The angle grinder is a convenient and versatile tool used both in large-scale productions and in home workshops. This article will allow the reader to get an idea about the features of the LBM device, the principle of operation and technical characteristics. Processing virtually any material at home is not difficult when using modern power tools. Angle grinders (angle grinders) of different models are freely sold in specialized stores and are available to a wide range of users. How to choose a grinder that would satisfy the specific requirements of the client? To answer this question, let’s try to figure out what the instrument is and what its parameters are.
The term "Bulgarian" to refer to this construction tool appeared in the Soviet Union in the early 70s of the last century. Angular grinders got this name thanks to the place of origin, their production was established at the Eltos-Bulgark plant in Plovdiv. LBM was designed by Ackermann + Schmitt (FLEX-Elektrowerkzeuge GmbH) in Steinheim an der Mur in 1954. Angle grinder quickly gained popularity among specialists, one of the main success factors of the tool was its versatility.
The use of special equipment allows using the grinder to carry out cutting and grinding operations on a wide range of various materials:
Ferrous and non-ferrous metals, as well as their alloys.
Natural and artificial stone.
Ceramic and silicate brick.
Concrete and products from it.
All types of ceramic facing tiles.
It is not recommended to use the grinder for cutting glass and wood, because of the high linear velocity at the touch point of the snap-in, heating occurs and possible ignition. In recent years, circular saws have been manufactured for working on wood with taps made from special refractory alloys. This equipment should be used very carefully and to prevent its overheating. The above list of materials defines the main areas of application of angle grinders.
This power tool is widely used:
A lot of LBM in the hands of the population, the owners of households are actively using them to perform work on the farm. With its help cutting and polishing of the materials mentioned above is carried out. This power tool, in particular, is the processing of welding seams and descaling. The operation does not take much time and allows you to do without excessive shock loads on the fresh joint.
The design of angle grinders is characterized by a relatively simple and technological design, which made it possible to organize their production in many enterprises.
The angle grinder consists of the following parts:
The body, which is made of reinforced polymers. Such materials are characterized by high strength, resistance to wear and the environment. On the outer surface is a button on the tool with a latch. Some models have windows, closed with hatches, to replace the drive brushes.
An electric motor powered by a household network or batteries. At LBM used drives that can provide high revolutions of the shaft. To cool the windings and other parts in front of the axle mounted fan.
A single-stage angle reducer in a separate housing, made primarily of magnesium or aluminum alloys. Consists of bevel gears, the shafts of which are mounted on ball or sliding bearings. The interaction of parts with each other in the gearbox is provided by a housing that is filled with grease.
A spindle consisting of a shaft with a metric thread, a thick-walled washer, and a nut for fixing the cutting disc or other tooling. On the gearbox housing, usually on the opposite side, there is a button locking the shaft in a fixed position. This is necessary for the dismantling and installation of new equipment.
The removable handle is threaded and can be screwed into the gearbox housing in one of the selected positions. This is done for the convenience of holding power tools in the process of performing various types of work.
The protective casing closes a part of the cutting disc and does not allow a sheaf of sparks that form during operation to fly apart in all directions. The device protects the worker and surrounding objects from wear products of equipment and fragments of material formed during its processing.
The angle grinder is supplied to the consumer complete with the user's manual and a special key for fastening the tooling. The latter is a steel strip with two pins that exactly coincide with the holes of the fixing nut. In some cases, the manufacturer adds spare carbon brushes to the delivery set.
The angle grinder is driven by an electric motor that is activated by pressing the latching button or the switch. Power is supplied from the network, as well as from a built-in or removable battery. Mainly the tool is equipped with collector electric motors, in which the stator winding has a large inductive resistance. This circumstance can significantly reduce operating currents.
When spinning, the motor shaft rotates the pinion gear in the gearbox, which drives the driven gear, and thus transmits the force to the spindle. The body of the mechanism is made of magnesium or aluminum alloys to improve heat transfer. The gearing between gears is of two types: spur gear and helical gear (conical Glisson system). The second option is preferable because it provides greater reliability and helps reduce noise.
On more expensive and more sophisticated models, a release clutch is used that is installed between the engine and gearbox. The main function of this node is to prevent the return stroke when the disk suddenly stops due to jamming. This allows you to protect the operator from possible injury and components of the grinder from damage. On these angle grinders, you can press the spindle lock button until it stops completely.
The choice of the constructive scheme in which the plane of rotation of the cutting disc or brush parallel to the tool axis is explained quite simply. When working angle grinder there is a significant torque, seeking to move the tool to the side. This effort is easily compensated by the operator, due to the optimal positioning of the arms along and perpendicular to the axis.
