Circular saws. Methods for tensioning the saw blade Sawing solid wood
Preparing the saw includes jointing, setting and sharpening the teeth. The nature of the saw's operation is influenced by the shape, size and inclination of the teeth. Saws with isosceles teeth are recommended to be used only for cross-cutting, rectangular shape- for longitudinal and transverse, with inclined teeth - only for longitudinal.
Planing saw (Fig. 1) consists of aligning the tops of the teeth so that they are at the same height. To do this, a file is secured in a vice and the tips of the teeth are moved along it. The quality of jointing is checked by applying a ruler to the tops; in this case, there should be no gaps between the tops of the teeth and the edges of the ruler.
Setting . To prevent the saw blade from getting pinched in the cut, the saw teeth are set apart, that is, they are bent: even teeth in one direction, odd teeth in the other. In this case, not the entire tooth is bent, but only it top part(1/3 from the top of the tooth). When spreading the teeth, it is necessary to maintain the symmetry of the bends on both sides. For sawing hardwood, the teeth are set apart by 0.25...0.5 mm on each side, and for softwood - by 0.5...0.7 mm.
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| Rice. 2. Universal wiring: 1 - plate; 2 - adjusting screws; 3 - scale showing the size of the divorce; 4 - a screw with a stop that regulates the height of the tooth being bent; 5 - spring; 6 - lever for bending the tooth away from the saw. | Rice. 3. Template for checking the correct alignment of the saw teeth: 1 - saw; 2 - template. |
When sawing wet wood, the gap should be maximum, and dry wood should be 1.5 times the thickness of the saw blade. The width of the cut should not be more than double the thickness of the blade.
To set the saw apart, a novice carpenter is recommended to use a special set (Fig. 2). The correctness of the saw is checked with a template (Fig. 3), moving it along the blade. The saw is moved evenly, without using much force, as otherwise you can break the tooth.
The teeth are sharpened with diamond- or triangle-shaped files, with double or single notches. Before sharpening, the saw is securely secured in a vice on the workbench. The file is pressed against the tooth while moving away from you; when returning it, lift it slightly so that it does not touch the saw. You should not press the file tightly against the tooth, as this will heat up the file, which will lead to a decrease in the strength of the teeth.
The teeth of saws for longitudinal cutting are sharpened on one side and the file is held perpendicular to the blade. For cross cutting, the teeth are sharpened through one and the file is held at an angle of 60...70°. Bow saws are sharpened with a triangular file.
Saws with large teeth are set and sharpened, while saws with small teeth are sharpened, but not set. This is explained by the fact that in carpentry work they use completely dry material, the blade of bow saws is thin (0.5... 0.8 mm), the dimensions of the cut along the length are not particularly large, so the danger of clamping is almost eliminated, and small teeth with a pitch of 2... 3 mm is very difficult to spread. The cleanliness of sharpened but not set saws with a tensioned blade is much higher than that of one-handed hacksaws with a set blade, which is especially important when sawing tenons and eyes.
Understanding that the saw blade is an interdependent and interconnected system, each sawmill must constantly solve mutually exclusive tasks.
For example: how to remove bulges from a 100% forged saw? At the same time, without changing the general and one-sided forging? Or how, not only by not increasing, but also by decreasing the overall forging, to get rid of strong one-sided forging.
You will probably read in the sawmill literature that an experienced sawmill is able to combine straightening saw blade. Editing is indeed carried out using a variety of methods, the choice of which depends on the symmetry of the forging and the size of the saw blade. Sometimes excessive or asymmetrical forging of the saw blade does not allow you to start straightening at all. Therefore, it is first necessary to remove forging defects, and only after that proceed to the actual straightening.
Editing an under-forged saw
We forge on a bare anvil, combining straightening with forging. Forging on a flat anvil is possible if the bulges are small, that is, they allow you to get a rebound hammer blow and a high-pitched sound when struck. Or for a better fit of the saw to the anvil, we forge it on a convex anvil.
However, the saw can be straightened with a minimal increase in forging, for example, by placing thin thick cardboard between the anvil and the saw. Electrocardboard with a thickness of 0.5-1 mm or pressboard is suitable. In this case, you should select the required impact force, since on cardboard you need to hit weaker. Upon completion of editing, the disc will need to be forged to the required size. Editing on cardboard is especially good when working with thin saws. Both of these methods require .
