Grinding wheels - why are they needed and what are they? Abrasive grinding wheels What is a grinding wheel for?

Every person who is going to make repairs or perform certain grinding tasks needs to know what the marking of grinding wheels means. They differ in their characteristics and are used in various cases. In order to effectively perform the work with the tool, you need to know all the nuances of the designations of the grinding wheels.

Classification of abrasive wheels

Discs are classified into the following types:

• with a recess (PV - for round grinding);
• double-sided conical (PVDC);
• straight profile (PP - universal circle);
• with a conical one-sided or two-sided undercut;
• ring (K - suitable for flat grinding);
• dish-shaped (T);
• cup conical or cylindrical;
• with a double-sided conical profile (2P: scope - thread grinding, spline grinding, gear grinding).

Grinding wheel marking

Grinding wheels can vary in geometric shape, type of abrasive material, as well as the type of bond, wheel grit, hardness, etc. When choosing a grinding wheel, hardness and structure can weigh more than the type of abrasive.

According to various editions of GOSTs, the marking of circles has different designation parameters. Almost every manufacturer labels their wheels differently.

So, the full marking of varieties of grinding wheels contains:

• circle type;
• grinding material;
• disk dimensions;
• degree of hardness;
• grain size;
• structure;
• binder;
• maximum rotation speed;
• accuracy class;
• imbalance class.

Abrasive type

The most popular and common materials used in the manufacture of grinding wheels include:

1. Electrocorundum. When buying such a circle, you can see white, titanium, chromium and zirconium options. The main disc used is white electrocorundum, which has a high self-sharpening ability. In working with it, you can achieve a more even and smooth surface.
2. Silicon carbide. There are black and green tones, this circle differs in structure and degree of fragility - it is harder and stronger than the first type described above. Scope - work with firm alloys, porcelain and marble.
3. Elbor. This kind of grinding wheel has the hardest abrasive material and high heat resistance. Elbor can be used for sharpening cutting tools and other parts that can deform from heat, as well as for working with hard metals.
4. Diamond. Another hard type of abrasive wheels. It is used in working with hard materials, glass and ceramic surfaces. Self-sharpening, but cubonite and elbor have greater heat resistance, while not inferior in strength.

Regardless of the type of abrasive material, all wheels are characterized by the parameters of strength, wear resistance and heat resistance, however, when choosing, one should take into account the main parameter - hardness. The hardness characteristic is prescribed in the GOST 2424 standards and is calculated according to special tables.

For example, the type of abrasive wheel 25A F180 K 7 V is white corundum. There are other types of known abrasives:

• normal electrocorundum (13-16A);
• white (23-25A);
• chromium (33 and 34A);
• only one titanium (37A);
• zirconium is also one (38A);
• monocorundum (43-45A);
• black silicon carbide (53 and 54C);
• green silicon carbide (62-64C).

Grit marking for grinding wheels

When marking grinding wheels, manufacturers indicate only its width (MKM or F with a numerical grain size indicator). The grain size not only indicates the wear resistance of the abrasive, but also plays an important role in the grinding of a particular surface.

The grain size of the wheel affects the quality and finish of the surface finish. Consider the material you are working with. To get the cleanest surface, you should buy a wheel with the smallest grit value. However, a person working with such a circle must understand that it is quickly salted, and the material being processed often burns.

According to GOST from 1980, units equal to 10 microns are used to measure the graininess of circles. In the modern version of GOST R 52381-2005, circles are marked with the letter F with a certain number (with an increase in the number, the degree of graininess decreases).

For example, the grit number according to the old GOST (M40-M5) and the new one (F280, F320, F360, F400-F600, F800). For decoding: such a disk is used for final finishing and honing of parts with an accuracy of 3-5 microns or less, as well as for superfinishing. Or size 40, 32 according to the old GOST and F40, F46 according to the new one: wheels with such a grain size are used for preliminary and final grinding of parts with surface roughness of 7-9 cleanliness classes, as well as for sharpening cutting tools.

