Why the angle grinder does not pick up speed

Why the angle grinder does not work (angle grinder): it gets hot, sparks, vibrates, makes noise and does not pick up speed

Problems with the brushes of angle grinder they spark, there and the drop in speed and power it does not develop, the brushes can be replaced, sometimes you can do without replacement, it is enough to clean the brush assembly of the angle grinder (angle grinder) from dust and dirt.

Or you may have to replace the brush holder springs.

There are more “trivial” reasons, I have an angle grinder lost speed due to the fact that the wire angle grinder has been damaged or from the constant kinks, or where someone hit it with a cutting wheel.

The contact was bad, it got hot under load, the speed dropped.

Disconnect the angle grinder, “feel” the wire with your hands, find the problem area.

angle, grinder, does, pick

Then we cut the wire, strip the ends, twist and insulate with tape.

But in any case, before you start searching for problems and methods of their elimination, you must remember what caused the problem and what led to it.

the angle grinder, being the most popular tool in the house, is exposed to considerable loads and intensive use. Because of this, after some time it happens that when you start the engine there is a jerk, the smell of burning and other malfunctions, suggesting that the angle grinder (angle grinder) is broken. But you should not immediately carry the device to repair or buy a new one. Most malfunctions of this device can be eliminated independently.

Why are the motor brushes sparking?

Appliances with a collector motor can produce sparks during operation. Intensive sparking often indicates an imminent damage to the tool. The causes for the increased sparking must be discovered and eliminated in good time. The article discusses the most likely causes of this negative phenomenon.

The brush-collector module is the heart of AC electric motor devices and provides the electrical contact between the rotor and the static part of the electrical appliance. This unit consists of two parts: the collector located on the rotor and the brushes. sliding contacts located outside the rotor part and pressed against the collector. Sparking on a collector motor occurs as a result of mechanical interaction between the moving and stationary parts. The contact between the collector and the brushes is periodically interrupted, causing a transient in the electrical circuit, which induces arcing. Brushes of the electric motor collector are the most nondurable part of the construction. Therefore, over time, various problems related to their operation may be observed.

Even a functioning motor usually shows slight arcing of the brushes. If the appliance switches on normally, develops full power and the spark formation is imperceptible, then there is no reason for concern.

Causes of brush arcing

Let’s analyze the most frequently occurring problems of brush-collector assembly.

Dewalt Angle grinder electrical fault finding

1) Brush wear. If these elements are badly worn, the electric motor does not develop revolutions to its full capacity, and may not start (permanently or intermittently). In this case, with the appliance on, you can use an insulated screwdriver handle to press the brush against the armature. If you can see an increase in motor RPM, then the problem is detected correctly. Most likely replacing worn parts with new ones will fix the situation. Sometimes the brush holder springs also need to be replaced.

2) An armature winding short circuit. Failure of appliances with electric motors can be caused by armature breakage. If this occurs, you will notice sparking in both brushes and the armature winding will become hot as a result of one contact drawing more current than the other. If this fault can be repaired by rewinding the armature winding or replacing the whole part.

angle, grinder, does, pick

3) Stator failure. If the stator is broken, usually only one of the brushes sparks. To check this, the resistance of the armature windings needs to be tested. If both windings have the same resistance (usually 4 ohms) then the stator is fine. Different resistance on the windings indicates that the stator is defective and the winding must be rewound.

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4) Short-circuiting of the collector contacts. Wearing of the contacts causes the formation of graphite dust, which accumulates between the contacts, short-circuiting them. In this case, during electric appliance operation there appear large sparks. To remedy the damage, the spaces between the contacts must be cleaned of graphite dust. It is also necessary to check the collector brushes, because when they are properly positioned and properly shaped, dust appears in minimal quantities.

5) Soiling of the collector contacts. If the contacts are soiled by soot, both brushes will spark and the motor cannot develop to its full speed. The collector gets sooted if it gets too hot. A bad electrical contact will lead to an increase of resistance in the element which in turn will lead to more sparking and sooting. In this case it is necessary to perform cleaning of the collector contacts from carbon deposits. This should be done with sandpaper of minimum grit

It is important not to make any corruptions in the shape of the contacts. That’s why special pads should be used for cleaning

At home you can use an electric screwdriver for cleaning. Clamp the armature in the chuck, turn it at minimum rpm and put the sandpaper against the collector. Anchor rotation during cleaning must match the direction of rotation of the armature in the electrical device.

