How to disassemble the gearbox of the Bosch angle grinder

Design features of the Bosch angle grinder

Design feature of the Bosch angle grinder is presented in the application of the gearbox as a bearing driven spiral bevel gear needle bearing.In Bosch angle grinders, the idler pinion on the spindle shaft is press-fitted.

In Bosch small power angle grinders, in which spur gears are placed in the gearboxes, the installation of adjustment gaskets is provided. This design allows the gears to be restored to serviceable contact by reducing the thickness of the gasket. Helical gears tend to wear much less than spur gears at higher tool speeds.

disassemble, gearbox, bosch, angle

The working environment of angle grinders is most often a dusty space. Dust is a major hazard, leading to failure of power tools, crank and angle grinder.

Two angle grinders Bosch. Green and blue

Good day dear readers. Autumn brings us warm days. After a nice walk along the evening promenade decided to write about two German angle grinder Bosch (strange wish, but what can I do).

By the way pictures of our beautiful embankment, specifically Lovebirds Bridge.

Two angle grinders came into our service. One of them is household green, the other one is professional blue. Bosch PWS 850-125 и Bosch GWS 750-125.

How to disassemble the angle grinder

The process of disassembling the angle grinder is simple and does not require any special knowledge. But it does require care and caution. Dismantling of any tool can be justified not only in terms of repairing component parts, but also in terms of regular cleaning from dust and dirt. Therefore, it is necessary to know how to disassemble the angle grinder, if you own such a tool and are interested in your tool to work properly for a long period of time.

Today you can buy a variety of angle grinder, which differ not only in appearance and size, but also in quality. Despite the abundance of models from different manufacturers with different build quality, they all tend to have the same principle of assembly (layout of parts).

So today in this article we will try to figure out how to disassemble the angle grinder of one manufacturer and look inside the housing to get acquainted with the structure of the angle grinder. Figuring this out and understanding the structure of this angle grinder you can then easily disassemble and reassemble any model you have.

In principle you do not need many tools to disassemble the angle grinder, you just need a ratchet screwdriver or an ordinary screwdriver and be a little collected and attentive. Relax and take your time to carefully disassemble the motor and remember the location of all the parts inside the housing for proper reassembly.

Figure-1. Appearance and arrangement in the housing of the SJS angle grinder

The basic modules that make up the assembly of all types of lathes

Handy body made of impact resistant plastic.

Sufficiently powerful electric motor consisting of rotor and stator.

Robust gearbox which can rotate the spindle axis of the rotor through 90 degrees.

Soft-start button (not all models are equipped).

SJS (Super-Joint-System).

angle grinder gear change | how to change angle grinder gear | angle grinder repair kasea hotahea

The system provides comfortable and smooth operation during work. Also avoids injury to the operator and tool breakage when the cutting wheel is jammed in hard material, reduces vibration to a minimum. True, not all angle grinders are equipped by manufacturers with such a device.

The safety guard allows the operator to work in safety.

Additional handle. This device allows you to hold the tool more comfortably while working. Several handle positions are available for fastening the handle, making the tool more convenient and versatile.

Repair Bosch Angle Grinder at Home. How to, |DIY|

And so, today I propose to consider disassembly angle grinder power of 700 watts, which I use only for grinding metal surfaces. During grinding, the angle grinder is heavily contaminated by small metal parts, dust and dirt accumulated inside the body of the angle grinder in the form of thick layers and pose a great threat to the performance of the tool.

Therefore, I periodically disassemble the angle grinder after the work and inspect the parts and regularly clean it from metal dust and dirt. This is a pretty monotonous process, but very necessary because the serviceability of the tool for me is extremely important. Next, I suggest to move from words to deeds and get acquainted with the disassembly process.

Replacing the gearbox bearing-flange on the Bosch GWS 20-230 angle grinder

The medium of grinders in most cases is a dusty place. Dust is the main danger, leading to wear of power tools, including angle grinder.

What to do the repair of angle grinder Bosch, without a tool can not do without. At a glance, if you have an electric screwdriver, it will greatly speed up the disassembly and assembly of the tool.

