Why do the brushes on the angle grinder spark strongly?

Strongly spark the brushes of the motor of the power tool reason

It’s hard to imagine an arsenal of home without such a popular power tool as angle grinder angle grinder or angle grinder (popular name). The angle grinder has gained its popularity due to its versatility, as this tool can be used for cutting, grinding, sawing, polishing, deburring, sharpening, and other work. over, you can handle absolutely any material. During the operation of the tool, there are different breakdowns, and one of the most common is the sparking of brushes on the angle grinder. Why the brushes on the angle grinder spark, not many people know, so let’s understand this issue, as well as find out why they burn out and how they are replaced.

Sparks, including on a working engine, appear due to mechanical effects between the brushes and the collector. Moving along the collector from one of its contacts to another, the brush alternately makes and breaks the connection with each of them. Now remember what happens if you unplug any working electrical appliance. usually at that moment a spark flashes between the plug and the socket. In the case of a brush motor, this is the same phenomenon.

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Therefore, a little sparking even on a functioning electric motor is acceptable, because the connection and the gap here are constantly occurring.

What to do if the drill sparks

Wholesale production of hand grinders started in the USSR in the year of. Today not a single manufacturing facility can do without this tool. But every tool breaks down at some point, but many parts can be repaired at home. The most common malfunction you can try to repair is a broken stator coils. This is mainly due to high overloads. Rewinding the stator of an angle grinder with your own hands is quite possible today. But this kind of work does require experience and know-how. When the voltage increases, the strength of the spark increases by leaps and bounds.

Brushes for angle grinder and other power tools are made of different materials, but the main ones are carbon and graphite. It is this material that has a low coefficient of friction and also has a high resistance to abrasion. To improve contact, different impurities are added to graphite or carbon in the composition of the brushes. Depending on the admixtures used, the following kinds of brushes are distinguished:

The composition of the main part affects not only durability or wear, but also such parameter as signs of sparking. The sparking level of the brushes depends on the composition from which they are made. When buying them, you need to pay attention to the composition, and not to buy equipment of unknown origin and of dubious quality.

This is interesting!In the design of the brushes there is a ceramic tip, which performs one of the important tasks. When the graphite layer is abraded to the limit, the tip begins to contact the copper lamellae of the manifold. Ceramics do not conduct electricity, so the angle grinder with abrasion brushes will work intermittently or will not turn on at all until the device is replaced.

The main malfunctions of angle grinders and their causes

According to statistics, most cases of failure of the angle grinder are related to the electrical part of the machine. Some failures may be minor, which allows you to repair the angle grinder with your own hands. But, for example, if the burnout of the motor windings repair angle grinder can make only a specialist.

angle grinder does not turn on

Reasons for an angle grinder not turning on may be the following:

  • The electrical plug is defective;
  • The electric cable is defective;
  • the start button is broken;
  • the contact between the power cable and the button is broken;
  • The contact wire of the electric brush is broken;
  • Heavy wear and tear on the electric brushes;
  • Rotor or stator winding failure.
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the angle grinder does not rotate

There are various possible reasons for the angle grinder not picking up speed.

  • Rotor or stator windings defective. To check this version, connect the motor of the appliance directly without the regulator and check the operation of the device.
  • Failure of the electric cable due to permanent kinks or mechanical damage. Because of this, the damaged wire begins to warm up under load, and the engine speed drops.
  • the collector is contaminated with dust. The contamination must be removed with alcohol.
  • Problems with brushes. They can wear out or have a short contact wire, as shown in the following photo.

The brush is half worn out, but is still serviceable. The short contact wire prevents the spring from pressing the electrode against the collector. This situation can also be the reason why the angle grinder does not operate normally.

Motor overheats

Angle grinder overheating can be caused by.

