How to change a bearing on a grinder. Repair Ushm Makita


Angle.Grinding machines (Ushm, Bulgarians) under the German brand Bosch are of high quality, reliability and durability. The main competitive advantage of Bosch angle grinders is the widespread use of innovative technologies in the manufacture of the product.

But German quality cannot resist Russian negligence. Improper use of the tool, untimely replacement of lubrication, coal brushes, bearings leads to the failure of the tool.

In order to repair the Bosch corner grinding machine, you can go in two ways: to give the grinder to the service center or to repair the Bosch grinder with your own hands.

The first option is more costly and not always of high quality. The second option can only be carried out if the consumer has a great desire to figure it out on its own.

Bosch Bold Scheme will help to carry out repairs on your own.

Bosch grinders are conditionally divided into low-power up to 1000 watts, and powerful over 1000 watts are labeled GWS 7-125, GWS 20-230 or others.

The first digits 20 or more indicates the power of the tool of more than 1000 watts. The second number 230 certifies that this is the maximum diameter of the detachment circle.

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The first digit of up to 20 indicates the power of the tool up to 1000 watts, and the second about the maximum diameter of the cutting circle up to 125 mm.

Mechanical malfunctions of Ushm

Bulgarian is an angle grinding machine designed to perform cutting, grinding, polishing work. The Bulgarian in the process of work is subjected to heavy loads, works in an dusty environment.

Excessive loads when using the grinder in the “cutting” mode cause increased wear of not only the bearing, but also the teeth of the gears of the gearbox.

The main malfunction of the grinder by the mechanical part, wear or destruction of the sliding bearing on the shaft of a large scooter of the gear of the gearbox.

It is not difficult to eliminate the malfunctions of the grinder if there is its scheme, description and recommendations for repair work at hand.

Repair of sliding bearings

The weak point of any corner grinding machine is bearings. And although there are only three of them in the design, they most often lead to mechanical breakdowns. The bearings have a negative effect:

Makita Angle Grinder Repair – How to replace the Ball Bearing 629LLB

  • High speed of rotation;
  • Work at maximum modes;
  • Insufficient lubrication;
  • Dust or dirt hit;
  • Untimely replacement or destruction of coal brushes.

The design of any grinder provides for a quick and not constituting complexity replacement of any bearing.

Bulgarian malfunctions associated with wear or destruction of the sliding bearing on the gearbox shaft are characterized by the appearance of an unpleasant extraneous sound.

Destruction of the sliding bearing is detected by checking the backlash of the installation shaft of a working tool. It is determined by swaying in different directions of the shaft when installing a working tool.

During the next installation of a working tool, check the ramp of the shaft, swaying at the end in different directions. The backlash should be absent or minimal.

The appearance of the backlash indicates the need to replace the sliding bearing.

The repair of the bearing is to extract it from the case and remove the gearbox from the shaft.

change, bearing, grinder, repair

It is better to remove the bearing from the shaft using the puller. It is best to get the internal clip of the destroyed bearing with a tap of the desired diameter, previously screwed into the clip.

The bearings are removed from the rotor using a puller or a folk way.

The keys or strips of metal are inserted into the vice, the bearings are laid on the keys and with the help of an infusion made of soft metal and a hammer weighing at least 400 g are pierced from the shaft axis.

Repair of the grinder gearbox

The degree of wear of the gear of the gearbox of the grinder is checked for the contact spot. Previously, the gearbox is completely cleaned of the old lubricant. A special blue is applied to the small gear of the gearbox, the gear. Next, you need to remove the driven large braid gear and look through the magnifying glass on the contact spot. It should occupy a total of at least 50% of the tooth surface.

Otherwise, the gears must be replaced or adjusted to the tooth profile. Correction of the tooth profile has been described more than once on the pages of this site.

But such a malfunction is eliminated only by an experienced master.Most often, licked, cut or destroyed gears change entirely, and in pairs.

How to change a bearing on a small grinder

Search for defects and repair of a grinder in artisanal conditions

The owners of the power tool are perfectly clear that it does not matter which equipment needs repeated maintenance. Some nodes require lubrication, others wear out and are replaced. However, in most cases, the masters operate the device until the details begin to spill out of the body. Then you have to solve critical measures to restore the usual mode of operation of the tool. The most to find out what has broken, check the grinder for performance and carry out repairs on your own?

