Do-it-yourself grinder repair

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

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.

Video (click to play).

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.

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.

Read also: Do-it-yourself jack repair

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.

Creating another creation, I needed a grinder.Having taken her into the light of day, it turned out that she was not half dead. We take care of repairs at home.So, we have a Chinese grinder. I got it, though cheap, but still a pity to throw it away. Due to intensive use, the following symptoms appeared: when turned on, noise increased, some uncharacteristic rattling appeared, power decreased, and then jamming began.We start to disassemble. Remove all screws from the coverApparently, the engine seat was smashed from work. And when voltage is applied, the rotor warps and wedges.We take dimensions from the seat.We cut out the gaskets from the pressboard. We place on one side of the casing.Note the position of the bushings. This is very important, otherwise you will suffer during assembly.Carefully, so as not to damage the brushes, we take out the engine.Insert the gasket symmetrically. We carefully collect everything back. Pay attention that the bushings sit in the grooves. We put on a jacket. Tighten with screws. We check.Changes for the better are already being felt. The motor rotates the shaft without problems. No jamming is observed. We assemble and fix the sanding pad.Check again - great! Now you can keep creating! Image - Do-it-yourself grinder repair

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Couldn't parse DWT. The eccentric was not filmed. I was afraid to break it, I wanted to carry it in for repair. But after looking at the pictures in the article, I took a chance. With brute force and such and such a mother, he removed the eccentric, and the rest went by itself. The bottom bearing was broken. ATP for the article.

Good article. Cognitive. Well done.

Thanks! It was helpful to read. Just used this for the first time today.

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In modern finishing works, various construction tools are used. Grinding machines are no exception.

The device of the grinding machine.

Due to frequent use, any tool can fail. And in order to repair the grinder with your own hands, you need to have an idea about its components and possible causes of failure. Since the angle grinder is the most in demand, subsequent repairs will be considered on its example.

According to the design and external characteristics, such a machine is a grinder, as it consists of the same parts.

protective cover;
ventilation hole;
push button switch;
side handle;
spindle lock.

Repair of the grinder should be done carefully and slowly, since the consequences of repairing power and electronic components can turn a minor breakdown into unsuitability of the device.

It will take not so many tools to repair the grinder:

A grease-caked bearing is a common cause of grinder breakdowns.

The machine has internal components and mechanisms, the device of which also needs to be sorted out;

When repairing, it is recommended to rely on the layout and electrical diagrams, to have on hand the instructions that were attached to this particular model of the grinder. But such instructions do not go to many models, in this case it is most reasonable not to carry out repairs on your own, but to seek help from the service.

When repairing any equipment, the sequence must be followed. Simple faults are:

First of all, the electric brushes are checked, since there is a possibility that they are not getting current from the power supply.

To replace the bearing, you need to remove the horseshoe retainer.

Specifically, the problem may be in the power plug or in the wire itself, and the Start button may also not work. To fix the problem, the case is disassembled and the wiring is called using a break tester. In frequent cases, the problem is in the wiring, and after replacing it, the grinder will work again;

After checking, the wires and the plug are intact, and the device does not show any working signs. In this case, the starting block is disassembled, and the elements to be removed are marked, since if they are incorrectly connected during assembly, this may lead to the winding burning or the armature may jam. The button is replaced with a similar model;
The start button and power cable work, but the machine refuses to work. In this case, it is recommended to examine the brush holder. The most common problem is the contact plates of the collector, which, after stripping, will begin to spark and even buzz. If these signs are not given, then the brushes must be replaced, since their service life is limited. If many models are made with a soldered connection of the brushes, then in this case it is necessary to solder and change as a set, since a partial replacement is not made;
After changing the electric brushes, they should be carefully examined if the wear is uneven - this is a sign of a shift in the center of gravity or internal moving parts. If such a problem occurs, it is recommended to contact a specialized service, since it is impossible to adjust the balance yourself.

