Abrasive grinding is one of the main types of rough grinding, which is performed to reduce surface roughness, dressing, and eliminate the periodic relief that occurs on the part after machining on machine tools. The laboriousness of the final readiness of the product depends on the correct choice of the grinding wheel, and its ability to better withstand the frictional loads that arise.
Types and technological application of grinding wheels
Abrasive grinding by rotation is carried out using:
- circles;
- heads;
- cutters (cones);
- segments.
The quality after grinding depends on the grade of the grinding wheel. There are three of them: A, B and AA. Class B grinding wheels have the least accuracy, and AA wheels have the highest accuracy (they are usually equipped with precision grinding machines). The accuracy of the grinding wheel is determined by its geometry, the composition of the abrasive material on the wheel, as well as the grain size.
In the practice of grinding or dressing on machine tools and manual machines, one-time fastening of the composition to the base is often used. In fact, this is sanding paper with a velcro backing. Such "circles" with Velcro are used mainly in everyday life, for manual machines, moreover, with a slight removal of metal, in particular, when editing.
On the contrary, when removing a significant amount of metal, home craftsmen often use cutters - nozzles for a conventional electric drill that look like a cutter. The cone, rotating at high speed, performs rough grinding of surfaces after drilling or milling work. Rollers are compact and have a small working surface diameter. Cone cutters, however, cannot provide much torque.
Standard notation
Marking is determined by GOST 2424, and includes the following varieties:
- for operations of rough (rough) grinding of metal, internal or external, dressing mainly by the periphery - circles with a straight profile (pp);
- for processing threads, and other periodic profiles on metal - double-sided conical (2p), or dish-shaped (t);
- for sharpening and dressing friction cut-off saws - conical one-sided (3p);
- for centerless grinding of metal - circles with one- or two-sided undercuts (pv);
- for face grinding with a flat surface - ring (k).
The above nomenclature refers to solid circles that perform the operation with their entire working perimeter (editing, rough grinding). When using typesetting grinding wheels, special segments are used, which are installed in the corresponding seats of the wheel body on a machine or machine. They are produced in accordance with the technical requirements of GOST 2464. Type-setting segments can process hard-to-reach surfaces (for example, rail cavities, narrow grooves in metal or stone). Grinding segments are more economical when dressing, and allow easier ongoing maintenance machine.
Applied abrasive compositions
The initial requirements according to GOST are resistance to frictional wear (moreover, under the combined action of high pressures and sliding speeds), low thermal conductivity and increased surface hardness.
Depending on the intensity of application, GOST 28818 allows the use of the following materials:
- Electrocorundum on a bauxite component, which is based on high-percentage aluminum oxide Al 2 O 3 with the addition of calcium oxide. This chemical compound is characterized by increased hardness, which is also preserved when high temperatures arising in the zone of grinding or dressing. Marking circles of electrocorundum - from 12A ... 15A for normal, up to 22A ... 25A - for white. With an increase in the index, the strength of the wheel increases due to an increase in the hardness of the base substance.
- Electrocorundum on a carbide basis. More often it contains carbides of chromium, titanium, zirconium and silicon. Marking starts from 38A (for zirconium) and ends with 95A (for chromium and titanium). The carbides of these metals have an increased resistance to shear shear stresses, and therefore are suitable for removing surface layers of parts that have undergone heat treatment, or for straightening them. The presence of silicon carbide (marking 52C ... 65C) increases resistance to temperature changes.
- Spherocorundum is a material that is obtained by blowing molten aluminum oxide, resulting in the final spherical shape of grains (in electrocorundum, grains are predominantly flat). The marking of this composition is ES, and it has an extremely high hardness. This circumstance makes it possible to use spherocorundum for grinding materials with increased hardness, including even hard alloys.
- Monocorundum (marking - 43A ... 45A), where the grinding grain, unlike other types, has a single-crystal structure. This increases the durability of the abrasive composition, but at the same time increases its cost, since the technology for growing single crystals is very complex. A more accessible variety is aggregated monocorundum, in which poly- and single-crystal sections are combined in a certain way.
The degree of granularity is set according to GOST 3647, and is also noted in the marking.
The bonding of the abrasive component with the base is carried out using rings, flanges, glass mesh discs, etc.
