What does a grinding wheel look like?

Labeling of grinding wheels: deciphering

Grinding disc. one of the types of abrasive tools, along with heads, segments, bars, abrasive belts and sandpaper, actively used for processing various kinds of surfaces. The abrasives used for grinding wheels are strong, hard substances: diamond, corundum, quartz, as well as artificial materials. electrocorundum, synthetic diamonds, silicon and boron carbide, etc. These grains are used to mechanically grind the surface of other materials, in terms of their function they can be compared with the teeth of an ordinary saw, but located not on the edges, but on the perimeter of the disk. Grinding wheels can be used on many materials: carbon steel, glass, plastic, bronze, wrought iron, and non-ferrous metals. They are also used in tools for cutting bricks, stone, ceramic tiles, drywall.

Non-professional classification, familiar to many, divides grinding wheels into the following types:

• Discs with the so-called “Velcro”. a special fabric that is applied to the sanding paper.
• Petal wheels. have a surface of abrasive material arranged in a fan overlapping layers. They are very durable, provide an even surface after processing, and are most often used for grinding pipes or wooden surfaces.
• Fibre sanding discs, consisting of vulcanized paper with a sandwich structure. They are attached to the machine by means of a support plate with the required cross-section. Fibre discs are used for scraping metal, wood, steel products.
• Diamond wheels used for finishing. Generally of low strength.

Grinding wheels. what they are for and what they are made of?

Grinding wheels are quite widely used both for professional purposes and by home craftsmen. Let’s look at the main characteristics and some features of these tools.

Grinding wheels are a cutting abrasive tool that is used on grinders, machines and in the manual processing of various types of surfaces. Such products are porous bodies containing abrasive grains, as well as artificial and natural binders.

The grit of grinding wheels can be compared to the teeth in an ordinary saw, as they perform the same tasks. The difference between the two tools is that on the abrasive product the grains are “scattered” along its perimeter, while the teeth, saws are known to be exclusively on its edges.

The many hard particles of grinding wheels mounted, for example, on an electric grinder clean the surface quickly and efficiently, removing unwanted components from it.Surfaces that can be machined with the abrasive tool can be made of carbon steel, malleable iron, strong plastic, bronze, non-ferrous metals, glass, wrought iron.

In addition, the described circles allow you to effectively cut bricks, roofing slate, drywall, all kinds of products from ceramics and concrete. With their help it is possible to process a variety of surfaces, as well as to perform grooves and cuts of the required depth and shape (no need to confuse grinding discs and drills for metal, their functions are completely different).

According to the old GOST 2424-83 “Grinding wheels: technical conditions” and the new standard (“Grinding wheel: GOST R 52781-2007”) in force today, such abrasive products are made of the following types:

• with two notches;
• double-sided conic;
• straight profile;
• With conical chamfering on one or both sides;
• annular;
• disk;
• cup conical or cylindrical
• tapered;
• With a recessed center;
• With one or two sided notch;
• With a hub and a double-sided notch;
• with a double-sided or single-sided hub;
• With reinforcing components and recessed center;
• with pressed fasteners (normal and ring-shaped);
• With a cylindrical notch on one side and conical on the other;
• with cylindrical and conical notches on both sides or on one side.

The average person who uses grinding circles, much clearer their “household” classification for the purpose and features of the application of products. Most often such circles are used:

• Self-gripping with velcro. Products have a secure grip with the support of the grinder due to the presence of a special fabric on the sanding paper.
• Petal. They are characterized by excellent adaptability to the surface to be grinded, high elasticity. Products get their name because of the fan orientation of the blades on the abrasive material. Their important advantage is the absence of secondary burrs. Most frequently the petal structures are used for machining of pipes, and if the lamellae have dissections. for wooden and shaped surfaces.
• Metal grinding wheels. Indispensable for weld dressing and deburring. Grinding wheels of this type are usually tested particularly thoroughly for their mechanical strength.
• Fibre. For their attachment to the grinder a special support plate of the required cross-section is designed. This wheel is made of multi-layer vulcanized paper and is suitable for deburring of stainless steel, wood, steel, metal products.
• Diamond. Specialists advise to use them for final surface finish. Always keep in mind the relatively low strength of diamond and its high brittleness.

