DIY belt grinder drawings. How to make a simple polishing machine and what is needed for this? Video: gluing grinder tape with PVA glue

Belt sander

What is a grinder made of?

Where can I get the tape?

For finishing wood, metal or stone, you can build a belt sanding machine 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, remove burrs, remove local defects, remove burrs formed during welding, carry out internal grinding, etc.

Manual execution of such processing is very labor-intensive and low-productivity, and the cost of industrial grinding machines is quite high. That’s why we have to come up with and build homemade structures, especially since they are not particularly complex.

General information about the design of belt sanders Belt grinding machines, with all the apparent diversity of their designs, have common features

Usually there are two such reels: the first is the leading one, and the second is the driven one. The driving drum is rotated electric motor through a mechanical transmission. This is usually a belt drive. It is desirable to have a device that allows you to change the rotation speed of the drive 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 anything: vertical, horizontal or inclined. The tape is usually mounted on a frame, where the workpieces can also be placed. IN homemade designs the workpieces 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 it is advisable to have an exhaust device. To adjust the degree of belt tension, a tension roller is often used.

Depending on what the grinding machine will be primarily used for, 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 work 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, panels and similar parts;
• grinding of intermediate layers of paint and varnish coatings.

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Homemade belt sander

The design prototype for a homemade grinding machine was a conventional industrial design in which the belt moves with the abrasive part outward over the flat surface of the work table. The resulting sander is distinguished from the industrial design by its increased dimensions and 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, a gearbox is not needed in this case. There is no provision for adjusting the rotation speed in such a simple design.

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

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

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

1. You can grind each workpiece separately on the machine.
2. A more preferable option is to place the blanks on the axle, clamp and grind them all together.

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

If you need a grinder for occasional work with wood and don’t want to spend money on professional equipment, you can assemble a power tool yourself using scrap materials, as in this project.

Materials

To make a grinding machine with your own hands you will need:

• suitable electric motor;
• fasteners;
• grinding disc;
• pieces of plywood;
• sandpaper;
• drill;
• saw;
• roulette.

In this project, the basis of the tool was an old electric motor from air compressor. It is powerful enough for the finished product to work no worse than special woodworking equipment.

Step 1. Be sure to attach the purchased grinding disc to the existing engine. This will help you decide on the parameters of the pedestal for the motor.

After careful calculations, assemble the base from boards or pieces of plywood. Be sure to secure the motor to it.

Step 2. Cut out a base for the disc from plywood and carefully sand the edges of the cuts with sandpaper. Using the motor pulley, mark the holes in the center of the disc. Drill them with a drill, and bolt the pulley and round base from plywood to each other.

Step 3. Basically, the grinding tool is ready, you will need to fix it on plywood base the disk itself, and you can work calmly. Or, as in this project, you can assemble a box from leftover lumber to make the power tool look nice, and also display a tool start button on its front part. Before assembling the box, be sure to make careful calculations.

You should work with the resulting tool extremely carefully and in compliance with safety rules. The rotation speed of the disc is high and there is a chance of wearing off your nails or injuring your hands during processing small parts, high.

Grinder (English) literally – crusher. Meat grinder is a meat grinder, rock (stone) grinder is a stone crusher; stick (wood) grinder – garden crusher of branches and twigs into chips. But there is also a completely unambiguous meaning of the word grinder: in mechanical engineering and metalworking it is grinding machine. A useful household item. For example, it is impossible to guide a dull meat grinder knife on a whetstone manually. On a manual knife sharpener - somehow possible, having solid working skills. And on the grinder - no problem. The same applies if you need to polish a part of a complex shape without disturbing its profile. Or just sharpen scissors or a professional knife. It is best to edit various types of wood and metal cutters on a grinder. It is quite possible to design and assemble a grinder with your own hands, without having complex equipment and skills to work with it. In terms of money, this will mean savings of 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 external turning at all. For example, how to make a simple grinder literally out of trash, see the video below:

Video: DIY belt grinder made from trash

Or another option, how to make a stronger and more durable grinder from scrap metal:

Video: scrap metal grinder

Disc or tape? And drive

There are almost more types of grinding machines used in industry than lathes. The emery known to all craftsmen - a motor with a pair of grinding wheels (or one wheel) - is also a grinder. For yourself at home, it makes sense to make either a disk end grinder (plate grinder) or a belt grinder. In the first, the abrasive is applied to a rotating hard disk; in the second - on an elastic band running around a system of pulleys and rollers. The disc type is more suitable for grinding simple wooden parts and coarse or medium clean metal parts. Using a belt grinder, it is also possible to produce precise and clean finishing of profiled parts of complex shapes, incl. large-sized, see below.

