Why do the brushes on an angle grinder wear out quickly?

The principle of operation of an electric motor is based on the interaction of a conductor with a current in a magnetic field.

The main element of its construction is the permanent magnet for DC motors, the excitation winding for AC motors. The rotor (armature) has its own winding, which is energized by a brush-collector assembly. The interaction of the magnetic fields causes the rotor to rotate.

The commutator consists of a set of contacts, which are copper plates located directly on the rotor. Micanite or mica wool sleeves act as insulators for each individual contact. Graphite brushes. sliding contacts pressed against the collector.

Brush replacement on angle grinder

Angle grinder (or as it is also called “angle grinder”). an indispensable and in-demand tool in the work of the master. Like any other, it is subject to natural wear and tear. During the operation of the tool, various breakdowns occur, and one of the most common is brush sparking on the angle grinder. In this article, the master plumber will tell you why the brushes on the angle grinder spark, as well as why they burn out and how to replace them.

Before you figure out the causes of sparking brushes on the angle grinder, you need to understand their purpose. Collector brushes are used not only in the construction of angle grinders, but also in the device of all modern power tools. drills, torches, jigsaws, and others.

In the construction of the angle grinder and other power tools, 2 brushes are used, which have a simple design.

brushes, angle, grinder, wear, quickly

This design is based on the following elements:

  • The main part. has a rectangular shape, and is made of carbon or graphite;
  • The contact is a wire strand of the appropriate diameter through which the electric current flows. The contact connects the wire to the graphite part;
  • The spring is the mechanism that ensures that the main part is pressed against the manifold. There may be no spring on the element, and this indicates that such a brush is designed for installation in power tools, where brush holders have a built-in clamping mechanism in the form of a curved plate.

The devices are designed to transmit electrical current to the rotor of the angle grinder.

The voltage drawn from the stator is applied to the rotor, which is reproduced by the carbon brushes and the collector. Feeding current to the collector allows the collector to rotate.

As the rotor rotates, the devices make contact with the collector (copper lamellas. armature winding outputs), thus ensuring the continuous flow of electric current.

Angle Grinders. 5 Common Issues & How to Fix Them

In the process of use, the devices wear out, so they are classified as consumables. The service life of brushes depends not only on the operating life of the power tool, but also on the materials from which they are made. The wear of the brushes is affected not only mechanically by friction, but also thermally. Electric current heats a conductor as it travels through it. The higher the value of the current, the higher the heating temperature. When current flows through the graphite brushes, they also heat up. The higher the load on the power tool, the higher the current, and therefore the temperature increases, which negatively affects the integrity of the consumables.

Brushes for angle grinder and other power tools are made from different materials, but the main ones are carbon and graphite. This particular material has a low coefficient of friction and also has a high abrasion resistance. To improve contact, various impurities are added to the graphite or carbon in the manufacture of the brushes. Depending on the impurities used, the following types of brushes are distinguished:

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

Causes of strong sparking brushes on the brushes of lathes are the following factors:

  • Armature winding faults. If the armature winding insulation fails, then it may cause an inter-turn fault, or a core fault. Winding breaks may also occur, eventually causing a higher load. A characteristic sign of a faulty armature winding is a decrease in speed, an increase in noise and a drop in power;
  • Brushes not pressing properly on collector. For clamping the main part is responsible for the spring, which loses its original springing properties over time;
  • The rotor winding is torn from the copper plate of the collector. this phenomenon is very rare, but when you overload the power tool, it may well happen;
  • The armature of the electric motor is misaligned, eventually causing the brush on the angle grinder to spark violently;
  • Collector shape is disturbed. The manifold, consisting of copper lamellas, has a cylindrical shape which can be disturbed when the rotor is rewound. If there is the slightest deformation in the shape of the collector, there will be arcing of the brushes The collector of an electric motor;
  • Insulation between the collector blades is broken. Each collector plate is insulated to each other, and if the micanite insulating layer is broken, arcing occurs. The insulation between the plates can also be disturbed due to settling of the graphite layer in the grooves;
  • Armature bearing deterioration. If the bearings are defective, then the rotating armature will run out and consequently, there will be signs of arcing;
  • Distortion of the rotor shaft. It is difficult to bend it, but if it does, the motor starts to run with the load. It is advisable to replace the rotor to prevent the tool from failing;
  • If the ends of the armature windings are improperly soldered to the copper plates of the collector. Such mistakes are not made at the factory, but they can be made by the winder who rewinds the armature of the power tool;
  • Unsuitable composition of graphite brushes. The parts in question are made of carbon and graphite, adding different kinds of impurities. This is done for a reason, but in order to use the brushes depending on the voltage and speed of rotation of the shaft. Graphite is either soft or hard. The lower the supply voltage, the softer the graphite grade is chosen. For high-voltage power tools, you must take hard brushes that have no copper in their composition;
  • Deformation of the blades due to heat. If the angle grinder is subjected to excessive loads, one or more of the collector lamellae may be deformed. The plates are lifted relative to the rest, resulting in a broken contact. Such a fault causes a strong sparking of brushes during operation of the power toolDamage of the angle grinder’s manifold;
  • Poor contact at the brush connection. If the terminal is loosely connected to the device, the result of such a contact failure can manifest itself as excessive sparking;
  • The presence of carbon deposits on the copper fins. periodically or regularly it is recommended to clean the surface of the copper fins from carbon deposits. Fouling is usually caused by worn brushes, so if you find blackening on the surface of the manifold, it should be wiped with alcohol.
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In addition to arcing, often the owners of power tools are faced with the fact that the brushes on the angle grinder burn. This phenomenon differs from arcing in that there is rapid wear and tear of the main part of the element. After installing new elements, wear and tear occurs as soon as the power tool is used for the first time.

The main reason lies not in the brushes themselves, but in the manifold. If the lamellae fall out or wear out on the collectors, it causes the load to increase. it is the graphite elements that are subjected to this stress and that start to wear out quickly when the angle grinder is turned on. this accelerated wear and tear process is called combustion. The elements are literally burning because of the high current flow. Many people call this process abrasion, but in reality, the brushes are not capable of rapidly erasing themselves through mechanical action. The cause of burning is a strong spark, causing the graphite to literally just burn out.

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

  • Loss or wear of the collector’s copper lamellae.
  • There is a short circuit between the lamellae or the rotor winding. this causes the current to increase, which heats up the brushes and causes them to burn. To determine the cause, you will need to test the armature
  • If the power tool is overloaded. if you use the angle grinder for a long time without interruption, the result of such use will manifest itself as a burnout of the brushes in 5-10 seconds.

There is also such a thing as a circular fire. This phenomenon occurs when there are large shocks in the armature current, e.g., overloads, short circuits, and under-voltage. Circular fires occur when the arc is repeatedly ignited. Increased loads and even short circuits occur when using an angle grinder for wood sawing. When wood is processed, the cutting disk is clamped, thus increasing the current to 15-25 times its nominal value. The most common cause of burning elements is the collector, so if you had to change 2-3 pairs of brushes in a month, it is time to make a diagnosis of the power tool.

Many people change the brushes only after they notice a strong sparking of the tool and a burning odor. Many masters do not stop even these signs, and they continue to operate the tool until it ceases to turn on. When it is necessary to change carbon brushes, so as not to harm the device of the power tool. The following signs are available for this purpose:

  • Strong arcing. If there are signs of strong arcing, disassemble the tool and inspect the consumables. Sparking is the first sign that the consumable elements are to be replaced;
  • The appearance of an odor of burning. if you can hear the smell of fouling when working with the tool, it is recommended that you disassemble the angle grinder and replace the graphite brushes;
  • When wear and tear on the main part exceeds 30% to 40%. However, it is almost impossible to determine their initial length unless you measure it before installing the elements;
  • If signs such as jerking and “growling” of the power tool appear.
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Replace if irregular wear and tear or inadequate quality.

