Schematic diagram of the grinder. How to make a speed controller for an angle grinder with your own hands Electrical diagram of a Makita angle grinder

(angle grinders), commonly known among Bulgarians, have a speed regulator.

The speed regulator is located on the body of the angle grinder

Consideration of various adjustments should begin with an analysis of the electrical circuit of the angle grinder.

simple representation of the electrical circuit of a grinding machine

More advanced models automatically maintain rotation speed regardless of the load, but tools with a manual disk are more common. If a trigger-type regulator is used on a drill or electric screwdriver, then such a regulation principle is impossible on an angle grinder. Firstly, the features of the tool require a different grip when working. Secondly, adjustment during operation is unacceptable, so the speed value is set with the engine turned off.

Why adjust the rotation speed of the grinder disc at all?

When cutting metal of different thicknesses, the quality of work greatly depends on the speed of rotation of the disk.
If you are cutting hard and thick material, you must maintain maximum rotation speed. When processing thin sheet metal or soft metal (for example, aluminum), high speeds will lead to melting of the edge or rapid soaping work surface disk;
Cutting and sawing stone and tile at high speed can be dangerous.
In addition, the disk, which rotates at high speeds, knocks small pieces out of the material, making the cutting surface chipped. And for different types stones, different speeds are selected. Some minerals are processed at high speeds;
Grinding and polishing work is in principle impossible without adjusting the rotation speed.
By setting the speed incorrectly, you can damage the surface, especially if it is a paint coating on a car or a material with a low melting point;
The use of discs of different diameters automatically implies the presence of a regulator.
Changing a disk Ø115 mm to Ø230 mm, the rotation speed must be reduced by almost half. And it’s almost impossible to hold a 230 mm disc rotating at 10,000 rpm in your hands;
Polishing stone and concrete surfaces depending on the type of crowns used, it is produced on different speeds. Moreover, when the rotation speed decreases, the torque should not decrease;
When using diamond discs, it is necessary to reduce the number of revolutions, since their surface quickly fails due to overheating.
Of course, if your grinder works only as a cutter for pipes, angles and profiles, you won’t need a speed controller. And with the universal and versatile use of angle grinders, it is vital.

Owners of power tools are well aware that any equipment requires periodic maintenance. Some components require lubrication, others wear out and must be replaced. But most often, craftsmen operate the device until the parts begin to spill out of the body. And then it is necessary to take emergency measures to restore the normal operation of the instrument. How can you find out what’s broken, check the grinder’s functionality and carry out repairs yourself?

What is angle grinder used for and how is it designed?

The angle grinder (angle grinder), or “grinder”, has firmly entered the everyday and industrial life of not only the craftsman, but also the common man who likes to comfortably solve plumbing and carpentry tasks. The popularity of this power tool is due to its simplicity, versatility and multifunctionality of use.

With the help of various additional attachments, the grinder can cut metal, grind various surfaces, clean them from rust or old paintwork. The angle grinder's arsenal includes functions such as sharpening cutting tools, gating concrete walls, cutting ceramic tiles or stone.

The device of the grinder

Structurally, the angle grinder is an electric motor with a power of 500 to 2000 W, which converts power electric current into rotational motion. A planetary gearbox, consisting of two main gears with a straight or bevel gear, serves the same purpose. The rotation of the spindle of the working shaft is carried out in direct transmission mode, the speed is determined by the ratio of the number of gear teeth. Some grinders are equipped with an electronic unit soft start motor and speed control.

Electric motor type - asynchronous, single-phase. The electromotive force arises when the rotor winding interacts with the magnetic field of the stator, which is fixedly fixed in the housing. Thanks to the angular transmission of torque, the level of safety during operation is significantly increased. If the disk jams in a viscous material, the tool body does not rotate reactively, which prevents possible injury to the operator.

Many have experienced in their own practice the phenomenon of reactivity when operating an electric drill. When a drill bit jams, for example, in hard wood, the body of the device begins to forcefully rotate in the opposite direction, is torn out of the hands and can lead to injury or even disfigurement.

Diagnostics of malfunctions in the operation of angle grinders

Signs of an angle grinder malfunctioning for a sensitive ear and a keen eye appear long before the actual failure of the tool. Before it completely breaks down, the grinder usually starts giving distress signals. It could be:

increased vibration of the housing during operation;
excessive sparking of commutator brushes;
uterine humming of the engine when turned on;
cracking of the gearbox due to broken teeth or dried out gears without lubrication;
jamming of the rotor shaft rotation bearings or their piercing creaking during acceleration;
a specific smell or even smoke emanating from the angle grinder body.

To save the grinder from a large and expensive repairs, you should be attentive to the technical condition of the tool and promptly respond to changes in its operation.

If the first symptoms of improper operation appear in the grinder, it is necessary to urgently diagnose the device and find the cause of the problem. To do this, you need to check two main systems of the device - electrical and mechanical.

