Classification of brushes for a grinder and features of their choice

Brushes are called both current collectors inside the grinder - a necessary element of the electric motor, without which an angle grinder, like any other electric tool, cannot work, and removable nozzles, which allow cleaning, grinding and even polishing various surfaces with this tool. In this article we will try to deal with these and other brushes.

If we talk about electric brushes, then first you need to clarify the name. This device was called brushes even in the early days of its existence (the beginning of the 20th century), when, in fact, a design resembling a brush or, more precisely, a brush was used to remove current from the rotor of an electric motor. Such a device, despite its high efficiency, turned out to be too short-lived and was replaced by a more durable one, made of a dense material, into which a copper wire is pressed.

The movement of the rotor of the electric motor causes constant friction of the working surface of the electric brushes, which is the main reason for the failure of this part. As a result, they have to be changed periodically. This process is natural and inevitable during prolonged use of any power tool. It is very easy to identify the wear of the brushes: the previously reliable unit will start to work intermittently, the characteristic smell of ozone may appear from the abundant formation of sparks in the current collector. It is advisable to replace the electric brushes at the first sign of abrasion.

In the first case, the product is pressed at high pressure, and then thermally processed, acquiring increased wear resistance. The coal option is the cheapest, since it does not involve heat treatment. These brushes are the least durable. Metallographite brushes are the most expensive because, in addition to carbon, they contain metal powder. This is the most durable option, which can be found very rarely in household appliances. As already mentioned, a removable nozzle for a grinder is also called a brush.

In order for the UMSh (angle grinder) to perform its main functions, it is necessary to install one or another nozzle on it. These can be cutting discs or grinding discs or brushes with various kinds of nap, fixed in a circle. Such a removable device is called a cord brush or, even shorter, a cord brush. Brushes, as well as disks for UMSh, are consumables. In the process of work, they wear out, and they need to be changed. The grinder brushes are designed in such a way that they are installed on the stem thanks to the hole in the center, this is their main difference from the drill brushes, which have a shank for installing them in the drill chuck.

In this section, we will not talk about electric brushes for a long time, their purpose is to remove current from the rotor (armature), in other words, without them there will be no rotation in the electric motor, the rod of the power tool will not rotate, and it will not work. But about the cord brushes it is necessary to say in more detail. They are used for machining various materials.Different types of these nozzles are used for cleaning before painting or applying primer, for brushing wood, for removing old paint from various surfaces, for polishing, sanding, smoothing corners and other operations.

As already mentioned, electric brushes can be classified according to the material from which they are made. A graphite brush, as the name suggests, is made from graphite, to which soot and bonding elements are added. This type of slip ring is most often used for UMSh.

The carbon brush is made of the same material, but without heat treatment. Such a product wears out much faster and is practically not used for a grinder. It is important not to make a mistake when purchasing replacement brushes. Carbon brushes on a grinder will not last long.

The metallographite brush is used in large industrial units, and it is unlikely that it will be possible to install it on a grinder. It is the most durable product with a very high price tag. The variety of cord brushes is much greater, their shape, material and size vary significantly, which is determined by the variety of applications for such equipment. They can also be classified according to the material from which they are made. The most popular are brushes with metal bristles. The metal brush is a fairly versatile attachment. For the manufacture of such products, both metals and alloys are used.

For work on metal, steel brushes are used. Stainless steel brushes are best used on stainless steel or aluminum. Often steel pile is covered with brass, such brushes do not corrode. There are also pure brass brushes - despite their great softness, they have a number of advantages: a relatively soft effect on the material, no sparks when working at high speeds, no scratches during surface treatment.

The wire for such brushes can be different. Twisted wire is usually the toughest, and can be bundled (stiffer and self-sharpening) or chaotically secured. These efficient attachments can be used to scrape off welding scale or rust. The corrugated cord brush has a wave-like curved pile and, unlike the previous type, does not affect the surface as intensely. With its help, you can clean the surface from old paint.

Even brushes are widely used, they are the most versatile and can be used on any surface. Their effectiveness may be slightly lower than that of specialized attachments. Tips with polymer bristles, such as nylon, are used for polishing various surfaces, including metal. They can be successfully used for woodwork - for texture selection or finishing. Plastic brushes are often used on soft materials.

