The speed controller does not work on the angle grinder

How to reduce the speed on the angle grinder with their own hands?

Collector motors with series excitation are used in lathes with speed regulator. They can be operated by DC or AC current. This type of motor is easily controlled by changing the current in the circuit.

Thanks to the fact that modern regulators use key pulse control, they cool down very little and can be built into even small tools. Control is achieved by means of a potentiometer whose knob is located on the handle of the machine.

Why control the speed of the disc?

Different cutting or grinding speeds are required by the physical properties of the materials being worked with. High speed with low pressure is required when cutting hard materials that can otherwise crumble or split. Soft materials that are not resistant to heat (thermoplastics, wood), on the contrary, require low speed:

• ceramics: 10000 rpm;
• metal: 8000 rpm;
• hard plastics: 5000. 8000 rpm;
• wood: 3000. 5000 rpm;
• soft plastics: less than 2000 rpm.

All professional tools are equipped with a stabilized speed regulator, but inexpensive household angle grinder, power less than 1200 watts, not always complemented by it. In this article we will talk about how to make such a regulator yourself to reduce RPM.

Speed controller for angle grinder with my own hands

Although creating a RPM regulator for the angle grinder is little, who needs it, there are still models that have made manual adjustment of disk speed. The regulation of the angle grinder is much different from an electric electric screwdriver or drill, because:

• Absolutely different grip is used during work.
• It is forbidden to make adjustments during work. Adjustment should only be carried out when the machine is switched off.

The need to adjust the speed of the disc

• When you cut metal (no matter how thick the material is), the result of the work you do depends on the rotational speed of the blade. If you are cutting thicker material you should use the maximum RPM. If you are cutting thin material you should slow down if you have to cut at high speed because the blurring of the blade surface is too fast.
• If a tile is cut at high speed, there is a certain amount of danger. Also, the disk, spinning at great speed, begins to beat off small pieces of material, thereby making its surface brittle. Since the stone has a variety of types, a specific speed is used for each type. High speeds are used for many minerals.
• If sanding or polishing is carried out, then the adjustment of the speed of the angle grinder is simply necessary. If the speeds are set incorrectly, the surface of the material will be ruined. For example, the material may be damaged if it has a paint coating.
• If you constantly use discs that have different diameters, then the speed controller for the angle grinder must be available. If you change the angle grinder disc for another one that has a larger diameter, the RPM speed must be reduced. You can not hold a grinder in your hands, which has a disc with a huge diameter.
• The speed of rotation when polishing concrete material depends on the use of the specific drill bit type. The torque must not be reduced by reducing the RPM.
• If you are using a diamond disc, the speed must be reduced, otherwise the surface will be damaged by overheating. Of course, if you use an angle grinder to cut pipes, angles or profiles, then the presence of a regulator is not necessary. But if the angle grinder is used for a variety of purposes, then the speed controller for the angle grinder is just necessary. All these reasons show that the presence of an angle grinder regulator is a must.

Angle grinder regulator description

The angle grinder regulator is a rheostat (variable resistor) that reduces the voltage (all done by the regulator). You need to control the amperage, because if you reduce the number of revolutions, there will be a decrease in the power of the construction machine. Consequently, the torque will be reduced. As a result, it will become a small value of voltage, and at a certain resistance the electric motor will not be able to turn the shaft. Therefore, it is necessary to follow a certain scheme: The scheme of the angle grinder is made up of a soft starter module and directly the speed regulator.

Modern advanced models have a distinctive electronic system, and not everyone can afford to buy it.

Making a regulator by yourself

How to make a regulator by yourself? The desire to build an ordinary electronic device designed to change the electric power (dimmer) ends up with nothing. First of all, the dimmer for angle grinder is designed for a different load. Also, the dimmer has no overlap with the control of the winding of the electric motor. Therefore, you need to install a separate circuit. You also need to think about where it will be located inside the body of the angle grinder.

An important point: if you do not have any experience with electrical circuits, it is best to buy a ready-made regulator for angle grinder or angle grinder with the presence of this function.

A simple semiconductor device (thyristor regulator) can be built with your own hands. For this procedure will need 5 radio elements. Radio elements can be purchased at a radio market. Due to the compactness, you can safely conduct the prepared scheme in the angle grinder, without damaging the ergonomics and reliability. However, there is no torque retention when the RPMs are reduced on the angle grinder. This option is best suited for machining soft metals as well as tinplate, which has a small thickness.

