How To Check The Stator Angle Grinder

How to check the rotor of an angle grinder

Angle grinder is a construction tool used in cutting and edging various hard materials such as stone, metal, wood, etc.

The rotor is a part of the motor of an angle grinder that rotates during the working process, driving other components and parts of the electric tool. The quality of the cutting and grinding performed by the tool and the durability of the device depend on the work of this important part.

Control of the rotor operation is carried out in two ways. by preventive inspection and by determining the cause of the malfunction, if a breakdown has already happened.

Testing and diagnostics methods

How to check if the angle grinder rotor is working properly? It is simply necessary to check the place of engine breakdown in case of its malfunction. after all, it is this procedure that will help to understand which part of the mechanism is working and which is no longer. Diagnostics is carried out in several ways:

  • Visual;
  • Using a multimeter;
  • Light bulb;
  • Special fixtures.

Sometimes even a visual inspection is enough to understand that a short circuit has occurred. In this case, the details will show, for example, an unprotected winding, wires where the insulation will be melted. You should also pay attention to charred varnish or its smell after engine overheating.

Loss of contact also occurs due to the collection of dust (graphite from brushes) on the lamellas. It is not difficult to notice it, as well as to clean the anchor from such fine debris.

A device called a "multimeter" also helps to establish a breakdown of an electrical device. It is enough to set the resistance to 200 Ohm and put the probes on two adjacent lamellas. The resistance between all the plates will be the same during the normal functioning of the part. If the indicator is less than 1 Ohm, then the matter is in the closure of the turns. When the indicator is more than one, this means a break in the winding turns. The device can even go off scale, since the resistance in the latter case can be very high. Using an analog multimeter, the arrow will swing to the right to the very end, the digital measuring device will not show anything.

A multimeter is, in fact, the same tester that determines the resistance in the right places of power tools.

When there is no device for determining and calculating resistance, you can use a simple 12 volt 40 W light bulb. Connect two wires to the light bulb. Where there is a minus, you need to make a break. Next, we apply voltage. We apply the ends of the wire at the break to the collector plates and scroll it. When, with such manipulation, the light is on without changing the brightness, then there is no short circuit.

Another test method concerns the breakdown of the current to ground. To do this, we connect one wire with the lamellas, and the second with the iron of the armature. After we carry out the same manipulation with the shaft. In the event of a malfunction in the part, the light will glow.

In any of the ways, you can check the stator of the angle grinder, which can also be the cause of breakdown or heating of the motor.

Indicator as a way of checking turns in case of short circuit

Manufacturers assemble an angle grinder in different ways, which is why some do not show the wires that connect to the manifold. The insulation is well hidden under a bandage or opaque compound, and to check its serviceability, you can use the indicator of short-circuited turns. The device is easy to use and small in size.

To determine the short circuit, a diagnostics for the absence of open circuits is first carried out. To do this, you need a tester that measures the resistance between the lamellas. The resistance indicator should not be higher than half, if this is the case. that is, an open circuit. When the norm is displayed on the monitor, go to the next stage.

The resistance measuring device has a sensitivity adjustment function, which is also used for diagnostics. We look at two bulbs and adjust the instrument so that the red lights up. We apply the indicator to the winding, while slowly turning the armature. If the light is on, it indicates a short circuit.

Checking the angle grinder rotor by various methods

Some people test a broken tool with a tester. A fairly correct solution to the problem, but in this case, this measuring device, unfortunately, has little to show us.

You need to understand that the armature of a small motor of a construction tool has a winding and a magnetic circuit where the rotation shaft is located. One end ends with a pinion gear, the other with a lamella collector. The magnetic circuit has soft plates and grooves, which are covered with a special coating for insulation.

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As the internal diagram of the rotor shows, in the grooves of the part there are conductors of the armature winding, there are two of them. Each of them is half a turn, the edges of which are connected in pairs in lamellas. In one groove are placed: the first turn (its beginning) and the last (end), which are closed on one lamella.

So how is an angle grinder anchor checked? Rotor malfunctions can only happen in some cases and for the following reasons:

  • Breakage of conductors;
  • Turn-to-turn closure;
  • Insulation breakdown. In this case, the winding is closed to the metal base of the armature, in most cases the fault of such a breakdown is a violation of the insulating winding of the conductors;
  • Desoldering the collector output;
  • Unevenly worn manifold.

