How To Properly Repair A Bosch Grinder With Your Own Hands

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

• Design features of the Bosch angle grinder
• Tool required for repair
• Dismantling the Bosch grinder with your own hands
• How to remove the driven gear
• How to remove the drive gear of a Bosch grinder
• How to remove bearings from a Bosch grinder rotor
• Possible electrical faults
• Simple malfunctions of the electrical part of the Bosch grinder
• Checking the electric motor
• How to identify a rotor malfunction
• Stator repair

• Stator overheating and rotor short circuit

  

• Malfunction of speed regulators
• Mechanical damage
• Assembling the grinder
• What kind of lubricant to use for the Bosch grinder
• Rotor assembly
• Gearbox assembly
• Bosch grinder repair video
• Bosch grinder assembly
• How to replace bearings on a Bosch grinder
• Repairing Bosch GWS 20 230

Angle grinders (angle grinders, grinders) under the German brand Bosch are of high quality, reliability and durability. The main competitive advantage of Bosch angle grinders lies in the wide use of innovative technologies in the manufacture of products.

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

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

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

The Bosch grinder diagram will help you carry out the repair yourself.

Bosch grinders are conventionally divided into low-power ones up to 1000 W, and powerful ones over 1000 W are marked GWS 7-125, GWS 20-230 or others.

Decrypted

The first digit 20 or more indicates the power of the instrument is more than 1000 watts. The second number 230 certifies that this is the maximum diameter of the cut-off wheel.

The first figure up to 20 indicates the power of the tool up to 1000 W, and the second indicates the maximum diameter of the cutting wheel up to 125 mm.

Design features of the Bosch angle grinder

The design feature of the Bosch grinder is presented in the application in the gearbox as a support bearing of the driven helical gear of the needle bearing. In Bosch hammer drills, the driven gear is mounted on the spindle shaft by pressing.

In Bosch grinders of low power, in which spur gears are installed in the gearboxes, the installation of shims is provided. This design allows the contact of the gears to be restored to work, reducing the thickness of the gasket. Helical gears wear significantly less spur gears at high tool speeds.

The working environment of grinders is most often a dusty space. Dust is the main danger leading to failure of power tools, falling in love and grinders.

Tool required for repair

To repair a Bosch grinder, you cannot do without a tool. Let's make a reservation right away, if you have a screwdriver, then this will significantly speed up the process of disassembling and assembling the tool.

But you can get by with a set of screwdrivers, preferably with a ratchet. You cannot do without an open-end wrench with which you will unscrew the nut that secures the leading helical gear.

It is better to have a special puller for removing the bearings.

Diagnostics of the electrical part can be carried out using a tester or a short-circuit test device.

It is especially useful in that it allows you to determine the malfunction of the rotor or stator without removing the assembly.

The Bosch grinder diagram will help you carry out the repair yourself, and this instruction will help you cope with any problem with dignity.

Dismantling the Bosch grinder with your own hands

For the owner of a power tool, knowledge of its device and the ability to disassemble is a must.

Knowing the procedure for disassembling the grinder allows you to independently perform such work as changing lubricants, changing bearings and carbon brushes.

To disconnect the gearbox housing poz.821 from the stator housing poz.888, it is necessary to disassemble (remove) the housing of the grinder handle pos.24.

This operation must be performed in order to get the carbon brushes pos. 810 holding the rotor collector.

At the second stage, unscrew the 4 (four) screws pos. 61 that secure the gearbox and stator housings.

Having pulled out the rotor together with the gearbox, proceed to disassemble the gearbox.

Repair of the Bosch grinder begins with disassembling the gearbox pos. 821. Disassembly of the gearbox begins with unscrewing 4 (four) screws, pos. 60. As a rule, the screws are screwed into the sealant at the factory. You will have to make some effort.

Let's note right away! Low-power Bosch grinders use spur gears in the gearbox. For grinders with a power of over 1000 W, helical gears are used in gearboxes.

How to remove the driven gear

After removing the gear cover, you can get the helical gear assembly, pos. 26.

To remove the gear, you need to use a press or puller. But using a puller is difficult because it requires the use of special thin jaws.

Before removing the helical gear, check the backlash of the gear connection, the integrity of the teeth, the contact patch.

