What is an angle grinder intended for?
An angle grinder was invented specifically for grinding, therefore, unlike a sawing tool, it works at a very high speed. The material is cut by grinding it. When cutting wood or plywood with a metal disc, high-speed friction leads to smoldering or even combustion of the workpiece. The plastic or soft metal under such a disk will simply melt. Soft materials can only be processed with a grinder when using special discs.
Cutting profiled sheet using an angle grinder using an abrasive cutting wheel
For cutting stone, brick and tile, discs coated with diamond chips and several cooling slots along the edge are used. The use of circular saw blades, as well as Chinese saw blades with a “grinder” fit, is a gross violation of safety rules and is therefore strictly prohibited.
Contrary to popular belief, an angle grinder is not a universal tool, and trying to do all the work with it is wishful thinking. Seeing the desire of craftsmen to saw various materials with a grinder, BOSH has developed a universal carbide disc Multi Wheell 2608623013. This is an abrasive disc with slots for cooling, thanks to which it does not burn the material being cut. Please note that neither BOSH nor other reputable companies produce saw blades for angle grinders.
Universal carbide disc Multi Wheell from BOCH
When purchasing any blade, it is important to make sure that the speed (rpm) indicated on the label is not less than the spindle speed of your angle grinder. A disc designed for 8,000 rpm may shatter into pieces when operated at 10,000 rpm. This is especially important if the angle grinder does not have a speed control function.
Types of grinders (ushm)
There are a whole range of varieties and types of grinders. Some are better suited for certain conditions, while some can do more than just cut metal, and the technical characteristics can vary greatly. There are varieties that are strictly connected to a compressed air network, and there are mobile ones - battery-powered or motorized (options such as moto are not shown - they are too exotic). For the job, you can choose a powerful saw or even a long drill. The main types and types can be identified as follows.
Mini grinder
The small (mini) grinder is a small version with a light weight. Its distinctive features are work with a circle with a diameter of up to 125 mm and the absence of a side handle.
The main purpose is operations in confined spaces and hard-to-reach places. The low weight does not tire the hand, so working with the mini machine lasts longer and is more efficient.
Due to the low power (up to 1 kW), the number of revolutions is not significant, so the design does not have a gearbox. Thanks to this same feature, the vibration is weak, so the work is more accurate. This makes it easy to polish.
The functionality of the machine is enhanced by the fact that the body itself is a handle: by setting the button to permanent operation, you can very easily grind surfaces and simultaneously hold or perform related operations. Due to its small size, it is convenient to perform gating at a considerable height.
Big grinder
The large grinder is a regular version with dimensions and power that allow you to work with a circle with a diameter of up to 230 mm and requires two-handed operation.
The most common type, equipped with a protective shield, a side handle (installation in several positions is possible) and requires removal of the working disk with a special key. The work is done in the largest circles. Therefore, depending on the manufacturer and configuration, there may be built-in speed control, and the gearbox is made of durable materials. Power is supplied from the general power supply, so when choosing, you should pay attention to the length of the cord. Regardless of power supply, cutting with water supply is possible. There are also vacuum cleaners for grinders.
Unlike the small one, it is often used as a wall chaser. High power when cutting allows you to quickly obtain a high-quality result - the grooves will be even. However, it should be borne in mind that the mass of the tool can be considerable, so it will not be easy to ditch at high altitudes. As for the diameter of the circle, with its large size, cutting the wall can stop in front of the inner corner near the floor.
When cutting rolled products with such a powerful machine, it is optimal to place the metal in a stand - on racks or in a miter box.
Wireless grinder
The wireless one is powered by a battery, so its dimensions and weight speak for themselves. Working with such a machine has maximum mobility and does not require meters of extension cord.
The working part is not fundamentally different from the usual one, but the rear part is significantly different: there are connectors for attaching and connecting the battery. The kit fits into a case.
There are also changes in the motor: power from the mains is suitable for an AC motor, and the battery motor is suitable for DC. The difference is in power; a DC motor produces less power for an angle grinder.
In this regard, the purpose of a cordless machine is the accuracy of the operation performed. It is most effective to accurately and quickly cut fairly durable materials - from granite to cast iron (even such small models are enough to cut a cast iron battery). Portability makes it best for car repairs.
Grinder straight
A straight angle grinder is different in appearance: the working body is a continuation of the body, usually there is no additional handle. The work can be done with one hand. The second hand is used to correct or hold material, or to stay in space under difficult conditions.
Its purpose is to work in hard-to-reach and miniature places and an extended list of operations. For this purpose, an extension cord or an adapter for an angle grinder is supplied in the kit or separately.
The design is convenient for polishing work. To treat the surface, you can use not only discs, but also cylindrical and conical nozzles of abrasive and petal types (to remove the height of the concrete floor in the corners), drills (this way you get a grinder-drill). Adapters are available for attachments. The end installation of the circle is convenient in its own way.
The number of revolutions per minute is up to 30,000 thousand. Usually a soft start system and overload protection are installed.
Ushm pneumatic
The operation of a pneumatic angle grinder is based on the supply of air under pressure to the working part. To do this, connect to the compressed air system - there is a special connector for this purpose.
The compressed air is started by pressing the trigger. After entering the internal cavity of the machine, the air spins the rotor, which in turn, through the gearbox, creates rotation of the working circles.
Like other options, the pneumatic angle grinder comes with a protective shield and an additional handle. Compared to others, it has a longer service life and quite high power. Such a tool can be used in a polluted environment. The housing is sealed and durable due to pressure work.
However, due to air escaping from the case, it is often impossible to work without dust. However, it is possible to install a dust removal system (as on other models). Polishing is often done to prevent too much dust. And the air suspension accelerates from the supply hose.
Brushless grinder
Like any other electrical device, an angle grinder includes such an element as brushes - removable sliding-type electrical contacts. The design of the brushes is developed, but quite unified (although each manufacturer produces their own).
As a mechanical element operating under dynamic conditions with constant friction, brushes often fail. The brushless motor is the next step in the development of electrical engineering. It requires less repair due to the absence of brushes, makes less noise and does not produce sparks. This allows us to consider this model more fireproof. A brushless angle grinder works quietly in very dusty air - it has no equal in repairs and construction. The question is how to grind a concrete floor (if it is not possible to install a dust extractor).
The price is a little more expensive than the classic model, but the advantages outweigh the cost of regularly replacing the brushes.
About the angle grinder speed controller
Some angle grinders are equipped with a speed controller. It can be useful when cutting relatively soft materials such as stone, tile or wood. When cutting metal, it is set to maximum. It is good if the regulator cannot be moved accidentally (for example, it is recessed into the body and turns tightly). True, there is a fly in the ointment in this barrel of honey.
Firstly, as the speed decreases, the engine cooling impeller also rotates more slowly, which leads to increased heating of the tool.
Secondly, when the speed controller fails, it does not burn out into an open circuit, but into a short circuit. This means that by setting a low speed, you can get an abrupt increase in speed right during operation, without being prepared for it. Of course, it is also possible for the regulator to burn out when the tool is idle, but this is no better: a burnt-out regulator set at low speed misleads the master, and again a wild jerk of the tool occurs, for which the master is not prepared. If at this moment there is a low-speed disk on the spindle, it may simply burst from excess speed. In other words, despite all the usefulness of the speed controller, its damage can lead to very sad consequences.
In general, it is better not to cut soft materials with a grinding machine, but to cut hard ones with great care and only with an abrasive disc. An angle grinder is a grinding machine, and the ability to cut by grinding is secondary. It’s the same as cutting with a router or milling with a drill: there is a technical possibility, but such a solution cannot be called optimal. Therefore, when planning to buy an angle grinder, think about what you are going to do with it and ask yourself whether it would be better to buy a jigsaw or a circular saw for these purposes?
However, let’s assume that you know exactly why you need an angle grinder. Manufacturers offer many options for angle grinders, classifying them in different classes, packaging them differently and charging different prices. Which car should you choose?
Principle of operation
No matter how different the Bulgarians may be in appearance, they operate on the same principle.
As soon as the start button is pressed, electric current is supplied to the motor and the rotor begins to move. From it, rotation goes to the rotor shaft gear. The latter, through the large gear of the gearbox, rotates the axis ninety degrees. The gear of the gearbox is fixed inside its housing. It is thanks to this that the gear, rotating, sets the cutting disc in motion.
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Existing classes of angle grinders
Like any other tool, angle grinders are divided into classes: household, professional and industrial (tools of the latter class are not considered here).
For a household tool, it has low power and minimal functionality. The gearboxes of such angle grinders are made of duralumin, and therefore are less resistant to wear than expensive steel ones. The motor windings of cheap tools are usually covered with a thin layer of low-quality varnish. If the permissible temperature threshold is exceeded, this varnish melts, which leads to a short circuit and irreparable damage to the motor. Household angle grinders are designed for occasional use.
Professional tools have higher power and endurance, and often have useful functions that are missing in household angle grinders. Such a tool costs more than a household one, but there is something to pay for. Typically, professional angle grinders include higher quality parts and an improved cooling system, which allows you to work longer without interruption. The delivery package may include useful accessories such as an anti-vibration handle or a quick-release flange.
Still, the master makes the final choice in favor of one class or another based on real needs. If a tool is needed occasionally and for minor work, then a household machine is quite enough. If you plan to work with the tool seriously, then it is better to overpay for a good thing. In general, it is better not to skimp on the quality of the tool.
If the budget is very limited, and buying a cheap angle grinder is the only acceptable option, you should strictly follow the operating mode specified in the documentation: work for 5 minutes - rest for 15 minutes.
Disc diameter and rotation speed
One of the most important selection criteria is the maximum disc diameter. Grinders for a 115 - 125 mm disc are considered small, for a 150 mm disc - medium, for a 180 - 230 mm disc - large. The spindle rotation speed is directly related to the maximum diameter of the disk and the power of the angle grinder.
Large grinders have a power of about 2500 W and a spindle speed of about 7000 rpm, and small ones have a power of 600 - 1100 W and a speed of 10000 - 11000 rpm. The reason for the difference in speed is dictated by the need to ensure a peripheral speed within 80 m/s for any disk diameter.
Rotation speed is a very important parameter that influences the choice of disks.
It is strictly forbidden to place low-speed discs on a high-speed tool!
A 230mm disc may not have enough strength to withstand excess speed. If installed on a 10,000 rpm machine, a 7,000 rpm disc will reach speeds it was not designed for, which could cause it to shatter into pieces and cause a lot of bloodshed.
It should be noted that medium-sized “grinders” are inferior in performance to large ones, and in terms of convenience - to small ones. It may make more sense to buy two angle grinders (large and small) than to buy one (medium).
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The second most important tool after a drill is an angle grinder (angle grinder), commonly known as an angle grinder. This name was assigned to the unit back in Soviet times, when Bulgaria was the first and only supplier of angle grinders. Today you can buy grinders from various manufacturers, both European, American and Japanese. The choice is so great that as soon as we come to a hardware store, we immediately face the question of how to choose an angle grinder - an angle grinder, and what parameters to pay attention to. After all, with the help of it we cut almost everything that needs to be cut. These are metal, brick, concrete, cement, ceramic tiles, plastic, wood, porcelain, stone, asphalt, glass. But this unit is designed not only for cutting, but also for grinding various surfaces. Therefore, when choosing, you need to determine which additional functionality or design features are really needed, and which you can do without.
- Main characteristics of angle grinders
- Grinder disc diameter
- Grinder power
- Disc rotation speed on an angle grinder
- Additional structural elements or features of grinders
- Ease of use
- Safety
- Additional options
Main characteristics of angle grinders
When you come to a construction supermarket, a specialized tool store, or just to the market to buy an angle grinder, the first question you will be asked is whether you need a professional tool or for yourself. Professional angle grinders are designed for daily use for several hours a day. To make the work of the master easier and to extend the life of the unit, it is equipped with enhanced dust protection, all kinds of electronics, design features that reduce noise levels, and adjustable disk rotation speed.
The grinder “for yourself” belongs to the category of a household tool for a home craftsman, who will use it occasionally, when suddenly something breaks or needs to be done, or no more than 30 - 40 minutes a day. Household angle grinders have less power and require working intermittently. For example, 15 – 20 minutes of work and 30 minutes of rest. During this time, the engine has time to cool down and the likelihood of failure is less.
When choosing an angle grinder for home repairs or professional work, you need to understand exactly what specific work it will be used for. Based on the needs, the diameter of the disk, its rotation speed and the power of the grinder are selected.
Grinder disc diameter
The diameter of the angle grinder disk is the main parameter that you need to focus on when choosing; the power of the unit and the rotation speed of the wheel are selected taking into account the diameter.
There are grinders for discs with a diameter of 115 mm, 125 mm, 150 mm, 180 mm, 230 mm. The simplest angle grinders with a disk diameter of 115 - 125 mm are household ones; they can be used for grinding various surfaces, removing rust and paint from parts, for polishing, as well as for cutting various metals and ceramic and granite tiles, the thickness of which does not exceed 50 mm. The main limitation when cutting is the thickness of the material. A small diameter disc will not cut a concrete curb or other massive element. But for home needs, a 125 mm grinder is more than enough.
230 angle grinder belongs to a professional tool, and the 180 mm one can also be included in the same category. Such powerful units are used for cutting massive concrete products, asphalt, stone, and brick. Enormous power, a heavy massive disk, and large vibrations make it pointless to use a grinder with a disk diameter of 230 mm for cutting thin corners, sheet iron, tiles, plastic, as well as for grinding and polishing surfaces. This is easier to do with a less powerful and weighty unit.
Grinder power
The range of power in angle grinders is very large: from 600 W to 2700 W. Grinders with a 115 mm disc come with 600 - 1000 W of power, more is simply pointless.
Grinders with a 125 mm disc have a power of 750 - 1500 W. As a rule, low-power units from the 125 mm series have a small number of additional functions and are not intended for long-term use. Grinders with a power of 1200 - 1500 W are usually stuffed with all sorts of useful functions and elements.
Grinders with a circle of 180 - 230 mm belong to multi-power units 1500 - 2700 W. To cut concrete, stone and other massive elements you will need an angle grinder with a power of 2000 W or more. But for cutting small parts, sheet metal, plastic, for grinding and polishing, an angle grinder with a power of 720 - 1000 W is suitable. If you buy an angle grinder for home repairs, but for complex work, then it is better to take a 125 mm angle grinder with a power of 1200 - 1500 W.
The more power an angle grinder has, the longer it can work under load. The power is selected taking into account the complexity and duration of the work, and the weight of the disk you are going to use. For example, if you plan to clean a weld seam with a 115 mm grinder, then you need to take a unit with a power of 1000 W or more. If you plan to use heavy 230 mm disks, which are not so easy to spin, then the power will need from 2000 W.
Disc rotation speed on an angle grinder
The rotation speed of the disk or spindle on which it is mounted indicates how many revolutions per minute it makes. The larger the drive is installed, the lower the speed required.
The rotation speed of the disk on an angle grinder ranges from 2800 rpm to 11000 rpm. Small circles 115 - 125 mm are used at a maximum speed of 10 - 11 thousand rpm. But for 180 mm wheels there is already a limit of 8500 rpm, and for 230 mm wheels – 6650 rpm. These restrictions are due to the fact that the linear speed of the cutting edge of the disk should not exceed 80 m/s, otherwise the disk may fly apart, injuring the master.
Important! It is better to purchase an angle grinder that has the ability to adjust the rotation speed of the disc depending on the size of the disc being used. Most often it is implemented using a special lever or regulator.
Let us remind you that the disk size indicated on the label is the maximum allowable. For example, a 150 mm grinder can accommodate 115, 125 and 150 mm discs.
Additional structural elements or features of grinders
Modern units are very different from the first models of angle grinders; they have become more reliable, versatile, durable and functional, with a wide range of capabilities and elements that make work easier. For ease of choice, we will divide the functionality of the grinder into 3 categories.
Ease of use
Ease of use includes not only those innovations that simplify working with an angle grinder, but also make it more durable, and the process itself smoother and more coordinated.
The anti-vibration handle is an extremely important element. Vibrations are very harmful to human health. If you work with an angle grinder for several hours a day, you can get an occupational disease. In addition, even during short-term operation, vibrations can weaken your hand grip, the grinder will jump out and there will be trouble. To reduce vibrations, vibration-absorbing handles are installed in professional tools, which absorb vibrations, making work less tiring and difficult. Almost any Bosch angle grinder over $175 can boast an anti-vibration handle.
The anti-vibration system is also designed to dampen vibrations, just like the anti-vibration handle. Its main task is to reduce vibrations to such an extent as to extend the ability to use the grinder without interruption. For example, if the norm is 26 minutes, then the anti-vibration system allows you to work for 42 minutes. Most often, this system is implemented using counterweights.
Protection from dust and noise . Protection from noise is important primarily for the master, since constant rumbling sounds can lead to temporary deafness. If the master works with an angle grinder every day, you can only sympathize with him or advise him to use earplugs or headphones. Directly in the angle grinder itself, helical gears (Glisson pair) are used to reduce noise; their engagement is more reliable and they operate quieter.
But dust protection is important to ensure the longevity of the tool. If dust settles on an idle unit, it does not cause any harm. If it gets into a mechanism that is spinning at breakneck speed, it performs a destructive function, since it is an abrasive material. First of all, you need to protect the engine. To do this, the winding is coated with special resins, which after hardening serve as armor. A slightly different method is a filtration system that releases dust particles back into the atmosphere. In addition to the engine, manufacturers also protect other elements. For example, the Makita angle grinder hides gears and bearings behind special labyrinths that slow down the dust jet.
The spindle lock is needed to make it easy to replace the disk. This feature is found in almost all modern models. By pressing the button the driven gear is locked. It’s just that this is implemented in different ways. Ideally, you can lock the spindle in any position, but this is extremely rare; most often you have to rotate the disk by hand until you catch the moment.
Important! You cannot press this button until the disk stops completely.
Although there are also exceptions to this rule, which are dictated by the mechanism itself. A striking example of this is the Metabo angle grinder. In it, the mechanism acts on the clutch connected to the driven gear, and not on the gear itself. Therefore, the button can be pressed immediately after turning off the angle grinder, i.e. on the run-out.
The disc is secured without a key using a special nut that comes with the grinder. The design of the nut itself is very interesting; it consists of several parts. When the nut is screwed onto the spindle and its bottom rests against the circle, then only the upper part of the nut rotates further, and the lower part presses the circle harder and harder. After prolonged use, such a nut self-tightens, and it is no longer possible to unscrew it with your fingers. You still have to use the keys. Although there are manufacturers who have successfully improved the clamping mechanism. For example, the DeWALT angle grinder boasts a nut that can be easily unscrewed even after long, hard work.
Adjustment of the protective cover without a key is carried out using special clamping mechanisms. A very important feature for those cases where it is necessary to frequently change the position of the casing. The clamp and lever, which can be tightened, allow you to fix the casing in any position. This method has a significant drawback - due to strong vibrations, the clamp can collapse, and the casing will rotate around its axis loose. There are also more advanced mechanisms, but they are found on expensive professional equipment.
A protective casing for an angle grinder is necessary for the convenience of the master during grinding work. It protects it from fragments of the material being processed, as well as in the event of destruction of the disk from its particles. The casing does not interfere with processing corners and edges; for this purpose it has a sliding section. To remove dust from the treated area, a vacuum cleaner can be connected to the protective casing.
Safety
In addition to the features that affect the convenience of working with an angle grinder, there are additional elements, functions and features that ensure safe operation for both the operator and the unit.
The number of handles - one or two, is a matter of convenience for each master. Most angle grinders with discs up to 150 mm are equipped with only one connected handle near the spindle itself. But this does not mean that the grinder can be held with one hand; this is strictly prohibited. The other hand must hold the motor housing. In heavier angle grinders, there is another handle behind the engine housing, which is like a continuation of the body, but at the same time more convenient to grip. What the second handle looks like can be clearly seen in the photo, which shows a Makita angle grinder.
Smooth start prevents the starting jerk of the disk and also protects the gears from excessive wear. All modern grinders are equipped with a similar feature: both household and professional. A smooth start is especially important if the angle grinder is of high power. It can be implemented in different ways. There are models in which the spindle picks up speed in a few seconds; for an impatient master, this risks the fact that he can load the unit before reaching maximum speed. In other models, the spindle picks up speed almost immediately, but there is no jerk at the start. You can check this only by turning on the angle grinder in the store.
Restart protection is necessary so that after a sudden shutdown and then switching on of the power, the angle grinder does not start working. Usually, if the power supply suddenly stops, we put the tool aside and go check what happened. If at this moment the supply is restored, the engine will start and the wheel will begin to rotate straight in the lying position. There is no need to explain how this could end. And so it will be necessary to first move the power lever to the “off” position, and then again to the “on” position in order to start the angle grinder.
Direct engine cooling allows all system elements to be cooled sequentially. It’s no secret that during operation the angle grinder heats up, especially the gearbox housing. The ventilation system and special lubricants do not completely solve the problem, although they are an effective help. How this is implemented is shown in the photo of a Bosch angle grinder. For rapid cooling, the gear housing is made of metal, most often aluminum or magnesium alloy. It cools faster and is stronger than plastic. And in some models, for example, in the Hitachi angle grinder, even the motor housing is completely cast from metal.
A starting current limiter is necessary to reduce the load on the network when the engine starts. This feature is relevant only for powerful models of angle grinders. “Soft start” smoothes out voltage surges in the network, thereby preventing overloads.
The safety clutch is necessary in order to prevent the destruction of the disk when jammed and to smooth out the return blow. This will protect the motor from overload. It is implemented in different ways: in some models it is a slip clutch, which reduces the load on the engine, in others it is a centrifugal clutch, and in others it is a completely different patented system, reminiscent of the clutch in a car gearbox, completely disconnecting the engine and the gearbox.
The emergency engine stop system when the disk is jammed is a more advanced safety system than the clutch and is found in more expensive professional models. The electronic stop system instantly shuts down the engine when a disc becomes jammed or jammed. The Bosch angle grinder boasts both an electronic engine stop system, Kick Back Stop, and restart protection.
An overvoltage fuse or thermal motor overload protection represents a whole range of measures. Most often, overload is recognized by the engine temperature. For example, when the temperature of the windings reaches 130 °C, the light comes on, when it rises to 160 °C, the speed decreases, and at 200 °C the grinder switches off completely. This protection system may irritate those who like to load the instrument heavily and for a long time.
Additional options
Angle grinders may also have additional options, features or elements that make the job easier or affect ease of use.
Electronic stabilization is necessary to maintain a certain speed under load. During operation under load, the speed begins to fall, and the current strength, on the contrary, increases, so that the efficiency of the unit does not fall, the electronics connects an additional reserve, again increasing the speed. Remember that you should not overload the tool. Do not press it if you see that the disc may jam.
The rotation speed of the disk is adjusted using a wheel on the body of the angle grinder. As we already wrote, it is adjustable depending on the diameter of the disk used. Please note that it is easier to damage the tool at low speeds than at high speeds. Although you won’t be able to do without low speeds if you want, for example, to sand plastic or remove paintwork. Please note that not all economy class models are equipped with this function. For example, the Interskol angle grinder has an adjustment wheel, starting with units costing from 70 USD.
The disc brake reduces the run-down time to 3 seconds. This is a help for the impatient. It can be implemented in different ways. For example, in Metabo angle grinders it is similar to a regular brake in a car and operates on the principle of friction. Bosch angle grinders have a more complex electronic system that works on the principle of polarity reversal. But keep in mind that the second method is only possible if the unit is connected to the mains. When the power is turned off, the disk stops according to the standard scheme.
Automatic disk balancing is very rare, but it makes the job more enjoyable. A special clutch, in which the balls are immersed in oil and are grouped depending on the displacement of the center of gravity, significantly reduces the vibration of the disc. This allows you to slow down the wear of the disk itself and reduce vibration during operation.
The removable network cable is convenient in all respects. Firstly, you don’t have to think about what and how to wrap it around in order to hide it or move it to another place. Secondly, in case of damage, you can simply get a spare tire or buy a new one. In all respects, the detachable cable makes it easy to transport the instrument. But it is found only in some models of Protool, Kress and Milwaukee angle grinders.
Easy access to replacement brushes allows you to replace them without going to the service center. There is a special plug on the body of the tool, removing which you get full access to the brushes.
Self-switching brushes allow you to extend the service life of the grinder. In the event of a sudden power outage, a sharp surge in voltage occurs. To prevent the engine from burning out, it must turn off immediately. Many units above the average cost can boast of this function, including the Sparky angle grinder made in Bulgaria.
Convenient switch . The grinder's power button itself should be as convenient as possible for the master and durable. For example, levers and wheels do not last long. And a convenient slide switch, no less than the width of a master’s finger, will serve for a long time and reliably. Found in many models, including the Russian-made Caliber angle grinder. By the way, grinders from this manufacturer belong to the economy category and are very cheap. The most expensive and sophisticated models are no more expensive than 80 USD.
A suitcase for transportation and storage is a nice bonus to a high-quality unit.
The choice of angle grinder manufacturer is also very important. Russian-made grinders are surprisingly cheap, but do not have a number of additional protection measures or functions, although they are reliable and durable. Chinese-made grinders can only be bought if you plan to do some work and then throw the unit in a landfill. European-made angle grinders Bosch, Sparky, Metabo are distinguished by their quality, durability and strength of parts. Just pay attention that the product was manufactured in Europe or Eastern Europe, for example, in Romania. Analogues from China are of very dubious quality. Japanese-made grinders Hitachi and Makita will delight their owner with the reliability, solidity and indestructibility inherent in Japanese technology.
Additional useful functions of an angle grinder:
5.1 Constant automaton
It is impossible not to mention such a useful function as maintaining speed under load. Equipment braking is often caused by the fact that the tool is moved across the material faster than it can cut it. The constant automatic machine recognizes such braking and increases the shaft rotation speed, compensating for the loss of productivity. The presence of this function is typical for a professional instrument. The cheapest tools do not have this function.
Be sure to pay attention to the location of the switch: it should be located so that it is always easy to reach. Often the keys are equipped with latches that allow you to not hold the switch. If an angle grinder with a fixed button breaks out of your hands, it will begin to circle around the floor, and you will not be able to stop it. It is highly desirable that the switch can be held without using a latch, so that when pulled out of your hands, the angle grinder stops on its own.
The shape of the body is of great importance. Grinders are divided into two types: one-handed and two-handed. One-handed ones include those that can be held by the body with one hand (although this should not be done during work, as it is unsafe). Two-handed ones have a handle at the back on which the start button is located.
If on one-handed grinders the button is located directly on the body and is small in size (you need room to wrap your hand around), then the button on two-handed machines has a fairly decent size, making it more convenient to press. Usually, large and strong angle grinders are made two-handed, since the more powerful the engine, the thicker it is. Without a handle, holding the car under a 230 mm disc would be extremely inconvenient.
The gearbox casing can be made integral with the machine body or as a separate part. The second option is preferable, since it makes it possible to configure the angle grinder for the most frequently performed type of work. To do this, you need to unscrew the gearbox and, without removing the armature, turn it to the desired angle, and then screw it back (the four screws that secure it to the body are located symmetrically).
It is clear that such a setting is available only to owners of angle grinders whose gearbox casing can be unscrewed. It is impossible to configure a monolithic angle grinder this way. Among other things, the collapsible gearbox is very easy to repair, clean from sawdust and lubricate.
Since the screws are usually driven directly into the plastic, this adjustment cannot be done frequently. Two-handed angle grinders, in which the rear handle rotates, are very convenient. You can adjust the machine in literally a couple of seconds; you don’t need to disassemble anything for this: the handle is mounted on a hinge and equipped with a position lock.
5.2 Protection against unintentional and restart
Unintentional start protection is a mechanism that blocks the start key from being pressed. To start the motor, you must first unlock the button. Considering the chaos that often reigns in workshops and in rooms where repairs are underway, the importance of such a mechanism is difficult to overestimate. With it, you don’t have to worry that the button will be pressed if it gets caught on some foreign object.