If the armature is faulty, this leads to overheating of the motor, which causes the insulation protection to melt, resulting in a short circuit of the turns. Further, there is an independent soldering of the contacts, which serve as a connection between the rotor winding and the collector plates. The current stops flowing and the tool motor does not function.

The stator of an angle grinder can also cause damage to the power tool.

Why tool failure most often affects the rotor?

During operation, the rotor is subjected to the greatest loads, namely:

  • Temperature;
  • Mechanical;
  • Electromagnetic.

In case of improper or too long operation, the breakdown of an electrical appliance may lie precisely in the armature, as the rotor is also called, which may need to be repaired or completely replaced. But before you are convinced of the malfunction of this particular part, you need to make sure whether it really is out of order.

Choke check of interturn closure

The rotor diagnostic tool helps to calculate the winding interturn short circuit. An inductor is a transformer with a primary winding and a magnetic gap cut in the core.

With the interaction of the armature (placed in the gap) and the choke, the winding works as a secondary, transformer. If, with the device turned on and the rotor lying on a metal plate, vibration or a magnetic effect is visible, there is a short circuit. Free movement of the plate along the turns indicates the full serviceability of the armature.

Causes of malfunction and characteristic symptoms

The main factors that affect the failure of the stator are as follows:

  • The supply network does not always guarantee a stable voltage, its surges are possible;
  • When using the power tool, liquid such as water may enter the stator;
  • When processing some materials (concrete, wood and others), a sick amount of dust is formed, from which it is difficult to protect the stator winding;
  • Long-term operation of the angle grinder under overload conditions, which causes the power tool to overheat;
  • During operation, do not stop the angle grinder by pulling the cord out of the socket suddenly.

How To Check The Stator Angle Grinder

408-105 Stator for Hitachi G18SE3 and HAMMER angle grinders. Photo 220V

Typical signs of a stator malfunction are as follows:

  • A persistent smell of burnt insulation of the winding wires appears;
  • The temperature of the body parts of the angle grinder rises noticeably;
  • The electric drive of the angle grinder hums more than under normal conditions;
  • The appearance of smoke is quite real;
  • The spindle starts to rotate more slowly, or even may stop completely;
  • The opposite to the previous case, the other extreme is possible. the spindle starts to spontaneously work at increased speeds, it is peddling.

Visual inspection for malfunction

The very first and easiest way to determine if the stator is faulty is to visually inspect it. For what it is necessary to get it out of the body of the power tool. Disassembly here will not present any difficulties. The main thing is to free it from all other structural elements of the angle grinder, including the rotor. This will make it possible, with appropriate good lighting, to inspect all surfaces of the stator winding. Usually, charred areas appear in the cliffs, which allows us to conclude that there is a defect. If visual inspection failed to identify a malfunction of the stator, you should resort to using special devices.

How to ring the stator angle grinder

408-317 Stator for BOSCH GWS7-125 / GWS7-115 HAMMER. Photo 220V

The stator as an element of the electric drive of the angle grinder participates in the creation of an electromagnetic field in which the rotor rotates, creating a torque on the spindle shaft. During operation, for a number of reasons, it fails. The user can independently diagnose damage and repair the stator.

  • Device
  • Causes of malfunction and characteristic symptoms
  • Visual inspection for malfunction
  • How to check the stator winding of an angle grinder at home in different ways
  • Checking the armature / rotor and stator with a multimeter / tester
  • On turn-to-turn circuit, indicator
  • Makita, without instruments
  • Multimeter. automatic: quickly and efficiently performs measurements


The stator of the angle grinder is a fixed structure in the form of a core made of sheet electrical steel. It has grooves in which the winding is placed, twisted in a certain way, its wires are located parallel to each other, to reduce eddy currents.

408-316 Stator for BOSCH GWS6-100 / GWS6-115 HAMMER. Photo 220V

The winding is necessarily covered with an electrical insulating varnish in order to protect against possible shorting of wires between themselves. In the grooves of the cores between the coils, insulation is made of electrical cardboard, glass tape and other similar materials. In the vast majority of grinder models, the stator is tightly seated inside a high-strength plastic housing, which protects the entire electrical part of the angle grinder.