It is almost unrealistic to summarize all the parameters by which grinding wheels are commonly classified. They have different grades depending on the following characteristics:

• grit size
• type of abrasive;
• type of bond (bakelite, ceramic, vulcanite);
• Size and geometric shape;
• Unbalance and accuracy grade;
• hardness index;
• the ratio between the bond, the abrasive material and the pores of the product;
• maximum speed.

The choice of a particular grade of grinding wheels takes into account the characteristics mentioned above. And for some materials, the type of abrasive and shape of the wheel may be even less important than the features of its structure and hardness level. The full marking of abrasive tools for grinding various surfaces usually indicates all of the above parameters.

Manufacturers often label grinding wheels in their own way (GOST for the release of different products can also be different). Here is the most common version of the marking, which allows consumers to easily decipher the information about the product. If you see a circle with the designation 25A25CM26KB3 in front of you, you can understand that:

• for its production, white electrocorundum was used as an abrasive. 25A;
• its grit size is (in microns) 315-250. figure 25;
• it belongs to the class of medium soft. SM2 and has a medium structure. 6;
• uses a ceramic bond. K;
• accuracy class of the wheel is B, and unbalance is 3.

Other types of products can be deciphered in approximately the same way. But they may be missing some parameters (e.g., accuracy class) or, on the contrary, adding new ones (most often. peripheral speed).

Product quality attributes

There are many different parameters by which such products are classified. There are even more types of marking of abrasive wheels due to the fact that there are many different combinations of these properties. The main parameters of abrasive wheels for sharpening machines are considered to be

Grit index.
• Type of abrasive material.
• Binding agent.
• Size and shape.
• Grinding material hardness.
• Operating speed.

Choose a wheel with the appropriate grit size, which is indicated in the marking on the product itself.

Grit size of the fixture

This is the most important feature. The grit size determines how smoothly the workpiece will be ground. Also the amount of wear, the productivity, and the thickness of the layer removed per cycle are largely dependent on the grit index. The smaller the grit of the tool, the finer the finish. However, working speed with such a grit size decreases. This type of fixture also frequently results in burnt workpieces.

The old standard defines the grit size in microns, the new standard is designated by the letter F and the number. The higher the digital component, the lower the grit. All these values are summarized in the table of grit of grinding wheels.

Materials of manufacture

As with all characteristics, the requirements for the material from which grinding wheels are made, correlate with GOST. The minimum conditions are wear resistance, low heat dissipation, hard surface. Based on these conditions, the abrasive tool is made of such material:

A substance that has a base of aluminum oxide (Al2O3) is called bauxite-bonded electrocorundum. GOST 28818 allows potassium oxide to be added to increase the hardness. This allows them to retain their original properties when the temperature rises in conditions of intensive work. Such wheels are marked as follows: 12A. 15A. normal, 22A. 25A. increased hardness.
• The same material with a carbide base includes chromium, titanium, zirconium, silicon compounds for work with hardened metals. Silicon carbide (52C. 65C) is needed to resist temperature fluctuations when cooling the workpiece. These products are marked with the letter, A, and figures ranging from 38 for zirconia to 95 for titanium.
• Round spherical corundum grains are obtained by blowing liquid aluminum oxide, have an increased hardness and are used for the abrasive treatment of carbide products. Marked with the letters ES.
• Monocrystalline monocorundum structure is the reason for durability of grinding wheels. Very expensive because of complex production processes. They can be recognized by the marking 43A, 44A and 45A.

Application of bonding materials

Special substances are used in grinding wheels for dense packing and protection against breakage. Their quality, grade, and even distribution influence all the characteristics of an abrasive tool. And also the presence of these materials shows the ability to self-sharpen the milled areas of the grinding stone. If the bonding agent is not suitable for the surface to be dressed, the tool loses its main property, the wear increases, the unworked grit is chipped away, the grinding wheel burns and salts.

As binding elements can be used organic and inorganic binder. The former are ceramic and silicate materials, the latter are bakelite and vulcanite.