Abrasive disc size

The marking of abrasive wheels by size is written as follows: DxTxH (where D is the outer diameter, T is the height, H is the diameter of the hole). The D parameter can reach a maximum size of 1100 mm, the H value can be up to 305 mm, and the T parameter varies from 0.18 mm to 250 mm.

Types of elbor and diamond discs are described in more detail in GOST 24747-90. Marking the shape of such grinding wheels consists of three or four characters indicating the shape of the section of the body and layer, its location on the wheel, and also provides information about the design features of the body.

For example, 150x16x32 - the size of the abrasive wheel 25A white electrocorundum.

Memo when choosing abrasive wheels:

• When choosing a wheel diameter, the number of spindle revolutions and the possibility of obtaining optimum speed should be taken into account.
• The larger the diameter, the lower the specific wear of the wheel. There are fewer grains on the working surface of small circles. So, in work they wear out unevenly.
• When choosing a diamond wheel, the width of the diamond layer should be taken into account. If used incorrectly, ledges may appear on the surface of the wheel.

Structure and hardness index

The density of the structure of grinding wheels is indicated by the percentage of the volume of abrasive grains per unit volume of the circle. The more abrasive, the denser the structure of the grinding wheel will be.

When sharpening a tool, a wheel with a less dense structure is more susceptible to cleaning the surface of material particles, creates less risk of deformation and cools faster.

Often, specialists use discs of medium hardness, but it all depends on the type of work performed, the coating being processed and the tool itself.

What are the numbers of structures and volumes of abrasive in the grinding wheel:

• dense structures include units of measurement from 1 to 4;
• the average density includes the numbers 5-8;
• to open - from 9 to 12;
• a highly porous structure is observed in circles with indicators 13, 14>.

However, do not confuse wheel hardness values ​​with abrasive hardness values. According to GOST 2424, the hardness of the grinding wheel is distinguished by a capital letter.

According to GOST R 52587-2006, there are such designations:

• very soft - letters F and G;
• to soft circles - H, I, J;
• medium softness includes marking K, L;
• averages are M, N;
• circles of medium hardness have the letters O, P, Q in the designation;
• solids are designated as R and S;
• very hard - T, U;
• extremely hard include V, W, X, Y, Z.

What grinding wheel hardness should I choose? It depends on many parameters - the characteristics of the material or surface being processed, the physical properties, of course, the power of the grinder. If it is necessary to maintain the exact shape of the material being processed, a wheel with a high degree of hardness should be purchased. Soft ones are used to prevent cracks and burns, also when grinding without additional liquid-lubricant cooling of the surface.

For example, let's take the same grinding wheel 25A, which has a hardness class of K, and a structure of 7. This means that this disc is medium soft and has a medium abrasive structure.

Bundle type

The bond is an indicator of bonding between abrasive grains. Modern grinding wheels have three types of ligaments:

• V (ceramic, previously marked with the letter K);
• B (bakelite, formerly known as B4 and BU);
• R (volcanic, formerly designated by the letter B).

Wheels with ceramic markings have materials mixed and ground in various proportions, such as quartz, sand, clay, etc. Such circles are quite high-strength. However, they should not be used for power grinding of metal.

Bakelite or artificial resin circles are highly elastic and heat resistant. Bakelite is often mixed with reinforcing elements such as graphite.

The vulcanic bond consists mainly of rubber, such circles are used in certain processing industries.

Using the 25A F180 K 7 V grinding wheel as an example, consider the type of bond, where the designation V refers to this disc as a vitrified bond.

Instability class

The accuracy class has three meanings: AA, A and B. The first type is used for work on machine tools, automatic lines. Class A is fairly accurate, while Class B wheels are used for less critical surfacing operations.

Instability has four classes (from 1 - the most accurate - to 4 - the roughest). This designation shows the specialist the ratio of the mass of the abrasive disc to the accuracy of its geometric shape. Often, the marking of the accuracy and instability classes are indicated side by side.

For example, the grinding wheel 25A F46 L 6 V 35 B 3 we are considering has accuracy B and instability 3.

So, circles marked AA have the least imbalance, with accuracy A - 1 and 2, with letter B - from 1 to 4 classes.

