A kind of sandpaper. Grinding wheel marking and selection

30.05.201827.05.2017

Used for grinding, polishing and surface cleaning. For manual processing, choose sheet or roll paper (you can cut a piece of the desired size from it). For machine room - finished goods from sandpaper: sanding belts, circles and strips with Velcro. In this review, we will tell you in detail what types of sandpaper and its grain size are.

Types of sandpaper

The main characteristic of sandpaper is graininess, i.e. the number of abrasive grains per square inch of surface. With a low grain size, the particle size is relatively large. Coarse paper is used at the beginning of processing. It allows you to roughly sand and clean the surface, remove the remnants of old paint. After it, there are scratches, so further grinding is necessary with finer sandpaper.

As the grain size increases, the grain size decreases. This skin is called fine-grained. It is used for fine, thorough processing, in particular before painting. A simple example - you decide to repaint your wardrobe. You will need 2 types of wood sandpaper, each with a different grain size. Coarse first (P60), then medium (P100). Ideally, it is better to walk with a third, finer sandpaper (P150).

The second most important parameter is the type of stem. There are two main types of paper:

With a paper base. It can be normal and moisture resistant. Of the advantages - it is cheaper, does not stretch during work. The finest grain can be applied. Of the minuses, it is less resistant to wear and tear.
With fabric base. It is more expensive than paper, but it has high tensile strength and is more resistant to moisture. Due to its elasticity, it can be stretched in length. The stiffer the base, the more durable the tape will be.

Sandpaper grit table

Depending on the grain size of the paper, there are two marking standards: Russian (with the letters H and M) and international (with Latin P). Below you will find a table of markings correspondence. Coarse and medium-grained papers are shown in blue, and fine-grained papers in yellow. The proposed type of work is also indicated.

Created on a fabric, paper or other basis with a layer of abrasive powder. Used sandpaper or abrasive paper for manual or machine processing of various surfaces to prepare them for priming, painting, sanding or to remove old paint. As a rule, this material is sold in rolls, but today other tools have been developed using this material, for example, emery sponges.

Sandpaper grit

Grit is one of the most important characteristics of sandpaper. It displays the amount of abrasive particles per inch of material. Therefore, the lower the grit value, the coarser the sandpaper. The modern market for abrasive skins offers products with a grit size of 12-4000.

A grit size of 12-16 means that the sandpaper is very rough. Most often it is used to remove old drying oil or varnish from the floor. An indicator of 24-40 also reports that the sandpaper is rough, it is used to remove paint from wooden surfaces.

For coarse sanding after removing the paint, use paper of 60-80 grit. And sandpaper 80-150 is more gentle. It is used after rough grinding to smooth and level the wood surface. It is also used for intermediate grinding, removing various imperfections, including marks. Sandpaper of this grit is called medium.

Fine sandpaper has a grain size of 150-180. With its help, the final sanding of wooden surfaces is carried out before painting and priming them. A 200-240 grit material is very fine. Sandpaper these numbers are used for intermediate sanding after priming before painting.

The grit size of extra fine sandpaper is 240-320. This paper is usually used for the final sanding before painting the wood. Thanks to it, you can gently remove dust marks that may appear after painting the surface.

Super fine sandpaper has 360-4000 grit. With its help, the final polishing of the painted wood is carried out. It allows you to get rid of the unnecessary shine of the glossy surface, as well as the smallest scratches and stains.

Sandpaper classification

Most often, sandpaper is classified according to the type of substrate. Let's look at the features of paper-based sandpaper. High-density sandpaper can withstand heavy mechanical stress. In addition, the base can be conventional or waterproof.

The advantages of this material include low cost. In addition, the paper base does not lengthen its shape, and even the smallest fractions of grinding material can be applied to its surface. If we talk about the shortcomings, then the strength and durability leaves much to be desired.

Cotton or polyester can be used as a fabric base in sandpaper. At the same time, the fabrics are impregnated with a special resin, which allows them to give them additional strength and resistance to moisture. The main features of the fabric base include elasticity and tensile strength.

Sandpaper can have a combined base, which can be obtained by gluing fabric and paper. You can also find fiber-based material in stores. But this applies to fiber discs, which are used on an emery machine and can handle particularly hard surfaces.

