Changing the grease in the gearbox of an angle grinder Bosch

Selection of grease for angle grinders or what is the best way to lubricate the gearbox

Angle grinders, commonly referred to as angle grinders, are widespread among DIY enthusiasts. With their help, the home maker can not only perform grinding work, but also to cut metal, plastic, stone. Angle grinders are made by various manufacturers, including domestic.

Angle grinder is a reliable tool that can work, with proper use and timely replacement of grease and carbon brushes, for a long time.

Properly selected grease for angle grinder not only extends the life of the tool, but also improves performance.

Knowing the rules for selecting grease for angle grinder or preparing it with your own hands, you can perform maintenance without turning to the service.

The process of applying grease

It is better to apply grease in a special room. You can go to a craftsman, or you can do it yourself. To begin with, it is necessary to disassemble the angle grinder and remove the layer of old lubricant. Old coatings must not be present on the elements. Step-by-step recommendations for lubricating the mechanism include the steps:

  • Disassemble the tool.
  • Using kerosene, gasoline gently wash all parts of the gearbox and remove the old grease.
  • Dry the elements.
  • Open container with grease, mix compound.
  • Place on the bearings and place in the cavity.
  • Assemble all the parts.

Often, users wonder how much grease is needed. Using a large amount of the substance will cause it to leak out of the gear housing during operation. In the future, the angle grinder can suddenly break. Take half the amount of substance in the gearbox.

How to use?

Do not just put grease on the nodes as you have to. Determine correctly where to apply grease, in which order, and how much grease mixture is needed. There is a maintenance plan for the angle grinder. It is clearly spelled out when to change the grease. This is usually done when parts break or fail.

Old grease can be identified by its appearance, it has a dirty dark color. This is caused by dust and metal particles that get into the grease during operation. Outdated grease is usually replaced. There should be no traces of old lubricant on the parts. If a component breaks down, all particles left in the housing compartments must be thoroughly removed.

Often, flushing liquids are used to remove grease. These include the motor cleaner blends often used by drivers. If you don’t have one on hand, you can always use kerosene or gasoline. After treatment it is desirable to dry the parts well. After cleaning, proceed to grease application. It must remain in a thin layer.

The bearings should be lubricated as if they were packed. Lubricants are simply squeezed out of the tube until they flow out the opposite side. Everyone is interested in how much grease should be. When applied to bearings, the amount of grease is regulated by the outflow.

But the situation with the gearbox is different. There are certain norms for it. If you overdo it, grease will leak out. But an insufficient amount will not bring good results in the work of your machine.

Fill the gearbox with the amount of grease that completely covers the gears. It is very easy to control the correctness of application. To do this, simply turn on the assembled angle grinder for a short period of time. If the gearbox became hot in a couple of minutes, there was leakage of mass, the amount of grease was obviously too much. In this case, you need to reduce its quantity. To do this, simply disassemble the gearbox and use something to remove the excess grease.

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But if when you turn on the angle grinder appeared a loud noise, then the amount of grease is insufficient, and this point must also be corrected. It can lose its properties with prolonged operation of the angle grinder. From time to time it is necessary to check its quality. To do this, open the gear cover and inspect the part. If you can see dry or slightly dried out areas of grease, it means that it needs to be replaced.

The compound for the gear wheels will be suitable for lubricating the gearbox of the angle grinder

Before you lubricate your angle grinder, you need to familiarize yourself with the main types of grease. The following mixtures are most commonly used to treat the gearbox of an angle grinder:

Important! If you can not afford to buy brand products, it is better to use mixes for CV joints. You can find them in almost every car shop.

What is the best lubricant to use for an angle grinder

Many people wonder what kind of grease is needed for the gearbox of the angle grinder and what is better to use. To understand this, you need to familiarize yourself with the peculiarities of the choice of lubricating compositions for tools from different brands.

grease, gearbox, angle, grinder, bosch


Bosch is a fairly popular manufacturer of drills, torches, grinders and other power tools. People who use devices from this brand can use their brand lubricants. They are sold in small tubes of 50 ml to 100 ml. It is enough to thoroughly lubricate a gearbox 3-4 times.

If you can’t get Bosch grease, you can look for universal mixes. Also suitable is solidol or compound for joints and Metabo angle grinder.


Makita grease is one of the most expensive on the market

This company, like Bosch, also produces power tools and lubricating compounds for them. Although Makita’s catalog of lubricants is small, it is still possible to find the right compound for machining the gearbox.

They are most often sold in large 500 ml plastic containers. In rare cases, you can find small disposable 30 ml tubes.

Further information! Makita greases are many times more expensive than other brands.


It is a famous Chinese-Russian manufacturer, which rapidly grows in popularity. It is worth noting that Interskol makes not only angle grinder, but also lubricants for them. There are at least ten items in the brand’s catalog. They are used to handle tail drills, gasoline engines, gears and saw structures.


DeWALT is a popular American brand specializing in high-tech power tools. This manufacturer does not produce branded lubricant mixtures and therefore you will need to select the appropriate composition. Solidol, lithol and grease for CV joints can be used.

Possible electrical problems

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

Simple electrical malfunctions of Bosch angle grinders

If you turned on your angle grinder and it refuses to work, start troubleshooting with a broken power cord. Most often, a wire breakage occurs at the entrance to the angle grinder or the plug. Do not allow any twisting, this will cause a short in the tool.

To determine if this is a problem, you need to open the handle covers on the angle grinder. Bosch angle grinders up to 1000 watts have a single screw in the face for the cover. On Bosch angle grinders over 1000 W the handle cover is fastened with few screws.