The role of ligaments
In addition to the cutting agent itself, the manner in which it forms the abrasive mass is also important. GOST allows the use of Bakelite or ceramics as binders. The bakelite version is good for its higher density, so the wheel is characterized by increased mass, suitable for metal work, but with a limited circumferential speed of rotation (especially if manual grinder machine). The use of ceramics makes the grinding wheel lighter, and the permissible speed of its rotation on the machine increases accordingly. However, the abrasive resistance as well as the hardness of the ceramic wheel are reduced.
The ligament also determines the method of attachment to the body base. For example, film bonding is suitable for vitrified bonds, but not for Bakelite bonds.
A special type of ligament is a fiber. Such a base is used in the so-called "cold" grinding of metal on a machine or machine, when the surface of stainless steel or the weld zone is cleaned. At the same time, the material being processed practically does not heat up, since the depth of the grinding zone is insignificant (the process is actually closer to polishing). Marking is carried out in accordance with GOST R 51967.
Other types of ligaments are also used to a limited extent - from various epoxy compositions, magnesite, porcelain.
How to choose the right size and type of tool
The choice depends on the processing conditions, the main equipment used (machine or manual machine), as well as on the material being ground.
The manufacturer also matters. Among consumers, there is a slang designation of the instrument - "Luga" and "Volga" circles. In the first case, the manufacturer is OAO Luga Abrasive Plant, and in the second case, OAO Volzhsky Abrasive Plant.
The Luga plant produces products in accordance with GOST based on silicon carbide, and imported components are used as feedstock. The products of the Luga plant on ceramic and bakelite bonds made of white electrocorundum are also popular. Circles of the Luzhsky plant with a steel bottom - a novelty of the manufacturer - can significantly increase the tool life during centerless grinding.
The products of the Luga plant are used for both round and flat grinding. The Luga circle is suitable for both a machine tool and a manual machine.
The Volzhsky plant manufactures circles in accordance with GOST from silicon carbide (wastes from metallurgical and refractory production are used). In the products of the Volzhsky plant, semi-finished products are used with strict compliance with the classification of European manufacturers of abrasives FERA. The goods of the Volzhsky plant were among the hundreds of the best domestic goods.
When choosing a domestic manufacturer - Volga or Luga - they are guided by the following practical recommendations:
- the goods of the Luga plant show the best resistance when grinding on machines or machines of products made of cast iron, aluminum, copper alloys, most non-metals;
- the products of the Volzhsky plant are more popular in situations where, in addition to the actual grinding, editing is also necessary. The products of the Volzhsky plant are also used for steel work.
Buying the optimal circle according to GOST of one standard size (Volga or Luga) is an unrealistic task in most situations. Using a manual machine, you need a circle that can withstand the maximum number of revolutions, and when working on stationary car you will need a tool that is able to withstand higher pressures.
If you have 1A1 250x40x34 24A F30 L 5 V 35 B 3 written on your grinding wheel, then I think after reading you can easily decipher
Grinding wheel shapes
250x40x34 24A F30 L 5 V 35 B 3
For cylindrical grinding, the wheel must have an A1A or 1V1 profile. In Soviet circles, there was the designation PP or 1.
Grinding wheel geometry
1A1 250x40x34 24A F30 L 5 V 35 B 3
250 is the diameter of the grinding wheel
40 is the thickness of the grinding wheel
34-hole diameter in the grinding wheel
Abrasive and grain of the grinding wheel
1A1 250x40x34 24A F30 L 5 V 35 B 3
All grinding wheels consist of two main components - these are the grinding grains that actually cut and the bond that fastens and holds them during the cutting process. The ratio of grain to free space andthe bond in the wheel characterizes the structure of the grinding wheel.
The ideal abrasive should remain sharp with a minimum number of sharp edges, and when dull, the abrasive of the grinding wheel should chip off, renewing fresh cutting edges.