A disk grinder is very easily obtained from the same emery or a motor of suitable power, see below. You need to order an adapter from the electric motor shaft to the shank of a metal-based grinding disc. Or under a clamping chuck, then on the same motor it will be possible to build a mini lathe, see figure:

A worn-out “plate” is suitable: a disk made of thin (4-6 mm) fibrous plastic is glued to 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

Note: a 100-200 W drive uses a mini-belt grinder (see below) for precise knife dressing, grinding/polishing jewelry and so on.

A drill or screwdriver as a grinder drive is also convenient in that it allows you to quickly change the speed of movement of the abrasive (see below) using a standard speed controller. You just need, firstly, to make a holder for the drill that rigidly fixes the tool. Secondly, an elastic transition coupling from the drill to the disc shank, because It is difficult to achieve their precise alignment without special equipment, and runout will negate the accuracy of processing and can damage the drive tool.

Drawings of a 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 a grinder are an order of magnitude lower than, say, in a lathe, the drill holder for it can be made of hard 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 advisable to use a drill without an impact mechanism and with a steel shell on the neck (for installing the front handle).

coupling

For the adapter coupling, you will need a piece of steel rod (not necessarily turned) of the same diameter as the shank of the grinder drive shaft, and a piece of PVC-reinforced hose (garden irrigation) with a clearance such that it stretches tightly over the rod and the 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 reliable clamping in the drill chuck. After assembling the coupling in place, the hose on the shank and rod is tightened tightly with clamps; can be wired. Such a coupling completely counteracts the misalignment of the drive and driven shaft up to 1-1.5 mm.

Tape is still better

A belt grinder allows you to do everything a disk grinder can do, and much more. Therefore, next we will focus on how to make a belt sanding machine with your own hands. Amateurs, focusing on industrial designs, sometimes make very intricate grinders, see figure:

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

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

Kinematics and design

As mentioned above, there are many designs of grinders. When considering what and how to build a grinder for yourself, it is better to focus on industrial designs designed to be fully mechanized for precise and clean grinding of large-sized profiled parts: once it “sands” the blade of an airplane propeller or wind turbine properly, it can handle any other work.

Kinematic diagrams of grinders for the specified purpose are shown in Fig.:

Basic kinematic diagrams of belt grinding machines (grinders)

Pos. A is the most complex and perfect, with three rocker arms. If the length of the tension roller rocker arm is approx. 2 times less than the working one, then by adjusting the tension of the springs, it is possible to achieve 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 of different lengths. Secondly, in the same way you can quickly change the belt tension for different operations. The working branch of the belt 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.

The scheme with a coaxially swinging rocker arm (item 2) is simpler, cheaper and in terms of processing accuracy is not inferior to the previous one, if the length of the rocker arm between the axes is at least 3 diameters of the workpiece. To reduce the profile by grinding, the stroke of the rocker arm is limited by stops within 10 degrees up and down. The pressure of the belt to the part is most often gravitational, under the weight of a rocker arm with a bypass pulley. The tension of the belt can be quickly changed within certain limits by pulling the rocker up with a weak adjustable spring, partly compensating for its heaviness. The grinder of this design can work as a grinder for small parts from a sliding table. In this case, the rocker arm is rigidly fixed horizontally, and the working surface of the belt will run around the bypass pulley. For example, the quite popular BTS50 grinder is made according to the scheme with a coaxial rocker. The disadvantages of the scheme are, firstly, the technologically complex rocker arm joint, which is coaxial with the drive shaft. Secondly, the need for an elastic band: if you make the idler pulley sliding and spring-loaded, the processing accuracy decreases. This drawback when processing small parts is completely eliminated by an additional tension roller, see below.

