed of the wheel during preparatory/final sharpening should not exceed twelve to fifteen meters per second.
Conducting fine-tuning
After sharpening the tools, they are polished with boron carbide on a cast iron disk rotating at a speed of 1-2 m/s. The disk should rotate in the direction from the tool support to the working edge.
When finishing is carried out, the blades and surfaces of the tool are sequentially ground in. In addition, irregularities are removed and the incisors are brought to a shine.
Why carry out fine-tuning? The fact is that during turning, the tool wears out and becomes dull due to friction of the plate against the chips and the workpiece. The smoother the plate, the weaker the friction, the slower the wear of the tool.
Finishing is carried out with abrasive pastes consisting of boron carbide. Wet the finishing disc with kerosene. Apply paste on it (in a zigzag pattern), bring the tool to the disk. When using kerosene, you can use GOI paste. If you are using a modern paste, it is not necessary to wet the disc with kerosene.
The tool table should be positioned so that the cutting blades are slightly lower or in line with the middle of the disk. The disc should rotate towards the cutting plate.
When the tool is pressed and finishing is performed, the paste particles are crushed. When they pass through the edges, no chips or abrasions appear on the cutter. The paste grains ensure the elimination of irregularities from the incisal surface.
In order to study the finishing procedure in more detail, you can watch the training video. Remember that high-quality finishing will ensure long-term operation of the cutter without re-sharpening.
Grinding wheels are characterized by geometric shape (type), type of abrasive material, its grain size, bond type, hardness, etc. And when choosing a grinding wheel, such characteristics as the degree of hardness or structure may be more significant than the type of abrasive.
The complete markings for grinding wheels contain:
- circle type;
- its dimensions;
- type of abrasive material;
- grit number;
- degree of hardness;
- structure (the relationship between the abrasive, bond and pores in the body of the tool);
- type of ligament;
- maximum speed;
- accuracy class;
- imbalance class.
The marking of wheels, made in accordance with various editions of GOSTs, has some differences regarding the designations of grain size, hardness, grade of abrasive and binder. Manufacturers label their wheels differently, using old or new designations and excluding certain characteristics. Below are examples of deciphering the designations of grinding wheels.
3 - hardness: K - medium-soft;
4 - structure: 6 - medium;
6 - imbalance class: 2
1 - abrasive material: 25A - white electrocorundum;
2 - grain size ( old markings): 60 (according to GOST it should be 63) - 800-630 microns;
3 - hardness: K-L - depending on the circumstances, it can be K or L - medium-soft;
4 - ligament: V - ceramic.
1 - abrasive material: 25A - white electrocorundum;
2 - grain size (old marking): 25 - 315-250 microns;
3 - hardness (old marking): SM2 - medium-soft;
4 - structure: 6 - medium;
5 - bond (old marking): K - ceramic;
6 - accuracy class: B
7 - imbalance class: 3
1 - abrasive material: 25A - white electrocorundum;
2 - grain size: F46 - average size 370 microns;
3 - hardness: L - medium-soft;
4 - structure: 6 - medium;
5 - bond: V - ceramic;
6 - peripheral speed: 35 m/s;
7 - accuracy class: B
8 - imbalance class: 3
1 - abrasive material: 14A - normal electrocorundum;
2 - grain size: F36-F30 - extended range including F36 (average size 525 microns) and F30 (average size 625 microns);
3 - hardness: Q-U - depending on the circumstances, it can be medium-hard, hard, very hard;
4 - bond: BF - bakelite with reinforcing elements;
5 - imbalance class: 1
The choice of grinding wheel brand should be made taking into account all its characteristics.