Electrical check

The electrical part of the angle grinder consists of:

electric motor;
power buttons;
electronic control unit for start and rotation speed.

The electric motor, in turn, is divided into two main parts - the stator and the rotor (or armature).

The master's task is to sequentially check all these systems and discover the causes of operational problems. To do this you will need a multimeter or tester.

Checking power circuits

First of all, you need to check the integrity of the power cord. Many troubles can occur only because there is damage in the cable and the power supply to the device is uneven. The cord must be completely intact, without signs of damage. During operation, it should not heat up or spark in places of kinks and connections with a socket or grinder. If any of these conditions are not met, the cord should be repaired or replaced.

Using a tester turned on in voltmeter mode, check the input voltage in the angle grinder; it must correspond to the passport values: 220 V. In ammeter mode, the current consumption is measured - it should not exceed 6 A.

Checking the start and control unit

Next, you should test the start button and electronic control unit. It is possible that the contact group for turning on the device has become oxidized or clogged. If the device is equipped with a soft start system, the disk should accelerate to operating speed gradually, without a sharp increase in speed. Using a multimeter, you need to make sure that the voltage is transmitted to the button when you turn on the button. electrical circuit.

If during operation of the grinder it was noticed that the brushes at the point of contact with the commutator spark excessively or the disk rotates unevenly, abruptly changing the number of revolutions per minute, then most likely the stator or armature windings are involved in this. Since the stator is less susceptible to overloads - it only creates a magnetic field, then most often attention should be paid to the rotor of the electric motor.

Rotor diagnostics - how to “ring” the armature with a tester?

To make sure the rotor is working properly, you need to “ring” it with a tester.

By setting the multimeter toggle switch to the 200 Ohm position, sequentially measure the resistance of the windings on two adjacent armature lamellas. If the resistance is the same everywhere, it means the anchor is intact and operational. If on any of the pairs of lamellas the tester shows a different value from the others, an interturn short circuit has occurred in this place. The anchor needs to be repaired or replaced.

Diagnostics of the rotor operation of an angle grinder

An interturn short circuit usually occurs when the tool overheats during operation. The insulation of the windings melts and this leads to the fact that adjacent turns consisting of copper wire come into contact. As a result, the balance of the electromotive force is disrupted and this leads to a loss of power at a certain position of the armature.

Motor stator diagnostics

If the armature turns out to be in good condition, the testing procedure should be carried out with the stator, measuring the resistance of the windings in a similar way. An interturn short circuit in the stator is characterized by bursts of increased speed of the grinder when turned on. The engine, for no apparent reason, begins to rotate “crazily” at increased speed.

An insulation defect in the stator windings can be corrected by repair or replacement. Repairs usually involve rewinding the copper wire.

A specially made template is used to rewind the stator coils. As a rule, it is made of plywood. The size of the template is determined with a margin of 10 mm for each frontal part. To prevent the wire from jumping off the plywood during winding, cheeks are attached to the sides.

Rewinding is done at home if available the necessary tool and devices. It is important to select a copper conductor with a cross-section that exactly matches the original one. The number of turns of the winding cannot be changed either.

Video: how to rewind the stator of a power tool

Checking the mechanical part of the machine

The mechanical part of the angle grinder consists of:

gearbox;
spindle locking button;
flange mounting of working tools;
bearings of the rotating rotor shaft.

To determine faults in the mechanical part of the angle grinder, it is necessary to open the gearbox housing, made of aluminum alloy. As a rule, the gearbox cover is secured with four screws, which must be unscrewed to gain access to the gear pair.

Inspection of gearbox gears

Inspection of the gearbox gear is to determine the strength of the gears, the presence of a sufficient amount of lubrication and the integrity of the teeth.

Checking the lock button

The spindle locking button is a spring-loaded steel rod that prevents the working shaft from rotating. The button is used when changing cutting discs. Failures of the locking rod usually occur when the disk jams or the electric motor is turned on with the button pressed.

Inspection of the flange for attaching nozzles

The grinder disc (or other working attachment) is secured using a flange threaded clamp. They fail extremely rarely, as they are easy to set up and operate. When inspecting, you should pay attention to the condition of the threads on the shaft; if necessary, it can be lubricated with grease, graphite lubricant or Lithol.

In practice, a situation often occurs when the flange nut is “hopelessly” tightened on the disk, and the wrenches do not help even with great physical effort. This can happen, for example, when a disc breaks. The following method will help you unscrew the nut:

A metal plate up to 2 mm thick is fixed in a vice.
The remains of the disc break and are bitten off with pliers.
The grinder's motor turns on.
With the help of a fixed plate, the remains of the disk are “crushed” from under the nut.
When the space under the flange is free, it can be easily unscrewed.

When performing this operation, it is necessary to use personal protective equipment: gloves and safety glasses - disc fragments fly at high speed and can cause injury.