  • Improper operation of the machine. Overloading can overheat the motor and often causes the windings to burn out.
  • Destruction of the bearings on the armature. As a result, the rotor is caught in the stator, the motor is hindered in its work and the windings overheat. The problem can be solved by replacing the bearings.
  • The ventilation ducts through which air flows to cool the motor are clogged. The ventilation openings must be cleaned of dust.
  • Failure of the impeller, which is used to cool the motor. It is mounted on the rotor, on the opposite side to the collector. If the impeller is broken, it must be replaced with a new one.

The angle grinder sparks

If you notice heavy arcing when you turn on your angle grinder where the collector is located, this problem may be caused by.

  • Damage to the armature winding: breakage of one or more sections of the winding, inter-twist short circuit. Such damage results in excessive noise, low engine speed and burned brushes.
  • The contact between the collector plates and the winding is faulty.
  • The brushes are not pressing hard enough. With long modes of the angle grinder, the springs overheat and can “anneal”, losing their elasticity.
  • Unbalanced motor rotor.
  • Cylindrical surface of the collector is broken. This sometimes occurs after a rewind if the armature is not turned on the lathe but installed directly into the machine. Brushes may also be observed to spark excessively in this case.
  • The insulation between the lamellae of the manifold is broken. There may also be graphite clogging of the slots or a breakdown between the lamellae.
  • Bearing wear, which causes the rotor to run out, also causes the brushes to spark strongly.
  • Armature shaft geometry is distorted. It usually happens in case of careless disassembly of the electric motor, when the shaft is bent.
  • The wrong brand of graphite brushes are installed. Brushes should be chosen according to the speed and voltage to be expected.
  • Lifting one or more blades causes the brushes to burn out quickly. This happens because of engine overheating in continuous operation. As a result, the glass mass that serves as the base of the collector softens and the lamellae begin to rise. Because the blades are up, the brushes wear out very quickly.

Why is one brush on the angle grinder on fire?

But the inner voice prompts that there is still another possible reason. One of the causes of brush arcing is the high inductive emission when the collector lobe opens. In some cases, such sparking can develop into a circular fire. In our case, only one brush sparks. That is, there is the presence of asymmetry. Assuming that there is a short-circuited coil in one of the stator shoes? Then the behavior of the rotor windings will be different, depending on which shoe they are near. Or rather, according to their orientation relative to each shoe. As the rotor rotates, all of its windings alternately pass both shoes. But the brushes do not change their position relative to the shoes. Thus, it is logical to assume that the unequal shoe (due to a short in the winding of one of them) is the cause of the unequal behavior of the brushes. That is, each plate of the rotor collector, opens on both brushes in different conditions, with different self-induction eds.

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The difference in the shoes can be not only because of a short circuit in the winding. If you consider that the described angle grinder is already old and worn out, then during this time it can easily have a one-sided bearing depletion on the rotor shaft. There are more than enough side loads, and the bearings don’t last forever. A clearance between rotor and stator shoes is small. That’s why even slight one-sided bearing wear can noticeably introduce asymmetry into the clearances. And then one shoe will be farther away and the other closer to the armature. The mutual inductance can change many times, and this too can cause the effects I have described above.


To attach the current-carrying wire to the brush holder bolt, a lug is attached to the end of the wire.

The basic types of lugs used are shown in Table 2:

Examples of complete lug designations:

8PG2-10. flag closed lug with a hole diameter of 8 mm, for two wires with a cross section of 10 mm2;

5FG1-1.5. flag closed lug with a hole diameter of 5 mm, for one wire with a cross section of 1.5 mm2.

Why do the brushes on an angle grinder burn out?

In addition to sparking, often the owners of power tools are faced with the fact that the brushes on the angle grinder burn. What distinguishes this phenomenon from sparking is the rapid wear and tear of the main part of the element. Immediately after the installation of new elements, there is wear and tear the first time you use the power tool. It is necessary to understand why the brushes on the angle grinder burn.

brushes, angle, grinder, spark

It is not the brushes themselves that are the main cause, but the collector. If the lamellas fall out or wear down on the manifolds, it increases the load. This load is experienced by the graphite elements, which, when you turn on the angle grinder, begin to wear quickly. this process of accelerated wear is called combustion. The elements are literally burning because of the high current flow. Many people call this process abrasion, but in reality, brushes cannot wear out quickly due to mechanical stress. The reason for burning is the high level of sparking, which causes the graphite to burn in the truest sense of the word.