If you are processing stone, then you need to install a disk that has the size of 180 millimeters. Next, you need to create a more complex circuit of the regulator. In this scheme, the control module will be the chip KR1182PM1. This circuit has control over the amperage at different RPMs, and also makes the loss of torque minimal when RPMs are reduced. Using such a scheme increases the operation of the motor.

If the angle grinder is used as a circular grinder, it is necessary to equip the angle grinder with a connection point. Thanks to such a point, the connection is made, and the speed can be adjusted remotely. You get a great homemade speed controller.

It does not depend on how you made the regulator, it is a mandatory component of the angle grinder, which makes the possibilities of work wider and allows the comfortable use of this construction tool. Also, after installing the regulator, it is necessary to conduct a test run of the angle grinder to check: whether the construction tool does not tear out of his hands. External speed controller for angle grinder with your own hands you can make.

How to make adjustment for angle grinder at home, homemade options

A relatively simple scheme of regulation on semiconductor devices, some users with a skill in working with electrical technology, can make their own. However, it will not be able to effectively adjust the amperage at lower speeds, and the value of torque on the work shaft may be insufficient. This will not be a big obstacle when working on polishing, cutting thin sheet metal or processing soft materials (plastic and similar).

If making a circuit by your own hands causes difficulties or the nature of work with the angle grinder, for example, a stone or ceramic, requires a more complex system with a chip, you can buy a ready-made unit and install it on the angle grinder.

Standard dimmer to change the brightness of the light found in the operation of the angle grinder in the following video.

Important: The power of the dimmer must be at least as powerful as an angle grinder. The quality of polishing work and less dust emitted during polishing determine the advisability of finalizing the electrical part of the angle grinder with a standard dimmer. This design requires a reasonable hand-load dosage when working, since overheating of the motor cannot be ruled out and there is a risk of failure.

Readymade solid-state power controllers are available from online stores. The author of the following video bought in Aliexpress Chinese sample, and it is enough powerful. 4 kW. This value increases the versatility of its application. Many household appliances (angle grinder, drill, heating elements in the form of heating elements) are operated in power ranges, where such a regulator can work quite effectively. The main disadvantage of such regulators is the inability to maintain the load for a long time (the power tool quickly overheats and requires stopping to cool it).

You can control the rotational speed of some power tools not only manually with a thumb wheel. Some devices are more convenient to control by means of pedals. In the following video the author demonstrates this method of control. Here is taken the speed controller made in the form of a pedal from a sewing machine and adapted to control an electric jigsaw. Nothing prevents you from making such a variant of control of the angle grinder, but the need for this should be justified by the nature of the work performed.

No loss of power

It is almost impossible to make a regulator that changes the speed without losing power on your own. Such devices with feedback on rotational speed monitoring and adjustment of current on its basis are produced only by manufacturers of lathes. Only regulators on semiconductor circuits, which do not guarantee 100% power retention when you change the spindle speed of the angle grinder, can be made or installed independently.

How to reduce/increase the speed of the disk

Readily available inexpensive Chinese-made circuit board can be mounted, as the author of the following video, in a separate plastic case, connected to a cable with a plug and a socket mounted on it. By connecting the plug to the power grid, and the angle grinder to it through the socket, you can change the amount of variable resistance by adjusting the wheel, to set the angle grinder to the desired speed. This tool will polish surfaces much better quality.

How to install, connect

Grinder users have come up with many different ways to arrange the speed controller and the angle grinder, for which it is designed. It can be located as a standalone element outside the body of the angle grinder, or it can be built inside. Below are some videos with these options.

In the following video, the author uses an external control device with an on/off button. Just in place of this very button is inserted ready-made Chinese board on semiconductors. The technology of wiring work is made at a good technical level. Such a carrier will be convenient to use during the execution of angular grinder works, requiring the use of low revolutions.

To place additional devices inside the body of the angle grinder can be quite a challenge. Often you have to make non-trivial decisions, like in the following video. Here, in order to put a board with speed control and soft start, it was necessary to change the buttons involved in the on/off lever operation. In the freed space was able to place a triac with a radiator and a board with a cooler of rpm controller soft start chip of angle grinder.

