How to replace the brushes on an angle grinder

Angle grinders (angle grinders) are one of the most common electrical tools, not only in professional use, but also in domestic. Anyone who works with power tools regularly has to deal with the problem of replacing defective brushes with serviceable new ones. Brushes are designed to supply electric current to the collector and they look like carbon parallelepipeds with an electric contact. Every brush will eventually wear out and compromise its function. From this power tool can work unstably, jerking, twitching. As a result, there will be a smell of burning, and the motor will stop at all. To prevent this from happening, brushes should always be replaced on time. Remember that their timely replacement ensures not only the safety of the tool, but also the operator. In this article we will tell about how to properly change the brushes in such a tool as an angle grinder, it also angle grinder.

This option is the easiest. But it can only be realized in those grinders that are equipped with special quick-access brush compartments. Usually they are located on the side of the tool. To change the brush, you need only unscrew the brush compartment cover, pull out the old worn out brush and put the new one in its place. Everything is very simple. And this procedure takes only a couple of minutes. The main thing that the brushes fit the model of the angle grinder.

Features of brushes

If we talk about electric brushes, you should first explain the name. Brushes this device was called in the early days of its existence (early XX century), when, indeed, to remove current from the rotor of the electric motor used the construction, resembling a brush or, more precisely, a brush. Such a device, despite its high efficiency, turned out to be too short-lived and was replaced by a more solid one, made of thick material, in which a copper wire is pressed.

The movement of the rotor of the electric motor causes constant friction on the working surface of the electric brushes, which is the main reason for the failure of this part. As a result, they need to be replaced periodically. This process is natural and inevitable with the long-term use of any power tool. It is very easy to detect brush wear and tear: previously reliable unit will work intermittently, the characteristic ozone smell from the abundant formation of sparks in the current collector may appear. It is advisable to replace the brushes at the first signs of wear and tear.

They come in graphite, carbon, or metallographic brushes. In all varieties, carbon is the basic material.

In the first case, the product is pressed under high pressure and then treated thermally, gaining increased wear resistance. The carbon version is the cheapest, as it does not need any thermal treatment. These brushes are the least durable. Metal brushes are the most expensive because, in addition to carbon, they contain metallic powder. This is the most wear-resistant option, which you can rarely find in household appliances. As already mentioned, the brush is also called a removable nozzle for the angle grinder.

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In order for the grinding machine (angle grinder) to perform its main functions, it is necessary to install a particular attachment. It can be cutting or sanding discs or brushes with different kinds of lint fixed in a circle. Such a detachable device is called a cord brush or shorter. a cord brush. Brushes are a consumable item, as are grinding discs. They wear out in the process and must be replaced. Brushes for angle grinder are arranged in such a way that they are installed on the rod thanks to the hole in the center, this is their main difference from brushes for a drill, which have a shank for their installation in the chuck of the drill.

Depending on the specific application, the brush filaments can be steel, brass, polymer fibers, or even wool.

Electronic unit in the angle grinder

Electronic unit allows you to combine the speed regulator and soft starter into one. The electronic circuit is implemented on the principle of pulse-phase control with a gradual increase in the opening phase of the triac. Angle grinders of various capacities and price categories can be equipped with such a unit.

Variety of units with electronic unit: examples in table

Name Power, W Maximum rotational speed of the disc, 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

Brush replacement

Here is where the question arises to the manufacturers of lathes, why not make a window in the body of a transparent plastic to visually assess the condition of the graphite contacts without disassembling the power tool (in some models of lathes there is no need to unscrew the body)?

Warning! Before replacing the brushes, you must disconnect the power supply by pulling the plug out of the socket, just like with any other penetration into the housing of the power tool.

DeWalt Grinder Repair. How to Replace the Brush

replace, brushes, angle, grinder

Due to the design diversity of angle grinders, the replacement of graphite contacts in each tool model may have its own characteristics.

Option 2. Replacing brushes directly in the body of the angle grinder.

If the tool is not equipped by the manufacturer with a quick brush changing system, the angle grinder has to be disassembled for this procedure. To begin with, you need to read the manual to the tool and its scheme, if they are available in the kit. Usually the angle grinder body consists of two parts, fastened together. After you have disassembled the housing, remove the old brush from the brush holder and replace it with a new one. Make sure the brush holder holds the brush firmly against the collector. Try to use only original brushes suitable for your specific tool model. However, if you do not have the opportunity to buy one, and you could not find an analogue. the brush can be adjusted to the size you need. It’s easy enough to do with a fine file. When adjusting, take your time and scrape off the brush gently. The main thing is that it did not end up being smaller in size than the original one.

How to change carbon brushes on an angle grinder

Separately, it should be noted that the replacement of brushes on the angle grinder is not complicated at all. However, when going to conduct it, make sure that your angle grinder is not already in the warranty period. Simply put, usually manufacturers are against any unauthorized introduction to their products. For such maintenance, there are special service centers. If you violate the warranty agreement by penetrating into the tool, the manufacturer will simply refuse free service or replacement of the tool as a result. In short, there are different cases. After all, each manufacturer has its own rules, so before you disassemble the angle grinder, we recommend that you carefully read the warranty card of the tool.

