The instruction on repair of angle grinders by own hands

Angle grinders( USM), popularly known as Bulgarians, are a popular and reliable tool. But everything once breaks. It is not difficult to repair a Bulgarian with your own hands, if you have an instruction telling you step by step how to perform the repair of ushm. Below you will find answers to any questions about repairing the gearbox, rotor, stator, carbon brushes of angle grinders.

Angle grinders are very popular among home craftsmen. The ability to change the working bodies allows you to produce cutting, grinding, polishing operations.

The presence of a soft starter makes the operation of the tool safe and convenient. Repair of the angle grinder is not complicated and can be performed independently. For those who decide to repair the ushm on their own, you will need a diagram of an angle grinder of the required type, a tool, lubricants and this manual.

Any repair of the Bulgarian with his own hands begins with a study of the arising malfunctions. The device of the Bulgarian is quite simple. The rotating rotor, through a helical gear, transfers the torque to the shaft( spindle) of the working member. The required tool is installed on the spindle, whether it is a cutting stone, grinding wheel or polishing wheel, and the required process operation is performed.

Speaking of the shape of the tooth. On the low-power Bulgarians, spur gears are installed. Helical gears are used in Bulgarian with a power of more than 1000 watts.

Angle grinders, like any tool, break down over time. The causes of failures Bulgarks can be different. They appear not only from improper operation of the tool, but also untimely replacement of carbon brushes, lubricating fluids.

In spite of the model of the angle grinder, all the faults appear at the same sites. Malfunctions of Bulgarians are conventionally divided into mechanical and electrical. For novice repairmen, faults are divided into simple and complex.

Mechanical Faults

The Bulgarian is an angle grinder designed for cutting, grinding, polishing. The Bulgarian is exposed to heavy loads in the process of work, working in a dusty environment.

Excessive loads when using the grinder in the "Cutting" mode cause increased wear not only of the bearing, but also of the teeth of the gears of the reducer.

Main malfunction of the Bulgarian on the mechanical part, wear or destruction of the plain bearing on the shaft of the large helical gear of the reducer.

It is not difficult to solve a Bulgarian grinder's problems if you have a diagram, description and recommendations for repair work at hand.

Repair of plain bearings

The weak point of any angle grinder is the bearings. And although there are only a few of them in the design, only three, they often lead to mechanical breakdowns. The bearings have a negative impact:

• high rotation speed;
• work in limit modes;
• insufficient amount of lubricant;
• ingress of dust or dirt;
• untimely replacement or destruction of carbon brushes.

The design of any grinder provides for quick and non-complex replacement of any bearing.

The malfunction of the grinder associated with the wear or destruction of the plain bearing on the gear shaft is characterized by the appearance of an unpleasant foreign sound.

The failure of the plain bearing is detected by checking the play of the operating tool shaft. It is determined by rocking in different directions of the shaft during installation of the working tool.

When installing the tool again, check the shaft play, shaking its end in different directions. Loft must be absent or minimal.

The appearance of a backlash indicates the need to replace the slide bearing.

Bearing repair consists of removing it from the body and removing it from the gearbox shaft.

It is better to remove the bearing from the shaft with a puller. The inner collar of the collapsed bearing is best obtained with a tap of the desired diameter, previously screwed into the cage.

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

Keys or stripes of metal are inserted into the vice, the bearings are placed on the keys and with the help of soft metal and a hammer head weighing not less than 400 g are knocked out from the shaft axis.

Repair of reducer for bulgaria

The degree of wear of the pinion gear of a Bulgarian reducer is checked for a contact patch. Preliminary the gearbox is completely cleaned of the old grease. A special blue is applied to the small gear of the reducer, the gearbox is cranked. Next, you need to remove the driven large helical gear and look through the magnifying glass on the contact patch. It should occupy a total of at least 50% of the tooth surface.

Otherwise, the gears must be replaced or the tooth profile corrected. Correction of the profile of the tooth 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 damaged gears change entirely, and in pairs.

