Lubricant for the rotary hammer gearbox: differences from conventional lubricants

A rotary hammer is one of the heavy-duty household tools. The impact reciprocating mechanism is a separate discussion; in our material we will look at an equally important unit: the gearbox.

It works hard in any mode: drilling, perforation drilling, impact mode. Maintenance and lubrication of the rotary hammer gearbox is a mandatory procedure and is performed regularly using high-quality consumables.

Moreover, this is not just anti-friction oil; each manufacturer of power tools includes certain characteristics in the composition, they must correspond to operating conditions.

How does the gearbox (transmission mechanism) of a hammer drill work?

To understand the importance of selecting consumables, let’s consider the structure of this loaded unit.

The mechanism can be made in two versions:

1. The hammer drill gearbox is separate, the reciprocating mechanism is separate. The piston group has its own lubricant; the gears of the transmission unit do not come into contact with it.
2. The hammer drill is implemented using a ratchet design. In this case, the gearbox and impact mechanism are one whole. Accordingly, they have the same lubricant.

The transmission unit itself consists of a pair of gears (with a standard layout). A planetary layout is possible, in which case there will be more gears. The teeth can be straight or oblique (if the mechanism is designed for heavy loads).

Using a gearbox, the gear ratio is changed:

• the rotary hammer spindle shaft rotates at a lower speed relative to the motor rotor;
• Accordingly, the torque on the chuck increases in proportion to the decrease in speed.

In this way, two problems are solved: mechanical traction increases and speed decreases, for better control of drilling.

Video description

In this video, see what kind of lubricant to lubricate the gearbox of an angle grinder and how to do it quickly and inexpensively:

Why do you need to lubricate the transmission unit?

No matter how strong the metal of the gears is, the friction of the teeth against each other inevitably leads to wear.

In addition, in the absence of anti-friction lubricant, the gears become very hot during operation, and the so-called “tempering” of the hardened steel occurs - the metal loses its hardness. After this, rapid wear and even breakage of the teeth occurs.

In addition to standard loads (when gears engage during rotation), the teeth can move in the longitudinal, axial plane. This happens when the hammer drill is designed using a ratchet design.

The small gear, together with the movable shaft, moves back and forth relative to the large one. Accordingly, the lubricant should ensure unhindered sliding.

In addition, the gearbox shafts rest on bearings. If they are not sealed (with their own lubricant embedded), the same composition is used (all mechanics in one housing).

There are many greases that are used both on cars and “heavy” mechanisms, and in household (professional) electrical appliances. However, a conscientious user of an electrical appliance tries not to use universal compounds.

Some tips for extending the life of your hammer drill

Any perforating type tool requires maintenance and preventive inspection. Following a few simple rules will allow the owner to significantly increase the service life of his device:

• Do not allow dust and dirt to get into the cooling holes (in extreme cases, they can be protected with an old nylon sock);
• It is preferable to treat shanks with “native” lubricant;
• Try not to allow the device to overheat, because in this case the lubricating substance crystallizes and ceases to perform its function;
• If the device is used in difficult conditions, then the rear rotor bearing should be changed every six months, and the carbon brushes should be changed every 70 hours of operation;
• After making the holes in the ceiling, the device should be turned upside down and “scrolled” a little so that the lubricant flows back onto the protected parts;
• At the end of the work, it is recommended to blow out the insides of the equipment with compressed air;
• It is also recommended to change the rubber cartridge collar more often;
• Sparking should not be allowed to occur on the commutator brushes during “dry running”;
• A one-time working period should not exceed half an hour;
• Do not overuse the equipment frequently in the “Impact” mode.

So, how to lubricate the gearbox to minimize its wear?

You must understand that power tools are sold ready to use. This means that the transmission unit of a new rotary hammer contains the right amount of oil, and it is “correct”.

Tool owners also know about the need to constantly lubricate the shanks of the working attachments. Grease for these purposes is almost always included in the tool kit.

Important, as an example!

The lubricant for the Makita rotary hammer gearbox, and the composition of the same brand marked “for drills,” are fundamentally different from each other. Consumables for the gearbox are marked with the generally accepted designation in the form of two gears.

However, not all manufacturers generously equip their tools with lubricants. Sooner or later, the owner has a question: what lubricant to use for a hammer drill?

Since universal lubricants (for example, Litol-24) are not always suitable for these tasks, it makes sense to look for trademarks of power tool manufacturers.

For example, lubricant for the Bosch rotary hammer gearbox is also suitable for other models. Elementary logic: if mechanical components operate under similar conditions, then the lubrication requirements are the same.

