Sanding grit sanding table. Sandpaper - types. Marking waterproof sandpaper

Sandpaper is an abrasive material that is used for grinding or removing various irregularities and other elements on a certain surface. In this article we will talk about what kind of sandpaper is, what type of sandpaper is intended for which cases, and everything else that can be somehow connected with it.

Classification of sandpaper by number (grit)

The most popular way to classify all sandpaper is by number. Paper can have a number ranging from 12 to 4000 - and that's what these numbers say. In fact, it is logical that the numbers are put for a reason. This number indicates how many abrasive particles are contained in one square inch of sandpaper. The smaller this figure, that is, closer to 12, the coarser the sandpaper will be - large grains will be present in it. Accordingly, on the contrary - the closer the number is to four thousand, the sandpaper will be fine-grained, and it will feel very soft.

Now, we can conditionally divide all sandpaper into about 3 categories:

- uh then coarse-grained sandpaper, ranging in size from 12-80;

- n sandpaper of medium grit, size from 80-160;

- n fine grit sandpaper, the size of which is from 160-4000.

So, coarse-grained sandpaper is used to remove some layers, such as varnish or paint, and is also used when primary processing. That is, if you need, for example, to remove a layer 5 mm thick from the board, first of all, you need to use coarse, coarse-grained sandpaper to remove about 4-4.5 mm of the layer. After processing with this paper, scratches will be left on the surface of the workpiece.

Next, to make the surface smoother, you need to use medium grit sandpaper. With its help, you can smooth or level the surface, and after using this paper, very few traces of any kind remain on the surface of the material. That is, medium grain paper is used to perform intermediate processing.

And, fine-grained sandpaper will help remove and smooth out all the scratches on the surface of the workpiece - with its help, final processing is carried out, followed by varnishing, painting, and so on.

Sandpaper materials

Now let's talk about what sandpaper is made of, and since it is a combined building material (or a tool, if you can call it that), it is worth noting all the components that make up its composition.

First of all, this is the basis of sandpaper. Often, the basis is just the same paper. It is very cheap, moderately strong and can withstand significant mechanical stress. It can be treated with almost any water-repellent agent, and even very small fractions of the material can be applied to such a base, but wear resistance in this case will only wish for the best.

Also, sandpaper can be fabric basis. Such a material will have a high degree of wear resistance, and will also be impregnated with various resins to make it waterproof. In addition, unlike the paper base, the fabric will have an excellent degree of elasticity, as well as tear strength.

And, there is a combined sandpaper. In this case, the basis is a combined layer consisting of both fabric and paper. Such sandpaper is used in cases where it needs to endure large mechanical loads. This type of sandpaper combines all the advantages of the previous two types, so it is the most expensive of all.

Now, a few words about the abrasive paper itself. So, you need to pay attention to the degree of abrasive coating - it can be a solid coating with high strength, which is suitable for processing solids, or paper with a semi-open coating of abrasive, which is intended for soft materials.

Abrasive materials

And, of course, now about what materials abrasives are made of. So, there are several types of abrasive, which is used for application to the emery base. So let's take a look at each type.

Electrocorundum. This is the most popular and used type of abrasive, which is obtained as a result of reduction melting in an arc furnace of a charge that consists of bauxite agglomerate, as well as iron chips and a special low-ash carbonaceous material. This material can withstand high pressure and also has a high cutting ability. By appearance very similar to crystals that have sharp edges at a break. Also, alloying melts can be added to electrocorundum, which can, to one degree or another, improve the properties of sandpaper.

Silicon carbide. This abrasive is obtained as a result of sintering krenezem and graphite, in a special Acheson electric furnace. So, this material consists of small shiny crystals that do not have a standard shape, and have very sharp edges. Silicon carbide has a much greater hardness than aluminum oxide, but is somewhat brittle. When pressure occurs, the crystals disintegrate, forming more cutting edges, therefore given property silicon carbide, allows it to be used effectively in sandpaper.

Pomegranate. An abrasive is also made from this material. It is a very soft mineral, which, when polished, is divided into a large number of small particles that, interacting with each other, do their job - they grind the workpiece.

Diamond. Sandpaper from this abrasive is the most expensive, it is clear for what reasons. At the same time, this material is very durable, so this sandpaper is very durable and effective. But, due to the high cost, it is rarely used.

Or mechanical grinding, right choice abrasive - important factor, which determines the quality of processing wooden surface. This seemingly simple task raises many questions. What sanding to use on various stages grinding? How to understand the marking when choosing the right abrasive? What properties do they have different types skins? For all these and others no less important questions we will answer in the submitted material.

