Diamond grinding wheels. Marking of grinding wheels: explanation Abrasive wheel for metal processing
Diamond grinding wheel is a type of diamond consumable tool. Used in manual and automatic (including angular) grinding machines 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 their 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 features diamond wheels could be used to the fullest, and the result of the work met expectations, required right choice products among many varieties.
Design of diamond grinding wheels
The circles represent a body on which a layer of diamonds with different structures is applied. In addition to diamond elements, spraying includes filler and binder.
All products have various characteristics and differ in:
- the type and shape of the circle;
- case size;
- degree of grain;
- 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, having the shape of AGC or A1PP, shanks made of U8 or U7 steels 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, the quality of the bond, the grain size of the diamond grain and the processing conditions.
The choice of circle concentration is based on the following requirements:
- a high concentration is necessary if the contact surface of the workpiece and the grinding wheel is small (for example, during cylindrical grinding), this guarantees long time operation 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) characteristic is designated 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 required 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 insignificant hardness, heat resistance and thermal conductivity, but is sufficient high performance and processing speed.
Wheels with an organic bond are used for finishing and finishing work, for finishing and finishing sharpening of products made of superhard 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 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 grinding dry.
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 wheels AA 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 they are used the best varieties materials.
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;
- diameter of the mounting hole - 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 indicated 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 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, to remove 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 recess, with dimensions D 100-250, H 6-25, S 1-5 for finishing, sharpening and grinding the 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 dimensions 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.
Diamond layer shape and width
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 tool 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%
At correct selection range 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.
Before it becomes a finished product, a metal blank is very often processed using abrasive grinding wheels. This is done in order to ensure a highly smooth surface.
Scope of application of abrasive grinding wheels
Polishing any elements not only makes them more attractive in appearance, but is also often a necessity from a technical point of view. In everyday life, elements of interior items are often subjected to this process, and in industrial production - parts of various machines, machine tools and other mechanisms.
For moving parts, polishing is extremely important: individual parts must be well-fitted and smooth to minimize friction. It is worth noting that the most different materials– metal, stone, plastic, wood. Abrasive wheels are also actively used in a variety of sharpening machines.
Abrasive wheels can vary in shape as they are used for different purposes. In addition to smoothing the surface metal parts often need cleaning to remove rust. It is almost impossible to implement this task without special circles. Using removable attachments for a grinding machine, you can make recesses and grooves of varying complexity in various materials, including non-ferrous metals, ornamental stone, concrete walls, soft alloys.
Abrasive wheels are very popular among jewelers, for whom polishing items made of precious metals is the main part of their work. Stone craftsmen who work with ornamental minerals and semi-precious stones also use this tool.
There are special varieties grinding attachments installed on a drill. They are actively used during repair or finishing works(for example, for cleaning the surface of walls before laying tiles or applying plaster compositions). Some sanding wheels are great for removing old paint from plumbing fixtures, cleaning pipes from corrosion, and other similar jobs.
Types of Grinding Wheels
To properly process a part, it is necessary to determine the type of grinding. This will allow you to choose the right abrasive attachments. The main selection criteria are the material of the workpiece and the nature of the impact on its surface.
Thus, grinding wheels with a straight or annular profile are widely used in everyday life and on small metals, sharpening operations performed by them end surface. These wheels are relevant when working with glass, porcelain, and stone (here you can also use flat attachments with one- or two-sided grooves, which are also convenient when carrying out grinding work).
The most common are conical circles, which can be either double-sided or regular. They can be used for all of the above work for surface treatment of parts with a plane. They can also be used to make holes in almost any material.
For processing many parts, the best options include a grinding cup wheel and a wheel with disc attachments (most often they have a solid metal nozzles and diamond sputtering). The cup wheel resembles a straight profile tool with a conical undercut. The main difference is that the end is located at a right angle to the side plane.
The range of abrasive wheels by type of abrasive is quite wide. In addition to the previously mentioned diamond coating, electrocorundum is widely used. Solid nozzles are made using electrocorundum. Most often they do not have a base and a pressed core.
Circles made of silicon carbide are also in demand. The latter are divided into two types: black and green (the nozzles have the corresponding color). Green is more fragile.
CBN is a high-strength abrasive. This material is based on cubic boron nitride. In terms of performance properties, it is not inferior to diamond, while CBN differs more high level heat resistance.
