Do-it-yourself grinder speed regulator repair

In detail: do-it-yourself repair of the grinder speed controller from a real master for the site my.housecope.com.

Do-it-yourself repair of an angle grinder is a completely solvable task. The main thing is not to rush, understand the design, remember all the circumstances under which it broke down, determine what could wear out during work, diagnose and start repairing.

The grinder is called an angle grinder (angle grinder). The name of the tool is due to the fact that it was produced by the Eltos-Bulgarian plant in Plovdiv. It is intended for performing work on grinding or cutting hard material:

Good for tool sharpening.

The grinder in our time is a very necessary tool, so almost everyone has it.

There are grinders of different power: from 500 W to 2500, depending on the thickness of the circle - from 115 mm to 230 mm. The most popular in the work are angle grinders with a power of 1.2 W, and the most used disk is 125 mm thick.

Every year, the choice for this construction power tool is becoming wider, but the operating rules hardly change. And even if you always adhere to them, sooner or later malfunctions occur in the mechanism, which you can try to fix with your own hands, collecting everything you need to repair the grinder.

Any grinder consists of the following parts:

rotor - the part of the electric motor that rotates during operation and is speed-controlled, also called the armature;
collector - a place on the rotor where the control winding wires are located;
brushes - parts that serve as current conductors from the cable to the collector winding;
gearbox - a mechanism that acts as a drive from a rotating rotor to a spinning disk, consists of a spindle, a bearing, two gears (a large one and a shaft gear);
stator - part of the electric motor in which the rotor operates;
grinder cooling impeller;
start button;
network cable with electric drive;
protection casing;
grinder body;
additional handle.

Video (click to play).

All these details can be divided into two parts:

How to disassemble the grinder? Not such a complicated process. This does not require special knowledge, but it is necessary to do everything carefully and with caution. Each owner needs to know how to disassemble any working tool, because periodically it needs internal cleaning from dirt and dust, and its durability depends on this.

At the present time on the market, you can choose a different type of grinder, which differ in performance, size, quality. Manufacturers are also different. Whatever model of grinder you purchase, all have the same assembly model of parts.

Disassembling the grinder will require a few tools, you just need a regular screwdriver or a reversible ratchet.

Having prepared a screwdriver, you can start disassembling:

We unscrew the screws from the case and remove one side of the product.
We remove the nut, thanks to which the disk is held, unscrew the bolts securing the protective casing.
We take the brushes off.
Disconnect the wires from the engine.
We unscrew the bolts that secure the gearbox inside, and very carefully remove it, and the rotor is also removed with it.
We unscrew the bolts that hold the stator, and remove it.
We assemble the grinder back, put everything back in place one by one and fasten it.

When disassembling the grinder, it is important to remember the order in which the parts are removed in order to assemble it correctly.

In the event of a malfunction, first of all, it is necessary to exclude elementary breakdowns:

Bulgarian does not turn on. The angle grinder suddenly became faulty - it stopped turning on. In this case, you need to check the serviceability of the outlet, then the plug and the power cord, perhaps the drive simply does not work due to the fact that current does not enter the product.
The cable with the plug is intact, but the drive does not work. You need to check the start button. It is easier to repair the grinder switch by buying a new button and replacing it. Since it is rarely subject to repair, basically, the plastic switch rod breaks inside. If you want to experiment, you can disassemble it by numbering the contacts, and put everything back in place so that after assembly there is no short circuit.
The above parts are intact, and the angle grinder does not want to work - so it's time to check the brushes. Perhaps it's time to change them in the grinder. Brushes from work are constantly heated, so they wear out quickly and more often than other parts need to be replaced, and in pairs.

Having eliminated all minor breakdowns, it is necessary to understand why the tool does not want to turn on and how to repair it. Most likely, the malfunctions are serious, requiring additional knowledge. This happens if:

the body is deformed;
jammed one of the bearings;
armature or stator does not work;
broken or worn teeth at the gear of the gearbox;
the collector is out of order;
the control electronics sensor does not show signs of life.

