How to grind a disk on a circular saw

Grinding circular saws

In domestic saws as a material for cutting plates the sintered tungsten-cobalt alloys of BK marks are used (BK6, BK15 etc.). The number indicates the percentage of cobalt). Hardness of ВК6 is 88,5 HRA, for ВК15. 86 HRA. Foreign manufacturers use their alloys. Hard VC alloys mainly consist of tungsten carbide cemented with cobalt. Alloy performance depends not only on its chemical composition, but also on the grain size of the carbide phase. the smaller the grit, the higher the hardness and strength of the carbide.

Carbide inserts are attached to the disc by high-temperature brazing. As a soldering material, in the best case, they use silver solder (PSr-40, PSr-45), in the worst case. Copper-zinc solders (L-63, MNMC-68-4-2).

Carbide tooth geometry

Tooth shape is divided into the following types.

Straight Tooth. Generally used in saws for fast, longitudinal cuts where quality is not of prime importance.

Oblique (beveled) tooth with left and right angles of the back plane. Teeth with different bevel angles alternate with each other, so they are called alternate bevels. It is the most common tooth shape. Depending on the size of the sharpening angles, alternate tooth saws are used for cutting a wide variety of materials (wood, chipboard, plastics). both lengthwise and crosswise. Saws with a steep backplane angle are used as scoring machines for double sided laminated boards. Their use prevents chips in the edge of the kerf. Increasing the bevel angle lowers the cutting force and reduces the danger of chipping, but also reduces the durability and strength of the tooth.

Teeth can be sloped not only on the back plane, but also on the front plane.

grind, disk, circular

Trapezoid tooth. These teeth have a relatively slow blurring rate compared with alternate teeth. They are usually used in combination with a straight tooth.

alternating with the last tooth and rising slightly above it, the trapezoid tooth performs roughing while the straight tooth following it performs finishing sawing. finishing. Saws with alternating straight and trapezoidal teeth are used for cutting double-sided laminated panels (chipboard, hardboard, fiberboard, etc.).), also for sawing plastics.

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Conical tooth. Tapered tooth saws are auxiliary saws and are used for notching the bottom layer of laminate to prevent it from being chipped as the main saw passes through.

in the vast majority of cases the front edge of the teeth have a flat shape, but there are also saws with a concave front edge. They are used for finish crosscutting.

Tooth sharpening angles

Sharpening angles are determined by the intended use of the saw. т.е. the material to be cut and in which direction it is to be used. Saws for longitudinal sawing have a relatively large rake angle (15°-25°). Cross-cutting saws have a cutting angle of γ normally varies between 5° and 10°. Universal saws designed for cross and longitudinal sawing have an average value of the front angle. usually 15°.

Sharpening angle values are determined not only by the direction of cutting, but also by the hardness of the material being sawn. The higher the hardness, the smaller the rake angle and back angle (less tooth sharpening).

The rake angle can be either positive or negative. Saws with this angle are used for cutting non-ferrous metals and plastics.

Basic principles of sharpening

When sawing massive workpieces, the side edges are also subject to rapid wear.

Over-blunted saws should be avoided. Cutting edge radius should not exceed 0.1 to 0.2 mm. Severely blunt saws not only result in reduced productivity, but also require several times as much time to sharpen as a normally blunted saw. The degree of sharpening can be determined both by the teeth themselves and by the type of kerf they leave behind.

Proper sharpening of circular saw blades consists in simultaneous providing of proper sharpness of cutting edge and maximum number of sharpening cycles which in optimal case could be up to 25-30 times. To this end, it is recommended that the carbide tooth be sharpened on the front and rear planes. In fact, you can sharpen the teeth along one front surface, but the number of possible cuts is about half as much as if you sharpen along two surfaces. The figure below illustrates why this happens.

It is recommended to make the last pass when sharpening circular saw blades along the rear surface of the tooth. Standard metal removal rates. 0,05-0,15 mm.

Before sharpening, the saw blade should be cleaned of debris such as tar and the sharpening angles checked. On some saw blades these are written on the disc.

Equipment and materials for sharpening circular saw blades

When using abrasive wheels (especially diamond wheels) it is advisable to cool them with coolant.

With increasing temperature microhardness of abrasives decreases. Increasing the temperature to 1000° C reduces the micro-hardness by a factor of nearly 2 to 2.5 compared to micro-hardness at room temperature. Increasing the temperature to 1300° C causes the hardness of abrasives to decrease by nearly 4-6 times.