Checking the rotor shaft bearings

Checking the operation of bearings on the rotor shaft involves visual inspection. A serviceable bearing should have a uniform color (without blue, which occurs when the part overheats, and lubricant leaks), and should rotate easily and without sound when turning. If this is not the case, the bearing is repaired or replaced.

General rules for repairing power tools

If, when diagnosing an angle grinder, the causes of the malfunction have been identified, repairs must be started in compliance with certain rules.

the device must be turned off from the power supply;
repairs should be carried out on a well-lit, uncluttered table or workbench;
The procedure for disassembling and, accordingly, reassembling the device must be followed.

If it is difficult to remember the location of parts inside the mechanism, it is recommended to photograph them.

When the device is disassembled, it is strictly forbidden to connect it to the electrical network.

The main causes of grinder malfunctions and their elimination

Below are the most common problems and how to fix them.

Commutator brushes burn (spark)

Sparking in the commutator is most often observed in cases when it is time to replace the carbon brushes. This usually happens after several years of using an angle grinder.

Standard brushes are designed for 7,000 hours of operation, after which they are washed.

Grinders have a simplified system for replacing brushes, so repairs are quite easy and quick:

Using a flat-head screwdriver, unscrew the two plastic caps on both sides of the casing.
Remove old brushes from their nests.
Wipe the collector with an alcohol swab, as there is carbon residue on the lamellas from the work of old brushes. You can also use tweezers with cotton wool or rags soaked in cologne.
Install new brushes into the sockets.
Screw on the plastic caps.
Check the angle grinder in operation.

Video: replacing the grinder brushes will help eliminate sparks

Grinder won't turn on

To determine the exact cause of this malfunction, it is necessary to examine the electrical circuit of the device. It is advisable to start from the outlet and end with testing the electric motor. After the location of the circuit break has been found, the flow of electric current in the tool should be restored. Most often, the cause of a break is dust or oxidation of the terminals or contacts of the start button.

Breakage of the spindle lock button

The defect is purely mechanical in nature. This happens when the circle jams or when the rod cavity is severely clogged. In this case, replacing the disk will help to produce a special flange wrench, which, as a rule, is always included in the kit of the sold tool. You can keep the shaft from turning using an open-end wrench. At the base of the flange mounting there is a specially machined turnkey plane.

Video: repairing the spindle lock at home

The engine has stopped working

If voltage is supplied to the motor, but it does not rotate, you need to check the condition of the brushes and bearings. Brushes may stick, bearings may jam.

If the brushes are sunk, they must be thoroughly cleaned and then the nests in which they are located must be blown out. Additionally, you should check the rubber seals on the covers covering the brush sockets. After all, it is on them that the insulation of the brushes and the collector from dust depends.
If the reason for the engine stopping is in the bearings, they must be removed from the rotor shaft, repaired or replaced. Sometimes flushing and lubrication is enough to ensure that the old bearing continues to function.

Angle grinder works in fits and starts, does not develop full power

The angle grinder motor operates jerkily if an interturn short circuit occurs in the rotor coils. The most common reason is irregular use of the tool, which results in overheating of the motor. Rewinding armature coils is a rather complicated and painstaking task, doomed to failure without certain skills. Therefore, if the armature fails, it is recommended to replace the entire part, along with the bearings. The value of the spare part must exactly match the value of the original.

The grinder gets very hot

Most often, the body of an angle grinder gets very hot due to improper operation of the device. Since the angle grinder is equipped with an asynchronous electric motor, an increase in the workload on it does not affect the rotation speed in any way. This can be misleading for an inexperienced user, as a result of which he continues to work without interruption for an unlimited time. But this cannot be done. The passport of each tool indicates the optimal operating time of an angle grinder under load, usually it is 5–7 minutes. After this, it is recommended to take a break of 1 minute or let the grinder idle.

When working with a tool, it is important to follow the correct order of stopping the grinder. After turning off the start button, you need to wait until the engine stops completely. If the rotating angle grinder is placed on the ground or a dusty floor, through ventilation holes Small particles of sand will be sucked in. They will get inside the engine and will erase the protective insulating layer.

Bulgarian is not gaining momentum

If the tool is equipped with an electronic shaft speed control unit, a malfunction may cause the shaft speed to “float” under load. Most likely, there is a short circuit on the board; the control unit should be replaced.

Gearbox failure

The gears of the gearbox play important role in the supply of rotational motion from the electric motor to the working tool. In addition, there is a decrease in speed and, accordingly, an increase in power. Grinders with power up to 1100 W use spur gears. If the engine power exceeds this figure, helical gears are used, which have greater fracture strength.

If you hear a crunching or grinding sound from the gearbox when you turn on the motor, the grinder must be turned off immediately. It is impossible to work with such a gearbox; this will lead to complete cutting off of the remaining gear teeth. After stopping the engine completely, you need to remove the gearbox cover to establish an accurate “diagnosis”.