The scheme with one misaligned rocker arm is used quite rarely in industry, because in principle, it does not allow achieving uniform tape tension. However, it gives 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 circuit from the point of view of an amateur master. And then we’ll try to figure out how to make a grinder belt ourselves and do without custom-made turned parts.

3 rocker arms

Competent amateurs build their grinders exactly according to the scheme with 3 rocker arms, on the left in Fig. below. Not all propeller blades can be ground, but in this case another advantage of this scheme applies: if the grinder is used as a vertical grinder, then the working branch of the belt 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 design is also widely used (in the center) for the same reasons. Repeating them yourself in most cases is quite possible. For example, the drawings of the KMG grinder, popular abroad, can be downloaded.

The dimensions are, however, inch - the machine is American. For the drive, in any case, it is possible to use an angle drill-grinder (on the right in the figure, 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 an asynchronous motor at 2-3 speeds from an unusable washing machine with a horizontal tank. Its advantage is low speed. This makes it possible to make a large-diameter drive pulley and thereby eliminate belt slippage. If the belt slips during operation, it is almost certainly a damaged part. Most washing machines with 2-3 speed asynchronous motors for 220 V are Spanish. Shaft power – 600-1000 W. If you come across one, don't forget about the standard phase-shifting capacitor bank.

Coaxial rocker

IN pure form Amateurs do not make grinders with a coaxial rocker. A coaxial hinge is a complicated thing; you can’t make an elastic band yourself, and store-bought ones are expensive. Grinders with a coaxial rocker are most often used at home in the version for small precision work from a table, i.e. with a rigidly fixed horizontal rocker arm. But then the need for a rocker arm as such disappears.

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

Its features are, firstly, an overhead bed for the tape (item 7), which significantly expands the possibilities of use. For example, the plane iron is straightened on this grinder with an angular stop literally by itself. IN in this case the grinder works, so to speak, like a self-propelled whetstone (emery block). Having removed the bed, we get a grinder with an elastic band for precise grinding/polishing of rounded small parts. Secondly, the tension shaft (item 12). By clamping it to the groove with nuts, we get a relatively fixed tension of the tape for working with the bed. And after releasing the nuts, we switch the grinder to the gravitational belt tension mode for fine work. Drive - not necessarily through a pulley (pos. 11). You can screw it directly onto the drive shaft shank (item 16) from the drill through the adapter coupling, see above.

A specialized tool grinder (for example, for guiding and straightening turning tools) generally loses any semblance of the original design. A high-speed motor is used for it (200-300 W is enough power). The drive pulley is, accordingly, of small diameter. The bypass pulley, on the contrary, is made larger and heavier for inertia. All this together helps reduce tape runout. The tension roller for the same purpose, plus for greater uniformity of belt tension, is moved further away and spring-loaded with a long, not very strong spring. How to make a grinder for processing incisors, see the video below.

Video: grinder for making cutters

One rocker

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

In this case, the original scheme is also modified: the rocker arm is rotated 90 degrees, moved upward and spring-loaded, on the left in Fig. It turns out to be a simple vertical grinder. And, importantly, it works without problems with homemade non-stretchable tape. A tension spring (in the center) or a compression spring can provide tension to the tape. Its strength is not so important, as long as the tape does not bend excessively during operation. No adjustments are required during use.

Consumables and parts

The only consumable material for a belt grinder is a tape (not counting grease for bearings and hinges. The tape can be ordered to the desired length (see at the end), but you can also make it yourself from textile-based emery cloth. It is highly desirable - flexible, unimpregnated. In general The procedure for making a grinder belt with your own hands is as follows:

• We cut the workpiece - a strip of the required 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 outline the mandrel with the workpiece inside out.
• We bring the ends of the workpiece exactly end to end and securely fasten them.
• Place a piece of glue stick for a hot glue gun on the joint.
• Heat with a construction hairdryer until the glue melts.
• We apply a patch of thin fabric to the joint.
• Press with 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 for the patch. It is very durable, but just try running your finger across a PET bottle. Not very slippery? Rough PET film cannot be stretched under tension even over polished metal. And instead of a patch, it is better to seal the back of the tape with a continuous strip of PET film with an overlap of 2-3 cm. The runout 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 blank skin.

Second, insert the finished tape into the machine and grind something indecent with it without strong pressure. The scar on the seam will be sealed, and the tape will become no worse than the branded one.