If it is determined that the malfunction occurred in the mechanical part of the grinder, then you need to pay attention to the condition of the large gear located on the shaft and the bushings. If the teeth are partially worn out or the shafts are wobbly, they must be replaced immediately.

The most common breakdowns

Malfunction grinders happen quite often. Everyone who works with this tool knows about it. What goes wrong most often?

Just one awkward press on the spindle lock button while the disc is spinning causes it to break. Sometimes it can be broken if it is used to remove a jammed disc. To prevent this from happening, you need to use an open-end wrench inserted into special holes near the disk attachment point.

It mainly occurs when jamming occurs. If a rumble is heard in the gearbox, this is a sign of just such a malfunction. When more than one tooth is broken at the gear, the angle grinder will not be able to cut the necessary material.

In order for the tool to continue working, it is necessary to change the gears, and that’s all, and even the bevel wheel. Before going to the store for spare parts, remember the manufacturer, model and power of the product.

This type of failure occurs with angle grinders that work in places where there is a lot of dust, and when they are given a rest, they are left on the ground. Dust that gets inside spoils the winding. Large loads, especially for a small power grinder, turn into a motor breakdown.

If the grinder is used to cut materials that create a lot of dust, then it is recommended to cover the ventilation holes with something.

The weakest link, and not only for angle grinders, are bearings. A high frequency of rotation quickly wears out the mechanism. The good news is that changing the bearing is easy. Replacing a sprinkled bearing with a grinder must be done on time so that there is no breakdown that cannot be fixed.

This breakdown is easy to determine when the angle grinder is turned on, but the disk revolutions are too intense and differ from normal operation - which means that there is a turn short circuit in the stator on the winding. Stator failure is considered the most serious, and special skills are needed to eliminate it. When there are doubts about your abilities, it is better to turn to professionals so that later you do not have to buy a new tool.

If the decision to repair it yourself is made, it begins with cutting off the frontal parts of the winding, the remnants are all removed.The next step is to make a new winding according to the pattern. It should be identical in number of turns, with the same density and from wire of the same thickness as the previous one.

Angle grinders whose power is less than 1100 W are usually equipped with spur gears. They are on the stator. Bulgarians with more power have helical gears. Each of the options has a conical shape, the shaft of the grinder gearbox intersects with the stator shaft at an angle.

Repair of the grinder gearbox mainly consists in replacing the gears. In the event of a broken disk gear, it is difficult to replace it, because it is very firmly fixed. Disassembling the gearbox is easy:

you need to unscrew the nut from its side;
carefully take the rotor housing in a vise and knock out the gearbox housing with light blows;
change the position of the clamped rotor and knock out the bearing through the wooden board;
unscrew the gear from the shaft.

The speed controller is not present in all models of grinders. When the angle grinder is used for cutting, it is, in principle, not needed, but if grinding is carried out, it is simply necessary. If it suddenly stopped working, then most likely the board burned out, which must be removed and bought the same in a power tool store for further replacement.

Self-repair grinder is not always feasible. If suddenly something does not come out or everything is not clear, it is better to contact the service center.

Before completely breaking down, the angle grinder gives signals about the onset of problems.

Pay attention to the work of your assistant: you should be alerted if:

the brushes began to spark too much;
during operation, the grinder heats up;
the motor hums inside the case when the tool is turned on;
the vibration of the body has become much greater during the performance of work;
grinder gearbox cracking inside;
the sound of bearings creaking during spin-up or periodic wedging is heard when the rotor shaft rotates;
The angle grinder smoked, or an uncharacteristic burning smell emanated from it.

In order not to buy a new angle grinder, you need to be attentive to the operation of the tool. In case of any deviations from the usual work, start troubleshooting, determine the cause and repair the power tool.

The service life of the grinder directly depends on the owner's care for it. Each tool needs good care, then it will work properly for a long time.

Any angle grinder will warm up during operation, but in order to postpone the repair of the angle grinder for a long time, it is necessary to adhere to some rules at work:

Do not overload the tool to avoid overheating and smoke.
Do not press hard on it during operation.
Clean and lubricate the necessary parts inside the case in time.
If abnormal operation is noticed, stop operation and inspect for malfunctions.
Replace wearing parts in a timely manner.
If the grinder smokes, immediately stop work and do not turn it on again.
Do not use the tool when processing wood type material.
Hold the grinder firmly during operation so as not to drop or damage it.