If the cause of extraneous sounds is chipped teeth, the damaged gears must be replaced. In this case, the cavity of their rotation should be thoroughly cleaned of grease and metal fragments that formed from the previous mechanism. After replacing parts, you need to completely renew the lubricant inside the gearbox.

Video: how to repair and adjust the gearbox

If the grinder smokes during operation

When you are engrossed in stone processing or metal grinding, it is easy to not notice how the tool has overheated. If the work is not stopped, very soon acrid, stinking smoke will begin to emerge from under the casing. This is the armature windings burning, in which, unable to withstand the thermal load, the insulating layer melts. If you do not interrupt the work, the grinder may burn out.

If you felt bad smell, you must immediately turn off the grinder and unplug the power cable from the outlet.

You can begin disassembling the instrument only after the housing has completely cooled down and the emission of caustic fumes has stopped.

Excessive sparking at manifold

A fan of sparks flying out from under the commutator brushes usually indicates a violation of the insulation on the armature or a short circuit between the wires in the windings. In this case, you should stop working and turn off the angle grinder from the network. Next, you need to disassemble the body and examine in detail the anchor of the angle grinder. The easiest repair option is a complete replacement of the anchor.

Bearings broke

If there is something wrong with the bearings, the angle grinder vibrates and makes noise under load; the sound is dominated by a low-frequency hum. This is due to the fact that the damaged bearing begins to hum during operation. Vibration occurs from the appearance of additional play on the bushings securing the rotating shaft. This malfunction can be eliminated by replacing the bearings. To do this you need to do the following:

Remove the brushes from the brush holders.
Remove the plastic housing by unscrewing the fixing screws.
Remove the gearbox cover and disconnect the drive gear.
Remove the armature shaft together with the cooling impeller and bearings.
Using a puller, separate the bearings from the shaft axis.
Assemble the structure in reverse order.

Video: how to change a bearing on a grinder

If the grinder buzzes, but does not rotate

If the angle grinder shaft does not rotate, there are two most likely reasons, both related to the mechanical part of the tool.

The gearbox is jammed.
The bearings are jammed.

To check the versions, turn off the grinder and try to turn the tool disk manually. If the spindle does not rotate or rotates slowly, the reason does not lie in the electrical part; you need to disassemble the gearbox and look for the reason there.

If the soft start does not work

If the soft start does not work, the reason lies in a malfunction of the electronic control unit. The solution to the problem is to replace the entire block. Only a specialist with the appropriate knowledge and diagnostic equipment can disassemble the unit and look for the cause of the problem.

Preventive maintenance of an angle grinder

Unexpected breakdowns can be avoided if you regularly carry out not only visual inspections, but also Maintenance tool. The manufacturer usually indicates the prevention regulations in the passport. In order for the grinder to serve for a long time and without “surprises”, you should:

carry out tool maintenance in a timely manner;
comply with operating and storage standards;
avoid long work tool under load at reduced speed;
do not allow the working part of the tool to become pinched;
Monitor the mechanisms and promptly replace worn parts.

If the angle grinder was operating at low engine speeds, it must be kept at idle for about a minute before turning it off. This will allow the engine to recover and regulate the temperature of the windings.

Preventive disassembly, cleaning and lubrication of mechanical parts will increase the service life of the tool several times. This simple maintenance will help you avoid costly repairs.

The optimal conditions for storing an angle grinder are dry rooms, protected from sudden changes in air temperature. When storing an instrument for a long time, it is preferable to pack it in a plastic bag in a cardboard box.

All renovation work All work carried out with power tools must strictly comply with safety standards. Under no circumstances should you disassemble the housing while the device is plugged in. Containers with flammable and flammable materials should not be located near the disassembly site.

As you know, nothing lasts forever and even tools from branded manufacturers break, not to mention the so-called “consumer goods”. And the grinder (angle grinder) is no exception. By the way, angle grinders began to be called “grinder” during the Soviet Union, because at that time 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 grinders, but the operating principle and design are not fundamentally different. Therefore, having considered the device of the instrument, possible malfunctions and repair methods, they can be applied to any model of angle grinder.

The device of the grinder 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, onto 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 controller, which is designed for optimal choice revolutions, for various types of work.
Another component could be a gearbox. The gearbox is designed to create optimal conditions transmission of rotation from the electric motor rotor to the cutting or grinding wheel. In this case, the number of revolutions on the output shaft of the gearbox decreases. Correctly selected rotation speed and circle diameter are the key to maximum efficient work tool.

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

An electric motor typically 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 side of the stator there is special device, called a brush mechanism. It contains copper-graphite brushes. Brushes are necessary to transmit voltage to the rotor through the commutator 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.