Use of water for cooling can lead to rusting of parts and machine components. Soap and certain electrolytes (sodium carbonate, soda ash, trisodium phosphate, sodium nitrite, sodium silicate, etc.) are added to the water to eliminate corrosion.д.), which form protective films. Soap and soda solutions are most commonly used for conventional grinding, and for finish grinding. with low-concentration emulsions.

However, when sharpening circular saw blades at home with low sharpening intensity, it is not often necessary to cool the wheel. not wanting to waste time on it.

To increase the productivity of grinding with abrasive wheels and reduce the specific wear, you should choose the highest grit, which provides the required purity of the surface of the sharpened tooth.

To select the grit size of the abrasive, according to the stage of grinding, you can use the table in the article about grinding stones. For example, when using diamond wheels, grinding wheels with a 160/125 or 125/100 grit size may be used for roughing, and for finishing. 63/50 or 50/40. Grinding wheels with a grain size between 40/28 and 14/10 are used to remove the jagged edges.

Circumferential wheel speed when sharpening carbide teeth should be about 10-18 m/s. This means that when using a 125 mm diameter wheel the speed of the motor should be approx. 1500-2700 rpm. Brittle alloys can be sharpened at lower speeds in this range. When sharpening carbide-tipped tools, the use of harsh cutting regimes results in higher stress and cracks, and sometimes even in chipping of the cutting edges and increased wheel wear.

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When using circular saw blade sharpening machines, the relative position of saw blade and sharpening wheel can be changed in various ways. Displacement of one saw blade (motor with a disc is stationary), simultaneous displacement of the saw blade and the motor, displacement of the motor with the disc only (saw blade is stationary).

A large number of sharpening machines are available with various functions. The most complex and expensive programmable complexes are able to provide a fully automatic sharpening mode, in which all operations are performed without the participation of the worker.

In the simplest and cheapest models, after setting and fixing the saw in a position that provides the necessary angle of sharpening, all further operations. turning the saw around its axis (rotation on the tooth), feed for grinding (bringing it into contact with the wheel) and control the thickness of the metal removed from the tooth. are done manually by a worker. Such simple models are practical for home use, when circular saws are sharpened occasionally.

Saw disc grinding process with grinder | circular saw

An example of the simplest machine for sharpening circular saws is the system pictured below. It consists of two main assemblies. the motor with the wheel (1) and the slide (2) on which the saw to be sharpened is mounted. The swivel mechanism (3) serves for changing the angle of the blade (for sharpening teeth with a beveled front surface). The screw (4) moves the saw along the axis of the grinding wheel. This ensures that the desired rake angle is set. The screw (5) serves for setting the limiter to prevent the grinding wheel from sinking too far into the interdental space.

The process of sharpening circular saw blades

The saw is mounted on a mandrel, clamped using a tapered (centering) sleeve and nut and then set in a strictly horizontal position using mechanism (3). The bevel angle of the front plane is thereby ensured (ε1) equal to 0°. On disc grinding machines without an integrated angle scale in the tilting mechanism, this is done by means of a conventional pendulum-type angle gauge. In this case it is necessary to check the level of the machine.

Set the required rake angle by rotating the screw (4) of the mechanism which ensures horizontal movement of the mandrel with the grinding wheel. In other words, the saw is moved to a position where the front face of the tooth makes firm contact with the working surface of the wheel.

Use a marker to indicate the tooth at which the sharpening operation is to begin.

The motor is switched on and the front plane is sharpened. By placing the tooth in contact with the wheel and moving the saw back and forth a few times while pressing the tooth against the wheel. The thickness of the metal to be removed is controlled by the number of sharpening movements and the amount of pressure the tooth exerts on the grinding wheel. After sharpening one tooth, the saw is taken out of contact with the wheel, rotated by one tooth and the sharpening operation is repeated. And so on until the marker mark makes a complete circle, indicating that all teeth are sharpened.

Tooth sharpening beveled on the front surface. The difference between sharpening a beveled tooth and sharpening a straight one is that the saw must not be set horizontally, but tilted. with the angle corresponding to the bevel angle of the front plane.

Angle of inclination of the saw is set with the same pendulum angle gauge. First of all, a positive angle (8° in this case) is set.

Then sharpen each second tooth.

After sharpening half of the teeth the angle of the saw blade changes from 8° to.8°.

Once again, every other tooth is sharpened.

Sharpening on the back plane. To sharpen a tooth on its back plane you need to have a circular saw blade sharpening machine that makes it possible to position the saw blade in such a way that the back plane of the tooth is in one plane with the working surface of the abrasive disk.