When replacing the brushes, as with any penetration into the housing of the power tool, you must disconnect the power supply by pulling the plug out of the socket.

angle grinder brush replacement without disassembling the housing

Some manufacturers have taken a very rational approach to the possibility of replacing brushes. There are screwed plugs in the machine housing. And the whole process of checking or “repairing” takes two minutes (for both graphite contacts):

  • If a brush has lost 70% to 80% of its length compared to a new one, you should replace it. Otherwise, the old graphite contact must be placed on the same side as it was before it was removed in order to eliminate the lapping process. The brushes do not wear uniformly because they are in contact with a rotating cylindrical surface;

This is the easiest way to replace the brushes on an angle grinder without having to disassemble the housing. That’s why you can take this into account when choosing a new angle grinder.

Angle grinder brush replacement without back handle

On grinders that do not have a back handle, the brushes are replaced in the following sequence:

  • Insert the new brush, close the contact block with the cover;
  • Repeat all the steps with the other brush;
  • Put the cover on the angle grinder and secure it with the self-tapping screw.

Sometimes there is another way to attach the brushes

In this case, the sequence of operations will be as follows:

  • Connect the contact of the new graphite rod to the connector, insert the brush into the guide block and press down with the spring;
  • Repeat all the steps with the second brush, close the housing with the hood and screw it on with a self-tapping screw.

These are the two most common ways to replace the graphite contacts.

The angle grinder sparks and twitches. What is the problem? How to fix an angle grinder?

Replacing brushes on the angle grinder with a backhandle

Angle grinders that have a back handle allow you to get to the brushes in a slightly different, simpler way:

  • Near the handle you need to find a small repair window, closed by a plastic plate, which is fixed with a bolt;
  • It is necessary to unscrew the self-tapping screwdriver, pick up the plastic plate in the groove with a screwdriver, remove it from the housing, opening the repair window;
  • The following steps for replacing brushes are the same as for low-power grinders: release the band spring (1), release the plug (2), remove the brush from the guide block by the wire;
  • Then insert the new brush, connect the plugs, secure the graphite rod with a tape spring, cover the repair window with plastic and screw the bolt;
  • Repeat all the steps with the second brush on the opposite side of the housing.

It’s possible that there may be other ways to replace the graphite brushes, due to the design features of the grinder.

In the story. What happens if you don’t change the brushes on the angle grinder in time

brushes, angle, grinder, wear, quickly

In the story. Why the brushes on the angle grinder burn, spark, what are the causes of faults

Angle grinders are structurally different, so the methodology for replacing brushes may differ slightly from the basic methods described above. But the common features can still be seen:

  • The brushes are near the back handle or the part of the body that is designed to hold the tool.
  • The most common designs of carbon brushes: with and without spring.

The first type of construction implies a simplified method of replacement, because it has a wire, a contact plate and a compression spring.

Springless brushes require a slightly more laborious replacement process, because the retaining spring is attached to the housing and is stiffer, and the wire is attached in a separate location with a plug.

Carbon brushes of any kind

The part is a rectangular parallelepiped made of carbon and graphite.

There is a short wire embedded in the part, the other end of which is soldered to the brass nickle or to the complex shaped lock.

The wire is held in place by a compression spring. Some heels are connected to the button with terminals.

Irregular brush angle and bearing wear

Ideally, the sliding contacts should be located directly on one mowing line on either side of the axis of the rotating manifold. They can become misaligned in the long run if they are held loose or deformed, or if the rotor does not rotate smoothly due to improper bearing condition.

Important! To eliminate sparks, adjust the position of the elements of the unit by means of the fasteners provided by the manufacturer (usually screws).

Brushes, supports and mounts that are mechanically damaged, show signs of corrosion and have worn bearings must be replaced. The diagram below shows a collector assembly with properly installed brushes. You can also find videos on the internet for the current model showing the entire repair process with the electric motor.

When to change them?