Typical malfunctions of angle grinders and methods of diagnosis and repair

The grinder suddenly stopped working.
The first thing you need to do is physically disconnect from the network and manually turn the disc. If the disc does not spin or spins very tightly, immediately disassemble the tool 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 Start button mechanism. It is enough to disassemble the case and "ring" the cable with a conventional tester, or in some other way, for a break. After repairing the break or replacing the wire, the angle grinder will start working.

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. The brushes may be broken or completely worn out. The resource of these devices is usually limited to several years, of course, it all depends on the intensity of use. Repair the break or replace the brushes.

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

Breakage or licking of 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 body;

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 the 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 rattling sound 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 pairs and the gear itself and the bevel wheel. When you go to the store for gears, don’t 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 dust wears down the winding. However, you can destroy the motor without dust - by strong overloads, especially if the tool is low-power. Therefore, in small angle grinders, not only the armature, but also the stator often burns out. In small angle grinders, the electronic speed control unit also breaks down. If you use an angle grinder to cut highly dusty materials, in particular slate, putting a stocking over the ventilation slots in the body helps to protect the tool.

Bearings.
Another sore spot for grinders (as well as other rotating power tools). Few machines have strong immunity to dust, and high rotation speeds mean 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 begins to gain speed and accelerates too much, there is definitely a turn short 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.

Gearbox
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 versions 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 everyone modern models drills, jigsaws, screwdrivers have a speed regulator. 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 for grinding it is simply not replaceable. The proposed homemade regulator circuit is very simple and reliable. There are not many parts and they are not expensive. If you already have an angle grinder without a standard 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. Or you can immediately assemble the regulator in the body of the angle grinder and remove the resistor handle.

Rules for using an angle grinder and preventive maintenance

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

After working at reduced speed, do not immediately turn off the power tool. To prevent local overheating, it needs to work for some time (more than 1 minute).

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

If the noise increases during operation of the angle grinder or if its performance characteristics deteriorate, it is necessary to carry out a professional examination. service.

Prevention consists of completely or partially disassembling the tool, cleaning, lubricating and replacing (if necessary) some parts.
Timely replacement of relatively cheap parts that wear out quickly will allow you to preserve more expensive long-term components, which will ultimately lead to savings in the operation of the tool, eliminate premature repairs and greatly extend the service life of the tool.

IN household and in industrial production Often there is a need to cut and grind metal, stone or other products from hard materials. A very effective power tool for these purposes is the Interskol angle grinder UShM-125/1100E.

What is this tool?

Angle grinder "Interskol" UShM-125/1100E is an electronic device. In everyday life it is often called a grinder and is used for working with iron, stone, concrete and other materials. "Interskol" UShM-125/1100E - angular, using nozzles with a diameter of 125 mm and a power of 1100 W. It is a product of the Russian company Interskol. Working with an angle grinder is not limited to cutting. This electrical device You can also grind and polish the surfaces of products if necessary. Wide multifunctionality in application is possible due to design features and technical capabilities of angle grinders.

Grinder "Interskol" UShM-125/1100E. Design Features

Grinding and polishing work on the surfaces of concrete products is often accompanied by copious emissions of dust, which is very undesirable for power tools. Settling dust negatively affects the service life of any angle grinder. The grinder "Interskol" UShM-125/1100E is assembled in such a way that the dust generated during polishing/grinding does not penetrate inside the mechanism. This is made possible by the direction of the armature impeller, which sends air currents through the front of the gearbox.

In these corner mount the gear is carried out; they are pressed onto the spindle shaft. The entire mechanism of the angle grinder USHM-125/1100E is assembled in one housing, in the rear part of which there is a convenient handle. This grinder is a very convenient and powerful machine designed for professional use. The two-handed design (main handle + additional included) ensures comfort and convenience during operation of this power tool.

What is the grinder equipped with?

"Interskol" UShM-125/1100E has an electronic system that allows you to adjust the speed if necessary (from ten thousand per minute to three). The owner of this power tool can reduce them to the required level without worrying that the power of the grinder will also decrease. This quality, which is possessed by the Interskol grinding machine UShM-125/1100E, is especially appreciated by professional tilers. By lowering the speed, you can easily process glazed tiles and other delicate surfaces.

In addition to the electronic system, the Interskol angle grinder UShM-125/1100E contains a special soft start board, which greatly facilitates the process of operating the grinder. The presence of a smooth start of the system is especially in demand when working with heavy grinding discs and diamond attachments for stone surfaces.

What ensures reliable retention of an angle grinder?

Comfort during operation is provided by special handles - holders. Each angle grinder is equipped with them. "Interskol" UShM-125/1100E has one more handle, an additional one. Despite the fact that this electrical device is compact in size, allowing it to be held with one hand, an additional handle is included in the kit and is indispensable for work related to cutting metal.