Using a tester, check power wiring from input plug pos.5 to the switch. If the circuit is intact, proceed to check the switch operation. Bosch angle grinders have a simple on/off switch that is operated by the on/off lever.

But the electrical contacts in the switch burn out and cause the angle grinder to malfunction. It is not practical to replace the contacts on the plastic switch with a new one.

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If the switch is intact, use a tester to check for a circuit from each plug pin to each carbon brush.If circuits are intact, the angle grinder must always start. If it doesn’t rotate, then the problem is in the mechanical part. Jammed gears or destroyed bearings are possible.

Checking the motor

If your Bosch angle grinder is picking up speed regardless of you, starts to get very hot, sparks, you need to pay attention to the integrity of the rotor windings, stator.

Unintentional rotation of the angle grinder indicates a faulty stator winding. Use a tester to check the windings for continuity, or a special tool to detect short circuits between the windings.

How to Identify a Rotor Failure

Repair of the rotor is a complex technological process, accessible to craftsmen with straight hands.

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

It is preferable to have the rotor repaired in a specialized workshop. And you can rewind on your own, if you decide to do the repair of the Bosch angle grinder with your own hands.

Dark-colored rotor windings and burned-out manifold lamellas are indicative of a short circuit in the rotor circuits. The malfunction can only be eliminated by replacement with a new rotor.

Stator Repair

Repairing a Bosch angle grinder also includes rebuilding the stator. The main sign of stator failure is the spontaneous increase in speed of the angle grinder, which can not be reduced by adjustments.Stator coil becomes discolored and darker if burnt. Stator core darkens due to high temperature.

The stator is easier to rewind, although it is necessary to observe certain rules and sequence.

If you have removed the stator housing cover, carefully inspect the carbon brushes and rotor header blades.

The length of the carbon brushes must not be less than 8 mm. By the way, in Bosch angle grinders are used carbon brushes with a “shot”, a device that stops the angle grinder at the minimum length of the carbon brush.

Collector blades must not show any signs of soot or wear. Fouling can be easily removed with absorbent cotton soaked in alcohol.

Speed regulator malfunctions

The Bosch brushcutters, especially the low power ones, are equipped with speed controllers. The speed regulator is accessed by opening the knob on 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 handlebar.

The faulty regulator is easy enough to remove, because it is mounted only on the guide.

Repair of the speed regulator of angle grinder is a complex process, the performance of which requires not only special knowledge but also tools and equipment.

If a speed regulator has failed and no new speed regulator is available, disconnect input leads and install a jumper.

The red one shows the jumper that is installed when the speed regulator goes out of service.

grease, gearbox, angle, grinder, bosch

What grease to choose

There are several ways to reduce frictional effects on the interacting elements of the angle grinder gearbox. The choice of what to lubricate the friction units is made from these options:

  • the use of expensive special greases for gearboxes from well-known brands;
  • The use of universal compositions suitable for any power tool;
  • Greasing the gearbox with lithol or solidol;
  • using a self-made lubricant.

Application of special materials is the optimal solution. When selecting grease for the gearbox, it is recommended to give preference to compositions produced under the same brand as the angle grinder itself. For example, if the machine is brand AEG, then lubricant should buy the same brand.

When using specialized products, the service life of the angle grinder increases significantly, as the manufacturer takes into account all the features and nuances of operation of their own equipment. The disadvantage of using brand materials is their high cost, which can affect the family budget.

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Most craftsmen use budget lathes or Chinese-made tools. For such machines, specialized lubricating compositions manufacturer has not developed and is unlikely to ever appear. However, even such equipment requires maintenance. What to do in this case?

Specialists and service craftsmen recommend buying any budget non-branded compound designed specifically for gearboxes. You can also use the grease used for CV joints in cars with front-wheel drive, which are operated under considerable loads. It can be easily purchased at any auto shop. This option is much worse than the use of branded materials. This is due to the fact that the specifics of the friction units of two different mechanisms are not taken into account.

The worst solution is to use lithol or solidol, since both are not designed for the lubrication of friction units that are heated to high temperatures. Some owners of bolt cutters use only these compounds, so their machines can’t last as long as declared by the manufacturer. In an effort to get a profit here and now, they do not consider the future costs of buying a new tool or replacing expensive parts.

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. I have to say that I’m not happy with the tool, when it was new it already pumped oil through the spindle locking button, so the button begins to stick and at some point it gets so much dust and oil under it that it is impossible to lock the spindle anymore. It’s only two years old, I used it mostly to clean old machines from paint and putty. The work is very dusty, so-that is time to disassemble and blow out at least.


Unscrew 4 screws, Torx T15, open the lid. There’s a rubber O-ring on the cover, don’t damage it.

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

Unscrew the screw on the back, remove the lid. Not a small amount of already-compressed dust came out. It looks like the angle grinder is forcing the dust in.

Unscrew 4 screws, pull slightly, no need to pull further, brushes are resting. We put the spring that retains the brush, and slightly remove the brush from the socket. For the other side is similar. Pull out the rotor.


Reassembly and Lubrication

Parts are washed out. You can see the bronze bushing, no bearings of course. The rotor was dust-free, unlike the housing and stator.

Return the pressure spring of the brushes. Do not forget or else tragedy!

put grease, cover and turn several times. Open to check and add as necessary.

Screw the gearbox to the housing and the gearbox cover.

Lay the wires as far away as possible from the push button rod.

Unfortunately this angle grinder tends to fill itself with dust. Fortunately the rotor is rather clean, all the stain collects in the back. The lock button will always get clogged, it’s in the design, you can probably just blow under it periodically.

Bosch Angle Grinder GWS 6-115. Bevel Gear Replacement

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