Any power tool contains in its design rotating parts that are subject to increased wear as a result of friction. It is possible to prevent their premature destruction and extend the service life of the tool if timely preventive maintenance of rubbing parts is carried out. In the grinder, the main wear is subject to gear reducer. The harmful effects of friction can be reduced by applying lubricants to the surface of parts. Let’s consider what kind of lubricant for the grinder gearbox is better to buy.

When to change lubricant

With intensive daily use of the grinder, the lubricant in the gearbox should be replaced at least once a year. Often, users do not adhere to certain terms of preventive maintenance of the tool, and routine maintenance is carried out after the appearance of extraneous sounds during operation. This is absolutely not the correct way to care for the gearbox.

Rattle during rotation, rattling indicate that wear has formed on the gears, and they will soon have to be replaced.

A preventive inspection of the gearbox begins with the separation of its casing from the rest of the grinder. To do this, just unscrew the four fixing screws.

Gear lubrication

The next photo shows that there is grease in the case, but it has collected on one side of the case, and there is not enough of it.

The location of the lubricant in the gearbox

This is because the angle grinder (angle grinder) is working at high speeds. Under the influence of centrifugal force, oil particles tend to move away from the axis of rotation. With prolonged operation, the surfaces of the gears become completely dry, and without lubrication, the metal is erased. In this case, it is enough to lubricate the gear teeth with the existing composition, then close the gearbox and work until the next maintenance.

Often in the gearbox you can see grains of oil mixed with dust. During operation, the grinder heats up, and these grains are sintered, solid particles interfere with the operation of the mechanism. This lubricant must be replaced.

How to lubricate the gearbox

Any tool that has moving parts needs periodic lubrication. Especially if it is actively used. With regard to angle grinders, the consistency and composition of the lubricant must meet certain requirements.

Lubricant features:

  • absence of solid particles;
  • maintaining viscosity at temperatures above 100 degrees;
  • good adhesion;
  • moisture resistance.

The presence of hard or even worse abrasive elements in the composition will cause abrasion of the working surface and individual parts of the device. A cheap lubricant simply evaporates when a temperature threshold of 100-120⁰С is reached. Therefore, special attention should be paid to the maximum permissible values ​​​​of the lubricant, otherwise the tool in the heat of work will remain without lubrication.

A good composition protects the surface from moisture, as well as from subsequent corrosion, which means that it must have water repellent properties. The adjusted consistency allows the lubricant to be retained on the surface: too thick lubricant will impede the operation of the mechanism, and the liquid one will simply drain into the gearbox.

gear lubrication angle grinder

Viscosity of lubricants for power tools is classified according to the NLGI standard (abbreviation for “National Lubricating Grease Institute”). The choice of one or another consistency depends on the specific angle grinder model, namely, the speed of rotation of the gearbox. The higher this indicator, the less dense the lubricant should be.

Viscosity classification for power tools:

  1. NLGI 00. The most liquid consistency used in heavy equipment: jackhammers, professional rock drills, etc.
  2. NLGI 0. This is a semi-liquid composition, which is just used for angle grinders, as well as circular saws and gasoline braids.
  3. NLGI 1. Sufficiently viscous consistency for use in construction hammers and medium power impact drills.
  4. NLGI 2. Soft type of lubricant. It is used in household jigsaws, light hammers and drills.

The required grade of lubricant must be specified in the instruction manual for the equipment. If there were no documents with the grinder, then all the parameters of the model should be indicated on the official website of the manufacturer of the equipment.

Finished lubricant

Manufacturers of power tools are advised to use special compositions of their own production. Such recommendations are given, in particular, by Makita and Bosch.

Lubricant "Bosch"

You can buy such funds, but their cost is quite high, and the costs are not always justified. Firm “Interskol” more democratic to the type of materials used. What is the best lubricant? The lubricant for the grinder gearbox must meet certain requirements:

  • the viscosity of the composition does not exceed 800 Pa * s;
  • temperature of separation of drops from the main mass is not less than 120°С;
  • homogeneous composition without the presence of mechanical inclusions;
  • resistance to moisture.