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Diagnosis of faults in the work of the angle grinder

Before you try to disassemble the angle grinder, you need to diagnose the breakdown. Before the final failure, the following signs can appear:

  • Strong vibration is observed;
  • Brushes of a collector can spark;
  • the motor may start with a dull hum;
  • jamming the bearings of rotation;
  • There is an odor or smoke from the housing.

Checking of electrical parts

The electrical part of the tool includes the following elements:

Please note! To check their work requires the use of special devices. So, you can use a tester or multimeter.

Check power circuits

First you need to assess the integrity of the power cord. There should not be any signs of damage. You can also switch the tester to voltmeter mode and estimate the input voltage in the angle grinder. It must be 220V.

replace, brushes, angle, grinder

Checking the starter and control box

Then it is recommended to test the operation of the start button. The function of the electronic control box is important. It is not uncommon for the switch contacts to become oxidized or clogged.

Diagnosis of the rotor. how to “sound” the armature with a tester?

Use a tester to find out how the rotor works. To do this, turn on the multimeter to 200 ohms and evaluate the resistance of the windings one by one. If it is identical at all points, this indicates the integrity of the armature. Otherwise the element must be replaced.


Diagnosing the Electric Motor Stator

If the armature is good, all manipulation is done with the stator. Here it is advisable to evaluate the winding resistance. When rewinding coils, it is necessary to use a special template made of plywood.

For your reference! To correctly rewind the stator of your tool, we recommend that you read the following video. It helps to get the right result and avoid mistakes.

Checking the mechanics of the machine

To determine if there are any mechanical components that are broken, it is advisable to disassemble the housing. The gear cover is normally secured with 4 screws. They need to be unscrewed to get to the pair of gears.

Inspecting the gears

When inspecting the gears, you need to evaluate the strength of the gear mount. The amount of lubricant and the structure of the teeth are of importance.

replace, brushes, angle, grinder

Inspect the locking button

This element is a spring-loaded steel rod that prevents rotation of the operating shaft. Button is used when changing cutting discs. Breakdowns can occur if a disc jams. It also occurs when the motor is switched on with the button depressed.

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Inspect the nozzle mounting flange

The angle grinder disc is secured with a flange-threaded clamping plate. It has a simple construction and therefore breaks very seldom. When inspecting you need to familiarize yourself with the condition of the thread. If necessary, this part can be treated with solideol.

Checking rotor shaft bearings

To assess the performance of these elements, they need to be visually inspected. If the bearings are in good condition, they have a solid color and rotate easily when turning.

How to disassemble the angle grinder

When identifying the causes of malfunction, you need to start repairing the angle grinder. It is important to know how to disassemble the angle grinder. The following rules should be observed:

  • unplugged;
  • Place the tool on a well-lit table or workbench;
  • Adhere to the order of disassembly and reassembly of the device.

What an angle grinder is used for and how it is built

Angle grinder (angle grinder), or “angle grinder“, has firmly entered the domestic and industrial life of not only a craftsman, but also ordinary man, who likes to comfortably solve locksmith and carpenter problems. The popularity of this power tool is due to its simplicity, versatility and versatility of use.

With a variety of optional accessories angle grinder can cut metal, sand various surfaces, clean them of rust or old paint coatings. In the arsenal of angular grinder has such functions as sharpening cutting tools, grinding concrete walls, cutting ceramic tiles or stone.

Angle grinder construction

Structurally, the angle grinder is an electric motor of 500 to 2000 W, which converts the power of electric current into rotary motion. The planetary gears serve the same purpose, consisting of two main gears with straight or bevel gears. The spindle is rotated in a direct drive mode, the speed is determined by the ratio of the number of teeth in the gearbox. Some angle grinders are equipped with an electronic soft-start motor and variable speed control.

Professional angle grinder with adjustable engine speed

Electric motor type. asynchronous, single-phase. The electromotive force is created by interaction of the rotor winding in the magnetic field of the stator fixed in the housing. Thanks to the angular transmission of torque, the level of safety at work is greatly improved. In case of disc jamming in viscous material, there is no reactive rotation of the tool body, which prevents possible injury to the operator.

Many people have experienced in their own practice the phenomenon of reactivity in an electric drill. When the drill jams in e.g. hardwood, the body of the device starts to rotate violently in the opposite direction, pulling out of your hands and can cause injury or even maiming.

angle grinder with backhandle

angle grinders with a backhandle allow you to reach the brushes in a slightly different, simpler way:

  • Near the handle, you should find a small repair window covered with a plastic plate that is secured with a self-tapping screw.
  • Unscrew the self-tapping screw, use a screwdriver to pry the plastic plate out of the housing, opening the repair window.
  • The following steps for replacing the brushes are the same as for low-powered grinders: release the belt spring (1), release the plug (2), remove the brush from the guide block by the wire.
  • Then insert a new brush, connect the plugs, secure the graphite rod with a tape spring, cover the repair window with the plastic plate and screw in the self-tapping screw.
  • Repeat all steps with the second brush on the opposite side of the housing.

There may well be other ways to replace the graphite brushes due to the design features of the grinder.

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