Alas it is possible to do and a set of screwdrivers, preferably with a ratchet mechanism. Do not do without the open-end wrench, which will unscrew the nut securing the helical drive pinion.

It is better to have a special puller for bearing disassembly.

Diagnostics of the electronic part of course with a tester or a device for determining the short circuit of the coils.

In particular, it is useful because it makes it possible to perform the fault of the rotor or stator without removing the unit.

Angle grinder Bosch scheme will help you perform repairs without assistance from others, and the real annotation will help to cope with any failure.

To the owner of a power tool to know how to assemble and disassemble it is an absolutely necessary task.

Knowing how to disassemble the angle grinder allows you to do such jobs as changing the lubricant, bearings and carbon brushes without the help of others.

To disconnect the gear housing pos.821 from the stator housing pos.888, you need to disassemble (remove) the handle housing angle grinder pos.24.

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This operation must be performed in order to remove the carbon brushes pos.810 that hold the rotor head.

In a second step unscrew the four (4) screws pos.61 holding the gearbox and stator housings.

After pulling out the rotor and gearbox, disassemble the gearbox.

Repair of angle grinder Bosch starts with disassembly of the gearbox pos.821. Disassembly of the gearbox begins by removing the four (4) screws pos.60. The screws are normally sealed at the factory. You’ll have to use some force.

At a glance, we should note! Bosch low-power drills use spur gears in the gearbox. In gearboxes of grinders with power over 1000 W are used helical gears.

By removing the gear cover it is possible to get the helical gear assembly pos.26.

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To remove the pinion you need to use the press or puller. But the introduction of the extractor is problematic, because it requires the introduction of special thin jaws.

Before you remove spur gears, check the free running of the gearing, the integrity of the teeth, the contact patch.

On the spindle shaft pos.26 The bearing pos.50. If the bearing has a large free movement, noises when turning, grease has dried up, it is better to replace it.

To remove the bearing, remove the pinion, the retaining ring and remove the bearing. If the bearing remains in the gearbox housing when disassembling the rotor shaft assembly, disassemble bearing with a hammer and a soft spacer.

Drive pinion pos.27 is removed from the rotor shaft in this order:

  • grip the rotor with your hand and with an open-ended wrench unscrew the nut pos.45.;
  • remove the washer pos.59.;
  • Remove the helical bevel pinion pos.27.

Visually check the integrity of the gear teeth, the contact surface of the pinion.

If the gears are very worn (licked), there are chipped teeth, they are replaced. The gear change is always done in pairs.

In Bosch lathes small power as a bearing in the gearbox is used needle roller bearing.

Make repairs at home angle grinder Bosch strictly according to the enclosed annotation. If you will need to remove the needle roller bearing from the body, without ingenuity is not enough. It can only be removed by destroying.

To extract the destroyed bearing rim, use the proven method.

Fit a tap with a diameter slightly greater than the inner diameter of the broken needle cage. The tap is fastened in the chuck of the electric screwdriver and screwed carefully at low speed into the cage. When the tap reaches the bottom of the gearbox housing, it begins to lift the rim.

Not counting the needle roller bearing on the spindle shaft, Bosch bolsters use two other bearings on the rotor shaft.

To remove the bearings from the rotor pos.803 of the Bosch angle grinder it is recommended to use pullers.

bearing pos.15 near the manifold is easy to remove, but to remove the bearing pos.14 not familiar with the impeller is complicated by the fact that you need to perform a number of preliminary operations.

Bearing pos.15 is covered by a soft rubber socket. A similar rubber guard pos.33 covers the bearing pos.14.

To remove the bearing pos.14 you have to unscrew the nut pos.45, remove the spur gear pos.17 and the plastic guard pos.33. With a puller it is possible to simply remove the bearing from the rotor shaft.

If there is no puller? A vice, two iron strips and a hammer with a soft metal drift will be helpful.

Faults in the electronic part of the angle grinder Bosch conditionally divided into ordinary and complex.

