Types of sandpaper, its marking and production

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There are also sanding sponges. This is an abrasive that is applied to polyurethane foam. This type of abrasive is used to smooth surfaces with grooves, threads, and recesses. Abrasive particles can be applied to one, two or four sides of the sponge. May be the same size or different. But usually, this is a fine grain, just of varying degrees of “fineness”. Sponges are more convenient because they can take any shape; in addition, they can be washed to remove dust and dried. The number of washes is not limited. They do not suffer from washing; they can be used while the grain is still intact. And this depends on the quality.

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Types of sandpaper grit

As already mentioned, sandpaper grit is the size of the abrasive fragments. They are measured in micrometers. The smallest grain found in sandpaper is only 3-5 microns, the largest is 1000 microns (this is 1 mm). Based on grain size, fine-grained and coarse-grained abrasives are distinguished.

Usually we are only interested in the grain size or grit of the sandpaper

Russian standards

In order to be able to understand what specific material is in front of you, the dimensions of the abrasive grain are indicated in the marking. But things are not so simple with her. During the USSR, GOST (3647-80) was introduced, the designation according to which still exists, although in 2005 a new standard was introduced (GOST R 52381-2005), which was developed on the basis of pan-European standards. The difference between the old and new GOST is significant.

This marking method is used in some countries of the post-Soviet space.

• According to the old standard, the minimum grain size is prescribed. That is, the higher the number, the larger the grain. But we must keep in mind that some of the grains are smaller. In addition, the markings (letter designation) for large and small grains are different. It's worth remembering. For coarse-grained sandpaper , the grain size of the sandpaper is indicated in microns , and after it the letter N is written with a hyphen in front of it - “N”. For example, 63-N . This means that the minimum grain size on the sandpaper will be 63 microns or 630 micrometers (µm). But there will also be larger particles. How much bigger? Slightly smaller than the previous brand. In this case, only 80-N is larger than 63-N, that is, the grain will be slightly less than 800 microns. The second example is 6-H. The grain size is no more than 6 microns or 60 microns, and the largest ones will be no more than 80 microns (since the previous grade is 80-N).

• When marking fine-grained sandpaper, the grain size is indicated in micrometers , and after the number they put the letter “ M ” (without a hyphen). Example: 14M. This means that the maximum grain size of sandpaper is 14 micrometers, but there are also finer grains up to 10 microns in size.
• According to the new standard (GOST R 52381-2005), the grain size of sandpaper is indicated by the number of fibers of the sieve through which the abrasive is sifted. It turns out that the lower the number, the larger the grain. The number is preceded by the letter “P”.

As you can see, it's already quite confusing. It is also worth saying that according to the old standard, fine-grained emery can have a double designation - with the letters M and H - as in the table. Moreover, more often the options in microns were in use. Therefore, the smallest grain - 5M or 00-N - is often called zero. This is because it is 3-5 micrometers in size. According to rounding rules, this can be considered zero. This is where the name came from.

Compliance tables for other countries

As we see, the situation is not simple. And there is also the American ANCI (USA and Canada), the European FEPA or its other name ISO 6344, the Japanese JIS and the Chinese GB2478. Moreover, on the market you can find material from almost all these countries/parts of the world. So it is advisable to have at least some data. The most common ones are shown in the tables.

Grit designation table for different standards: coarse grain

Sandpaper grit according to different countries' standards: fine-grained

Please note that next to each column the grain sizes in micrometers (µm) are written. Sizes vary. This may be important for work.

Sandpaper markings

Sandpaper marking is a set of letters and numbers that encodes complete information about the type of base, abrasive, application method, composition and grain size. We have already looked at graininess. This parameter appears at the end of a series of letters and numbers. It’s more or less clear with him. In general, sandpaper markings display the following data (starting from the first character):

• what material is the grain made from?
• skin base;
• binder with which the grain is glued to the base;
• methods of applying grain;
• type of base (paper or fabric);
• water resistance (if not waterproof, there is no symbol);
• sandpaper grit.

Sanding paper markings

Let's look at the rest of the characteristics that are encrypted in the labeling. The letters here are in Latin. Let's take an example of what the following marking means: KK19XW. So:

• first K - type of abrasive - normal electrocorundum;
• second K - base - cotton fabric;
• 1 - two-layer application of a binder (resin + resin).
• 9 — type of application is unclear;
• X - textile type - hard.
• W - indicates that the material is waterproof.

Next should be the letter P and numbers that determine the grain size of the sandpaper.

Types of abrasive

The first letter in the marking indicates the material from which the abrasive is made. It is the abrasive material that is responsible for how much effort must be applied during processing. The stronger it is, the longer you can work with one piece of sandpaper. Unfortunately, the rule here is true: the better, the more expensive.