On the spindle shaft pos. 26, the bearing pos. 50 is pressed. If the bearing has a large play, makes noises when rotating, the lubricant has dried, it is preferable to replace it.

To remove the bearing, it is necessary to remove the gear, circlip and dismantle the bearing. If, when removing the rotor shaft assembly, the bearing remains in the gear housing, the bearing is removed using a hammer and a soft tip.

How to remove the drive gear of a Bosch grinder

The drive gear pos. 27 is removed from the rotor shaft in the following sequence:

• clamp the rotor by hand and, using an open-end wrench, unscrew the nut pos. 45 counterclockwise.;
• remove the washer pos. 59.;
• pull out the leading helical gear pos. 27.

Visually check the integrity of the gear teeth, contact patch.

If the gears are badly worn (licked), there are chipped teeth, then they must be replaced. Moreover, the replacement of gears is always done in pairs.

In low-power Bosch grinders, a needle bearing is used as a support bearing in the gearbox.

Do-it-yourself bosch grinder repair follow the instructions provided strictly. If you need to remove the needle bearing from the housing, you can’t do without some quick wits. Its dismantling is carried out only upon destruction.

To get a destroyed bearing race, you can use a proven method.

A tap is selected with a diameter slightly larger than the inner diameter of the destroyed needle bearing holder. The tap is fixed in the chuck of the screwdriver and carefully screwed into the holder at low speeds. When the tap reaches the bottom of the gear case, it will begin to lift the clip.

In addition to the needle bearing of the spindle shaft, Bosch grinders use two more bearings mounted on the rotor shaft.

How to remove bearings from a Bosch grinder rotor

It is recommended to use pullers to dismantle the bearings from the rotor pos. 803 of the Bosch grinder.

The bearing pos. 15 near the collector can be easily removed, but to remove the bearing pos. 14 from the impeller side it is complicated by the fact that a number of preparatory operations must be performed.

Bearing pos. 15 is closed with a soft rubber seat. A similar rubber protection pos. 33 also covers the bearing pos. 14.

To dismantle the bearing, pos. 14, unscrew the nut, pos. 45, remove the spur gear, pos. 17, and the plastic protection, pos. 33. Using a puller, you can easily dismantle the bearing from the rotor shaft.

And if there is no puller? A vice, two metal strips and a hammer with a soft metal guide will come to the rescue.

Dismantling grinder Bosch

Possible electrical faults

Malfunctions of the electrical part of the Bosch grinder can be conditionally divided into simple and complex.

Simple malfunctions of the electrical part of the Bosch grinder

If you turned on the grinder, and it refuses to work, start looking for a malfunction with a break in the power supply wire. Most often, a wire break occurs at the point of entry into a grinder or a plug. Do not twist, this will short-circuit the instrument.

To determine such a malfunction, you must open the grinder handle covers. In Bosch grinders up to 1000 W, the cover is fastened with one screw at the end. For Bosch grinders over 1000 W, the handle cover is fastened with several screws.

Using a tester, ring the power circuit from the input plug pos. 5 to the switch. With a complete circuit, proceed to test the operation of the switch. Bosch grinders use simple switches controlled by the on-lever.

But the electrical contacts of the switch burn out and cause the grinder to fail. It is impractical to restore the contacts of the plastic switch, it is necessary to change to a new one.

If the switch is intact, use a tester to check the presence of a circuit from each pin of the plug to each carbon brush. With whole circuits, the grinder should turn on. If it does not rotate, then there is a mechanical problem. Gear jamming or bearing destruction is possible.

Checking the electric motor

If your Bosch grinder is gaining momentum regardless of you, it starts to get very hot, sparkle, you need to pay attention to the integrity of the rotor and stator windings.

An involuntary set of revolutions of the LBM indicates a malfunction of the stator windings. The integrity of the windings is checked with a tester, and the short circuit between the turns is checked with a special device.

How to identify a rotor malfunction

Rotor repair is a complex technological process available to straight-handed craftsmen.

A rotor malfunction is indicated by a drop in engine speed, the appearance of a long sparkling trace at one of the brushes. This is the first sign of a short circuit in the turns of the armature winding.

The rotor should preferably be repaired in a specialized workshop. And you can rewind yourself if you decide to repair the Bosch grinder yourself.