Aluminum oxide - this abrasive is used for grinding carbon steel and alloys, high speed steel, annealed ductile iron, wrought iron products, bronze. It happens white - 22A,
23A,
24A,
25A(the higher the number, the higher the quality) and normal -12A,
13A,
14A,
15A,
16A; chromium - 32A,
33A,
34A; titanic - 37A. Foreign manufacturers of grinding circles have the following designation
BUT brown alumina, WA white alumina
WAB white alumina + blue bond
WA white alumina + special bond
WAR white alumina + red bond
WAY white alumina + yellow bond
PA pink aluminum oxide
RA ruby alumina
DA white and brown aluminum oxide
SA semi-brittle alumina
HA monocrystalline aluminum oxide
FROM black silicon carbide
Zirconia aluminum oxide - This abrasive is used for grinding in rough grinding, designated 38A or Z.
Silicon carbide - this abrasive is used for grinding gray and chilled cast iron, soft bronze, brass and aluminum and non-metallic materials, denoted64С-62С or GC.
Ceramic alumina - this abrasive is used for precision grinding of difficult-to-cut steels and alloys, designated AS1-5, the higher the number, the greater the content of alumina, for example 1 is 10%.
Grain size is the number of linear holes per inch of the sieve used for the final sieving of the grain. How larger size grains, the coarser the grain. How smaller size grains, the larger the wheel is suitable for fine grinding.
Grinding wheel grain size
1A1 250x40x34 24A F 30 L 5 V 35 B 3
Large from 8
before 24 (F 180-80)
Average of 30
before 60 (F 56-24)
petty off 80
before 180 (F 24-12)
very small from 220
before 600 (F 10-4)
Grinding wheel hardness
1A1 250x40x34 24A F30 L 5 V 35 B 3
Bond hardness is measured in terms of the hardness of the grinding wheel. For example, the bond has a hard degree if the bonding of the abrasive grains of the grinding wheel is very strong, and it holds the grains well from tearing out under the action of cutting forces during grinding. Conversely, the bond has a soft degree if the application of a small force is sufficient to pull the grains out of the circle.
Hard wheels are used for work for processing with a small contact area. Soft grinding wheels are used for fast and coarse material removal and for hard materials.
| Name | Designation according to GOST 19202-80 | Designation according to GOST R 52587-2006 |
| Quite soft | VM1, VM2 | F, G |
| Soft | M1, M2, M3 | H, I, J |
| Medium soft | CM1, CM2 | K,L |
| Middle | C1, C2 | M, N |
| Medium hard | ST1, ST2, ST3 | O, P, Q |
| Solid | T1, T2 | R, S |
| Quite hard | WT | T, U |
| Extremely hard | Thu | V, W, X, Y, Z |
Grinding wheel structure
1A1 250x40x34 24A F30 L 5 V 35 B 3
The structure of the 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.
With knitting grinding wheel
1A1 250x40x34 24A F30 L 5 V 35 B 3
The bond in the grinding wheel is designed to hold the abrasive grains together and should facilitate the self-sharpening process of the grains.
The choice of the type of bond of the grinding wheel affects the speed of processing, its appearance and accuracy.
ceramic bond It is made from inorganic substances - clay, quartz, feldspar and a number of others by grinding and mixing them in certain proportions. Vitrified bonded grinding wheels are marked with the letter ( V). Old designation - ( TO)
The ceramic bond gives the abrasive tool rigidity, heat resistance, shape stability, but at the same time increased brittleness, as a result of which it is undesirable to use wheels with a ceramic bond under shock loading, for example, in rough grinding.
bakelite bond mainly consists of artificial resin - Bakelite. The marking of circles with bakelite has a Latin letter in the designation ( B). Old designation - ( B). Compared to ceramic, wheels with a bakelite bond have greater elasticity and elasticity, heat the metal being processed less, but have lower chemical and temperature resistance.
Bakelite bond can be with reinforcing elements ( bf, old designation - BOO), with graphite filler ( B4, old designation - B4).
Vulcanite bond is a vulcanized synthetic rubber. The marking of the abrasive wheel has the letter ( R). Old designation - ( IN)
Grinding wheel accuracy class
1A1 250x40x34 24A F30 L 5 V 35 B 3
The accuracy of the dimensions and geometric shape of abrasive tools is determined by three classes AA, BUT And B. For less critical abrasive operations, a tool of the class B. More accurate and high quality is a class tool BUT. To work in automatic lines, on high-precision and multi-circular machines, high-precision tools are used AA. It is distinguished by a higher accuracy of geometric parameters, uniformity of the grain composition, balance of the abrasive mass, and is made of the best varieties grinding materials.