The abrasive can be applied in different ways

Emery paper can have a half-open and open fill, in addition, the fill is closed and continuous.

Products with half-open and open filling differ in that about half of the surface of the base is covered with abrasive grains. With the help of such paper, relatively soft and friable material is processed, including some wood species. Due to the special structure of the surface, lumps do not form on it, which makes it possible to exclude the clogging of the gaps between the grains with grinding waste.

Solid or closed grit sandpaper has a backing completely coated with abrasive grains. This material is optimal for working with hard surfaces.

Having dealt with the types of sandpaper, you were able to see what material can be used for different purposes.

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Sanding paper is an invention of John Oakey, which today is one of the most common abrasive materials... It is used for both manual and machine grinding. It is indispensable for carrying out almost any preparatory workstarting with removing old paintwork and finishing with sanding surfaces before polishing.

Abrasives for abrasives

The structure of this material includes a backing and an abrasive. The latter for modern sandpaper is made from artificial aluminum oxide (electrocorundum) or silicon carbide (corundum). There is also an emery on sale with an abrasive of garnet, elbor (borazon) and synthetic diamond.

Electrocorundum is most widely used due to its excellent cutting ability. It can withstand quite strong pressure, which significantly increases the abrasive properties of the emery. Electrocorundum is produced by reduction melting of a charge (a mixture of aluminum shavings, low ash carbon filler, bauxite agglomerate and recycled materials) in an arc furnace. In some cases, alloying elements are added to the charge to improve the characteristics of the abrasive paper.

Corundum is produced by sintering a mixture of silica and graphite in an Acheson electric furnace. This abrasive is harder than aluminum, but has increased fragility. It retains abrasive properties for longer, and its surface is excellent against clogging. This material used in the processing of glass and plastics, as well as in metal grinding.

Sanding paper with garnet abrasive is used when working with soft materialssuch as a tree. It wears out pretty quickly, but it provides a perfectly smooth surface. Elbor and artificial diamond are at least three times as hard as corundum abrasives. These materials are complex and expensive to manufacture, so they are rarely used to make emery.

Abrasive grain classification

Granularity - main characteristic sandpaper. Abrasive grains can have sizes from 3-5 to 1000 microns, which determines the scope of the material. Earlier in our country the classification of abrasive skins was regulated by GOST 3647-80, now GOST R 52381-2005 is in force. Meanwhile, the international standard ISO 6344 (FEPA) is widely used in the world, although the USA and Canada have their own - ANSI, and in Japan and China - JIS and GB2478.

In the modern Russian standard, as in FEPA, the letter P with a number (the number of sieve wires per square inch) denotes the grain size of the sanding paper in ascending order. But in many countries of the former USSR, grain size continues to be expressed in tens of microns and is designated by the corresponding number with the letter N. The smallest emery in the Soviet marking has an additional letter M, and its number corresponds to the grain size in microns, which should be remembered when buying material. So, paper for rough work with a grain size of 800-1000 microns according to the ISO-6344 standard is designated P22, and according to GOST 3647-80 - 80-N. Sanding paper with a grain size of 3-5 microns according to the ISO-6344 standard is designated P2500, according to GOST 3647-80 - M5 \\ H-00 (hence the expression "zero"). Sanding paper of medium grain size (125-160 microns) is designated P100 (ISO-6344) and 16-H (GOST 3647-80).

Sandpaper marking: a few words about the important

If the material is sheet, the letter L will be the first in the marking. Next, the type of base is indicated (1 - for working with materials of low hardness, 2 - for grinding metals). The letter E or M means that the abrasive was applied electrostatically or mechanically. The following numbers represent the dimensions of the sheet or roll media.

Everything that follows in the marking is directly related to the field of application of the abrasive. So, as a basis can be used:

standard paper or semi-duplex fabric (P);
moisture resistant paper (L or M);
twill (C or Y).

The most widely used abrasive paper with electrocorundum abrasives of several types:

normal (15A);
white (24A, 25A);
monocorundum (43, 45A).

The next in the marking indicates the size of the main fraction of the abrasive, as well as its content in the finished material. Next, the type of binder is indicated:

M (skin glue);
C (synthetic glue);
K (composite adhesive);
SFK (formaldehyde resin);
YAN-15 (amber varnish).