Mechanical faults

From mechanical damage most often bearings are worn out or completely destroyed. Signs of the problem may be increased vibration of the angle grinder housing, increased noise, as well as excessive heating of the housing. It is possible to remove the bearings even if you do not have a puller, you just have to gently knock them out, preferably before heating them. After replacement, the bearings should be lubricated with lithol or thiamine.

Also, as a result of continuous use of the angle grinder, it is not uncommon for the gear teeth to wear down or for one or more of the teeth to break which can be visually detected. If the wear is quite small, it can be corrected with a nail file. If the wear is high, you will have to change the gear.

If you have to use the angle grinder often, do not forget about the preventive maintenance of the tool, namely the cleaning of nodes, complete replacement of all lubricants, timely replacement of worn parts.

Do not let the angle grinder work under load for a long time at reduced speed in comparison with idling speed, try to avoid jamming of the tool.

Repairing the gears of bolt cutters with your own hands

There are two options to eliminate the malfunction of the angle grinder: to use the services of a special service center or perform repairs yourself. When repairing with your own hands you can save money, because the services of professionals do not cost cheap.

If you have the means and lack the skill, it is important to choose a repair shop responsibly. It is important that the money spent is not wasted. Here to help section of the site “Repair angle grinder,” where you can find information about companies that repair angle grinder in different cities of Russia.

In the case of a gearbox failure, you should consider repairing it with your own hands. No special tools and equipment are required for such repairs. Unless you need pullers to press out the bearings, which are usually available to the home handyman.

angle, grinder, does, pick

Spare parts without problems can be found in specialized stores.


The gearbox of the angle grinder is a mechanical part of the power tool angle grinder. It transmits the rotation of the electric motor rotor to the working tool.

The gearbox usually consists of a bevel gear pair with a decreasing gear ratio in order to provide the necessary speed of the working tool.

Gearbox broken, causes and frequent faults

Increased vibration, the presence of uncharacteristic sound during operation, strong heating of the housing, gearbox jamming during angle grinder operation require immediate intervention to determine the causes of the appearance of these factors and their elimination. As the practice of operation of angle grinders shows, the most frequent failures of gearboxes are caused by the following reasons:

  • Wear and tear of bearings with critical backlash;
  • Bearings can “crumble” as a result of shock loads during “hard” operation of the angle grinder;
  • increased wear of the bevel gear pair, breakage of the teeth;
  • untimely replacement of the gearbox lubricant or presence of low-quality lubricant in the gearbox.
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Bearing wear (Lepse)

In the following video the author makes a complete disassembly of an angle grinder brand Lepse of Russian production (Electromechanical plant in St. Petersburg, Russia). Kirov) in order to determine lack of spindle rotation when the electric motor is normally running. A complete analysis of all disassembled parts is performed.

Even high-quality Soviet bearings after 10 years of operation have a little wear, determined manually by the amount of backlash. A detailed description of what to do in such cases in the article “Replacing the bearings in the gearbox of angle grinder”. In the case of a Lepse model angle grinder, the backlash of the front rotor bearing needs to be replaced.

After replacing the defective bearing with a new one, it must be lubricated, just like all other bearings on the angle grinder.

No gear engagement (Interskol), gearbox noises/rattles

The following video shows a rattling noise during the operation of the Interskol angle grinder, which is characteristic of a failing gear pair.

The assumption was confirmed after opening the gear housing, where you can see the breakage of small drive pinion. Further disassembly of the angle grinder made it possible to determine the probable cause of the gear breakage.

Increased play in the front rotor bearing could lead to high forces in a pair of bevel gears, causing one of them to break down.

Important: increased rotor runout due to bearing damage can lead to armature contact with the stator winding, resulting in inter-turn short circuits and winding burnout. To correct such a defect would cost a pretty penny.

Backlash (CROWN, Bosch)

Increased play, not just in the rotor, but also in the spindle, could be the cause of an accident.

The CROWN angle grinder in the following video had excessive play in the spindle. The author noticed a strong end run-out of the grinding tool.

Working in such conditions can lead to the destruction of, for example, a cutting wheel, which creates an unsafe situation for the person working with the angle grinder and the surrounding people.

The bearing was replaced by the author using a bearing puller.

In the following video, the play on the spindle is noticeably greater. This is caused by wear of both bearings. the ball bearing located in the housing cover and the friction bearing located in the gear housing. Lack of lubrication. this is the conclusion made by the author, analyzing the defects.

Note the method by which the sleeve bearing is removed from the housing. The calibrated rod (in this case the drill bit guide) puts pressure on the grease that fills the cavity in the inner diameter of the slide bush.