Grit size of the grinding wheel
Grit size of the grinding wheel affects the quality of the resulting surface when grinding the surface, for example, the finer the grain of the wheel, the higher the surface roughness class.
The grit size of the grinding wheel is chosen depending on the type of grinding operation: rough, semi-finishing or finishing, as well as the necessary requirements for cleanliness and accuracy of processing. In the rough grinding operation, wheels made from coarser grains are used than in the finishing one. High requirements to the cleanliness of the resulting surface and the accuracy of processing in most cases are ensured by the use of circles with a finer grain. Hardened parts and hard alloys are ground with finer-grained wheels than non-hardened ones. For grinding parts made of materials prone to greater clogging (brass, copper, and many others), use wheels with a larger grain. With large contact surfaces of the grinding wheel with the workpiece (for example, grinding with the end of the wheel), wheels with a coarser grain are used.
Grit size of the grinding wheel characterizes the size of the grains of the wheel in diameter. The surface cleanliness and processing accuracy depend on the size of the grains; granularity is determined by sifting abrasive grains through a series of sieves with a different number of holes.
The grit size of the grinding wheels is selected depending on the type of work performed and the requirements for the roughness of the surface to be treated.
The grit size of the grinding wheel affects the quality of the surface to be ground; the finer the grain of the circle, the cleaner the surface is obtained. The grit size of a grinding wheel is characterized by the size of its abrasive grains and is indicated by the corresponding number.
Grinding wheel imbalance class
1A1 250x40x34 24A F30 L 5 V 35 B 3
The unbalance class of the grinding wheel characterizes the unbalance of the mass of the wheel, which depends on the accuracy of the geometric shape, the uniformity of the mixing of the abrasive mass, the quality of pressing and heat treatment of the tool during its manufacture. Four classes of permissible unbalance of the mass of circles are established ( 1
, 2
, 3
, 4
). Unbalance classes are not related to the accuracy of balancing wheels assembled with flanges before installing them on a cylindrical grinding machine.
Under the grinding of surfaces of parts from various materials, they understand the main initial operation for removing scuffs, notches remaining after the operation of various metalworking machines, sharpening knives. For high-quality processing, it is necessary to choose a grinding wheel with characteristics that correspond to the type and size of the part undergoing this procedure.
General information
Abrasive grinding tool actually represents a kind of cutting metalworking equipment. The cut is carried out with the help of a large number of hard particles. There are a lot of types of grinding wheels, some of which are known only to those who have encountered them. For example, in the aircraft industry and the space industry, a special tool is used. However, it does the same job as other similar devices.
For different coatings there is a kind of grinding wheel. With their help, steel, cast iron products, non-ferrous alloys and forged accessories can be processed. Special equipment is available for working with glass, ceramics and bricks. The most common abrasive tools currently in use are:
- Circles.
- heads.
- Mills, or cutters.
- segments.
- Bar accessories.
After processing with such equipment, the remaining roughnesses are determined by classes A, B and AA. The best quality grinding, denoted by the letters AA, is achieved on high-precision machines.
Classification of emery tools
The gradation of circles by type occurs in two ways. The first of them is determined by two official documents: the old Soviet GOST 2424-83 "Grinding wheels: specifications" and the modern "Grinding wheel: GOST R 52781-007". However, what is contained in them will be little understood by most unprepared users.
For this, there is a second, popular specification of a grinding tool:
Qualitative characteristics of products
There are a lot of different parameters by which such products are classified. There are even more types of markings for abrasive wheels due to the fact that there are many different combinations of these properties. The main parameters of abrasive wheels for grinding machines are considered:
For use, a circle is selected with the appropriate indicators, which are indicated in the marking on the product itself.
Grit of fixture
This is the most significant feature. Its value determines how smoothly the sample will be polished. In addition, the amount of wear, productivity, thickness of the layer to be removed in one cycle also depend to a greater extent on this indicator. The smaller the tool grain, the higher the finish. However, the speed of work with such granularity is reduced. In addition, such devices often cause burn parts.
