How to sharpen a circular saw at home
Circular saws in wood: How to sharpen them yourself?
Those who work with wood know how important circular saws are. Always keep your circular saw in good working order and in perfect working order. All sharp-cutting tools are known to have a tendency to blunt. Wood circular saws are no exception. Sharpening them requires special attention. At the first signs that the saw is starting to malfunction, you should start sharpening, because later the tool will start to blunt even more.
Circular saw sharpening is made in different ways: with a file, on a machine, in a vice and by weight.
Wood circular saws, sharpening of which is periodically necessary, are especially important in the arrangement of a country house made of wood. Circular saws are also called circular saws. This tool is important because it can accurately cut wood.
Is it possible to sharpen it yourself?? Yes, sharpening by yourself is possible. Timely sharpening of circular saws on wood will not only allow you to have a sharp working tool at hand, but also increase its service life. You should especially keep an eye on the condition of circular saws, whose power is relatively low, as a poorly sharpened saw begins to overheat. And overheating can lead to complete failure of the working tool.
How to sharpen circular saw blades
Any kind of sharpening machine can be used to form a new cutting edge. It is important to choose the correct emery wheel from the beginning and sharpen the edge with it. Use corundum or diamond models.
HOW TO SHARPEN CIRCULAR SAW BLADES, SIMPLE JIG.
The best option is to use special equipment designed for this work. But because of its high cost, in many cases it is impractical to buy it. 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. First of all, it takes a very long time. Secondly. the result obtained 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 upper edge of the tooth. There is a rounding of edges from 0.1 to 0.3 mm. It is from this place it is necessary to start processing;
- the sharpening is performed along the front and the rear edge. This will ensure that the procedure can be repeated up to 25 times;
- the value of removal should not exceed the value of 0,05-0,15 mm;
- The sharpening level on the leading and trailing edges must be identical.
After the wood disc sharpening is finished, it is recommended to finish it with a fine-grained emery paper. This can be done manually or with a special machine.
Specialists advise to use special corundum discs, the end surface of which has a specially shaped groove. It will facilitate the performance of the procedure.
How to sharpen a circular saw with your own hands
You can sharpen your saw at home all by yourself. For this, there is no need to go to a workshop to use a specialized sharpening machine or buy one. It is rather expensive, and is rarely used for sharpening, unless of course you plan to use it for large production purposes.
But it is not the best solution to hold circular saw blades in hands while sharpening teeth with a grinding wheel. A circular saw blade is not a drill, it is much bulkier. No amount of hand hardness and excellent judgement will make it possible to sharpen the cutting elements so that they are sharp enough to be used effectively. For this, the simplest type of fixing device should be provided.
To hold the toothed circular wheel in position relative to the plane of the sharpening tool, you can use the most ordinary flat stand.
Its surface position should correspond to the level of the axes on the rear disc. Placement of gear wheel on the stand so that the sharpened tooth plane is perpendicular to the blade of the saw blade. To sharpen beveled teeth on front and rear surfaces, it is necessary to have movable joints in this device.
But in such cases it is quite difficult to maintain the same values of the front and back angle of the tool. To solve this problem, it is necessary to make a rigid fixation of the saw’s center according to the desired position in relation to the sharpening wheel. It is made by means of slots for mandrel, which is mounted on the stand with placing of sharpened saw blades on it, or by means of setting special stop on the stand that fixes saw blade according to required angle to the abrasive stone.
If you adhere to all the requirements for sharpening a carbide circular saw, then this tool will work as effectively as possible for a long period of time.
The need for sharpening
The most obvious benefit of sharpening is speed of sawing. This is even more important in the country house than in the workshop, because you often have to work in tight spaces and awkward positions. A badly sharpened blade gets stuck in wood, especially damp wood. Besides, there is a risk that the blade will break and hurt the person working.
The practical advantages of sharpening include:
Sharpening a carbide-tipped circular saw blade
Carbide tipped disc Decide for starters if you want to sharpen or not. There are several obvious signs that indicate the relevance of performing this procedure. If ignored, the disc may become unrepairable in the future and cause failure of an expensive machine.
The advantage of using a tipped saw blade is that it extends the life of the blade. It is also designed for working hardwood. Claddings are made of steel 9KhF, 50KhVA, 65G and similar compositions. They are very hard, but there is an increased likelihood of breakage if used extensively.