Dark color of the rotor winding and burnt collector lamellas indicate a short circuit in the rotor circuits. The malfunction is eliminated only by replacing it with a new rotor.

Stator repair

Repair of a bosch angle grinder also includes restoration of the stator. The main symptom of a stator failure is a spontaneous increase in the speed of a working grinder, which cannot be reduced by adjustments. A burnt-out stator winding changes color and becomes darker. The stator core also darkens from high temperatures.

It is easier to rewind the stator, although certain rules and sequence must be followed here.

If you removed the stator housing cover, carefully inspect the condition of the carbon brushes and rotor manifold fins.

The length of the carbon brushes should not be less than 8 mm. By the way, Bosch grinders use carbon brushes with a “shot”, a device that stops the grinder's operation at the minimum length of the carbon brush.

The collector lamellae must be free of carbon deposits or wear. Carbon deposits are easily removed with cotton wool soaked in alcohol.

Stator overheating and rotor short circuit

Malfunction of speed regulators

In the Bosch series grinders, especially of low power, speed controllers are installed. Access to the speed controller is carried out by opening the handle of the stator housing, which is held by one end screw.

The speed range of the regulator can be set with a potentiometer hidden in the knob panel.

Removing a faulty regulator is easy enough, since it is attached only to the rail.

Repairing the LDM speed regulator is a complex process, the implementation of which requires not only special knowledge, but tools and equipment.

If the speed regulator is out of order, but there is no new one, then disconnect the supply wires and install a jumper.

A jumper is shown in red, which is installed when the speed regulator fails.

Mechanical damage

Bosch angle grinder is designed for cutting, grinding and polishing work. The operation of the tool in dust under heavy loads has a particularly detrimental effect on the durability of the gearbox, namely its gears.

In addition to wear and tear of the gear teeth, mechanical failures include the destruction of bearings and housing. Repair of a Bosch grinder in terms of replacing failed bearings, restoring the housing is not difficult to perform if there is a desire and need.

Assembling the grinder

The assembly of the grinder begins with an examination of all parts, assemblies, bearings, gears.

Prepare the work area in advance with correct and good lighting, place tools, lubricants, napkins.

What kind of lubricant to use for the Bosch grinder

Bosch ear repair will not be of good quality if you do not change the lubricant during its execution. For high-quality lubrication of the Bosch grinder units, it is recommended to use those lubricants that the tool manufacturer offers. But their high price makes them look for another way out, and there is one.

Domestic manufacturers of lubricants have developed special lubricants for gearboxes and grinders.

In terms of quality, they are in no way inferior to foreign lubricants, and are much cheaper. The only drawback is that our greases require more frequent changes.

Or you can use a hand-made lubricant.

Rotor assembly

The assembly of the rotor consists in pressing the bearings onto it, installing the impeller. The lubricated bearings are pressed onto the shaft using a wooden adapter. The bearing near the manifold is covered with a rubber protection. This is a general assembly algorithm for the rotor shaft.

Certain models of Bosch grinders have their own characteristics.

Gearbox assembly

The assembly of the gearbox begins with the installation of the rotor shaft in its housing. When the shaft is inserted into the housing, the drive gear, washer, and lock nut are slid over the shaft. The gearbox housing with the inserted shaft must be placed in the stator housing.

When you insert the manifold bearing into the seat, press the gear housing against the stator housing. Check the ease of rotation of the rotor in the bearings.

A spindle assembly with a fitted bearing and a gear is mounted in the gearbox housing cover.

It remains to insert the cover into place and check the quality of rotation of the spindle shaft. If the shaft rotates easily by hand, it is fashionable to tighten the screws securing the rotor housing cover. The screws are pre-lubricated with sealant.

This is the general algorithm for assembling the gearbox. For some models, the repair of the Bosch grinder gearbox is slightly different.

Conclusions:

• Knowing the general scheme of Bosch grinders, you can safely take on the disassembly of the lubrication tool;
• The ability to repair a Bosch grinder with your own hands will allow you to extend the life of the tool, independently replace the lubricant, carbon brushes;
• Observing the mode of operation and technological maintenance of the tool, you will extend its trouble-free operation for many years.

Good luck in job!

Bosch grinder repair video

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