Anatomy of an emery sheet

Sandpaper or a grinding wheel for a grinder consists of three main components: abrasive material, backing and binder.

abrasive material - a substance ground to the state of fine grains. Used to make sandpaper Various types abrasives: aluminum oxide (electrocorundum), silicon carbide, garnet, glass, elbor, etc. The size of the abrasive particles determines the most important characteristic of the abrasive skin - its grain size, which we will talk about in more detail.

Substrate - a paper or fabric base on which the abrasive material is glued. The fabric is more often used for tapes, rolls and some types of grinding discs. Paper is commonly used for sandpaper and most discs. Along with paper and fabric substrates, you can find options from polyester materials.

Binder - a layer of adhesive that holds abrasive grains. As a binder, hide glue, synthetic resin (more durable option) or a combination of these two materials is used.

Understanding the types of coverage

For various works with wood: its roughing, preparation for finishing, interlayer grinding of coatings, polishing, etc., are traditionally used the following types abrasives.

Aluminum oxide (electrocorundum) . Differs in the high density and resistance to crushing. The most common abrasive for grinding wood and metal. Recommended for sanding raw wood.

Silicon carbide . During operation, the crystals of this abrasive break, forming new cutting edges. This feature of the grains ensures self-sharpening of the skin and prevents its rapid clogging. Silicon carbide coated sandpaper is recommended for delicate sanding, such as sanding between coats of finishes.

Pomegranate . Relatively soft mineral abrasive. It has the ability to self-sharpen, but wears out quickly. It is traditionally used for the final sanding of treated and untreated wood.

Alumina ceramics . This is aluminum oxide that has undergone additional high-temperature processing. Its abrasive properties are higher than those of its unfired counterpart. Differs in the maximum wear resistance, it is optimum for processing of a tree at various stages.

How not to make a mistake with graininess?

Grit - the most important characteristic sanding skin. When the hackneyed question sounds: what kind of sandpaper to grind a tree, they usually mean not so much the type of its coating, the nature of the binder, etc., but the graininess index.

The suitability of sandpaper for a particular type of work depends on the gradation of grit. At first glance, everything seems simple, but in practice, choosing the right skin is often complicated by confusion in marking by numbers.

It so happened that several sandpaper standards are in active use on the modern market at once: the international classification ISO 6344 (it fully complies with the new Russian GOST R 52381-2005), the old Soviet marking (GOST 3647-80) and the American standard (CAMI).

TABLE: TYPES OF GRIT OF SANDPAPER, PURPOSE OF ABRASIVE, RATIO OF MARKINGS

What is open and closed abrasive coating?

Based on the characteristics of the application of the abrasive material, there are skins with open and closed filling. It's another one important parameter, which is worth paying attention to when choosing sandpaper for working with wood.

In open and semi-open sandpaper, abrasive grains cover from 40 to 60% of the working surface. The sparse filling of grains prevents the rapid clogging of the abrasive wood chips, resin, paint and other waste. Such sandpaper is optimal for machine sanding, processing wood for painting, working with soft and resinous wood species.

In sandpaper with a closed or solid coating, abrasive grains cover the entire working surface. Such a skin is more effective for manual grinding, working with hardwoods, and finishing polishing.

How to extend the life of an abrasive?

As chips are clogged and tree resin, as well as wear of abrasive grains, sandpaper loses its working properties. Clogged abrasive, especially when machine grinding, leaves dark footprints, compresses the fibers and polishes the surface, which is why the wood does not absorb the finishing composition well.

To make abrasives last longer, start with a coarser sandpaper, gradually moving to a paper with a finer grit. For soft and resinous woods, use sanding paper with a sparse coating and a special stearate coating (a dry lubricant that prevents the abrasive from clogging quickly).

When working with a grinder - do not rush. Overheating of the surface leads to softening of the binder and accelerates the wear of abrasive grains. An important factor is the storage conditions of the grinding material. Cold and critical humidity can make it unusable. Optimum temperature storage 15-25°C at a relative humidity of 35-50%.

All of the above cleaning methods are more relevant for grinding abrasives. To clean ordinary skins, you can use a brush with hard plastic bristles.

In production related to the processing of wood, plastic, metal, glass, sandpaper is indispensable. It is indispensable when removing old paint, there is no alternative to it if you need to prepare the surface for priming and painting, etc.

The ancient Chinese in the 13th century used a starch-based adhesive to stick plant seeds, finely ground sand, and shells onto parchment.