Why is Ushm used and how it works

The corner grinding machine (Ushm), another “Bulgarian”, firmly entered the household and production life of not only a artisan, but also an ordinary tradesman who likes to comfortably solve locksmiths and carpentry tasks. The popularity of this power tool is justified by the simplicity, versatility and multifunctionality of implementation.

Using various additional nozzles of the grinder, metal can cut, grind different surfaces, clean them of rust, as it is also called old paintwork coatings. In the arsenal of Ushm, of course, functions such as sharpening cutting tools, stroke of concrete walls, cutting clay tiles or stone.

Bulgarian device

Structurally, the Bulgarian is an electric motor with a capacity of 500 to 2000 watts, which converts the power of electronic current into rotational movement. The same purpose is a planetary gearbox consisting of 2 main gears with a straight or conical gear gear. The rotation of the spindle of the working shaft is carried out by working in direct transmission mode, the speed is determined by the ratio of the number of teeth of the gearbox. Some grinder are equipped with an electric unit of smooth launch of the motor and adjusting the speed of rotation.

The type of electric motor is asynchronous, single.Phase. The electric motor appears with the promotion of the rotor winding in the magnetic field of the stator, which is unlimited in the case. Thanks to the angular transmission of the rotational moment, the level of safety increases significantly during operation. For which the design of the disk jacket in viscous material is intended, there is no reactive rotation of the tool body, which prevents the probable injuries of the operator.

Probably experienced in their practice the phenomenon of reactivity during the operation of the electric drill. When the drill jams, for example, in a solid wood breed, the case of the device begins to spin with force in the back, breaks out of the hands and leads to injury in other words.

Diagnosis of defects in Ushm works

Signs of incorrect operation of the grinder for the penetrating ear and sharp.Eyed eye arise for a long time until the actual failure of the tool. Ahead of time before it is completely broken, the Bulgarian usually begins to give distress signals. You will like this more:

  • High vibration of the body at one time of operation;
  • Excessive sparking of collector brushes;
  • Uterine buzz of the motor at one time of inclusion;
  • The crackle of the gearbox with broken teeth or drying without lubrication with gears;
  • Braining the rotation of the rotor shaft in other words, their penetrating creak at one time acceleration;
  • A specific smell or even smoke emanating from the Ushm case.

To save the grinder from a large and expensive repair, one should closely relate to the technical condition of the tool and respond to configuration in its work in time.

If the 1st symptoms of incorrect work have appeared in the works of the grinder, you need to urgently diagnose the device and find the cause of the problems. For this purpose, it is necessary to check the two main ones that allows accounting (software) of the device. Electronic and mechanical.

Checking the electronic part

The electric motor, as a rule, is divided into two main parts. The stator and rotor (in other words of the anchor).

The task of the master is to alternately check these that allows accounting (software) that allows you to keep accounts and find the prerequisites for problems in the work. For this purpose, a multimeter or tester is useful.

Checking the power circuits

First of all, you need to check the integrity of the network power supply. Probably troubles, of course, occur only because the cable has damage and the power supply is uneven. The cord is completely intact, without signs of damage. At one time, he should not heat up as he is also called sparking in the places of excesses and connections with a socket or grinder. If at least one of these criteria is not observed, the cord should be repaired or replaced.

Using a tester included in the voltmeter mode, check the input voltage in the Ushm, it must correspond to passport indicators: 220 V. Working in the ammeter mode, the current consumption is measured. It should not exceed value 6 A.

Checking the start and control unit

Next, testing the start button and the control unit. Maybe the contact group of the device turned on the operation was oxidized or clogged. If the device is equipped with a smooth launch system, the disk should accelerate to operating speeds evenly, without a sharp set of speed. Using the multimeter, you need to make sure that the voltage when turning on the button is transferred to the electronic circuit.

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If during the work of the grinder it was seen that the brushes at the place of contact with the collector are extremely sparkled or the disk is spinning unevenly, spasmodically changing the amount of rpm, then, most likely, the windings of the stator or anchor are involved in this. Because the stator is least susceptible to overloads. It only creates a magnetic field, then in most cases attention should be paid to the rotor rotor.

Diagnosis of the rotor. How to “call” the anchor by the tester?

To make sure the rotor is working, you need to “call” it by the tester.