The last symbol of the marking is an indicator of the wear resistance of emery, which is indicated by letters:

AND -<0,5 %;
B -< 2 %;
IN -<3 %.

Types and properties of bases

The sandpaper can have a paper and / or fabric backing. The advantages of the first are the low price, the possibility of applying fine abrasives and the absence of stretching during operation. Fabric-based paper consists of polyester and cotton, impregnated with a special resin that increases the strength and water resistance of the material. The disadvantages of this type of emery are low tensile strength and higher cost compared to paper-based abrasives.

For the production of certain categories of abrasives, combined bases and fibers are used. The latter is notable for its hardness, has a high density, but is not moisture resistant, which significantly limits its scope.

Classification by filling method and application

The abrasive is applied by the following methods:

open and half-open (the abrasive covers 40-60% of the base);
closed (abrasive grains cover the entire base area).

Sandpaper with open and semi-open filling is used for processing loose and soft (putty, wood, fibrous, etc.) surfaces. Closed fill is more effective when sanding metals, hard wood and plastics.

It is possible to work with abrasive paper both manually and using machines - vibration, surface grinding, eccentric, belt, etc. Currently, in addition to traditional sheets and rolls, abrasive paper can be presented in the form of various devices designed to perform specific operations.

In conclusion, it is worth recalling that the main criterion when choosing emery is by no means the price, but such characteristics as the grain size and type of base indicated in the marking.

Sandpaper (sandpaper) is an abrasive material that is designed to sand and remove irregularities / notches from the surface.

There are many types of sandpaper and they can be classified according to various parameters, such as base material, application of the abrasive layer and grit size.

Classification by numbers (grain size)

Today, sandpaper is available in grit sizes from 12 to 4000.

Grit is the number of abrasive particles per square inch of sandpaper. The lower the number, the coarser (coarser grains) the sandpaper.

It can be conditionally divided into 3 groups:

Coarse-grained (12-80).It is most often used to remove various varnishes and paints from the surface, that is, it is used for primary processing. This rough sanding usually leaves scratches that need to be sanded with finer sandpaper.
Medium grit (80-160) sandpaper, usually used after coarse grit to smooth and smooth wood surfaces. Such paper leaves few traces and is used for intermediate processing of the material.
Fine-grained (160-4000). Fine-grained sandpaper allows you to completely remove all unevenness and scratches from the surface of the wood. Used as a finishing treatment just before painting.

Sandpaper base

Paper base. Paper-based abrasive paper is the cheapest, it can withstand heavy mechanical stress and can be treated with a water-repellent substance. Even the smallest fractions of the grinding material can be applied to such a base, but its wear resistance leaves much to be desired.
Fabric base. Cloth-based abrasive paper has good wear resistance and can be impregnated with special resins to protect it from moisture. It also has good elasticity and tear resistance.
Combined base. Sandpaper on a combined basis (paper + cloth) is used in cases where a sanding surface with a high level of grit is required under high mechanical stress. Such paper has collected all the best properties of the previous types and is the most expensive.

In addition to the grain size and base material, we also recommend paying attention to the abrasive filling.

For example, solid sandpaper has a higher strength and is suitable for processing solids.

Semi-open abrasive products are designed for softer materials and will clean better with use.

We hope that this classification of sandpaper was useful to you and you chose it correctly!

Sandpaper is the most common material for sanding various surfaces. There are many types and brands of it. Without understanding them, you run the risk of damaging the sanding material or the abrasive itself - this happened to me once at the dawn of my foggy youth.

What is sandpaper?

Sandpaper is a flexible grinding material... It is also called abrasive paper, emery cloth, or simply sandpaper. It is made of a paper or fabric base and a layer of abrasive grains glued to it.

Sandpaper is intended for processing surfaces made of concrete, wood, brick, metal, plastic, glass and other surfaces. With its help you can:

remove old coatings (eg varnish) and their residues;
prepare bases for priming and painting;
remove chips and burrs from sections of different materials;
level, grind, polish surfaces.

Abrasives for the production of sandpaper

Natural emery is a mixture of magnetite and corundum. Now it is practically not used in the production of abrasives.

Carborundum (silicon carbide) and electrocorundum (aluminum oxide) - most often used for the production of abrasive skins. They get them artificially.
Borazon (elbor), syntheticdiamond and pomegranate are used less often.