By adhering to the listed simple recommendations and rules in working with a tool called a grinder, you can extend its life longer than provided by the warranty period.

All budget options for angle grinders have several drawbacks. First, there is no soft start system. This is a very important option. Surely all of you have included this powerful power tool in the network, and when you start it, you have watched the glow of the light bulb, which is also connected to this network, drop.

This phenomenon occurs for the reason that powerful electric motors at the time of startup consume huge currents, due to which the mains voltage sags. This can destroy the tool itself, especially Chinese-made ones with unreliable windings that may one day burn out during start-up.

That is, the soft start system will protect both the network and the instrument. In addition, at the moment the tool is launched, a powerful recoil or push occurs, and in the case of a soft start system, this, of course, will not happen.

Secondly, there is no speed controller, which will allow you to work with the tool for a long time without loading it.

The diagram below is from an industrial design:

It is introduced by the manufacturer into expensive devices.

You can connect to the circuit not only the "grinder", but, in principle, any devices - a drill, milling and turning machines. But taking into account the fact that the collector motor should be in the tool.

With asynchronous motors, this will not work. It needs a frequency converter.

So, you need to make a printed circuit board and proceed with the assembly.

You can download the board from the following link at the bottom of the article.

A dual operational amplifier LM358 is used as a regulatory element, which controls a power triac using a transistor VT1.

So, the power link in this circuit is a powerful triac of the BTA20-600 type.

There was no such triac in the store and I had to buy BTA28. It is slightly more powerful than what is according to the scheme. In general, for engines with a power of up to 1 kW, you can use any triac with a voltage of at least 600 V and a current of 10-12 A. But it is better to have some margin and take 20 A triacs, they still cost a penny.

During operation, the triac will heat up, so it is necessary to install a heat sink on it.

So that there are no questions about the fact that the motor at start-up can consume currents that significantly exceed the maximum current of the triac, and the latter can simply burn out, remember that the circuit has a soft start, and starting currents can be ignored.

Surely everyone is familiar with the phenomenon of self-induction. This effect is observed when opening a circuit to which an inductive load is connected.

The same is true for this diagram. When the power supply to the motor abruptly stops, the self-induction current from it can burn the triac. And the snubber circuit dampens the self-induction.

The resistor in this circuit has a resistance of 47 to 68 ohms, and a power of 1 to 2 watts. Film capacitor for 400 V. In this embodiment, self-induction as a side effect.

Resistor R2 provides current suppression for the low voltage control circuit.

The circuit itself, to some extent, is both a load and a stabilizing link. Due to this, after the resistor, you can not stabilize the power. Although the network has the same circuits with an additional zener diode, it is pointless to use it, since the voltage at the power supply terminals of the operational amplifier is within normal limits.

Possible replacement options for low-power transistors can be seen in the following picture:

The circuit board mentioned earlier is only a board for the soft starter and does not contain any speed control components. This is done on purpose, because in any case, the regulator must be output using wires.

The regulator is tuned using a 100 kΩ multi-turn trimmer.

And the main adjustment is already using the resistor R5. It is worth saying that a scheme of this kind will not allow adjustment from zero, only from 30 to 100%.

If you need a more powerful regulator, then it can be assembled according to the following scheme:

This scheme allows you to adjust the power from almost zero, but for the "grinder" it does not make sense.

First, the circuit must be checked for operability by connecting a 40-60 W 220 V light bulb as a load.

If everything is in order, then after disconnecting from the network, you immediately need to check the triac by touch - it should be cold.

Further, the board is connected to the "grinder" and the launch is performed.

If everything is working fine - the grinder starts smoothly, and the speed is regulated - then it's time to start testing under load.

I would like to use the grinder as a cutter, for stripping, grinding, etc. anything. But here's the problem, it's very high turnover. I have two grinders, alas, without speed control. Of course, you can buy another third, with speed control, but I don’t see much point in this.

