How To Properly Repair A Grinder With Your Own Hands

2023 Author: Philip Bishop | [email protected]. Last modified: 2023-08-25 07:54

• Mechanical malfunction of angle grinder
• Repair of plain bearings
• Grinder gearbox repair
• How to properly disassemble the grinder gearbox
• How to remove the gears of the reducer
• Repair of the spindle lock button
• Electrical malfunctions grinder
• Finding a Broken Power Wire
• Malfunctioning carbon brushes
• Repair of the power button and the speed controller
• Stator repair
• Repair of the rotor angle grinder
• Grinder repair video
• Do-it-yourself grinder repair (start button)
• How to replace bearings on a Bosch grinder

Angle grinders (angle grinders), popularly called grinders, are a popular and reliable tool. But everything breaks down sometime. It is not difficult to repair a grinder with your own hands, if you have an instruction that tells you the step-by-step procedure for repairing a grinder. Below you will find answers to any questions about the repair of a gearbox, rotor, stator, carbon brushes of angle grinders.

Angle grinders are very popular among home craftsmen. The possibility of interchangeability of the working bodies allows cutting, grinding, polishing operations.

The presence of a soft starter makes the operation of the tool safe and convenient. Repairing an angle grinder is simple and can be done independently. For those who decide to repair the angle grinder on their own, you will need a diagram of an angle grinder of the required type, tools, lubricants and this instruction.

Any do-it-yourself grinder repair begins with an investigation of the malfunctions that arise. The grinder's device is quite simple. The rotating rotor transmits torque to the shaft (spindle) of the working body through a helical gear. The required working tool is installed on the spindle, whether it is a cut-off stone, a grinding or polishing wheel, and the required technological operation is performed.

By the way, about the shape of the tooth. Spur gears are installed on low-power grinders. Helical gears are used in grinders with a power of over 1000 watts.

Angle grinders, like any tool, break down over time. The causes of malfunctions of the grinder may be different. They appear not only from improper use of the tool, but also from untimely replacement of carbon brushes and lubricating fluids.

Regardless of the model of the angle grinder, faults all appear in the same units. Malfunctions of grinders are conventionally divided into mechanical and electrical. For novice repairmen, faults are divided into simple and complex.

Mechanical malfunction of angle grinder

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

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

The main malfunction of the grinder in the mechanical part, wear or destruction of the sleeve bearing on the shaft of the large helical gear of the gearbox.

It is not difficult to troubleshoot a grinder if you have its diagram, description and recommendations for performing repair work at hand.

Repair of plain bearings

The weak point of any angle grinder is the bearings. And although there are few of them in the design, there are only three, they are the ones that most often lead to mechanical failures. Bearings are adversely affected by:

• high rotation speed;
• work at limiting conditions;
• insufficient lubrication;
• dust or dirt;
• untimely replacement or destruction of carbon brushes.

The design of any grinder provides for a quick and easy replacement of any bearing.

Malfunctions of the grinder 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 sleeve bearing is detected by checking the backlash of the working tool installation shaft. It is determined by swinging the shaft in different directions when installing the working tool.

At the next installation of the working tool, check the shaft play by swinging its end in different directions. Backlash should be absent or minimal.

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

Bearing repair consists in removing it from the housing and removing it from the gearbox shaft.

It is better to remove the bearing from the shaft using a puller. It is best to get the inner race of a damaged bearing using a tap of the required diameter, previously screwed into the race.

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

Keys or metal strips are inserted into the vice, the bearings are placed on the keys and, using a soft metal adapter and a hammer weighing at least 400 g, are driven out of the shaft axis.

Grinder gearbox repair

The degree of wear of the gears of the grinder reducer is checked for the contact patch. The gearbox is pre-cleaned from old grease. A special blue is applied to the small gear of the reducer, the reducer rotates. Next, you need to remove the driven large helical gear and look through a magnifying glass at the contact patch. It should cover a total of at least 50% of the tooth surface.

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

But such a malfunction can only be eliminated by an experienced craftsman. Most often, licked, cut or destroyed gears are changed entirely, and in pairs.

How to properly disassemble the grinder gearbox

When repairing a gearbox of any grinder, the most difficult task is to remove the gears and press out the support bearing.

Dismantling the gearbox begins with removing the gearbox cover, pos. 1, and disconnecting the stator housing and freeing the rotor, pos. 2. The released rotor is clamped in a vice and the nut of fastening item 3 of the leading small gear is unscrewed.

The spindle bearing is pressed into the gearbox cover. To get the bearing, in some grinders, you need to remove the circlip securing the support bearing and remove the bearing.

The destroyed bearing pos. 1 in the gear housing pos. 2 is easiest to reach by prying it with a screwdriver.

In other models, the gear in the spindle is fixed by a circlip.

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

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

The small drive gear is either screwed on the shaft along the left-hand thread (in some Sparky models, the thread is right-hand), or fixed with a keyway and clamped with a nut.

How to remove the gears of the reducer

Spur gears are used in grinders up to 1000 W, and helical gears are used in angle grinders.

The gears are attached in different grinders in different ways. The pinion is keyed or threaded onto the rotor shaft. The driven gear is mounted on the spindle shaft with an interference fit or keyed connection. Details on how to remove the gears and bearing from the shaft.

Repair of gears consists in replacing them, and only in pairs.

Long-term and trouble-free operation of the gearbox depends on the availability of a sufficient amount of lubricant and its timely replacement.

Repair of the spindle lock button

The spindle lock button is designed for quick removal of the working tool. The button breaks when pressed while the disk rotates. Repair of the grinder consists in a complete replacement of the button.