Electrocorundum

Aluminum oxide is the most common abrasive. These are hard crystals with sharp edges at the fracture:

Electrocorundum is synthesized by reducing the melting of the charge in an arc furnace. The raw material consists of iron filings, bauxite agglomerate and low ash carbonaceous materials.
Aluminum oxide has excellent cutting ability. It can withstand high pressure.
Alloying additives are often added to the charge during melting. They improve the performance of fused alumina. So, chromium oxide increases the strength and abrasive qualities of the material. Aluminum oxide can be identified by its ruby \u200b\u200btone.

Carborundum

Silicon carbide is produced by sintering graphite and silica in an Acheson electric furnace. These are crystals of various shapes, the edges of which are very sharp.
Carborundum is harder than fused alumina... But his fragility is higher.
The pressure during grinding breaks the crystals. This creates new cutting edges. This feature of carborundum keeps the sandpaper working for a long time and prevents clogging of the abrasive layer.

Silicon carbide abrasive paper is best suited for sanding plastics and glass. It can also be used for metal.

Elbor and artificial diamond

Diamond has the highest hardness of all known substances... Elbor is slightly inferior to him in hardness, 3 times higher than carborundum and 4 times higher than electrocorundum. But Elbor surpasses diamond in temperature resistance.

The disadvantage of these abrasives is their high price.... Therefore, they are rarely used to make emery cloth.

Garnet

Pomegranate is a relatively soft mineral... Its hardness on the Mohs scale is 6.4-7.5 units. Therefore, garnet abrasive is used for processing soft substrates and materials. In most cases, this is wood.

Lack of pomegranate skin - fast wear.

Dignity - the abrasive layer has the same grain size. Therefore, this sandpaper sands more smoothly than materials with other abrasives.

Sandpaper classification

The most important characteristic of the abrasive paper - grain... The purpose of the sandpaper can be different:

polishing,
grinding,
rough preliminary stripping.

Based on it, the grain diameter can vary from 3 microns - for fine polishing, up to 1 mm - for the roughest work.

The grain size of the emery cloth is regulated by the international standard ISO No. 6344 (FEPA). Its analogue in the Russian Federation is GOST R No. 52381/2005, adopted in 2005.

According to these documents, the grain size of the material is indicated by the letter P and the number from 2500 to 12. The higher the number, the smaller the grain diameter. The number itself indicates the number of wires per inch of the sieve.

In the CIS countries, the Soviet GOST No. 3647/80 is still used:

According to it, the number indicates the minimum grain diameter in microns. After it is put the letter N.
On a fine skin, first put the letter M, then there is a number indicating the size of the grains in microns.

Some of the countries have different standards:

In Canada and the USA - American National Standards Institute (ANSI);
In China - GB-2478;
In Japan - Japanese Industrial Standard (JIS).

Sanding paper grades by grain size

Sandpaper is marked with two alphanumeric groups... They are printed with ink on the back of a roll or sheet. The first of them speaks about the granularity of the material. Types of sandpaper for this feature are presented in the tables.

Coarse paper

Coarse skin is intended for rough work.

Coarse emery cloth
Purpose	Marking according to ISO No. 6344		Grain diameter in micrometers
The roughest job	P-22	80-N	1000-800
	P-24	63-N	800-630
	P-36	50-N	630-500
Rough work	P-40	40-N	500-400
	P-46	32-H	400-315
	P-60	25-N	315-250
Primary grinding	P-80	20-N	250-200
	P-90	16-H	200-160
	P-100	12-H	160-125
	P-120	10-H	125-100
Final sanding of soft woods, old paint coat before painting	R-150	8-H	100-80
	P-180	6-H	80-63

Fine-grained skin

The finer sandpaper is for fine work.