What are abrasive wheels - materials of manufacture and technology of application. An abrasive wheel is nothing more than a mechanized grinding block. It is made from grains of abrasive materials mixed with a binder.

The resulting mass is pressed into the required shape and sealed under pressure at high temperature. For use, it is enough to have any rotating drive with an electric motor (or other propulsion), on the axis of which the disk is attached.

Wide choice and various applications

The main types of abrasive wheels

Types of abrasive wheels and the main methods of surface treatment.

Consider the most popular:

• circular grinding - surfaces are processed, the section of which in a plane perpendicular to the axis of rotation is a circle;
• flat grinding - processing of any flat surfaces;
• centerless grinding - as a rule, it is used at enterprises engaged in the processing of external and internal surfaces, such as, for example: camshaft shafts, bearing cages;
• abrasive wheels produce cutting and cutting blanks;
• abrasive grinding of surfaces (for example, a saddle and a needle of a diesel nozzle);
• honing - processing of round surfaces (holes) using special honing heads. It is used in the processing of engine cylinders or
• surfaces of hydraulic pumps;
• polishing wheels - used to give the surface a small roughness and a mirror finish;

Cut-off

Designed for cutting hard materials with little effort. Most often used in manual angle grinders (grinders), but can also be installed on stationary cutting devices.

They are a flat (up to several millimeters thick) disk of abrasive material, bonded with a bundle and reinforced with reinforcement.

The working edge of the disc scrapes the chips from the surface of the material being processed, forming a cut. In this case, the diameter of the disk is reduced, and the surface always remains ready for work, i.e. disk is self-sharpening.

They are divided according to the type of material being processed:

• used for cutting pipes, profiles and sheet metal;
• for concrete and reinforced concrete, when cutting grooves in concrete structures;
• work with stone, to give the necessary shape to blanks made of stone and ceramics;

The variety of sizes is impressive

grinding wheels

Used for emery. With the help of such discs, it is possible to sharpen tools made without the use of hard alloys, as well as finishing workpieces of various shapes.

Grinding wheels in the section are of the following geometric shape:

1. straight profile. They are used for sharpening knives, axes, external and internal grinding, peeling and clean-up work. Can be used for flat grinding.
2. Conical profile. They are used for sharpening teeth of non-circular saws.
3. Double sided tapered profile. They are used for finishing the profiles of shavers and cutters, gear wheels, thread grinding.
4. Straight profile with undercut, single or double sided. Are applied to round, flat and internal grinding, processing of a neck and an end face.
5. Single sided or double sided taper. They are used for trimming the end with simultaneous round grinding, as well as round grinding of the neck and end.

Cup

Subdivided into:

1. Cylindrical. They are used for flat grinding with the end part and sharpening of the teeth of cutting tools, for example, circular saws.
2. Conical. They are used for grinding flat guides and sharpening the teeth of cutting tools.
3. Disc-shaped. They are used for processing and sharpening multi-blade cutting tools and finishing gear teeth.

Conical grinding stones

For household grinders, as a rule, universal straight-profile emery wheels are used, which can be easily changed to cup ones if necessary to sharpen a circular saw. In general, the main advantage of abrasive wheels is their wide range of applications.

note

Having a primitive grinder and a minimal set of emery in your home workshop, you can perform almost any work on sharpening, finishing and grinding products from a variety of materials.

Abrasive grinding wheels, when used correctly, require some tooling to secure the workpiece, or at least guides.

Choice of abrasive wheel

For the correct choice of an abrasive tool, it is necessary to know well the capabilities of the grinding machine - power, working speed, the ability to adjust them. Also, for different types of surfaces to be treated, the appropriate type of emery should be selected.

IMPORTANT! You can not use the grinding wheel, which will be "at hand". Always check that the emery is suitable for the material being processed.

It is also necessary to know if the work requires cooling and lubrication of the working surface of the grinding wheel. If the requirements of the abrasive manufacturer are not met, the emery wheel itself can be quickly disabled and the workpiece can be spoiled. It is important to choose the right grit size for the abrasive wheel.