Vulcanite and bakelite grinding wheels
Diamond coating is quite expensive, so it is applied in a very thin layer to a metal base. Abrasive wheels with less strength are formed in a different way. Often, for this purpose, a binder ceramic composition is used, where the main components are materials of inorganic origin (quartz, clay, etc.). Highly ground, these binders are added to the selected abrasive when forming the wheel, providing finished product increased rigidity, but also corresponding fragility.
Bakelite nozzles are in great demand on the market. They owe their name to the main filler – bakelite (artificial resin). This binding component gives the circle elasticity and a kind of elasticity, but at the same time wear resistance is reduced as a result of weaker fixation of the grains (compared to a rigid ceramic base).
It is important not to forget that a rigid base of high hardness can lead to overheating of the metal being ground and, accordingly, burnout of the surface of the processed element. Bakelite nozzles do not have this drawback. They are much softer, so they heat the metal very little and are capable of self-sharpening when processing a part.
The grinding wheel with vulcanite binder is even softer. Here the main abrasive element is synthetic heat-treated rubber. In other words, vulcanization is used in the production of such grinding attachments, which is reflected in their name. Vulcanite wheels have a higher cost compared to ceramic abrasives. However, despite the increased elasticity, their wear resistance is beyond praise.
Selecting a grinding wheel
The main requirement for an abrasive attachment concerns its hardness. The hardness of the nozzle must be higher than the hardness of the workpiece. At the same time, it is undesirable for these parameters to differ greatly, otherwise the likelihood of overheating of the treated surface increases. One of the most important criteria when selecting an abrasive is its grain size.
Large fractions of ceramic or rubber wheels are not suitable for working with soft materials. Fine grains are only suitable for polishing. Often fine-grained abrasives are applied to cutting discs and disc-shaped metal nozzles. A fiber disc can provide a glossy surface. If its nozzle is softer than the workpiece, the processing result will be good, but the wear of the tool will also be very severe.
In most cases, to give the final product smooth surface metal workpieces are processed using special grinding wheels. Thanks to polishing, it is possible to achieve the external attractiveness of the element, as well as provide it with the technical characteristics necessary in a particular situation.
This tool finds wide application both when processing elements of interior items, and for fitting, for example, bar and panel parts industrial production. Making moving parts smooth is especially important, since ensuring that their friction is minimized plays a large role in the operation of all equipment.
A fairly wide range of materials can be sanded. These include stone, metal, plastic, and even wood. Removable nozzles allow you to form various grooves and recesses in non-ferrous metals, concrete walls, soft alloys, which are brought to a final finish by cutting heads.
Grinding wheels are often used not only for smoothing metal surfaces, but also to remove rusty deposits from parts, which is almost impossible to do without this equipment. In many cases, craftsmen purchase abrasive wheels for sharpening machines, with the help of which they can quickly make other cutting tools.
These products have gained particular popularity among jewelers, who primarily polish precious metals. The tool is also often used for processing the surfaces of semi-precious stones and ornamental minerals.
On the market you can find special types of grinding attachments that are installed on a drill. They are used during the process repair work, for example, when cleaning walls for subsequent tiling. Certain types of wheels allow, when installed on an electric sharpener, to clean pipes from corrosion and remove old paint from plumbing and so on.
Types of equipment
To carry out the correct processing of parts, it is necessary to decide on the type of grinding. Thanks to this you can choose best option abrasive nozzle.
The main criteria for choosing this equipment include the following components:
- the material from which the workpiece is made;
- the nature of the work exerted on the surface of the product.
Grinding wheels equipped with a ring or straight profile are often used for work on small emery surfaces and machines, in everyday life, as well as for sharpening carried out with the end surface of the tool. The materials used with this equipment are stone, porcelain and glass.
The most popular are conventional and double-sided conical wheels, the operation of which is based on processing the surfaces of the part with a plane. They also allow making cuts in a wide range of materials.
Often, experienced craftsmen have in their arsenal cup wheels and tools with all-metal disk attachments equipped with diamond coating. The cup modification resembles straight profile equipment with a conical groove. It differs only in the rectangular arrangement of the end in relation to the side plane.
If we consider the types of equipment depending on the type of abrasive, we can distinguish a fairly wide range of tools. In addition to the above-mentioned diamond coating, which is usually used for sharpening and finishing carbide elements, electrocorundum is considered quite popular, making it possible to produce one-piece attachments. Corundum wheels are usually made without a pressed core and base.
