Sharpening circular saws for wood with your own hands: geometry of corners, machine tools
Sharpening of carbide-tipped circular saws is carried out with obvious signs: increased engine load, deterioration of sawing, increased processing time.
Ways to Extend Saw Blade Life
The process of forming a new cutting edge is laborious and time consuming. Therefore, it is recommended that you fulfill a number of conditions to increase the life of the disk.
First of all, you should read the manufacturer’s recommendations. They indicate the number of revolutions (maximum and minimum) for different types of processed materials. For metal, this parameter should be less than for wood.
Hard solders have a long service life. However, they are more likely to chip and break off. The alternative soft is practically not subject to such defects. But its service time is shorter than that of a solid one.
The appearance of roughness on the cutting surface is not allowed. In the future, they can lead to the appearance of chips and cracks.
The material shows an example of a hand-made disc sharpening machine:
Sharpening circular saws for wood with your own hands: geometry of corners, machine tools
Carbide-tipped circular saw blades may lose their original qualities during prolonged use. But this does not mean that you should purchase a new cutting tool. In most cases, sharpening can be done at home using any suitable machine.
Ways to sharpen circular saws
Any sharpening machine can be used to form a new cutting edge. It is important to initially choose the right emery wheel and sharpen the edge with it. For this it is necessary to use corundum or diamond models.
The best option is to use special equipment designed to do this job. But due to its high cost, in many cases, its acquisition is impractical. An alternative way is to use a grinding machine with the ability to change the angle of the corundum disc.
In no case should you do the sharpening by hand yourself. First, it will take a very long time. Secondly, the result obtained will not meet the standards. If it is not possible to sharpen the saw blade on wood yourself, it is recommended to use the services of specialized companies.
Do-it-yourself professional sharpening of circular saws is performed according to the following rules:
- The main deformation occurs at the upper edge of the tooth. The edges are rounded from 0.1 to 0.3 mm. It is from this place that you need to start processing;
- Sharpening is carried out along the leading and trailing edges. This will provide the ability to repeat the procedure up to 25 times;
- Removal rate should not exceed 0.05-0.15 mm;
- The level of machining of the leading and trailing edges must be the same.
After the sharpening of the discs on wood is completed, it is recommended to finish it with fine-grained sandpaper. This can be done manually or using a special machine.
An experienced craftsman usually knows right away when the prongs start to fail. This can be determined by the following criteria:
- Visual deformation of the teeth (individual teeth may bend or break off);
- During sawing, the master has to make great physical efforts in order for it to work efficiently;
- Some seasoned sawers check the sharpness of the teeth by touch. However, this method is not recommended, as any careless touching of the teeth may result in a finger injury;
- Often makes an unpleasant creak or crackle during operation. During the sawing process, you can clearly hear the wood creak.
If the teeth are dull, it is advisable to sharpen the saw as quickly as possible. Many DIYers mistakenly believe that getting injured from a sharp saw can be much faster than from a blunt one. In fact, the situation is exactly the opposite. This paradox can be easily explained: when a sawer uses a blunt saw, he has to apply physical force. If the force is incorrectly calculated or applied in the wrong direction, it is very easy to injure the hand. And if the sawer uses a well-sharpened tool, no effort is required, the main thing is precise and accurate movements.
Definition and purpose of the circular saw
A circular or circular saw is a tool whose working surface is a disc. This disc can be of various thicknesses and different diameters, depending on the purpose. At the edges, the disc is equipped with sharp teeth, which can have various shapes, for example:
- Straight vertical teeth;
- Beveled teeth;
- Trapezoidal teeth;
- Cone-like teeth.
It is used when a large volume of wood needs to be cut. She is comfortable working with both hard and soft woods. And also with the help of it you can process plywood and chipboard. When the disc is given rotation, the teeth cut into the material and begin to saw it. Experienced sawers claim, that working with a circular saw is much easier than with a classic one, which is a horizontal metal plate with teeth and one (two) plastic handles.
A circular saw is often used:
- On sawmills;
- On the construction of wooden houses;
- During renovation work in city apartments;
The working surface of such a tool is usually hard-alloyed. These solders are used to prevent the teeth from warping when sawing hardwood. However, sooner or later, the teeth of any circular saw become dull. If this moment has come, then it is time to sharpen the tool.