The prototype of sanding paper is considered to be " sandpaper”, because for its manufacture used the smallest particles of glass.

In 1834, the American engineer A. Fisher Jr. first patented the production of emery cloth, where silicon carbide and corundum were already abrasive grains.

You should know that the graininess of sandpaper is one of its main characteristics.

Conventionally, the paper was divided into groups: coarse-grained, medium-grained and fine-grained paper.

The grain size determines the type of work for which sandpaper is intended. Marking will help you choose it.

Emery carry out work on dry and wet processing of all kinds of puttied surfaces.

For various, sandpaper differing in grain and base is used. The marking of such paper is specific.

Sanding grit

H - marking of domestic products (old).

P - marking of imported products and new marking domestic products.

Manufacturers producing products for export use a single world standard for designating grain size.

In some states of the collapsed Union, sandpaper, marking of emery production is carried out in accordance with GOST (old).

The same is happening in Canada, China, the US and Japan, where the domestic market uses its own designations.

The European standard (new GOST) implies an increase in values ​​as the grain size decreases. Sandpaper is marked in a completely different way in the above countries.

GOST, for example, is designed in such a way that the values ​​here, on the contrary, decrease as the grain size decreases.

These differences cannot be ignored when buying abrasive products on the territory of the countries of the former Soviet Union, because. this difference may lead to the purchase of an unsuitable product.

It should be noted that imported paper is most often sold in products, while domestic paper is sold in rolls, and it is sold by linear meters.

If paper is used in everyday life, then remembering the marking is not necessary. You just need to know that the old marking comes with the letter H after the number, and the new one with the letter P before the number.

On reverse side paper has other designations. They can be installed additional information about sandpaper: its basis, abrasive technology, grain material, type of binder, etc.

Now you know what Marking is? You got it right with her too. It remains to wish everyone a pleasant and fruitful work.

The operations to create a smooth surface are called grinding (roughing) and polishing (finishing). They are carried out by means of abrasive materials - sandpaper or grinding cloth.

Material Description

Sandpaper, colloquially, "sandpaper", is a flexible substrate with powdered cutting material applied. The latter is sand of artificial origin of various fractions.

It is used for preliminary and finishing finishing of blanks and parts made of wood, metal, polymeric substance, glass and other materials. It is applied at manual or machine operations.

Types of sandpaper

One of the main divisions by type of sandpaper is an elastic base:

1. Paper.

   The base must be of a certain density, withstand external loads, and have adhesion to adhesive compositions for attaching the abrasive. It has a number of advantages:

   • low cost;
   • availability of raw materials (wood) or recyclables;
   • low coefficient of elongation (compression);
   • thanks to a continuous surface, allows to apply the smallest fractions of an abrasive powder.

   But, it is not without drawbacks:

   • low strength under mechanical action;
   • low wear resistance;
   • is destroyed by water (except for materials for manual labor).
2. Textile.

   Cotton and polyester are used as the base. In order to increase strength, the fabric is treated with resins. The main indicators are flexibility (elasticity) and breaking force. They are divided into classes according to rigidity:

   • class J - finishing the edges of the workpiece and profile products (with complex geometric shape);
   • class X - rough initial grinding process;
   • class W or Y - the base has increased strength.

   Advantages:

   • high tensile strength;
   • increased wear resistance;
   • base flexibility;
   • water resistance;
   • the ability to produce abrasive material on a fabric basis in the form of endless tapes;
   • high adhesion to glue (due to the structure of the fabric).
   • increased cost compared to paper;
   • elongation of the base in the process.

In relation to water it is subdivided:

• non-water resistant (the adhesive composition is destroyed);
• waterproof (paper base in this case is used for manual labor).

Grain

The most important characteristic of sandpaper, which is responsible for cutting properties, is graininess. The indicator indicates the size of the abrasive grain. For example, a fraction of 0.8~1mm is used for preliminary operations. Finishing, indicators do not exceed 3~6 microns.

The volumetric value of the abrasive material is regulated according to the world standard ICO 6344. GOST 52381-2005 is in force in the Russian Federation. According to the requirements, sandpaper numbers are indicated by the letter P with digital support 12-2500. The indicator corresponds to the number of wires per 25.4 mm (English inch). That is, the more cells per inch, the smaller the grain size at the output during calibration.

On the territory of the country there is an old designation, from the time of the USSR, according to GOST 3647-80. Grain size is indicated in microns. The smallest value for the group is accepted, for example, 16-H, 8-H. In the fine-grained category, the letter M is used. "Nulyovka" is one of the smallest sandpaper (M40), popular with motorists.