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Checking the armature / rotor and stator with a multimeter / tester

In the following, a multimeter device or, as more often in everyday life, called a tester, is used as a tool for diagnosing the rotor and stator of an electric drive. It is used to measure various electrical parameters: resistance, current, voltage. To determine faults in the form of wire breaks, breakdown of the winding to the case, the "ohmmeter" mode is used, that is, a certain resistance value is set, which is comparable to that available in the tested circuit. In this case, with a limit of 200 ohms.

Breakdown of the stator to the housing is determined by applying indicator probes to its housing and one of the ends of the winding. The presence of any resistance value on the indicator indicates the presence of a defect in the form of a breakdown of the winding onto the case. When diagnosing a winding break, the indicator of the device will not show anything when combining the probes with the winding leads.

complex manipulations should be carried out when checking the rotor windings of the electric drive. A winding break can be in any connection with a single collector lamella. Therefore, it is necessary to check the resistance between all collector lamellas by applying indicator probes to them one by one. In the absence of a break, the resistance will have the same small value in all cases. Any deviation indicates a break. The breakdown of the winding on the case is checked with probes when they come into contact with the collector and "iron" from a set of sheets of electrical steel. The indicator scale should not react to this action.

However, it is impossible to determine the turn-to-turn circuit with a multimeter. Here, a device called a short-circuited loop indicator (IKZ) is used. details about it in the information below.

Makita, without instruments

In one of the Makita models, the next one emitted smoke during operation, which is a sure sign of a burnt out rotor or stator. To determine the reasons, the author performed a complete disassembly of the angle grinder, which makes it possible to perform a good external examination of the angle grinder units suspected of malfunctioning. If there were no signs of smoke consequences on the rotor, then on the stator several places of burnt electrical insulating varnish were clearly visible.

How to correctly determine the malfunction of the rotor rotor of the Makita rotary hammer and choose brushes

All power tools begin to fail over time. Faults are divided into mechanical and electrical. The most common electrical faults are faults associated with the failure of the brushes. In second place: failure of the armature bearings. Less common are stator or rotor failures. And how to correctly determine the malfunction of the stator, rotor of the Makita 2450 and 2070 hammer drill, replace the brushes? And here the circuit diagram of the Makita 2450, 2470 perforator will help us.

Installation of brushes

Before inserting the brushes into place, it is necessary to clean the brush holders from carbon deposits. This is done with a rag soaked in solvent. It is preferable to remove carbon deposits in the form of particles obtained with intense sparking with a small file. The cleaned brush holders are installed in place, brushes are inserted into them and clamped from above with latches.

The brush is installed in the brush holder

Checking motor windings

The electronic rotor tester is a standard digital multimeter. Before proceeding with the short circuit test, you should check the multimeter and its readiness for operation. The switch is set to measure resistance and touch each other with the probes. The device should show zeros. Set the maximum measurement value and check:

  • First, check the rotor for an open circuit. Touching the black probe to the slip ring, you need to ring the windings with the red one. The arrow of the device is off scale, which means that the winding has an open circuit of turns. The rotor should be rewound;
  • We measure the resistance to determine the possibility of a short circuit to the case. We attach a black probe to the slip ring, red should ring the rotor housing for a short circuit. In the case of a low reading of the resistance value and a sound signal, such an anchor must be returned for repair;
  • Carrying out a ringing on the turn-to-turn closure of the rotor turns. We reinforce the probes on the armature slip rings. With a value on the scale of the device, from 1.5 ohms to 6 ohms, we checked a working device. All other values ​​on the scale indicate a malfunction of the multimeter.

This completes the rotor check. It should be recalled once again the main stages of determining the malfunction. Disconnect the power supply before checking the angle grinder or any other device. Before taking measurements, visually inspect the housings, insulation and the absence of carbon deposits on the stator and rotor.

It is necessary to clean the contact surfaces from clogging with dust and dirt. Contamination leads to increased current with loss of motor power.

When disassembling the instrument for the first time, write down all your steps. This will allow you to have a hint next time, to avoid the appearance of unnecessary parts during assembly. If the brush extends beyond the edge of the brush holder less than 5 mm, such brushes should be replaced. You can check the turn-to-turn circuit with an electronic tester, that is, a multimeter.

How to make your own brushes?

The cheapest way is to pick up electric brushes from other models of power tools by sharpening them to the desired size with an ordinary file. This is economical, but they will last less than the original ones. Alternatively, you can adjust the carbon rod of the battery or other elements.