If you do not have a sharpening machine for circular saw blades

Exactly maintain the necessary sharpening angles by holding the saw in your hands in the balance. a task impossible even for a person with a unique eye and an enviable hardness of hands. The most sensible thing to do in this case. To make a simple sharpening fixture that allows you to fix the saw in a certain position in relation to the wheel.

The easiest of these devices for sharpening circular saws is a stand, the surface of which is flush with the axis of the sharpening wheel. By putting the saw blade on it it is possible to ensure perpendicularity of front and back planes of the tooth relative to the saw blade. Making the top surface of the stand movable. one side hinged and the other. by mounting it on a pair of bolts that can be screwed in and out. it can be set at any inclination, making it possible to sharpen an oblique tooth along the front and back planes.

But in this case one of the main problems remains unresolved. keeping the same front and back angle of sharpening. The problem can be solved by fixing the center of the saw relative to the abrasive disk in the required position. One way to do it. Make a groove on the surface of the stand for the arbor, on which the saw is mounted. By moving the mandrel with the wheel along the groove, it will be possible to maintain the required front angle of the tooth sharpening. But for sharpening circular saws with different diameters or angles of sharpening, it must be possible either to move the motor or the stand and with it the groove. Another way to ensure the desired angle of sharpening is more simple, and is to install on the table stops fixing the drive in the right position. At the end of the article there is a video with a demonstration of such a device.

Device for sharpening circular saw blades with movable stops on the table

Quality control of sharpening

GOST 9769-79 establishes certain values of tolerances for sharpening parameters. End run-out of tooth tips must not exceed 0,2 mm (for saws up to 400 mm in diameter), radial run-out of tooth tips must not exceed 0,2 mm. 0.15 mm. Runout is checked with an ordinary pointer indicator.

Required tools

Circular saw blades can be sharpened with your own hands only if you have special tools. There is also a machine that allows you to automate the process and make it more efficient.

The following tools can be used to sharpen the circular saw blades with your own hands:

You can also use a circular saw blade sharpening machine, which does not require the above tools.

When should circular saws be sharpened?

It is quite important to determine when to sharpen circular saws. Severe wear and tear can make it impossible to carry out such work. There are three clear signals that are used to determine when a circular saw blade needs to be sharpened:

  • If there is smoke, the guard is heating up. The fixture usually has a special guard, which can get hot if the disc is blunted. It must also be noted that in special cases smoke may be produced as a result of excessive heat in the cutting zone.
  • Also with mechanical feed, when the pressure is adjusted with your own hands, a great deal of force must be applied to get the desired result.
  • When processing wood or other material, there are traces of carbon residue and a corresponding smell in the cutting area.
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In the above situations it is recommended to sharpen the circular saw disc.

Features of Tooth Shape. Grinding angles

Before describing how to sharpen a circular saw with pobedite tips, let’s go over the theory. The main feature of these discs is that the teeth are brazed with special tungsten carbide plates. They act as cutting elements.

Each sharpening face has four working surfaces:

At the intersection of these surfaces the cutting edges are formed. They wear out in the course of use, so sharpening comes down to removing a thin layer of the front and back of the file to sharpen the cutting edges.

The complexity of works on the restoration of geometry comes to the fact that the working surfaces of the tips are located at certain angles, which should be adhered to in the process of sharpening. And to do this, the working surface of the plate must be positioned correctly against the sharpening disk.

It is imperative that the four sharpening angles be considered in the process:

These angles can be different and depend on the purpose of the circular saw blade. Usually, all the necessary information for maintenance is indicated on the disc itself.

Since the inserts are made of carbide materials, you will need a special disc for sharpening pobedite. Diamond, CBN and silicon carbide wheels are used for this purpose. The first option is the most common, so it is not difficult to purchase.

How to know when it is time to sharpen a blade

When working with a circular saw, regardless of its purpose, you should understand. prolonged use will wear down the cutting edge. This process will take place regardless of what the saw is made of and what kind of fillings are on the teeth.