If you turned on the angle grinder and it refuses to work, start troubleshooting with a broken power wire. In most cases the wire breakage occurs at the entry point of the angle grinder or the plug. Do not twist, it will cause a short circuit in the tool.

To determine such a malfunction should open the cover handle angle grinder. In Bosch grinders up to 1000 watts, the cover is secured with one screw in the end. On Bosch battery powered power tools above 1000 W the handle cover is secured with several screws.

Using a tester, test the power circuits from the input plug pos.5 up to the switch. If the chain is intact, run to check the switch. Bosch power tools use conventional switches, which are controlled by the trigger lever.

But electronic contacts of the switch burn out and become a reason for the failure of the angle grinder. No need to reset plastic switch contacts, need to replace with a new one.

If the switch is intact, use a tester to check for a circuit from each prong of the plug to each carbon brush.If the circuits are intact, the angle grinder should turn on. If it will not turn, the problem is on the mechanical side. There may be jamming of gears or destruction of bearings.

If your Bosch angle grinder develops independently of you, starts to get very hot, sparks, you need to check the integrity of the rotor windings, stator.

Unintentional rotation of the angle grinder is indicative of a faulty stator winding. The integrity of the windings can be checked with a tester, and the short circuit between the coils can be checked with a special device.

Repair of rotor is not a simple manufacturing process and can be done by craftsmen with straight hands.

The rotor malfunction is indicated by the motor RPM drop, appearance of one of the brushes with a longish sparkling trace. This is 1st sign of a shorted armature winding turns.

It is advisable to have the rotor repaired in a special workshop. You can rewind without the help of others, if you decide to make repairs yourself an angle grinder Bosch in artisanal conditions.

Black rotor windings and burned manifold lamellae indicate a short in the rotor circuits. The malfunction can only be eliminated by exchanging for a new rotor.

Bosch angle grinder repair contains and stator rebuild. The main sign of stator failure is the spontaneous increase in the speed of the working angle grinder, which is unrealistic to reduce adjustments.Burned stator winding changes color, becomes darker. The stator core also darkens from the highest temperature.

The stator is easier to rewind, but certain rules and sequences must be observed.

If you have removed the stator case cover, take a good look at the carbon brushes and the rotor collector blades.

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Carbon brushes are at least 8 mm long. When, in Bosch angle grinders are used carbon brushes with a “shot”, a device that stops the angle grinder when the length of the carbon brush.

The manifold lamellae do not have to show any signs of sooting, as it is also called wear. The carbon deposits are easy to remove with absorbent cotton soaked in alcohol.

The Bosch brushcutters, especially the low power ones, have speed controllers. access to the speed regulator is gained by opening the handle of the stator housing, held in place by one end screw.

The speed range of the regulator can be adjusted with a potentiometer hidden in the handle panel.

Faulty regulator is quite easy to remove as it is only fastened to the guide rail.

Repair of the angle grinder RPM regulator is not an easy process, whose performance requires not only special knowledge, but also tools and equipment.

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

The reddish colour shows the jumper that is installed when the speed regulator is ready to go out of operation.

Angle grinder Bosch created for cutting, grinding, polishing works. Working with the tool in the dust at high loads in particular has a negative impact on the durability of the gearbox, but specifically its gears.

In addition to wear and breakage of gear teeth, mechanical problems include the destruction of bearings and housing. Repair angle grinder Bosch in terms of changing frayed bearings, restoration of the body is not difficult to perform, if the desire and need, of course.

Assembly of the angle grinder begin with the examination of all parts, components, bearings, gears.

Prepare beforehand a place of work with proper and good lighting, arrange tools, lubricants, wipes, etc.

Repair of Bosch ear grinders will not be of high quality if you do not change the grease. For high quality lubrication of Bosch angle grinder parts it is recommended to use lubricants that are offered by the tool manufacturer. Alas their high cost forces to find another way out, and they are.

Russian domestic manufacturers of lubricants have developed special greases for gearboxes and assemblies of bolsters.

