DIY repair of a small grinder

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

As you know, nothing is eternal and even the tools of brand manufacturers break, not to mention the so-called “consumer goods”. And the grinder (angle grinder) is no exception. By the way, they began to call angle grinders "grinders" at the time of the Union, because then this instrument 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 grinders, but the principle of operation and device is 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.

Grinder device relatively simple. The basis of the tool is its body, inside which there is an electric motor, a starting device and a gear transmission to the spindle, on which various attachments are attached.

The body is made of strong impact-resistant plastic. Depending on the power, there are different dimensions and shapes 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 could be a gearbox. 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 leads to a decrease in the number of revolutions on the output shaft of the gearbox. Correctly selected rotational speed and wheel diameter are the key to the most efficient tool performance.

Video (click to play).

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

The overload clutch acts as a limiter in the event of a sudden reactive torque. On the other hand, when the disc is jammed in the material, the grinder itself begins to rotate abruptly, which can lead to injury to the worker. This clutch does not allow such rotation.

The electric motor consists of a stator and a rotor as standard. The stator is located in the guide lugs of the plastic housing 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 required to transfer voltage to the rotor through the manifold 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 an aluminum alloy.

The gearbox housing of the 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 planes of location during operation.

The reducer consists of two gears, with the help of which the direction of the output shaft changes 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.

The grinder suddenly stopped working.
The first thing to do is disconnect physically from the network and manually rotate the disc. If the disc does not spin or is spinning very tightly, immediately disassemble the instrument for visual inspection. If it turns 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 an ordinary tester, or in some other way, for the presence of 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 mechanism, and it is advisable to mark the removed contacts - if they are subsequently connected incorrectly, then the winding may burn out or the anchor may jam. Repair of the trigger mechanism is not often possible - 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 order, the grinder does not work.
Check brushes and brush holders. There may be a breakage 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. Eliminate open or replace brushes.

Then there are more serious malfunctions, 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 the control electronics;
- failure of the collector;
- deformation of the body;

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

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

Chipped gear teeth.
Usually they arise due to jamming (in such a situation, tool breakage is not the worst thing that can happen). A rumble in the gearbox is a sign of a malfunction. 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 by 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 which are forced to rest in the sand or on the ground: the sucked-in dust grinds off the winding. However, you can ditch the motor without dust - by strong overloads, especially if the tool is low-power. Therefore, in small Bulgarians, not only the anchor, but also the stator often burns out. Small 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 in place of the ventilation slots in the housing helps a lot to protect the tool.

Bearings.
Another sore spot of the Bulgarians (as well as other twisting power tools). Few machines stand out with strong immunities against dust, and high rpm suggests rapid wear. In general, bearings are not the worst failure, they are easy to change. However, it is important to make a replacement on time, otherwise there is a greater likelihood of a more serious breakdown, the repair of which is comparable to a purchase.

Stator
If, when turned on, the disk starts to gain speed 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 more expedient to entrust it to professionals or use the services of a repair shop.

We start repairing the grinder's stator 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, which 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 case, we make 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 are usually used, mounted on an anchor, but grinders with a higher power, for example, 1500 W, require helical gear wheels. Both options are tapered, since the axis of the gear stem intersects with the armature shaft, and transmission is possible only by angular engagement of the teeth.
As a rule, repairing the grinder's gearbox consists only in replacing the gears. If a disk gear wheel breaks down, it will be very difficult to remove it for replacement, this unit is best fixed in the gearbox.

Speed ​​regulator
Almost all modern models of drills, jigsaws, screwdrivers have a speed controller. But not all grinders (grinders) are equipped with such a mechanism. In principle, a regulator is not needed for cutting metal with a cut-off stone, but for grinding it simply cannot be replaced. The proposed scheme of a home-made regulator is very simple and reliable. There are not many parts and they are not expensive. If you already have a grinder without a standard speed governor, then you can easily improve it.

Can be assembled separately in a box with a power outlet and used as a carrier with a power regulator. Or you can immediately assemble the regulator in the grinder body and remove the resistor handle.

The power tool must not be allowed to operate under load for a long time at significantly reduced speeds (this can be determined by ear) in comparison with idle speed, and even more so, clamping (blocking) of the tool must not be allowed, otherwise it will burn out within a few seconds.

Do not turn off the power tool immediately after operating at reduced speed. To prevent local overheating, it needs to run for some time (more than 1 minute).

It is important to strictly observe the intervals for changing (adding) the lubricant and its quantity specified in the operating instructions.

Prevention consists in 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 preserve more expensive durable components, which ultimately will lead to savings in tool operation, eliminate premature repairs and significantly extend the life of the tool.

Image - DIY repair of a small grinder

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

Image - DIY repair of a small 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:

  1. We unscrew the screws from the body and remove one side of the product.
  2. Remove the nut that holds the disc, unscrew the bolts securing the protective casing.
  3. We remove the brushes.
  4. Disconnect the wires from the engine.
  5. We unscrew the bolts that secure the gearbox inside, and very carefully remove it, and the rotor is also removed with it.
  6. We unscrew the bolts that hold the stator and remove it.
  7. 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:

  1. 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.
  2. 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.
  3. 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.

Image - DIY repair of a small grinderThe 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 must be identical in the number of turns, with the same density, and made of wire of the same thickness as the previous one.

Image - DIY repair of a small grinder

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:

  1. Do not overload the tool to avoid overheating and smoke.
  2. Do not put pressure on it while working.
  3. Timely clean and lubricate the necessary parts inside the case.
  4. If malfunctions are noticeable, discontinue operation and inspect for malfunctions.
  5. Replace wearing parts in a timely manner.
  6. If the grinder smokes, immediately stop working and do not turn it on again.
  7. Do not use the tool when processing wood-type material.
  8. 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.