Surface grinding is a complex mechanical process. In addition, it is difficult to achieve a perfectly flat surface by hand. This was dictated by the emergence of such a power tool as a grinder.
How a grinder works
The action of the grinder is based on the effect of friction of the abrasive surface of the tool on the base being processed.
There are several principles of operation of a power tool:
- Vibration. It is characterized by forward-return movement.
- Circular. The movement is around an axis.
- Combined (eccentric). Combines two principles of work – axial rotation and vibration.
- Linear continuous. Typical for a belt type tool.
Work must be done in the following sequence:
- connect the equipment to the outlet;
- provide a comfortable grip;
- turn on;
- wait until the unit picks up speed;
- bring to the surface to be treated and start grinding.
By following the steps, you can avoid injury and damage to the device.
Any grinder has the following elements in its design:
- Engine. Most often there is a collector, in the most modern models it can be collectorless. But the cost of the second option is quite high. But it does not require periodic replacement of brushes.
- Nutrition: mains, accumulator, pneumatics.
- working platformon which abrasive removable sheets, tapes, disks are fixed.
- Lever. Depending on the model, there may be 1-2 handles.
- Control system. On / off, speed control. In well-known brands, there is an additional auto-adjustment. At the moment when grinding begins, due to the friction force, the productivity of the machine drops.
In professional equipment, there is a sensor that controls the speed, which allows you to maintain the required torque intensity.
- Disk. The disc diameter directly depends on the engine power. The higher the capacity of the unit, the larger the disk can be used.
Depending on the type of grinder, there may be differences in design.
Types and functions of grinders
There is no strict classification for grinding power tools. Some of them are named according to the principle of operation, others – according to the features of the device, and still others – according to the specifics of the application.
Sanding polishing machine
The name speaks for itself, this technique is used for finishing surface polishing and restoration work. This equipment is used in the automotive industry and the finishing cleaning of varnished wood products, including parquet. According to the principle of operation, orbital and eccentric models are produced.
Polishing machines have the following specifications:
- Power consumption 901 – 1200 W. In this case, there must be a high-quality gearbox. Compared with an angle grinder (angle grinder), it has a large transmission moment.
- Max disc diameter 181 – 230 mm, for floor machines it can be 800 mm.
- The weight. The greater the engine power, the heavier and larger the equipment itself will be. For polishing jobs that are considered thin, it is better to take a small unit up to 2 kg.
- Number of turnoverin from 600 to 3000 rpm. Do not forget that this indicator is set in an idle position, with the action and increase in the friction force, this indicator will fall.
- Auto RPM. This function will output the specified parameter at the output and during operation, which will significantly improve the quality of the polished surface.
- Smooth start – an important function that, when starting up, will not allow the equipment to jump out of your hand, and when using polishing liquids, splashing will not occur in all directions.
- Protection against accidental inclusion. How relevant this function is for polishing machines is an individual decision.
- Overload protection. For this equipment, high speeds are not provided, and the design assumes a special structure of the gearbox, which is able to withstand an increased load.
- Dust collector connection. Polishing machines are more used for finishing polishing, in which there is no significant dust. Therefore, this function is not so important. But if you plan to use it often for stripping, then it is better to provide a model with such an opportunity.
Accessories and equipment for polishers depend on the application:
- Disks. It can be both soft polishing materials and abrasive ones. Fastening occurs to the platform using clips or Velcro. The second option is more popular.
- Additional handle gives a comfortable grip. Actual for larger models.
- Barbell needed when working with hard-to-reach places.
- case. A branded tool has a “package” by default – it ensures the safe storage and movement of equipment.
- dust collector. Depending on the intensity of “dirty” work. At high rates, it is better to use a construction hand vacuum cleaner.
There are models that run on mains, battery, compressor. The first two are used for domestic needs and in the semi-professional field.
Compressor connection is typical for professional industries and high intensity of operation.
The universal angle grinder (angle grinder) is designed for cutting and processing various materials: metal, ceramics, tiles, concrete, plastic, glued beams, wood. This tool in its design has an important difference from the previous one – high speed. Associated with the versatility of use.
The devices must not be intensively used as a polishing tool.
It is used for short-term work without overloads. Grinding produced by angle grinders is coarser, suitable for deburring than for finishing polishing.
By design, angle grinders can be single-handed and two-handed. The second type belongs to the professional line.
- Power consumption. Single-handed (domestic use) – 600-900 W, 1200-1500 W, two-handed – 1800 – 2100 W.
- Maximum disc diameter > 230 mm. For such consumable wheels, the recommended speed is 8000 – 10000 rpm, for small ones – 10001 – 12000 rpm. For household needs, discs 116 – 125 mm are used. They can do both cleaning the base and rough grinding.
- The number of revolutions directly depends on the power consumption, so the range of values is very large from 1000 to 12000 rpm. The operating range of 4000 – 6000 rpm is considered optimal.
- Weight and dimensions. These parameters also depend on the power of the equipment and reach up to 4.5 kg.
Additional features can make your work more comfortable:
- Auto speed control. This option is in demand for intensive use of equipment as a grinding unit. This will avoid rapid wear of the angle grinder.
- Soft start, protection against accidental inclusion. Helps to avoid jerk at startup. Ensures safe use.
- Overload protection. An important feature, especially if the tool does not provide automatic speed control.
Accessories: cutting and polishing wheels of various types.
Power supply: mains, battery, pneumatics.
The device is used for cleaning and finishing grinding of hard-to-reach places. For this, conical, cylindrical abrasive nozzles, soft of small diameter, are used. The peculiarity of such a tool is its compactness.
The equipment itself is presented in the form of a small pen.
Often the kit is supplemented with an extension trunk, which allows you to work in hard-to-reach, remote places.
- The average power consumption of a straight grinder is in the range of 600-900 watts. This is due to the miniaturization of the device.
- Maximum disc diameter ≤ 115 mm. There are also more powerful units with the ability to install consumables with a diameter of 126 – 150 mm.
- The revolutions of such equipment reach > 12000 rpm. You should know that the smaller this indicator, the greater the torque, i.e. under loads, the device will not overheat.
- The weight. It is considered optimal from 1.3 to 1.7 kg.
- Speed controller. The equipment is used for various types of surfaces, so the function must be present.
- Speed controller. The specificity of a straight grinder is “jewelry work”. Therefore, this option will not be superfluous.
- It is desirable that the engine be protected from dust.
- Another interesting option is a flexible “trunk” for working in remote hard-to-reach places.
- Stand, holder.
Accessories in straight cars:
- cone, ball, cylindrical abrasive stones;
- abrasive, soft circles;
- cue ball.
The discs are fastened with the help of scurvy, the optimal size of which is 6 mm.
Power supply: mains, battery; pneumatics. The latter type of connection is used in the production of professional equipment, increased power.
Belt sander (LSHM) – the most famous and popular type. At the base of the device there are two rollers on which a closed abrasive belt is pulled. Such a machine is used for the primary processing of wood surfaces.
When scrolling the tape and moving the equipment along the base, a layer of up to 1 mm is removed. Works are carried out along the fiber, this gives a smooth quality base. Machining across the grain will roughen it. Can be used to remove old paintwork.
Given the design features, the tape machine will not work well with metal and plastic. It is associated with high performance of the equipment, which can lead to heating of the base due to friction and its deformation.
It is not recommended to process surfaces with significant irregularities.
It will not be possible to perform high-quality processing, and it threatens to wear out consumables.
There are models for processing convex and concave surfaces.
Belt sanders have the following specifications:
- Power consumption. The model range is quite large, there are both low-power equipment with narrow tapes (601 – 900 W) and powerful units (1501 – 1800 W).
- The length and width of the tape depends on the engine power. The first dimension is in the range from 400 – 600 mm. The second, from 65 to 110 mm.
- The rotation speed of such a device ranges from 200 to 700 m/min. For domestic purposes, machines with indicators of 200 – 300 m / min are suitable.
- The weight. The average parameter is up to 4 kg. For high power units, it can reach up to 6 kg.
- Speed controller. It will allow you to work not only with wood bases, but also with plastic.
- Protection against accidental inclusion. The need for this function is decided individually.
- Overload protection. As a rule, LSHMs are rarely equipped with a speed controller and an auto-regulator, so it is advisable to provide this option.
- Dust collector connection. Such machines need this option. Processing wood surfaces, especially at high speeds, generates a lot of dust.
- Tape position and tension adjuster.
- The bounding box allows you to shoot the same layer in different areas.
Accessories – sanding belts with different abrasive sizes.
Complete set: case (usually in more expensive models), dust collector (if there is a function in the equipment itself), clamps, clamps, bounding frame. Clamps help to fix the LSM permanently. Power supply: mains, battery, pneumatics.
Random Orbital Sander
The equipment is used for fine finishing grinding and polishing. The principle of operation is circular and reciprocating motion, which resembles the movement of planets in orbit. Therefore, the device received another name – orbital. It is this distinctive feature that gives the output a surface with high quality.
Such devices are not recommended for polishing cars and surfaces with significant irregularities.
They cannot be permanently installed for processing small parts due to increased vibration.
EShM (eccentric sander) has a flat sole in the form of a plate, on which working disks are attached, using Velcro or fastening. For removal of dust on the working basis of the tool perforation is provided. Fine and polishing jobs do not require powerful speeds.
Main technical data:
- The power consumption can be ≤ 300 W or in the range of 300 – 600 W. It is typical for ESHM that at high power consumption, the revolutions are reduced, and at low power consumption, they are high.
- The maximum disc diameter is 215 mm. It is considered optimal in the range of 126 – 150 mm.
- The number of revolutions and the number of oscillations. Unlike other types of grinders, ESHM has exactly two characteristics. The first can be from ≤ 4000 rpm and go up to 12000 rpm. The number of oscillations will be 2 times more than the revolutions.
- The weight. Such machines have a small mass in the range of 1.2 -3 kg. It does not require much pressure to work. Quality is achieved due to the principle of operation at low speeds.
- An important characteristic is the range of motion. The average is 3-5 mm.
- Speed controller. For fine work, the option is needed to expand the range of processed surfaces.
- Speed controller. Its presence is required for intensive operation of the equipment.
- Connecting to a dust collector. For ESHM, this function is relevant, since the work occurs with the appearance of a large amount of fine dust.
- Pressure control. This system helps to make uniform pressure to remove the same layer.
Maximum equipment: additional handle, rod (for working in hard-to-reach places), removable network cable, case, dust collector. Power supply: mains, battery. Accessories for such equipment are wheels with abrasive of various grain sizes.
Another name is flat grinding. It is used for fine polishing and grinding work. It can be wooden surfaces, and sanding after putty. The principle of operation is based on reciprocating motion. The amplitude of movement is insignificant, at high speed.
The base of the equipment is represented by a flat sole, more often of a rectangular shape.
The speed of work depends on its area. Sanding sheets can be fastened with Velcro, clips or a combined fastening.
There is a dust extraction system. For this, a special perforation is provided on the sole and sheets. The quality of processing depends on the abrasive of the grinding sheets and speed.
- Power consumption in the range ≤ 300 W.
- The platform has a rectangular shape, width from 75 to 115 mm, length from 104 to 330 mm.
- The number of revolutions is high in the ranges of 8000 – 10000 rpm, 10000 – 12000 rpm, > 12000 rpm, depending on the model.
- The magnitude of the amplitude of movement is from 1.5 to 4.5 mm.
- Weight from 1.2 to 2 kg.
Important additional features:
- Speed controller. This will expand the application possibilities.
- Speed controller. It will help to perform high-quality fine finishing polishing.
- Soft start, protection against accidental switching on, protection against overloads is solved individually depending on the intensity of work.
- Connecting to a dust collector. The current option will help reduce indoor pollution.
- Pressure control.
Accessories: fabric and abrasive sheets, coated meshes. Maximum equipment: case, rod, additional handle, dust collector. Power supply: mains, battery.
This equipment option is a kind of surface grinders. It has the same purpose and similar characteristics. The only difference is the shape of the platform, which resembles an iron. This allows you to work with complex parts and perform grinding in hard-to-reach places (corners, joints).
The device is designed for grinding walls, ceilings, floors, and is produced on the basis of eccentric and vibration machines.
A distinctive feature is the presence of a rod in which a dust removal system is mounted.
Weight together with the bar reaches 6-8 kg.
Specifications are the same as for vibratory or eccentric machines.
- Regulator of revolutions / oscillations. This option will increase the views of the processed surfaces.
- Autoregulator. Allows uniform removal of the sanding layer.
- Overload protection. Despite the insignificant power, the remote control of the equipment does not allow you to control the level of pressure, so it is better to provide this function.
- Pressure control. This device has an actual function.
- Connection to a vacuum cleaner. For use in construction and finishing works, it is better to provide. This will reduce the emission of harmful dust into the atmosphere of the room.
Accessories: nets with various coatings, abrasive and fabric nozzles. Maximum equipment: case, rod, additional handle.
Grinder for stone and concrete
There are two versions of devices: for dry stripping and wet stripping. This equipment is widely used in construction and decoration. With it, you can level concrete and monolithic floors, clean surfaces from old coatings and seams, and remove scratches.
The support sole is made in the form of a circle. Grinding discs, cutting heads are attached to it.
The stone/concrete tool can be either a manual type or a floor type.
According to the principle of operation, these can be eccentric, vibration machines.
Specifications for manual type equipment:
- Power consumption in the range from 900 – 1500 W. There may be more powerful machines.
- Maximum disc size up to 800 mm. For manual units, 125 mm is optimal.
- Number of revolutions depending on the model average value ≤ 4000 rpm.
- The weight of manual devices is on average 2-3 kg. Floor options can reach up to 124 kg.
- Speed controller. Expands the scope.
- Automatic speed control for manual models allows you to work with a uniform load.
- For such equipment, soft start, protection against accidental activation, overload protection are relevant.
- Connecting to a dust collector. Required feature. Grinding of concrete and stone surfaces is accompanied by a large amount of dust.
Accessories are presented in the form of cutters, grinding wheels. Maximum equipment for manual models: case, additional handle (provides a comfortable grip), dust collector. Power supply: mains, battery, pneumatics.
The brush grinder is widely used for cleaning surfaces from paint and varnish coatings, rye. It is interesting to use it in carpentry to highlight the texture of wooden surfaces, aging. Fine polishing and grinding can be done.
The principle of operation is similar to the operation of a tape machine.
- Power consumption in the ranges 901 – 1200 W, 1201 – 1500 W.
- Roller diameter 120 mm.
- Number of revolutions 1000 – 3000 rpm.
- The weight of the devices is 4-5kg.
- Speed controller. Required because grinding and cleaning surfaces occur at different speeds.
- Speed controller. Useful feature for uniform surface finish.
- Mechanical adjustment of the grinding depth.
Accessories: rollers in the form of metal brushes, abrasive-polymer, nylon. Maximum equipment: case. Power supply: mains, battery.
Sanders have undeniable advantages:
- The speed of grinding operations is many times higher than during mechanical processing.
- The physical costs are much lower than manual grinding.
- The quality of the resulting surface. The presence of additional functions in the devices allows you to remove a uniform layer from the entire plane.
- With mechanical grinding, dust must be constantly removed. A modern power tool is equipped with a dust collector, or has the ability to connect to a vacuum cleaner, which makes “dirty work” clean.
- A wide range of models allows you to choose the right model for specific materials.
- Various areas of application from “jewelry work” to building a house from a bar.
- The main advantage of grinders is to make tedious and hard mechanical work fast and of high quality without much effort.
When using grinders, there are several disadvantages:
- The work is carried out in several stages, with the change of grinding discs / sheets or different tools.
- Dead zones. Every machine has them. You will have to refine it mechanically, or purchase a narrowly focused tool (straight grinder, delta grinder).
- Price – options. Additional features are deferred to the cost of equipment. Saved on purchase, repair costs are acquired.
- The presence of fakes of famous brands.
How to choose a grinder
To select any power tool, you should determine for yourself:
- Scope and scope. This parameter allows you to focus on a specific type of equipment and decide on accessories and equipment.
- Intensity of exploitation. It will help you choose the right power, number of revolutions.
- Ability to connect to the network. In this case, it will be easier to decide what type of power the grinder should have – mains, battery, pneumatics.
- Budget. It is decided individually, it helps to announce to the seller the price segment in which to look for a suitable model.
- Manufacturer. It is better to give preference to well-known brands.
- Guarantee. Warranty conditions and the availability of a service center.
- Ergonomics. Before buying, you should hold the tool in your hands. Feel how comfortable it will be to use.
These are the points that will make it easier to choose a tool. It should be remembered that savings when buying can lead to additional repair costs in the future.
Which is better
When choosing a grinder, it is impossible to say unequivocally which tool is better to purchase. We can only indicate some of the distinguishing characteristics that should be noted.
- For polishing cars, paintwork surfaces, it is better to take polishing machines.
- For rough processing of wood surfaces – belt, angle grinders. They have high performance.
- For final grinding, polishing of wood sheets – vibrators and orbital.
- For hard-to-reach places straight and delta grinders.
- Brushes are suitable for cleaning surfaces, highlighting textures.
- For construction needs, it is better to take wall grinders and devices for concrete / stone.
From the point of view of safety and convenience of work, it is better to take equipment that has the following options:
- regulator and automatic speed controller;
- protection against accidental start;
- grinding depth regulator;
- connection to the dust collector and its availability;
- the ability to quickly change consumables;
- ease of assembly / disassembly during maintenance;
- additional handle;
- protection of the engine against dust pollution.
This will help to perform quality work and prevent the risk of rapid equipment wear.
After completion of work, the grinder should be thoroughly cleaned and periodically lubricated moving parts. If the dust collector has become worse to absorb dust, it is necessary to disassemble and clean it.
It is recommended to use consumables with the characteristics declared by the manufacturer. It is necessary to control that the power cord does not fall into the working area of the device and prevent overheating of the equipment. Store the device in a dry, heated room.
All these measures will prevent the rapid wear of machines.
When working with the equipment, observe safety measures and use safety goggles and a dust mask.
A very important factor in choosing and buying a tool is the terms of warranty service. The term is set either by the manufacturer or the seller.
Warranty obligations do not apply if the service center proves that the cause of the breakdown is related to improper operation, storage, and transportation.
Most often, the warranty does not cover the mechanical parts of the grinder, only the elements that move when turned on, the automation.
Therefore, when purchasing, you should carefully inspect the tool and check it for performance.
Be sure to keep all documents for the purchase and do not remove the identification marking from the device.
In the event of a breakdown, you should contact the service center, which is indicated in the passport for the equipment. If it is proved that the warranty case, then the buyer has the right to demand: repair, or replacement, or a refund.
The design of grinders is not particularly difficult. And repair is carried out by replacing faulty parts with new ones. The motors in such a power tool are commutator-type, they are light in weight and have good power.
The main parts that can fail:
- Carbon brushes. This is a consumable item that has its own life and must be replaced periodically. Check if the copper plates to which the brushes adjoin have oxidized. Oxidation is eliminated with a rubber eraser.
- Breakdown of the winding. Self-repair is not possible, it is required to completely remove the winding and wind a new one.
- Malfunction of buttons, wiring (over time, the latch is erased, and the contact pad). It is necessary not only to correct, but also to establish the cause of this breakdown.
- Rotor bearings. If a malfunction is found, replace.
- The bevel gear pair is worn out – replace.
- When the machine is overloaded, the grinding of gear teeth (with increased wear of the teeth, the backlash increases) must be replaced.
When working, it is important to mark the parts or take a step-by-step survey, which will later facilitate the correct assembly of the tool.
There are a large number of grinder manufacturers on the market. Consider the main brands:
AEG. Specialization in household appliances and power tools. This company has established itself as a quality supplier of woodworking equipment, which includes grinders. Distinctive characteristic – powerful reliable engines. Batteries deserve special attention.
The warranty period is 12 months from the date of purchase.
Black&Decker. Specialization in gardening and power tools. The equipment belongs to the household category. There are three categories, they differ in color: red, silver, green. Factory warranty of 24 months.
board. Part of the SBL group of companies. The assortment is quite extensive: garden equipment, power tools (drills, airbrushes), household appliances (refrigerators, air conditioners, etc.), devices for cars. Warranty period of 24 months.
Bosch. Specializes in the production of power tools, garden equipment. There are professional lines, and for domestic needs. The price range is different. High level of service.
The warranty period can be up to 36 months.
Defort. Part of the SBL group of companies. The range is quite extensive garden equipment, power tools, household appliances, devices for cars.
Warranty period of 24 months.
DeWALT. Specialization – professional power tools. One of the most popular brands on the market today, meeting all safety, reliability and durability standards.
The original tool on each part of the body has an embossed letter logo. Products are available only in yellow-black case. Particular attention is paid to the availability of maintenance, work safety, and the environment.
Warranty period up to 36 months.
FELISATTI. It specializes in the production of professional tools and equipment for construction and woodworking. Much attention is paid to new technologies. The warranty period is 24 months from the date of purchase.
Hammer. The company produces professional household tools. Woodworking specialization. The warranty period is 36 months.
hitachi. They produce power tools and equipment for industry, construction medicine, and household purposes. Reliability, quality and durability of the equipment is proved by years of faithful service.
Warranty period 36 months, batteries 12 months.
Interskol. Russian manufacturer. It is in the middle segment both in terms of price and quality. The grinding machines of this plant have established themselves as reliable. Produces tools for woodworking, concrete work, garden tools.
The warranty period is 12 months.
Caliber Russian manufacturer, not so long ago appeared on the market. Low price with good quality. The warranty period is 12 months.
Makita. The company’s products are classified as professional. Tools are produced gasoline, electric, battery. The warranty period is 12 months. In case of repair, its period is extended by the time spent in the service center.
Metabo. They produce tools for construction, metal processing, and gardening. Products belong to the professional line. The warranty period is 36 months, including for lithium batteries, which serves as a guarantee of quality.
Skil. They produce garden, household and professional tools. Warranty period 12-24 months, but from the date of purchase by the first buyer. Those. considering that the dealer is the first buyer, then equipment can be delivered to a simple consumer with a warranty period from the seller.
The list of presented manufacturers of grinding machines is far from complete. It should be noted that sometimes low-quality equipment can be hidden behind a well-known brand. To be safe, you can ask the seller’s service center about a particular device, whether there were any complaints about it and what.
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