Sandblasting gun for compressor

To clean a metal surface from varnish or paint, you can use special attachments for angle grinders. Appropriate hand tools are also used for such purposes. In addition to angle grinders and hand tools, metal surfaces can be cleaned with a sandblasting gun for a compressor. Let us find out in detail why it is worth using this tool and how effectively it copes with the assigned tasks.

What is a sandblasting gun and its purpose?

A sandblasting gun is a nozzle for a compressor, which is designed to clean car body surfaces from stubborn dirt and paintwork. The sandblasting attachment is popular in auto repair shops for painting cars, but nothing prevents a home craftsman from buying a gun for a compressor and using it to clean any metal surface, which is often done before painting, patination and anodizing.

Externally, the nozzle almost completely resembles a gun for blowing or painting a compressor, but there is still a difference. The main structural elements of the device are:

Metal body in the form of a pistol
Channel - hose for supplying abrasive substance to the gun
Nozzle - a hole through which sand flies out under pressure and hits the surface being treated.
Handle with trigger - designed to hold the tool body, as well as to start the sandblast feed
Adjustment screws for adjusting air pressure and abrasive feed rate

The most important element of the device is the nozzle, which must be made of high-strength materials such as tungsten or ceramics. If you choose sandblasting guns for a compressor with a nozzle made of plastic or thin metal, then such a tool will not last long. The nozzle will very quickly fail under the influence of abrasive substances.

The operating principle of a compressor sandblasting gun is that fine sand flies out of the nozzle under the pressure created by compressed air. This removes paintwork and other contaminants from metal surfaces.

This is interesting!
Sandblasting is intended not only for processing metal surfaces, but also for removing contaminants from plastic, wood and other materials.

Making a homemade nozzle

In order to turn a Karcher mini washer into an effective sandblasting unit using a homemade nozzle, you will need the following structural elements:

a nozzle through which a mixture of water and sand will be supplied to the treatment zone;
trigger;
reinforced hose that will be able to withstand high pressure;
dispenser necessary to make the consumption of abrasive material more economical.

Nozzle diagram: 1 – thread; 2 – low pressure chamber; 3 – nozzle; 4 – fitting for sand supply; 5 – junction of two parts of the nozzle; 6 – smooth tapering transition

For the nozzle, if you intend to use your sandblaster regularly, it is best to purchase one that is made of ceramic. This type of attachment, which is constantly exposed to abrasive material, will last you much longer than its metal counterpart.

Homemade water sand blasting nozzle

Nozzle details: 1 – pistol; 2 – nozzle; 3 – nozzle holder; 4 – sandblasting nozzle

The efficiency of the sandblasting machine with a homemade nozzle, which you will equip your Karcher sink with, is greatly influenced by the quality of the nozzle. It’s worth starting to create such an element yourself only if you have the opportunity to drill an exact hole in a metal rod, the diameter of which is at least 15 mm. But if this is not possible, then it is better to purchase a factory nozzle, the quality of which will determine the operation of the entire device. The advisability of purchasing a serial nozzle also lies in the fact that some models of such products are already immediately equipped with triggers.

When choosing a hose, the length of which must be at least 2 meters, you should pay attention only to reinforced products. This is explained not only by the fact that such a hose will work under high pressure created by the compressor, but also by the fact that its internal walls will be constantly exposed to abrasive, which will quickly render the unreinforced product unusable.

When starting to assemble and attach the nozzle to equip the Karcher washing machine, you should adhere to the following algorithm of actions:

a ceramic or metal tip must be fixed to the nozzle of your homemade nozzle using a threaded connection;
the dispenser, with which you will regulate the flow of the water-sand mixture coming under high pressure from the nozzle, should be attached to the metal or ceramic tip of the nozzle;
the hose through which sand will be supplied from the hopper must be secured to the back of the nozzle, for which a fitting and a clamp of the appropriate diameter are used.