Sharpening carbide-tipped circular saws
Sharpening saw blades for wood is one of the most important maintenance measures for a circular or circular saw. If not sharpened, it will quickly become dull and unusable.
It is most convenient to sharpen on a special production machine. However, many home craftsmen make their own design for this purpose, which significantly saves time and money.
- Definition and purpose of the circular saw
- Sharpening discs
- Using a special machine
- Self sharpening
Saws made of high-quality materials are less blunt, which means they rarely need sharpening. However, if the discs are made of low-quality material (and this happens quite often, and even an experienced craftsman cannot always determine the quality of the metal "by eye"), most likely they will have to be sharpened often. Therefore, any home master, the user of a circular saw should know how to sharpen it.
Sharpening angles of teeth
The sharpening angles are determined by the purpose of the saw. Those. The cutting of which material and in which direction it is intended. Rip saws have a relatively large rake angle (15 ° -25 °). For cross-cut saws, the γ angle usually ranges from 5-10 °. Versatile cross and rip saws have an average rake angle. Usually 15 °.
The sharpening angles are determined not only by the direction of the cut, but also by the hardness of the material being cut. The higher the hardness, the smaller the anterior and posterior 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.
If you don’t have a saw blade sharpener
Accurately maintain the required sharpening angles while holding the saw in your hands. An unbearable task even for a person with a unique eye and enviable firmness of hands. The most reasonable thing in this case. Make the simplest sharpening device that makes it possible to fix the saw in a certain position in relation to the circle.
The simplest of such devices for sharpening circular saws is a stand, the surface of which is flush with the axis of the grinding wheel. By placing the saw blade on it, you can ensure that the front and back planes of the tooth are perpendicular to the saw blade. And if the upper surface of the stand is movable. Hinged one side and the other. Supported by a pair of bolts that can turn in and out. Then it can be installed at any inclination, getting the opportunity to sharpen an oblique tooth along the front and back planes.
True, in this case, one of the main problems remains unresolved. Keeping the same front and rear sharpening angles. You can solve this problem by fixing the center of the saw relative to the abrasive wheel in the desired position. One way to implement this. Make a groove on the surface of the stand for the mandrel on which the saw is installed. Moving the mandrel with a circle along the groove, it will be possible to maintain the required rake angle of the tooth sharpening. But for sharpening circular saws with different diameters or sharpening angles, it must be possible to either move the engine or the stand and the groove with it. Another way to provide the required sharpening angle is simpler, and is to install the stops on the table to fix the disc in the desired position. At the end of the article there is a demonstration of such a device.
Equipment and materials for sharpening saw blades
When using abrasive wheels (especially diamond), it is desirable to cool them with coolant.
As the temperature rises, the microhardness of abrasive materials decreases. An increase in temperature to 1000 ° C reduces the microhardness by almost 2-2.5 times compared to the microhardness at room temperature. An increase in temperature to 1300 ° C causes a decrease in the hardness of abrasive materials by almost 4-6 times.
The use of water for cooling can lead to rust on the parts and assemblies of the machine. To eliminate corrosion, soap and certain electrolytes (sodium carbonate, soda ash, trisodium phosphate, sodium nitrite, sodium silicate, etc.) are added to the water, which form protective films. For normal sanding, soap and soda solutions are most often used, and for fine sanding. Low-concentration emulsions.
However, when sharpening saw blades at home with low intensity of grinding work, they do not resort to cooling the wheel so often. Not wanting to waste time on it.
To increase the productivity of grinding with abrasive wheels and reduce specific wear, you should choose the largest grain size, which provides the required surface cleanliness of the sharpened tooth.
To select the grit size of the abrasive, in accordance with the sharpening stage, you can use the table in the article about sharpening bars. For example, in the case of using diamond wheels, wheels with a grain size of 160/125 or 125/100 for finishing can be used for rough sharpening. 63/50 or 50/40. Wheels with a grain size of 40/28 to 14/10 are used to remove chipping.
The peripheral speed of the wheel when sharpening carbide teeth should be about 10-18 m / s. This means that when using a 125 mm diameter wheel, the engine speed should be around 1500-2700 rpm. Sharpening of more brittle alloys is performed at a lower speed from this range. When sharpening carbide tools, the use of hard modes leads to the formation of increased stresses and cracks, and sometimes to chipping of the cutting edges, while the wear of the wheel increases.
When using machines for sharpening circular saws, changing the relative position of the saw and the grinding wheel can be realized in different ways. Moving one saw (the motor with the wheel is stationary), the simultaneous movement of the saw and the motor, only moving the motor with the wheel (the saw blade is stationary).
A large number of sharpening machines of various functionality are produced. The most complex and expensive programmable complexes are capable of providing a fully automatic sharpening mode, in which all operations are performed without the participation of a worker.
In the simplest and cheapest models, after installing and fixing the saw in a position that provides the required sharpening angle, all further operations. Turning the saw around its axis (turning per tooth), feeding for grinding (bringing it into contact with the wheel) and controlling the thickness of the metal removed from the tooth. Produced by the worker manually. It is advisable to use such simple models at home, when the sharpening of circular saws is episodic.
An example of the simplest machine for sharpening circular saws is the system, the photo of which is shown in the photo below. It consists of two main units. Motor with circle (1) and support (2) on which the sharpened saw is mounted. The turning mechanism (3) is used to change the angle of inclination of the blade (when sharpening teeth with a beveled front plane). The screw (4) moves the saw along the axis of the abrasive wheel. This ensures that the required rake angle is set. The screw (5) is used to set in the desired position the limiter, which prevents the wheel from excessively entering the interdental cavity.
General rules for sharpening a circular saw
- First of all, the main faces are processed, of which the front wears out more.
- In extreme cases, with severe wear of the side faces, they are corrected.
- At a time, remove no more than 0.15 millimeters of the saw metal thickness.
- When finishing the edges with an electric tool, overheating of the metal is not allowed, in which case its properties deteriorate.
- To ensure the maximum service life of the saw, when it can be sharpened up to 30 times, both edges should be sharpened, both the front and rear, by removing the same amount of metal.
- It is not allowed to sharpen circular saws with tools not intended for this, for example, an angle grinder and a disc for cutting metal.
After carrying out the basic sharpening operations, you can finalize the teeth with fine sandpaper. The quality control of the sharpening of the tool takes place in working conditions. If everything is in order, the material will be cut clean, smooth, without visible defects and blackening.
It is possible to independently sharpen the teeth by hand using a file, so that it is of high quality, if they do not have a bevel, that is, the surface of the front edge is perpendicular to the surface of the blade. The process looks like this:
- A block is harvested from dense wood with a cross section of somewhere 50×50 mm and a length of 100 mm. The sides of the bar should be strictly perpendicular to each other.
- Mark with a marker any tooth that will be reportable and the first to be processed.
- The saw blade is clamped in a vice together with a bar so that the front edge of the workpiece is flush and in the same plane with the surface of the bar (the bar in this case acts as a file guide).
- A thin file (its thickness should allow it to fit freely into the cavity between adjacent teeth) is applied to the treated surface of the tooth and simultaneously sharpening is carried out to the bar and methodically back and forth.
- So each tooth is gradually sharpened, monitoring the condition of the bar and, when working out its surface, slightly shifting the plane.
The main sharpening angles of circular saws
The front face, the one that first cuts into the workpiece in the direction of the saw movement, forms the main cutting edge with the rear face. The angle at which the leading edge meets the material is called the Y-angle (angle of attack). The angle between the back face and the front face is the taper angle. If you subtract the rake angle and the taper angle from 90 degrees, you get the clearance angle.
In practice, it is important to observe these angles when sharpening for each type of disc. It is according to the front angle that the saws are divided into types:
- Longitudinally cutting, where the rake angle should not go beyond 15-25 degrees.
- Transverse cutting, where it is permissible to sharpen the front face of the tooth at an angle of 5-10 degrees.
- Universal discs, which are easy enough to cope with both longitudinal and transverse cuts, their rake angle should be maintained in the region of 15 degrees.
The angle of the bevel of the rear and front planes is also important: the sharper it is, the easier it is for the saw to enter the material, but wear occurs faster.