Editing an optimally forged saw
It is carried out with unbalanced weak blows on a bare anvil or on cardboard. It may be necessary to remove excessive forging after finishing balancing, for example, with balanced blows at the point of the second zone “B” at a quarter force on both sides of the saw in 16 sectors.
Editing a symmetrically reforged saw
First, it is necessary to remove excess forging, which depends on the degree of reforging. This can be point 2 of zone “B” on both sides of the saw on 16 sectors. Or the first and third points of zone “B” on both sides in 16 sectors. The impact force is measured, as a rule, by a quarter. After this you can start editing.
Dressing a cup-shaped, under-forged saw
It is necessary to balance the saw blade on the bare anvil from the convex side. The number of points on a sector, as needed, can be from one to three in 16 sectors. For example, in 16 sectors, points 3 and 5 of zone “B”. During the final symmetry - on 4 sectors, point 4 of zone “B”.
Dressing of a cup saw with extremely positive one-sided (150-300%) and general forging.
This defect is corrected by asymmetrical intensive forging of the saw blade along the entire radius of the saw from the convex side in 16 or 32 sectors. Sometimes this may be necessary twice with the full force of the blow. At point 2 of zone "B" and points of zone "B" from 1 to 12 (or from 1 to 7). Depending on the size of the bowl on a convex anvil, with its radius from two to six meters. Thus, the existing tension is released into increasing the diameter of the saw blade. You should mark the saw blade with the “Star of David” in the center. Even beams are marked at 10, 7 or 6 points, and odd beams at 12, depending on the diameter of the saw. There will be fewer points with a smaller saw diameter.
Preparation for round work flat saws
The main operations for preparing circular saws for work are cutting and notching teeth, straightening, rolling or forging, sharpening teeth, setting them or flattening them, and installing the saw on the machine.
Trimming and notching teeth. These operations are performed in cases where the dimensions of the tool do not correspond to the conditions of its operation, the breakage of several adjacent saw teeth, or the appearance of cracks in the blade.
Rice. 102. Detection and elimination of defects in the shape of a circular flat saw blade: a-diagrams for detecting a disk defect by checking on both sides; b-location of blows when correcting defects; C-weak points; T-tight spots; B-bulges;
When cutting teeth, the gap between the punch and the matrix should not exceed 0.5 mm. The stamped contour of the teeth must provide an allowance of 1 -1.5 mm relative to the required profile. Final form The teeth are achieved by sharpening them on machines.
Editing saws. By editing, local and general defects in the shape of the canvas are eliminated. Straightening device circular saws shown in Fig. 101.
To detect defects in the shape of the blade, set the saw in a horizontal position on three supports and check it with a short straight edge on both sides. The established boundaries of the defects are outlined with chalk (Fig. 102).
The correction method depends on the type of defect. Weak spots “C” are corrected by striking a forging hammer with a round striker around the defect, gradually weakening as one moves away from it.
The blows are applied on both sides of the saw (Fig. 102 I). Tight spots “T” are corrected by blows of a forging hammer inside the defect zone, starting from the borders and ending in the middle. The blows are applied on both sides of the saw (Fig. 102 II).
Bulge “B” is corrected by striking a forging hammer from the side of the bulge (Fig. 102 III). In order not to change the overall tension of the blade, a cardboard or leather spacer is placed between the saw, placed with the bulge upward, and the anvil.
The bend of the saw “I” (folds at the jagged edge, bent areas, humpbackedness and one-sided wingedness of the disk) is corrected by blows with the correct bend of a hammer (with an elongated striker) either along the ridge itself at the bend, or, if the size of the defect is significant, from the edges of the bend to the ridge with sides of the convexity. The axis of the striker must coincide with the direction of the bending axis (Fig. 102III).
It is recommended to check the quality of saw editing using a special device (Fig. 101). In this case, the test takes place under conditions close to operational ones. The criterion for assessing the quality of straightening is the magnitude of the greatest deviation of the side surface of the saw (in the peripheral part) from the plane of the end surface of the saw.
