How to sharpen a circular saw at home
Harbor Freight Circular saw blade sharpener review ( Chicago Electric)
Saw sharpening required
Carbide tipped disc Decide for starters whether to sharpen or not. There are several clear signs that indicate the relevance of performing this procedure. If they are ignored, then later the disk may become unrepairable and cause failure of an expensive machine.
The advantage of using a tipped circular saw blade is a longer service life. Also suitable for hardwoods. Claddings are made of steel 9KhF, 50KhVA, 65G and similar compounds. They have a high hardness, but with significant operation will increase the likelihood of breakage.
Timely sharpening of circular saws with a machine with their own hands is performed at the following obvious signs:
- higher load on the motor. The reason for this is a deterioration in sharpening and as a consequence the power unit needs more power to cut through the wood. If the motor is not equipped with protective relays, it is possible that the motor fails;
- Deterioration of quality of cut. The first sign is an increase in the width of the cut, as well as the formation of chips and irregularities on its edges;
- Longer cutting time of the workpiece. Cutting takes longer than normal to form.
The best way is to periodically check the condition of the wood tipped blade. It requires temporarily leaving the machine and removing the cutting tool. If its geometry does not match the original, it must be resharpened.
Sharpening of carbide-tipped circular saws
Sharpening wood saw blades is one of the most important steps in caring for a circular, or circular saw. If it is not sharpened, it will quickly become blunt and unusable.
Sharpening is best performed on a special production machine. However, many craftsmen at home make their own construction for this purpose, which saves time and money.
Saws made of good quality materials blunt less frequently, so they do not need to be sharpened as often. However, if the discs are made of poor quality material (which is quite often the case, and even an experienced craftsman is not always able to “by eye” determine the quality of the metal), it is likely that they will have to be sharpened frequently. Every home handyman who uses a circular saw should therefore know how to sharpen it.
The first version of the manufacture of the simplest sharpening equipment has the following form:
- On the workbench is placed an emery machine, on the shaft of which is placed a wheel with a diamond coating
- Fixed base plate made of particleboard. This base also acts as the guide along which the sliding frame will move
- In the next step, a movable frame is made of particle board or plywood, the walls of which should point downwards and act as a movement mechanism
- On the outer side of the movable frame is placed a disk retainer of the appropriate diameter, and a slot is made
- The result is a complete sharpening machine for circular saw blades
For the manufacture of such a device requires a minimum of time and cost, and the efficiency of its use is 100%. For details please refer to
Check the quality of the sharpening
On the ground teeth should be no cracks, chips, visible risks from the grinding wheel. The radius of curvature of the cutting edge must not exceed 0.015 mm. This can be defined visually as a lack of ghosting on the cutting edge.
How to sharpen your circular saw blades, the easy way.
GOST 9769-79 specifies certain tolerance values of grinding parameters. End run-out of tooth tips should not exceed 0,2 mm (for saw diameter up to 400 mm), radial run-out should not exceed 0,15 mm. Runout is checked with usual pointer indicator.
The deviation of the sharpening angles must not exceed:
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Grinding of circular saws
In domestic saws as a material for cutting plates the sintered tungsten-cobalt alloys of BK marks (BK6, BK15 etc.) are used. the number indicates the percentage of cobalt). Hardness of BK6 is 88.5 HRA, BK15 has a higher hardness. 86 HRA. Foreign manufacturers use their alloys. Hard VC 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 grain, the higher the hardness and strength of the alloy.
Carbide inserts are fixed on disc by high-temperature soldering. As soldering material, in the best case, silver solder (PSr-40, PSr-45) is used, in the worst case. copper-zinc solders (L-63, MNMC-68-4-2).
Carbide tooth geometry
The following types of teeth are distinguished by their shape.
Straight tooth. Typically used in saws for longitudinal quick cuts where quality is not a major concern.
Oblique (beveled) tooth with left and right angles of inclination of the rear plane. Teeth with different bevel angles alternate with each other, therefore, are referred to as alternate bevels. It is the most common tooth design. Depending on the angle of sharpening, alternately beveled toothing saws are used for cutting all kinds of materials (wood, chipboard, plastics). both in the longitudinal and transverse direction. Saw blades with a large angle of the back plane are used as undercutting when cutting double-sided laminated boards. Their use avoids chipping of the coating on the edges of the kerf. Increasing the bevel angle lowers cutting forces and reduces the risk of chip breakage, but also reduces tooth strength and durability.
The teeth can be inclined not only on the back plane but also on the front plane.
Trapezoid tooth. The teeth have a relatively slow blunting rate compared to alternately beveled 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. finishing. Saws with alternating straight and trapezoidal teeth are used for cutting double-sided laminated panels (chipboard, hardboard, hardboard and so on).) as well as for sawing plastics.