An abrasive called elbor has particular strength. The basis of this material is cubic boron nitride, which is practically not inferior in its performance characteristics to diamond. Moreover, it has an undeniable advantage, namely: a high level of heat resistance.
The technique of performing diamond spraying on abrasive attachments does not involve the use of any binding elements, since it is applied to the metal in a thin layer. This is what accounts for the significant high cost of such equipment. Abrasive wheels, which have less strength, are made using a ceramic binder composition, which usually includes materials of inorganic origin, such as clay, quartz, etc. They are carefully ground and added to the selected abrasive during the formation of the wheel. Thanks to this, the final product becomes rigid.
There are two main types of nozzles depending on the binder component in the abrasive:
- bakelite;
- volcanic.
The most popular are bakelite attachments, which include an artificial resin that gives the circle the necessary firmness and elasticity. However, the designated component also causes a decrease in wear resistance, which occurs due to insufficient bonding of the grains. This is not observed with wheels on a hard ceramic base. However, it is worth remembering that hard substrates with high hardness can provoke overheating of the metal being ground, and this can lead to burnout of the surface of the workpiece. There is no such drawback in bakelite nozzles. They are quite soft, do not heat the metal very much and self-sharpen during operation.
Wheels with a vulcanite component are even softer. They use heat-treated synthetic rubber as an abrasive element. In the production process of the equipment, the vulcanization method is used, which formed the basis for the name of the product. Such wheels are somewhat more expensive than modifications equipped with ceramic abrasive. But this is not surprising, because in addition to excellent elasticity, they also have increased wear resistance.
Features of choosing a tool
The main selection criterion grinding stone is its hardness. This indicator should not be less than the hardness of the part being processed. Moreover, it is not permissible to allow large differences in such parameters, which is fraught with possible overheating of the surface.
An important criterion when choosing an abrasive can also be called grain size. Usually to establish optimal size grain, it is necessary to familiarize yourself with the requirements for the purity of processing of the final product. Each grinding wheel is equipped with its own marking, the decoding of which allows you to select the correct sanding tool. It is usually represented by the type of abrasive material, degree of unbalance, size and type, structure, degree of hardness, level of precision, grit size, nature of the bond and maximum speed processing.
When working with metal and wood, it is necessary to use sanding wheels of different grain sizes, otherwise the quality of the finish may be poor. If you find nicks or rough marks on the surface of the element being processed, you can confidently say that the choice of the grain size of the equipment was made incorrectly.
For ease of use of the tool, a table of grinding wheel grain size has been created, which allows you to quickly understand the necessary parameters and decide on the choice of attachment.
The most popular types of such tools include grinding wheels with the following designations:
- with grit 120;
- with grit 60;
- with 100 grit.
Depending on the specific type of operation being performed, the specialist selects the required type of equipment. For rough grinding, wheels with large grain fractions are usually used, but for finishing grinding this figure should be significantly lower. In addition, when selecting a tool, the features of the grinding equipment mode and technical properties cutting element.
When working with soft materials, do not use rubber and ceramic wheels with large fractions. Fine-grained nozzles are used only for polishing. Typically, fine-grained abrasives are applied to disc-shaped metal attachments, as well as to cutting discs. To ensure a glossy surface, it is logical to use a fiber wheel. In this case, the processing result will be better if you choose a tool with a softer nozzle than the material of the part being manipulated. However, this is also often accompanied by rapid tool wear.
When working with large surfaces, you should opt for grinding wheels large diameter. This recommendation will allow you to save equipment, because a small element will need to rotate much more often, which will lead to its rapid deterioration.
By approaching the choice of a grinding wheel thoroughly, you can find a tool that will perform as efficiently as possible at the lowest financial cost.
– goods for stone processing.
A grinding disc is one of the types of abrasive tools along with heads, segments, bars, abrasive belts and sandpapers, actively used for processing various kinds surfaces. The abrasives used for the manufacture of grinding wheels are durable, highly hard substances: diamond, corundum, quartz, as well as artificial materials– electrocorundum, synthetic diamonds, silicon and boron carbide and others. The grains of these substances subject the surface of other materials to mechanical processing; in terms of their purpose, they can be compared with the teeth of a conventional saw, but located not along the edges, but along the perimeter of the disk. Grinding wheels are used to process many materials: carbon steel, glass, plastic, bronze, wrought iron and non-ferrous metals. In addition, they are used in tools for cutting brick, stone, ceramic tiles, and drywall.