Their quality is as good as the greases from other countries, and they are much cheaper. The only disadvantage is that our greases need a more frequent change.

Assembly of the rotor consists of pressing bearings, installation of the impeller. Lubricated bearings are pressed on the shaft using a wooden spacer. The bearing near the manifold is locked by a rubber shield. This is the general method of assembling the rotor shaft.

Pressing in of planetary gear

Pressing process. practically the reverse of pressing.

  • Thrust ball is transferred to the opposite end of the spindle (thread side)
  • Now almost any cylinder serves as a working set-up (huge tolerances between the inner diameter and the planetary gear ring)
  • Everything is prepared in advance for the press-fit (spindle shaft support bearing in the flange replaced. t.к. Personally we, at tight fit, change it in 99% of cases, which is generally in line with regulations and with logic. We also recommend installing the bearings in the well heated aluminum housing beforehand. this way you can install it practically with your fingers, eliminating damage)

There is also the technology to cool the spindle shaft in parallel ❄❄❄❄, but First of all: Our practice has shown that, observing the above, both shaft and pinion lose almost no size ☝. Secondly: with the simultaneous cooling of the shaft, time will run out when pressing, which requires experience and skill. Third: thermal deformation of metals cannot be ruled out

Mechanical faults

the angle grinder is used for polishing, grinding or cutting operations. The tool is subjected to very high loads during operation. It is also subjected to very hard working conditions (dust and dirt).

The heavy loads during cutting operation of the angle grinder cause significant wear on both the gear teeth and the bearing.

The most common mechanical failure of the angle grinder is the destruction or wear of the sliding bearing on the bevel gear.

Solve the problem simply, if there is a description, diagram and recommendations related to repair.

Diagnose the mechanical components of the angle grinder

The bearings and gears in the mechanical part of the angle grinder are most often repaired or replaced (see. rice. below). Wear and failure of these parts is usually accompanied by increased vibration, abnormal noises or gearbox seizure. Their condition is diagnosed visually after the complete disassembly of the gearbox and the results are used to decide whether and what kind of repair is necessary.

In addition, the gearboxes of bucking machines use protective clutches to prevent a sharp jerk of the housing when the disc jams. These units are originally designed for extreme conditions and seldom need to be repaired as a rule.

Checking the locking button

Locking the spindle of angle grinder (stop button) is needed to keep it stationary when tightening the clamping nut. If it starts to sink in, it is necessary to remove the push button, take out the stem and spring, then clean the inside and visually check the condition of the stem, gland and spring. A fixer repair usually involves replacing one of these components (see. video).

Checking the rotor bearings

The bearing of the angle grinder drive shaft, which is the rotor shaft of the electric motor, can be inspected and replaced without complete disassembly of the gearbox. To do this, simply disconnect the gearbox and drive housing (see photo below), and then remove the. Figure. above). If it is decided to repair with bearing replacement, it will be necessary to remove the entire motor rotor, remove the drive pinion (see “Repairing the rotor with bearing replacement”). photo below), then remove the old and put a new bearing.

Disassembly of Bosch PWS 750-115

After the dacha season is over, the tool has migrated from the dacha to the apartment, so it’s time to perform maintenance. This time we will service simple angle grinder, it is “angle grinder” Bosch pws 750-115. Bought the tool in 2009, but not used much, worked a little on repairing the apartment, and then occasionally used in the cottage.

My relationship with grinders at the beginning was not very good, because of the fear of the tool. A colleague at work got hurt because of a failure to comply with the simplest safety precautions (angle grinder wood disc “without a hood” on the weight), in general, the classic case of. But after all these years I had to conquer my fears and start using the tool. I would like to warn you, the angle grinder, as well as any other power tool does not forgive careless and careless handling. Simple Safety Instructions Will Protect Your Health!

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angular grinder bought in a plastic case, the kit included: the tool itself, a key, an additional handle, and traditionally a bunch of waste paper, which is better to read, at least the section “safety work. I disassembled the tool a few times, but because of small use, disassembly ended with opening the gearbox and defective lubrication in it. I want to say one more time that it is better to dismantle tools with expired or non-existing warranty.