Types of grinding wheels and their sizes
| 1 | 150x16x32 | 25A | F46 | L | 6 | V | 35 | B | 3 |
The following types of grinding wheels are produced (in parentheses the designations according to the old GOST 2424-75 are given):
- 1 (PP) - straight profile;
- 2 (K) - ring;
- 3 (3P) - conical;
- 4 (2P) - double-sided conical;
- 5 (PV) - with one-sided groove;
- 6 (CHTs) - cup cylindrical;
- 7 (LDPE) - with two grooves;
- 9 - with double-sided groove;
- 10 (PVDS) - with double-sided groove and hub;
- 11 (CHK) - conical cup;
- 12 (T) - disc-shaped;
- 13 - disc-shaped;
- 14 (1T) - disc-shaped;
- 20 - with one-sided conical groove;
- 21 - with double-sided conical groove;
- 22 - with a conical recess on one side and a cylindrical recess on the other;
- 23 (PVC) - with conical and cylindrical grooves on one side;
- 24 - with conical and cylindrical recesses on one side and a cylindrical recess on the other;
- 25 - with conical and cylindrical recesses on one side and conical on the other;
- 26 (PVDK) - with conical and cylindrical recesses on both sides;
- 27 - with a recessed center and reinforcing elements;
- 28 - with a recessed center;
- 35 - straight profile, working with the end;
- 36 (PN) - with pressed-in fasteners;
- 37 - ring with pressed fasteners;
- 38 - with one-sided hub;
- 39 - with a double-sided hub.
All types are described in GOST 2424-83.
In addition to the profile shape, circles are characterized by the size DxTxH, where D is the outer diameter, T is the height, H is the diameter of the hole.
Types of diamond and CBN wheels are regulated by GOST 24747-90. The marking of the shape of CBN and diamond wheels consists of 3 or 4 characters that carry information about the cross-sectional shape of the body, the cross-sectional shape of the CBN-containing or diamond-bearing layer, the location of the latter on the wheel, and the design features of the body (if any).
Designation of a grinding wheel with a body shape 6, the shape of a diamond-bearing or CBN-containing layer A, with the location of a diamond-bearing or CBN-containing layer 2, with design features building S.
All types are described in GOST 24747-90.
The type and size of the wheel are selected based on the type and configuration of the surfaces being ground, as well as the characteristics of the equipment or tool used.
The choice of wheel diameter usually depends on the spindle speed on the selected machine and on the ability to provide an optimal peripheral speed. Specific wear will be the least with the largest diameter circle size. Smaller wheels have fewer grains on the working surface, each grain has to remove more material, and therefore they wear out faster. When working with small diameter wheels, uneven wear is often observed.
When choosing a diamond wheel, it is advisable to pay attention to the width of the diamond-bearing layer. When working "on the pass" it should be relatively large. When grinding using the “plunge” method, the width of the diamond coating should be commensurate with the width of the surface being processed. Otherwise, ledges may appear on the surface of the circle.
Abrasives
| 1 | 150x16x32 | 25A | F46 | L | 6 | V | 35 | B | 3 |
The most commonly used abrasive materials for grinding wheels are: electrocorundum, silicon carbide, CBN, diamond.
Electrocorundum Available in the following brands: white - 22A, 23A, 24A, 25A(the higher the number, the higher the quality); normal - 12A, 13A, 14A, 15A, 16A; chromium - 32A, 33A, 34A; titanic - 37A; zirconium - 38A and others.
Silicon carbide. There are two types of silicon carbide available: black - 52C, 53C, 54C, 55С and green - 62C, 63С, 64C, differing from each other in some mechanical properties and color. Green carbide is more fragile than black carbide.
Diamond widely used for the manufacture of diamond grinding wheels used for finishing and sharpening carbide tools, processing parts made of hard alloys, optical glass, ceramics, etc. It is also used for dressing grinding wheels made of other abrasive materials. When heated in air to 800°C, diamond begins to burn.
Elbor(CNB, CBN, borazone, cubonite) is a cubic modification of boron nitride. Having the same hardness as diamond, it is significantly superior to the latter in heat resistance.