Just one point needs to be taken into account: the hammer drill mechanism must be exactly the same as that of the Bosch tool for which this lubricant is intended.

Briefly about the main thing

To increase the service life of power tools, it is necessary to use only high-quality lubricants. In particular, for uninterrupted operation of the rotary hammer, it is better to opt for specialized compounds that the manufacturer supplies with its products. This will guarantee the correct selection of the necessary lubricant components for this particular model.

You can also use products from leading manufacturers of oils and lubricants. Their universal materials are of high quality and are not much inferior to specialized products. The only condition in this case is the need to change oils more often than usual.

Types of lubricants for gearboxes

Liquid lubricant

Similar to regular car motor oil. It is used in hammer drills with a hermetically sealed gear housing. The rotating shafts in such devices are sealed with oil seals, with the help of which the oil is retained inside.

Lubrication is carried out through special holes, which are then tightly closed. The system is very effective because gears and other elements subject to friction are evenly coated with an antifriction compound.

In addition, the working fluid acts as a heat sink and helps cool the gearbox by coming into contact with the walls of the housing. However, there is a drawback: when heated, the pressure in the sealed gearbox housing increases.

Since there is no breather (like in a car engine crankcase), loss of lubricant squeezed out through the seals is possible.

Grease

It is much more widespread due to ease of use. It has a thick consistency and good adhesion. It is applied to the gearbox parts in the disassembled state of the latter.

In this case, it is enough to simply control the amount of lubricant. When cold, the lubricant is thick enough to adhere firmly to the mechanisms. After assembly, complete sealing of the gearbox is not required; high-quality gaskets and sealing bushings on the shafts are sufficient.

During operation of the hammer drill, when the gearbox heats up, the viscosity of the lubricant decreases and it spreads evenly over the surface of the parts. After cooling, the lubricant thickens again and is fixed on the gears.

What it is?

Lubricant is a viscous substance that reduces the coefficient of friction between tool parts. The operation of a rotary hammer is associated with a huge number of different rotational movements, which increases the degree of wear of structural elements.

When drilling, quite a lot of dust is released, which significantly impairs the operation of the device, which is why it requires periodic lubrication.

Properties of gear lubricants

The standard characteristics of thick oils for general use are not suitable for a rotary hammer gearbox. Only compositions for automobile CV joints have similar parameters.

Some properties are generally unique, since the gearbox mechanism does not simply operate under large variable loads. When the impact mechanism operates, the lubricant is spontaneously squeezed out of the contact zone.

Composition requirements

1. Adhesion must be so high that an oil film remains between the parts under any load.
2. A high level of water resistance is required - rotary hammers can operate in conditions of high humidity. When cooling, a reduced pressure occurs in the gearbox housing, atmospheric air along with liquid vapor is sucked inside.
3. If water gets in, an emulsion should not form.
4. Since the gearbox gets very hot during operation, the lubricant thins out due to temperature. In this case, the basic properties should be restored after cooling. The heated composition should also not lose its basic antifriction parameters.
5. Requires high dropping point. Otherwise, the rotating gear, under the influence of centrifugal forces, will throw lubricant from the surface of the teeth.
6. Fine cement (stone) dust gets into the gearbox housing. The composition of the lubricant is selected in such a way that abrasive particles are bound and removed from the zone of intense friction. When using good oil, the dirt is always on the walls of the gearbox, and not inside the gears.
7. Since the gear housing is made of aluminum alloys and the gears and bearings are made of alloy steel, the anti-corrosion properties should be equally suitable for both metals.

The same properties (with the exception of dropping point and adhesion indicators) must be present in liquid compositions. In a sealed gearbox housing, lubricant adhesion is not required: liquid oil constantly washes all parts of the mechanism during operation.

Installing the mode switch lever

The mode switch is designed to move the clutch, pos. 39, to various positions and transmit translational motion to the shaft of the impact mechanism through the rolling bearing, pos. 41, to the cylinder, pos. 32.

Assembly of the mode switch lever for the Makita 2450 rotary hammer

On the axis of the inner housing you need to put the mode switch lever pos. 82 on top, press the pressure spring pos. 88 on top, and press it with a flat washer pos. 87. Install the locking ring pos.86. and fix it.

The retaining ring must be carefully secured. When turning the intermediate shaft, you must carefully check the correct operation and free movement of the cylinder in the housing. This must be done now so that it does not become clear at the end of assembly that the assembly was assembled incorrectly.

Which manufacturers produce gear lubricant?