Brush repair is a minor repair when troubleshooting, but more serious breakdowns are best left to specialists.

Also, to prevent malfunctions, it is recommended to follow the basic rules of operation:

unnecessarily, it is forbidden to remove the casing above the abrasive wheel, and if this is indispensable, then the tool must not be allowed to touch;

the machine must be held firmly in your hands, if the disk jams, the device may break out of your hands, in connection with this the machine can be seriously damaged and cause injury;

during the operation of the grinder, sparks are formed, it is necessary to avoid their contact with wires and similar flammable materials;

the part to be sanded is important to firmly fix.

Try not to use the grinder in the winter season on the street. While you are working, the engine heats up. The air is icy. As a result, condensation forms. Moisture is detrimental to the engine.

Always use the wheels recommended by the tool manufacturer. If the grinder is 180 mm, do not put more than 200 mm there. The larger the circle, the lower the rpm should be. You will have to remove the protection, and the speed will be exceeded. Vibrations and vibrations will increase. As a result, the circle will break into pieces.This is fraught not only with serious injuries. The gearbox bearing is broken, the gears are worn out.

If you actively use the grinder, then you are a good master. It will not be difficult for you to understand the device of the tool and repair it with your own hands. Find the problem first and determine which parts to check. Repair the grinder carefully, without haste, so that a minor breakdown does not turn into a major one.

The anchor of the grinder is subjected to thermal, mechanical and electromagnetic loads more than all nodes. Therefore, it is a common cause of tool failure, and as a result, it often needs to be repaired. How to check the anchor for performance and repair the element with your own hands - in our article.

An angle grinder motor armature is a conductive winding and a magnetic circuit into which a rotation shaft is pressed. It has a drive gear at one end, a collector with lamellas at the other. The magnetic circuit consists of grooves and soft plates coated with varnish for isolation from each other.

In the grooves, according to a special scheme, two conductors of the anchor winding are laid. Each conductor is half a coil, the ends of which are connected in pairs on lamellae. The beginning of the first turn and the end of the last are in the same groove, so they are closed to one lamella.

Types of anchor faults:

Breakdown of insulation to ground is the short circuit of the winding on the metal housing of the rotor. Occurs due to the destruction of insulation.

Soldering of collector conclusions.

Uneven manifold wear.

If the armature is faulty, the motor overheats, the winding insulation is melted, the turns are short-circuited. The contacts connecting the armature winding to the collector plates are soldered. The power supply is cut off and the motor stops working.

visually;
multimeter;
light bulb;
special devices.

Before taking the device for diagnostics, inspect the anchor. It may be damaged. If the wiring is melted, the burnt insulating varnish will leave black marks or a peculiar smell. You can see bent and crumpled coils or conductive particles, such as solder residue. These particles cause a short circuit between the turns. The lamellas have curved edges, called cockerels, to connect with the winding.

Due to the violation of these contacts, the lamellas burn out.

Other manifold damage: Raised, worn or burnt plates. Graphite from brushes can accumulate between the lamellas, which also indicates a short circuit.

Set the resistance to 200 ohms. Connect the probes of the device to two adjacent slats. If the resistance is the same between all adjacent plates, then the winding is working. If the resistance is less than 1 ohm and very close to zero, there is a short circuit between the turns. If the resistance is two or more times higher than the average, then there is a break in the turns of the winding. Sometimes, during a break, the resistance is so high that the device goes off scale. On an analog multimeter, the arrow will go all the way to the right. And on digital it will not show anything.

If you don't have a tester, use a 12 volt bulb up to 40 watts.

Take two wires and connect them to the lamp.

Make a break on the negative wire.

Apply voltage to the wires. Attach the ends of the gap to the collector plates and scroll it. If the light is on without changing the brightness, then there is no short circuit.

Perform a short to iron test. Connect one wire to the lamellas and the other to the iron of the rotor. Then with a shaft. If the light is on, then there is a ground breakdown. The winding closes to the rotor housing or shaft.