The saw is considered straightened if deviations (in mm) from flatness (warping, bulging, etc.) on each side of the saw blade do not exceed for saws with a diameter (mm) of up to 450-0.1;
To straighten circular flat saws, use a PI-38 sawing anvil, PI-40, PI-41 forging hammers; straight hammers PI - 42, PI - 43; device for checking the quality of editing; calibration rulers PI - 44, PI - 45, PI - 46, PI - 47 and G1I - 48.
The length of the handles of straightening hammers should be 30 cm; weight of hammers with cross strikers - 1 kg, with oblique strikers - 1.5 kg; convex radius - 75 mm.
Rolling of saws is carried out in order to create the initial stresses necessary to compensate for the temperature stresses that arise when the saw blade is unevenly heated during the sawing process, and to reduce the risk of the occurrence of resonant states of the tool.
The essence of rolling is to weaken the middle part of the saw, due to its elongation when rolled between two working rollers under pressure.
A rolled saw acquires lateral stability of the gear ring during operation, i.e., the ability to withstand unbalanced lateral forces acting on the disk during sawing, and thereby ensure the straightness of the cut
It is enough to roll the saw along one circle with a radius of 0.8 R (where R is the radius of the saw without teeth) for 3-4 revolutions of the saw under the influence of the rollers.
The average roller pressure values for new unforged saws when rolling along one circle with a radius of 6.8 R should be set in accordance with the data in Table 25.
Table 25. Roller clamping force when rolling flat circular saws
|
Saw dimensions* mm |
Average clamping force |
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|
lparameter |
thickness |
kg |
according to the pressure gauge of the machine model PV-5*, Ki s/cm 1 |
|
315 |
1,8; 2,0; 2,2 |
1550; 1700; 1840 |
55; 60; 65 |
|
400 |
2,0; 2,2; 2,5 |
1550; 1700; 1980 |
55; 60; 70 |
|
500 |
2,2; 2,5; 2,8 |
1550; 1840; 2120 |
55; 65; 75 |
|
630 |
2,5; 2,8; 3,0 |
1700; 1980; 2260 |
60; 70; 80 |
|
710 |
2,8; 3,0; 3,2 |
1840;2120;2400 |
65; 75; 85 |
Depending on the initial stress state of the saw, the pressure of the rollers may fluctuate.
A correctly rolled saw when positioned in horizontal plane on three evenly spaced supports located inside the circle of the tooth cavities at a distance of 3-5 mm from it, with free sagging of the middle part it should acquire a uniform concavity (taper shape). The convexity values of rolled saws operating at cutting speeds of 40 - 60 m/s, measured on both sides at a distance of 10 - 15 mm from the edge of the central hole of the saw, must correspond to the values specified in Table 26.
If the required weakening of the middle part of the saw is not achieved, the saw is turned over and re-rolled with the same roller pressing force. Turning the saw over helps to slightly reduce the bending of the blade by the rollers. If the middle part of the saw has not received the necessary weakening, the rolling process is continued along the same circle with increased pressing force of the rollers.
Excessive weakening of the middle part of the saw during its re-rolling is corrected by rolling along a circle spaced 3 - 5 mm from the circumference of the tooth cavities. In this case, the pressing force of the rollers is taken from 10 to 30 kg, depending
from the initial stress state of the tool.
Sawing solid wood
To carry out longitudinal and transverse sawing of solid wood, today special circular saws are used, which are equipped with special plates made of hard alloys. As a rule, in the process of cross-cutting there are absolutely no problems with the use of saws, so we will focus on the features of using circular saws to carry out rip sawing.
When processing solid wood, it is necessary to use saws that fully correspond to the nature of the work being performed, are properly prepared, rolled according to all rules or forged, and that do not have any mechanical damage. Quite often, due to negligence and non-compliance with all the manufacturer’s recommendations for the use of circular saws (CS), they prematurely fail (break, wear out). Bulges appear on the canvas itself, as well as slacks that have characteristic burn marks. In addition, the teeth may chip or break off, and finally, in the most unfavorable case, the saw may simply break. Such consequences of non-compliance with basic rules and recommendations can often lead to disastrous consequences.
So, how can you save a really expensive tool from premature failure, while increasing the level of operator safety, as well as increasing the productivity level of sawing using circular saw equipment?