• K - “normal” electrocorundum. The abrasive is brown in color (shades may vary). The most common and relatively inexpensive material.
• C—silicon carbide. Very durable material. It does not wear off for a long time and clogs little. For processing glass and plastic, for finishing metal polishing. Types of sandpaper. They differ not only in grain size, but also in the material from which this grain is made.

• G—zirconium electrocorundum. It has a brick-red color due to the addition of zirconium. It is characterized by increased wear resistance, but is more expensive than the “usual” one.
• A - alloyed electrocorundum. It has a titanium additive, which gives it a blue color. Perhaps the most durable. Recommended for grinding difficult-to-process materials.
• V - white electrocorundum. It is distinguished by its white color due to the large amount of aluminum.
• S - ceramic electrocorundum.

If, looking at the photo, you decided that the emery was tinted, then in vain. Different colors are given to it by various additives used in the manufacture of abrasive substances. Another thing is that most often we see brown, gray or dark gray sandpaper for sanding. They are simply the cheapest and most popular.

Types of base

The base of the sanding paper is the material on which the abrasive is glued. This material determines the degree of flexibility and resistance to deformation. It also depends on the base whether this type of sandpaper can be used for dry or wet sanding.

In the marking, the type of base is encrypted by the second letter.

• Woven base. The fabrics are woven from cotton and synthetic fibers: K - cotton fabric. High strength, wear resistance, not afraid of getting wet. The disadvantage is that it can lengthen during operation. This is bad for belt sanders.
• X - polyester textile. Compared to cotton, it is more wear-resistant. Used for the production of tapes of various widths. The base is dense. It can stretch slightly when inserted into grinding machines and does not deform for a long time. Emery cloth - sandpaper on a woven (textile) basis

• Y - synthetic. Used in the furniture industry for polishing wooden panels. Withstands very heavy loads.
• J - elastic cotton fabric. Used for processing minor relief.
• JJ or F - cotton fabric with increased elasticity. These types of base are for narrow belts and for processing deep relief. They stretch and bend very well.

If we talk about the base, then the cheapest sandpaper is paper based. It is usually used for manual processing or mounted on a hand holder. For sanding machines, a woven base is often used. But cotton or polyester is your choice. Who likes what more?

Binder

In the third position in the marking of the sanding paper there is a number that encodes the method of fixing the abrasive to the base. They use glue or polymer resins or combinations thereof. The glue “adheses” well to the abrasive and the base. Single-layer application of the binder (number 2 in the corresponding position on the marking) is used where the emery is not subject to heavy load.

Methods for gluing abrasive to a base. Glue or resin is used, their combinations in different orders

To hold the grains more firmly, a second layer is poured over the glue. Most often this is a resin (phenolic or any other). The result is a bundle - glue + resin (number 3 in the marking). The second layer of binder makes the sandpaper more resistant to abrasion.

There is another option - resin + resin (this is 1 in the encoding). That is, both the first and second layers are made of bakelite resin. The cost of this option is higher, which determined its area of ​​use - production.

Method of applying and pouring grain

There are two ways to apply grain to the primary binder layer: free and electrostatic. When free, abrasive particles simply pour in. They lie in a free order, their direction is random. With the electrostatic method of filling grain, the paper is passed through an electric field. As a result, the grains have the same orientation, which makes the surface rougher.

Abrasive is applied in different ways

In addition, there are two types of grain filling: open and closed. They differ in the number of particles per unit area. When the backfill is open, the sharp fragments are located at a distance from each other, and the base is visible (open). This paper is good when working with loose materials. For example, with wood. Wood dust wakes up, the abrasive does not clog.

The closed backfill of grain on sandpaper is denser. The abrasive particles lie next to each other, the base is practically closed and cannot be seen. This type of sandpaper is good for hard materials (steel, for example).

Release forms and types

Our usual form of release is in rolls or sheets. The sheet can be based on cardboard, or it can be on thick paper. Most often it is more rigid than rolled. Roll sanding is most often used on belt sanding machines, and for manual use too. In addition, there are the following types of abrasive materials:

• Abrasive wheels. Used for installation on attachments for special machines. These can be grinders, drill attachments, angle grinders. There are different types: Regular circles of different diameters and different grain sizes.
• With Velcro glued to the back.
• Petal ones are when strips of sandpaper are glued to the base. Can be of different grain sizes. They are used for rough processing of metals (usually) and for removing paint (including from concrete).