The old standard defines the size of the grain in microns, in a new way it is denoted by the letter F with a number. The higher the digital component, the less graininess. All these indicators are summarized in the table grit grinding wheels.
Materials for manufacturing
Like all characteristics, the requirements for the material from which the grinding wheels are made correspond to GOST. Minimum conditions - wear resistance, low heat transfer, hard surface. Based on these conditions, abrasive tool is made from the following material:
Application of bonding materials
For a tight arrangement and protection from destruction in grinding wheels, special substances are used. Their quality, variety, even distribution affect all the characteristics of abrasive tools. And also the presence of these materials shows the ability to self-sharpen the crumbled areas of the grinding stone. If the binding component does not correspond to the surface to be treated, the tool loses its main property, wear increases, the grain that has not yet been processed is chipped, burning and clogging appear.
Organic and inorganic binders can be used as binding elements. The former are ceramic and silicate materials, the latter are bakelite and volcanic.
The following materials are involved in the ceramic bond: refractory clay, quartz and spar. They are strong, durable, with a stable cutting edge. The tool on this basis can be cooled with special emulsions. Circles of small thickness are destroyed by lateral impact. Designated K0, K1, K3 and so on. At their production carbide - silicon or electrocorundum grain is used. They grind well in all ways, except for cutting and using in narrow grooves.
Bakelite resin and lacquer powder make up a bunch of B, B1, B2 and others. Such circles are thin, strong and elastic. However, when heated, such a connection floats and the grains fall out. To increase heat resistance, cryolite is added to such a bundle. Wetting when grinding with Bakelite bonded wheels is prohibited.
A mixture of artificial rubber with sulfur gives a volcanic bond. Its elasticity is higher than that of bakelite, but the heat resistance is worse. Elasticity allows the production of thin cutting discs with the designation B, B1, B2.
High-strength metal bond is produced on copper, tin, aluminum and other bases. It is used in the manufacture of diamond and elbor grinding wheels.
Hardness indicators
This property describes the ability of a disk to retain grains under external influence. The lower it is, the faster the destruction of the abrasive. The decoding of the hardness of grinding wheels for machine tools looks like this:
This parameter is determined by the depth of the sandblasting or the Rockwell hardness tester. The most commonly used grinding discs are of medium hardness. They are extremely efficient and durable. Soft tools are suitable for internal and flat grinding. When turning threads, small diameter parts, hard circles are needed. As a general rule, the harder the workpiece, the softer the abrasive tool needed.
Grinding wheel precision
When determining this parameter, the existing cracks, shells and the location of surfaces relative to each other are evaluated. The most precise accessories are characterized by the minimum inconsistencies and are installed on high-precision high-precision machines and high-speed equipment. Marked with the letters AA.
The next most accurate abrasive devices are slightly inferior to the highest quality ones. They are designated by the letter, A. Samples of the lowest category of accuracy are one and a half to two times inferior to accessories, A - class. They are marked with the letter B and are used for not the most accurate grinding operations.
Abrasive tool size
This parameter is observed in accordance with GOST 2424-75. Disk dimensions are strictly observed. All grinding equipment is designed to these standards:
- The outer diameter of the circle is designated D, its dimensions are from 3 to 1100 millimeters.
- The inner diameter, in sizes from 1 to 305 mm, is marked with the letter d.
- The height, or thickness, is h with a value of 0.18-250 millimeters.
Tool instability
This characteristic shows the deviations of the grinding wheel for the grindstone from the rest position - in other words, the beating during rotation. In the marking stamp, it is indicated next to the accuracy class and has designations from 1 to 4. The unit indicates the high quality of the equipment.
Surface structure
Its density is determined by the ratio of the number of grains to the disk volume. Accordingly, the larger their number and the smaller the coefficient, the denser the circle. A dense surface is marked 1-4, marking 5-7 guarantees an average. 8-10 is an open structure, and a factor of 11 and 12 means a porous type of emery.
Safety at work
Operations with equipment that performs grinding and cutting work have several hazards. This is the rotation of the device, the possibility of destroying the disk on the go, the threat of touching the rotating equipment. To maintain health, you need to fulfill the following requirements:
Modern grinding tools and machines greatly facilitate the work of a person. BUT right choice tooling will allow you to perform stripping operations with a maximum level of cleanliness.