Scheme of operation and example of manufacturing a nozzle for collecting sand

When assembling and installing a nozzle for Karcher, you should take into account the fact that all elements of such a device will operate under high pressure created by the compressor of the device. That is why all formed connections must be ensured with maximum tightness and reliability. It is not difficult to fulfill this requirement if you make such connections using a special fum tape.

There is one more trick that will allow you to save abrasive material. It consists of the following: cleaning must be performed over a special container with a grid into which the waste mixture of water and sand will be collected. This mixture can be reused by lowering the end of a reinforced hose into it, which is connected to the nozzle of the device. There must be a grate on the top of this container; it is necessary in order to hold processing waste and prevent it from getting into the water-sand mixture.

Karcher sink with sandblasting nozzle in use

How does a sandblasting gun work?

If you decide to use a sandblasting gun for the first time, it will not hurt to first understand the question of its operating principle. Knowing the principle of operation of the nozzle, it will not be difficult to learn how to use it. First, let's find out how a sandblasting gun from a compressor works:

The gun is connected via a hose to the compressor through the receiving fitting
The air enters a special chamber where its pressure can be adjusted
The air is directed through the channel to the nozzle
Due to the passage of air through the channel, sand and abrasive are sucked from a special container (due to the pressure difference)
The amount of sand sucked in by air can also be adjusted with a special screw, which depends on the tool manufacturer
Not only compressed air is supplied through the nozzle, but also sand with abrasive particles, which have a cleansing effect on the surface

The operating principle of the tool is somewhat similar to the functioning of a spray gun. Often these two tools are used simultaneously when performing paintwork. Initially, the surface is cleaned and then painted. Moreover, this applies not only to car bodies, but also to various structures on the farm, for example, gates, fences, poles and others.

Types of sandblasting guns for compressor

Today you can buy a nozzle for a sandblasting compressor quite inexpensively, which is due to the low quality of such a tool. However, for periodic use of such attachments in the household, they are quite sufficient. Professionals prefer to work with expensive sandblasting guns, which not only have high performance, but are also reliable.

Sandblasting equipment is divided into two types according to the principle of operation:

Pressure type - abrasive material is supplied from the reservoir through a hose to the nozzle of the gun, and flies out through the nozzle onto the surface to be treated. The principle of operation of the pressure system is based on the fact that compressed air is supplied into a sealed container with sand, which pushes the fine mixture through a special channel into the chamber. The finely dispersed consistency supplied under constant pressure is picked up by a stream of compressed air and transported to the nozzle, from where it flies to the surface. These types of equipment are classified as professional, and they are often used for processing ships, bridges, etc.
Ejector type (not to be confused with injection ones) - the operating principle is based on creating a pressure difference, from which the effect of suction of a finely dispersed consistency occurs. Sand and air are mixed in a special gun chamber and released through a nozzle

The operating principle of both devices is shown schematically in the photo above. The most popular are ejector-type devices, which are used not only by specialists in car services, but also by home craftsmen.

It is important to note that sandblasting guns differ in the type of location of the container with the abrasive substance.

With a tank - the container is a component of the gun, which makes the tool similar to a spray gun. Nozzles with a tank have one significant drawback - the need to frequently interrupt to fill the container with sand. That is why such devices are used exclusively for processing small-sized surfaces. These attachments are also used for engraving on glass and other structures.
With a hose - used when processing large surfaces. The material is supplied from a separate container, which can have different sizes, which is a great advantage, allowing work to continue until the sand is completely used up. Sand is supplied from the container to the gun using a special connecting hose. The nozzle without a tank for connecting the hose is similar to a conventional blow gun

Before choosing a sandblasting gun, you need to decide what size surfaces you plan to process. Often, tools with built-in capacity are enough for home use.

What are the advantages and disadvantages of a sandblasting gun?