The following materials are used in ceramic binder: refractory clay, quartz and feldspar. They are strong, durable, with a stable cutting edge. Tools on such a base can be cooled with special emulsions. Low-thickness circles are destroyed by lateral impact. Their designations are K0, K1, K3, etc. In their manufacture, silicon carbide or electrocorundum grains are used. Grinds well by all means except cutting and use in narrow grooves.

Powder of bakelite resin and lacquer makes up the bond B, B1, B2 and others. These grinding wheels are thin, firm and elastic. However, when heated, such a compound floats and grains fall out. Cryolite is added to the binder to increase heat resistance. Wetting is not permitted with basalt-bonded grinding wheels.

A mixture of synthetic rubber and sulfur gives a vulcanite bond. Its elasticity is higher than that of Bakelite, but its thermal stability is poorer. Elasticity allows the manufacture of thin cutting discs marked B, B1, B2.

High-strength metal bonds are produced on copper, tin, aluminum and other bases. Used in manufacture of diamond and CBN grinding discs.

Hardness values

This property describes the ability of a disc to retain its grain when subjected to external influences. The lower it is, the faster the abrasive breaks down. The deciphering of the hardness of grinding wheels for machine tools is as follows:

Soft M 1 to M 3.
• Medium soft CM 1. CM 2.
• Medium C 1 to C 2.
• Medium-hard CT 1. CT 3.
• Hard T 1. T 2.
• Very hard WT 1. WT 2.
• Extremely hard CT 1. CT 2.

This is determined by the depth of recess from the sandblaster or with a Rockwell hardness tester. Medium-hardness grinding discs are most commonly used. They are most productive and long lasting. Soft tools are suitable for internal and flat grinding. When turning threads and small-diameter workpieces, stiff circles are needed. As a rule, the harder the workpiece, the softer the abrasive tool is needed.

Grinding wheel accuracy

When determining this parameter, existing cracks, cavities and the position of the surfaces in relation to each other are evaluated. The most precise accessories are characterized by minimum discrepancies and are installed on precision machines of high precision machining and on high-speed equipment. Marked with the letters AA.

The following accessories are slightly inferior to the highest quality ones in terms of precision. Identified by the letter, A. The samples of low accuracy category are one and a half to two times inferior to accessories, A. grade. Labeled with B and used for less precise grinding operations.

Profile

The profile of a wheel determines its suitability for certain operations. Let’s list the most commonly used types of profiles:

• Flat with a straight profile. internal or centerless grinding, processing of tores, etc. operations.
• Flat double-sided with conical profile. machining of gears and simple threads.
• Flat with a notch. circular grinding, trimming of ends.
• Cylindrical and tapered wheels. tool grinding, etc. operations.
• Disc wheels. sharpening tools with several cutting blades.

Marking and selection of grinding wheels

Grinding wheels are characterized by geometric shape (type), type of abrasive material, its grit size, type of bond, hardness, etc. And when choosing a grinding wheel, characteristics such as degree of hardness or structure may be more important than the type of abrasive.

The complete marking of grinding wheels contains:

• lap type;
• its dimensions;
• type of abrasive material
• grit number;
• degree of hardness;
• Structure (ratio between abrasive, bond and pores in the tool body);
• type of bond;
• maximum speed;
• accuracy grade;
• class of unbalance.

Marking of grinding wheels made in accordance with different editions of State Standards has some differences concerning the designations of grit size, hardness, abrasive grade and bonding. Manufacturers label their wheels differently, using old or new designations and excluding some characteristics. The following are examples of the deciphering of the designations of grinding wheels.

Grinding wheel marking

abrasive material: 25A. white electrocorundum; 2. Grit size (old marking): 60 (according to GOST it should be 63). 800-630 microns; 3. hardness: K. medium soft; 4. structure: 6. medium; 5. bond: V. ceramic; 6. unbalance grade: 2

Marking of the grinding wheel

abrasive material: 25A. white electrocorundum; 2. grit (old marking): 60 (according to GOST it should be 63). 800-630 microns; 3. hardness: K-L. Depending on circumstances may be K or L. medium soft; 4. bond: V. ceramic.