And using a “cup” type nozzle with brass wire is generally dangerous. First of all, it is designed for speeds up to 5000-6500 rpm. the grinder has 12000 rpm by default. As a result, the metal wires from the brush scatter, hitting everything around with their wire. An unpleasant feeling, and just dangerous.

Seeing on Ali a block that allows you to reduce speed, I bought such a block. Received, connected, working. Indeed, the speed has decreased to the level where the destruction of the brushes does not occur. I will not say that it is possible to reduce these revolutions to zero, but practically at the very minimum, it decreases by half.

At first I tried to put a block in the grinder itself. It didn't work out. There was too little space in the hull of the grinder. Therefore, I had to make an external unit with regulation. But this is not even bad, since it can be used for many purposes.

I made it in the case of an external, two-socket box, I used one part of the bark for the adjustment unit, and the second socket, where the angle grinder is connected. To do this, the block itself with sockets had to be sequestered. Yes, so as to leave a mount for the screw holding the socket housing.
Then I cut out a plate with a hole for the adjusting resistor from a white soap dish.
Since the resistor was originally soldered to the board, in order to place it as planned, I had to unsolder it from the board by connecting it to the board with wires.

All placed and secured. I glued the panel and screwed it on with small screws. Now this whole structure looks like a regular extension cord. However, when setting the maximum current, it can be used this way.

The Bulgarian, being the most demanded tool in the house, is subjected to considerable loads and intensive use. Because of this, after some time, it happens that jerks, a burning smell and other malfunctions appear when starting the engine, suggesting that the angle grinder (angle grinder) has broken down. But do not immediately carry the device for repair or buy a new one. Most of the malfunctions of this device can be eliminated independently.

Over the long years of the existence of such a tool as an angle grinder, its appearance, as well as the internal structure, have not changed much. To repair the grinder with your own hands, you need to know the device of its mechanical part, as well as the electrical one.

If you look at the figure below, you can see what parts the angle grinder consists of.

Wheel for adjusting the spindle speed of the unit.
An electric motor consisting of a rotor and a stator.
Start button. Sometimes a soft start system is connected to it.
Housing made of impact-resistant plastic.
Button for locking the spindle (used when changing tools).
Safety clutch. Protects the motor from overload when the tool jams.
Protective cover. Closes the tool and protects the user from flying particles of the processed material, and also prevents injury to a person when the tool is destroyed, for example, an abrasive disc.
A nut holding a tool. It is unscrewed using a special key that comes with the power tool. There are also quick-lock nuts that can be unscrewed without a wrench.
The gearbox housing and the gearbox itself. It consists of a block of gears that transmit rotational movements from the rotor to the spindle with the tool.

The figure below shows electric circuit grinder.

The electrical part of the angle grinder has the following elements:

electrical cable with a plug for connecting to the mains;
start button;
stator;
electric brushes (carbon or graphite);
collector;
anchor (rotor).

The following figure shows grinder connection diagram, namely its engine.

All components of the electric motor perform certain functions.

Rotor - this is the shaft on which the coils and the collector are placed. The rotor, rotating in the magnetic field of the stator, transmits rotational motion to the angle grinder gearbox.
Collector. It is a part of the rotor to which all control cables are connected. Electrical signals from the control unit to the engine pass through the collector. It is to the collector that the electric brushes are connected.
Electric brushes. Their main task is to transfer electric current from the power cable to the collector.
Stator. It is a coil with a certain number of turns. The task of the stator is to create a magnetic field, which, interacting with the armature, sets the latter in motion.

According to statistics, most cases of angle grinder failure are associated with the electrical part of the apparatus. Some breakdowns can be minor, which allows you to repair the grinder with your own hands. But, for example, if the motor windings burn out, only a specialist can repair an angle grinder.

The reasons that the angle grinder does not turn on may be the following:

electrical plug is defective;
defective electrical cable;
start button broken
the contact between the power cable and the button is broken;
breakage of the contact wire of the electric brush;
strong wear of electric brushes;
failure of the rotor or stator windings.