Abrasive materials are characterized by hardness, granularity, abrasive ability, strength, heat and wear resistance. High hardness is the main distinctive feature abrasive materials. Below are comparative characteristics of microhardness and heat resistance of the main abrasive materials.
| Materials | Microhardness, kgf/mm 2 |
| Diamond | 8000-10600 |
| Elbor (cubic boron nitride, CBN) | 8000-10000 |
| Boron carbide | 4000-4800 |
| Silicon carbide green | 2840-3300 |
| Silicon carbide black | 2840-3300 |
| Monocorundum | 2100-2600 |
| Electrocorundum white | 2200-2600 |
| Titanium electrocorundum | 2400 |
| Chromium electrocorundum | 2240-2400 |
| Electrocorundum normal | 2000-2600 |
| Corundum | 2000-2600 |
| Quartz | 1000-1100 |
| Titanium carbide | 2850-3200 |
| Tungsten carbide | 1700-3500 |
| Hard alloy T15K6, VK8 | 1200-3000 |
| Mineral ceramics TsM332 | 1200-2900 |
| High-speed steel hardened P18 | 1300-1800 |
| Carbon tool steel sealed U12 | 1030 |
| Carbon steel sealed St.4 | 560 |
The choice of one or another abrasive material is largely determined by the characteristics of the material being processed.
| Abrasive | Application |
| Electrocorundum normal | It has high heat resistance, good adhesion to the binder, mechanical strength of the grains and significant viscosity necessary for performing operations with variable loads. Processing of materials with high tensile strength (steel, ductile iron, iron, brass, bronze). |
| Electrocorundum white | It is more homogeneous in physical and chemical composition, has higher hardness and sharp edges, has better self-sharpenability and provides less roughness of the processed surface compared to normal electrocorundum. Processing of the same materials as normal electrocorundum. Provides less heat generation, higher surface finish and less wear. Grinding of high-speed and alloy tool steels. Processing of thin-walled parts and tools, when the removal of heat generated during grinding is difficult (stamps, gear teeth, threaded tools, thin knives and blades, steel cutters, drills, woodworking knives, etc.); parts (flat, internal and profile grinding) with a large contact area between the wheel and the surface being processed, accompanied by abundant heat generation; for finishing sanding, honing and superfinishing. |
| Silicon carbide | It differs from electrocorundum in its increased hardness, abrasive ability and fragility (the grains look like thin plates, as a result of which their fragility increases during operation; in addition, they are less well held by the bond in the tool). Green silicon carbide differs from black silicon carbide in increased hardness, abrasive ability and fragility. Processing of materials with low tensile strength, high hardness and brittleness (hard alloys, cast iron, granite, porcelain, silicon, glass, ceramics), as well as very viscous materials (heat-resistant steels and alloys, copper, aluminum, rubber). |
| Elbor | It has the highest hardness and abrasive ability after diamond; has high heat resistance and increased fragility; inert to iron Grinding and finishing of hard-to-cut steels and alloys; fine grinding, sharpening and finishing of high-speed steel tools; finishing and final grinding of high-precision workpieces made of heat-resistant, corrosion-resistant and high-alloy structural steels; finishing and final grinding of machine guides and lead screws, the processing of which is difficult with conventional abrasive tools due to large thermal deformations. |
| Diamond | Has high wear resistance and reduced heat resistance; chemically active towards iron; has increased fragility and reduced strength, which promotes self-sharpening; synthetic diamond of each subsequent grade (from AC2 to AC50) differs from the previous one in higher strength and less fragility. Grinding and finishing of brittle and high-hard materials and alloys (hard alloys, cast iron, ceramics, glass, silicon); fine grinding, sharpening and finishing of carbide cutting tools. |
Diamond wheels are capable of processing material of any hardness. However, you need to keep in mind that diamond is very fragile and does not withstand shock loads well. Therefore, it is advisable to use diamond wheels for final processing of carbide tools, when it is necessary to remove a small layer of material and there is no shock load on the grain. In addition, diamond has relatively low heat resistance, so it is advisable to use it with a coolant.
Grain
| 1 | 150x16x32 | 25A | F46 | L | 6 | V | 35 | B | 3 |
Abrasive grain size is a characteristic of grinding wheels that determines the cleanliness of the resulting surface. The grain is either an intergrowth of crystals, or a separate crystal, or its fragments. Like everyone else solids, it is characterized by three dimensions (length, width and thickness), but for simplicity they operate with one - width. Many parameters depend on the grain size - the amount of metal removed in one pass, the cleanliness of the processing, grinding performance, wheel wear, etc.