How to remove the voltage sensor

In the following video the author had a broken speed regulator on one of his angle grinder models. Attempts to repair it failed. The author describes how to remove the broken regulator and build an electrical circuit without it (just connect the stator windings directly through the switch). The angle grinder will function only at maximum rpm.

The simplest regulator circuit

Electrical diagram of the speed regulator for angle grinder is assembled on the circuit board or in hinged mounting. And the printed-circuit board, too, can be made by yourself, using textolite and bleach for etching. Instead of iron, you can use a mixture of hydrogen peroxide, salt and citric acid.

Diagram of motor speed regulator for angle grinder

Circuit configuration

• resistor R1 (4,7 kOhm);
• DIAC symmetrical thyristor (DB3);
• symmetrical thyristor TRIAC (VT-136/138);
• the trimmer resistor VR1 (500kOhm);
• Capacitor C1 (0.1 uF400V).

Working principle

The circuit working principle is as follows. VR1 is responsible for the charging time of C1. Thyristors are closed when voltage is applied to the circuit, the output is 0. As the capacitor is charged the voltage in the capacitor increases and opens the DIAC which gives the voltage to the TRIAC. It also opens and allows current to flow. Then both thyristors close and stay in this position until C1 is fully recharged. As a result, a complex waveform with an amplitude directly related to the operating time of the C1-VR1-R1 circuit is generated at the output.

Connection diagram of the speed regulator

Final assembly and testing of the regulator

Circuit is assembled on the printed circuit board or on the copper (aluminum) radiator. When hinged assembly is especially important place of thyristors installation (strictly on the radiator, it plays the role of heat sink). Then there is a mandatory check of the circuit operability with an ordinary light bulb. Smoothness of filament change will be the same as in the ready made speed regulator for angle grinder after final assembly.

The factory models provide a plastic regulating wheel, if you want it can also be bought separately and included in the set of self-made regulator. If testing is successful, the regulator is attached to the angle grinder and plugged into the power circuit of the tool.

Winding data for Bosch stators and armatures and other brands of angle grinder

Stator for Bosch GWS6-100/GWS6-115 HAMMER with green winding. 220Volt photo

Repairing the stator with your own hands makes it much easier to have documentation with winding data. This information can usually be obtained from the data sheets for a particular model of angle grinder. You will not need to spend a lot of time using labor-intensive ways to determine the number of winding turns of the coils and the diameter of the wire used. The datasheets contain the following basic information, including the winding data of the stators:

• operating parameters of the angle grinder (power, speed, operating voltage and other characteristics);
• the number of slots in the stator core for laying the windings;
• the diameter of the winding wire without insulation;
• number of wires in one groove;
• Depending on the winding scheme, it can be done with a certain pitch, which is specified in the passport;
• dimensions of the stator’s inner and outer diameter and other technical information.

It is possible, with the winding data, to rewind most of the stators of angle grinders by yourself. However, many other electric motor stators, because of the complex winding scheme, it is not possible to do without special devices.

The main malfunctions of angle grinders and their causes

According to statistics, most cases of failure of the angle grinder are related to the electrical part of the machine. Some failures may be minor, which allows you to repair the angle grinder with your own hands. But, for example, when the motor windings burnout repair angle grinder can only produce a specialist.

the angle grinder does not turn on

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

• the electrical plug is defective;
• A faulty electrical cable;
• the start button is broken;
• contact between the power cable and the button is broken;
• breakage of the contact wire of the electric brush;
• Severe wear of the electric brushes;
• Rotor or stator windings have failed.

angle grinder doesn’t rotate

There are various possible causes of the angle grinder not picking up speed.

• Breakage of the RPM control unit. To check this version, connect the motor of the machine directly, bypassing the regulator, and check the operation of the device.
• Faulty electric cable due to constant kinking or mechanical damage. Because of this, the damaged wire begins to warm up under load, and the engine speed drops.
• Dust on the collector. You need to remove the dirt with alcohol.
• Problems with the brushes. They may be worn out or have a short contact wire as shown in the following photo.

Brush half worn out, but still serviceable. In this case, a short contact wire does not allow the spring to press the electrode to the collector. This situation can also be the reason why the angle grinder stopped working normally.

Electric motor heats up

The angle grinder can be hot.