Each tool has not only advantages, but also disadvantages. The situation is similar with sandblasting nozzles for a compressor. Their advantages include:

Fast and effective processing of various types of surfaces - metal, plastic, wood, glass
Ability to access hard-to-reach places, which is often impossible to do manually or with power tools
The ability to independently manufacture nozzles. Many home craftsmen make sandblasting guns with their own hands from improvised materials.
Large selection of nozzles, differing in external design, as well as the name of the manufacturer
High productivity, which has a positive effect on saving time

With the advent of sandblasting guns for compressors, they have gained great popularity. However, if you are not familiar with this device, then do not rush to buy it until you know all the negative aspects:

The service life directly depends on the quality of the tool, and the higher this indicator, the correspondingly more expensive the nozzle will be. Cheap models have a short service life
Noisy operation
The need not only to use high-quality nozzles, but also to periodically replace them when worn out
Loss of abrasive material during operation

Another drawback that can be identified is the need for additional surface cleaning and sand removal. However, such manipulations must be performed after any type of processing.

Operating principle of the nozzle

Making such a nozzle with your own hands is not so difficult, the main thing is to choose high-quality materials for this. The operating principle here is the same as the nozzles in a full-fledged sandblasting machine.

Sandblasting operation diagram

It should be noted that such a product cannot be considered as complete. Rather, it is a lightweight option for treating surfaces with water.

Here you should pay attention to one very important point - it is better to use distilled water. This is due to the fact that the metal in this case will not corrode.

Please note that the sand when using such a nozzle on a Karcher must be of a very fine fraction and supplied together with water.

The operating procedure in this case is as follows:

when you press the gun, water passes past the intake hose, thereby creating a vacuum;
the vacuum sucks in the sand, mixing it with water, thereby starting the process.

Scheme of operation of a water-abrasive nozzle
It is worth noting that using only such a scheme (without additions in the form of dispensers and taps) is impractical. On average, cleaning a surface with a diameter of 70-80 cm can take up to 30 kg. Therefore, the principle of operation is good and does not require additions.

Sandblasting gun with recovery or how to do dust-free processing

Tool manufacturers are constantly improving their creations, which is exactly what happened with compressor attachments - sandblasting guns. The modernization of these devices is that they are additionally equipped with special dust collectors. Such nozzles are called sandblasting guns with abrasive recirculation. These devices with an abrasive recycling system allow sandblasting to be carried out without waste and with minimal sand loss.

Unlike conventional sandblasting nozzles, guns with abrasive recirculation are equipped with a nozzle made of rubber material. Such nozzles not only ensure a long service life, but also allow dust-free processing. The operating principle of a dust-free sandblasting gun with recirculation is as follows:

The sand released from the nozzle with air hits the surface to be treated, cleaning it
After this, the sand is not sprayed, but returns to the nozzle, but accumulates in a special bag
Once the bag is filled with sand, it can be reused

Loss of abrasive material does not exceed 5%, which is very convenient and economical. Closed cycle sandblasting nozzles are also produced based on the recuperation gun. A certain portion of sand is transported in a circle, performing useful work in the form of cleaning the surface. To use the nozzle for a sandblasting compressor with recovery, you should perform the following manipulations:

Place a nozzle of the appropriate shape on the gun - square, triangular, round, etc. It all depends on the shape of the area being treated
Bring the gun directly to the area to be sandblasted and apply it closely
Press the trigger and perform the appropriate manipulations to clean the surface
The length of time the trigger is held in one place depends on the complexity of the area being treated.

Manufacturers are silent about the fact that pistols with recuperation also have their drawbacks. The main disadvantage is that not only sand accumulates in the bag, but also particles of rust, paint, etc. That is why the sand that accumulates in the bag must be sieved regularly to prevent clogging of the nozzle and channels when reusing abrasives. The video below shows the process of how to work with a sandblasting gun with recovery.

How does a sandblasting nozzle work?

The operating principle of any sandblasting installation is that abrasive material from a special hopper enters the nozzle under the influence of an air flow supplied under high pressure. In serial installations, a separate compressor is used to create such pressure, due to which a significant amount of kinetic energy is imparted to the sand stream emerging from the nozzle. In the case of a Karcher washing machine, the pneumatic equipment built into it will be used for these purposes. As a nozzle for such equipment, you can use a serial gun, specially designed for equipping pneumatic treatment plants, but in order not to spend money on such a device, you can easily make it yourself.