Fine-grained emery cloth
Purpose	Marking according to ISO No. 6344	Marking in accordance with GOST No. 3647/80	Grain diameter in micrometers
Finishing sanding of hard woods, sanding between coats	R-240 5	M-63 and 5-N	63-50
Finishing sanding of hard woods, sanding between coats	P-280	M-50 and 4-N	50-40
Finish polishing, sanding between paint coats, wet sanding	P-400	M-40 and 3-N	40-28
	P-600	M-28 and 2-N	28-20
Sanding of plastic, metal and ceramic, wet sanding	P-1000	M-20 and 1-N	20-14
The finest polishing and grinding	P-1200	M-14	14-10
	P-1500	M-10 and 0-N	10-7
	P-2000	M-7 and 01-N	7-5
	R-2500	M-5 and 00-N	5-3

Skin marking according to the state standard

The second marking indicates all the data about the sandpaper... It can be printed with ink or located on a product label. Let me give you an example: L2E600 × 40P125A25-L1MA GOST No. 13344/79. I will decipher:

The first letter L means that the sandpaper is sheet. Roll material is not indicated in any way.
Number 2 indicates the type of paper. In our case, it is intended for metal grinding. The number 1 would mean that the skin is used for processing materials with a low hardness.
The letter E indicates that the abrasive was applied electrostatically. Letter M would mean a mechanical way.
600 × 40 are the dimensions of the sheet, its width and length in millimeters. For rolled skin, its width is indicated in millimeters, and its length in meters.
The alphanumeric group L1 indicates the basis of the material. In our case, it is moisture-resistant paper.
P2 marking is a 0-200 paper base.
Moisture-resistant paper is designated M, L1 and L2.
The paper not resistant to water is marked with P1 and P11.
The twill fabric base is designated S2G, S1G, C1, U2G, U1G, U2 and U1.
Semi-bunny fabric is marked with the letter P.
Alphanumeric group 25A indicates the type and brand of abrasive. In our case, it is white fused corundum. It can also be referred to as 24A.
Marking 15A indicates normal fused alumina.
45A and 43A are mono corundum.
55C, 54C and 53C - black carborundum.
62C, 63C and 62C - green silicon carbide.
81Kr - flint.
71St indicates glass abrasive.

The number 25 indicates the grain diameter of the main fraction of the abrasive in micrometers.

Fine-grained skin is marked in this part with an alphanumeric group from M3 to M63.

-H indicates the content of the main fraction of the abrasive. In our case, this is 55 percent.
The letter B will indicate 60%.
Letter D - by 41%.
Letter H - 45%.
The next letter tells about the composition of the abrasive material glued. In my example, this is M. So, skin glue was used.
The letter C will indicate a synthetic compound.
K means a combined mixture of skin and synthetic glue.
YAN-15 indicates amber varnish.
SFC stands for phenol-formaldehyde resin.
The last letter shows the wear resistance class of the skin in relation to the presence of defects. In my example, this is class A - less than 0.5% of the defective material surface.
The letter B means less than 2%.
Letter B says less than 3% defects on paper.
GOST No. 13344/79 indicates the standard by which the material is made. Waterproof sandpaper is made on it. The material not resistant to water is produced in accordance with GOST №6456/82.

Classification by abrasive distribution method

Semi-open and open fill... With this distribution method, the abrasive covers 60 to 40% of the substrate. Such a filling excludes filling the gaps between the grains with grinding waste. No lumps form on the skin.

Sandpaper with open and semi-open grit is ideal for sanding soft and loose materials. For example, resinous types of wood, putty surfaces.

Continuous (closed) backfill... With this method, the abrasive is applied to the entire substrate. This sandpaper is ideal for sanding hard materials. For example, hard wood, metals.

Emery cloth base materials

The type of emery cloth depends on the material of its base.

Paper base

The abrasive paper should be as strong as possible. So it will withstand mechanical stress longer. Paper is classified based on its density in grams per square meter. This classification is adopted according to ISO # 6344. Marking is carried out in letters.

The paper can be plain and moisture resistant. The glue used for the abrasive can also increase its water resistance.

Pros:

low cost;
when grinding, it does not lengthen;
the surface of the paper makes it possible to apply the smallest grains of abrasive to it.

Minuses:

low strength;
low wear resistance.

Fabric base

In the form of a base for sandpaper, polyester or cotton are most often used. They are impregnated with polyester resins. The impregnation gives the material moisture resistance and increases its strength.

Tear strength and elasticity - these are the main characteristics of fabric bases. According to these parameters, they are divided into four classes:

Group J fabrics - used for finishing profiles and edges.
Class X - used for heavy and dirty work.
Fabrics of groups Y and W - are used if maximum strength of the abrasive material is required. For example, in industrial sanding of cladding panels.