Grinding wheels are designed to remove small amounts of material from the surface of a workpiece. In this way, irregularities are removed, sharpening of various tools is performed. To choose one or another model, you should familiarize yourself with the classification and types of grinding wheels.
Purpose of grinding wheels
The scope of these processing tools is wide. They differ not only appearance, but also by the method of manufacture. With the help of grinding wheels, it is possible to remove a small volume from the surface of the workpiece, thereby improving the technical and performance characteristics, appearance.
A variety of materials and tools fall under the definition of a grinding wheel. Therefore, it is advisable to consider the most common of them. For domestic purposes, most often used end, which are installed on a drill. In addition, one should take into account the marking of the product, the possibility of using it on special grinding machines, size.
Ways to use grinding wheels, depending on the marking and composition:
- grinding surfaces of various parts and workpieces. The degree of processing depends on the grain size, total area contact and rotation speed;
- tool sharpening. To perform these actions, you must use special diamond sharpeners.
During the selection, the material of manufacture of the workpiece is taken into account. For processing wooden, steel and polymer surfaces with a drill, they are used different types grinding wheels.
Some types of work sometimes require grinding wheels of non-standard configurations and sizes. In other models, they differ not only in grain size, but also in shape. Most often, such models are used to complete factory machines.
Types of grinding wheels
To determine the types of grinding wheels, you must familiarize yourself with GOST 2424-83. It indicates the destination area, the material of manufacture and the requirements for the technical parameters of this type of tool. But the operating conditions are decisive.
Currently, the following types of end and flat wheels with the appropriate marking and designation can be used to perform grinding work:
- grinding for metal. Are applied to processing of welded connections. After installation on the drill, the end part is used to process workpieces and parts;
- diamond. Designed for final grinding of the surface of the workpiece. It should be remembered that they belong to the category of grinding. Characterized by a special composition;
- fiber. Made from multilayer vulcanized paper. Processing takes place both with the end and planar part of the material. Designed for installation on a drill;
- petal. They consist of many petals mounted on a mounting ring. They are characterized by high adaptability to any types of workpiece surfaces. With the help of flap discs, rust is effectively removed;
- self-locking. Characterized by a high grain size. One part has an adhesive base for installation on a drill. Designed for fine processing of wooden or metal surfaces.
Before choosing, you should consider the grit size of the grinding discs. The same applies to sharpening models. The larger the grain size, the more intensively the material will be removed from the surface of the part during grinding.
The diameter is also taken into account. For household machines, models with a diameter of 50 to 300 mm are used. Specially shaped wheels can be set during fine processing.
Material for the manufacture of grinding wheels
The degree of processing of the grinding wheel largely depends on its structure. Given the different types of operations, manufacturers offer several types for a drill, differing in marking, material of manufacture and type of processing - face or plane.
The main requirement for the material of manufacture is abrasive properties. At the same time, they must have sufficient mechanical strength and not collapse under the influence of aggressive media. Latest Quality especially important when using coolants. This is not typical for petal models.
The structure and composition of the material of manufacture can be determined by marking and designation. The scope of the grinding wheel is also indicated there:
- electrocorundum. They are divided into white (22A, 23A, 24A, 25A), normal (12A, 13A, 14A, 15A, 16A), chromium (32A, 33A, 34A), titanium (37A) and zirconium (38A). The higher the number, the higher the quality of workmanship;
- silicon carbide. It is produced in green (62C, 63C, 64C) and black (52C, 53C, 54C, 55C) colors. The first has a more fragile structure. Used as sharpeners;
- diamond. The main area of application is sharpening and grinding of carbide tools. With the help of diamond wheels, it is possible to finish other types of grinding surfaces;
- elbor. Its properties are similar to diamond, but it is more heat resistant. For domestic needs, it is practically not used as a sharpener, as it has a high cost.
The next property of the end circles for a drill is their graininess. It determines the purity of the resulting surface. In the old GOST, the main characteristic was the grain size. This characteristic can vary from 20 to 200 microns. Grain size according to GOST 52381-2005 is designated Fx (where x is a grain size characteristic). The higher this value, the smaller the particle size.