After a load, the grease penetrates into the gap between the bushing and the housing and presses the bushing out of its seat.

Similar to the previous two, the following video shows spindle backlash in a Bosch angle grinder.

Here we show that no special tools are needed to fix the defect.

It is possible to remove and replace the roller and friction bearings without using pullers, using only improvised means, including a matching diameter of the stud bolt.

Angle grinder speed hack

Faults of the stator

Rotor bearing failure can be the cause of stator winding failure. Therefore, replacement bearings will not solve the problem of the angle grinder’s operability.

Requires knowledge of how to rewind the stator winding. The video describes how to solve this problem on your own.

The main thing is to successfully make a template and pick up a frame for winding copper wire (in the video it is a can from an air freshener).

How to disassemble an angle grinder for diagnostics

In order to make a diagnosis of the electrical part of the angle grinder, as well as to eliminate mechanical failures of the machine, it is necessary to disassemble it. Disassembly is carried out according to the following algorithm.

    Use a wrench to remove the disc or other attachment from the machine’s spindle.

    After removing the armature, the motor stator remains in the housing and can also be easily removed for diagnosis by loosening the fasteners.

Reasons for severe vibrations of the angle grinder

If you have stopped working “angle grinder“, if it is noisy, strongly vibrates or overheated, it is recommended to contact the service center, which will not only eliminate the current problem, but also will conduct a diagnosis of all units of the tool.

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The device of electrical equipment angle grinder

Over several decades, the external parameters of angle grinder almost unchanged, with the exception of improved models, which use a battery as a power source. The basis of the tool is the body with the built-in asynchronous motor and gearbox, and a handle with a protective housing is screwed on.

The power tool can be used with cutting and deburring discs, and there are also discs with sanding blades. Like all tools, the grinder can refuse to work, but more often than not, it is not so difficult to troubleshoot. It may be necessary to disassemble the housing and make minor repairs. However, it is necessary to understand the construction of the angle grinder, which has the following elements in its circuitry:

The function of all the components is very important for the proper functioning of the entire system. If any part fails, the grinder becomes a useless tool. In order for the angle grinder disc to rotate, the armature must rotate and drive the gearbox, and the faster the armature rotates, the greater will be the disc rotation speed. Collector. a peculiar part in the form of a platform, to which the contacts of the power and controlling electrical components lead. The collector accepts voltage from the brushes, and in the process, electrical energy is converted into mechanical energy.

Mechanical failure and troubleshooting

To the mechanical breakdowns of the angle grinder, you can include the following.

  • Wear of the motor armature bearings. Usually when the bearings are worn you may feel a strong vibration when the machine is running. In addition, a grinding noise and other noises can be heard. Sooner or later the bearing will be destroyed and the spilled balls will run into the gears. If this happens, then in addition to the bearing, the gears will also have to be replaced. Of course, it is better not to wait for this trouble, and at the first signs of bearing failure replace it. How to get to this part of the angle grinder was told above.
  • Wear of the ball bearing or the gearbox slide bearing. As in the previous case, when you turn on the machine will feel vibration and hear noise, unusual for normal operation of the angle grinder. To prevent further damage to the gearbox, it is necessary to replace the faulty part.
  • Gear gears are worn. Gears quickly wear out due to insufficient lubrication. This is also the reason why the gearbox gets warm. The lubrication inside the gearbox should be monitored and changed if necessary. How to Disassemble the Gearbox was described above. Grease should be used specifically designed for gear reducers angle grinder, and you can buy it in stores where this tool is sold. If for some reason the teeth of at least one pinion are broken, it is necessary to change the whole set of pinions (pair).

How to check the stator for a short circuit using a multimeter

The Anchor is the part that most often accumulates the greatest amount of dirt. If the angle grinder has malfunctioned, you can identify it yourself using a multimeter, or in other words, an ammeter.

Checking starts with finding the faulty component. If your unit has failed completely, it may be an indication of splintered brushes or a destroyed layer of dielectric between the plates. If you observe sparking inside, it means that the current collectors in the angle grinder are damaged.

Regardless of the result you get from the examination, you should check the resistance. It should be the same for each of the measurements.

If the readings show a deviation, it indicates a disturbance in the connection of the coils and a bad fit of the brushes.

Pay attention to the brushes, their wear should be the same, and in the presence of scratches they must be replaced by new ones. If you do not find faults, you need to measure the resistance of the blade and coil.

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