The reasons why the brushes on the angle grinder burn are as follows:

  • Loss or deterioration of the copper lamellas of the collector. Video shows how the collector blades look like. The material also shows how to try to correct such a malfunction
  • There is an inter-twist fault between the lamellae or the winding of the rotor, which causes the brushes to heat up and begin to burn. To determine the cause, you will need to wire the anchor
  • If the power tool is heavily overloaded. if you operate the angle grinder for a long time without interruption, the result of such use will manifest itself as a burnout of the brushes for 5-10 seconds

There is also such a thing as circular fire. This phenomenon occurs with large armature current surges, such as overloads, short circuits, or with a drop in line voltage. Circular fire appears when the arc is repeatedly ignited. An increased load and even a short circuit occurs when using an angle grinder for wood sawing. When working on wood, the cutting disc is jammed and the current increases by a factor of 15 to 25 times its nominal value. Most often the collector is the reason of burning of the elements. If you had to change 2-3 pairs of brushes in a month it means that it is time to make a diagnostics of your power tool.

brushes, angle, grinder, spark

Preventive maintenance of manifolds

In order to prolong the life of the armature, and therefore the power tool itself, it is necessary to follow a few simple rules. These measures are as follows:

  • Do not let the tool work for a long time at low speed with a substantial load, much less jamming of the cutting part. If the electric motor jams, a short blocking time is enough for it to burn out.
  • If the device is jammed, carefully loosen it and let it idle for two minutes. During this time, the heated parts will have cooled down through natural cooling.
  • Observe the time limits for the addition or replacement of lubricants.
  • If you notice vibrations or noises, it is necessary to have a preventive examination with disassembly of the case and cleaning of dirt from the collector and the whole space inside.
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Any self-repairing of power tools, not only angle grinders, is not recommended before the end of the warranty period. The manufacturers do not recommend tampering with the appliance without authorization. It doesn’t concern only replacement of brushes without opening the case, and in other cases it is better to apply for help to an authorized service center.

An angle grinder is a high-speed electric tool equipped with a collector motor. In this motor, the current is supplied to the armature, the internal rotating part. Such feeding is carried out by the sliding method, and the only way to implement the contact of the power source with the moving part. graphite “brushes”. They are “fuses” against overvoltage and are the first to fail.


The structure of the pile and the shape of the product depend on the work for which the nozzle on the angle grinder is designed. The right choice can make life easier for the craftsman performing the work. Brushes in the following shapes are available on the tool market:

  • Cup-shaped. Cup brushes are perfect for hard brushing over large areas. The vertical trim on cup brushes ensures the correct force vector.
  • Tapered. These products have bristles inclined at an angle to the reference plane. This design allows you to work parts with small depressions in the surface.
  • Radial. These tools are also referred to as “mounding brushes”. They are designed for final cleaning of workpieces from scale formed after pickling procedure. Special pile positioning allows you to work in hard-to-reach places.
  • Disk. This shape is the most common. The bristles are on the horizontal plane of the tool. Not suitable for large jobs, but works well in narrow recesses.

Brushes are made with different types of wire:

  • Twisted. This type of design is characterized by a wire twisted in random strands. pressure is applied to the surface, but the tool life is much shorter.
  • Harness. Angle grinder brushes with a knotted filament, arranged in a strict order, are advantageous due to their robust construction, as well as the self-sharpening effect in the course of work.
  • Corrugated. The wavy wire design gives the brush a curved effect. This softens the impact on the surface to be treated.

The size of the brush head depends on the size of the angle grinder. Their diameter ranges from 75 to 200 mm.

Brushes for angle grinder have proven to be much better for processing large areas. For cleaning workpieces with complex shape or curved surfaces we recommend a similar drill bit which has exactly the opposite properties.

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