In order for your homemade sandblasting nozzle, which you will use for installation on a Karcher device, to be effective and not malfunction, you must use high-quality materials for its manufacture.

Operating principle of wet sandblasting rust cleaning machine

Of course, equipment assembled in this way can, with great stretch, be considered as a full-fledged sandblaster, but it is quite suitable for cleaning various surfaces with a stream of water mixed with sand. When using such a sandblasting device, it is very important to adhere to two recommendations:

It is better to use distilled water as the working fluid, which will avoid corrosion of the metal elements of the nozzle;
the sand that will be used as an abrasive must be of a very fine fraction and carefully sifted.

Diagram of a sandblasting nozzle (click to enlarge)

A self-assembled sandblasting machine, the basic elements of which are a Karcher mini-washer and a homemade nozzle, will work according to the following scheme.

When you press the start button on the nozzle gun, water under high pressure created by the compressor flows past the opening of the intake hose, the other end of which is placed in a hopper with sand. This creates a vacuum in the intake hose.
Under the influence of vacuum, sand is sucked from the hopper into the main hose, where it is mixed with the water flow.

In order to minimize sand consumption and bring this parameter to a value of 30 kg of abrasive for processing a surface area with a diameter of 70–80 cm, the design of this equipment must be supplemented with taps and dispensers.

Homemade mixer from water taps and tees

How to use a sandblasting gun - basic recommendations

If you understand the principle of sandblasting, then it will not be difficult to master the tactics of sandblasting the surface in order to remove corrosion, paint, varnish and other contaminants. Before starting work, you should prepare the workplace and put on protective clothing. Let’s consider in detail what the process of preparing for sandblasting is:

Selecting a work location. It is best to carry out work indoors, since sand scatters over large areas, which complicates its assembly and is also harmful to the environment, depending on the type of abrasive used. Work can be carried out outdoors if it is necessary to remove rust or paint from a gate or fence, as well as other large surfaces
Lay oilcloth or linoleum on the floor. This is necessary so that after finishing the work it is easy to collect the sand and use it again
Provide good lighting in the room. This is very important, since working in a poorly lit room will result in untreated areas. During work, visibility is reduced due to dust clouds
Remove all unnecessary items that do not need processing. If the flow from the gun gets onto the surface, it will damage it.

It is important to choose the necessary protective equipment when carrying out work:

Special safety glasses. The following requirements apply to glasses: they must fit snugly to the body and be made of glass. Plastic glass will reduce visibility if sand gets on it.
Respirator - and you need to use not a simple mask, but a full-fledged respirator, especially if the work is carried out indoors
Thick clothing and hat

After this, you can begin sandblasting work. There are no difficulties with their implementation, since the essence is to remove the surface coating from the workpiece. Depending on the type of material being processed, you need to adjust the pressure and sand supply, and then begin processing. The gun must be held at an angle of 45 degrees to the surface being treated, since it is at this angle that the effect of particle separation from the surface is maximum.

This is interesting!
The duration of holding the tool in one area depends on the thickness of the layer being removed from the surface, and is established experimentally. After finishing the work, the surface must be degreased, and you can begin painting work.

Choosing sand for a sandblasting gun

An important question when treating surfaces with sandblasting guns is which sand to choose. Many inexperienced craftsmen use ordinary street sand for such purposes, which ultimately leads to rapid failure of the equipment. In addition to the fact that street sand contributes to the disabling of the nozzle, it can also damage the surfaces being treated. When choosing consumables for sandblasting guns, it is important to consider the following factors:

Fraction size - depends on criteria such as nozzle diameter, compressor pressure and the desired result
Material hardness - a 10-point scale is used for evaluation. It is not always necessary to choose sand of high hardness, as it depends on the type of material of the surface being treated
Abrasive ability - this parameter characterizes the time during which the consumable material will cope with the task. The higher the abrasive ability, the greater the amount of work that can be completed in a short period of time.
Recovery ability - this parameter is important to consider when using a special tool with a sand collector