A non-professional classification, familiar to many, divides grinding wheels into the following types:
- Discs with so-called “Velcro” - a special fabric that is applied to sandpaper.
- Petal wheels - have a surface made of abrasive material arranged in the form of a fan-like overlay of layers. They are very durable, provide a smooth surface after processing, and are most often used for sanding pipes or wooden surfaces.
- Fiber discs consisting of vulcanized paper with a multi-layer structure. They are attached to the machine using a support plate with the required section. Fiber discs are used for cleaning metal, wood, and steel products.
- Diamond wheels used for final processing. As a rule, they have little strength.
Marking of grinding wheels
The qualitative characteristics of abrasive wheels are regulated by GOSTs, standards and technical specifications. Each of the grinding wheels has its own marking according to the following characteristics:
- Sanding material
- Disc size
- Grain size
- Disk type
- Hardness degree
- Binder
- Instability class
- Structure
- Segments
- Optimal rotation speed
To decipher these points, it is necessary to consider the markings of grinding wheels in more detail.
Type of grinding abrasive
The most common markings of abrasive wheels by type of material are as follows:
- Electrocorundum
Marking 12A, 13A, 14A, 15A, 16A: normal electrocorundum (material with high heat resistance, good adhesion to the binder, mechanically strong grains). Suitable for processing wrought iron, cast iron, steel, bronze, chrome steel.
22A, 23A, 24A, 25A: white electrocorundum (more uniform than type 14A, harder, with sharp edges, has the property of self-sharpening, provides a more uniform surface of the processed material). Used for sharpening and grinding tool steel, thin-walled parts and tools, as well as finishing and finishing.
Marking of abrasive wheels
32A, 33A, 34A: chromium electrocorundum.
37A: titanium electrocorundum.
38A: zirconium. The higher the marking, the higher the strength of the discs.
- Silicon carbide
Marking 52-55C: black silicon carbide (has increased hardness compared to the previous type of abrasive, and brittleness). Used for polishing cast iron, granite, porcelain, silicon, ceramic, glass surfaces, as well as viscous aluminum, copper, rubber materials, and heat-resistant steel products.
Marking 62С,63С,64С: green silicon carbide. It differs from black in being more fragile.
- Elbor
Marking CBN, CBN, cubonite, borazone: has the strength of diamond, but greater heat resistance.
- Diamond
Marking of diamond wheels: AC2 (regular strength), AC4 (high strength), AC6 (high strength), AC32 (single crystals), AC50, ARB1, ARK4, APC3. They have the highest wear resistance, strength, and low fragility. Diamond wheels are used in processing brittle and high-hard alloys (cast iron, ceramics, silicon, optical glass), as well as finishing grinding, cutting, and sharpening carbide tools.
Grinding wheels, grit (marking)
A characteristic such as grain size determines the smoothness of the processed surface. The grain size of the grinding disc determines its wearability, the thickness of the metal layer removed in one pass, etc. The smaller the value of one grain, the smoother and cleaner the processed surface will be.
The grain size determines the marking of the discs:
- Grinding: grain size ranges from No. 200 to No. 16
- Sanding powder: №№12-4
- Micro sanding powder: M63-M14
- Fine micro-grinding powder: M10-M5.
The grain size units are given in µm. The marking of diamond grinding wheels, or more precisely, the type of their grain size, is indicated in a different way (through the fraction of the upper and lower values).
Grinding wheel grit markings Circle size
Disc sizes are regulated by GOST 2424-75. Marking D is a numerical designation of the outer diameter, d is internal diameter, h – height (width). Outside diameter can vary in the range of 3-1100 mm, internal - from 1.0 to 305 mm, and height - from 0.18 mm to 250 mm.
Instability class (imbalance)
There is a designation for four classes of imbalance (from 1 to 4), i.e. permissible values of disc deviation from static balance. The imbalance class denotes the mass ratio abrasive disc to the accuracy of its geometric shape. Therefore, often the unbalance and accuracy markings are indicated side by side. Accuracy class A is used for working on high-precision equipment, class B is more universal, AA - discs of ideal shape and geometry made of very high quality abrasive.