The brushes for the washing machine have a guaranteed life of 5 years, and with careful use of the device, it can exceed ten years. Since the brushes are close to the axis of the rotor, which rotates, over time, these parts will wear out.

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There are various reasons for rapid wear and tear on the elements, including:

Such improper operation leads to abrasion of the brushes within a few years, and their replacement is simply necessary, because the motor will not work.

To determine if this wear part needs to be replaced, look for the following symptoms of malfunction:

  • Sudden loss of engine power or complete stoppage of operation.
  • Unusual noise when the drum rotates.
  • Some modes do not work correctly.
  • A burning smell emanating from the machine.
  • The machine does not pick up speed when wringing, resulting in the laundry remaining wet.
  • An error code appears on the machine’s display.

Important! In order to determine whether you need to replace the brushes in the washing machine, first check for foreign objects in the drum. These are the ones that may produce an unusual noise. Check the condition of the drive belt, and also test the mains voltage. Worn bearings may also produce some noise. If after checking all the above parts are in good condition and there are no foreign objects in the drum, proceed to replace the brushes.

In domestic applications, the brushes have an average life of 80-120 hours. But it makes no sense to keep track of the drill, so it will be relevant to use a special brush wear indicator, it is if the tool is not equipped with an automatic shutdown at wear.

Sparking occurs when there is an inter-turn fault in one of the windings. In this case, carefully inspect the stator windings, an obvious sign is that the varnish on one or both windings has darkened. You can also measure the resistance of both windings, it should be the same.

In the process of operation the brushes are rubbing due to the constant friction. This necessitates their replacement. For this the manufacturer supplies the power tool with a spare brush set. In other situations, you may observe sparks in the brush area.

Electric current when flowing through a conductor causes it to heat up. The greater the amount of current, the higher the heating temperature. When current flows through the graphite brushes, they also become hot.

Useful instructions. how to replace the brushes and the angle grinder cord

It is not uncommon for an Interskol angle grinder to stop working because the cord is broken or the brushes are worn, so they can barely reach the stator and the machine does not perform at its full capacity.

You already know how to remove the cord from the previous removal instructions for the angle grinder button (with p.1 to par.3). It remains to figure out how to get to the brushes and replace them with new ones.

  • Using a Phillips screwdriver, unscrew the fastening screws of the handle on both sides;
  • Using the above-mentioned diagram, we find the brush holders, in which the parts we need are located;
  • Disconnect the brushes from the common electrical circuit of the angle grinder, picking up the tips with a flat screwdriver and simply pulling them out by hand;
  • Insert the new brushes in their place. If you can not find in stores native brushes, it is allowed to take their size a little bit larger. with a file they can be ground to a suitable size. Not a problem if the new brushes have different tips. cut off the lead from the worn brushes and screw it onto the new ones;
  • Replace the brush head cap and screw it back on.

Having disassembled angle grinder it is recommended to blow it from dust with compressor.

Also check the armature manifold, which may be scratched from worn brushes. Scratches can be sanded down with emery cloth.

How to change

Angle grinder maintenance with motor brush replacement is easy.

Remove the back cover of the housing and you get access to the brush-collector assembly. In our video we show you an example of the Interskol 115/900 (also valid for 125/900).

With some models of angle grinder enough to unscrew the plastic plugs on the sides of the housing, and the brush assembly with springs, current collectors and contacts will fall out by themselves.

Brush unit, located on the body of the angular grinder Makita GA9020, makes it easy to change brushes. Photo by AllInstruments.manual

Replace brushes when they reach one-third of their original height of wear.

Use only gasoline or mineral spirits to clean and rinse the collector and brush holders.

Blowing out and drying the interior of the machine is easy with a car compressor. A domestic vacuum cleaner can be used.

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Some manufacturers produce pretreated brushes. These brushes do not require a running-in period.

Run (run-in) flat-faced brushes on the angle grinder at idle speed, without load. After the running-in period it is advisable to blow out the brush units and the collector to remove the carbon dust.

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