Technical indicators

The power consumed by the power tool is 1100 W.
Voltage - 220 V/50 Hz. Power comes from the electrical network.
Speed: from 3000 to 10,000 per minute.
Weight is 2.2 kg.
The power tool is designed for a circle with a diameter of 125 mm.
The main handle is three-position.
Smooth start.
There is a function for adjusting the rotation speed.
There is a fixed spindle.

When selling Interskol, the UShM-125/1100E is equipped with:

additional handle;
a set of gaskets;
a special key for installing discs and attachments.

Advantages

One of the most reliable and durable products Russian production The grinder "Interskol" UShM-125/1100E is considered. Consumer reviews indicate good performance and high reliability of this electric tool.

Among users strengths This Bulgarian is considered:

the ability to easily rotate the gearbox 90 degrees in case of an inconvenient or unusual location of the release key;
high power;
presence of a speed controller. According to consumer reviews, the ability to reduce the rotation speed makes this angle grinder indispensable for work such as cleaning welds, removing rust or old paint With metal structures through various grinding wheels and nozzles;
the complete set with a long cord makes it much easier to carry and makes it possible to work with an angle grinder at long distances from the outlet and in other rooms;
small dimensions and weight allow the Interskol UShM-125/1100E to be used for working with small products, since heavier angle grinders are very inconvenient for this purpose;
availability of quick-release protective casing, for installation of which no tools are required;
the presence of a power unit that maintains low speeds;
reasonable cost of production;
the presence of a smooth descent;
the presence of a main handle that can be used in three positions;
complete with additional handle.

The combination of power, dimensions, weight and additional functions - positive traits, which distinguishes the Interskol angle grinder UShM-125/1100E. User reviews confirm the well-deserved popularity of the tool both among craftsmen who professionally use this angle grinder in production, and among amateurs who like to tinker at home.

Disadvantages of UShM-125/1100E

According to numerous consumers, weaknesses of this grinder are:

Possibility of breakdown This mainly occurs as a result of voltage surges from 220 to 260 V. In this mode of operation, the regulator quickly breaks down.
High cost of spare parts.
Poor ventilation and lack of armor on the windings. Lack of ventilation, according to user reviews, leads to the fact that the engine located inside the angle grinder burns out after several weeks of operation. This is due, according to the owners of the tool, to the fact that the plastic casing does little to protect the engine from dust.

A long service life of the UShM-125/1100E is possible subject to high-quality lubrication and timely replacement of its carbon brushes and bearings.

Repair

Any power tool breaks down sooner or later. Interskol UShM-125/1100E is no exception. You can repair this device yourself.

All breakdowns of grinders are divided into mechanical and electrical.

To successfully and quickly troubleshoot problems you will need:

instructions, which contain a detailed algorithm for disassembling and assembling the Interskol structure UShM-125/1100E;
product diagram;
open-end wrenches, hammer, vice, press. These tools are used in troubleshooting mechanical problems;
IK-2 tester for detecting short-circuited turns (used for electrical breakdowns of angle grinders);
lubricant, washing liquid, wipes (auxiliary materials).

Before starting work, ensure high-quality lighting of the workplace.

Guided by step by step instructions And visual diagram, you can successfully repair the instrument yourself.

Stator failure. Symptoms of a problem

The most common stator failure is considered to be burning. Mostly it occurs as a result of burning of a power tool. Before proceeding with the repair of the grinder, it is necessary to inspect the structure and determine the nature of the malfunction. When the stator burns out, the rotor of the angle grinder begins to spin uncontrollably.

How to fix it?

To begin with, the angle grinder must be disassembled and the faulty stator removed from the housing. You can also check its functionality without removing it from the case.

But such a procedure is only possible in a specialized workshop. At home, for such a check, you can use a special device for monitoring short-circuited turns IK-2. It is intended to detect breaks or short circuits in the stator windings, which does not have to be removed from the housing for this. A burnt stator needs to be rewinded or replaced.

How to rewind the stator?

If it is not possible to purchase a new stator, then the old one can be repaired by carrying out repair measures, which consist in covering the stator with a new winding.

Sequencing:

from one edge you need to cut the old winding;
count the turns and determine in which direction the winding is made;
measure the diameter of the wire;
calculate the percentage of filling of the core grooves;
after removing the damaged winding, it is necessary to check the insulation and clean the grooves, wind the required number of turns;
put an insulating wire on the ends of the windings;
solder the ends of the windings.

When carrying out the stator winding, it is important to use alternating current, perform impregnation of new windings. After impregnation, traces of impregnation must be cleaned, both inside the stator and outside, on its body. During operation, it is necessary to check from time to time whether the rotor moves freely inside the stator.

Rotor failures

There are several reasons causing malfunctions:

carbon brush wear;
power outages and short circuits;
wear of the armature commutator lamellas;
destruction or jamming of the rotor bearings.