The reasons why the angle grinder is not gaining momentum can be different.

Breakdown of the speed control unit. To check this version, it is necessary to connect the device's motor directly, bypassing the regulator, and check the operation of the device.
Electrical cable failure due to permanent kinks or mechanical damage. Because of this, the damaged wire begins to heat up under load, and the engine speed drops.
Collector pollution with dust. Alcohol stains must be removed.
Brush problems. They may be worn or have a short contact wire, as shown in the following photo.

The brush, although half worn out, is quite functional. In this case, a short contact wire does not allow the spring to press the electrode against the collector. This situation can also be the reason why the angle grinder stopped working in normal mode.

The reasons why the grinder is warming up may be as follows.

Incorrect operation of the machine. As a result of overloads, the electric motor can become very hot, which often leads to burnout of the windings.
Bearing destructionlocated at anchor. As a result, the rotor clings to the stator, the operation of the motor is difficult, and the windings overheat. The problem is solved by replacing the bearings.
Clogged ventilation ductsthrough which air enters to cool the engine. The ventilation openings must be cleaned of dust.

Impeller failureused to cool the engine. It is installed on the rotor, on the side opposite to the collector. If the impeller is broken, it must be replaced with a new one.

Image - Do-it-yourself grinder speed regulator repair

Interturn short circuits stator and rotor windings. You will need to rewind the coils or replace these parts with new ones.

If you notice a strong spark when you turn on the angle grinder in the place where the collector is located, then the causes of this trouble may be as follows.

To diagnose the electrical part of the angle grinder, as well as eliminate the mechanical breakdowns of the device, you will need to disassemble it. Disassembly is carried out according to the following algorithm.

Unscrew the handle.

Remove the protective cover.

Open the special windows located on the sides of the angle grinder casing and remove the electric brushes after disconnecting the terminals.

Unscrew the gearbox housing from the angle grinder motor housing.

Gently pull on the gearbox housing and detach it from the casing. In this case, the gear unit will be removed together with the rotor.

After removing the armature, the motor stator will remain in the casing, which is also easily removed for diagnostics after unscrewing the fasteners.

To disassemble the gearbox, unscrew the screws holding the cover. After removing the cover, you will see the gears of the gearbox.

To remove the anchor from the grinder, you will need to unscrew the nut inside the gearbox.

In order to remove the bearing from the armature, it is recommended to use a special puller. Otherwise, the shaft may be damaged.

As mentioned above, most often the angle grinder refuses to work due to breakdowns in the electrical part of the unit. For the correct diagnosis of the electrical circuits of the tool, electrical repairmen use a special device - tester.

If you pressed the start button of the unit, and it does not work, then in 90% of cases the cause of the breakdown is not so serious that you cannot repair the grinder with your own hands.

Experts advise adhering to the basic rule of repairing power tools: move from simple to complex.

First of all, you will need checking the electrical cable and plug at its end. If it is collapsible, then unwind it and check the reliability of the contacts. Otherwise, you will have to disassemble the grinder (remove the casing of the device) and “ring out” the cable with a tester, and also make sure that the current is coming to the contacts of the “Start” button. If the device shows a break, then the cable should be replaced with a new one.

The situation when the current flows to the button, but does not pass further (when the position is on), speaks of switch malfunction. The button can't be fixed. It must be replaced with a new one, but first mark the contacts to be removed in order to connect them correctly in the future. If the contacts are connected incorrectly, the motor winding may burn out.

If during the test it turned out that both the cable and the start button are working, but no current is supplied to the brushes, then it is necessary to cleaning the contact plates of the brush holders. If this procedure is ineffective, it is recommended to replace the brushes. Further, if everything is fine with the brushes, and current is supplied to them, you should check the rotor and stator for short circuits and breaks.

The rotor of the electric motor may have the following malfunctions: interturn short circuit and breakage of conductors at the contacts of the lamellas. You can check the anchor of the angle grinder with a multimeter: the device is switched to the resistance change mode, the value is set to 200 ohms, and the resistance between two adjacent lamellas is measured using probes. Thus, it is required to check all pairs of lamellas. If the resistance values are the same, then the rotor winding is not damaged. Detection during the “ringing” of other resistance values, as well as the detection of an open circuit, indicates a malfunction in this coil. In this case, repair of the anchor of the angle grinder will be required.