Given the significant difference in parameters between different models of angle grinders, the question arises, which is better to buy a grinder for home or work ? It should be determined: to perform, what operations it is needed, and what are the volumes of the proposed work.
One of the main parameters of angle grinders is the linear speed of rotation of the circle, which depends on the diameter of the circle. The optimal value for this indicator is 80 m / s, a significant deviation of the speed of rotation upwards will lead to the destruction of the circle. Slower speed causes fast wear on the disc. There are five types of angle grinders that differ in the size of the cutting wheels used.
The dependence of the spindle speed on the diameter of the working disk is as follows:
115 mm - 13290 rpm
125 mm - 12230 rpm
150 mm - 10190 rpm
180 mm - 8490 rpm
230 mm - 6650 rpm
Data on the allowable rotational speeds of the cutting wheel for each specific model must be indicated on a special plate that is attached to the body. The magnitude of the torque at the same time should be sufficient to overcome the resulting friction force and maintain the required cutting speed. This characteristic is determined by the rated power of the electric motor of the grinder.
Bulgarian nominal power ranges from 650 to 2700 W, and depends on the diameter of the disc used. Correspondingly, angle grinders designed for large diameter discs have more powerful drives. With such parameters, the electric motor provides the force at the cutting edge of the circle sufficient for effective impact on the material being processed.
For normal operation it is necessary that the power consumption of angle grinders with a disk diameter of 125 mm is at least 750 watts. Moreover, the larger the diameter of the allowable tooling, the more powerful the engine must be. So in models with a tooling diameter of 230 mm, which are designed for intensive use on construction sites, the power consumption of the engine must be at least 2200 watts.
Be sure to decide what diameter of equipment will be sufficient for your needs. Remember that you cannot use circles with a diameter greater than the allowable one.Of course, you can do this by removing the protective cover, but such manipulations are prohibited, as they can cause injury to the operator. It is especially dangerous to use angle grinders without a protective casing when working with metal discs with hard-melting taps, which when scattering can cause significant harm to health or even death. If you have such a desire, just find on the Internet photos of people who were injured while neglecting safety when working with angle grinders and this desire will disappear forever.
The diameter of the snap is deeply associated with such a parameter as the depth of cut. This moment is especially important if you are going to cut curbs and other materials having a greater thickness with the help of LBM. The cutting depth of the model with a disk diameter of 125 mm is only 30 mm - 35 mm, depending on the model. That's because to immerse the circle in the material completely, the dimensions of the gearbox will not allow.
Of course, you can cut the curb stone by making cuts from two sides. But to make such a cut with quality is more difficult, and it will take more time. Therefore, if you have to constantly cut such materials, then you should look in the direction of the "Bulgarians" with a maximum disc diameter of 230 mm.
angle grinders with a small working circle are unsuitable for cutting superhard materials, and large models are inconvenient for polishing the car body.
To determine which grinder to choose for the home and which for intensive work, you need to proceed from its technical indicators. The entire power tool, including the angle grinder, is divided into household and professional, depending on the time of continuous operation. LBM household models are intended for occasional use of 30 - 40 minutes per day. Professional models are designed for internal use of the tool throughout the day or work shift. Professional angle grinders have enhanced protection from dust, noise and a number of systems that are designed to ensure the comfort and safety of the operator.
If the angle grinder is designed for small household tasks, then you should pay attention to models with a disc diameter of 115 mm, 125 mm or 150 mm. The most common model for the home is the angle grinder with a disk diameter of 125 mm. To understand how to choose a grinder for the home, it is necessary to outline the range of tasks and the list of processed materials. Obviously, the acquisition of expensive professional tools in this case is unjustified.
With regard to professional models, the undoubted leader here is LBM with a diameter of 230 mm discs. When choosing such a model is worth paying attention to the diameter of the engine. The larger the diameter of the engine, the more torque can be developed by the angle grinder, and this is very important in exhausting operation. Therefore, if you choose between two approximately equal angle grinders, give preference to the one that has a larger engine diameter and only secondarily look at power. Some manufacturers themselves indicate the torque in the passport data of the tool, but many ignore this parameter.
Angle Grinders are widespread due to their convenience, versatility and reliability. The design of the power tool provides a number of systems that are designed to ensure high performance and safety of work with the tool. The functionality of each model is determined by the manufacturer at the design stage, the list of additional options affects the cost. That is why, then we will consider additional systems that ensure the operation of the LBM and determine how important their presence is for the effective and safe use of the tool.
When the electric motor is switched on, an abrupt increase in the load on the motor winding occurs by 6-8 times, which may cause its damage or the protection to trip. This also results in a shock moment, which is transmitted through the shaft to the gearbox and spindle. The inrush current limiting system is an electronic circuit that provides a smooth increase in speed. The principle of operation of this system is to gradually increase the voltage on the windings for a specified time. The use of an angle grinder at the same time becomes safe, increases the resource of the electric motor and gearbox.