Troubleshooting a rotor malfunction requires experience. Best to buy new tool or have your angle grinder repaired at a specialized service center. If the work is done on your own, then it is very important to have required material and follow the procedure:

unscrew the nut and key securing the rotor drive bevel gear (11);
the gear is removed from the rotor shaft (8);
the rotor is removed from the gearbox housing (19);
Using a special puller or improvised means (a vice, steel strips, a hammer), the bearings (9) are removed from it.

What other breakdowns happen?

Some common electrical breakdowns are:

1. Breakage of carbon brushes. You can also deal with this problem on your own. Procedure:

The design of the angle grinder "Interskol" UShM-125/1100E is designed in such a way that the carbon brushes are located in special brush holders. You can get to them after removing back cover in the stator housing;
Unscrew the screws that secure the brush holder;
Determine the wear level of carbon brushes. This can be done after measuring their remaining length. If the brush is in working condition, its length should be at least 0.5 cm.

2. Damage to the power cable. This malfunction mainly occurs at the points where the wire enters the tool and into the plug. Twists in these cases will not solve the problem. A faulty electrical cable must be replaced.

Final stage

After all necessary repairs have been carried out, the corner Sander it is put back together in the same sequence as it was taken apart. But before assembly itself, it is necessary to lubricate all mechanical components of the angle grinder.

For this purpose, experts recommend domestically produced lubricants. On the shelves of stores selling household electrical appliances you can find lubricants from foreign manufacturers, but they are much more expensive, although their quality is no better than domestic ones. Among the huge selection of lubricants, you should choose those products that have high adhesion rates (they are recommended for gearboxes of all angle grinders). Such lubricants adhere better to the surface.

If you have an old angle grinder in your arsenal, don’t rush to write it off. Using a simple electrical circuit, the device can be easily upgraded by adding the function of changing the speed. Thanks to a simple regulator that you can actually assemble with your own hands in a few hours, the functionality of the device will increase significantly. By reducing the rotation speed, the grinder can be used as a grinding and sharpening machine for various types materials. New opportunities are emerging for the use of additional attachments and accessories.

Why grinder low speed?

The built-in disc speed control function allows you to delicately process materials such as plastic or wood. At low speeds, operating comfort and safety increases. This function is especially useful in electrical and radio installation practice, in car services and restoration workshops.

In addition, among professional users of power tools there is a strong opinion that the simpler the device is, the more reliable it is. And it is better to move the additional service stuffing outside the power unit. In this situation, equipment repair is greatly simplified. Therefore, some companies specially produce remote, separate electronic regulators that connect to the machine’s power cord.

Speed controller and soft start - what are they for?

Modern grinders use two important functions that increase the reliability and safety of the tool:

speed controller - a device designed to change the number of engine revolutions in various operating modes;
soft start - a circuit that ensures a slow increase in engine speed from zero to maximum when the device is turned on.

Used in electromechanical instruments, in the design of which a commutator motor is used. Helps reduce wear on the mechanical part of the unit during switching on. Reduces the load on electrical elements mechanism, putting them into operation gradually.

As studies of the properties of materials have shown, the most intense production of friction units occurs during a sharp transition from a state of rest to a mode of rapid movement. For example, one start of an internal combustion engine in a car is equivalent to 700 km of mileage in terms of wear on the piston group.

When the power is turned on, an abrupt transition occurs from a state of rest to rotation of the disk at a speed of 2.5–10 thousand revolutions per minute. Those who have worked with an angle grinder are well aware of the feeling that the machine simply “rips out of your hands.” It is at this moment that the overwhelming number of breakdowns associated with the mechanical part of the unit occur.

The stator and rotor windings experience no less load. Brushed motor starts in short circuit mode, the electromotive force is already pushing the shaft forward, but the inertia does not yet allow it to rotate. A jump in starting current occurs in the coils of the electric motor. And although they are structurally designed for such work, sooner or later a moment comes (for example, during a power surge in the network) when the winding insulation cannot withstand and an interturn short circuit occurs.

When soft start circuits and changes in engine speed are included in the electrical circuit of the tool, all of the above problems automatically disappear. Among other things, the problem of the “failure” of voltage in the general network at the time of launch is solved. hand tools. This means that the refrigerator, TV or computer will not be at risk of “burning out”. And the safety circuit breakers on the meter will not operate and cut off the current in the house or apartment.

The soft start circuit is used in angle grinders of medium and high price categories, the speed control unit is used mainly in professional models of angle grinders.

Adjustable speed allows you to process with an angle grinder soft materials, perform fine grinding and polishing - at high speed, wood or paint will simply burn out.

Additional electrical circuits increase the cost of the tool, but increase the service life and level of safety during operation.

How to assemble a regulator circuit with your own hands

The simplest power regulator, suitable for an angle grinder, soldering iron or light bulb, is easy to assemble with your own hands.

Electrical circuit diagram

In order to assemble a simple speed controller for an angle grinder, you need to purchase the parts shown in this diagram.