  Abrasive sanding paper is available in the form of sheets, rolls, tapes, and wheels. There are other forms - for attachments to instruments

There are also sanding sponges. This is an abrasive that is applied to polyurethane foam. This type of abrasive is used to smooth surfaces with grooves, threads, and recesses. Abrasive particles can be applied to one, two or four sides of the sponge. May be the same size or different. But usually, this is a fine grain, just of varying degrees of “fineness”. Sponges are more convenient because they can take any shape; in addition, they can be washed to remove dust and dried. The number of washes is not limited. They do not suffer from washing; they can be used while the grain is still intact. And this depends on the quality.

What should be the grit of sandpaper for the job?

As you understand, different sanding cloths are used for different processing of materials. Now we are not talking about the form of release, but about the size of the grain and the method of applying it. The type of abrasive and method of application is of secondary importance. They have a greater impact on the durability of the material. But as usual, better means more expensive. Here everyone chooses for themselves. But it is better to select the grain size for specific tasks.

Sandpaper for sanding wood for painting: choosing a grain size

What sandpaper to sand wood

To prevent the skin from clogging, the grain should be applied at intervals. This is an open type of application. In this case, you won’t have to “knock it out” or change it often. Base type - paper or fabric. Paper is cheaper, fabric is more expensive. If you have a grinder, see the recommendations for it. For manual processing, you can fix the piece on a special holder or nail it to a block.

How to choose sandpaper grit for wood processing

Recommendations for choosing grain size are given in the table. For primary processing, sandpaper from P40 to P80 is used. This is giving shape, removing a thick layer. We use the same materials to remove varnish and paint from wood. To prepare wood for painting you need P100 to P240. For sanding after applying the first layer of varnish, use P360 or P400. And bringing it to smoothness - actually polishing and varnishing - is already very small P500 and above. In general, polishing is a separate topic, and there you need to sand and apply paint or varnish step by step. And each time the grain is taken finer and finer. And the polishing is completed with a generally soft polishing (felt) material.

Which emery abrasive to use on metal?

To process metal, you will have to use harder, and therefore more expensive, abrasive materials. Regular corundum will cope with aluminum and its alloys. They also process cast iron, bronze and black steel. For brass you need at least zirconium, but preferably titanium or alloyed electrocorundum. And even better - ceramic. Please also note that the application method must be closed.

For grinding and polishing metal, you need a different type of sandpaper, and we select the grain size according to the type of work

The principle of selecting the grain size is the same: for rough processing, increased “roughness” of the coarse grain; the finer the processing, the finer the abrasive. To remove rust and level out the main roughness, use the coarsest sandpaper. The thinner the layer, the smaller the grain size. So everything is logical here. But note that for each type of work there are two or three grit sizes. This does not mean that you need to take any of the above. This means that to get a good result you need to process each size. Although, if appearance is not so important to you, then you can use one of the recommended sizes.

Sandpaper for plastic, stone, ceramics and glass

Regarding the type of abrasive and its application, the recommendations are the same: stronger, more dense. But sanding is recommended with water supply, so a waterproof modification of the sandpaper is required.

Sandpaper for plastic: choice of grit

For finishing plastic and glass, sandpaper even with the smallest grain - the same zero or P800 - will be too coarse. It will leave visible scratches. These materials are brought to smoothness using GOI paste and even finer grinding compounds. But this is a separate story and its own technologies.

What is sandpaper

Emery, sandpaper (or just sandpaper), sandpaper, abrasive or sandpaper - these are all names for the same material. This material is an abrasive on a flexible basis for manual or machine processing of various materials. There is sandpaper for metal, wood, plastic, glass. They are sometimes used for processing plaster and putty, but for these purposes a sanding mesh may be more convenient. It doesn't clog like that.

Sandpaper, sandpaper or paper, sandpaper, sandpaper - that's all about this material

Sandpaper abrasives are small particles of hard materials of varying sizes. These particles are called grains, and their size is called grit. They are glued to a flexible base. Sanding/abrasive paper-based sandpaper is more common. This is the cheapest type, but not the most durable. The fabric base is more reliable, but can stretch, which is also not always convenient when working. Polyethylene-based emery is a waterproof sanding material. This is the most expensive type, but you can even work in water. For wet processing, sanding on waterproof paper is also used.

Sandpaper is used for processing metal, wood, plastic, glass

Sandpaper is used to eliminate irregularities and defects, to obtain a smooth surface, grinding and polishing. So sanding can be rough or fine. By rough we mean the removal of paint or rust, burrs, and the initial leveling of the surface. For this work, material with coarse (from 500 microns to 1 mm or more) and medium (from 200 microns to 500 microns) grains is used. Obtaining an even and smooth surface - grinding, polishing - is already a fine or finishing treatment. For this type of work, sandpaper with fine grain (less than 200 microns) is used.