The lack of impact at start contributes to higher cutting accuracy and eliminates the possibility of scoring during grinding.
When the cutting disc touches the surface to be treated, friction occurs, which increases the load on the engine and reduces the speed.The system of maintaining a constant number of revolutions of the disk compensates for the resistance and ensures the preservation of cutting speed. Stabilization of the spindle speed is carried out through the use of a constant electronic circuit.
There are two ways to maintain the speed in angle grinders operating under load: by current or by frequency of rotation of the spindle. In the first case, a consumed current sensor is used, which captures its value and as the circuit increases, the voltage on the windings increases.
Speed control implies the use of a total station sensor that monitors the rotation of the angle grinder. With a decrease in this indicator, the electronic circuit increases the voltage and, as a result, ensures the optimum rotation speed of the tooling. The choice of methods for maintaining a constant rotational speed occurs at the design stage and takes into account the positive and negative sides of each method.
Not all models are equipped with such a system; one can say that its presence is desirable, but not necessary.
During construction, it is possible that a power outage occurs for a variety of reasons. The system of blocking the re-activation of the angle grinder eliminates the possibility of inadvertently starting the engine. When the grinder suddenly stops, the worker most often simply lays the tool aside without checking the position of the switch.
Sudden renewal of power supply in this case is fraught with injuries for the contractor or damage to valuable property. For Bulgarians equipped with such a system, the restart occurs only after the starting device is turned off and pressed again. The user at the same time will need to take the tool in hand, which means that his actions will be meaningful and controlled.
The existence of such a system is very important and necessary.
During the use of angle grinders, especially with the large-diameter snap-on, wear of the disks or brushes is uneven. This leads to an imbalance, which manifests itself in the form of vibration, which does not contribute to the accuracy of the operation. The runout adversely affects the condition of the bearings and reduces the life of the electric motor.
The automatic disk balancing system compensates for the uneven mass distribution of the rotating tooling. Different technical solutions are used to stabilize the instrument, mainly special bearing designs with a smaller number of balls. This system increases the cost of products and is usually used on professional models with large diameter discs.
If you choose a tool for intensive use on the construction site, it is best to give preference to models equipped with this system.
In the process of using the angle grinder, the load on the electric drive is non-constant and in certain periods can significantly exceed the calculated one. To protect the motor from overloads, “Bulgarians” are equipped with special systems that forcibly stop the flow of current. In this case, the tool simply stops working and for renewal it is necessary to turn it off first and then on again.
There are two ways to protect angle grinders from overheating: by current or by temperature. In the first variant, the shutdown occurs when the limit parameters are exceeded, which are fixed by the electronic module. In another design, a thermal sensor is installed on the engine, which interrupts the power circuit when the parameter goes beyond the set values.
The system provides the longest tool life, but does not affect the quality and safety of the work.
Significant amounts of dust are generated during grinding of surfaces or cutting materials using angle grinders. It enters the body with air flow and causes increased wear, the bearings, the brush unit and the outer surfaces of the rotor and stator are most vulnerable. Metal particles formed during cutting may cause a short circuit between windings.
The protection system of the angle grinder provides for the use of the following design and technological solutions:
Dust protection systems greatly increase the angle grinder life and make it safe during operation, preventing the occurrence of a short circuit.
A sudden snap-in of a snap-in leads to a torque that is directed at the turning of the angle grinder. At the same time, considerable efforts arise, and it is unrealistic to keep the instrument in the hands, and this is already fraught with injuries to the upper limbs and other parts of the body.
The anti-kickback system during jamming of the equipment prevents this from occurring. It is implemented in two ways: mechanical or using electronics. In the first embodiment, various couplings are used, which operate with a sharp increase in the resistance to rotation of the shaft. The second method is based on the constant monitoring of current values, when a certain value is exceeded, the power is turned off.
Different manufacturers have their own experience in order to implement such protection, its presence is extremely important on professional models with a large circle diameter.
The spindle speed is adjusted using the dial on the tool body. On cheap models, this adjustment may be absent altogether. But as practice shows, when performing certain works, its presence is very important and allows for better cutting or grinding. For example, performing the grinding of plastic and various paints, with too intensive rotation of the snap-on, the treated surface may burn.
In the classical form, the angle grinders have two main and additional handles that are mounted on the gearbox. But in this regard, the tool has many features that should be considered separately.