According to GOST 3647-80, in the designation of the grain size of grinding wheels, the grain size is indicated in units equal to 10 microns (20 = 200 microns), for micropowders - in microns with the addition of the letter M.
In the new GOST R 52381-2005, basically corresponding international standard FEPA, the grain size of grinding powders is designated by the letter F with a number. The higher the number, the finer the grain and vice versa.
Diamond and CBN wheels have their own grain size designations. Their grain size is indicated by a fraction, the value of the numerator of which corresponds to the size of the side of the upper sieve in microns, and the denominator - the value of the lower sieve.
The table below shows the ratios of grinding wheel grit according to old and current standards.
| Designation according to GOST 3647-80 | Designation according to GOST 9206-80 (diamond powders) | Size, microns | FEPA | |
| Designation for abrasive materials excluding flexible materials | Average size, microns | |||
| F 4 | 4890 | |||
| F 5 | 4125 | |||
| F 6 | 3460 | |||
| F 7 | 2900 | |||
| 200 | 2500/2000 | 2500-2000 | F 8 | 2460 |
| F 10 | 2085 | |||
| 160 | 2000/1600 | 2000-1600 | F 12 | 1765 |
| 125 | 1600/1250 | 1600-1250 | F 14 | 1470 |
| 100 | 1250/1000 | 1250-1000 | F 16 | 1230 |
| F 20 | 1040 | |||
| 80 | 1000/800 | 1000-800 | F 22 | 885 |
| 63 | 800/630 | 800-630 | F 24 | 745 |
| 50 | 630/500 | 630-500 | F 30 | 625 |
| F 36 | 525 | |||
| 40 | 500/400 | 500-400 | F 40 | 438 |
| 32 | 400/315 | 400-315 | F 46 | 370 |
| 25 | 315/250 | 315-250 | F 54 | 310 |
| F 60 | 260 | |||
| 20 | 250/200 | 250-200 | F 70 | 218 |
| 16 | 200/160 | 200-160 | F 80 | 185 |
| 12 | 160/125 | 160-125 | F 90 | 154 |
| F 100 | 129 | |||
| 10 | 125/100 | 125-100 | F 120 | 109 |
| 8 | 100/80 | 100-80 | F 150 | 82 |
| 6 | 80/63 | 80-63 | F 180 | 69 |
| 5, M63 | 63/50 | 63-50 | F 220 | 58 |
| F 230 | 53 | |||
| 4, M50 | 50/40 | 50-40 | F 240 | 44,5 |
| M40 | 40/28 | 40-28 | F 280 | 36,5 |
| F 320 | 29,2 | |||
| M28 | 28/20 | 28-20 | F 360 | 22,8 |
| M20 | 20/14 | 20-14 | F 400 | 17,3 |
| M14 | 14/10 | 14-10 | F 500 | 12,8 |
| M7 | 10/7 | 10-7 | F 600 | 9,3 |
| M5 | 7/5 | 7-5 | F 800 | 6,5 |
| M3 | 5/3 | 5-3 | F 1000 | 4,5 |
| 3/2 | 3-2 | F 1200 | 3,0 | |
| 2/1 | 2-1 | F 1500 | 2,0 | |
| F 2000 | 1,2 | |||
| 1/0 | 1 and | |||
| 1/0,5 | 1-0,5 | |||
| 0,5/0,1 | 0,5-0,1 | |||
| 0,5/0 | 0.5 and | |||
| 0,3/0 | 0.3 and | |||
| 0,1/0 | 0.1 and | |||
The choice of wheel grain size should be determined by a number of factors - the type of material being processed, the required surface roughness, the amount of allowance to be removed, etc.
The smaller the grain size, the cleaner the processed surface is. However, this does not mean that finer grain size should be preferred in all cases. It is necessary to choose the grain size that is optimal for a particular processing. Fine grain gives a higher surface cleanliness, but at the same time can lead to burning of the processed material and clogging of the wheel. Using fine grains reduces grinding performance. In general, it is advisable to choose the largest grain size provided that the required cleanliness of the treated surface is ensured.