Typically, a conductor break occurs at the junction with the winding. Inspect the places where the coils are connected to the lamellas, make sure that the soldering of the contacts is reliable.

If you do not have a measuring device, then you can check the rotor by using 12V bulb and battery. Power should be in the range of 30-40 watts. The check is done as follows: apply 12 V voltage from the battery to the plug of the angle grinder, connect a light bulb to the gap of one wire, start rotating the angle grinder spindle. With a good winding, the light will burn evenly, without blinking. With an interturn circuit, the degree of incandescence of the bulb spiral will change.In this case, repairing the anchor of an angle grinder with your own hands will be difficult, since the anchor winding scheme is quite complicated, and the process itself requires special equipment and knowledge. Therefore, this operation is recommended to be entrusted to specialists. But the best way out of the situation would be to replace the anchor on the angle grinder with a new one.

If the lamp does not light up when testing the rotor, this indicates an open in the stator or a short circuit in its windings, as well as problems with the electric brushes.

To check the stator of the grinder, use, as in the previous case, a multimeter. Values needed set to 20-200 ohms and do the following. Touch one probe to the contact of the stator winding, and the second to the body of the part. If the device shows resistance, this means that a breakdown has occurred on the case. Touch the probes to the contacts of one winding, and then to the contacts of the other. If the resistance is the same, then the coils are working. If the device shows an open circuit on one winding, then the stator will need to be rewound or the part replaced with a new one.

It will be problematic to rewind the stator at home without special knowledge, skills and equipment. It is better to contact specialists who are professionally engaged in rewinding engines.

The mechanical breakdowns of angle grinders include the following.Mechanical failures include breakage of the shaft retainer. In order to replace the retainer, you will need to disassemble the gearbox and remove the large gear.

Do you have a grinder, but no speed controller? You can make it yourself.

Both are necessary for reliable and convenient operation of the power tool.

This device is designed to control the power of an electric motor. With it, you can adjust the speed of rotation of the shaft. The numbers on the adjusting wheel indicate the change in disc speed.

The regulator is not installed on all angle grinders.

The lack of a regulator greatly limits the use of the grinder. The speed of rotation of the disk affects the quality of the grinder and depends on the thickness and hardness of the material being processed.

If the speed is not regulated, then the speed is constantly kept at maximum. This mode is only suitable for hard and thick materials such as angle, pipe or profile. Reasons why a regulator is necessary:

For thin metal or soft wood, a lower rotation speed is needed. Otherwise, the edge of the metal will melt, the working surface of the disk will become blurry, and the wood will turn black from high temperature.
For cutting minerals, it is necessary to regulate the speed. Small pieces break off from most of them at high speed and the cut becomes uneven.
You do not need the highest speed to polish cars, otherwise the paintwork will deteriorate.
To change the disk from a smaller diameter to a larger one, you need to reduce the speed. It is almost impossible to hold a grinder with a large disk rotating at high speed with your hands.
Diamond blades must not be overheated so as not to spoil the surface. For this, the turnover is reduced.

The presence of such a launch is a very important point. When you start a powerful power tool connected to the network, an inrush current occurs, which is many times higher than the rated current of the motor, the voltage in the network sags. Although this surge is short-lived, it causes increased wear on the brushes, motor commutator, and all parts of the tool through which it flows. This can cause the tool itself to fail, especially the Chinese one, with unreliable windings that can burn out at the most inopportune moment when turned on. And also there is a large mechanical jerk at startup, which leads to rapid wear of the gearbox. This start prolongs the life of the power tool and increases the level of comfort when working.

The electronic unit allows you to combine the speed controller and soft start into one. The electronic circuit is implemented according to the principle of pulse-phase control with a gradual increase in the opening phase of the triac. Such a block can be supplied with grinders of different capacities and price categories.