An indicator that it is time to sharpen the cutting part will be these signs:

  • You need more force to move the tool in the process. a sharpened blade cuts like butter, but a blunt blade requires more force to cut.
  • Transverse and longitudinal cuts are uneven, with jagged edges, because it is necessary to sharpen the saw teeth do not cut, but literally tear fibers. Because of this even a strong hand is not able to hold the tool evenly and instead of an even mowing line you get a sinusoidal pattern.
  • The cut of the tree will have a distinct charred look. since the teeth do not cut, but tear the fibers, the device will char the cut.
  • Sawdust turns out small, more like dust with a shade of rye loafa. a sharp tool has larger sawdust with sharp edges.
  • During operation there is a distinctive smell of fire. while the fibers are charring, there is smoke and the disc itself is getting very hot.
  • Even after a short time of operation, you can feel that the motor is getting very hot and it takes more time to cool down.
  • Visually, you can determine that the teeth have lost their sharpness, and the setting has lost accuracy, the individual elements have different degrees of deviation.

Sharpening methods

You can use a saw blade sharpening machine or handy tools.

There are three basic methods of sharpening, where a specific device is used, and the rules of processing discs are observed. Which of these is the right one, it is difficult to say. Once you have tried each technique, you can draw certain conclusions for yourself.

grind, disk, circular

Classic

This sharpening technique has been used for a long time, which is why it got its name.

  • Sharpening begins at the back of the circular saw blade.
  • The front part that runs into the material as it cuts remains in its unchanged position.
  • You can sharpen directly on the circular saw or remove the circular saw by placing it in a vise.
  • If you sharpen with a circular saw, always disconnect the machine from the power supply.
  • To secure the disk, use a pair of bars that will secure the wheel like wedges. The blades must be pressed firmly against the workpiece to prevent it from moving as you grind.
  • Use a felt-tip marker to mark the first tooth you will begin with.
  • Perform a certain number of strokes on the first tooth with the sharpening tool. Note their number.
  • For all subsequent teeth, repeat the same number and intensity of motions.
  • After completing the sharpening, be sure to check the performance of the saw, which you renewed with your own hands. If there is no extraneous noise, vibrations, and the disc machine behaves steadily, you have managed to do the job correctly.

Alternative solutions

Alternative ways of sharpening include the two methods we described above. They are quite effective and are therefore frequently used by craftsmen.

  • Full-face machining of the saw blade. Of all the sharpening methods, this one is the most precise and of the highest quality. This is due to the fact that for full profile sharpening, special sharpening machines are used. The special wheel is chosen according to size and goes over the entire tooth space of the blade in one go, overlapping the surface of the adjacent cutting edge. This method of sharpening circular saw blades avoids the possibility of tooth deformation. The only disadvantage of the sharpening method is that different saw profiles require different grinding wheels.
  • Tooth Edge Grinding. The popularity of this method of sharpening circular saw tools is explained by the fact that it can be used professionally and in ordinary household conditions. If sharpening is carried out with a machine, you will need to buy the appropriate abrasive wheels that match the parameters of your circular saw blades. But the optimal way for most circular saw owners is to use a home machining method. This is due to the fact that it is often not necessary to carry out a large amount of work, and all the processing of cutting edges is carried out by a nadphil. To effectively sharpen a product, it is sometimes enough to make 4-5 movements with a quality file. That way the teeth will acquire the necessary degree of sharpness.

Signs of a worn circular saw

Circular saws, if you follow all the rules of operation and careful maintenance, are reliable and durable, but, like any tool, from time to time requires preventive maintenance. If during the operation of this equipment became noticeable difficulties and appeared dark traces on the surface of the material, it means that the edges of the kerf are burnt from overheated teeth of the saw. If combined with fumes and smells from overheating of the engine cover, it is most likely that the tool needs sharpening right away.

Regular sharpening of circular saws has a big influence on the trouble-free operation of the electric motor.

A blunt disk increases the load on the mechanism many times and can lead to its complete failure. The main degree of wear is at the upper cutting edge of the teeth on the circular saw blade. To avoid tool blunting, you should regularly check the cutting edge rounding radius, which should not exceed 0,1-0,2 mm according to the rules. It is possible to determine if the circular saw needs urgent sharpening also by the shape of the kerf. Regular sharpening of the circular saw blade will not only prolong the term of non-failure operation of the equipment, but also increase productivity and reduce time and efforts spent for cleaning of absolutely worn tools.

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Types of circular saw tooth setting

The complexity of setting is due to the need to set the teeth at the same distance to the side. This can be accomplished by using the factory set circular sawframe. Each tooth should be set in the middle of its size. For different density of wood materials the degree of setting should be different, but without going into details, it can be said that for cutting soft wood is wider than for hard wood.