If it is necessary to reduce surface roughness, the grain size must be reduced. Larger allowances and increased productivity require larger grits.
In general, the harder the material being processed and the lower its viscosity, the higher the wheel grit can be.
| Grit numbers according to GOST 3647-80 | Grit numbers according to GOST R 52381-2005 | Purpose |
| 125; 100; 80 | F14; F16; F20; F22 | Dressing of grinding wheels; manual roughing operations, cleaning of blanks, forgings, welds, casting and rolling. |
| 63; 50 | F24; F30; F36 | Preliminary round external, internal, centerless and flat grinding with surface roughness of 5-7 cleanliness classes; finishing of metals and non-metallic materials. |
| 40; 32 | F40; F46 | Preliminary and final grinding of parts with surface roughness of 7-9 classes of cleanliness; sharpening cutting tools. |
| 25; 20; 16 | F54; F60; F70; F80 | Finish grinding of parts, sharpening of cutting tools, preliminary diamond grinding, grinding of shaped surfaces. |
| 12; 10 | F90; F100; F120 | Diamond finishing grinding, sharpening of cutting tools, finishing grinding of parts. |
| 8; 6; 5; 4 | F150; F180; F220; F230; F240 | Finishing of cutting tools, thread grinding with fine pitch threads, finishing grinding of parts made of hard alloys, metals, glass and other non-metallic materials, fine honing. |
| M40-M5 | F280; F320; F360; F400; F500; F600; F800 | Final finishing of parts with an accuracy of 3-5 microns or less, roughness of 10-14 cleanliness classes, superfinishing, final honing. |
Hardness of grinding wheels
| 1 | 150x16x32 | 25A | F46 | L | 6 | V | 35 | B | 3 |
The hardness of the grinding wheel should not be confused with the hardness of the abrasive material. These are different concepts. The hardness of a grinding wheel characterizes the ability of the bond to hold abrasive grains from being torn out under the influence of the material being processed. It depends on many factors - the quality of the bond, the type and shape of the abrasive, and the wheel manufacturing technology.
The hardness of a wheel is closely related to self-sharpening - the ability of an abrasive wheel to restore its cutting ability by destroying or removing dull grains. During operation, the wheels intensively self-sharpen due to the splitting of the cutting grains and their partial chipping out of the bond. This ensures that new grains enter the work, thereby preventing the appearance of burns and cracks in the material being processed. The lower the hardness of the wheel, the higher the self-sharpening ability. Based on hardness, circles are divided into 8 groups.
| Name | Designation according to GOST 19202-80 | Designation according to GOST R 52587-2006 |
| Very soft | VM1, VM2 | F, G |
| Soft | M1, M2, M3 | H, I, J |
| Medium soft | SM1, SM2 | K, L |
| Average | C1, C2 | M, N |
| Medium-hard | ST1, ST2, ST3 | O, P, Q |
| Solid | T1, T2 | R, S |
| Very hard | VT | T, U |
| Extremely hard | Thu | V, W, X, Y, Z |
The choice of grinding wheel hardness depends on the type of grinding, the accuracy and shape of the parts being ground, the physical and mechanical properties of the material being processed, the type of tool and equipment. In practice, in most cases, medium-hard wheels are used that have a combination of relatively high performance and sufficient durability.
A slight deviation of the wheel characteristics from the optimal one leads either to burns and cracks of the sharpened surface, when the hardness of the wheel is higher than required, or to intense wear of the wheel and distortion of the geometric shape of the sharpened tool, when the hardness of the wheel is insufficient. Wheels for sharpening tools with inserts made of hard alloys should be selected especially accurately in terms of hardness.
Here are some recommendations that may be useful when choosing grinding wheels based on hardness. When sharpening tools with carbide cutters, the wheel must have high self-sharpening ability. Therefore, when sharpening them, wheels of low degrees of hardness are used - H, I, J (soft), less often K. The more tungsten or titanium carbides in the hard alloy, the softer the grinding wheel should be.