Timely sharpening of circular saws with the machine with their own hands is performed at the following obvious signs:
- higher load on the motor. The reason for this is the deterioration of sharpening and as a consequence. the power unit needs more power to cut wood. If protective relays are not provided in the motor design, it is possible that the motor fails;
- deterioration of sawing quality. The first sign is an increase in the width of the cut, as well as chipping and jagged edges;
- increase in time of processing the workpiece. It takes longer than usual to form the cut.
The best way is to periodically check the condition of a wood tipped blade. This would require temporarily leaving the machine and removing the cutting tools. If its geometrical parameters are not the same as the initial ones. sharpening is necessary.
Sharpening angles of carbide-tipped circular saws are not easy to maintain because the tooth is tapered. This alloy is hardened by soldering. The geometry of the cutting part is complex, and the sharpening parameters must be maintained accurately.
Work is carried out by smoothing out the cutting edge to a radius of 0.3 mm. A greater tolerance should not be tolerated.
- Grinding is carried out on the front and back surfaces of the tooth. If performed correctly, the total number of sharpenings before the blade wears out is 30 times.
- Work should begin on the front surface.
- The portion of the tooth that is clamped must fit snugly on the cutting wheel.
- Turning time is 3 to 5 seconds. No longer possible. This causes unnecessary heating of the metal. It is rehardened and tempered with a decrease in hardness.
- Thickness of material to be ground is in the region of 0,15 m.
Grinding circular saws
In domestic saws as a material for cutting inserts the sintered tungsten-cobalt alloys of BK marks (BK6, BK15 etc.) are used. the number indicates the percentage of cobalt). BK6 has a hardness of 88.5 HRA, BK15. 86 HRA. Foreign manufacturers use their own alloys. BK hard alloys consist mainly of tungsten carbide cemented with cobalt. The characteristics of the alloy depend 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 alloy.
Carbide inserts are attached to the disc by high-temperature brazing. As a soldering material, in the best case, silver solder (PSr-40, PSr-45) is used, in the worst case. Copper-zinc solder (L-63, MNMC-68-4-2).
Carbide tooth geometry
The following types of teeth are distinguished by their shape.
Straight tooth. Usually used in saws for longitudinal quick sawing, where quality is not very important.
Oblique (beveled) tooth with left and right angles of slope of the posterior plane. Teeth with different angles of inclination alternate with each other, which is why they are called alternate beveled. This is the most common tooth shape. Depending on the size of the resharpening angle, cross-toothed saws are used in cutting a wide variety of materials (wood, chipboard, plastics). both longitudinally and transversally. Saws with a steep back angle are used as scoring machines for double sided laminated boards. Their use prevents chipping of the coating on the edges of the kerf. Increasing the bevel angle reduces the cutting effort and reduces the danger of chips, but also reduces the durability and strength of the tooth.
Teeth can be inclined not only on the posterior but also on the anterior plane.
Trapezoid tooth. A feature of these teeth is the relatively slow blunting rate of the cutting edges compared to alternate teeth. They are usually used in combination with the straight tooth.
Alternating with the latter and rising slightly above it, the trapezoidal tooth performs roughing while the straight tooth following it. finishing. Saws with alternating straight and trapezoidal teeth are used for cutting double-sided laminated panels (chipboard, hardboard, wood-fibre board, etc.), for example.), as well as for sawing plastics.
Conical tooth. Saws with conical teeth are auxiliary and are used to cut the lower layer of the laminate, protecting it from splintering as the main saw passes through.
The vast majority of tooth flanks are flat, but there are also saws with a concave flank. They are used for finish crosscutting.
Tooth sharpening angles
Sharpening angles are determined by the intended use of the saw. т.е. The type of material and direction in which the blade is intended to cut. Saws for longitudinal sawing have a relatively large rake angle (15°-25°). Cross-cutting saws have the angle of γ normally varies between 5° and 10°. Universal saws intended for cross and rip sawing have a median rake angle. normally 15°.
Angle values of sharpening 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 such an angle are used for cutting of non-ferrous metals and plastics.
The basic principles of sharpening
When cutting massive workpieces the sides are subject to quick wear.
Avoid excessive dulling of the saw blade. Radius of curvature of cutting edge should not exceed 0.1 to 0.2 mm. Besides the fact that when working with a very blunt saw, productivity falls sharply, it takes several times longer to sharpen it than to sharpen a saw with a normal bluntness. The degree of blunting can be determined both by the teeth themselves and by the type of kerf they leave.