By installing the multimeter switch to 200 Ohms position, alternately measure the resistance of the windings on 2 adjacent anchor lamellas. If the resistance is monotonous everywhere, it means that the anchor is intact and is efficient. If the tester indicates good from the other significance on any of the lamellas of lamellas, an interval circuit came out in this matter. The anchor must be repaired in other words.

How to extract/remove a needle bearing in a grinder

It is not difficult to press out a new needle bearing, but The use of the original puller is required to remove. The next video The author describes Production of such a device And its practical action is shown.

The puller is Podsiece tsianga with burtles At the ends of mobile petals. The dimensions of the tsangi are made on a lathe, and the central hole is sparkled under the piercing petals of the rod. The puller is inserted into the bearing and the beams after moving the rod along the hole are uplift and rested with the side surface against the end of the ring. With the help of not very spectacularly looking, but reliable levers of reinforcement with sharpened edges, resting on the puck inserted, the bearing can be removed from the case.

change, bearing, grinder, repair

Important: The needle bearing has a resource of work much larger than a sliding bearing. However, the shaft of the spindle wears out, which also needs to be changed. In the video described, the author found a replacement option. However, in most cases, this can create additional problems.

How to change

Regardless of the models of the Bulgarians, the technique of replacing bearings is not much different from each other. Correction of repair technology is connected With design features, which every brand has.


The next video describes Replacing the bearings of the gearbox of one of the Bosch models, which has a large backlash on the spindle. Here the main executive body, which creates the efforts of extinguishing/pressing, serve Ordinary locksmith vice. The use of various extensions in the form of the corresponding in size of pipes and other similar details allows you to transfer efforts to the right place of the structure using the movement of the viges of the vice. Some operations are performed With the help of extensions and light beats of the hammer.

A feature of the design is A flange flooded with plastic. For extinguishing/pressing the flanberry bearing, the author using a knife and burner removed plastic interfering with this process. Perhaps, if there are a turner skills, just cut off this material on the machine.


One of the Makita models describes the process of replacing bearings without the use of special tools, by any affordable improvised means. As basic surfaces Wooden bars are used from hard rocks that perceive the load when performing various technological operations using force exposure.

As equipment are used metal sheets suitable in thickness and end heads (you can use suitable pipe size) when knocking out bearings. The central holes of the shaft serve as a base for a pointed rod (in the video it is a modified old screwdriver), with which the shaft itself is released itself. The only tool for industrial production is Stop rings puller, Although without it you can figure out what to remove them with the help of improvised means.


Some design of bearing nodes are performed Without the use of landing. So, for example, in the next video ball bearing lids of the gearbox body of the intercol model gathers in the supporting structure using the puck, Fixed with threaded joints. For a better fit to the plane of the case, the surface of the washer is covered with adhesive composition.


Some designs of bearing nodes At first glance, they exclude the replacement of the bearing itself directly, in such a knot. However, the author of the next video found a way to do this in one of the Hitachi models and thereby save a decent amount of money proposed in the proposed way.

To fix the bearing node, a crown on a tree approached the drill, in the inner surface of which one of its external diameters sits tightly. With a working drill Using a sharp object, plastic material is removed to the size of the outer ring of the bearing. Thereby nothing prevents the bearing with a hammer and extension.

Further when assembling a new bearing Instead of rushed plastic, a ring is inserted (In the video, it is most likely from the Kaplon or other similar material). Since the ring in the video has a wall thickness that does not allow the assembly of the gear according to technical requirements, using the chisel, the inner diameter is finalized to the desired size.


In the next video, one of the models of the SPARKY brand grinder was failed. To determine the cause of the malfunction author made a complete disassembly of the grinder with a sink and cleaning all the details. Details on the process of disassembly in this video did not stop. This technological operation can be viewed in the article on the link “How to disassemble a gearbox”.

After analyzing the state of nodes and details, it turned out that The cause of the malfunction of the grinder was the front bearing of the rotor. He was easily replaced with a new one, which inserted into the gearbox body without an interference and fixed with a puck using threaded screws. SPARKY Bulgarhaka is 15 years old, therefore, other defects are not excluded and the author correctly draws a conclusion about the acquisition of a new grinder.

Sections: gearboxes, repair of Bulgarians with your own hands

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A couple of words about lubrication

The reliability of the reducer and its durability largely depend on the timely replacement of the lubrication and its correct selection.

A large assortment of lubricants is presented in the Russian fuel and lubricants market. Among them are lubrication of Russian manufacturers.