The industry produces many types of lubricants, including special formulations for use in gearboxes. Mixtures containing molybdenum disulphide as an extreme pressure additive show the best results. If we talk about foreign manufacturers, Castrol and Mobil have proven themselves well.

“Mobil” for ease of use places products in tubes that have the shape of a syringe.

From domestic brands, MS-1000, Limol can be noted. The use of grease, litol or Ciatim-221 does not give the desired result.

Homemade mixes

If the required lubricant is not on sale, or if the user considers the price of the product to be unreasonably high, you can try to make the lubricant mixture yourself. There are several recipes using different bases. One of them is common Ciatim-221.


Transmission oil TAD-17 is added to the container with Ciatim. Whisking continuously, add the oil one drop at a time until the desired consistency is reached. The mixture should adhere well to the parts, not be too thick or run like thin oil.

Transmission oil

Another base can be CV joint grease in combination with MS-20 liquid oil.

Lubricant "CV joint"

How to lubricate the gearbox

First of all, it is necessary to disconnect the equipment from the mains and clean the case from dust, dirt and other debris. The lubrication procedure includes several stages: opening the protective cover, disassembling the gearbox, cleaning from the old lubricant, filling in a new one and checking.

Removing old grease

The gearbox must be cleaned of the remnants of old grease and wear. In no case should you add a new lubricant, mixing it with the previous one. The fact is that used grease carries solid particles.

removal of old grease

Remove old grease first

Advice! Old grease is best removed with a soft cloth that absorbs moisture well. You can also use paper towels. An ordinary rag will simply drive dirt and solid particles through the gearbox without absorbing anything.

All parts must be treated in solvent or gasoline, and then dried thoroughly. Neither the first nor the second should get into the new grease, because they will change its characteristics for the worse.

Lubricant application

Before pouring, make sure that there are no foreign elements in the composition, and that the consistency is uniform – without lumps or light / dark spots. Grease is applied to moving parts in a thin layer, but in such a way that it covers all parts of the mechanism.


in bearings lubricant is easiest to add with a conventional syringe. After processing the parts, you can pour the composition into the gearbox.

Lubrication amount

Permissible volumes of material are specified in the operating instructions. Excess lubrication is no less detrimental to the tool than its lack. Lubricant must completely cover the gear teeth. Due to the insufficient amount of material, the moving parts wear out quickly, and the tool itself will begin to smoke under heavy load.

Lubrication in the gearbox

Excess lubrication makes it difficult for parts to work, plus oil will ooze through all the cracks and fasteners.

Advice! In the absence of documentation for the equipment, you can focus on the figures of 40-50% of the lubricant from the total capacity of the gearbox.

Application control

The last step in changing the lubricant is to check the equipment in light mode. After assembling the structure, you need to make sure that all parts are tightly fitted to each other, and the fasteners are securely tightened. Semi-liquid NLGI 0 is able to seep into even tiny holes, especially during prolonged operation of the equipment, when the oil is heated to over 100 ° C.

We turn on the grinder at low speed and make sure that there are no extraneous sounds. At the first start, a slight burning smell is considered normal and should be gone in less than a minute. If this does not happen, then the equipment must be turned off and the build quality checked.

Particular attention should be paid reducer unit temperature. The task of the lubricant is to evenly distribute heat. Regular temperature indicators for the engine and the structure as a whole are indicated in the specification for the angle grinder. They should not exceed the norm.

After a blank check, the equipment must be disassembled and the correct lubrication must be assessed. We open the gearbox and inspect the helical gears. If they are completely covered with lubricant, then it is applied correctly. Surpluses can be traced almost immediately after turning on the machine: oil on the slots and in the places where the gearbox is attached.

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