How to correctly disassemble a reducer for a Bulgarian

When repairing a reducer for any Bulgarian, the most difficult task is to remove the gears and press out the support bearing.

Dismantling of the gear unit begins with removing the cover of the gearbox pos.1 and detaching the stator housing and releasing the rotor pos.2.Release the rotor clamped in a vice and unscrew the fastening nut 3 of the driving small gear.

The spindle bearing is pressed into the gearbox cover. In order to reach the bearing, in some Bulgarians it is necessary to remove the retaining ring that secures the bearing and remove the bearing.

The destroyed bearing pos.1 in the gearbox housing pos.2 is easiest to get by using a screwdriver.

In other models, the gear in the spindle locks the locking ring.

The driven large gear on the spindle is attached in several ways:

1. The gear is pressed onto the spindle.
2. Gear is attached with a key.

The driving small gear is either wound on the shaft on the left-hand thread( in some Sparky models, the thread is right), or fixed by a keyed connection and clamped with a nut.

How to remove the gears of a reducer

In Bulgarians up to 1000 W, spur gears are used, and helical gears are used in angle grinders.

Gears are attached in different Bulgarian differently. The drive gear is attached to the rotor shaft by a keyed connection or installed on the thread. The driven gear is attached to the spindle shaft by a fit fit or by a keyed connection. Details on how to remove gears and bearings from the shaft.

Repair gears is to replace them, and only in pairs.

Continuous and trouble-free operation of the gearbox depends on the availability of sufficient lubricant and its timely replacement.

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Repair of the spindle lock button

The fixing button for the spindle is designed for quick removal of the working tool. The button breaks when you press it while the disk is rotating. Repair of the Bulgarian is to replace the button completely.

The button should be pressed only when the grinder is fully stopped.

Electric faults of Bulgarian

The electrical circuit of the main part of Bulgarians is almost identical. The rotor transmits the rotational moment through the reduction gear to the working tool. The rotor rotates in the stator field. Control circuits consist of a button that regulates the speed and performs a smooth start of the tool, carbon brushes that ensure the transfer of alternating voltage to the collector sipes. Power is supplied to the instrument through the connecting cable.

The main electrical malfunctions of the electric grinder are:

• breakage of the supply cable at the entrance to the tool;
• destruction or wear of carbon brushes;
• outage of the power button;
• an open or shorted stator;
• an open or short circuit of the rotor;
• delamination or production of the collector sipes.

The electrical defect of the Bulgarian is best determined by a tester or other device. Suitable for these purposes and homemade device, called in the people "arc" .

The scheme of the Bulgarian is simple enough and does not require special knowledge. You just have to be careful and safety when doing repairs and know electrical engineering in the middle school.

Finding an open in the power cable

One of the common failures of the Bulgarian is the inability to turn on the instrument or spontaneously stop during operation. The cause of this type of failure is the breakdown of the power cable, pos. 27 at the entrance. Elimination of the fault by replacing the cable or throwing out the failed part. The fault is easily found by means of a tester.

If there is no tester on hand, but there is a screwdriver with a neon indicator light, the fault can be found by alternately connecting the power wires to the phase.

The failure of the carbon brushes

Reliable operation of any power tool depends to a large extent on the integrity and proper operation of the carbon brushes. The qualitative fit of carbon brushes, their proper location relative to the collector sipes, affects the efficiency of the rotor collector.

Remember! The length of the carbon electrobrush can not be less than 8 mm.

Timely replacement of carbon brushes avoids most of the malfunctions.

The degree of wear of carbon brushes is characterized by the types of arcing in the place of the collector. Sparking should be uniform throughout the contact spot of the carbon brush and lamellas and not exceed a length of more than 8 mm. Circular sparking indicates the appearance of a malfunction in the rotor circuits.

In Bulgarians it is recommended to use carbon brushes only by the tool manufacturers. Homemade carbon brushes can be installed, but only for a short period and immediately replaced at the first opportunity.