Marking of the grinding wheel

abrasive material: 25A. white electrocorundum; 2. grit (old marking): 25. 315-250 microns; 3. hardness (old marking): CM2. medium soft; 4. structure: 6. medium; 5. bond (old marking): К. ceramic; 6. accuracy grade: B 7. unbalance class: 3

Abrasive wheel marking

abrasive material: 25A. electrocorundum white; 2. grit size: F46. average size of 370 μm; 3. hardness: L. medium soft; 4. structure: 6. medium; 5. bond: V. ceramic; 6. cutting speed: 35 m/s; 7. accuracy grade: B 8. unbalance class: 3

Designation of grinding wheel

abrasive material: 14A. electrocorundum normal; 2. grit: F36-F30. extended range including F36 (average 525 μm) and F30 (average 625 μm); 3. hardness: Q-U. Depending on circumstances can be medium-hard, hard, very hard; 4. bond: BF. bakelitic with the presence of reinforcing elements; 5. unbalance class: 1

The choice of grinding wheel grade must take into account all of its characteristics.

Grinding wheel types and sizes

The following types of grinding wheels are produced (designations in parentheses are given according to the old GOST 2424-75):

• 1 (PP). straight profile;
• 2 (К). annular;
• 3 (3П). conical;
• 4 (2П). double-sided conical;
• 5 (PV). with one-sided notch;
• 6 (CZ). cup cylindrical;
• 7 (PVD). with two notches;
• 9. with double-sided notch;
• 10 (PVDS). With double-sided notch and hub;
• 11 (NC). cup conical;
• 12 (Т). disk
• 13. disk-shaped;
• 14 (1Т). disk-shaped
• 20. with one-sided conical notch;
• 21. with conical notch on both sides;
• 22. with a tapered notch on one side and a cylindrical notch on the other;
• 23 (PBC). with conical and cylindrical notches on one side;
• 24. with conical and cylindrical notches on one side and a cylindrical notch on the other side;
• 25. with conical and cylindrical notches on one side and conical on the other;
• 26 (PVDC). With conical and cylindrical notches on both sides;
• 27. with recessed center and reinforcing elements;
• 28. with recessed center;
• 35. straight profile, working face;
• 36 (PN). With pressed fasteners;
• 37. ring with pressed fasteners;
• 38. with one sided hub;
• 39. with double-sided hub.

Some types of grinding wheels

In addition to the shape of the profile, grinding wheels are characterized by their dimensions DxTxH, where D. outer diameter, T. height, N. bore diameter.

Types of diamond and CBN wheels are regulated by GOST 24747-90. The marking of the shape of CBN and diamond grinding wheels consists of 3 or 4 symbols carrying information about the shape of the cross-section of the body, the shape of the cross-section of the CBN or diamond-bearing layer, the location of the latter on the wheel, the design features of the body (if any).

How to choose the right grinding wheel

When choosing a grinding wheel, it is necessary to have a good idea of what it will be used for and on what device. For example, if it is an electric grinder, it requires a wheel to work on ordinary metal (steel, aluminum, bronze). At the same time it is necessary to know exactly the diameter of the seating hole and the mounting size. It is very important that the speed of rotation of the power tool does not exceed the parameter specified on the marking of the grinding wheel. Grit size and type of abrasive also matter, but one need not delve into these parameters if one acquires a grinding wheel for universal use (as a rule, this is indicated on the label). If you intend to process any soft or very hard materials, the choice of grinding wheel should be approached more carefully and, if necessary, consult a specialist.

For some reason, the marking of many grinding wheels does not include such a parameter as structure, although its description implies that it should directly affect the runout level of the new disc. Is it true and does the structure value directly relate to runout?? If anyone can answer this question, please do so in the Комментарии и мнения владельцев of this article.