Application and grit:

Sandpaper is classified by grit. This is necessary for correct compilation technological process and drawing up the stages of operations.

Abrasive

Since ancient times, quartz sand and natural glass have been used as a grinding material, - volcanic obsidian. Small particles stuck to the skin. Hence, another popular name is sandpaper.

Modern abrasive:

1. Electrocorundum. artificial material, which is based on Al2O3 (aluminum oxide). It has sharp and hard edges. Possesses the high cutting ability. To improve technological performance, the substance is alloyed various additives, which can be recognized by color:
   • White, - the content of aluminum oxide is within 99%.
   • Ruby shade, - chromium oxide introduced.
   • Gray-blue gamma - saturation with titanium oxide.
   • Shades of brown, normal electrocorundum with 91~96% Al2O3 content.
   • Brick red - indicates the presence of zircon additives.
2. Silicon carbide. Substance black. Chemical formula SiC. Possesses the increased hardness, in comparison with aluminum oxide. But more fragile. In the process of exposure to mechanical loads, it breaks. New abrasive particles are created. This process contributes to the "self-cleaning" of the structure of the abrasive tool from sludge. It is used on glass, ceramics, plastics and for finishing metal grinding.

Less common substances - diamond, elbor, garnet and others are less commonly used due to high cost and low availability.

Documentation

Grinding and polishing materials on a paper-like carrier or a wicker base are produced in the light of the requirements of regulatory documents:

• GOST 6456-82 Grinding paper skin.
• GOST 13344-79 Sanding cloth waterproof.
• GOST 5009-82 Grinding paper and cloth and other documents.

Describes the rules for the manufacture, granularity, application. The decoding of the marking (designation) of sandpaper is given.

Designation, name

For correct application grinding material, you need to know about its properties and purpose. To this end, on wrong side indelible paintwork is printed with an inscription that contains information about the abrasive.

Designation according to GOST: L2E700×110S1G15A25-NMA GOST 13344-79 514, where

• Structural type of abrasive material:
  • L - in sheets; for rolled, the abbreviation is not put.
• Media type:
  • number 1 - processing of workpieces with low hardness;
  • number 2 - metal grinding.
• Polyrite attachment:
  • E - electrostatic method.
• Overall dimensions of the product:
  • sheet, - width × length in mm;
  • roll, - width × length in m.
• Carrier:
  • paper 0-200;
  • L1, L2, M - moisture resistant paper;
  • P1-P11 - non-moisture resistant paper;
  • S1, S1G, S2G, U1, U2, U1G - twill fabric;
  • P - semi-double fabric.
• Abrasive brand:
  • 15A - normal electrocorundum;
  • 24A, 25A - white electrocorundum;
  • 43A, 45A - monocorundum;
  • 53С, 54С, 55С - black silicon carbide;
  • 62С, 63С - green silicon carbide;
  • 71St - glass;
  • 81Kr - flint.
• Grinding grain fraction:
  • 25 - grain size in microns;
  • M63-M3, - micro grinding, size in microns.
• The amount of mass composition of the abrasive grain:
  • B ≥ 60%;
  • P ≥ 55%;
  • H ≥ 45%;
  • D ≥ 41%.
• Type of binder:
  • M - skin glue;
  • C - synthetic binder;
  • K - composite binder (M + C);
  • SFC - adhesive composition based on phenol-formaldehyde resin;
  • YAN-15, - varnish from amber resin.
• Abrasion (defects):
  • A ≤ 0.5%;
  • B ≤ 2%;
  • B ≤ 3%.
• Regulatory document:
  • GOST 6456-82, nominal value, non-waterproof base type;
  • GOST 13344-79, waterproof fabric.
• Factory marking:
  • 514 - designation party;
  • It may not be displayed.

1. The use of a coarse abrasive allows you to remove a fairly thick layer of the material being processed, but at the same time, distinct grooves form on the surface.
2. An expedient grinding sequence is from coarse grit to fine grit.
3. In the absence of the necessary fine fraction, it can be obtained by rubbing sheets with larger grains against each other.
4. For lapping operations of two adjacent surfaces, grinding powder can be obtained by soaking non-moisture-resistant sandpaper in warm water.
5. Ensuring the flatness of the treated surface is achieved by attaching the sandpaper to a hard, durable surface.
6. A curved surface is more convenient to grind with paper attached to a thick piece of soft rubber.
7. The size of the cut (ground) layer of material directly depends on the efforts applied to the tool.

