Do-it-yourself grinder repair

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

Have you noticed that the tool always breaks the minute you need it most? And what to do? There is no time to run to the repairmen, and maybe not even run. Maybe try to repair it yourself? It was not the gods who did it. Let's take a grinder for a sample.

Any, even a very complex mechanism, consists of large and small parts. The Bulgarian is no exception. Its main nodes and details:

Frame;
Stator;
Rotor;
Reducer;
Connecting wire;
Switch.

The assemblies can be divided into electrical and mechanical. Electric - stator, rotor, connecting wire. Mechanical - housing and gearbox. Of course, there is also a button, a fork, brushes.

Vala;
Windings;
Contact collector;
Brush holder and brushes;
Ball bearings.

For repairs, you will need a minimum amount of tools - an ordinary screwdriver with a special crown, pliers, a multimeter, electrical tape, thick grease for gearboxes. If we have all this, then you can start repairing yourself.

To simplify the task, troubleshooting and repairs must be performed systematically. There is no need to rush to disassemble the instrument. First, let's define the type of malfunction. The most important trouble is that the grinder does not turn on. What you need to check:

Serviceability of the power outlet;
Serviceability of the connecting plug;
The integrity of the connecting wire.

If these elements are in good order, then we inspect the contact brushes. Brushes are used to transfer the supply voltage to the contacts of the electric motor collector. The armature windings are soldered to these contacts. If one of the brushes does not contact or is broken off altogether, then the electric current will not flow to the winding and the grinder will not want to work.

Video (click to play).

In order to inspect the condition of the brushes, you must:

Find two coaxial threaded plugs on the body;
Unscrew them carefully;
Remove the brushes.

The brushes are spring loaded, so you should try not to lose the springs. The removed brushes must be the same size. There will be some wear on them, but there should be no chips or transverse cracks that could break contact.

If the brushes are in good condition, you will have to inspect the engine armature. This node is only called an anchor, but in fact it has absolutely nothing to do with an anchor. This is the central shaft of the engine, on which the winding and the collector crown are located. Sometimes, due to heavy loads, a strong spark occurs between the brushes and the collector contacts. As a result, the copper contacts are covered with a layer of oxides and the current does not pass to the winding.

What needs to be done to put the anchor in order? We need to take the usual white rubber band, which is used by draftsmen and art lovers. Use the corner of the elastic to rub the contacts. The oxide film should be cleaned and shine with a copper sheen.

If this operation did not give results, then it is necessary to open the grinder's case and inspect the condition of the internal wires, the phase-shifting capacitor and the winding. The winding should have an even color of the varnish with which the winding wire is covered. Darkening or blackening of the wire or its sections indicates a short circuit in the winding. It is difficult to fix this malfunction with your own hands; you will need to replace the anchor.

The task of the gearbox is to transfer the rotation of the electric motor shaft to the grinder's disk. Moreover, since we have an angle grinder, we also have an angle gearbox. To inspect it, you must:

Image - Do-it-yourself assault grinder repair

Remove the disc, if installed;

Remove the protective cover;

Unscrew the four screws on the gearbox housing.

After that, the gearbox must come out of the housing.There are few faults here:

Breakage or significant wear of the gear teeth;
Shaft breakage;
Lack of fixation of gears on shafts.

Defective gearbox elements must be replaced. Replacing a gear is not difficult. The gearbox is then lubricated with a good layer of grease and reinstalled.

The stator is the part of the electric motor that is rigidly fixed in the housing. It is designed to create an electromagnetic field in which the armature rotates. Image - Do-it-yourself assault grinder repair

The main malfunction of the stator is a break in the winding or its strong overheating. Why is overheating dangerous? When the winding wires overheat, the protective insulating varnish that covers them also overheats. Violation of the varnish insulation leads to a short circuit of the winding turns.

Even the closure of one turn of the winding completely disables the grinder. The winding immediately begins to overheat and smoke. The shaft rotates slowly or stops rotating altogether.

To repair the stator, you will have to change the windings to new ones or rewind. But rewinding the stator is not a procedure for beginners.

Any instrument must be treated with care. The design of a modern instrument asks for respect by its very appearance. The plastic case, although it has a margin of safety, is shock-resistant. Try to use special soft stands for any instrument. Image - Do-it-yourself assault grinder repair

The housing has ventilation holes through which the motor is cooled. During operation, especially when cutting strobes, a lot of construction dust gets into the body. Therefore, after performing dusty work, it is necessary to blow out the inside of the grinder with compressed air. The outer surface of the tool must be wiped with a rag and dirt removed.

After completing the work, you need to remove the disc. This relieves stress on the drive assembly, and at the same time you can inspect and assess the condition.