But the most important thing is elasticity best glue for gluing the grinder tape, it is not expensive and difficult to use thermo- or mounting, but ordinary PVA. If the tape is covered with a lining along the entire length of the back, then its PVA strength will be more than enough. How to glue PVA grinder tape, see video

Video: gluing grinder tape with PVA glue

Pulley

The generatrix (side surface in cross-section) of the grinder drive pulley must be straight. If you use a barrel pulley, the belt will bend like a trough along its entire length. The rollers prevent it from slipping, see below, but the generatrix of the pulley must be straight.

A pulley for a grinder that is not intended for particularly precise work, firstly, does not have to be turned. In a scheme with 3 rocker arms, the beating of the belt from its misalignment will go out on the rollers before it reaches the working branch. In a simple vertical grinder, the beating of the belt 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

Secondly, the pulley, rollers and, in general, all the parts of a home grinder can be made from plywood. In production, this is certainly not an option, even if a 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 it and itself. But you won’t be running a grinder at home every day in 3 shifts. And no tape slips along the plywood pulley. Incl. homemade. So you can safely make a grinder pulley from plywood:

Video: pulley for grinder made of plywood

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

Video: what wheel is needed for a belt grinder

Rollers

The rollers of the grinder, oddly enough at first glance, are its most important parts. 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 grinder for incisors. Only barrel rollers can cope with this task, see below. But the “trough” of the belt after any roller must straighten before it reaches the working area.

Rollers with flanges (sides, edges) will not hold the tape. The issue here is not only and not so much with the misalignment of the roller axes: the grinder belt, unlike the drive belt, must withstand the loads from the parts being processed without slipping. If you make videos with flanges, then if you barely touch the tape with something, it will creep 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 for turned steel and not less than 35-40 mm for plywood. The tension roller (the probability of the tape slipping from it is greatest), if the working branch of the tape does not come off it, can have a diameter of 0.7-1.2 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 processed cleanly, see e.g. track. video:

Video: barrel roller for grinder

Not every turner can turn a profile roller barrel exactly according to GOST even on a machine. Meanwhile, there is a way to make videos for the grinder without significant difficulties. The same PVC-reinforced garden hose will help out, on the right in Fig. previously. A section of it is pulled tightly onto a roller blank with a straight generatrix and cut off with a margin along the edges to the thickness of the hose wall. The result is a roller with a complex profile of the generatrix, which holds the tape even better and gives it a smaller “trough”. Don't believe me? Try to get to an airplane or missile graveyard and dig around in them. You will find rollers with exactly the same generatrix profile. Just in mass production complex profile rollers are much more expensive than Type 3 barrels.

And another option

All critical parts of the grinder - a solid belt, pulleys with a coating that prevents it from slipping, rollers - can be purchased separately. They won’t be that cheap, but still not thousands of foreign ones and not dozens of native leather jackets. The remaining parts of the grinder, either flat or from corrugated pipes, are made using a regular tabletop drill or drill. Here's where you can order parts for the grinder:

• //www.cora.ru/products.asp?id=4091 – tape. Lengths and widths are made according to the customer's wishes. Consult on abrasives and processing modes. Prices are reasonable. Delivery time - questions to Ruposhta.
• //www.equipment.rilkom.ru/01kmpt.htm – spare parts (components) for grinding machines. There is everything, the prices are divine. Delivery - see previous.
• //www.ridgid.spb.ru/goodscat/good/listAll/104434/ – the same, but foreign production. Prices are higher, delivery is the same.
• //www.pk-m.ru/kolesa_i_roliki/privodnye_kolesa/ – drive wheels. You can find ones suitable for grinding.
• //dyplex.by.ru/bader.html, //www.syndic.ru/index.php?option=com_content&task=view&id=36&Itemid=36 – spare parts for grinders. They do not make ribbons to order - choose from the catalogue. Rollers without axles; axles sold separately. The quality is impeccable, but everything is very expensive. Dispatch - within 2 weeks to the border. Then - their customs, our customs, Rusposhta. Total approx. 2 months It may not arrive if some local bureaucrat considers the product sanctioned. In this case, there are no problems with the return of payment due to the complete absence of real opportunities for the average citizen to receive one.
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