Saw design
To carry out a certain job, it is necessary to select circular saws that will have the smallest possible diameter. Saws with a small diameter are more stable and also provide a very high level of cut quality, which in turn makes it possible to achieve an increase in the volume of manufactured products and, accordingly, a higher level of quality in comparison with the use of the same cutting tool, but subject to a larger diameter. To ensure free movement of the saw in the cut, the teeth of the cutting tool (this saw) must be set apart or equipped with special carbide soldering. It is worth noting that if the teeth are set, it is necessary to bend only 1/3 of the tooth height. Saws with soldered hard alloys (soldered special plates that are made of hard alloy) or stellite do not need this set of teeth at all.
Longitudinal swaddling
In the process of longitudinal sawing, the sharpening of the tops of the teeth should be straight, without any inclinations. The front and rear sharpening angles, depending on the type of material being processed (cut), should not exceed the limits of 15°-25°. The width of the tooth tip (blade length) should be 0.6-1.6 millimeters wider than the thickness of the saw blade. In other words, the width of the cut is equal to: S = b + 2S1, where b is the thickness of the saw blade in millimeters, and S1 is the widening on the side in millimeters.
The widening on the side can be completely different. This depends on the degree of hardness of the wood being processed, as well as on its state of aggregation (in other words - warm, freshly cut, dried or frozen, etc.). For example, under conditions of processing raw wood (wet and soft wood, viscous), the maximum maximum expansion on the side can be from 0.8 to 0.8 millimeters. Moreover, in the case of processing dry (dried) hard wood, such broadening can be at least 0.4-0.5 millimeters. This is explained by the fact that, due to the frictional forces that arise during the cutting of wood and at the same time leading to strong heating of the saw body, the elastic restoration of the processed wood in the cut in different states of aggregation is carried out differently. The least recovery in a cut occurs in dry, hard, and frozen wood, while the maximum level of elastic recovery occurs in soft, wet and viscous wood.
Cleaning knives (multexes)
Special plates can be soldered into the body of the saw, which are made of hard alloy (so-called cleaning knives or multitex). During the process of work (cutting), these plates, due to the fact that their width is less than the width of the tooth blade, do not rub against the walls of the cut at all. Moreover, even in conditions of loss of flatness (stability) of the disk, for some reason, friction of the saw blade on the cut, thanks to the cleaning knives (multexes), is completely eliminated. These soldered plates preserve and protect the saw blade, as well as the saw itself as a whole, from the occurrence of too high a heating level, which can damage the saw. It is highly desirable that in the process of sawing materials that have a thickness of more than 100 millimeters, the saws are equipped with such multiplexes.
Preparing for use of a circular saw (CS)
Before installing a circular saw (CS) on the equipment, it must be properly prepared for work. In particular, this applies specifically to the blade of such a cutting tool. It is necessary to create internal mechanical stresses in the canvas. Modern circular saws without internal stresses are absolutely unsuitable for use. This is explained by the fact that they are characterized by lateral beating, as well as a low level of stability of the blade during sawing. At the moment of processing (sawing) of the material, such saws “float”, in other words, the DP blade loses its stability, after which in the very next moments it receives quite large burns.
The presence of internal stresses in circular saw blades is the most important prerequisite for the implementation of the most successful work such a tool. This is explained by the fact that during the work, the tooth area (crown) heats up more strongly than in other areas, and thermal compressive stresses appear. It is on them that tangential stresses from centrifugal force are imposed. Both of these stresses are summed up, which could inevitably lead to the most Negative consequences for a tool (circular saw). It is precisely because of this that there is a need to take measures that will eliminate such phenomena, resorting to rolling or forging the saw body.
In order to prevent the area of the saw teeth from taking on a wave-like shape during the sawing process, it is necessary to extend the middle zone of the circular saw. In this case, the edge of the saw itself gains freedom to stretch and the saw, while rotating, remains flat. Stresses in the middle sector of the saw blade arise through rolling or forging (in other words, blows with a special hammer on a special straightening anvil). Rolling of a circular saw blade is carried out using special equipment. In progress manual editing When using a disk blade, blows with a hammer must be applied according to a special pattern, depending on the characteristics of the saw itself, the cutting modes, the feed speed of the material being processed, as well as many other factors. A properly tensioned circular saw that is installed vertically should not vibrate at all when punched in the middle.
