What is the importance of belt grit for sanders? – Setafi

One of the important indicators is the grain size of the belt for grinding machines. The size of the granules on the surface and the purpose of the tape depend on it. In some cases, the material is used for fine processing, in others - only for rough. The main selection criteria, grit marking are described in the article.

What is granularity

Grit is the most important characteristic of the tape, which determines the scope of its application. Meaning has different characteristics:

• types of abrasive powder;
• granule size (grain size);
• method of applying abrasive powder.

Abrasive belts are made on the basis of different chemical compositions:

1. Silicon carbide is a very hard powder and is therefore used on metal, plastic, painted surfaces and fiberglass.
2. Pomegranate is a natural material of high hardness, suitable for processing wood of any species.
3. Ceramic abrasive is another hard powder that is used on wood-based materials, including to level the surface.
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4. Aluminum oxide is a coarse powder used in woodworking. The metal is soft, so the grains "spread" a little when heated. Thanks to this, they form new faces and work effectively even with repeated processing.

The method of applying the abrasive also matters. To cover the surface of the tape with many granules, 2 filling technologies are used:

1. Open and semi-open - the grain covers about half of the surface (within 40-60%). In this case, the tape is used only for working with soft materials. It can be wood with a high resin content, putty surface and others.
2. Solid or closed coating - in this case, the abrasive powder completely covers the surface. These belts are used for grinding hard surfaces. It can be metal or hardwood.

Depending on the purpose for which the tape is intended, the size of the grains (granules) can be either very small (3-5 microns) or relatively large (2-3 mm). This is discussed in more detail in the next section.

Grain levels

Of particular importance for grinding is the degree of graininess, that is, the size of the abrasive granules. According to this parameter, 2 types of granularity are distinguished - fine and large. They are designated by the letter "P" and certain numbers, as described below.

fine grain

Fine-grained tapes are used for various tasks, among the representatives of this group there are 4 categories:

1. From P240 to P280 - final grinding.
2. From P400 to P600 - polishing of the final coating.
3. P1000 - fine processing.
4. From P1200 to P2500 - delicate grinding.

Coarse grain

In the group of coarse-grained abrasives, 4 categories are also distinguished:

1. Especially large (denoted in the range from P22 to P36). These tapes are only suitable for rough grinding.
2. Large (from P40 to P60) are tapes that are used for starting grinding wood or other materials.
3. From P70 to P120 - the abrasive is used for primary processing.
4. From P150 to P220 - for final grinding.

When purchasing tapes of one grain or another, you need to evaluate how suitable they are according to the correspondence table. To do this, check the size by comparing it with the Russian standard according to GOST 3647-80, and, if necessary, also with European, Chinese or American standards.