When it is required to maintain high precision of shape and size, preference is given to those types of grinding wheels that have increased hardness.
When using cutting fluids, grinding uses harder wheels than when grinding without cooling.
Wheels on a bakelite bond should have a hardness 1-2 levels higher than wheels on a ceramic bond.
To prevent burns and cracks, softer circles should be used.
Structure
| 1 | 150x16x32 | 25A | F46 | L | 6 | V | 35 | B | 3 |
The structure of a tool is usually understood as the percentage of the volume of abrasive material per unit volume of the tool. The more abrasive grain per unit volume of the wheel, the denser the structure of the tool. The structure of the abrasive tool affects the amount of free space between the grains.
When sharpening cutting tools, it is advisable to use wheels with more free space between the grains, as this makes it easier to remove chips from the cutting zone, reduces the possibility of burns and cracks, and facilitates cooling of the tool being sharpened. For sharpening cutting tools, wheels on a ceramic bond of 7-8th structure are used, and on a bakelite bond - 4-5th structure.
Bunch
| 1 | 150x16x32 | 25A | F46 | L | 6 | V | 35 | B | 3 |
In the manufacture of grinding wheels, abrasive grains are bonded to the base and to each other using a bond. The most widely used binders are ceramic, bakelite and vulcanite.
Ceramic bond It is made from inorganic substances - clay, quartz, feldspar and a number of others by grinding them and mixing them in certain proportions. The marking of ceramic bonded grinding wheels contains the letter ( V). Old designation - ( TO)
The ceramic bond gives the abrasive tool rigidity, heat resistance, shape stability, but at the same time increased fragility, as a result of which it is undesirable to use wheels with a ceramic bond under shock loads, for example, during rough grinding.
Bakelite bond mainly consists of an artificial resin - bakelite. Marking of circles with bakelite has a Latin letter ( B). Old designation - ( B). Compared to ceramic, bakelite binder has greater elasticity and elasticity, heats the metal being processed less, but has lower chemical and temperature resistance, and worse edge resistance.
The bakelite bond can be with reinforcing elements ( B.F., old designation - BU), with graphite filler ( B4, old designation - B4).
Vulcanite bond is a vulcanized synthetic rubber. The abrasive wheel is marked with the letter ( R). Old designation - ( IN).
In most cases, abrasive wheels on ceramic or bakelite bonds are used. Both have their own characteristics, which determine their choice for a particular job.
The advantages of a ceramic binder include strong fixation of grain in the binder, high heat and wear resistance, good preservation of the working edge profile, and chemical resistance. The disadvantages are increased fragility, reduced bending strength, high heat generation in the cutting zone, and, consequently, a tendency to burn the material being processed.
The advantages of the bakelite bond are elasticity, good self-sharpening of the wheel due to the reduced strength of grain fixation in the bond, and reduced heat generation. Disadvantages: more intense wear compared to ceramic bond, reduced edge resistance, low resistance to coolants containing alkalis, low heat resistance (bakelite begins to become brittle and burn out at temperatures above 200°C).
Accuracy class
| 1 | 150x16x32 | 25A | F46 | L | 6 | V | 35 | B | 3 |
The accuracy of the dimensions and geometric shape of abrasive tools is determined by three classes AA, A And B. For less critical abrasive processing operations, a class tool is used B. A class instrument is more accurate and of higher quality A. High-precision tools are used to work in automatic lines, on high-precision and multi-circular machines AA. It is characterized by higher accuracy of geometric parameters, uniformity of grain composition, balance of abrasive mass, and is made from the best varieties grinding materials.
Unbalance class
| 1 | 150x16x32 | 25A | F46 | L | 6 | V | 35 | B | 3 |
The imbalance class of a grinding wheel characterizes the imbalance of the wheel mass, which depends on the accuracy of the geometric shape, the uniformity of mixing of the abrasive mass, the quality of pressing and heat treatment of the tool during its manufacturing process. Four classes of permissible imbalance of the mass of circles have been established ( 1 , 2 , 3 , 4 ). Unbalance classes have nothing to do with the accuracy of balancing the wheels and flanges before installing them on the grinding machine.
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