Four types of sand are used for sandblasting:

Quartz - characterized by low cost and availability. The material is characterized by a large amount in its composition, which has a positive effect on the quality of processing. The disadvantage of quartz sand for sandblasting is that it is harmful to health, so work must be carried out strictly using protective equipment, and there should be no people or animals nearby.
Corundum is a material that is excellent for working with high-strength coating materials. Corundum sand is capable of recovery, and it is used in a variety of fields
Garnet is an abrasive material that is environmentally friendly, but it is used on equipment that operates on high-pressure water.
Cooper slag has a high density of abrasive substances, and at the same time it can be used for re-processing. The composition contains quartz particles that are harmful to human health, so it is important to wear protective clothing when working.

When choosing sand, you also need to consider what type of sandblasting equipment is used. These can be closed or open type devices.

This is interesting!
Only dry sand should be used for sandblasting.

Which compressor to use for a sandblasting gun

Before using a sandblasting gun, you need to pay attention to the choice of compressor. It should be noted right away that a low-performance compressor is not suitable for sandblasting work. The minimum output pressure must be at least 5 atmospheres. The productivity should be at least 300-400 liters per minute, and ideally 500 liters per minute. When choosing the main device, it is important to consider the following parameters:

Pressure
Compressed air consumption level
Consumption of abrasives
Speed of work
Compressor type

We decide on these parameters, on the basis of which the compressor is selected. Below is a table from which you can roughly calculate the consumption of abrasive substances depending on the diameter of the hose for sand and air, as well as the size of the nozzle and the pressure of the compressor. The values given in the table are approximate and allow you to navigate depending on the volume of planned work.

An important parameter of a compressor for a sandblasting nozzle is pressure. This parameter affects not only the speed of work, but also its quality. If the nozzle diameter of the nozzle is 6.5 mm, then a compressor with a minimum pressure of 4.2 atmospheres is suitable. For nozzles over 8 mm, equipment with pressure ratings of 6.6 atmospheres or more is required.

This is interesting!
It is necessary to take into account the fact that up to 15% -20% of pressure is lost in the connecting air hose.
Another important factor is the type of compressor. They come in piston and screw types. Piston compressors are more popular, but their disadvantage is that the compressed air contains particles of an oil mixture. This causes the sand to become wet, thereby reducing productivity and also reducing service life. To eliminate air humidification, you need to use special dehumidifiers.

If it is necessary to perform a large volume of work while maintaining high quality, then it is recommended to use screw compressors. They are not only reliable, but also efficient. When choosing a sandblasting gun, it is important to consider the suitability of the tool for the type and volume of work planned.

Recommendations for safe use of the nozzle

When using a homemade nozzle on a Karcher machine for sandblasting, you should adhere to safety requirements when working with such equipment. When using a Karcher washing machine, only water is supplied from its nozzle, which is not capable of harming the health of the operator. When using a sandblasting nozzle, in addition to high-pressure water, sand is also supplied from the tip of such a device, which can seriously injure the person operating such equipment. That is why when using such an attachment it is important to strictly adhere to the following safety rules:

Processing should only be carried out in special closed-type clothing;
shoes used for treatment using such a device must also be closed;
All sandblasting work is best done outdoors.

Protective equipment when working with a sandblasting machine

Considering the fact that when using a Karcher apparatus and a homemade sandblasting nozzle, processing is carried out using a mixture of sand and water, it is not at all necessary to use face and respiratory protection in such cases.

When starting to make a sandblasting nozzle with your own hands, you should keep in mind that it will work effectively only if the compressor of your Karcher mini washer is capable of producing a stream of water under a sufficiently high pressure.

More on the topic: > Do-it-yourself sandblasting: drawings, videos, manufacturing instructions > Homemade sandblasting gun > Do-it-yourself sandblasting chamber: drawings, components, assembly