• Improper operation of the machine. As a result of overloading, the electric motor can become very hot, which often causes the windings to burn out.
• Destruction of the bearings on the armature. As a result, the rotor clings to the stator, the motor cannot be operated properly and the windings overheat. The problem can be solved by replacing the bearings.
• The ventilation ducts through which air flows to cool the motor are blocked. The ventilation openings must be cleaned of dust.
• Breakage of the impeller, which serves for cooling the motor. It is installed on the rotor, on the opposite side with respect to the collector. If the impeller is broken, it must be replaced with a new one.

The angle grinder sparks

If you notice a strong sparking when you turn on the angle grinder in the place where the collector is, then the causes of this trouble can be.

• Damage to the armature winding: breakage of one or more winding sections, inter-turn short circuit. Such defects are characterized by excessive noise, low engine speed and burning brushes.
• The contact between the collector plates and the winding may be faulty.
• Weak pressure of brushes. When the angle grinder is operated for long periods, the springs overheat and may “anneal” and lose their tension.
• Rotor imbalance.
• Cylindrical surface distortion of the collector. This sometimes occurs after rewinding if the armature is not turned on the lathe but mounted directly on the machine. Brushes may also show excessive arcing.
• Insulation between the collector lamellae is broken. There could also be graphite clogging of the track grooves or a breakdown between the lamellae.
• Worn bearings that cause the rotor to run out also make the brushes spark strongly.
• Breach of armature shaft geometry. This usually happens when the electric motor is carelessly disassembled, when the shaft is bent.
• Wrong brand of graphite brushes installed. The brushes are matched to the expected speed and voltage.
• Raising one or more lamellae causes the brushes to burn out quickly. This happens due to overheating of the motor in continuous operation. As a result, the glass mass that serves as the base of the collector softens and the lamellas start to rise. Because the blades are lifted, the brushes wear out very quickly.

Electronic unit in an angle grinder

The electronic unit enables the speed controller and the soft start to be combined into one unit. The electronic circuit is implemented on the principle of pulse-phase control with a gradually increasing phase of the triac’s opening. Angle grinders of various capacities and price categories can be equipped with such a unit.

Variety of electronic unit: see table for examples

Name	Power, W	Maximum speed of the disk, rpm	Weight, kg	Price,
Felisatti AG125/1000S	1000	11000	2,5	2649
Bosch GWS 850 CE	850	11000	1,9	5190
Makita SA5040C	1400	7800	2,4	9229
Makita PC5001C	1400	10000	5,1	43560
Flex LST 803 VR	1800	2400	6,5	91058

Angle grinders with electronic unit: popular in the photo

Felisatti AG125/1000S

Bosch GWS 850 CE

Makita SA5040C

Makita PC5001C

Flex LST 803 VR

Replacement of graphite brushes

Practice shows that it is graphite brushes are most often the cause of grinder failure. Their service life is limited to 1.5-2 years. Replacing old brushes with new ones shouldn’t be too difficult. To check the brushes, the housing must be open. They are easy to get to. First of all (with the power cord unplugged) use a straight screwdriver to gently pry up and move aside the brush holders mounted on the collector. Screwdriver can also be used to remove the brushes. If you have a brand-name tool, then it is likely that the brush is held in place by a spring, and to remove it, it is enough to press down on this spring with a screwdriver. If the tool is Chinese, then there are plugs, which will have to be removed with a screwdriver, only after that you can remove the brush.

The brushes should be replaced only with new ones, bought at a specialized store. Buying them, be sure to take the removed brush and measure your purchase to fit the size. Slide the new brush into the brush holder, making sure it moves smoothly.

If it does not cling to anything, you can fix the brush in the brush holder. Then push it in and you can reinsert the brush holder in the socket. Replace the second brush in the same way. Finally, check how neatly and properly you have laid the wires, whether they will not be squeezed anywhere. After that you can close the housing and try to turn on the machine.

Brush replacement. this is the maximum that common sense allows you to fix yourself in the angle grinder, without the risk due to inexperience or inability to spoil the tool.

complex repairs, such as cleaning the manifold, replacement of the gearbox or armature, without the necessary experience, it is better not to do yourself. If there is such a need. invite a friend, who has more than once performed a similar repair. The repairs themselves can do with their own hands, but only under his supervision and on the tips.

Better yet, take your tool to a repair shop. Still, the angle grinder, even fully serviceable, is source of increased danger. It is better to pay professionals for repair than pay doctors for their treatment.