Modern tool manufacturers strongly recommend using lubricants of only their own production. This is the manufacturer’s policy.

From Russian lubricants, we recommend using lubricants specially designed for gearboxes.

But not only properly selected lubrication affects the quality of the work of the grinder, but to a greater extent its timely replacement! Do not tighten with the replacement of lubrication, follow its condition.

What repair of a grinder with your own hands can make a user

Although the Bulgarian is not an instrument of particular complexity, the user may not carry out repair work on all nodes.

Along with a simple replacement of bearings or gears of the gearbox, there are such malfunctions that cannot be made without special equipment or devices.

  • To extinguish the driven gear, you will need a press. It will not be possible to wrap the rotor without devices.
  • Such malfunctions include failure of the rotor. For a simple consumer, such a malfunction ends with going to the service center.
  • Advanced users can revive a burned rotor, having certain skills and concepts. But sometimes it’s easier to buy a new one than to rewind.

For most users, the repair of the grinder with their own hands is limited to a certain circle of malfunctions.

Systematization of malfunctions of the electrical part of the Ushm

  • The simplest malfunction for which the Bulgarian does not turn on is the break of the power wire. Most often, a break in the power cord near the fork or at the entrance to the tool. The malfunction is easily eliminated by replacing the power cord or removing a ragged piece of wire.
  • Strengthening heating in the area of ​​the installation of coal brushes. Most often, such a malfunction appears due to shortening of coal brushes less than a nominal size. The length of coal brushes cannot be shorter than 8 mm.
  • Wantle the Bulgarian Turn button. The malfunction is related to the burnout of internal contacts in the button. Eliminated by the complete replacement of the circuit breaker with a new.
  • In some USM models, a device has been used to smoothly adjust the revolutions of the grinder. Ushm revolutions improves the smoothness of turning on the grinder and prevents the bite of the working body. Repair of the speed control regulator is the full replacement of it.

Grouping malfunctions by the mechanical part of the Ushm

  • The appearance of extraneous noise in the gearbox of the grinder, heating the gearbox. The malfunction is associated with the destruction of the supporting bearing, the wear of the teeth of the gear of the gearbox, drying out the lubricant. Eliminated by replacing the gears with high tooth wear. With a slight wear of the teeth of the gears, you can try to fix it. The tooth profile is corrected manually by drinking with a round suprafil and drill. The lubricant is replaced by a new one for each repair of the gearbox. New grease is applied to carefully washed parts.
  • The replacement of the bearing is required when it is destroyed or the appearance of a large backlash. In some models, the bearing is planted on a spindle with an interference. Replacement requires special equipment, in particular, the press. Details must be cooled or heated.
  • Replacing bearings on the rotor is required when a large beating appears. The presence of an increased beating is easy to see on the rotor collector and the intensity of the wear of coal brushes.
change, bearing, grinder, repair

Makita Angle Grinder Repair – How to replace the Ball Bearing 696ZZ

Simple malfunctions and methods of diagnosis and elimination with your own hands

If you do not turn on when you press the “Start” button, then the check starts with the inspection of the cable at the entrance to the tool.

Unscrew the cover of the grinder and check the integrity of the power cord using a tester or phase. Strictly follow the safety rules.

If the power cord is intact, and the grinder does not turn on, replace the “Start” button.

If when installing the new button, the Bulgarian did not work, check the quality of fastening of coal brushes and their dense fit to the rotor manifold.

Complex malfunctions and Ushm repair with your own hands

The types of breakdowns below require certain knowledge and skills to eliminate them:

  • Jamming or destruction of bearings.
  • Licking or destruction of the teeth of the gears of the gearbox.
  • Cliff or short circuit in the rotor or stature.
  • Failure of the details of the control circuits.
  • Destruction of the gearbox.

The main stages of work

Further, in principle, everything is very simple. It is necessary to measure and then cut off a piece of threaded hairpin under the diameter of the hole in the blank and choose the right nuts with washers.

Wrap the nut for one end of the hairpin, then put on the puck and a piece of the blank. After that we put on the puck again and wind up the nut. Now you can start extracting bearings.

We insert one end of the hairpin into the hole in the bearing, twist the second nut and fix the part of the gearbox in the locksmith. Raise the steel blank up the hairpin and drop it sharply down. Several such movements, and the bearing in your hands.

You can watch in detail about this simple method in the video on our website.