Internal voltage control
Controlling internal stresses in a circular saw can be done using the following methods: you need to slightly tilt the blade with your left hand, while right hand attach a special straight edge to the canvas. In this case, a light gap should appear, which is a sign of the presence of internal stresses. Exactly the same light gap should be present when checking the other side of the saw blade. Approximate values of the light gap for a cutting speed of 50 meters per second: 0.3-0.5 millimeters, provided that the saw diameter is 400-800 millimeters and 1.6-1.8 millimeters for saws with a diameter of 1000 millimeters.
Selecting the number of teeth on a circular saw
In order to achieve a high level of cutting quality, very great importance has the number of teeth of a circular saw. General rule is as follows: to cut thinner materials, it is necessary to use saws that have a large number of teeth, while to cut thicker materials, it is necessary to use circular saws with fewer teeth. To cut solid wood, at least two and maximum four teeth must work simultaneously. If the material being cut contains less than two saw teeth, the saw blade will not be able to function stably and reliably. However, if there are more than four teeth in the material being processed (in the cut), then the outer (crown) area of the circular saw will become unacceptably hot. In this case, the saw loses its flatness and may well fail due to the friction force of the disk against the walls of the material being cut.
Most optimal quantity teeth (Z), which should be in the material being processed, can be calculated using a simple formula: Z = (H/t) +1, where H is the cutting height (in millimeters), and t is the pitch of the saw teeth (in millimeters).
In any case, regardless of the material being processed and the size and characteristics of the saw, there should always be more than one tooth in the material being processed. Otherwise, it is absolutely impossible to provide any guarantee of straightness of sawing. The most optimal number of teeth in a cut is two to three teeth. Too many teeth on the saw is main reason increasing the load level on the drive motor. It is for this reason that the drive motor must have sufficient high level power. The tooth pitch t (in millimeters) can be determined by the following formula: t = Dπ/z, where “D” is the diameter of the saw itself (in millimeters), and “n” in turn is equal to 3.14, while Z is the number circular saw teeth (in units/pcs).
Tooth pitch DP
A large tooth pitch of a circular saw, which ranges from 30-45 millimeters, is recommended for use in the process of longitudinal sawing of wood, at high cutting heights, or when sawing soft wood. In turn, the fine pitch of the teeth of circular saws is recommended for use in conditions of cross-cutting wood, in conditions of a small cutting height, or in the process of cutting the hardest types of wood. In the process of choosing a circular saw for sawing solid wood, it is the shape of the tooth profile that plays a significant role. It is worth remembering that in the process of sawing hardwood, as well as in the process of sawing frozen wood, the shape and volume between the tooth cavity extremely significantly affects the level of quality, as well as the speed of sawing.
In conditions of a sufficiently large number of teeth and, accordingly, a small cavity between the teeth, very fine sawdust is formed. At the same time, removing such sawdust from the cut becomes difficult, and some of the sawdust gets between the walls of the cut and the body of the saw. Thus, the saw begins to heat up, and a very large amount of resin, as well as dust, sticks to the saw blade. In this case, the saw begins to burn and, as a result, becomes dull quite quickly. Due to this, the operator is forced to sharpen such a saw quite often. In addition, electricity consumption per unit of manufactured products increases sharply.
Feed rate
In the process of mechanically feeding material into the sawing area, it is worth choosing a speed level at which the feed per tooth (Uz) will be 0.2-0.7 millimeters under conditions of processing raw wood and 0.1-0.3 millimeters if dry wood is processed. On given value influences the number of teeth and is ensured provided that the material being processed is fed into the cutting area at a feed rate (m/minute): U = UzZn/1000, where Uz is the feed per tooth (in millimeters), Z is the number of teeth of the saw used, and “n” is the saw shaft rotation speed – 1/min. (revolutions/minute).
If we know the feed speed, saw rotation speed, as well as the optimal feed per tooth value for different varieties wood, as well as types of materials, then we have the opportunity to independently select the most correct and suitable number of teeth that the circular saw will have. Feed per tooth values for different materials are given in the table.
Minimum feed speed of processed material
The level of speed of mechanical feeding of the processed material must be no less than 20-30 meters per minute. Under conditions of lower feed rates, increased (rapid) wear of the saw teeth occurs, overheating of the cutting tool and, as a consequence, failure of the saw. To process materials, saws must be extremely sharp. Sawing wood using dull tools significantly increases the consumption of electrical energy, and also deteriorates the quality of the manufactured product and, undoubtedly, is one of the main reasons for saw failure.