Structure
The density of the structure is indicated depending on the ratio of the number of abrasive grains to the volume of the disk. The more abrasive per unit volume of the grinding wheel, the denser its structure. If a tool is sharpened, a disk with a less dense structure is better able to clean the surface from material particles, creates less risk of deformation, and cools faster.
The numerical designation of the structure is as follows:
1,2,3,4 – dense structure;
5,6,7 – medium density;
8,9,10 – open;
11,12 – porous.
Marking of grinding wheels: old and new, difference according to GOST
Until 2008, the conditional indicators of disks were regulated in accordance with GOST 2424-83. Came into effect in 2008 new edition GOST 2424. In 2009, marking of abrasive wheels began in a new way: modern standards for the symbol of hardness of a processing tool (GOST 52587-2006 instead of the old GOST 18118, 19202, 21323), grain size (GOST 52381-2005 instead of GOST 3647-) came into force 80), ligaments ( new GOST 52588-2006).
Also, modern indicators of types of grinding wheels differ from those adopted in the USSR. The existing designation of grinding wheels is as follows (the previously used designation is indicated in parentheses):
- – cross-section of a straight profile circle (PP). Suitable for universal use
5 – straight profile with one-sided groove (PV). Used for cylindrical grinding.
7 – with two grooves (PVD)
10 – with hub and double-sided recess
- – ring type (K)
6 – cylindrical cup-shaped (CC). Used for sharpening tools.
36 – with fasteners (PN)
11 – conical cup-shaped (CC)
41 – cutting disc type
4 – with a double-sided conical profile (2P)
- – type with conical profile (3P)
12.14 – disc-shaped (T,1T).
Flap grinding wheels are marked with the type, outer diameter, inner diameter, height, grit size and series of abrasive paper.
Marking by type of bundle
The bond holds the grinding grains to the base and to each other. Typically, three types of bond markings are indicated on discs: vulcanite, ceramic and bakelite.
The first type of connective is designated as R, or the outdated designation “B”. It consists of synthetic rubber subjected to the vulcanization process.
The ceramic bond is marked as V, the former name was “K”. It includes a compound of inorganic substances (clay, quartz). Its advantages are wear resistance, thermal and chemical stability, but at the same time fragility.
The bakelite bond is marked as B, formerly known as "B4" and "BU". It contains artificial resins. This is an elastic ligament, but otherwise the parameters are lower than those of a ceramic one.
Hardness indicators
The hardness indicator of a grinding wheel indicates the strength of the grains being held by the bond on the surface when the disc is exposed to the abrasive being processed.
Disk hardness designations begin from very soft (VM1, VM2) to extremely hard (CHT), in the new designation the marking is carried out with letters English alphabet, ranging from F (very soft) to Z (extremely hard).
Most often, disks of medium hardness are used, but the choice of type of degree depends on the type of work being performed, the surface of the material, and the tool itself.
Grain
According to the previously valid GOST, the marking of the degree of granularity was expressed in measuring the number of grains in a volume of 10 microns; for micro-grinding powder, these values were expressed by adding the letter “M”. The new standard establishes the designation with the letter "F" with the addition of a number that indicates the degree of grit. The larger it is, the less grain and vice versa.
2017-07-06
Types of abrasive wheels are distinguished by design differences and are regulated by GOST R 52781-2007 “Grinding wheel”. The document defines the following types of products:
- ring;
- disc-shaped;
- conical;
- conical double-sided;
- with grooves on one or two sides;
- with a recessed central part;
- with cylindrical and conical recesses;
- with two grooves.
Image #1:
Products of certain subtypes are used for different procedures: processing, grinding, tool sharpening. Wherein main criterion choice is related to the type of workpiece being ground and the nature of the impact on its surface.
Grinding wheels with straight and annular profiles are used in domestic conditions and on compact machines for processing metal products, sharpening tools, and cutting edges. They are also suitable for working with glass, stone, porcelain, and ceramics.
Photo #1:
The most popular are conical-type circles (double-sided and regular). With their help, planes are processed and recesses of various shapes are made.
Photo #2:
Cup-shaped and disc-shaped wheels with diamond coating are widely used. In addition to diamond abrasive, other materials are actively used for the manufacture of wheels: electrocorundum, silicon carbide, CBN, bakelite. We will tell you more about choosing attachments for cutting tools below.