Do not use a disc with a diameter that exceeds the size established for this grinder. A large diameter disc can be compared to a large lever, with which you try to destroy the mechanism of a tool or burn its electrical windings. In addition, it is not possible to install a protective cover.

After work, the electrical wire must also be wiped clean, remove dirt, and especially oil. The wire must be carefully wound onto a reel or at least onto the grinder's body.

Many power tool users have the bad habit of pulling the plug out of the socket by the connecting lead. Because of this habit, the wire breaks, the socket gets loose. This applies more to people who are sloppy and lazy by nature.

Avoid the possibility of water getting inside the grinder. When working in an open area, have a plastic bag or piece of polyethylene handy to cover the tool at all times to protect it from rain or snow.

In order for the grinder to serve for a long time and reliably, it is necessary to periodically open the gearbox, clean it and apply new grease.

Attention to a tool always has a beneficial effect on its long-term performance and your safety. And this should not depend on the brand of the grinder - it is Makita, sparka or our domestic sample. Image - Do-it-yourself assault grinder repair

Do-it-yourself grinder repair is a completely solvable task. The main thing is not to rush, to understand the structure, remember all the circumstances under which it broke down, determine what could have worn out during operation, make diagnostics and start repairing it.

Angle grinder (angle grinder) is called a grinder. The name of the instrument is due to the fact that it was produced by the Eltos-Bolgarka plant in Plovdiv. It is designed to perform work on grinding or trimming hard material:

Performs well sharpening of the tool.

Nowadays, a grinder is a very necessary tool, so almost everyone has it.

There are grinding machines of different power: from 500 W to 2500, depending on the thickness of the wheel - 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 disc 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 there are malfunctions in the mechanism that 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 - a part of an electric motor that rotates during operation and is speed-controlled, also called an anchor;
collector - the place on the rotor where the control winding wires are located;
brushes - parts that serve as conductors of current from the cable to the collector winding;
reducer - a mechanism that acts as a drive from a rotating rotor to a rotating disk, consists of a spindle, a bearing, two gears (large and a shaft gear);
stator - the part of the electric motor in which the rotor works;
grinder cooling impeller;
start button;
network cable with electric drive;
protection casing;
grinder body;
additional handle.

All these details can be divided into two parts:

How to disassemble a grinder? Not so difficult process. This does not require special knowledge, but everything must be done carefully and carefully. Each owner needs to know how to disassemble any working tool, because from time to time it needs to be cleaned internally from dirt and trapped dust, and its durability depends on it.

At the present time on the market, you can choose for yourself a different type of grinder, which differ in performance, size, quality. Manufacturers are also different. Whichever model of grinder you buy, everyone has the same assembly model.

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

Having prepared a screwdriver, you can start disassembling:

We unscrew the screws from the body and remove one side of the product.
Remove the nut that holds the disc, unscrew the bolts securing the protective casing.
We remove the brushes.
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 put the grinder back, put everything in place in the reverse order and fasten it.

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

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

The grinder 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 no current flows into the product.

The cable and plug are intact, but the drive does not work. You need to check the start button. It is easier to repair the grinder switch by purchasing a new button and replacing it. Since it rarely needs to be repaired - basically, the plastic rod of the switch breaks inside. If you want to experiment, you can disassemble it by numbering the contacts, and put everything back together in place so that after assembly does not happen a short circuit.

The above parts are intact and the angle grinder doesn't want to work - so it's time to check the brushes. Perhaps it's time to change them in the grinder. The brushes are constantly heated from work, so they wear out quickly and more often than other parts need to be replaced, and in pairs.

Having excluded 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 and require additional knowledge. This happens if:

the body is deformed;

one of the bearings is seized;

the armature or stator does not work;

the teeth of the gear wheel of the reducer are broken or worn out;

the collector is out of order;

the sensor of the control electronics does not show signs of life.

If it is determined that a malfunction has 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 to the bushings. If the teeth are partially worn out or the shafts are wobbling, they must be replaced immediately.

The most common breakdowns

Grinder malfunctions happen quite often. Everyone who works with this tool knows about this. What goes wrong most often?

Just one awkward pressing of the spindle lock button while the disc is rotating will break it. It can sometimes be broken if used to remove a jammed disc. To prevent this from happening, you need to use an open-end wrench inserted into the special holes near the place where the disc is attached.

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

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

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

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

The weakest link, and not only among the grinders, are the bearings. A high speed will quickly wear out the mechanism. The good news is that changing the bearing is easy. Replacing a sprinkled bearing at a grinder must be done in time so that a breakdown does not happen that cannot be fixed.

