How to correctly sharpen a brush cutter blade

How to correctly and at what angle to sharpen a circular saw blade

The use of circular saws is especially common in construction. Most work needs cutting and reshaping of finished materials. Circular saw helps to cope with such tasks quickly and get a quality result. But a tool cannot last forever, sooner or later it can get blunt. This is why you need to know exactly how to sharpen your saw teeth in the home.

Checking a circular saw for wear is an important issue that requires special attention. Deep damage makes it impossible to sharpen the wheel. There are three basic signs that tell you that the saw needs sharpening or replacement:

• Severe heating of the blade guard and smoke formation. A circular saw has a special guard that signals that the saw has blunted through heat. In particularly severe situations, smoke may come out of it.
• Sometimes the saw is designed with a mechanical feed (if you have to adjust the pressure manually). In this situation, wear can be noticed if the pressure has to be increased.
• If when sawing the wood there is soot and a strong, unpleasant odor on the workpiece.

All situations described above tell the user that it is time to sharpen.

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.

When they intersect each other, they create a single cutting edge that is used to cut surfaces.

• Straight tooth. It is most often used only for quick longitudinal sawing. Quality and precision are of little importance in this type of work.
• Bevel Tooth. The back plane of such a part is tilted to the right or left. On saws, these teeth often alternate, causing them to be called “alternate-sloped. These teeth are used in the tool most often. angles vary in size depending on the substrate being cut. wood, chipboard, plastic. They are used for both longitudinal and transverse movements. Large angles of inclination on these tools are used when cutting double-sided laminated boards. This helps prevent material chipping. The larger the beveled angle, the easier it is for the saw to pass over the surface. But it greatly increases the likelihood of tooth breakage. On some products, the teeth are slanted not only at the back, but also at the front.
• Trapezoidal Tooth. The main advantage of this type is that the edge blunts slowly. But they are seldom used separately, usually alternated with straight teeth. During operation, the trapezoidal teeth are positioned over the straight ones, so they take on the main (roughing) work of sawing. Straight teeth do the finishing work. This saw design is used for sawing plastic, particleboard and fiberboard.
• Conical tooth. This type of tooth is considered supplementary because it only helps to cut the bottom of the material (most often laminate). This design allows to secure the surface from chipping and cracking. Tapered teeth usually have straight leading edge, but it can also be concave. This type is used for finishing a cut.

Important! Each type of tooth requires a thorough sharpening. Do not turn them at the same angle.

Sharpening with a machine tool

If there is an opportunity to buy a special machine, then the process under consideration can be carried out with maximum efficiency. The machine is compact and can be used at home.

Particular attention is paid to the choice of abrasive wheel. In this case, note the nuances below:

• The carbide disc is difficult to sharpen.
• When selecting, look for grinding wheels made of elbor, diamond or green silicon carbide.

Sharpening with professional equipment is very simple. A special retainer is used to clamp the disc. It is created with the design features of the wheel in mind. Let us pay special attention to the fact that with the use of special machines it is very easy to sharpen circular saws with observance of the necessary indicators. In this case the error is minimal. This is due to the fact that the design has a special angle indicator meter. In order not to make a mistake at the time of work which teeth have already been machined, you should mark the starting point with a marker.

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During long-term use, carbide-tipped circular saws can lose their initial qualities. But this does not mean that you should buy a new cutting tool. In most cases sharpening can be done at home, using any suitable machine.

How to determine the sharpening angle of a circular saw

Carbide tip geometry

It is best to have a reference template that can be used to readjust the cutting edge geometry. Often it is made of thin-walled stainless metal, less often. of thick cardboard.

Carbide tines are made according to GOST 9769-79. But their geometry and geometric dimensions are determined by the manufacturer based on the purpose of the saw. If you do not have a template. you need to determine the required angles of sharpening by yourself. It is advisable to use a pendulum-type angle gauge for this.

The technology of making a template with your own hands.

• Take a new flute disc that is identical to the blunt disc.
• Draw precise contours on a hard piece of cardboard.
• Determine the initial geometry of the carbide tips with a pendulum-type angle gauge.
• Write the data down on a template.

It can then be used for self-sharpening on a machine tool or provided as a template for companies providing similar services.

Additionally, it is advisable to compare the data obtained with the reference data. In saws for longitudinal shaping the front angle is usually 15°-25°. For transverse models, this ranges from 5° to 10°. In universal models the cutting edge angle is 15°.

Important to remember that the rake angle can be negative. Similar models are used for cutting plastic sheets and non-ferrous metals.

Sharpening is necessary

Sharpening of circular saw blades is required when work can no longer be carried out. This can be understood from the three signals:

• Heat of the blade guard. Smoke appears from underneath, exits the cutting zone.
• The need for additional forces when feeding the workpiece at the time of cutting.
• Wood comes into contact with the cutting metal and gives off a burning and smelly odor.

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The geometry of the carbide tines

A carbide tooth has four working planes. the front (A), the back (B), and two auxiliary side planes (C). Intersecting each other, these planes form the cutting edges. the main (1) and two auxiliary (2 and 3). The given definition of tooth edges and bevels is given according to GOST 9769-79.

The following tooth shapes are distinguished.

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

Angled (beveled) tooth with left and right angles of slope of the back plane. Teeth with different angles of inclination alternate with each other, therefore, are called “cross cut saws. This is the most common tooth design. Depending on the size of the sharpening angles, alternate-tooth saws are used for sawing a wide variety of materials (wood, chipboard, plastics). both longitudinally and transversely. Saws with a steep slope angle of the back plane are used as undercutting saws when cutting double-sided laminated boards. Their use prevents chipping of the coating on the edges of the kerf. Increasing the bevel angle lowers the cutting effort and reduces the danger of chipping, but at the same time reduces the strength and durability of the tooth.

Bevel tooth with beveled back plane

Teeth can have not only a sloping back plane but also a sloping front plane.

Oblique tooth with beveled front surface

Trapezoid tooth. Feature of these teeth is relatively slow blunting rate of cutting edges in comparison with alternately beveled teeth. They are usually used in combination with the straight tooth.

Alternating with the last tooth and slightly rising above it, the trapezoidal tooth performs rough sawing, and the straight tooth following it performs finish sawing. Saws with alternating straight and trapezoidal teeth are used to cut double-sided laminated panels (Particleboard, Fibreboard, etc).) as well as for sawing plastics.

Conical tooth. Saws with a bevel tooth are auxiliary and are used for cutting the lower layer of the laminate, preventing it from chipping when the main saw passes over.

In the vast majority of cases front teeth are flat, but there are also saws with concave front edge. They are used for finish crosscut sawing.

Tooth sharpening angles

There are four basic circular saw blade cutting angles which, along with the tooth shape, determine the performance of the circular saw blade. These are the anterior angle (γ), the posterior angle (α) and the anterior and posterior bevel angles (ε1 and ε2). The sharpening angle (β) is of secondary importance as it is set by the front and rear angles (β=90°-γ-α).

The values of the sharpening angles are determined by the purpose of the saw. t.е. what material it is intended for and in what direction it is to be cut. Saws for longitudinal sawing have a relatively large rake angle (15°-25°). Cross cut circular saw blades have an angle γ of between 5° and 10°. Universal saws intended for cross and longitudinal sawing have an average value of the front angle. usually 15°.

Sharpening angles are not only determined by cutting direction, but also by the hardness of the material to be sawn. The higher the hardness, the smaller the leading and trailing angles should be (less sharpening of the tooth).

The rake angle can be not only positive, but also negative. Saws with this angle are used for cutting non-ferrous metals and plastics.

Tools

To do the sharpening of the saw with your own hands is allowed only with the use of special devices. There is a sharpening machine for this, which helps to carry out the process on an automatic, not manual. The result is then more accurate.

In addition, other improvised devices are used for sharpening:

There is no substitute for the aforementioned tools. If at least one of these is not available, sharpening is not possible.

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How to properly sharpen a circular saw!

The circular saw needs to be sharpened on the front and back edge! In the picture below we have shown the tooth of the new saw (extreme left). In the process of sawing wood, the sharp cutting edge of the tooth is blunted, and if we look at it under magnification of several times, we can see that the front edge has a rounded shape. To make it flat again we have to grind one of the tooth flanks: grind that circle, and the edge will be sharp again.

To do this, we can sharpen it only on the front edge of the tooth (which is wrong) and we will have to grind a lot, or we can distribute the amount of grinding evenly. on the front edge of the tooth circular saw tooth and on the back edge of the tooth circular saw tooth. That is, it is recommended to sharpen the circular saw along the front and back edge of the tooth

As a result we, sharpening circular saws on the front and the back side of the tooth, we can significantly increase the life of the tool: we can sharpen it more times, which means it will work longer and pay back the money invested in it when buying. And often, circular saws of large diameters for multi-rip saws and log saws are very expensive, and such saws are not bought one piece at a time.

To sharpen circular saw blade it is necessary to use a specialized sharpening machine, preferably with CNC, which has a high precision. The sharpening is performed in several steps:

• First it is absolutely necessary to clean the saw from wood resins, for which special demineralizing technical fluids (alkalis with sodium) are used.
• Then the circular saw is sharpened along the leading edge. The saw is sharpened in several passes with a small amount of grinding in one pass. The saw is sharpened in 2-3 laps, this is determined by an experienced operator.
• The third step is sharpening the saw along the back edge of the tooth. Also in several passes.

We strongly recommend that circular saws be sharpened in specialised service workshops using CNC machines.

In this case the operator can set all necessary sharpening angles of the circular saw tooth on the control panel:

• cutting angle of the cutting edge,
• angle of sharpening of the rear edge if the rear edge is of variable bevel. this too can be set on the control panel.
• Angles of trapezoidal teeth, etc.п.

A quality tool sharpening is the life of a circular saw. If you have been able to sharpen your saw properly, it will not lose its original cutting edge and will function like new.

How to sharpen circular saw blades

A machine for sharpening circular saws with a file

Any sharpening machine can be used to shape a new cutting edge. It is important to choose the right emery wheel first and sharpen the edge with it. To do this, use corundum or diamond models.

The best option is to use special equipment designed for this work. But its high cost makes it impractical in many cases. An alternative way is to use a sharpening machine with the possibility of changing the angle of the corundum disc.

Under no circumstances should you do the sharpening by hand yourself. Firstly. it takes a very long time. Second. the result will not meet standards. If you can not sharpen the wood saw blade yourself, it is recommended to use the services of specialized companies.

Professional sharpening of circular saws with your own hands is performed according to the following rules:

• The main deformation occurs on the top edge of the tooth. Rounding of edges from 0,1 to 0,3 mm takes place. This is where you should start processing;
• The sharpening is performed on the leading and trailing edges. This will ensure that the procedure can be repeated up to 25 times;
• the value of removal must not exceed the value of 0,05-0,15 mm;
• the level of machining of the front and rear edges must be the same.

After sharpening wood discs is completed. it is recommended to finish it with fine-grained emery paper. It can be done manually or with a special machine.

Specialists advise to use special corundum discs, the end face of which has a specially shaped groove. It will make the procedure easier to perform.

Basic rules

When sharpening a wood saw with their own hands requires concentration, good eye and skills to work with file. Despite the apparent complexity of the process, if you follow the recommendations, this manipulation can be done quite simply, although not quickly. To sharpen a hacksaw at home, you need to spend an hour or two of time, you can cope even faster if you have a hand.

Hacksaws are also sharpened with the angle grinder, but many craftsmen treat this method negatively. First of all, it is not safe, and secondly, you can damage the cutters more than sharpen them.

Preparing

The blade must be firmly clamped in a vice. You can also sharpen on your lap or on a stool, but it is not comfortable to hold a hacksaw this way. The place where you sharpen the hacksaw should be well lit, and gloves should be worn for safety purposes. Nothing distracting, like a TV set, should distract you from your work.

To restore the performance of a joinery tool, only a file of good quality should be used. Usually a three-sided file is used, but a special square file is available for the small prongs of a hacksaw.

The edges of the cutters should always be deburred with a file or file that has a fine velvet notch. If a used file has to be used, it should be cleaned beforehand, using a steel brush.

A small layer of coating should be removed from the cutters. While sharpening them, it is important that the file does not slip, but that it adheres well to the workpiece. If not, it means the file is not suitable for sharpening, or the cutters are overhardened. Use another tool for sharpening. If the second attempt is unsuccessful, it is advisable to change the hacksaw.

Sharpening

To sharpen a wood hacksaw properly with a file, its handle is clamped with the right hand and the left hand holds the end. The tool should be angled towards the teeth of the blade (as it bevels). Apply pressure evenly, smoothly and only in a certain direction (usually away from yourself).

If possible, it is advisable to make sure that the removed metal layer is of the same thickness. For this it is recommended to move the tool an equal amount of times and with an equal amount of pressure. That will keep the height, pitch, and size of tooth corners after machining.

Any burrs that may appear on the tooth edges should be removed with a wet burr or with a file with a velvet cut. If they are left on, they will reduce the sharpness of the teeth and break out when sawing wood materials, which will worsen the quality of the manipulation performed.

When sharpening is complete, check the sharpness of the teeth by sawing a piece of wood. If when inspecting the saw blade the cutters do not shine, then all actions have been done effectively and the hacksaw is ready for use.

Tooth setting

The teeth separation is necessary to prevent the hand saw from jamming while cutting, so it would run smoothly and easily. After prolonged use of the hacksaw, it may be necessary to perform a setback before sharpening it. The idea of the process is to bend the teeth evenly in all directions. After this procedure there should be some free gaps on both sides of the blade. The movement of the cutting tool in the cut will be much more efficient.

The more bent the cutters, the lower the risk of jamming the saw during operation. But do not overdo it, otherwise the sawing will be very problematic.

Please note! According to the standard, the adjustment should be no more than 2 mm. If the hacksaw is intended for sawing dry wood, the teeth are to be bent by 0.3-0.5 mm. For sawing raw wood materials you should allow 0,5-1 mm distance between the saw blade and the workpiece.

For convenient performance of bending it is recommended to use setters. special devices. The hacksaw is well clamped in a vise, the device is mounted on the work surface. The main thing is that the teeth must not protrude fully, otherwise they will break.

Sharpening 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 lead to “tempering”. Of course, processing is much faster with diamond tools, but the cost is very high. It is much more economical to buy a carbide blade.

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

Toothblade sharpening at home

To process a circular saw it is not necessary to have a special machine for sharpening circular saws with your own hands. To fix the blade in a certain position, you can use a flat stand that has several nuances:

• The surface must be in line with the center of the sharpening disc.
• The sharpening plane should be at an angle of 90 degrees with respect to the toothed wheel.
• In order to create different inclinations, the fixture must have a swivel joint.

To select the right angle, the marker is made with a colored marker. The device must be set in a high-powered vise. Not even the slightest movement of the special stand is allowed.

Methods of grinding circular saws

Any kind of sharpening machine can be used for sharpening a new cutting edge. It is important to choose the correct emery wheel and sharpen the edge with it. Corundum or diamond models must be used for this.

The optimal solution is to use special equipment designed for this task. But because of its high cost, it is not practical in many cases. An alternative method is to use a sharpening machine with the ability to change the angle of the corundum disc.

Under no circumstances should you do the sharpening by hand yourself. Firstly, it will take a very long time. Secondly. the result will not meet the standards. In case there is no possibility to perform sharpening of wood saw blade by yourself it is recommended to use the services of specialized companies.

Professional sharpening of circular saws with their own hands is performed according to the following rules:

• the main deformation occurs on the top edge of the tooth. There is a rounding of the edges from 0.1 to 0.3 mm. This is where you need to start machining;
• sharpening is performed on the front and back edge. This will provide an opportunity to repeat the procedure up to 25 times;
• the value of the removal should not exceed the value of 0,05-0,15 mm;
• the level of processing of the front and back edges should be the same.

After sharpening the wood discs, it is recommended that they be sharpened with fine grit sandpaper. It can be done manually or with a special machine.

Specialists advise using special corundum discs, the end surface of which has a specially shaped groove. It will make the procedure easier.

Ways to extend the life of a circular saw blade

The process of shaping a new cutting edge is laborious and time-consuming. Therefore a number of conditions are recommended to increase the life of the blade.

First of all, you should read the manufacturer’s recommendations. They give the number of revolutions (maximum and minimum) for the different types of material to be machined. For metal it should be less than for wood.

Hard tips have a longer service life. However, they are more likely to chip and break off. The alternative soft one is practically not subject to such defects. But its lifetime is shorter than that of hard.

Roughness on the cutting surface is not allowed. These can cause chipping and cracking later on.

The video shows an example of a machine for sharpening disks, made with their own hands:

Professional equipment from 150 000. up to 1.5 million

Professional sharpening machines are intended for use in the repair shops of large sawmills or by service companies specializing in these tools. They all have industrial controllers with the ability to select the processing program for a specific saw blade model.

№	Model	Max. diameter (mm)	Drive power (W)	Weight (kg)	Control type	Price (.)
1	MF1263	630	300	260	automat	165 000
2	Unimac 600A 288,000	630	300	250	automatic	288 000
3	GRIGGIO GA U5	400	560	115	machine	451 000
4	OS-2M	1500	1 100	270	p/automatic machine	525 000
5	OTOMAT-96	750	1 000	850	automatic machine	1 500 000

Tools required

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

The following tools can be used to do the job of sharpening the disk with your own hands:

It is also possible to use a circular saw blade sharpening machine that does not require the above tools.

When to do the work of restoring circular saws?

A rather important issue can be called determining when circular saws should be sharpened. Severe wear and tear can make it impossible to sharpen a disc. There are three clear signals that can be identified that determine the need for circular saw blade sharpening:

• Appearance of smoke, heating of the safety guard. The sharpening attachment usually has a special guard that can become hot if the circular saw blade becomes blunt. It should also be noted that in special cases smoke may be produced as a result of excessive heating of the cutting zone.
• Also with mechanical feeding, when the pressure is adjusted with your own hands, you should give a lot of force to get the desired result.
• When wood or other material is being cut, there are traces of carbon residue and a corresponding smell in the cutting area.

In the above situations it is recommended to sharpen the circular saw blade.