Grinding wheels are abrasive cutting tools that are used on grinders, machine tools and manual processing of various types of surfaces. Such products are porous bodies containing grains of abrasive materials, as well as artificial and natural binding elements.

Grinding wheel grains can be compared to the teeth in a regular saw, as they perform the same tasks. The difference between these two tools is that on the abrasive product the grains are "scattered" around its perimeter, and the teeth, saws, as you know, are located exclusively along its edges.

Many solid particles of grinding wheels, installed, for example, on, quickly and efficiently clean the surface, removing unnecessary components from it. Surfaces that can be processed with an abrasive tool can be made of carbon steel, ductile iron, durable plastic, bronze, non-ferrous metals, glass, wrought iron.

In addition, the described circles allow efficient cutting of bricks, roofing slates, drywall, all kinds of ceramics and concrete. With their help, you can process a variety of surfaces, as well as perform grooves and cuts of the required depth and shape (no need to confuse grinding wheels and, their functions are completely different).

2 Grinding wheels - classification

According to the old GOST 2424-83 "Grinding wheels: specifications" and the current new standard ("Grinding wheel: GOST R 52781–2007"), such abrasive products are manufactured in the following types:

• with two grooves;
• double-sided conical;
• straight profile;
• with a conical one-sided or two-sided undercut;
• ring;
• dish-shaped;
• cup conical or cylindrical;
• conical;
• with a recessed center;
• with one- or two-sided undercut;
• with hub and double-sided undercut;
• with a two- or one-sided hub;
• with hardening components and recessed center;
• with fastening pressed-in elements (ordinary and ring);
• with a cylindrical recess on one side and a conical recess on the other;
• with cylindrical and conical undercuts on both sides or on one side.

For an ordinary person using grinding wheels, their "household" classification according to the purpose and features of the use of products is much clearer. The most commonly used circles are:

3 Features of marking grinding products

It is almost impossible to bring together all the parameters by which it is customary to subdivide grinding wheels. They have different brands depending on the following characteristics:

• grain;
• type of abrasive;
• type of bond (bakelite, ceramic, volcanic);
• size and geometric shape;
• unbalance and accuracy class;
• hardness index;
• the ratio between the bond, the abrasive material and the pores of the product;
• maximum speed.

The choice of a specific brand of grinding wheels takes into account the characteristics indicated above. Moreover, for the processing of some materials, the type of abrasive and the shape of the circle may be even less important than the features of its structure and the level of hardness. In the full marking of abrasive tools for grinding a variety of surfaces, all of the above parameters are usually indicated.

Manufacturers often mark grinding wheels in their own way (GOST for the production of different products may also be different). We present the most common marking option, which allows consumers to easily decipher information about the product. If you see a circle in front of you with the designation 25A25SM26KB3, then you can understand that:

• for its production, white electrocorundum was used as an abrasive - 25A;
• its grain size is (in microns) 315–250 - the number 25;
• it belongs to the class of medium-soft - CM2 and has an average structure - 6;
• a ceramic bond is used - K;
• circle accuracy class - B, and unbalance - 3.

Approximately the same can be deciphered and other types of products. But they may lack some parameters (for example, accuracy class) or, conversely, add new ones (most often, circumferential speed).

4 Grit size of the grinding wheel

We cannot but say separately about the graininess of products for grinding - a very important characteristic, on which the surface cleanliness obtained after its processing depends. It, in addition, determines a number of other parameters - the wear of the wheel, the performance indicator of the grinding operation, the amount of metal removed in one pass, and others.

The grit size of the grinding wheel should be chosen taking into account what allowance is planned to be removed, what surface roughness needs to be obtained, what material is being processed. The surface will be cleaner the smaller the grit size used. At the same time, fine grain often causes clogging of the wheel and burning of the material being ground. Yes, and directly the performance indicator of the grinding process is reduced if products with a small grain size are used.

We add that the grain size according to GOST 1980 (3647) is indicated in units equal to 10 microns, in the more modern standard R 52381-2005 - the letter F with a certain number. The grain will be the smaller, the higher this number.