Application of abrasive wheels
The main area of application of abrasive wheels is cleaning surfaces made of carbon steel, cast iron, plastic, non-ferrous metals, glass, iron. The tool is also used for cutting brick, tile, slate, drywall, and concrete. Products are actively used for cutting grooves and slits of various shapes and depths.
The circles that are installed on the drill deserve special attention. Such nozzles are used during repair and finishing work to clean walls before laying tiles and applying plaster. Removing paint stains, rust and other coatings is another area where abrasives can be used.
How to choose an abrasive wheel
To select an abrasive wheel, pay attention to its markings. The scope of application of the products is of primary importance. There are attachments for industrial installations and hand tools. To work in a domestic environment, you will need the second option. We will consider the remaining points related to the choice separately.
Abrasive grain size
The particle size on the canvas varies in the range of 12-4000 microns. It is indicated on the circle in the form of a special marking. The generally accepted encryption system is FEPA. The grain size indicator in the table is indicated by the index F. The lower the numerical value, the larger the particles in size.
There are three main grit sizes:
- large (F16-24);
- medium (F30-60);
- small (F70-220).
Large abrasive particles allow you to cut metal, concrete and other hard elements with maximum speed. However, a fine-grit bit is required to carefully cut edges and grooves.
Circle diameter
The diameter of the circle must match the size of the cutting tool. There are products with a diameter of 80-500 mm on sale. Household machines are produced for circles with diameters of 115, 125, 150, 180 and 230 mm. How larger size products, the easier it is to saw a thick metal part.
Photo #3:
Photo No. 4:
Type of processed material
The best abrasive wheels are those that are suitable for the material being processed. Information about this will be given by drawings on the surface in the form of stone, concrete, ceramics, metal, etc. There are also universal products that are suitable for working with different coatings.
Rotational speed
Pay attention to the estimated rotation speed of the nozzle. It should be slightly higher than the one on which the grinder works. This parameter is indicated by the color of the strip on the product:
- green - 100 m/s;
- red - 80 m/s;
- yellow - 63 m/s.
Circle Density
The choice of abrasive wheel is influenced by its structure (density). This parameter shows how far apart the grains are from each other. The specific type of backfill is selected according to the density of the material being processed. There are three structure options:
- closed - for metals and aggressive grinding;
- semi-open - for non-ferrous metals, paints, plastics;
- open - for wood processing.
Let's give specific examples. Circle PS18EK with filling open type Suitable for wood processing, rust removal, paint, putty. The PS22K semi-open attachment is designed for sanding metal and hardwood. The dense backfill product PS21FK is suitable for machining stainless steel.
Marking of abrasive wheels
The full markings applied to abrasive wheels contain the following information:
- circle type;
- overall dimensions (height and diameter);
- abrasive material;
- grit class;
- hardness level;
- material structure;
- type of connecting element;
- rotational speed;
- accuracy class.
Circles 125-150 mm are closer to universal ones. They weigh little, yet easily solve a variety of household tasks. Also, when purchasing, check that the diameter of the mounting hole of the circle matches the mount on the grinder. The standard value here is 22 and 32 mm. There are 10 mm holes in circles that are installed on a drill.
Image #2:
Circles are marked according to different editions of GOST standards, so the codes contain differences in hardness, density and other parameters. To understand the markers, review the table below.
Photo No. 5:
- Abrasive material: 25A - white electrocorundum.
- Grit size: 60, that is, 800-630 microns.
- Hardness: K - medium.
- Structure: 6 - medium.
- Connecting element: V - ceramics.
- Unbalance class: 2.
Photo No. 6:
- Abrasive material: 14A - normal electrocorundum.
- Grit size: 36-30, that is, 525-625 microns.
- Hardness: Q-U - medium/hard.
- Connecting element: BF - bakelite with seal.
- Unbalance class: 1.
How to calculate the need for abrasive wheels
It remains to understand how to calculate the need for abrasive wheels during processing individual materials to determine the volume of purchases. There is no absolute calculation criterion, since consumption depends on a number of parameters, including the quality, density and hardness of the wheels, as well as their suitability for the selected material.
The following table will help you with your calculations.
Image #4:
In a simplified form, consumption can be determined in practice. To do this you should:
- treat a certain amount of surface;
- divide the footage by the number of nozzles used.
In everyday life, this calculation is sufficient. If we are talking about controlling production costs, the data is recorded and a document is drawn up on the rate of abrasive consumption, which is signed by the director of the enterprise.