There are three basic methods of deburring:

  • The deburring type. This method is reduced to the fact that the tooth in two remains in its place without change, the rest are deflected in different directions. Such saw preparation is good for working with solid wood.
  • A variant of the classic set-up, where the saw teeth are alternately set to the right and left. This universal method can be applied to almost all types of saws.
  • The so-called wavy setting, the hallmark of which is the setting of the teeth not at a strictly defined distance from the center, but at different distances with a deviation of within 0.3-0.7 millimeters.

When it is time to sharpen?

Professionals recommend sharpening tools regularly. But how do you know when it is time to sharpen?? To do this, you need to pay attention to such signs:

appearance of smoke and a specific burnt smell;

the need to apply force when working with the tool;

A large number of imperfections on the workpiece after cutting;

Rounding of the disk edge when viewed under a magnifying glass.

If one or more of these symptoms occur, you should take the tool to a sharpening machine or sharpen it yourself.

Types of cutting teeth

There are four planes on the tooth surface. one at the front, one at the back, and two at the sides.

At the moment of intersection they create a single cutting edge thanks to which surfaces are sawn.

  • Straight tooth. Most commonly used only for quick rip cuts. Quality and precision are of little or no importance in this type of sharpening.
  • Tooth bevel. The back plane of such a part is tilted to the right or left. Saws often have these teeth alternate, causing them to be called “alternate-slotted. These teeth are the most commonly used in tools. Angle size can be different, it has to do with the surface finish. wood, chipboard, plastic. They are used for both longitudinal and crosscutting movements. The large angle on the tools is used when cutting double-sided laminated boards. This helps to avoid chipping of the material. The more beveled the angle, the easier it is for the saw to pass over the surface. But it significantly increases the likelihood of tooth breakage. On some products, the teeth are not only angled at the back, but also at the front.
  • Trapezoid tooth. The main advantage of this type is that the edge blunts slowly. But they are rarely used alone, usually alternating with the straight tines. During the operation of the device, the trapezoidal teeth are located above the straight ones, so they take on the main (rough) work of sawing. Straight teeth do the finishing work. This saw design is used for sawing plastic, chipboard and fiberboard.
  • Conical tooth. This type of tooth is considered additional, because it only helps to notch the bottom part of the material (most often laminate). This design protects the surface from splintering and cracking. Tapered teeth usually have a straight leading edge, but it can also be concave. This type is used for finish cuts.

Important! Each type of tooth needs to be ground very thoroughly. They should not be sharpened at the same angle.

Selecting the cutting teeth sharpening angle

Links on the cutting attachments have a working area, which has an appropriate sharpening angle. Depending on the type of teeth, a blade can be used in one sawing direction as well as in two. When the links are blunted on one part, it is necessary to turn the disk, and continue working in the opposite direction. However, not all circular saw blades can be sharpened in this manner, e.g., blades with beveled links are not suitable for sharpening.

If you perform the sharpening of the circular saw disc with your own hands, you need to understand that depending on the direction of the cut, you need to consider the angle of sharpening.

grind, disk, circular
  • If you plan to saw wood in the longitudinal direction of the fibers, the angle of sharpening on the links should be 15-25 degrees
  • If wood is sawn transversely, the sharpening angle is reduced to 5-10 degrees
  • Universal angle of sharpening is considered to be 15 degrees. Circular saw blades with these teeth can be used not only lengthwise but also crosswise

Angle grinder into Circular saw (Дисковая пила из УШМ)

When sharpening the teeth on circular saw, angle grinder and circular saw blades and discs it is necessary to take into account one more important factor. it is the density of the material to be sawn. The lower the density, the higher the sharpness of the tooth. If the circular saw is used for sawing plastic or plastics, the angle of the blade should be negative.

Circular saws are used everywhere in construction. Many jobs require making changes in the size of the building materials used, creating notches and more. A circular saw makes it possible to quickly cut through a wide variety of materials at a very high cutting rate and produces the best quality of cut. Continuous use of the equipment in question determines that the cutting tool begins to blunt, it has a significant impact on the efficiency of work performed and its quality. That is why many people think about how to sharpen circular saws with their own hands. After all, the ability to qualitatively perform such work will save significantly.

Sharpening of carbide-tipped tools

Sharpening circular saws with pobedite tips often causes problems. Sharpening with standard abrasives takes a very long time and if the material is overheated it can cause a “tempering” phenomenon. Of course, machining with a diamond tool is much faster, but its cost is very high. It will be much more economical to buy pobeditovogo disk.

Every craftsman approaches this problem on a strictly individual basis. To get the correct sharpening angles for carbide-tipped circular saws, you will definitely need a machine.

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