The brushes can also be divided according to their shape.

The cup is used for working with large surfaces. Its form follows from the name. On such a brush, a clamping nut is most often immediately fixed, since the special key provided in the kit with the grinder cannot be applied to it. The conical brush is used for working with concave surfaces. Radial, as a kind of flat brushes, is used to process hard-to-reach areas. Disk, the most common type of cord brushes, also has a flat shape and can be used to process a wide variety of small surfaces.

And more cord brushes are divided into size groups. The diameter of the brushes is determined by the technical capabilities of the grinder and the scope of this attachment. Brushes with a diameter of less than 115 mm are usually used for small surfaces.It is better not to use a circle of more than 200 mm for a small grinder, you will have to remove the protective casing, and this is a violation of all safety standards. Such large brushes are usually used for processing large structures and only with the help of large powerful UMSh.

The most acceptable for domestic purposes is the diameter of the brushes 125 mm. It is possible to offer a fourth classification of cord brushes - by application. Brush brush, the name is given from the name of the technical operation, which is carried out using this nozzle. Brushing - preparation of the surface for subsequent processing: removal of rust, paint, dirt. At some stages, this is a process of chemical action on the surface of the product, but the initial treatment consists in mechanical cleaning of the surface. For mechanical brushing, metal (steel or brass-coated) brushes are used. The task of such processing is to remove scale, oil stains, small defects, burrs, and the like. Without brushing, it is sometimes difficult to assess the quality of the weld, the adhering scale can hide some defects.

In stores, the choice of cord brushes for a grinder can be very wide. Consider what you need to consider when choosing this type of attachments. The selection parameters may be dictated by the nature of the work to be done and the size of the angle grinder on which the brush will be installed. In no case should you install a nozzle designed for a large unit on a small grinder. It is also important to know the number of revolutions of the grinder, the brush must be selected in accordance with this indicator. If there is a circle designed for low speed on a fast grinder, its effectiveness will be small, since, most likely, it will fail even before the end of the work. Working on a "slow" grinder with a nozzle for a revolving unit will be very laborious and will take much more time than with a brush that matches the capabilities of the angle grinder.

If you have decided on the size and type of brush, you should pay attention to its quality. The wire iron bristle should have a uniformly distributed pile, individual villi should not be longer or shorter, this factor can cause poor-quality surface treatment and excessive vibration, therefore, loads not only on the grinder's parts, but also on the hands of the person who will perform the work ...

Excessive vibration of the machine during operation is the main reason for the high stress on the muscles of the arms. With a small diameter brush, vibration is always less. A polymer brush is the lightest type of cord brushes, and the vibration with it is the least, but not every surface can be processed with such a nozzle. A polymer-abrasive brush is used for brushing (aging) wood, and you should not try to process metal with it.

If you have no experience with cord brushes, of course, you need to consult, and sometimes you have to purchase several different attachments in order to determine the best model in practice in the process of work. The most popular manufacturers of cord brushes, presented on the shelves of specialized stores, can be built into a kind of rating. Russian brands: Zubr, Praktika, SibrTech, Enkor. Foreign: DEXX, FIT, MATRIX, Lessmann, Wortex.

Installing or changing a cord brush on a grinder is no more difficult than doing it with a cut-off wheel. You need to fasten it with a nut, and the same standard open-end wrench with pins is used to tighten and unscrew it. Some cup and cone brushes come with a nut. Replacing such a nozzle is even easier, just screw it onto the pin.Working with a cord brush does not imply strong pressure in the direction of the surface to be treated; this can cause the appearance of furrows, which will be a sign of poor-quality, unprofessional processing.

Operation without a protective cover is inadmissible. Safety goggles or a mask are required to protect the eyes from splinters of wire cord, shavings or flying pieces of old paint and metal scale. The high speed of rotation of the brush can give the shards a completely unpredictable trajectory, so the eye protection must fit snugly against the face. It is also advisable to protect your hands from sparks and chips, small metal splinters or cuts with large chips and sharp edges of scale are possible.

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