Conical tooth. Tapered-tooth saws are auxiliary saws and are used for cutting the lower layer of the laminate, protecting it from splintering when the main saw passes over.
The vast majority of tooth flanks are flat, but other saws also have a concave tooth flank. They are used for finish crosscutting.
Tooth sharpening angles
Cutting angle values are determined by the intended use of the saw. т.е. The angle depends on the material to be cut and the direction in which it is to be cut. Saws for longitudinal sawing have a relatively large rake angle (15°-25°). In cross-cutting saws the angle γ Usually ranges from 5° to 10°. Universal saws designed for crosscut and longitudinal sawing have an average value of the front angle. usually 15°.
Angle values are not only dictated by cutting direction, but also by the hardness of the material to be 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 cutting massive workpieces, the sides are also subject to rapid wear.
Saw bluntness must not be excessive. The radius of curvature of the cutting edge should not exceed 0,1-0,2 mm. In addition to the dramatic drop in productivity that a severely blunted saw has, it takes several times longer to sharpen it than a normally blunted saw. The degree of blunting can be seen both in the teeth themselves and in the type of kerf they leave behind.
The correct sharpening of circular saw blades is to ensure simultaneously with the proper sharpness of the cutting edge the maximum number of sharpening cycles which in the optimal case can be up to 25-30 times. To this end, it is recommended that the carbide tooth be sharpened on its front and rear planes. Essentially, teeth can be ground along one front plane, but in this case the number of possible sharpenings is almost twice less than in case of sharpening along two planes. The figure below illustrates why this happens.
The last pass when sharpening circular saw blades is recommended to be made on the rear surface of the tooth. Standard metal removal rates. 0,05-0,15 mm.
Before sharpening, the saw blade should be cleaned of impurities, e.g. tar, and the sharpening angles checked. On some saws they are written on the disk.
Equipment and materials for sharpening of circular saw blades
When abrasive wheels (especially diamond wheels) are used, it is desirable to cool them with coolant.
With increasing temperature the microhardness of abrasive materials decreases. Increasing the temperature to 1000°C reduces microhardness by a factor of nearly 2 to 2.5 compared to microhardness at room temperature. Increasing the temperature up to 1300° C causes the hardness of abrasive materials to decrease by a factor of nearly 4-6.
Use of water for cooling could result in rusting of parts and machine components. Soap and certain electrolytes (sodium carbonate, soda ash, trisodium phosphate, sodium nitrite, sodium silicate, etc.) are added to water to eliminate corrosion.д.), which form protective films. In conventional grinding, soap and soda solutions are most commonly used, while in finish grinding the. 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. do not want to waste time on this.
To increase the grinding performance of abrasive wheels and to reduce the specific wear, the maximum grit size should be selected, which provides the required surface finish of the ground tooth.
To select the grit size of the abrasive, according to the stage of sharpening, you can use the table in the article about grinding stones. For example, in the case of diamond wheels, for roughing grinding wheels with 160/125 or 125/100 grit size can be used, for finishing. 63/50 or 50/40. Grinding wheels with grit sizes from 40/28 to 14/10 are used for removing burrs.
Circumferential wheel speed when sharpening carbide teeth should be about 10-18 m/s. This means that when using a wheel with a diameter of 125 mm the speed of the motor should be approx. 1500-2700 rpm. Sharpen more delicate grades at lower speeds in this range. When sharpening carbide tools, the use of harsh regimes results in increased stress and cracking, and sometimes chipping of the cutting edges, with increased wheel wear.
When using circular saw blade sharpening machines, changing the relative position of the saw and the sharpening wheel can be accomplished in various ways. By moving one saw blade (motor with a disc is stationary), simultaneous moving of saw blade and motor, moving only the motor with the disc (saw blade is stationary).
Many sharpening machines with different functions are available. The most complicated and expensive programmable complexes are able to provide fully automatic sharpening mode, in which all operations are performed without the participation of the worker.
In the simplest and cheapest models, once the saw has been set and clamped in a position that provides the desired angle of sharpening, all further operations. Turning the saw blade around its axis (turning it on the tooth), feeding it for grinding (bringing it into contact with the wheel) and checking the thickness of the metal removed from the tooth. are done manually by the worker. Such simple models are appropriate for home use when sharpening circular saws is occasional.
An example of the simplest machine for sharpening circular saw blades can be the system, the picture of which is shown in the photo below. It consists of two basic assemblies. the engine with the wheel (1) and the slide (2), on which the saw to be sharpened is mounted. Swivel mechanism (3) serves for changing the angle of blade tilt (when sharpening teeth with beveled front surface). The screw (4) moves the saw blade along the axis of the grinding wheel. This ensures that the required rake angle is set. Screw (5) serves for setting of the limiter in the desired position, which prevents excessive penetration of the disk into the interdental space.