In each case, the material of manufacture of the grinding wheel for face machining with a drill is determined on an individual basis. This is influenced by the properties of the workpiece, the required degree of its grinding.
Marking of basic grinding wheels
In order to choose optimal models grinding wheel, you need to know the symbols on its surface. Thus, you can find out not only the method of its manufacture, but also the graininess, exact dimensions and configuration: petal, regular or special sharpening.
First of all, it is necessary to determine the material of manufacture and the possibility of using it as a sharpener on the machine. Data can be taken from the list described above. Then the graininess of the circle for the drill is recognized. In some cases, the icon indicates that face machining is not possible. Most often this applies to corundum discs for metal.
The next property is the hardness of the grinding wheel. Classification depending on its composition:
- F, G. Belong to the category of very soft;
- H, I, J. Soft, designed for finishing parts;
- K, L. Thus, products with medium softness are marked;
- M, N. Medium, the most common type;
- O, P, Q. Medium hard;
- R, S. Solid;
- T, U. Very hard, used as a grindstone;
- V, W, X, Y, Z. Extremely hard.
Manufacturers rarely indicate the structure and composition of the disc on the label. First of all, it refers to the type of connection. This term indicates which composition was used to create a homogeneous mass. Currently, ceramic, bakelite and volcanic binders can be used as a binder.
During operation, the geometry of the oval circle or the size of the petal base may be disturbed. In particular, this applies to the end processing of parts using a drill or machine. In this case, it is necessary to make an edit according to the marking. To do this, it is recommended to use carbide tools or diamond blades.
The video shows the main types of grinding wheels:
- products for stone processing.
A grinding disc is one of the types of abrasive tools, along with heads, segments, bars, abrasive belts and sanding sheets, which is actively used for processing various kinds of surfaces. The abrasives used for the manufacture of grinding wheels are strong, 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 machine the surface of other materials; in terms of purpose, they can be compared with the teeth of an ordinary saw, but located not at the edges, but along the perimeter of the disk. Grinding wheels are used on 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, drywall.
A non-professional classification, familiar to many, divides grinding wheels into the following types:
- Discs with the so-called "Velcro" - a special cloth that is applied to sanding paper.
- Flap wheels - have a surface of abrasive material, located in the form of a fan-shaped overlay of layers. They are very durable, provide a smooth surface after processing, and are most often used for grinding pipes or wooden surfaces.
- Fiber discs consisting of vulcanized paper with a multilayer structure. They are attached to the machine using a support plate with the required cross section. Fiber discs are used for cleaning metal, wood, steel products.
- Diamond wheels used for final processing. As a rule, they have little strength.
Grinding wheel marking
Qualitative characteristics of abrasive wheels are regulated by GOSTs, standards and specifications. Each of the grinding wheels has its own marking according to the following characteristics:
- Sanding material
- Disc size
- Grain size
- Disk type
- Degree of hardness
- Binder
- Instability class
- Structure
- Segments
- Optimum rotation speed
To decipher these points, it is necessary to consider the marking of grinding wheels in more detail.
Grinding abrasive type
The most common marking of abrasive wheels according to the type of material is the following:
- Electrocorundum
Marking 12A, 13A, 14A, 15A, 16A: normal electrocorundum (material with high heat resistance, good adhesion to the binder, mechanically strong grains). Applicable to wrought iron, cast iron, steel, bronze, chrome steel.
22A, 23A, 24A, 25A: white electrocorundum (more homogeneous than type 14A, harder, with sharp edges, has the property of self-sharpening, provides a more uniform surface of the material being processed). It is used for sharpening and grinding tool steel, thin-walled parts and tools, as well as finishing and finishing.
Abrasive wheel marking
32A, 33A, 34A: chromium electrocorundum.
37A: titanium electrocorundum.
38A: zirconia. The higher the marking, the higher the strength of the discs.
- Silicon carbide
Marking 52-55C: black silicon carbide (it has increased hardness compared to the previous type of abrasive, and brittleness). They are used for polishing cast iron, granite, porcelain, silicon, ceramic, glass surfaces, as well as viscous aluminum, copper, rubber materials, heat-resistant steel products.
Marking 62С,63С,64С: green silicon carbide. It differs from black in greater fragility.