When choosing a skin on a fabric basis, prefer it as hard as possible - such as the forthcoming grinding and the shape of the surface to be sanded will allow. The durability of the abrasive material depends on the rigidity of the base.
Grinding discs are most often made on a fiber base.
The fiber base is intended for the production of grinding wheels. It is produced by treating cellulose with zinc chloride. The result is a dense and hard material.
Lack of fiber - it is non-moisture resistant, as it strongly absorbs water.
Sandpaper production
In the production of sandpaper, two methods of applying abrasive material are used.
Abrasive Grain Application Methods
Electrostatic method. The negatively charged abrasive material is attracted in an electrostatic field to the adhesive layer applied to the substrate. The field forces the particles into the binder. The grains are placed vertically and point downwards.

The advantage of the method - the abrasive layer created by electrostatic means is more aggressive. It makes it possible to grind more material (compared to a mechanically created abrasive layer) with the same physical effort.
Mechanical method. Abrasive particles under the influence of gravity fall on the adhesive layer applied to the substrate. They are arranged in random order.

Lack of method - the abrasive layer created by mechanical means is less aggressive.
Adhesives
For the production of abrasive skins, synthetic and natural adhesives of various brands are used. The type of binder affects the strength and usage patterns of the sandpaper.
The main tasks of the glue - hold the abrasive on the substrate and remove heat from it during grinding. The fixing strength of the grains in the adhesive layer should be greater than the strength of the particles themselves.
The type of glue determines the elasticity and rigidity of the sanding paper and, to some extent, moisture resistance. Manufacturers often add special additives to the binder. They give the material certain qualities. For example, anti-grease, anti-static properties.
Epoxy, urea-formaldehyde and phenol-formaldehyde resins, as well as amber varnishare the most common types of synthetic adhesives.

Skin glue - the most commonly used natural composition. The skin made with it is not waterproof. Therefore not suitable for wet work.

Features of using the material
When sanding surfaces, follow the universal rule: you need to start processing with a coarser sandpaper. Gradually change it to sandpaper with a thinner abrasive layer.

Very coarse and coarse abrasive It is used for pre-treatment of wood, removing the old paint layer and corrosion centers from metal.

Very thin and thin skin it is used for various stages of surface finishing and polishing.

For plastic Carborundum-coated abrasive is best.

For wet processing you need to use a waterproof type of sandpaper with an abrasive layer P-600 / P-400. Sanding in an aqueous medium makes it possible to achieve a smoother surface and suppresses dust formation.

For manual processing of volumetric surfaces of complex and curved shapes, it is most convenient to fix the sandpaper on a thick piece of soft rubber.
Small instruction:
To work with the sanding paper more comfortably, wrap it around the stone. It can be made of any suitable material - foam, plastic or wood;

Pre-glue or nail a piece of foam rubber or felt to the bar.

With such a simple device, the quality of your work will increase. You can control the sanding pressure and increase productivity.
Machine application
Sandpaper serves as a consumable for such devices:
Surface Grinder (Vibration Grinder) Machine... On its working part, rectangular sheets of skin are fixed with Velcro or in clamps. The device may have a dust collector outlet.

Delta Grinder... Its triangular shape resembles the Greek letter Δ (delta). The device makes it possible to grind surfaces in hard-to-reach areas. On it, sheets of sandpaper in the form of a triangle are fixed with Velcro. The device is equipped with a dust collector outlet.

Orbital (eccentric) grinder... On it, the skin in the form of a circle is fixed with Velcro. The machine has a dust collector outlet.

Angle grinder (grinder) and electric drill with additional attachment... The emery discs on the backing pad are fixed with Velcro. Or have a hole in the center for a clamping washer. This tool does not have a dust collector outlet.

Universal Vibration Cutter... On its support platform, the triangular sheets of sanding paper are fixed with Velcro. The machine does not have a dust collector outlet.

Belt sander... The roll skin cuts are fixed on the roller and the drive shaft of the fixture. The device does not have a dust collector outlet.

Conclusion
Sandpaper is the optimal material for sanding work. To make the surface treatment effective and efficient, choose the most suitable sandpaper for your case - I told about the types and features of sandpaper.
The video in this article will continue to introduce you to the topic. If you still have questions, ask them in the comments.