This abrasive in everyday life is better known as a skin. That sandpaper can be used for surface finishing various materials- from plastics and wood to metals - everyone knows. But to the question, what is the specifics of the application, depending on the marking of the sandpaper, not many will be able to answer correctly.

For those who want to learn more about specifications on sandpaper, the search for an appropriate standard causes certain difficulties. There are several GOSTs - No. 6456 of 1982 (for paper skins), No. 5009, dated the same year (for sandpaper on paper and fabric basis) and No. 52381 of 2005 (concerning the graininess of products). Often there are references to another Soviet standard - No. 3647 of 1980.

• Russian GOST (the letter P is present in the marking of sandpaper) fully complies with foreign standards, which are prescribed in the ISO 6344 standard (generally accepted).
• Some manufacturers of neighboring countries are also guided by the GOST of the times of the USSR - in the marking of the letter H or M (for skins with small grains).
• Some countries have their own standards, and sandpaper has its own markings. As an example - Japan, USA, Canada, China.

Further, in order not to repeat myself, the author will indicate the marking of paper, depending on its purpose, both in Russian and Soviet (in brackets) symbols. There are no big differences in the definition of the "grain" of the skin, and, accordingly, the specifics of its use, and a more detailed consideration of all the features of the product varieties is of interest only to a specialized specialist. In terms of domestic use, they do not play any role.

Sandpaper marking and scope

Coarse sandpaper

• P22 - 36 (H50 - 80) - for primary (preliminary) processing of parts. For example, removing a layer of rust, removing scale and the like. Therefore, the purpose is preparation for further work with the material.
• P40 - 60 (H25 - 40). Sandpaper with a similar marking is used for rough surface treatment - cleaning, leveling, removing dirt in certain areas, and so on.
• P80 - 120 (H10 - 20). Purpose - precise processing. It is often referred to as pre-sanding. In some cases, this is enough to apply any coating or pasting the surface.
• P150 - 180 (H6 - 8). Such sandpaper is used for final alignment (grinding) when extreme accuracy is not required.

Fine-grained sandpaper

• P240 - 280 (M63, H5) - metals and hard wood.
• P1000 (H1, M20) - plastics, ceramics, soft metals.

Polishing

• P400 - 600 (H2 - 3, M28 - 40). The main purpose is to prepare the surface for applying varnishes or paints.
• P1200 - 2500 (M5 - 14, H0 - 00 - 01). Such sandpaper is called "velvet". It is intended for the most delicate operations, when it is required to “finish” the part after all previous treatments.

As already noted, the skin has different basis. What is the difference?

Sandpaper paper

Pros:

• Does not "stretch" during use.
• On such a basis, the smallest grain can be applied. Sandpaper fabric "for polishing" is almost never found.
• Low cost.

Minuses:

• Insufficient strength, therefore, fragility. The main purpose is for manual processing of materials.
• Increased moisture absorption. It is used for cleaning, polishing only dry surfaces.

Sandpaper fabric

Pros:

• Tear strength combined with some elasticity. The main purpose of this product is the processing of parts mechanically, for example with .
• Minimum moisture absorption.

Minus:

• The price is higher than paper counterparts.

All types of sandpaper vary in grit density. This feature also determines the main purpose of the skin.

• Solid backfill - for working with solid samples (metals, dense wood, ebonite, and so on).
• Open (semi-open) - for stripping, grinding relatively soft materials with a porous structure. It is also used in the treatment of surfaces on which putty, paint were previously applied, as well as softwood, plastics and in a number of other cases.

If necessary, finish grinding the part (finishing it to a marketable condition) instead of fine-grained sandpaper, it is advisable to use ordinary, rough. Alternatively, a wrapper. The effect is the same.

Particular care must be taken when stripping copper contact groups. For example, lamellas of collectors of electric motors. In this case, only the "glass" skin is used. All other types of sandpaper increase the wear of carbon brushes, as they leave the smallest abrasive fractions (dust) on the copper surface.

Additional product information, including its purpose, can be found at reverse side sample. The letters are affixed in a variety of ways, but the most common ones should be indicated.

• M, L1 (or 2) - moisture resistant sandpaper.
• 1 - for porous (soft) materials.
• 2 - for grinding parts made of hard alloys, metals or dense wood.
• P - only for dry surfaces (increased absorption of moisture).
• L - sheet sandpaper. The rolled skin has no designation.

When choosing sandpaper for marking, it is necessary to take into account local specifics - the material of the part, the degree of contamination (rust), humidity, whether there was pre-treatment (for example, paint) and a number of other nuances. Only in this case can a rational purchase be made.