Saw blade sharpening process
The saw is placed on the arbor, clamped by the tapered bushing (centering bushing) and nut and then aligned in a perfectly horizontal position by means of the mechanism (3). This ensures the bevel angle of the front plane (ε1) equal to 0°. On disc grinding machines without integrated angle scale in the tilting mechanism, this is done with a conventional pendulum-type angle gauge. At this point it is necessary to check the level of the machine.
By turning the screw (4) of the mechanism that ensures the horizontal movement of the mandrel with the grinding wheel, the desired rake angle is set. In other words, the saw is moved to a position in which the front plane of the tooth is firmly in contact with the working surface of the wheel.
A marker is used to indicate the tooth at which the sharpening is to begin.
HOW TO SHARPEN CIRCULAR SAW BLADES, SIMPLE JIG.
The motor is switched on and the front surface is sharpened. by bringing the tooth into 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 force with which the tooth presses against the abrasive 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. Repeat until the marker makes a complete circle, indicating that all teeth are sharpened.
Grinding a tooth beveled on the front plane. The difference between sharpening a beveled tooth and sharpening a straight one is that the saw must be set not horizontally, but with a slant. 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 set a positive angle (in this case 8°).
After that, every second tooth is sharpened.
After sharpening half of the teeth the angle of the saw blade changes from 8° to.8°.
Every other tooth is sharpened again.
Sharpening on the back plane. To sharpen the tooth on its back plane you need a sharpening machine that makes it possible to mount the saw in such a way that the back plane of the tooth is in line with the working surface of the abrasive wheel.
If you do not have a machine for sharpening circular saw blades
Exactly maintain the necessary sharpening angles while holding the saw in their hands by weight. A task impossible even for a person with unique eyesight and enviable hardness of hands. The most sensible way to do this is to. Make a simple device for sharpening, allowing the saw to be fixed 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. By putting the circular saw blade on it, it is possible to ensure perpendicularity of the front and back planes of the tooth relative to the saw blade. And if the upper surface of the stand is made movable. by fixing one side pivotally and the other. by means of a pair of screws that can be turned in and out. then it can be set at any inclination, obtaining the possibility to sharpen an oblique tooth along the front and back planes.
One basic problem remains unsolved, however. holding the same forward and backward angles of sharpening. It is possible to solve this problem by fixing the center of the saw relative to the abrasive disk in the required position. One way of doing it. Make a groove on the surface of the stand for the arbor on which the saw is mounted. Moving the mandrel with a disk on a groove, it will be possible to maintain the necessary forward angle of sharpening a tooth. But for sharpening circular saws with different diameter or angle of sharpening, it must be possible either to move the motor or the stand and its groove. Another way to provide the required angle of sharpening is more simple, and consists in installing the stops fixing the disk in the required position on the table. At the end of the article there is a video demonstration of such a device.
Device for grinding circular saw blades with movable stops on the table
Quality control of sharpening
GOST 9769-79 establishes certain tolerance values of grinding 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.
Proper sharpening of circular saw blades is largely ensured by a good tooling fixture. There are two options: the rigging can be removed from the tool and fixed in a vise using wooden blocks on a work table or perform grinding directly on the tool, then for fixation it is necessary to stick a block between teeth, having set it against some surface. It is important to remember that the saw must be de-energized before you sharpen it. Whichever method you choose, make sure the disc is firmly locked in place and does not rotate.
To help you know which tooth you have started sharpening, you should mark on the body of the blade with a highlighter. That way you will know you have come full circle when sharpening so you don’t have to sharpen a second time.
Manual sharpening of circular saw blades is done with a file. A tool with a flat blade is best suited. it can easily pass between the teeth. Please note that most of the wear is on the top cutting edge of the tooth. During sawing it interacts most intensively with the material and gradually rounds. The leading edge of the tooth is also ground very finely.
First sharpen the back side of the tooth. Carry the file through several times, using a small amount of force. Grind each tooth in alternating, even strokes.
It is important to remember! When sharpening circular saw blades, each cutting segment should be treated with equal force and the file should be filed the same number of times. This helps to evenly sharpen the whole disk, the teeth will be identical.
After sharpening each tooth in turn, when the wheel has completed a full rotation you will return to the starting point. After that you need to sharpen the front side of the teeth. Repeat the same procedure until the bit is completely turned.
It is important to remember! While sharpening, make sure the tooth tip remains perpendicular to the plane of the blade. This ensures a smooth and fast cut later on when sawing workpieces.
To be sure of the quality of the teeth sharpening, it is necessary to inspect them carefully. There should be no chipping, rips, or cracks on the cutting edges, and no glare on the edges. If the edges are shiny, carefully file them down.