5 Dressing grinding wheels

The geometry of the wheel during its operation may be violated, since the grains of the abrasive break out of the bond as a result of smoothing, abrasion, and destruction. In order to return the product to its cutting capabilities and its original geometric shape, the wheel is dressed. This process is understood as the removal of a bond and an abrasive from the surface of the product with a special tool.

Editing is carried out in different ways using a diamond-free or diamond tool. At industrial enterprises, the procedure is usually carried out with a free abrasive or using rolling technology, and in home use, you can use a simple device for dressing the grinding wheel, which makes it possible to reprofil it, level it and clean it from clogging (in other words, stripping).

Before it becomes a finished product, a metal workpiece is very often processed using abrasive grinding wheels. This is done in order to ensure a high surface smoothness.

Scope of application of abrasive grinding wheels

Polishing any elements not only makes them more attractive in appearance, but is 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 smoothed to minimize friction. It is worth noting that a variety of materials are subjected to grinding - metal, stone, plastic, wood. Also, abrasive wheels are actively used in a variety of grinding machines.

Grinding abrasive wheels may differ in shape, as they are used for various purposes. In addition to surface smoothing, metal parts often need to be derusted. To realize this task without special circles is almost impossible. By means of removable nozzles for the grinder, you can make recesses, 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 the polishing of precious metal products is the main part of the work. Stoneworkers working with ornamental minerals and semi-precious stones also use this tool.

There are special varieties of grinding nozzles mounted 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 grinding wheels are great for removing old paint from plumbing, cleaning pipes from corrosion, and other similar jobs.

Types of grinding wheels

To correctly process the part, it is necessary to determine the type of grinding. This will allow you to choose the right abrasive nozzles. The main selection criteria are the material of the workpiece and the nature of the impact on its surface.

So, grinding wheels with a straight or annular profile are widely used in everyday life and for small metals, grinding operations performed by their end surface. These circles are relevant when working with glass, porcelain, stone (here you can also use flat nozzles with one- or two-sided recess, which are also convenient when performing peeling work).

The most common are conical circles, which can be both double-sided and regular. They can be used for all of the above works for surface treatment of parts with a plane. Also, with their help, it is possible to perform recesses in almost any material.

For the processing of many parts, the best options are a grinding cup wheel and a wheel with disc nozzles (most often they have all-metal nozzles and diamond coating). The cup circle resembles a straight profile tool with a conical undercut. The main difference is that the end is located at right angles to the side plane.

The range of abrasive wheels according to the type of abrasive is quite wide. In addition to the previously mentioned diamond coating, electrocorundum is widely used. With the help of electrocorundum one-piece nozzles are made. Most often they do not have a base and a pressed core.

Silicon carbide wheels are also in demand. The latter are divided into two types: black and green (nozzles have the corresponding color). Green is more fragile.

Elbor belongs to high-strength abrasives. This material is based on cubic boron nitride. In terms of operational properties, it is not inferior to diamond, while elbor has a higher level of thermal stability.

Vulcanite and bakelite grinding wheels

Diamond coating has a rather high cost, so it is applied in a very thin layer on a metal base. Abrasive wheels with less strength are formed in a different way. Often, a bonding ceramic composition is used for this purpose, where the main components are materials of inorganic origin (quartz, clay, etc.). Highly ground, these binders are added to the selected abrasive during the formation of the wheel, which provides the finished product with increased rigidity, but also with appropriate brittleness.

Bakelite nozzles are in great demand in the market. They owe their name to the main filler - bakelite (artificial resin). This binding component gives the wheel elasticity and a kind of elasticity, but at the same time wear resistance decreases 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 workpiece. Bakelite nozzles are free from this drawback. They are much softer, so they heat the metal very weakly and are able to self-sharpen when machining a part.

Grinding wheel with vulcanite binder is even softer. Here, the main abrasive element is synthetic heat-treated rubber. In other words, in the production of such grinding nozzles, vulcanization is used, which is reflected in their name. Vulcanite wheels have a higher cost compared to ceramic abrasive. However, despite the increased elasticity, their wear resistance is beyond praise.