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

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

LBM, the power of which is less than 1100 W, are usually equipped with spur gears. They are located on the stator. Bulgarians with more power have helical gears. Each of the options has a conical shape, the rod of the grinder's gearbox crosses with the stator shaft at an angle.

Repair of the grinder gearbox mainly consists of replacing the gears. If the disc gear breaks, it is difficult to replace it because it is very firmly fixed. It is easy to disassemble the gearbox:

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

The speed regulator is not present on 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 suddenly it 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 of the grinder is not always feasible. If suddenly something does not work out or everything is not clear, it is better to contact the service center.

Before it completely breaks down, the angle grinder signals the beginning of a malfunction.

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

the brushes began to spark too much;
the grinder is heated during work;
the motor hums inside the case when the tool is turned on;
the vibration of the body has become much greater during work;
the grinder's gearbox is bursting inside;
you hear the sound of a creak of bearings during spin-up or periodic wedging when the rotor shaft rotates;
The angle grinder has smoked, or an uncharacteristic burning smell emanates from it.

In order not to buy a new grinder, you need to be careful about 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 instrument needs good care, then it will work properly for a long time.

Any grinder will warm up during operation, but in order to postpone the repair of angle grinders for a long time, you must adhere to some rules in the work:

Do not overload the tool to avoid overheating and smoke.
Do not put pressure on it while working.
Timely clean and lubricate the necessary parts inside the case.
If malfunctions are noticeable, discontinue operation and inspect for malfunctions.
Replace wearing parts in a timely manner.
If the grinder smokes, immediately stop working and do not turn it on again.
Do not use the tool when processing wood-type material.
Hold the grinder firmly during work so as not to drop or damage.

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

Any power tool can fail over time. This usually happens due to a violation of the rules for its operation. The Bulgarian is no exception. If you have such a nuisance, do not panic and immediately call the wizard, because in most cases you can fix the problem yourself.

Figure 1. The device of the grinder.

To do this, you need to know the basics of electrical engineering and understand a little about the design of grinding machines. Next, we will consider how to repair the grinder with your own hands.

To understand how an angle grinder works, you first need to familiarize yourself with the principle of operation of this tool. With the help of electricity, the engine works, which, through a special gear wheel, transmits the rotational movement to the shaft. At its end, a grinding or cutting wheel is fixed.

The high quality of work carried out with the grinder will depend on the number of revolutions of the cutting blade in 1 minute. With a professional power tool, this value can reach 10,000 rpm and more.

First of all, if a grinder breaks down, it should be disassembled and thoroughly cleaned; in most cases, the tool starts to work.

The layout of the grinder may differ slightly from different manufacturers, but the main parts are the same for all models (Fig. 1):

two-piece body;
electric motor of a certain power;
reducer;
electrical part.

The body is made of impact-resistant plastic. Its main task is to hold all the components in place and transfer the forces applied by the operator to the cutting element.

The electric motor drives the drive gear of the reducer, which rotates the driven gear, on the axis of which the disk is located. The reducer consists of gears through which the axis of rotation is rotated 90 °. Due to the use of gears of different diameters, the optimal speed of rotation of the cutting blade is achieved.

Before you repair the grinder, you need to prepare tools and materials that may be needed during the repair work:

tester;
screwdriver;
spanners;
knife;
tweezers;
sandpaper;
insulating tape;
grease;
alcohol;
rags.

The main principle that must be adhered to when repairing any power tool is that one should move from simple to complex, that is, the sequence of repair work must first exclude elementary malfunctions.

When an angle grinder fails, the first step is to remember the circumstances under which the breakdown occurred. This will most likely help to establish the cause of the breakdown, which will allow for a successful repair of the grinder.

The most common breakdowns of a grinder are open or short-circuited turns in the stator or armature windings.

The most vulnerable point of the grinder is the electrical part, the breakdown of which occurs most often. It can burn out from excessive loading of the tool during work, from water entering the device, from power surges, etc.

The mechanical part does not like abnormal operating modes, poor or untimely maintenance of bearings and gear elements of the gearbox, falling of the tool on the floor. Therefore, before you repair the grinder, you must thoroughly clean its body and trigger. If this does not help, then the grinder will have to be disassembled for further inspection and repair.

Very often a situation arises when the grinder suddenly stops working. The first thing to do in this case is to disconnect the device from the power source and manually rotate the disc. If it does not turn or turns very tightly, then you need to completely disassemble the tool and inspect its mechanical part. If the disc scrolls easily, then this means that power is not supplied to the brushes of the electric motor. This may be due to a failure of the power cord or the "Start" button.

The first step is to inspect the supply cable for integrity. Very often it bends at the point of its entry into the grinder's body. To eliminate such a breakdown, it is necessary to remove the cover from the handle of the device, and then ring 2 wires with a tester. If a break is found in any place, then it is better to replace the cable with a new one.