As you know, nothing is eternal, and even the tools of branded manufacturers break down, not to mention the so-called “consumer goods”. And the grinder (angle grinder) is no exception. By the way, they began to call the angle grinder "Bulgarian" during the time of the Union, because then this tool was produced in Bulgaria and the first models were supplied from there. The grinder, as a tool, has become very widespread due to its versatility and ease of use. There are also many varieties and models of angle grinders, however, the principle of operation and the device are not fundamentally different. Therefore, having considered the device of the tool, possible malfunctions and repair methods, they can be applied to any model of the grinder.

Bulgarian device relatively simple. The basis of the tool is its body, inside which there is an electric motor, a starter and a gear transmission to the spindle, on which various nozzles are mounted.

The case is made of strong impact-resistant plastic. Depending on the power, there are various dimensions and shape of the tool. Some models have an angular speed regulator, which is designed to optimally select the speed for various types of work.
Another component can be a reducer. The gearbox is designed to create optimal conditions for the transfer of rotation from the rotor of the electric motor to the cutting or grinding wheel. This reduces the number of revolutions on the output shaft of the gearbox. Properly selected rotation speed and circle diameter is the key to the most efficient operation of the tool.

The button for replacing the working disk, when pressed, locks the disk in a certain position, preventing it from scrolling when removed.

The safety clutch serves as a limiter in the event of a sudden reactive torque. In another way, when the disc is jammed in the material, the grinder itself starts to rotate sharply, which can lead to injury to the worker. This clutch does not allow this rotation.

The electric motor normally consists of a stator and a rotor. The stator is located in the guide tides of the plastic body of the grinder. On the back of the stator there is a special device called a brush mechanism. It contains copper-graphite brushes. Brushes are needed to transmit voltage to the rotor through the collector assembly.

The rotor is located inside the stator and is fixed in the housing in bearing assemblies, which are inserted directly into the tool housing. The front bearing assembly is usually made in a metal plate, or this plate can be made of aluminum alloy.

The gearbox housing of the angle grinder is almost always made of aluminum alloy and has several threaded holes for attaching an additional handle. By screwing the handle into various holes, you can change the plane of location during operation.

The gearbox consists of two gears, with the help of which the direction of the output shaft is changed by 90 degrees and the rotation speed is reduced. The ratio of the number of teeth on the primary gear to the number of teeth on the secondary gear is called the gear ratio.

Bulgarian suddenly stopped working.
The first thing to do - disconnect physically from the network and manually rotate the disk. If the disc does not spin or spins very tightly, immediately disassemble the tool for visual inspection. If it spins easily, then the most likely thing is that electricity does not reach the brushes of the electric motor. That is, the problem lies either in the power plug, or in the wire itself, or in the mechanism of the Start button.It is enough to disassemble the case and “ring out” the cable with a conventional tester, or in some other way, for a break. After eliminating the break or replacing the wire, the grinder will work.

The wire and plug are guaranteed to be intact, but the tool still does not work.
It is necessary to disassemble the trigger, and it is desirable to mark the contacts to be removed - if they are subsequently connected incorrectly, the winding may burn out or the armature may jam. It is not often possible to repair the trigger mechanism - it is easier and more reliable to replace the trigger button with any similar one with suitable power parameters. Such a button is not so expensive and you can buy it in any store of the corresponding profile.

The start button and the power wire are in working condition, the grinder does not work.
Check brushes and brush holders. There may be a break or complete wear of the brushes. The resource of these devices is usually limited to several years, of course, it all depends on the intensity of use. Repair break or replace brushes.

More serious malfunctions follow, respectively, and repair requires certain knowledge and skills.

- breakage or licking of the gear teeth of the gearbox;
– jamming of bearings;
- failure of the armature or stator;
– failure of control electronics;
- failure of the collector;
– deformation of the hull;

When determining the mechanical defects of the grinder, more attention should be paid to the condition of the plonitary (large gear), shank (gear on the shaft) and bushings. Uneven wear of the teeth or the shank of the shafts indicates the immediate replacement of worn parts.