Grinding wheel selection

The main requirement put forward to the abrasive nozzle concerns its hardness. The hardness of the nozzle must necessarily be higher than the hardness of the workpiece. In this case, it is undesirable that these parameters differ greatly, otherwise the probability of overheating of the treated surface increases. One of the most important criteria in the selection of abrasive is also the size of its grain.

Coarse 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 glossy surface can be provided by a fiber circle. If its tip is softer than the workpiece, the machining result will be good, but tool wear will also be very strong.

If a certain amount of material remains on the workpiece, then it can be removed from the surface of the part using grinding wheels. Sharpening is performed in the same way, and any notches are smoothed out.

All grinding wheels differ both in appearance and in the method of manufacture. However, this tool of any brand, regardless of size, is able to improve the technical and operational properties of the product.

In addition, after grinding, the appearance of the treated surface is improved. For example, decorative mirrors, crystal chandeliers and porcelain tableware are processed with small-sized grinders, resulting in products that acquire a silky smoothness.

In some cases, specialists use a grinding tool of a non-standard configuration. Specific grit and circle shape are used for particularly complex professional tasks. For example, for a complete set of machines on productions.

Types of grinding wheels

The classification of grinding wheels is determined by GOST R 52781–2007.

It stands for:

• material of manufacture;
• scope;
• technical requirements.

However, the main value is the operating conditions.

Grinding wheel shapes

Both among professionals and in domestic use, classification according to the options for using circles is popular.

According to the purpose and features of use, the following types of grinding wheels are distinguished:

• Self-locking. Fastening method - Velcro. Differ in strong coupling with the grinding machine.
• Petal. Flap-type grinding wheels are characterized by the complete absence of secondary burrs. They perfectly adapt during use to any surface due to the fan orientation of the petals.
• Fiber. Requires a support plate of a given section for engagement with the grinder. Used for cleaning any materials (from wood to steel).
• Diamond. Used for finishing material.
• Metal discs. They are subject to thorough analysis (testing) for strength, as they are required for the final work with the seam after welding.

Ligaments: varieties and classification

Types of bonding of grinding wheels are determined by the area of ​​use. Experts divide them into organic and inorganic.

Types of grinding wheels by types of bonds:

• Bakelite. Required for finishing. Suitable for sharpening and flat grinding. The bond is characterized by a high polishing effect, but it is not resistant to aggressive chemical environments.
• Ceramic. One of the most fire resistant This type of tool is characterized by the highest chemical resistance, as well as the ability to maintain an edge profile. However, the bond has a low coefficient of resistance to mechanical stress. In particular, it must be protected from bending loads.
• Magnesian and silicate. They are particularly sensitive to coolants. They are endowed with a low coefficient of strength, but they emit less heat during operation.
• Volcanic. Needed to work with particularly complex curly surfaces, as well as for profile grinding. It has rubber and sulfur in its structure, so the scope is very specific. The structure of these grinding wheels is very dense, which provokes increased heat transfer during the grinding process. Without periodic breaks in work, it softens, and the cutting process becomes not so high quality. With strict observance of technological standards of operation, it guarantees a perfectly flat surface, therefore it is used for finishing grinding curly surfaces with complex geometry.
• Metal. Required for grinding especially hard alloys.

pivot table

It is from the type of bond of grinding wheels that the hardness of the tool and its strength depend.

Wheels for grinder

Everyone who has come into close contact with grinding or cutting knows what grinding wheels are for grinders.

On the market they are presented in a wide variety:

• abrasive circles. Designed for grinding work and fast cutting.
• Diamond coated discs. The tool is relevant for construction work. Without difficulty, not only stone or concrete, but also metal are divided into fragments. There are solid and segmented options on the market.
• Saw discs. Similar to a saw, but a more powerful alloy is used in their manufacturing process. The most demanded disk from this series from tungsten carbide.

All types of grinding wheels for grinders have a standard diameter. For example, the smallest model has a size of 115 mm. For private use, 125 mm discs are most widely used.

It should be remembered that marking when choosing discs for a grinder is of great importance. This tool has great power and speed. The slightest discrepancy between the selection of the emery disc and the size of the installed shaft can provoke traumatic situations. Only the right selection of equipment will ensure the effective performance of the required task.