- Elbor
Marking CBN, CBN, cubonite, borazone: has the strength of diamond, but greater heat resistance.
- Diamond
Marking of diamond wheels: AC2 (normal strength), AC4 (high strength), AC6 (high strength), AC32 (single crystals), AC50, ARB1, ARK4, APC3. They have the highest wear resistance, strength, low brittleness. The use of diamond wheels finds itself in the processing of brittle and high-hard alloys (cast iron, ceramics, silicon, optical glass), as well as finishing grinding, cutting, sharpening carbide tools.
Grinding wheels, grit (marking)
Such a characteristic as granularity determines the smoothness of the treated surface. The grain size of the grinding disc determines its wear, the thickness of the metal layer removed in one pass, etc. How less value one grain, the smoother and cleaner the surface will be.
The grain size determines the disc markings:
- Grinding grain: the size of the fraction is from No. 200 to No. 16
- Sanding powder: No. 12-4
- Microgrinding powder: M63-M14
- Fine microgrinding powder: M10-M5.
Grain units are given in µm. The marking of diamond grinding wheels, more precisely, their type of grit, is indicated in a different way (through a fraction of the upper and lower values).
Grit marking for grinding wheels Circle size
The sizes of disks are regulated by GOST 2424-75. Marking D is a numerical designation of the outer diameter, d is the inner diameter, h is the height (width). The outer diameter can vary from 3-1100 mm, the inner diameter from 1.0 to 305 mm, and the height from 0.18 mm to 250 mm.
Instability (unbalance) class
There is a designation of four classes of imbalance (from 1 to 4), i.e. admissible values of disc deviation from static balance. The unbalance class indicates the ratio of the mass of the 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 to work on high-precision equipment, class B is more versatile, 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 disk volume. The more abrasive per unit volume of the grinding wheel, the denser its structure. If the tool is sharpened, a disc with a less dense structure is better exposed to surface cleaning from material particles, creates less risk for 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
The conditional indicators of disks until 2008 were regulated in accordance with GOST 2424-83. Since 2008, a new edition of GOST 2424 came into effect. In 2009, the marking of abrasive wheels began in a new way: modern standards for the symbol for the hardness of a machining tool came into force (GOST 52587-2006 to replace the old GOST 18118, 19202, 21323), grain size ( GOST 52381-2005 instead of GOST 3647-80), bundles (new GOST 52588-2006).
Also, modern indicators of the 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 brackets):
- - section of a circle of a straight profile (PP). Suitable for universal use
5 - straight profile with one-sided undercut (PV). Used for circular grinding.
7 - with two grooves (PVD)
10 - with a hub and a double-sided undercut
- – ring type (K)
6 - cylindrical cup-shaped (CC). Used for sharpening tools.
36 - with fasteners (PN)
11 - conical cup shape (ChK)
41 – cut-off type disk
4 - with a double-sided conical profile (2P)
- - type with a conical profile (3P)
12.14 - poppet (T, 1T).
Flap grinding wheels are marked with the type, outer diameter, inner diameter, height, grit and sanding series.
Bond type marking
The bond holds the grinding grains to the base and to each other. Typically, three types of bond markings are indicated on the discs: these are vulcanite, ceramic and bakelite.
The first type of ligament is designated as R, or, the obsolete designation - "B". It consists of synthetic rubber subjected to a vulcanization process.
The ceramic bond is marked as V, the former name is "K". It includes the combination of inorganic substances (clay, quartz). Its advantages are wear resistance, thermal and chemical resistance, but at the same time brittleness.
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 index of the grinding wheel indicates the strength of the grains held by the bond on the surface when the abrasive being treated is exposed to the disc.
Disc hardness designations start from very soft (ВМ1, ВМ2) to extremely hard (ЧТ), in the new designation, marking is carried out by letters English alphabet, ranging from F (very soft) to Z (extremely hard).
Most often, discs of medium hardness are used, but the choice of the type of degree depends on the type of work performed, the surface of the material, and the tool itself.
Grain
According to the previous GOST, the marking of the degree of graininess was expressed in measuring the number of grains in a volume of 10 microns, for microgrinding 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 graininess. The larger it is, the smaller the grain and vice versa.