Schematic diagram speed controller

R1 - resistor, resistance 4.7 kOhm;
VR1 - trimming resistor, 500 kOhm;
C1 - capacitor 0.1 µF x 400 V;
DIAC - triac (symmetrical thyristor) DB3;
TRIAC - triac BT-136/138.

Circuit operation

Trimmer resistor VR1 changes the charging time of capacitor C1. When voltage is applied to the circuit, at the first moment of time (the first half-cycle of the input sinusoid), triacs DB3 and TRIAC are closed. The output voltage is zero. Capacitor C1 charges and the voltage across it increases. At a certain point in time, specified by the R1-VR1 chain, the voltage on the capacitor exceeds the opening threshold of the triac DB3, the triac opens. The voltage from the capacitor is transmitted to the control electrode of the TRIAC triac, which also opens. Current begins to flow through the open triac. At the beginning of the second half-cycle of the sinusoid, the triacs are closed until capacitor C1 is recharged in the opposite direction. Thus, the output produces a pulse signal of complex shape, the amplitude of which depends on the operating time of the C1-VR1-R1 circuit.

Assembly order

Assembling this circuit will not be difficult even for a novice radio amateur. Spare parts are available and can be purchased at any store. Including desoldering from old boards. The procedure for assembling the regulator using thyristors is as follows:

How to connect the device to an angle grinder, options

The connection of the regulator depends on what type of device is selected. If used simple circuit, just install it into the power supply channel of the power tool.

Installing a homemade board

There are no ready-made installation recipes. Anyone who decides to equip an angle grinder with a regulator places it in accordance with their goals and model of the tool. Some people insert the device into the handle of the holder, others into a special additional box on the body.

In different models, the space inside the angle grinder body may be different. Some have enough free space to install a control unit. In others, you have to take it to the surface and attach it in a different way. But the trick is that, as a rule, there is always a certain cavity in the back of the instrument. It is designed for air circulation and cooling.

Cavity at the back of the device

This is usually where the factory speed controller is located. A self-made diagram can be placed in this space. So that the regulator does not burn out, thyristors should be installed on a radiator.

Video: soft start plus and engine speed control

Features of mounting the finished block

When purchasing and installing a factory regulator inside an angle grinder, most often you have to modify the body - cut a hole in it to allow the adjustment wheel to come out. But this may adversely affect the rigidity of the casing. Therefore, it is preferable to install the device outside.

The adjustment wheel changes the speed

The numbers on the adjustment wheel indicate the number of spindle revolutions. This value is not absolute, but conditional. “1” - minimum speed, “9” - maximum. The remaining numbers serve as a guide for regulation. The location of the wheel on the body varies. For example, on the Bosch PWS 1300–125 CE, Wortex AG 1213–1 E or Watt WWS-900 angle grinders, it is located at the base of the handle. On other models, such as the Makita 9565 CVL, the adjustment wheel is located at the end of the housing.

The connection diagram of the regulator to the angle grinder is not complicated, but sometimes it is not so easy to stretch the cables to the button, which is located at the other end of the device body. The problem can be solved by selecting the optimal wire cross-section or by placing it on the surface of the casing.

The regulator is connected according to the diagram

A good option is to install the regulator on the surface of the device or attach it to a network cable. Not everything always works out on the first try; sometimes the device has to be tested and then some adjustments made. And this is easier to do when access to its elements is open.

Important! If you have no experience working with electrical circuits, it is more advisable to purchase a ready-made factory regulator or angle grinder equipped with this function.

Attaching to the power cord

Device Instruction Manual

The basic rule when operating an angle grinder with a homemade speed controller is to adhere to the work and rest schedule. The fact is that an engine operating at a “regulated” voltage gets especially hot. When grinding at low speeds, it is important to take frequent breaks so that the commutator windings do not burn out.

It is also highly recommended not to turn on the tool if the speed regulator is set to minimum - the reduced voltage will not be enough to rotate the rotor, the collector lamellas will remain in short circuit mode, and the windings will begin to overheat. Unscrew the variable resistor to the maximum, then, turning on the angle grinder, reduce the speed to the desired value.

Following the correct order of activation and adjustment will allow you to operate the angle grinder for an unlimited period of time.

In addition, it should be understood that the adjustment of the speed of rotation on an angle grinder occurs according to the principle water tap. The device does not increase the number of revolutions, it can only decrease them. It follows from this that if the maximum nameplate speed is 3000 rpm, then when a speed controller is connected, the angle grinder will operate in a range lower than the maximum speed.

Attention! If the angle grinder already contains electronic circuits, for example, it is already equipped with a speed controller, then the thyristor controller will not work. The internal circuits of the device simply will not turn on.

Video: homemade angle grinder speed controller

Equipping the angle grinder with a circuit for adjusting engine speed will increase the efficiency of using the device. and expand its functional range. This will also save the technological resource of the grinding machine and increase its service life.