If the angle grinder is not equipped with a speed regulator, can you install it yourself? Most angle grinders (angle grinder), in common parlance grinders, have a speed regulator.

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

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

The simplest representation of a grinding machine circuit diagram

advanced models automatically maintain the speed of rotation regardless of the load, but more common are tools with manual adjustment of disc speed. If on a drill or an electric screwdriver the trigger-type regulator is used, then on an angle grinder such a principle of regulation is impossible. First. the particularities of the tool imply a different grip when working. Second. adjustment during work is inadmissible, so RPM value is set when the motor is off.

Circuit operation

The VR1 trimmer resistor changes the charging time of the capacitor C1. When voltage is applied to the circuit, at the 1st instant of time (1st half period of the input sine wave) the triacs DB3 and TRIAC are closed. The output voltage is zero. Capacitor C1 is charged, the voltage here increases. At a certain point in time, defined by the R1-VR1 circuit, the voltage on the capacitor exceeds the DB3 opening threshold, the triac opens. The voltage from the capacitor is transferred to the control electrode of the TRIAC triac, which also opens. A current starts to flow through the open triac. At the beginning of the second half cycle of the sine wave the triac is locked until the capacitor C1 is recharged in reverse. Thus, a pulse signal of a complex shape is output, the amplitude of which depends on the running time of the circuit C1-VR1-R1.

What is a soft start

A smooth start of the angle grinder is a voltage build-up, which accelerates the motor without inrush current and with a gradual increase in torque. It protects the power supply line from overvoltage and prevents it from “sagging. This is especially relevant when powering the angle grinder from autonomous voltage sources. In addition, it protects the motor windings from excessive currents, which can lead to their breakdown. During the soft start, the gearbox of the angle grinder is not subject to shock loads, which protects it from premature wear.

The electronic circuitry ensuring the angle grinder’s smooth start is based on the same principle as the speed regulator. It also uses a triac, which limits the power supply to the motor. But unlike the speed regulator, the control pulses to the triac are formed not by manual setting of resistance in the RC-chain, but by the electronic circuit, which forms the pulse sequence with decreasing delay time. The diagram below shows how the pulse shift time is reduced and the power supplied to the angle grinder motor is increased.

Since the soft starter and the speed regulator work on the same circuitry, electronic units are available which combine the functions of both devices.

Minor malfunctions and troubleshooting

In cases where the angle grinder refuses to turn on when the start button is pressed, the cause may not be significant and most likely the repair can be made by yourself without the help of a specialist. You need to follow the main rule. start with the simplest units and move to more complex ones. The cause of the breakdown of the angle grinder in this case can be a breakage in the wiring section of the power wire and brushes.

First of all, you need to unplug the angle grinder from the mains, then inspect the cable for damage. After that you need to disassemble the housing and check the connection of the power button and brushes. If the wire is damaged, it can be replaced with a new one, and the broken electrical circuit can be restored. If after checking the cable and electrical circuit, there is power to the machine but no start, the problem may be in the starter button itself.

Check the pushbutton and if any malfunction is found, repair or replace it. The button should be carefully disassembled and the terminals and wires should be labeled. When reconnecting it is important to connect the contacts correctly, since improper installation can cause burnout of the winding and jamming the armature.

After checking the functionality of the power cord and button you need to check the speed controller, which is available in some models of angle grinder. If no faults are detected, you need to pay attention to the brushes and replace them if necessary, as well as clean all contacts.

Carbon brushes defective

The main cause of failure may be the brushes. Depending on the load and duration of operation of the angle grinder, the brushes can last six months, a year or two, then wear out, and the tool can stop working. Replace old parts with new ones with the cable disconnected and the housing disassembled. Unscrew the brush holders with a screwdriver and remove the old brushes. They can also be sealed in the housing with plugs, so that the housing need not be disassembled.

Brushes should be replaced only with a similar size and material of manufacture, and after replacement brushes are lapped. angle grinder works for a while at idle speed. With a faulty start button, you must not work with the angle grinder, as this can lead to jamming of the cutting disc, its destruction and unpredictable consequences. Speed regulator is a soft starter of angle grinder, and after a malfunction in its operation, it requires replacement, as repairs will be difficult and almost impossible.

The main faults, their causes and repair methods

To simplify the problem, troubleshooting and repair should be carried out systematically. Do not rush to disassemble the tool. First determine the type of fault. The most important trouble. the angle grinder does not turn on. What needs to be checked:

Anchor of the electric motor

If these elements are serviceable, then 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 make contact or is broken off, the electric current will not flow to the winding and the angle grinder does not want to work.