Breaking out the spindle lock button.
The reason is just one careless movement, namely pressing (intentionally or accidentally) on the button when the disk is spinning. Sometimes breakdowns occur due to attempts to remove a jammed disk using a button. Many grinders on the spindle, where the disk is attached, have slots especially for a regular open-end wrench, look at your grinder, most likely you have one. So, it's better to use them and an open-end wrench than a disk lock button.

Chipped gear teeth.
Usually occur due to jamming (in such a situation, a tool breakage is not the worst thing that can happen). A sign of a malfunction is a rumble in the gearbox. If the gear has lost two or three teeth, then the tool will not be able to cut.
In this case, it is necessary to change the gears in a pair and the gear itself and the bevel wheel. When you go to the store for gears, do not forget to write down the name of your grinder and its power.

Failure of the electric motor.
This often happens with tools that work in dust and are forced to rest in sand or on the ground: the sucked-in dust wears down the winding. However, you can ruin the motor without dust - by strong overloads, especially if the tool is low-power. Therefore, in small grinders, not only the anchor, but also the stator often burns out. Small angle grinders also have a breakdown of the electronic speed control unit. If you use a grinder to cut very dusty materials, in particular slate, a stocking put on the ventilation slots in the case helps to protect the instrument.

Bearings.
Another sore spot for angle grinders (as well as other twisting power tools). Few machines stand out for their strong immunities against dust, and the high speed implies rapid wear. In general, bearings are not the worst failure, they are easy to change. However, it is important to replace it on time, otherwise there is a high probability of a more serious breakdown, the repair of which is comparable to the purchase

stator
If, when turned on, the disk starts to gain momentum and accelerates too much, there is definitely a turn circuit on the stator winding. Stator repair is one of the most serious breakdowns and requires appropriate skills.If you are not confident in your abilities, then it is better to entrust it to professionals or use the services of a repair shop.

We begin repairing the stator of the grinder by cutting off the frontal parts of the winding, the remnants of which we take out. Next, we make a new winding using a template sandwiched between two large plates on an axis that can be inserted into an electric drill. The main thing is to achieve an identical number of turns made with the proper density and withstand the thickness of the wire. We insert two coils into the stator housing, draw conclusions from the same winding wire, insulating with flexible tubes of the appropriate diameter.

Reducer
In models with a power of up to 1100 W, spur gears mounted on an anchor are usually used, but angle grinders with more power, for example, by 1500 W, require helical gear wheels. Both variants have a conical shape, since the axis of the gearbox rod intersects with the armature shaft, and transmission is possible only by angular engagement of the teeth.
As a rule, the repair of the grinder gearbox consists only in the replacement of gears. If the disk gear is broken, then it will be very difficult to remove it for replacement; this assembly is best fixed in the gearbox.

speed controller
Almost all modern models of drills, jigsaws, screwdrivers have a speed control. But not all grinders (grinders) are equipped with such a mechanism. In principle, a regulator is not needed for cutting metal with a cutting stone, but it is simply not replaceable for grinding. The proposed circuit of a homemade regulator is very simple and reliable. There are not many parts and they are not expensive. If you already have an angle grinder without a regular speed controller, then you can easily improve it.

You can also assemble it separately in a box with a socket and use it as a carrier with a power regulator. And you can immediately assemble the regulator in the grinder case and bring out the resistor knob.

The power tool must not be allowed to work for a long time under load at a significantly reduced speed (this can be determined by ear) compared to idle speed, and even more so, the tool must not be clamped (blocked), otherwise it will burn out within a few seconds.

After working at low speeds, do not immediately turn off the power tool. To prevent local overheating, it is necessary that it work for some time (more than 1 min.).

It is important to strictly observe the terms for replacing (adding) lubricant and its quantity indicated in the operating instructions.

Video (click to play).

Prevention consists in the complete or partial disassembly of the tool, cleaning, lubrication and replacement (if necessary) of some parts.
Timely replacement of relatively cheap parts that wear out quickly will allow you to save more expensive durable components, which in the end will lead to savings in the operation of the tool, eliminate premature repairs and greatly extend the life of the tool.