Paper-based circles with Velcro

A Velcro-bonded grinding wheel was given its nickname by the principle of fastening to the grinding tool support. The Velcro cloth overlaid on the grinding paper is firmly connected to the hooks of the support and does not fly off even at high speeds. Self-gripping grinding wheels are suitable for processing all available materials. It’s all in the abrasive grain, the type of his filling and additional bonds. If you look closely at the coloring of circles, you can see that even brown circles have different shades. The color of the wheel depends on the dye applied during manufacture, and is a kind of marking for such abrasives. Most often, abrasive tool manufacturers use brown color for tools with aluminum oxide abrasive grain. corundum, which are designed for grinding metal or wood. Blue indicates that the grinding wheel is traditionally designed for grinding stainless steel and contains zirconia alumina. zirconia alumina grit. Sanding wheel in different shades of white is used for sanding lacquered surface, paint, putty. Black for grinding wheels with silicon carbide grit for grinding mineral materials. It is possible to accurately determine the main purpose with the help of color coding, but what to do when you do not have a grinding wheel with a direct purpose.

Self-adhesive grinding wheels are true “universal soldiers. Virtually every type can be used for purposes other than the intended use. There is little information about these capabilities in the description of a particular type. To select the grinding tool for processing a specific material should be compared with its characteristics (hardness, toughness, structure). For example: if the material is soft, such as fibreboard, paper or chipboard, the PS18 open grit emery wheel is the right choice. The same type of wheel is also suitable for removing rust from metal. Open grit filling prevents clogging with sanding products. the PS21 zirconcorundum grinding wheels are ideal for grinding hardwood, e.g. parquet. With the processing of stainless steel products cope well circles white paint, varnish, putty. Special additives prevent the surface from overheating and since only PS33 can be supplied in fine grit, up to P600, there is no better option for pre-polishing. When working with self-adhesive grinding circles to take into account the speed, pressure and grain size, which will achieve optimal results.

In the near future, self-glued and Velcro-bonded film-backed grinding wheels with backing pad should be available in our catalog. Their development and testing are nearing completion. Film-based grinding discs allow you to occupy a niche of abrasives and tools for the body repair and automotive industry.

Criteria for selecting a grinding wheel

Choosing a wheel for the grinder, it is recommended to carefully read its characteristics:

• Disc material. Marking from 12A to 16A electrocorundum normal (characterized by heat resistance, excellent grit strength). Suitable for work with wrought iron, steel, cast iron and bronze. Marking from 22A to 25A for discs with a greater degree of uniformity of coating, high hardness and ability to self-sharpen. Higher marking. higher hardness. Grinding discs 52-22C and 62-64C are brittle.
• Disc size is standardized according to GOST, where D. outer diameter, d. inner diameter, h. height.
• Grit size: grit (fraction 00 to 6), powder (fraction 2 to ), microgrinding powder and fine microgrinding powder (finest grit).
• Disc variety.
• Abrasive hardness: BM1, BM2. soft, HT. extremely hard.
• Grit bonding material: R (B) vulcanite bond (rubber); V (K) ceramic and B (B4 or BU) with artificial resins.
• Disc unbalance. the ratio of the disc’s weight to its shape. Grade A indicates that the disc can be used on high-precision machines. Precision B is a universal disc, and AA marked discs are the perfect geometric shape.
• Disc texture is indicated by numbers: 1 to 4 means high-density (great amount of abrasive), 5 to 7 indicates the medium-density coating.

What is a diamond wheel??

This tool has become very popular in recent years. Despite their high price, diamond wheels are very much in demand for a variety of reasons. First, this abrasive is very wear-resistant, so it can process much more material than the classic version. Secondly, the quality of work is much better and the surface is cleaner, which is essential, especially where this is required. The so-called tortoise. Diamond grinding wheel (flexible). Ideal for stripping concrete, granite and other building materials. Usually the machining process with such a tool is characterized by the fact that it significantly reduces labor intensity and increases the speed of execution. This can also be seen as a cost effective measure. This type of wheel wears out much more slowly than the classical grinding wheel. Diamond tools are also characterised by their low noise level.

It can be said with great confidence that at the present time universal circles. the most popular. Their universality lies in the fact that they are able to work a wide range of materials. The simplest example can be given by picking up a PP grinding wheel. It is suitable for external grinding of workpieces with a diameter of 250-1100 mm, internal grinding of workpieces up to 1500 mm, centerless grinding, flat grinding of workpieces with different diameters. This makes them practically indispensable for jobs of varying complexity. Of course, for some other applications other materials are used. For example, the wheel type 36 (PN) is used for roughing work and very seldom for finishing work.