Once all the teeth have been sharpened, check the cutting characteristics. Attach the cutting attachment to the tool, turn on the power and cut a block of wood for a test cut. Good sharpening is indicated by a clean cut, smooth running, and quiet operation. If you see excessive noise and unevenness in the cut of the material, check the height of the teeth. they may not be the same. To align all cutting segments, bring a marker to the cutting edge and turn the tool fully in the opposite direction to the direction of rotation. Examine the surface: each tooth should have a mark on it to help you compare the heights of all segments. Look for the teeth with the highest height and carefully reduce their length with a file.
Types of cutting teeth
Type of 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 the sawing of surfaces takes place.
- Straight tooth. It is most often used only for quick bevel cuts. Quality and precision are of little or no importance in this type of work.
- Oblique tooth. Their back plane is tilted to the right or left. On saws, these teeth often alternate, which is why they are called “alternate-slanted”. These teeth are the most common type of tool. The size of corners can vary, this is due to the coating of the surface to be processed. wood, chipboard, plastic. They are used for both longitudinal and transverse movements. Large bevel angles on tools are used when cutting double-sided laminated boards. This helps to avoid chipping of the material. The steeper the angle, the easier it is for the saw to cut through the surface. But this greatly increases the likelihood of tooth breakage. On some products, the teeth are not only slanted 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 separately, usually alternating with straight tines. During operation, trapezoidal teeth are above the straight ones, so they do the basic (rough) work of sawing. Straight teeth perform finishing work. saws of this design are used for sawing plastic, chipboard and fibreboard.
- Conical Tooth. This tooth type is considered a secondary tooth, as it only helps to cut the under side of the material (usually laminate). This design protects the surface from chips and cracks. Tapered tines usually have a straight leading edge, but it can also be concave. This type is used for finish cuts.
Important! Each type of tooth requires a thorough reworking when sharpening. Do not sharpen them at a single angle.
Basic sharpening methods
The circular saw blade is sharpened with a fine-grained abrasive wheel, along the planes that form the main working angle:
In the case of the combined version of the restoration of the edge, the front corner is sharpened first. If so, the disc can be resharpened 25 to 30 times during operation.
Removing a thin layer from the back of the tooth leads to a faster reduction in blade diameter and saw wear.
At home, you can do the sharpening of circular saws with your own hands. It is sufficient to use an oscillator to correct a tool with pobedite tips. In case of a large amount of work, a device from an angle grinder or milling machine is made.
Grinding circular saws with tungsten carbide inserts requires more force and is done on special machines and with a device with an abrasive disk.
Manual grinding on a flat grinding wheel.
- Fix an angle grinder with a grinding wheel stationary.
- Make a support for the circular saw blade. Its plane must be level with the axis of the sharpening wheel.
- Bring the tooth side until it is in contact over the entire area of the sharpening plane.
- Install 2 clamps on the sharpening table on the right and left. They help you align the plane to be sharpened quickly, without adjusting each tooth.
- Set the taper to the left fixture and turn until it stops at the right fixture after each turn of the disc by one step.
It is necessary to remove 0,12-0,15 mm from the cutting plate during one sharpening.
To sharpen the circular saw on the back plane, turn it around and reposition the clamps.
Angle grinder for grinding circular saws
Using the machines
In mass production it is necessary to sharpen circular saw blades regularly. For this purpose special machines with wheels are available in the workshops. Each of them has a device that aligns the tooth to the wheel at the desired angle and allows the tool to move progressively.
In special automatic operating equipment, the disk performs only a rotary movement by the size of a given step. Rotating abrasive wheel drives up after each turn and grinds the next plane.
You can sharpen the carbide disc by hand, with an arbor, but the effect will be poor. Without special devices it is impossible to maintain the angle and remove a uniform layer from all planes.
Circular saw sharpener, overview and comparison
|Model||LTT MF126A||SZTP 600T||LTT MF1263||Hytec PP-480Z|
|Resharpening wheel size,mm||100||150||150||480|
|Diameter of sharpening saws, mm||160-600||140-170||100-630||65-480|
SPT 600 LTT MF1263 Hytech PP-480Z
Ways of increasing the service life of circular saw blades
Tooth angles for sharpening
The process of forming a new cutting edge is laborious and time-consuming. For this reason, a number of conditions are recommended to increase the life of the disc.
Please first read the manufacturer’s recommendations. They specify the number of revolutions (maximum and minimum) for different types of materials to be processed. For metal this parameter should be less than for wood.
Solid tips have a longer service life. However, they are more likely to chip and break. Alternative soft is practically not prone to such defects. But its lifetime is shorter than that of hard.
Roughness on the cutting surface is not allowed. They can cause chipping and cracking later on.
The video shows an example of a disc sharpening machine made by your own hands: