Wood grinding machine - do it yourself or buy it? Belt sander: we study and do it ourselves Making a belt sander

Grinder (English) literally - a crusher. Meat grinder is a meat grinder, rock (stone) grinder is a stone crusher; stick (wood) grinder - garden crusher of branches and rods into chips. But there is also a completely unambiguous meaning of the word grinder: in mechanical engineering and metalworking, this grinding machine. A useful household item. For example, it is impossible to guide a dull meat grinder knife on a whetstone by hand. On a manual knife sharpener - somehow possible, with a solid working skill. And on the grinder - no problem. The same - if you need to grind a part of a complex shape without violating its profile. Or just sharpen scissors or a professional knife. All kinds of cutters for wood and metal are best corrected also on the grinder. It is quite possible to design and assemble a grinder with your own hands, without having sophisticated equipment and skills to work on it. In terms of money, this will mean savings from 50-90 thousand rubles. up to 3-6 thousand USD.

To make a grinder yourself, you will need to order a maximum of 4-5 turned parts, and it is often possible to do without turning from outside at all. For example, how to make the simplest grinder literally from trash, see the video below:

Video: do-it-yourself tape grinder from trash

Or another option, how to make the grinder stronger and more resilient from scrap metal:

Video: scrap metal grinder

Disk or tape? And drive

Almost more varieties of grinding machines are used in industry than lathes. Emery known to all craftsmen - a motor with a pair of grinding wheels (or one circle) - this is also a grinder. For yourself at home, it makes sense to make either a disc end (plate) or a belt grinder. In the first, the abrasive is applied to a rotating hard disk; in the second - on an elastic tape running around a system of pulleys and rollers. Disc is more suitable for grinding simple wooden parts and rough or medium cleanliness - metal. On a belt grinder, it is also possible to produce precise and clean finishing of profiled parts of complex shape, incl. large, see below.

A disc grinder is very simply obtained from the same emery or a motor of suitable power, see below. It is necessary to order an adapter from the motor shaft for the shank of a cup-shaped grinding wheel on a metal base. Or under a chuck, then on the same motor it will be possible to build a mini lathe, see fig.:

A worn-out “plate” is suitable: a disc made of thin (4-6 mm) fibrous plastic is glued onto the edge of its side, and an abrasive is placed on it. How to make an end grinder, see next. video clip.

Video: homemade end grinder

The difference between a disc grinder and a belt grinder is not only in the possibilities of use. If you take ordinary home crafts, then a drive power of 250-300 W on the shaft is enough for a disk grinder. For small wooden parts - and 150-170 watts. This is an old motor washing machine, straight (ordinary) drill or screwdriver. But for a belt grinder, you need an engine from 450-500 W: three-phase with batteries of starting and working capacitors. If it is supposed to process a large size, then the motor power is from 1-1.2 kW. Moreover, capacitor banks for both will cost a little less than the engine itself.

Note: a 100-200 W drive uses a mini belt grinder (see below) for fine dressing of knives, grinding / polishing jewelry, etc.

A drill or screwdriver as a grinder drive is also convenient in that it allows you to quickly change the speed of the abrasive (see below) with a standard speed controller. It is only necessary, firstly, to make a holder for the drill, rigidly fixing the tool. Secondly, an elastic adapter from the drill to the disc shank, because it is difficult to achieve their precise centering without special equipment, and the runout will negate the accuracy of processing and can damage the tool-drive.

Drawings of the drill holder for using it as a drive for a home metal-cutting machine are given on the left in the figure:

Since shock and irregular alternating loads on the drive in the grinder are an order of magnitude lower than, say, in lathe, the drill holder for it can be made of solid wood, plywood, chipboard, MDF, on the right in fig. The diameter of the mounting (large) hole is along the neck of the drill. It is highly desirable to use a drill without an impact mechanism and with a steel shell on the neck (for the installation of the front handle).

Coupling

For the adapter, you will need a piece of steel bar (not necessarily turned) of the same diameter as the shank of the grinder drive shaft, and a piece of reinforced PVC hose (garden irrigation) with a gap so that it is tightly pulled over the bar and shank. The length of the “free” hose (between the ends of the rod and the shank in it) is 3-5 cm. The length of the protruding part of the rod should be sufficient for a reliable clamp in the drill chuck. After assembling the coupling in place, the hose on the shank and rod is tightly tightened with clamps; can be wire. Such a coupling completely parries the misalignment of the drive and the driven shaft up to 1-1.5 mm.

Ribbon is still better.

A belt grinder allows you to do everything that a disc grinder does, and more. Therefore, further we will focus on how to make a belt sander with our own hands. Amateurs, focusing on industrial designs, sometimes make grinders very intricate, see fig.:

And this is justified: the design and kinematics of the belt grinder are very flexible, which makes it possible to successfully use improvised materials and old scrap metal. You just need to follow 3 principles:

Do not do as in the second photo from the left: the tape with the abrasive side should only touch the workpiece. Otherwise, the abrasive will eat both the bypass rollers and itself. The accuracy and cleanliness of processing during one working operation will be unpredictable;
The design of the machine must ensure uniform belt tension, regardless of the nature of the operation being performed;
The speed of the belt movement must correspond to the nature of the operation being performed.

Kinematics and design

As mentioned above, there are many designs of grinders. Thinking about what and how to build a grinder for yourself, it is better to focus on industrial designs designed for fully mechanized precision and clean grinding of large-sized profiled parts: since the propeller blade of an aircraft or wind turbine “skins” as it should, then it will cope with any other work.

Kinematic schemes of grinders for the specified purpose are given in Fig.:

Basic kinematic diagrams of belt grinders (grinders)

Pos. A - the most complex and perfect, with three rocker arms. If the length of the tensioning roller rocker is approx. 2 times less than the working one, then by adjusting the tension of the springs, it is possible to achieve a uniform tension of the tape when the working rocker moves 20-30 degrees up and down. By tilting the bypass rocker, firstly, the machine is reconfigured for belts different lengths. Secondly, in the same way, you can quickly change the belt tension for different operations. The working branch of the tape can be any, except for the one running from the drive pulley to the tension roller, i.e. a grinder with 3 rocker arms is both horizontal and vertical at the same time.

A scheme with a coaxially swinging rocker (pos. 2) is simpler, cheaper and not inferior in processing accuracy to the previous one, if the length of the rocker between the axes is at least 3 diameters of the workpiece. In order to knock down the profile by grinding, the course of the rocker arm is limited by stops within 10 degrees up and down. The clamping of the tape to the part is most often gravitational, under the weight of the rocker with a bypass pulley. It is possible to quickly change the tension of the tape within certain limits by pulling the rocker up with a weak adjustable spring, which partly compensates for its severity. The grinder of this scheme can work as a grinder for small parts from a sliding table. In this case, the rocker arm is rigidly fixed horizontally, and the running surface of the tape will be a bypass pulley. According to the scheme with a coaxial rocker arm, for example, a fairly popular BTS50 grinder was made. The disadvantages of the scheme are, firstly, the technologically complex rocker arm hinge coaxial with the drive shaft. Secondly, the need for an elastic band: if you make the bypass pulley sliding spring-loaded, the machining accuracy drops. This disadvantage when processing small parts is completely eliminated by an additional tension roller, see below.

A scheme with one misaligned rocker arm in industry is used quite rarely, because. in principle, it does not allow to achieve a uniform tension of the tape. However, it gives an accuracy that is quite sufficient at home and allows you to build a very good simple grinder.

What's good for what

Now let's see what is possible to "squeeze" out of this or that scheme from the point of view of an amateur master. And then we’ll try to figure out how to make a belt for the grinder ourselves and do without custom-made turned parts.

3 rockers

Competent amateurs build their grinders exactly according to the scheme with 3 rocker arms, on the left in fig. below. Far from all propeller blades are ground, but in this case another advantage of this scheme operates: if the grinder is used as a vertical one, then the working branch of the tape is elastic. This allows a skilled craftsman, for example, to guide cutting edges and blades with literally micron precision.

In industrial grinders for home use, the 3-rocker pattern is also widely used (in the center) for the same reasons. Repetition of them independently in most cases is quite possible. For example, drawings of the popular KMG grinder abroad can be downloaded.

The dimensions, however, are inch - an American typewriter. For the drive, in any case, it is possible to use an angle grinder drill (on the right in the figure, it is quite suitable in terms of power) with a homemade pulley and rollers, see below.

Note: if you are making a stationary drive, try to get a 2-3 speed asynchronous motor from a worthless washer with a horizontal tank. Its advantage is low turnover. This makes it possible to make the drive pulley of large diameter and thereby eliminate belt slippage. A slippage of the tape in the work is almost certainly a damaged part. Most washing machines with 2-3 speed 220 V asynchronous motors are Spanish. Shaft power - 600-1000 watts. If you come across one, do not forget about the standard phase-shifting capacitor bank.

Coaxial rocker

IN pure form amateurs do not make grinders with a coaxial rocker. The coaxial hinge is a complicated thing, you can’t make an elastic band yourself, and a purchased one is expensive. Grinders with a coaxial rocker at home are most often used in the variant for fine precision work from the table, i.e. with a rigidly fixed horizontal beam. But then the need for a yoke as such disappears.

An example is a mini grinder, the drawings of which are given in Fig.:

Its features are, firstly, an overhead bed for the tape (pos. 7), which greatly expands the possibilities of use. For example, a planer iron is straightened on this grinder with an angle stop literally by itself. In this case, the grinder works, so to speak, like a self-propelled donkey (emery bar). After removing the bed, we get a grinder with an elastic band for precise grinding / polishing of rounded small parts. Secondly, the tension shaft (pos. 12). Clamping it with a groove with nuts, we get a relatively fixed tension of the tape for working with the bed. And having released the nuts, we put the grinder into the mode of gravitational tension of the belt for fine work. The drive is not necessarily through a pulley (pos. 11). Can be screwed directly behind the drive shaft shank (pos. 16) from the drill through the adapter, see above.

A specialized tool grinder (for example, for aiming and dressing turning tools) generally loses any semblance of the original scheme. A high-speed motor is taken for it (a power of 200-300 W is enough). The drive pulley, respectively, of small diameter. The bypass pulley, on the contrary, is made larger and heavier, for inertia. All this together allows you to reduce the runout of the tape. The tension roller for the same purpose, plus for greater uniformity of the tape tension, is taken away and spring-loaded with a long, not very strong spring. How to make a cutter grinder, see the video below.

Video: cutter grinder

One rocker

In amateur practice, grinders with misaligned rocker are good because they do not need precise details at all. For example, hinges can be made from card loops. At the same time, the accuracy of processing remains sufficient for ordinary amateur requests.

The original scheme in this case is also modified: the rocker is rotated 90 degrees, carried up and spring-loaded, on the left in Fig. It turns out a simple vertical grinder. And, importantly, it works without problems with a home-made inextensible tape. Both tension spring (in the center) and compression spring can provide belt tension. Its strength is not important, as long as the tape does not bend excessively during operation. No adjustments are required during use.

Consumables and parts

The only consumable item for a belt grinder is a belt (not including grease for bearings and joints. Belt can be ordered desired length(see at the end), but you can also make it yourself from emery cloth on a textile basis. Highly desirable - flexible, unimpregnated. In general, the procedure for making a tape for a grinder with your own hands is as follows:

We cut off the workpiece - a strip of the desired length and width.
We prepare a mandrel (not necessarily round) with a length along the generatrix slightly less than the length of the tape.
We circle the mandrel with the workpiece inside out.
We bring the ends of the workpiece exactly end-to-end and securely fasten.
We put a piece of glue stick for a hot glue gun on the joint.
We heat with a building hair dryer until the glue melts.
We impose a patch of thin fabric on the joint.
We press something hard through the Teflon film until the glue hardens.

There are three significant points here. The first is to use a rough PET film with a thickness of 25-50 microns (sold) instead of fabric on the patch. It is very durable, but try running your finger over a PET bottle. Not very slippery? A rough PET film under tension cannot be stretched over polished metal. And instead of a patch, it is better to seal the wrong side of the tape with a continuous strip of PET film with an overlap of 2-3 cm. The beating of the tape will be no more than 0.05-0.1 mm. This is less than from the thinnest calico and even less than the error in the thickness of the skin-blank.

The second - fill the finished tape into the machine and grind something obscene with it without strong pressure. The hem on the seam will come together, and the tape will become no worse than the branded one.

But the most important thing is that in terms of elasticity, the best adhesive for gluing the grinder tape is not expensive and difficult to use thermal or assembly, but ordinary PVA. If the tape is pasted over with a lining along the entire length of the inside, then its strength for PVA is more than enough. How to glue a tape for a PVA grinder, see the video

Video: gluing the grinder tape with PVA glue

Pulley

The generatrix (lateral surface in section) of the drive pulley of the grinder must be straight. If you use a pulley-barrel, then the tape will bend like a trough along its entire length. The rollers do not allow it to slip, see below, but the pulley generatrix must be straight.

A pulley for a grinder that is not designed for particularly precise work, firstly, does not have to be turned. In the scheme with 3 rocker arms, the beating of the tape from its misalignment will go out on the rollers before it reaches the working branch. In a simple vertical grinder, the belt runout will be sufficiently damped by the tension spring. Therefore, it is quite possible to make a pulley for a grinder without a machine, see video:

Video: drive wheel on a grinder without a lathe

The second is that the pulley, rollers and, in general, all the details of a home grinder can be made from plywood. In production, this is certainly not an option, even if the plywood grinder is offered for free with an additional payment: the grinder needs a salary, and the wooden grinder in the workshop will completely wear out before it pays for itself. But you won’t drive the grinder at home day after day in 3 shifts. And no tape slips along the plywood pulley. Incl. homemade. So you can safely make a grinder pulley out of plywood:

Video: plywood grinder pulley

It is much more important to correctly calculate the diameter of the pulley according to the speed of the motor and the required speed of the belt. Too slow running belt will tear the processed material; too fast - it will be erased by itself, without really processing anything. In which case, what tape speed is needed is a special conversation, and a very difficult one. In general, the finer the abrasive and the harder the material to be processed, the faster the belt should move. How the speed of the belt depends on the diameter of the pulley and the speed of the motor, see the figure:

Fortunately, for most abrasive-material pairs, the allowable limits for belt speed are quite wide, so choosing a grinder pulley can be easier:

Video: which wheel is needed for a belt grinder

Rollers

The rollers of the grinder, oddly enough at first glance, are its most important details. It is the rollers that keep the tape from slipping and ensure its uniform tension across the width. Moreover, there can be only one video in kinematics, see, for example, the video above about the cutter grinder. Only barrel rollers will cope with this task, see below. But the “trough” of the tape after any roller should straighten out before it reaches the working area.

Rollers with flanges (sides, edges) will not hold the tape. The point here is not only and not so much with the misalignment of the axes of the rollers: the grinder belt, unlike the drive belt, must withstand, without slipping, the loads from the workpieces. If you make rollers with flanges, then, just touching something to the tape, it will crawl onto the flange. In the grinder, you need to use Type 3 barrel rollers (highlighted in red on the left in the figure).

The dimensions of Type 3 rollers are also given there. It is advisable to take the diameter of the rollers no more than 0.5 of the width of the tape (so that the “trough” does not go far), but not less than 20 mm of steel turned and not less than 35-40 mm of plywood. The tension roller (the probability of the tape slipping from it is greatest), if the working branch of the tape does not leave it, can be 0.7-1.2 in diameter of its width. Plywood rollers are made in the form of a thick shell into which the bearing is pressed; then the roller is mounted on the axle (in the center in the figure) and finished clean, see e.g. track. video:

Video: barrel roller for grinder

Not every turner can machine a profile barrel roller exactly according to GOST. Meanwhile, there is a way to make rollers for the grinder without significant difficulties. The same garden reinforced PVC hose will help out, on the right in fig. previously. On the roller blank with a straight generatrix, its segment is pulled tightly and cut off with a margin along the edges to the thickness of the hose wall. It turns out a roller with a complex generatrix profile, which holds the tape even better and gives it a smaller “trough”. Don't believe? Try to get into the graveyard of planes or missiles and dig into them. You will find rollers with exactly the same generatrix profile. It's just that the mass production of rollers of a complex profile is much more expensive than Type 3 barrels.

And another option

All critical parts of the grinder - one-piece belt, non-slip coated pulleys, rollers - can be purchased separately. They will cost not so cheap, but still not in thousands of foreign and not in dozens of native "leather jackets". The remaining parts of the grinder, either flat or from professional pipes, are made using a conventional bench drill or drill. Here is where you can order grinder parts:

//www.cora.ru/products.asp?id=4091 - tape. Do lengths and widths at the request of the customer. Advise on abrasives and processing modes. The prices are acceptable. Delivery time - questions to Ruspost.
//www.equipment.rilkom.ru/01kmpt.htm - spare parts (accessories) for grinding machines. There is everything, the prices are divine. Delivery - see prev.
//www.ridgid.spb.ru/goodscat/good/listAll/104434/ - the same, but foreign-made. Prices are higher, delivery is the same.
//www.pk-m.ru/kolesa_i_roliki/privodnye_kolesa/ - drive wheels. You can find suitable for the grinder.
//dyplex.by.ru/bader.html, //www.syndic.ru/index.php?option=com_content&task=view&id=36&Itemid=36 – spare parts for grinders. Ribbons are not made to order - choose from the catalog. Rollers without axles; axles are sold separately. The quality is impeccable, but everything is very expensive. Sending - within 2 weeks to the border. Then - their customs, our customs, Ruspost. Total ok. 2 months It may not reach if some local bureaucrat considers the goods to be sanctions. In this case, there are no problems with the return of the payment due to the complete absence of real opportunities for an ordinary citizen to receive one.

5,00

Sanding is one of the methods of processing wood, which allows you to give the blanks a perfectly flat surface. A versatile wood sander will be functional and easy to use. For processing lumber, you can use units manufactured by specialized manufacturers, or you can make such equipment yourself, which will save a lot.

Types of woodworking machines

Currently, there are numerous types of grinders that are designed to perform various kinds of work with wood. They differ in their design, are intended for household and industrial use. You can easily pick up both highly specialized models and universal machines which are intended for complex processing of wood.

If necessary, you can make a home-made grinder for metal or wood, made on the basis of a drill, a motor from a washing machine, or using other equipment.

Disc units

The working surface of do-it-yourself grinding machines for metal and wood is made in the form of an island metal disk, on which an abrasive is attached. Due to its simplicity of design and versatility of use, this type of equipment has gained wide popularity in the market today.

This machine consists of an electric motor, on the axis of which a circle with a fixed working surface is put on. Abrasive nozzles and sanding paper are attached to the working axis, which allows processing wooden blanks. Despite the simplicity of design, such machines are versatile in use, they can perform high-quality wood processing, giving the workpieces a perfectly flat and smooth surface.

The advantages of surface grinding technology include:

Versatility of use.
Efficiency.
Reliability.
Simplicity of design.

A feature of this type of equipment is the ability to adjust the speed of processing wooden blanks without changing the indicator of the number of revolutions of the working element. When working with such a machine, you can move the workpiece along the radius of the circle, which allows you to change the intensity of processing products. At the edge of the disk line speed will be higher, which allows you to significantly speed up and simplify the processing of wood. But inside the circle, where the linear speed is lower, final sanding is performed with the removal of the thinnest layer of wood.

Belt plants

Belt sanders have two shafts between which a continuous belt of sandpaper is stretched. Processing of blanks is carried out by exposing them to sandpaper, which removes thin chips from wooden blanks, giving them a perfectly flat, smooth surface. The working surface of disc machines can be vertical and horizontal, while individual models allow you to change the direction of the tape. With the help of such equipment, it is possible to process products of great length, aligning their ends. The simplicity of the design allows you to make a belt grinder for domestic use with your own hands.

drum models

The main purpose of this type of units is horizontal alignment using a jointer. This type of equipment is mainly used in industrial workshops, which is explained by the complexity of its design and the narrow specialization of drum units. With the help of grinding drum machines, wooden products of the same type with the same thickness are manufactured and processed.

Manufacturing of grinding machines

Industrially manufactured machines offered today in specialized stores are distinguished by their versatility in use, functionality and efficiency. Their only drawback is high price , therefore, if it is necessary to perform various kinds of grinding work, most homeowners decide to manufacture homemade equipment, which in terms of its parameters and quality of processing is practically not inferior to factory units.

A structurally made do-it-yourself metal grinding machine will consist of the following components:

Metal or wooden frame.
Electrical engine.
Drive shaft.
Working surface.
Sanding belt.

When making a drum grinder for wood with your own hands, you need to determine the power of the electric motor used. It is recommended to choose electric motors that develop about 3 kW and are able to maintain a clean speed of 1,500 rpm. On the basis of such a drive, a functional, durable and reliable grinding machine can be manufactured that can cope with the processing wooden products. The easiest way is to make such equipment based on an electric motor from an old washing machine.

The grinder bed can be made of lumber or metal corner, welded and additionally sheathed with plywood. It is necessary to choose the dimensions of the frame based on the dimensions of the drive used, as well as the dimensions of the wooden blanks processed on the unit. When performing the frame, it is necessary to focus on the existing project documentation, which will allow you to correctly manufacture the bearing base of the machine, which in the future will be able to withstand significant loads.

The shaft of the manual and automatic belt grinder, which is directly connected to the electric motor, can be machined on a lathe or use ready-made blanks from industrial equipment. The shafts of the calibrating drum grinder must be located strictly in the middle of the main drive, which subsequently guarantees high-quality processing of wooden blanks.

The optimal width of the sanding belt used will be 200 millimeters. It can be done from emery, which is cut into strips and subsequently the used abrasive tape is already glued from them. The material should be glued end-to-end, and with reverse side dense matter is laid, which will ensure the strength of the seam.

Having made a grinder with your own hands, you can significantly simplify the processing of wooden blanks, leveling boards and removing chips from lumber. Making such a unit with your own hands is not difficult. On the Internet, it will be necessary to select a diagram-drawing for the manufacture of the machine, and using an electric motor from an old washing machine, make the simplest equipment, which in terms of its functionality and quality of processing will not be inferior to factory-made equipment.

During construction and repair work men often need to process wood, stone or metal. For quality work, it is advisable to purchase a belt sander. But what to do when finances do not allow you to make such a purchase? To do this, it is enough to build a belt sander with your own hands.

Purpose of the belt sander

Wood is widely used in a variety of industrial organizations. Wood is used to make many kinds of details and products. In order to properly process a wooden blank and give it the appearance of a finished product, it is customary to use various equipment, including belt sanders.

Belt sanders are generally used for final stages production, when parts are subjected to finishing machining. Such devices are convenient to use in the manufacture of furniture and various consumer wood products. Depending on the material used, belt sanders work with wood or metal.

The main goals of using grinders for wood are the final leveling of the surface, bringing their level of roughness to the required level, obtaining even and smooth surfaces for wood products and wood-based material before veneering or after varnishing and other coatings. finishing materials, removal of local irregularities in the form of depressions and elevations, deburring and removal of local varnish and primer deposits, deburring, internal grinding and grinding of roundings.

Metal belt grinders work with various materials and formats that are popular in metalworking: plain and alloyed steel, non-ferrous metals in the form of square, round and flat billets. Grinding machines allow you to grind round timber and large diameter pipes rationally and with minimal time.

Depending on the type of processing and type of feed, belt grinders are intended for:

for sanding curved surfaces with free sanding belt;
for processing a flat surface with a fixed table, manual movement of the iron and table, as well as mechanized movement of the work table and manual movement of the iron;
for processing panel and bar parts, their ends and side edges;
for intermediate sanding of paint and varnish coatings.

The design of the belt sander

Belt grinding machines are produced by modern foreign and domestic manufacturers in a wide range. Grinding machine prices vary considerably. They also differ in their possible performance and their design. However, they also have something in common. They are united by the fact that absolutely all machines have an abrasive belt as a working body, which is most often connected into a ring and placed between rotating drums.

One drum is the leader and the other is the slave. This means that the first of them is equipped with a mechanical transmission, which is most often based on a belt drive, through which torque is transmitted to it from an electric motor. Any belt grinder is designed so that the speed of the driving drum, and therefore the speed of movement of the abrasive belt can be changed, providing different modes of surface treatment.

The abrasive belt can be positioned vertically or horizontally. In addition, there are equipment modifications on sale in which the working body is installed under certain angle. The abrasive belt is mounted on a bed, on which the workpieces are usually located. Workpieces can be held manually by the operator, or with the help of special devices that facilitate the work of users and make the processing procedure more efficient and safe.

The machine table is made of metal sheets or thick boards. If the design provides for the manufacture of a table precisely from metal, then it will turn out to sharpen more complex products. The length of the working part of the belt grinder and the grinding belt itself primarily depends on the length of the products that will be sanded on the machine.

If the part has a shorter length than the working surface of the machine, then it will be much more convenient to process it, and the processing will turn out to be of better quality. For example, with a sanding belt length of 4.5 meters, wooden blanks can be easily processed, which have a length of 200 centimeters.

Belt grinding machines are divided into equipment with a fixed and movable work table and devices with a free belt. A special group is wide-belt grinding machines, in which the table, which is made in the form of a caterpillar, is also a feed organ. On machines with tables, the tape is placed horizontally, on designs with a free tape, it is installed in different ways.

Since a lot of dust is inevitably generated during the grinding process, all belt grinders are usually equipped with special powerful hoods that remove most of it during the very technological process. Grinding machines are powered by an electric motor, which has a power of about 2.8 kilowatts. With a high power motor, the normal belt speed reaches 20 meters per second.

Abrasive belts for grinding machines

The cutting tool of belt grinders is a sanding belt, which consists of a fabric or paper base and abrasive grains that are attached to it with adhesives. Abrasive belts are produced by two methods: mechanical and electrical. The first method consists in uniformly pouring abrasive grains onto the base, which is covered with glue, and the second method occurs in electric field, which orients the grains upwards with the sharpest edges to improve the cutting properties of the grinder.

Abrasive grains are poured onto the base in a bundle densely or rarely. The most effective is an abrasive belt with a rare backfill, when the grains occupy less than 70% of the area, because the wood dust generated during the grinding process is not able to clog between their grains. Can be used as an abrasive material natural minerals or artificial materials, which have high hardness, such as green and black silicon carbide, white and normal monocorundum, and normal electrocorundum.

For the purpose of gluing the grains, synthetic resins and skin glue are used. As a base, use a fabric such as calico and twill, or a special grade of paper. The size of the abrasive grains is indicated by a number that corresponds to the mesh size of the sieve in which these grains are retained, and is displayed in hundredths of a millimeter.

If you are interested in how to make a belt sander, then you should pay attention to the following sizes of grinding powders and abrasive grains and their classification: grinding grain - from 2000 to 160 microns, grinding powders - from 125 to 40 microns; micropowders - from 60 to 14 microns, very fine micropowders - from 10 to 3 microns.

Sanding paper is supplied to woodworking enterprises in sheets or rolls. On the non-working surface of the skin there is a marking with the specified characteristics of the skin and the manufacturer. For a belt sander, skins are used in rolls and cut into strips of a certain length and width. The length of the cutting tool is determined, depending on the method of its connection - overlap or butt at an angle.

The ends are cut off at a 45 degree butt joint and then glued onto a linen backing 80 to 200 millimeters wide. At one end of the tape, when lapping, abrasive grains are removed hot water for 80 to 100 millimeters, then the other end of the tape is applied to the bare base smeared with glue. Compress the connected ends and dry them using a special tool or size press.

Sheet skins are used for combined belt sanders. For grinding discs, it is customary to cut the skin in the form of a circle according to a pattern, the diameter of which is 60 - 80 millimeters larger than the diameter of the disc. Using a rectangular template, blanks are cut out for a bobbin. After cutting, they have smooth edges without tearing. The presence of unglued ends or seals when gluing the tapes can cause the tape to break prematurely.

The skin is cut for wide belt sanders into sheets according to a template that is made of plywood or aluminum sheet. The skin is cut in such a way that the edges are even, and the difference in the length of the side edges is no more than 1 millimeter. One of the beveled edges is cleaned, removing the abrasive at a width of 20 millimeters. The cleaned edge and the longitudinal edges are pasted over with a strip of tracing paper, which has a width of 40 millimeters, which protrudes beyond the edge of the skin by about 10 millimeters.

Lubricate the beveled edge with tracing paper with glue and keep it in the air, depending on the viscosity and type of glue. Then the beveled edges are connected and a strip of skin is applied to the junction, the junction is compressed and held in a press. Ready-made endless tapes are usually hung on special brackets and kept for at least a day in a dry room before being installed on a grinding machine.

The principle of operation of the belt grinder

The belt sander consists of a worktop with a working table for attaching the cutting tool. This table is fixed in different positions relative to the tabletop. The material for the countertop is usually laminated chipboard with a thickness of 25 millimeters. The working table on rollers moves manually or in the transverse direction by means of a mechanical drive on round guides that are attached to the calipers.

Above the table is a working tape, put on non-drive and drive pulleys. The sanding belt is tensioned and adjusted using a screw device with a pneumatic cylinder. Twin belt sanders have two identical sanding tools that are placed in series on the bed and have sanding belts that move towards each other.

Grinding is performed with the transverse movement of the working table and the longitudinal movement of a short iron, which presses the tape against the material being processed. Sanding belts are driven by an electric motor through a belt drive. Waste that is generated during grinding is captured by a dust collector, which is connected to the exhauster network.

When assigning a grinding mode, it is recommended, according to a certain roughness and properties of the material that is being processed, to choose the grit of the skin, the feed rate and the force of pressing the tape to the product. It is customary to choose the grain size of the skin, depending on the hardness of the processed materials and the required surface roughness. Clamping force and feed rate are interdependent quantities. With a small effort and a high feed rate of the skin, some places on the surface can not be sanded, with high pressure and low feed, burns and blackening of the material are possible.

Before installing the tape, check the quality of its bonding. Do not use incorrectly glued and torn sanding belts with an uneven edge. Using the handwheel, you can reduce the distance between the pulleys and put on the tape. The place of gluing is placed so that the outer end of the seam on the side of the abrasive is directed against the working movement of the sanding belt.

The belt tension can be adjusted by moving the tension roller for the belt grinder or the non-drive pulley. It is not advisable to stretch the tape too much, because this leads to its rupture. But the sanding belt slips over the pulleys at low tension and heats up very quickly. The tension force is set, depending on the strength of the base of the cutting tool and is determined by the arrow of its deflection with a slight pressure on it.

How correctly the tape runs can be checked by turning the pulley manually or briefly turning on the electric motor. The axis of the pulley, when the tape slips, is turned by the handle at a small angle and fixed with a locking device. After setting up the belt grinder, the dust extraction system is turned on, trial processing of parts is carried out and their quality is checked.

The manual feed belt sander can serve one worker. By moving the product relative to the cutting tool in the longitudinal direction, and turning the part around the axis, the operator sequentially brings into contact with the tape all the sections that form the surface to be machined. When slowing down or moving carelessly, grinding may form.

It is customary to grind individual parts of the part in several passes. It is possible to achieve high-quality alignment with the correct regulation of the pressure that is exerted on the ironing handle, and the speed of movement of the table and ironing. The pressure when approaching the edges must be reduced to prevent their grinding off. To increase the quality and productivity of grinding, small bars are placed on the table in a row, several pieces at a time.

Belt grinders with mechanical feed of products are served by two operators. One of them places the part on the conveyor, orients it along the width of the working table and directs the product under the clamping elements of the machine. Parts must not be moved sideways when being picked up by the conveyor.

It is not allowed to feed into the machine blanks that have an unequal thickness, and parts with gross surface defects. The feed rate and pressure of the clamping beam, as a rule, are not regulated during processing. The second operator takes care of receiving the finished parts and ensures that there is no unacceptable chamfering or grinding.

Production of a belt sander

The price of belt grinders from an industrial manufacturer is quite high, so when they are used infrequently, craftsmen involuntarily think about whether to buy equipment or not. An alternative to buying an expensive machine is to assemble it yourself. The main parts of the machine are the frame, rollers and engine.

The engine can be removed from an old washing machine. Cut out the bed from thick iron measuring 500 by 180 by 20 millimeters. Cut one side evenly milling machine for metal, it is required to mount the platform with the motor. Dimensions of the working platform - approximately 180 by 160 by 10 millimeters. Make a markup and drill three holes in the end face of a flat-cut bed. It is necessary to pull the platform to the frame with three bolts.

Remember that the longer the desktop is, the more options you will get when choosing a technological method for grinding and processing the product. If the length of the workpiece is less than or equal to the length of the worktable, then you can achieve perfect grinding much easier than when moving a large workpiece.

The engine must be tightly placed on the frame. It should have a power of about 2.5-3.0 kW and a speed of about 1500 revolutions per minute. If you choose a speed of about 20 m/s for the sanding belt, then the diameter of the drums should be about 200 millimeters. Thus, with sufficient engine speeds, a gearbox for a grinding machine is not required.

One of the two drums will play the role of a leader, which should be rigidly fixed to the engine shaft, and the other tension drum should rotate freely around a fixed axis on bearings. The table on the side of the driven drum must have a certain bevel, which will ensure a smooth touch of the sanding belt on the desktop surface, this is especially true for a glued joint.

You can make a tension drum and a drum that leads the sanding belt from chipboard. To do this, you need to saw blanks from the plate overall dimensions 200 by 200 millimeters and from them assemble a package of 240 millimeters. Square tiles or their package should be folded on the axis and machined to a diameter of about 200 millimeters.

Remember that in the center the diameter of the drum should be 2-3 millimeters larger than at the edges. With such a surface geometry, the flexible sanding belt will be located in the middle of the drum. The optimal width of the tape is an indicator of 200 millimeters. From a roll of emery cloth, which has a width of 1 meter, it is easy to glue 5 similar tapes.

It is necessary to glue the cutting tool end-to-end, placing a thin dense material from below, for example, a tarpaulin. Glue is recommended to use the highest quality that you can get. On the rollers, without fail, stretch the rubber, the width of which reaches 30 millimeters. Rubber can be taken from the cameras of a moped or bicycle.

On a home-made belt grinder, in addition to grinding wooden products, for which it is actually intended, it is very convenient to sharpen tools with cutting surfaces - chisels, knives, axes, secateurs. Another advantage of this grinder is the ability to work with parts that have a curved surface - for this you need to grind the workpiece with the reverse side of the working tape.

For finishing wood, metal or stone, you can build a belt sander with your own hands. The need for such processing arises quite often. It is needed not only to obtain even and smooth surfaces. With its help, you can remove various kinds of irregularities, bulges and depressions, peel off burrs, remove local defects, remove flash formed during welding, carry out internal grinding, etc.

Manual execution of such processing is very laborious and inefficient, and the cost of industrial grinding machines is quite high. Therefore, it is necessary to invent and build home-made structures, especially since they do not differ in particular complexity.

General information about the design of belt grinders

Belt grinders, with all the apparent diversity of their designs, have common features. An abrasive belt is used as a working tool in these designs. Most often, it is connected into a ring and placed between two rotating drums.

Usually there are two such drums: the first is the leader, and the second is the slave. The driving drum is driven by an electric motor through a mechanical transmission. Usually it is a belt drive. It is desirable to have a device that allows you to change the speed of rotation of the main drum, thereby providing a variety of processing modes.

The location of the sanding belt depends on the purpose of the sanding machine and can be any: vertical, horizontal or inclined. The tape is usually mounted on a frame, and workpieces can also be located there. IN makeshift designs the blanks are usually held by hand, although there may be other variations.

The length of the working part of the sanding belt depends on the size of the workpieces being processed. The grinding process is accompanied by the release of a large amount of dust, so the presence of an exhaust device is desirable. A tension roller is often used to adjust the degree of belt tension.

Depending on what it will be mainly used for Sander, it may have some design features. This applies to the diameter of the drums, the length and speed of the belt, its grain size, the design of the working table, etc. The main types of grinding are:

grinding curved surfaces;
leveling flat surfaces;
alignment of side edges or ends, as well as surfaces of bars, shields and similar parts;
grinding of intermediate layers of paint and varnish coatings.

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Homemade belt sander

The structural prototype of a homemade grinder was a conventional industrial design in which the belt is moved by the abrasive part outward over the flat surface of the desktop. The resulting grinder is distinguished from the industrial design by increased dimensions and a stationary installation.

Since a gearbox or belt drive complicates the design, an electric motor is used, the rotor of which makes 1500 rpm. The power of the electric motor should be about 2-3 kW. With a drive shaft radius of 10 cm, the linear speed of the belt will be about 15 m/s. As already mentioned, the reducer is not needed in this case. Adjustment of the speed of rotation in such a simple design is not provided.

The drive shaft is rigidly mounted on the motor shaft, and the second shaft tensions the belt. The tension shaft rotates on bearings sitting on a fixed axle to reduce friction. This axis can be shifted relative to the desktop in one direction or another, reducing or increasing the degree of tension of the sanding belt.

The desktop can be made from improvised materials: sheet metal or wooden beam. Its dimensions are determined by the distance between the axes of the shafts and the length of the abrasive belt. Near the shafts, the surface of the table must have bevels to ensure smooth contact of the tape (especially its junction) with its plane.

Both drums are easy to make yourself. Chipboard can serve as a material for their manufacture. Squares with a side of 20 cm are cut from the original plate. Their number should be such that the total thickness of the set is about 24-25 cm. Discs with a diameter of 20 cm are made from them on a lathe. There are two options for processing them:

You can grind each workpiece on the machine separately.
A more preferable option is to put the workpieces on the axis, clamp and grind them all together.

The groove should be carried out in such a way that the edges of the drums are a few millimeters smaller than their middle. This is necessary so that the abrasive belt is automatically installed in the centers of the drums.