In order to inspect the condition of the brushes it is necessary to:

Brushes are spring loaded, so take care not to lose the springs. Removed brushes should be of equal size. There will be some wear on them, but there should be no chips or cross cracks that could break the contact.

If the brushes are in good condition, then the motor armature will need to be inspected. This assembly is only called an armature, but in fact, it has absolutely nothing to do with an armature. It is the center shaft of the motor that houses the winding and the collector ring. Sometimes there is a strong spark between the brushes and the collector contacts because of the heavy loads. The result is that the copper contacts become covered in a layer of oxide and no current flows to the winding.

What you need to do to get the armature in good order? It is necessary to take an ordinary white rubber band used by the draughtsmen and lovers of drawing. It is necessary to rub the contacts with a corner of a rubber band. The oxide film should be cleaned and have a shiny copper sheen.

If this operation has no results, it is necessary to open the body of angle grinder and examine the condition of internal wires, phase shifting capacitor and winding. The winding should have an even color of varnish, which coats the winding wire. Darkening or blackening of the wire or its sections indicates a short circuit of the winding. This malfunction with their own hands is difficult to eliminate, will need to replace the armature.

Gearbox Repair

The purpose of the gearbox is to transmit rotation of the motor shaft to the angle grinder’s disc. over, since we have an angle grinder, then we have an angle reducer. To inspect it is necessary:

After that, the reducer should come out of the case. There are few faults here:

Defective gearbox elements must be replaced. Replacing the gear is not difficult. Then the gearbox is lubricated with a good coat of thick grease and reinstalled.

Repairing the stator of an angle grinder

The stator is the part of the electric motor which is fixed in the housing. It is designed to create an electromagnetic field in which the armature rotates.

The main fault in the stator is a winding breakage or excessive overheating. The dangers of overheating? If the winding wires overheat, the protective insulation varnish that covers them also overheats. A fault in the lacquer coating causes the winding to short-circuit.

Even a single winding fault shorts the angle grinder completely. The winding immediately begins to overheat and smoke. The shaft rotates slowly or stops rotating altogether.

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

Main malfunctions, their causes and repair methods

To simplify the problem, troubleshooting and repair should be performed systematically. There is no need to rush to disassemble the tool. First let’s define the type of fault. The most important problem. the angle grinder does not turn on. What you need to check:

Motor anchor

If it is OK, then you need to check the brushes. The brushes are used to transfer the supply voltage to the motor’s collector pins. The armature windings are soldered to these contacts. If one of the brushes does not contact or breaks off at all, the electric current will not flow to the winding and the angle grinder will not want to work.

In order to inspect the condition of the brushes is necessary:

Brushes are spring loaded, so you have to try not to lose the springs. Removed brushes must be of equal size. There should be some wear, but no cracks or cross cracks which could interfere with the contact.

If the brushes are in good condition, the motor armature will have to be inspected. This assembly is only called an armature, but in reality has absolutely nothing to do with an armature. This is the center shaft of the motor that houses the winding and the collector ring. Sometimes there is a strong spark between the brushes and the collector contacts due to heavy loads. As a result, the copper contacts are covered with a layer of oxide and the current does not flow to the winding.

What you need to do to fix the armature? It is necessary to take an ordinary white rubber band, which is used by draughtsmen and drawing lovers. Rub the contacts with the corner of the rubber band. The oxide film should peel off and have a copper sheen.

If this operation is also unsuccessful, you need to open the angle grinder body and examine the condition of the internal wires, the phase shifting capacitor and the winding. The winding must have an even color of varnish, which coats the winding wire. Darkening or blackening of the wire or sections thereof indicates a shorted winding. This malfunction with their own hands to fix it is difficult, you need to replace the armature.

Gearbox repair

The task of the reducer. to transmit the rotation of the motor shaft to the wheel of the angle grinder. And, since we have an angle grinder, we have an angle gearbox. To inspect it you need to:

After that, the reducer should come out of the housing. Faults here are few:

Failed gearbox elements must be replaced. Replacing the gear is not difficult. Then the gearbox is lubricated with a good layer of thick grease and reinstalled.