Proper sharpening of circular saws consists in simultaneous ensuring the proper sharpness of the cutting edge, ensuring the maximum number of sharpenings, which in the best case can be up to 25-30 times. It is therefore recommended that the carbide tooth is ground on its front and rear surfaces. In fact, the teeth can also be sharpened along one front plane, but the number of possible sharpenings is almost twice as low as in the case of two planes. The figure below illustrates why this happens.
It is recommended to make the last pass when sharpening circular saw blades on the back plane of the tooth. Standard metal removal rates. 0.05-0.15 mm.
Before sharpening, the saw must be cleaned of debris, such as tar, and the sharpening angles checked. On some saws, they are written on the blade.
Equipment and materials for sharpening circular saw blades
When using grinding wheels (especially diamond wheels), it is desirable to cool them with coolant.
The micro-hardness of abrasives decreases with increasing temperature. Increasing the temperature to 1000° C lowers the micro-hardness by a factor of nearly 2 to 2.5 compared to the micro-hardness at room temperature. Increasing the temperature to 1300° C causes the hardness of abrasives to decrease by up to 4-6 times.
The use of water for cooling may cause the occurrence of rust on the parts and machine units. 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, but for finish grinding. low concentrated emulsions.
However, when sharpening saw blades at home with low sharpening intensity, it is not often necessary to cool the wheel. Not wanting to waste time on this.
In order to increase the grinding performance of the grinding wheels and to reduce the specific wear, the largest grit size should be selected, which ensures the required surface finish of the ground tooth.
For selection of the grit size, according to the grinding stage, you may use the table in the article on sharpening stones. For example, when using diamond wheels, grinding wheels with a 160/125 or 125/100 grit size can be used for roughing, and for finishing. 63/50 or 50/40. Wheels with a grit size of 40/28 to 14/10 are used for deburring.
Use a wheel circumferential speed of approx. 10-18 m/s when sharpening carbide-tipped teeth. This means that when using a 125mm diameter wheel, the motor speed should be around 1500-2700 rpm. Brittle alloys are sharpened at a lower speed out of 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, with increased wheel wear.
When using circular saw blade sharpening machines, the relative position of the saw blade and the sharpening wheel can be changed in various ways. Movement of one saw (motor with wheel is stationary), simultaneous movement of saw and motor, movement of only motor with wheel (saw blade is stationary).
A large number of sharpening machines with various functions are available. The most complex and expensive programmable complexes are able to provide a fully automatic sharpening mode, in which all operations are carried out 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 sharpening angle, all further operations. Turning of saw blade around its axis (turning on tooth), feed for grinding (bringing into contact with wheel) and control of thickness of metal removed from tooth. are made by the worker manually. Such simple models are appropriate for home use, when circular saws are sharpened occasionally.
An example of the simplest circular saw sharpener is the system shown in the picture below. It consists of two main units. Motor with grinding wheel (1) and slide (2) on which the saw to be sharpened is set. The swivel mechanism (3) is used to change the blade angle (when sharpening teeth with a beveled front surface). The screw (4) moves the saw along the axis of the grinding wheel. This makes it possible to set the desired rake angle. Screw (5) is used to set a stop to prevent the tooth from sinking too far into the interdental space.
Sharpening process for circular saw blades
The saw is placed on the arbor, clamped by the tapered (centering) sleeve and nut and then set in horizontal position by the mechanism (3). This ensures that the bevel angle of the front plane (ε1) equal to 0°. If you have a disc grinder that does not have an angle scale built into the tilt mechanism, use a standard pendulum-type angle gauge to do so. Check the level of the machine in such a case.
By rotating the screw (4) of the mechanism providing horizontal movement of the mandrel with a wheel, the necessary forward angle of sharpening is set. In other words, the saw is moved to a position in which the front plane of the tooth fits tightly against the working surface of the wheel.
A marker is used to mark the tooth at which the sharpening begins.
The motor is turned on and the front surface is sharpened. The saw blade is pushed into contact with the disc and back and forth a few sawing movements while pressing the tooth against the disc. The thickness of the removed metal is regulated by the number of sharpening strokes and by the force with which the tooth is pressed against the abrasive disk. After sharpening one tooth the saw blade is taken out of contact with the wheel, turned one tooth and the sharpening operation is repeated. And so until the marker mark makes a complete circle, indicating that all the teeth are sharpened.