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Various batteries

We need to take the battery and pull out the central carbon electrode from it. The electrode must be grinded with needle files to the required size of the old electric brush. (This is informational information and is not essential for use)

It is worth noting that the quality of graphite directly affects the service life and sparking.

Homemade carbon rod brushes

After making sure that the brushes are worn out, select analogues.

Installing and assembling a new rotor

Rotor replacement does not require special knowledge and can be done by any user.

The rotor is inserted into the mechanical block with a helical gear until it fits snugly.

Remember! It is very important to correctly install the bearing pos. 56 and the rubber ring 10 pos. 77. In the Makita 2450 hammer drill, the bearing 607LLB pos. 56 or the domestic analogue 80017 is used on the rotor from the collector side, and the bearing 609LLU pos. 51 or analog 80019.

Correctly fitted rubber ring 19

Having installed the rotor, closing it with a case, put the electric brushes in place and check the operation of the puncher.

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All! You have coped with a difficult task. The punch works.

Checking the stator and rotor of power tools for interturn short circuit

It does not take much time to check the stator and rotor for turn-to-turn circuit with a multimeter. It will take longer to disassemble the engine. Angle grinder, drill, hammer drill. every tool can be repaired with a fault. It is better to break the check into several main stages, and consistently slowly perform the actions.

Rewinding the stator do-it-yourself angle grinder

408-317 Stator for BOSCH GWS7-125 / GWS7-115 HAMMER. Photo 220V

An asynchronous collector motor is used as an electric drive in angle grinders. One of the main components of its design is the stator, which always works in tandem with the rotor and creates a magnetic field with which it rotates. In the event of a malfunction of the stator, the angle grinder fails and must be repaired. There are two main ways to repair the stator. either replace the defective stator with a new one, or by rewinding, the burned-out winding is changed to a new one. Such repairs, when done independently, require certain knowledge and skills. The article describes tips for those who want to learn how to do it yourself.

  • Angle grinder and stator device
  • Causes of breakdowns
  • Major malfunctions
  • How to call
  • Winding diagram, how to choose the thickness of the wire
  • Required tools
  • How to rewind at home, stages of work
  • Rewinding spools using a template
  • Rewinding windings directly on the core
  • It is not always possible to find the right template
  • Repair technology with a detailed description of varnish impregnation after rewinding

Rewinding spools using a template

The author of the following restores the stator of the Temp model angle grinder with the help of objects that can be easily found in any household. So the base (template) for winding the wire was taken from a can of air freshener. Important: the diameter of the cartridge must correspond to the diameter of the wire sample formed according to the dimensions of the stator slots.

Required tools

Locksmith solid-forged hammer 500 gr. Inforce. Photo VseInstrumenty.Ru

Typical repair tool kit.

  • Various hammers: metal, wood, several sizes.
  • Pliers, round-nose pliers, pliers are used to manipulate the coils.
  • Cleaning the stator surfaces from dirt and insulation is carried out with a metal brush.
  • The required cleanliness of the stator surface can be obtained using an electric drill with appropriate attachments.
  • In addition to a micrometer, for less critical measurements, a caliper and a ruler are used.
  • You can control the electrical parameters of the coils after rewinding with a multimeter.
  • Shims, insulating cardboard, keeper tape special varnish for impregnation. auxiliary materials for repair technology.

Causes of breakdowns

408-105 Stator for Hitachi G18SE3 and HAMMER angle grinders. Photo 220V

The most common cause of stator failure in an angle grinder is a violation of operating conditions. Induction motors have the ability to maintain speed regardless of the magnitude of the applied load. This is both an advantage and a disadvantage.

The ability to perform work under heavy loads is accompanied by overheating of the tool, which contributes to the occurrence of malfunctions in the rotor and stator windings during long-term operation. Under the influence of high temperature, the protective layer of the insulating coating burns out, which leads to the failure of electrical components.

It is not always possible to find the right template

In the following, the author warns those doing do-it-yourself rewinding about the difficulties with choosing a template. It is not always possible to choose the right one right away. Guaranteed high-quality rewinding provides a much more laborious, but reliable method directly on the "hardware".

Angle grinder and stator device

Stationary induction motors usually have a special housing where the stator and rotor are securely attached. In angle grinders, the role of the supporting element for the main units of the electric drive is played by the body of the power tool itself. It is usually made of high-strength plastic, into which the stator fits tightly. This design significantly reduces the weight and overall characteristics of the angle grinder, which is important for hand-held household devices.