Angle grinder stator repair

The stator is a part of the electric motor, which is fixed in the housing. It is designed to create an electromagnetic field in which the armature rotates.

The main failure of the stator is a breakage of the winding or its strong overheating. The dangers of overheating? When the winding wires overheat, the protective insulating varnish that covers them also overheats. A fault in the lacquer insulation causes the winding to short circuit.

Even a single winding fault strikes the angle grinder completely. The winding immediately begins to overheat and smoke. Shaft rotates slowly or stops rotating at all.

To repair the stator, the windings will have to be replaced with new ones or rewound. But rewinding the stator is not a procedure for beginners.

Angle grinder stator repair

The cause of a defective grinder stator can be determined. You need to pay attention to any irregularities in the winding. The rotor can develop speeds in excess of the allowable speeds, which would indicate an interwinding short circuit in the winding. Many breakdowns can only be repaired in service centers, but for trouble-free operation, timely cleaning, lubrication, replacement of brushes and bearings can be performed.

Failure of the stator of a Makita angle grinder is rare, and permanent overheating of the angle grinder can be the cause. In this case, the housing gets very hot, and in the ventilation ducts there is a smell of burning. In the winding of the stator can be a short circuit or breakage, so without special tools to determine the fault and repair the unit is difficult. To repair the angle grinder with your own hands or to replace the stator, it is necessary to carry out these actions:

• Dismantling the gearbox of the angle grinder;
• Disassembling the rotor after removing the mounting bar;
• Removal of stator guard;
• Unscrewing the screws securing the stator in the housing;
• Removing the handle cover and disconnecting the power wires;
• Removing the stator.

The stator is tightly seated in the housing, so the removal process can be accompanied by light blows on the housing with a mallet. Most often the stator must be replaced, but sometimes amateurs can do the rewinding themselves.

Making an external regulator with your own hands without losing power

Users of lathes, which are not equipped with a speed controller, are faced with jobs, the quality of which can be improved by machining at lower speeds than specified in the technical data. Expand the functionality of the angle grinder you can install this option yourself, with your own hands.

Depending on the nature of the work performed, you can install a simpler power regulator or a complex electronic device with feedback, which will provide support for the selected value of revolutions without loss of power. Information on how to install can be found in the article “angle grinder RPM controller with your own hands“. In the case of malfunctions in the mechanism, you should read the information presented in the article “Repair of rotational speeds of bolsters with your own hands”.

On triac BTA-16-200 and thyristor

The main elements of power regulators are semiconductors. triacs and thyristors. You can buy them easily in specialized stores, as well as other elements included in the circuit. resistors and capacitors. A user who has skills in making electronic circuit boards can make the regulator with his own hands. The option of buying a ready-made regulator is also popular among those who want to install it on the angle grinder.

Diagram of the regulator on the U2010B chip. Photo source here

Some microcircuits, acting as a basic component of the electronic speed control unit, working in conjunction with a sensor that reads the speed, provide the necessary speed without loss of power. Such a scheme to perform with their own hands without knowledge of electronics is difficult enough. However, there are microcircuits, such as U2010B, which do not require a tachodometer for operation. Such a device can be purchased in a store and inserted into the electrical circuit of an angle grinder is not very difficult.

A typical speed regulator diagram

This is what the speed regulator board looks like assembled

A motor speed regulator is not just a variable resistor that lowers the voltage. Electronic control of the current value is necessary, otherwise with a decrease in RPM will proportionally reduce the power, and thus the torque. In the end, there will come a critically low voltage, when at the slightest resistance of the disk, the motor simply can not turn the shaft. Therefore, even the simplest regulator must be calculated and made in the form of an elaborate circuit.

And more advanced (and therefore expensive) models are equipped with regulators based on integrated circuits.

Integral speed regulator circuit. (most advanced variant)

If we consider the electric circuit of angle grinder in principle, it consists of speed controller and soft starter module. Power tools equipped with advanced electronic systems are significantly more expensive than their simple counterparts. That is why not every home handyman is able to buy such a model. And without these electronic units will remain only the winding of the electric motor and the trigger.

The reliability of modern electronic components of the angle grinder exceeds the life of the motor windings, so you should not fear the purchase of power tools, equipped with such devices. Only the price of the product can be a limiting factor. Not only that, users of inexpensive models without a regulator sooner or later come to install it themselves. The unit can be purchased in ready-made form or make it yourself.