Begin disassembly by inspecting the gearbox. First remove the protective cap and clean it from dirt. Remove the four screws fixing the gearbox, traditionally using a “star” bit (torx T20). Let’s take it off carefully from the housing, you may need to pry each side of the gearbox cover with a slotted screwdriver.

When dismounting pay special attention to two metal gaskets, try not to damage them. As I actually expected, in view of the small work angle grinder lubrication in the gearbox is in good condition and does not require replacement.

Since the tool is low-powered, it are spur gears, the tools with high power are usually used helical gears. If the lubricant is not in a satisfactory condition, it must be replaced by discarding the old one completely. All old grease should be removed because it may contain metal particles and new grease should be applied. If, like me, the grease is in good condition, then it should be distributed to the large and small gears, the final assembly of the tool.

Next, detach the gear case from the plastic housing, to do this, unscrew the four screws and carefully separate the parts. There is a lot of dust in the air intake, so be careful not to let dust and dirt get into the tool. Also try not to damage the rubber seal in the form of a ring.

Next, we proceed to the disassembly of the plastic housing and check the condition of the major electrical components. Loosen all the screws on the tool body and separate the tool body into two halves. In one half will remain the motor, the other half will be completely empty. Remove dust from the tool with a soft brush or with air (vacuum cleaner, compressor, compressed air in a bottle). For better access, you can pull out the motor, and you can dismantle the power unit and clean it without disassembling.

Very often, the main fault of the tool is a torn power cable, so if there are strong places of kinks, it is better to cut it and reconnect or even replace it with a new one.

To check or replace the brushes, you must remove the spring and carefully bend back the retainers. After examining the brushes you can proceed to the assembly of the tool.

Assembly is done in reverse order and no problems. When closing the panels and screwing the gear reducer pay attention to the clearances and the absence of “bitten” wires. After assembly, be sure to turn the shaft and make sure that all parts turn smoothly, nothing rattles or cracks. It is better to check it once than search for new gear wheels or a new tool. As a result the tool can be serviced by your own efforts and without much hassle.

I will be glad if I helped anybody! If you liked this article, click. “This is helpful!”Write your feedback, criticism and suggestions in the discussions! Thank you all! Good luck to you all! Let your tool last a long time and bring only positive emotions!

Cleaning and lubrication of the Bosch GWS 750-125 angle grinder

Finished repairing the apartment, just cleaning and lubricating the tool. This time an angle grinder from Bosch. Before I say that the tool is not happy with it, as it was new it already squeezed the oil through the spindle lock button, why the button starts to stick and at some point it gets so much dust and oil, that the spindle can not be locked anymore. It is only two years old, I mostly used it to clean the old machines from paint and putty. The work is very dusty, so-so it is time to disassemble and bleed at least.


Unscrews 4 screws, Torx T15, open the lid. There is a rubber O-ring on the cover, do not damage it.

You can see that the gears are dry and grease looks like dirty plasticine, how this could happen in a couple of years is unclear, I will wash in ultrasound.

Unscrew the screw on the back and remove the cover. A considerable amount of already compressed dust is falling out. Apparently, the angle grinder is forcing the dust in.

We unscrew 4 screws, pull slightly, it is not necessary to pull further, brushes are resting against it. We shift the spring holding a brush, and slightly take out a brush from a jack. Same for the other side. Take out the rotor.


Assembly and greasing

Parts washed out. You can see the bronze bush, no bearings of course. The rotor showed a low dust content when blown out, unlike the stator and housing.

Return the brush compression spring. Don’t forget or else tragedy!

Put grease on, cover and turn a few times. Open it up for inspection and add more grease if needed.

Screw the gearbox to the housing and the gearbox cover.

Lay the wire as far as possible from the button.

Unfortunately the given angle grinder is inclined to fill up dust. Fortunately, the rotor is rather clean, all the stain is collected in the back. The lock button will always be clogged, it is inherent in the design, perhaps you can just periodically blow under it.

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