Distinguish angle grinders with one and two handles. It should be noted right away that this does not mean at all that when working you will hold the tool with one hand. Just in the one-hand angle grinder the second hand is located on the case. Single-handed produced angle grinders with a disc diameter of 115 mm and 125 mm. The main advantage of single-handed angle grinders is their small length, which makes it possible to use the tool in hard-to-reach places, for example, during body work. The main drawback is that they are harder to keep at work. Therefore, a tool for a snap of large diameter is only with two handles. In any case, holding the tool with two handles is much more convenient and safe than holding it with one handle and body. Before purchasing an instrument, it is worth holding it in your hands to decide which option is preferable for you.
The gearbox housing has at least 2 holes for attaching an additional handle. The best is the presence of 3 holes - two on the sides and one on top. This is quite enough for the convenience of performing almost any work. Some manufacturers make more than 3 positions for fixing the handle, do you need such functionality?
Attachment points for the additional handle.
The main handle can be rotated relative to the housing axis. Most often there are 3 positions - neutral and 90 0 in both directions. This allows you to choose the necessary coverage for a better and more convenient execution of work.
Angles of rotation of the main angle grinder.
When operating with an angle grinder, a vibration occurs, which is dampened using a special vibration damping handle. Equipped with such a pen, not all models. As a rule, it is more expensive or professional angle grinders. It may seem that this is not such an important detail, but based on experience, I can say that the work of angle grinders with an anti-vibration handle is much softer and more comfortable.Therefore, it is better if the tool is equipped with such a handle.
Autonomous Bulgarians appeared on the power tool market relatively recently. In such constructions, lithium-ion batteries of large capacity are used, capable of ensuring the operation of the angle grinder for a short period of time. Such technical solutions are currently applicable only to grinders with a small disc diameter of 115 and 125 mm.
Using battery-operated angle grinders at home with a power supply is not the best solution:
The only advantage of such a tool is the possibility of using it in places where there is no power supply. For modern homeownership, this is not a problem, which means that the choice of battery charger is inappropriate. Buy them in case of emergency, when there is no opportunity to work from the power source. The main parameter that is worth paying attention to when choosing a battery angle grinder is the capacity of the battery. Remember that angle grinders consume quite a lot of energy, so the greater the battery capacity, the more time you can work with the instrument on one charge. All other selection criteria are the same for both battery and network angle grinders.
Angle grinders are extremely versatile due to the use of a wide range of different accessories. The tooling market is very large and can satisfy both the home craftsman and the professional. But there may be difficulties associated with the selection of the size of the snap. As mentioned earlier, the most common dimensions are angle grinders at 125 mm and 230 mm. It is possible to buy equipment for such tool in any hardware store. But with equipment for angle grinders 150 mm and 180 mm problems may arise, since this type of tool is not very common. All manufactured equipment is designed for cutting or grinding a certain type of material or materials and it is not allowed to use it on other materials. This is the first thing to pay attention to when choosing it.
The selection of equipment is carried out taking into account the nature of the work performed and the parameters of the angle grinder. It is not allowed to use equipment, the diameter of which exceeds the maximum allowable diameter of a circle for this model of angle grinders.
The nomenclature of equipment includes the following items:
Designed for cutting various materials. When using this type of equipment should strictly maintain the angle between the tool and the treated surface. Cutting discs are used only for well-fixed parts. They are abrasive and diamond.
Abrasive cutting discs.
Most often such circles are used for cutting metal, stone and concrete. The specification of such circles is marked on their label and denoted by letters and numbers, for example: A 24 S, where:
All these parameters must be selected under the material being processed. Otherwise, the disc may either burn or grind out too quickly. The main rule - the harder the material being processed, the softer the bond should be.
Diamond cutting discs.
Diamond cutting wheels of different types are narrowly specialized and designed to be used only for working with certain materials:
By the form of the cutting edge they are divided into segment, solid and "turbo":
Grinding disc wheels.
Cup type grinding wheels.
Flap disc grinding wheel.
Flap disc grinding wheel.
Cup brush with brass bristles.
Disk brush with steel bristles.
When working with a grinder, you must remember that the rotational speed of the disk is from 6,650 to 13,290 rev / min and its destruction accompanied by scattering fragments. Therefore, it is strictly forbidden to remove the protective cover, and the operator must use special glasses. When working with power tools, the following security measures should be observed:
Neglecting simple safety rules can lead to injuries and even death due to damage to vital organs by disk shards.
In order to understand how to choose a grinder - an angle grinder for the house, you need to know what exactly the tool is needed for, and how often it will be used. If we take into account the average needs of the homeowner and the list of the work being done, we can recommend the angle grinder with a circle diameter of 125 mm from a well-known manufacturer. Usually such a unit is enough to perform most of the work. In general, this tool is not very expensive and the market is oversaturated with supply. Therefore, you just have to determine your needs and by comparing several suitable models to make your choice.