Grinding a tooth beveled on the front surface. The difference between bevel sharpening and straight sharpening is that the saw must not be set horizontally, but tilted. with an angle corresponding to the bevel angle of the front plane.
The angle of inclination of the saw is set with the same pendulum angle gauge. First set the positive angle (in this case 8°).
Then every second tooth is sharpened.
After sharpening half of the teeth the angle of the saw blade changes from 8° to.8°.
Again every other tooth is sharpened.
Grinding on the back plane. To sharpen the tooth on the back plane it is necessary that the machine for sharpening saw blades allows to set up the saw in such a way that the back plane of the tooth will be in the same plane with the working surface of the abrasive disk.
If you do not have a machine for sharpening saw blades
Accurately maintain the necessary angles of sharpening by holding the saw in your hands by weight. a task impossible even for a person with unique eyesight and enviable hardness of hands. The most sensible thing to do in this case. make a simple device for sharpening, which makes it possible to fix the saw in a certain position in relation to the wheel.
The simplest of such devices for sharpening circular saws is a stand, the surface of which is flush with the axis of the sharpening wheel. Putting the saw blade on it, you can ensure perpendicularity of the front and back planes of the tooth in relation to the saw blade. And if the upper surface of the stand is made movable. by mounting one side hinged and the other side hinged. supported by a pair of bolts that can be screwed in and out. then it can be mounted at any inclination, making it possible to sharpen an oblique tooth on the front and back planes.
But in this case one of the main problems remains unresolved. Exposing the same front and back sharpening angles. This problem can be solved by fixing the center of the saw relative to the abrasive disk in the desired position. One way to do this. making 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 forward angle of the tooth sharpening. But for sharpening circular saws with different diameters or angles of sharpening, it should be possible either to move the motor or the stand and with it the groove. The other way to provide the required sharpening angle is more simple, and consists in the installation on the table of stops fixing the disk in the right position. At the end of the article there is a video demonstration of such a device.
Device for circular saws sharpening with movable stops on the table
Quality control of sharpening
GOST 9769-79 establishes certain values of tolerances on sharpening parameters. run-out of tooth tips should not exceed 0,2 mm (for saws up to 400 mm in diameter), radial one. 0,15 mm. Runout can be checked with a simple dial gauge.
How to sharpen the circular saw blade manually?
You notice that your circular saw is not cutting as well as it should? Materials are becoming harder to cut, black soot, smoke and a hint of burning? Obvious signs that the disc needs sharpening! Otherwise not only the productivity of the tool will decrease, but also the danger of overheating of the motor will arise. Let us tell you how you can return the cutting properties of your sawblade with your own hands.
Principle and angle of grinding circular saw blades
The circular saw blade is sharpened at 4 key sharpening angles. These are the basic technical parameters of the cutting disc, as well as the shape type of the cutting teeth.
It is worth noting that all the teeth of a circular saw are characterized by front (γ), rear (α) angles, as well as the cutting angle of the front and rear surfaces (ε1 and ε2). The value of each specified angle should correspond to the purpose of the sawing equipment, the materials to be sawn and the direction of sawing.
In particular, the longitudinal saw is sharpened at fairly large forward angles (15° to 25°).
Forward angles for cross-cutting cuts are in the 5° to 10° range. Universal variants, used for processing materials in all types of directions, standardly sharpened at 15°.
The angle is also influenced by the hardness of the objects to be cut. Their value has a strict dependence: if the material to be sawed is harder, the cutting teeth should be less sharpened.
According to the basic principle of resharpening the teeth on carbide saw blades, it is important to remember that in continuous use the biggest wear occurs on the top cutting edges. As a result, if they are used intensively, their mowing lines can round off to 0.3 mm or more. Regarding the tine planes, it is worth noting that the greatest wear occurs on the front surfaces.
When properly sharpening the cutting element, the cutting edges must be shaped so that the cutting edge radius does not exceed 0,2 mm. In this connection it is recommended to carry out parallel grinding of the metal on the front and rear surfaces of the teeth. This is considered the most appropriate way of sharpening. It is possible to sharpen just one front surface, but in such cases this operation is more time-consuming. In addition, there will be more rapid grinding of the teeth, because there is a need to grind more metal from the front surfaces.
The standard layer for grinding metal is a value of 0.05-0.15 mm.