It is better not to do twisting, because in the place of twisting the wire will bend again after a while.

Grinder anchor device.

When the handle cover is open, you can immediately see the condition of the brushes on the armature collector. If they are worn out, they should be replaced. To do this, open the 2 windows of the brush holder and, by bending the spring, replace it. New brushes should be the same as the old ones.

Carbon deposits can form on the collector plates, making it difficult to apply the brushes evenly. In this case, the carbon deposits should be removed. To do this, take tweezers and wrap cotton wool around it. After that, take out the brushes, wipe them and the collector with alcohol, and then put the brushes back.

If, after these operations, the grinder still does not start, this means that the cause of the malfunction lies in the start button, which should be repaired. For repair, you need to disassemble the trigger. In this case, it is recommended to mark the removed elements, which will save you from incorrect reassembly. The serviceability of the button must be checked with a tester. If it turns out that it is defective, replace it with a new one.

Sometimes a situation arises when extraneous noise is heard during the operation of the grinder.To eliminate this problem, open the gearbox by unscrewing the 4 fixing screws. If the gear is worn out, replace it with a new one.

If the speed on the tool has decreased and strong sparking is visible from under the brush, then the armature insulation is broken. It is necessary to dismantle the old anchor and replace it with a new one. Such repairs are not always cost-effective, since the anchor is quite expensive.Another weak point of the grinder is the bearings. This is due to the fact that the tool often has to work in dust, and the high rotational speed implies their rapid wear. Bearing wear is not the worst failure, because they are easy to change. The main thing is to replace them on time, as otherwise you may have more serious problems.

use the tool only for its intended purpose;

during operation, do not neglect the main technical characteristics of the grinder indicated by the manufacturer;

do not block the power tool;

carry out timely lubrication of the mechanical elements of the device, while using only high-quality lubricants;

carry out maintenance according to the technological maps for equipment and to the fullest extent.

Turn-to-turn closures stator and rotor windings. You will need to rewind the coils or replace these parts with new ones.

If you notice strong sparking when turning on the angle grinder in the place where the collector is located, then the reasons for this trouble may be as follows.

To diagnose the electrical part of the angle grinder, as well as eliminate mechanical damage to 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 LBM motor housing.

Pull lightly on the gear housing and detach it from the housing. 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. Removing the cover reveals the gears of the reducer.

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

In order to remove the bearing from the armature, it is recommended to use a special puller. Otherwise, the shaft could 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 instrument, the repairmen of electrical equipment 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 yourself.

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

The first step is to checking electrical cable and plug at its end. If it is collapsible, then unscrew it and check the reliability of the contacts. Otherwise, you will have to disassemble the grinder (remove the cover of the device) and “ring” the cable with a tester, and also make sure that the current goes 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), indicates switch malfunctions... The button cannot be repaired. It must be replaced with a new one, but first mark the removed contacts in order to connect them correctly in the future. If the contacts are incorrectly connected, the motor winding may burn out.

If during the check it turned out that both the cable and the start button are in good order, but no current flows to the brushes, then it is necessary to make 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 the current flows to them, the rotor and stator should be checked for shorts and breaks.

The rotor of the electric motor may have the following malfunctions: interturn short circuit and wire breakage at the contacts of the lamellas. You can check the grinder's anchor with a multimeter: the device is switched to the resistance change mode, the value is set to 200 Ohm, and the resistance between two adjacent lamellas is measured with the help of 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. The detection of other resistance values during the “ringing out”, as well as the detection of an open circuit, indicates a malfunction in this coil. In this case, the grinder's anchor will need to be repaired.

Usually, the rupture of conductors occurs at the junction with the winding. Inspect the places where the coils are connected to the lamellas, make sure that the contacts are soldered securely.

If you do not have a measuring device, then you can check the rotor by using 12 V light bulb and battery... The power should be between 30-40 watts. The check is done as follows: apply a voltage of 12 V from the battery to the plug of the angle grinder, connect a light bulb to the break of one wire, start rotating the spindle of the angle grinder. If the winding is in good condition, the light will burn evenly, without blinking. With an inter-turn closure, the degree of incandescence of the spiral of the light bulb will change. In this case, repairing the grinder's anchor 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, it is recommended to entrust this operation to specialists. But the best way out of the situation would be to replace the anchor on the grinder with a new one.

If the light does not light up when testing the rotor, this indicates an open in the stator or a short 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. The values you need set to 20-200 Ohm 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, it means that there has been a breakdown to 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 serviceable. If the device shows an open circuit on one winding, it means that you will need to rewind the stator or replace the part 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 a specialist who is professionally engaged in motor rewinding.

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.