General purpose brands such as Castrol, Xado, Ravenol, Shell, etc. Of course, these products do not have approval from the hammer drill manufacturer. But the description must contain information that this is a lubricant for a power tool gearbox. All you have to do is choose the right consistency. Information about this is in the technical documentation of the tool.

• Specialized brands: Bosch, Makita, Lubcon, AEG. This is a better choice, but you should be more careful when purchasing. The documentation for the lubricant may contain a list of specific models of the hammer drill manufacturer. Compatibility with tools from different brands is determined by consistency and similar characteristics.
• An interesting product: semi-liquid lubricant for gearboxes “ULTRA”. This is a compromise between consistency and liquid oils.

The lubricant easily turns into a liquid state with slight heating, and at the same time has excellent adhesion. Therefore, this product can be used in both crankcase and non-sealed gearboxes.

Instead of an epilogue

An analysis of the market for the lubricants in question has established that this important element of maintenance activities for such an expensive tool as a hammer drill has a relatively low cost. Despite the fact that finding a quality option on today’s market is not a problem. At the same time, the problem of counterfeit products from world-famous brands is acute, therefore, professionals advise purchasing lubricant from trustworthy online stores or trusted retail chains. Separately, it is worth mentioning Russian lubricant manufacturers, who today manage to produce completely universal options that are not inferior in quality to special foreign ones, and which have a significantly lower cost, and they can work with a large number of different devices.

How to properly lubricate the gearbox

Having decided on the choice of brand, we proceed to routine maintenance. Liquid oils are drained from the gearbox in the same way as in a car. If the waste looks too dirty and is saturated with abrasive inclusions, the gearbox should be washed with a special compound.

You can also disassemble the housing and perform a thorough cleaning. Then careful assembly is carried out (if necessary, replacing the gaskets), and the new composition is poured through the standard holes.

Step-by-step video instructions for lubricating the rotary hammer gearbox

The amount of oil is indicated in the documentation. If it is absent, you can measure the volume of drained waste. True, natural losses should be taken into account.

With consistency compositions it is somewhat simpler. The gearbox is clearly disassembled, the components can be removed (be careful not to lose the springs and retaining rings).

Then the metal parts and gear housing are thoroughly cleaned and rinsed. Kerosene is usually used (aggressive detergents can damage sealing bushings and gaskets).

Lubricant is applied to the assembled gearbox (without cover). It must completely cover all gears and moving parts of the mechanism. The layer thickness is no more than 5 mm, the internal cavities are completely filled.

However, you should not work according to the principle: “you can’t spoil porridge with oil.” Excess lubricant will complicate the operation of the mechanism and will definitely come out, damaging the gasket or oil seal along the way.

The illustration shows how not to lubricate the gearbox.

This is not the way to lubricate the gearbox!

The frequency of replacements does not depend on calendar days, but on the number of engine hours. Information about this is in the documentation for the tool. It should be remembered that “station wagons” like Litol last less.

Design Features

Such power tools are cylindrical and straight, mechanical and pneumatic, depending on the size. Light, medium and heavy.

• Core;
• Boer;
• Attacking;
• Piston;
• Cylinder;
• Electromagnetic coil.

There are differences in details depending on the type of attachment. And that's not all the details on the list. So, how useful are punching tools in construction work? The units, in addition to the specified parts, are equipped with:

In addition, such tools have various indicators and speed controls. After understanding the nuances of this construction tool, it’s time to move on to lubricating some of its elements.

Features of servicing an electric drill with a perforation function

An electric drill that works with a hammer drill function is much more difficult to maintain. This hybrid tool has some disadvantages, unlike a regular drill:

• They do not have special containers for pouring oil;
• It is much more difficult to maintain the pipe.

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Permanent lubrication is required only for the drill tip. The amount of oil is minimal: just clean the drill from dust and apply a small amount of solid oil (the size of a match head) to the tip. The same requirements apply to lubrication of a conventional drill. Excess lubricant during a storm will not damage the mechanism of the tool, but in any case it will be sprayed and can damage the room. But if too much oil enters the transmission, it simply spreads.

We need to talk a little about professional rotary hammers. At home, this tool is usually not used. Here, first of all, the price of the instrument plays a role, and therefore it is chosen much less often. But at the same time, this tool is considered the simplest and most unpretentious to use. There are usually no problems with the oil of this tool, because the design of the mechanism is very simple.

The gearbox also does not have features that would complicate maintenance. It's simple: unscrew the drain valve, pour used oil into the tank, wash the oil tank out of the drill, unscrew the drain hole and fill in new oil to the desired level. The gearbox of this rotary hammer is maintained in exactly the same way as described above.