Repairing the power button and the speed controller

The faults of the power button are most often manifested in a difficult and unreliable switch-on of the tool during start-up. Such a malfunction appears spontaneously and disappears.

It is inadmissible to operate the Bulgarian with a malfunctioning power button. This fault leads to jamming of cutting discs during operation and their destruction with unpredictable consequences.

The fault is removed by completely replacing the button with a new one.

In modern models of Bulgarians, a soft starter with a speed regulator is integrated. Repair it is not subject to, but will require a complete replacement. No, advanced left-handed masters, of course, can repair such a knot.

Repair of stator

The stator's failure is indicated by spontaneous unwinding of the machine shaft, the Bulgarian starts to gain maximum revolutions. This malfunction indicates the occurrence of an inter-turn fault in the stator winding.

Some faults can only be eliminated by specialists. The continuation of the uninterrupted operation of the stator can only be done by timely cleaning, lubrication and replacement of carbon brushes and bearings.

Typically, the stator breaks down quite infrequently. This leads to frequent overheating of the instrument during operation. The malfunction is manifested by the strong heating of the housing of the Bulgarian and the appearance of the smell of burnt insulation.

The stator can have both an open and a short circuit. Without parsing the stator, these faults can easily be found using the IR-32.

Faults are eliminated by replacing the stator. For those who like to craft themselves, we can recommend rewinding the failed stator with our own hands. Nothing complicated in this.

The stator is removed easily, but in different models of the USM in its own way.

How to remove stator:

• remove the reducer of the Bulgarian;
• remove the rotor, having removed the lash plate;
• remove plastic stator protection;
• unscrew the stator fixing screws in the housing;
• remove the handle cover and disconnect the power wires to the stator;
• extract the stator by tapping the body with a wooden hammer or bar.

Repair of the rotor of the USM

The failure of the rotor in the bulgarian is caused by improper operation of the tool, frequent overheating, untimely replacement of carbon brushes, hitting the collector of abrasive particles and dust on the lamellas.

At first, the length of the spark on the collector increases, then the smell of burning and, at the last stage, smoke. The operation of the faulty gearbox is accompanied by a thud and hum.

The destruction of even a pair of teeth results in malfunctioning of the tool.

To prolong the rotor life it is possible to prevent dust from getting inside the instrument, to prevent overheating of the tool, timely change of carbon brushes and lubricants, using only those working tools and the diameter recommended by the manufacturer of power tools.

The rotor is a complex unit that requires repair in service centers. But fans can make repairs by themselves, they can repair the rotor independently.

Repair of the collector and rotor blades

The dismantling of the rotor is not particularly difficult.

Procedure for removing the rotor from the angle grinder:

• remove the grinder handle cover;
• to free and remove carbon brushes;
• unscrew the screws securing the gearbox housing to the main body;
• remove the gear housing;
• remove the rotor.

The removed rotor should be carefully examined. If large grooves are rubbed on the lamellas, they must be removed by punching the collector in the lathe.

With minor grooves, the defect is eliminated by grinding. The rotor is clamped into the holder of the electric drill and the work is removed with the aid of the nail file and grinding paper. The process is simple.

The drill is clamped in a vice or securely attached to a flat surface. In the drill chuck inserts the end of the rotor, on which the lamella is placed, and securely clamped. The bearings are removed from the rotor.

The second end of the rotor must be supported with a set of wooden bars. The drill is turned on and a small number of revolutions are set. At the first stage, use a grinding paper of coarse granularity No. 40..80, at the final stage, a smaller No. 120..200.

After grinding, it is necessary to cut the grooves between the lamellas. This is best done with a hacksaw blade, specially sharpened. After milling the grooves of the collector, the edges of the lamellas must be stripped from the burrs, using a diamond nail file. Properly polished lamellas should not have burrs.

In addition to general malfunctions in models of angle grinders from different manufacturers, there are also specific breakages, characteristic only for the tool of this manufacturer. But about this in another article.

Good luck to you!

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