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

Electrical malfunctions grinder

The electrical circuit of the main part of the grinders is almost the same. The rotor transmits the torque through the gearbox to the working tool. The rotor rotates in the stator field. The control circuits consist of a button that regulates the speed and performs a smooth start of the tool, carbon brushes, which ensure the transfer of alternating voltage to the collector lamellas. Power is supplied to the instrument via the connecting cable.

The main electrical malfunctions of the grinder include:

• breakage of the supply cable at the entrance to the tool;
• destruction or wear of carbon brushes;
• failure of the power button;
• open or short circuit of the stator;
• open or short circuit of the rotor;
• delamination or development of collector lamellas.

Electrical malfunctions of the grinder are best determined with a tester or other device. A home-made device, popularly called "arkashka", is also suitable for these.

The grinder's scheme is quite simple and does not require special knowledge. You just need to be careful and safe when performing repair work and know electrical engineering in the amount of high school.

Finding a Broken Power Wire

One of the common breakdowns of a grinder is the inability to turn on the tool or spontaneous stop during operation. The cause of this kind of malfunction is the breakage of the power cable pos. 27 at the entry point. The malfunction is eliminated by replacing the cable or throwing out the failed section. The fault is easily found with a tester.

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

Malfunctioning carbon brushes

The reliable performance of any power tool is highly dependent on the integrity and proper operation of the carbon brushes. The good fit of the carbon brushes, their correct location relative to the collector lamellas affects the performance of the rotor collector.

Remember! The length of the carbon electric brush must not be less than 8 mm.

Timely replacement of carbon brushes avoids most of the malfunctions.

The wear rate of carbon brushes is characterized by the types of sparking at the collector site. Sparking should be uniform over the entire contact patch of the carbon brush and lamellas and should not exceed a length of more than 8 mm. Circular sparking indicates a malfunction in the rotor circuits.

It is recommended to use carbon brushes in grinders only from tool manufacturers. Homemade carbon brushes can be installed, but only for a short period, and replaced as soon as possible.

Repair of the power button and the speed controller

Power button malfunctions most often manifest themselves in a difficult and unreliable turning on of the tool at start-up. Such a malfunction spontaneously appears and disappears.

It is unacceptable to work with a grinder with a faulty power button. This malfunction leads to jamming of cutting discs during operation and their destruction with unpredictable consequences.

The malfunction is eliminated by completely replacing the button with a new one.

In modern models of grinders, a soft starter with a speed controller is built in. It cannot be repaired, but will require a complete replacement. No, advanced left-handed craftsmen, of course, can fix such a node.

Stator repair

The failure of the stator is indicated by the spontaneous promotion of the machine shaft, the grinder begins to gain maximum speed. Such a malfunction indicates the appearance of an interturn short circuit in the stator winding.

Some malfunctions can only be rectified by specialists. Prolongation of uninterrupted operation of the stator is possible only by timely cleaning, lubrication and replacement of carbon brushes and bearings.

Usually the stator fails quite rarely. This is caused by frequent overheating of the tool during operation. The malfunction is manifested by strong heating of the grinder body and the smell of burnt insulation.

In the stator there can be both an open circuit and a short circuit. Without disassembling the stator, these faults can be easily found using the IK-32 device.

Faults are eliminated by replacing the stator. For those who like to do it yourself, we can recommend rewinding a failed stator with your own hands. There is nothing difficult about this.

The stator can be removed easily, but in different LBM models in its own way.

Stator removal procedure:

• remove the grinder gearbox;
• remove the rotor, after removing the mounting bar;
• remove the plastic protection of the stator;
• unscrew the screws securing the stator in the housing;
• remove the handle cover and disconnect the power wires to the stator;
• remove the stator by tapping on the housing with a wooden hammer or block.

Repair of the rotor angle grinder

Failure of the rotor in the grinder is caused by improper use of the tool, frequent overheating, untimely replacement of carbon brushes, contact with the collector lamellas of abrasive particles and dust.

First, the length of the spark on the manifold increases, then a burning smell appears and, at the last stage, smoke. The operation of a faulty gearbox is accompanied by a knock and hum.

The destruction of even a pair of teeth leads to incorrect operation of the tool.

The life of the rotor can be extended by preventing dust from entering the tool, preventing the tool from overheating, changing carbon brushes and lubricants in a timely manner, using only those working tools and of the diameter recommended by the manufacturer of the power tool.

The rotor is a complex unit that requires repair at service centers. But DIY lovers can repair the rotor on their own.

Repair of the collector and rotor lamellas

Removing the rotor is easy.

To remove the rotor from the angle grinder:

• remove the cover of the grinder handle;
• release and remove the carbon brushes;
• unscrew the screws securing the gearbox housing to the main housing;
• remove the gearbox housing;
• remove the rotor.

The removed rotor must be carefully inspected. If large grooves are rubbed on the lamellas, they should be removed by turning the manifold in a lathe.

With minor grooves, the defect is eliminated by grinding. The rotor is clamped into the chuck of an electric drill, and the wear is removed using a needle file and sanding paper. The process is simple.

The drill is clamped in a vise or securely mounted on a flat surface. The end of the rotor, on which the lamella is located, is inserted into the drill chuck and securely clamped. The bearings were previously removed from the rotor.

The other end of the rotor must be supported with a set of wooden blocks. The drill turns on and a small number of revolutions are set. At the first stage, use coarse sanding paper No. 40..80, at the final stage, a finer one No. 120..200.

After grinding, the grooves between the lamellas must be milled. This is best done with a specially sharpened hacksaw blade. After milling the grooves of the collector, the edges of the lamellas must be deburred using a diamond file. Correctly sanded lamellas should be free of burrs.

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

I wish you success!

Grinder repair video

Do-it-yourself grinder repair (start button)

Video:

How to replace bearings on a Bosch grinder