An equally important function is protection against restarting. Sometimes you have to interrupt work against your will (for example, during a power outage). In this case, the tool stops, the plug remains in the socket and there is a risk of forgetting to press the locked start button. When current is applied, the tool with restart protection will not turn on until the master releases the button and turns it on himself.
5.3 Soft start
A soft starter is usually not installed on cheap tools. The presence of this machine has nothing to do with the size of the disk and the power of the engine; it is found on both large and small angle grinders. It is much more convenient to work with it, since the grinder does not twitch in your hands, and there are no shock loads on the gearbox, which has a positive effect on its service life.
But there is one caveat: small angle grinders that are not equipped with a soft start do not require strong tightening of the flange. During the jerk at startup, the flange remains in place by inertia, and tightening occurs by itself. If there is a soft start, self-tightening does not occur, so the flange must always be tightened with a wrench.
The conclusion follows from this: on small angle grinders, soft starting only adds trouble, but on large ones it is very useful, because without it, a powerful engine makes too strong a jerk, the gearbox receives too strong shock loads and quickly becomes unusable.
As for the flange, on a large angle grinder it must be firmly fixed with a key, regardless of the presence or absence of a soft start.
If the soft start is too long, you may be tempted to put the disc on the material before it reaches operating speed, but this should not be done. To avoid such mistakes, it is better not to buy cars with a soft start that takes too long.
5.4 Kickback protection
Particular attention should be paid to the presence of a kickback prevention system (we are talking about BOSH KickBack Stop technology, Makita SJS and similar technologies from other brands, both mechanical and electronic). The cheapest tools, of course, are not equipped with it, but automatic stopping of a jammed disk can safely be called one of the most vital functions.
With it, you don’t need to think about where the “grinder” will fly during a reverse strike - it won’t fly anywhere. This function truly saves lives and preserves the integrity of limbs. However, one should not think that such systems are omnipotent and indestructible. Spring-loaded clutches, while spinning, still rub and eventually fail, and the electronics may not be able to cope with too much pressure. In other words, the tool should be handled with care, no matter what protection it has.
5.5 Balancing mechanism
Unfortunately, it is not always possible to work with a perfectly flat disk. A simple but effective balancing mechanism compensates for disc runout, although within very small limits. The structure of the balancer is surprisingly simple. This is a bearing in which the balls move freely around a circle. A poorly centered disk knocks the balls in the direction opposite to their own deviation from the axis, and they play the role of a counterweight, compensating for the eccentricity of the disk.
Why is the tool called an angle grinder?
An angle grinder is an angle grinder; the working force is applied at an angle to the body. The name “angular” is based on the design of the device: the entire device is placed in a housing, the working element of which extends at a right angle. This is the difference from straight grinding.
The angle connection imposes some limitations on functionality, so the straight grinder is more versatile. The grinder can only perform cutting, grinding and creating a polished surface; her colleague can also perform drilling and engraving.
The body is cylindrical and contains an electric motor. The motor shaft is connected to the working axis through a gear drive. The output torque is directly dependent on the power and diameter of the disk.
The external design consists of a handle with control buttons on the body itself and a screw-on handle for holding, as well as a power cord. The handle is screwed into the head of the tool without additional devices.
Additional accessories
Manufacturers often complete their products with additional accessories that greatly facilitate the work process. Such accessories include a quick-release nut like the SDS-Click superflange from BOSH or its equivalent from Makita.
SDS-Click quick-release nut from BOSH
The additional handle that comes with the cheapest angle grinders has the simplest design, while more expensive tools are equipped with a handle with an anti-vibration shock absorber. You can buy such a handle separately, but the main thing is that the thread fits the socket of your angle grinder (the sockets for handles may vary from one angle grinder to another).
Safety precautions when working with angle grinders
When working with an angle grinder, strictly follow safety rules. This is the law of life, written in blood. Be sure to install the protective cover in such a way that it protects you from sparks and debris. Install the additional handle so that it is separated from the disk by the casing.
Particular attention should be paid to protecting the face and neck.
Using a face shield when working with an angle grinder
When working for long periods of time, you should also protect your hearing by using noise-cancelling headphones or earplugs.