Of utmost importance for the most stable operation, as well as the durability of the circular saw, is the technical condition of the processing equipment, as well as the method of feeding the processed material into the processing area (direct sawing). If the equipment has significant (exceeding 0.02 millimeters per 100 millimeters of length) radial runout of the saw shaft, it is imperative that all problems be corrected without delay. It is most advisable to place the saw on the shaft, and also check the saw for lateral runout using a special indicator. Depending on the diameter of the tool (saw) are allowed maximum deviations from the stroke plane, which range from 0.01 millimeters to 0.03 millimeters.
On equipment that has a roller feed, in the vast majority of cases, as a rule, the exhaust system, which removes sawdust from the saw box formed during processing, is attached to the machine from below. Along with the generated sawdust, pieces of broken bark, as well as other industrial waste, which can quickly clog the chip discharge channel, also enter the exhaust system. At the same time, productivity exhaust system will decrease significantly after sawing 10-15 beams. As a result of such actions, chips from the saw box practically cease to be removed, which in turn entails very rapid heating of the saw blade used for processing, as well as its failure. Taking into account such features, it is most preferable and advisable to use equipment equipped with a caterpillar feed of the processed material into the sawing area.
The most common problems in the process of sharpening circular saws:
- The service life of the circular saw does not correspond (is less) to the resource declared by the seller of this instrument;
- A circular saw is not able to withstand a sufficiently large number of sharpenings.
The number of sharpenings of DP equipped with carbide tips depends on a number of factors:
- Depending on the quality level of the hard alloy;
- From the material that needs sawing;
- From correct operation (compliance with all rules and recommendations);
- On the amount of sawn material;
- From the timeliness of sharpening the saw;
- From technical condition technological equipment, with the help of which sawing is carried out;
- From the production culture, as well as from compliance with all technologies and rules;
- And finally, from the processing equipment itself, with the help of which sharpening is carried out.
Circular saw quality
Most good tool Accordingly, it has a high cost, however, such a tool lasts quite a long time. The quality of the saw depends on what kind of carbide alloy is used by the manufacturer. In its turn mechanical properties hard alloys are established using the percentage of carbides, as well as binders, and the particle sizes of the hard alloy powder. In addition, they can be influenced by technological process preparation of the mixture, baking modes, processing modes during the grinding process, as well as methods for soldering cutting plates onto the body of the cutting tool itself (saw). It is worth adding that the highest level of hardness is distinguished by plates made from an alloy with the lowest cobalt content (3-5%). However, provided that a certain amount of titanium carbide is present in the composition of the hard alloy, the flexural and impact strength levels of the alloy will decrease. Increasing the cobalt content in the binder reduces the level of hardness, but at the same time the flexural and impact strength of the alloy increases. Thus, a low-quality alloy quickly breaks down and wears out. In the process of sharpening, to correct the geometry of the tooth, it becomes necessary to remove a large layer of soldered carbide, which in turn entails a decrease in the number of sharpenings of the saw (in other words, a decrease in the service life of the tool).
Selection of saw depending on the material being processed
Among other things, the material that is to be sawed can also affect the operational (mechanical) parameters of the cutting tool (saw). Due to this, there is a need to implement the most correct selection tool in absolute accordance with its intended purpose. Special catalogs can help you with this task, in which the largest manufacturers indicate for what material this or that tool (saw) is intended. In addition, these catalogs contain all the necessary information on the diameter, as well as the number of saw teeth for processing the corresponding materials. Processing low-quality (contaminated) material can also lead to the destruction (destruction) of the hard alloy soldering. This, in turn, means that in the process of sharpening a low-quality tool it is necessary to remove a very large layer, in comparison with a tool that is made of a high-quality carbide alloy.
Implementation correct use cutting tool, as well as the amount of processed (sawn) material are interrelated things. For example, if a tool is used to solve the most complex and voluminous tasks assigned to production, for which this tool is absolutely not intended (it is worth remembering that the cutting tool manufacturer’s catalog contains information about the approximate volume of sawing before sharpening, and the level of feed speed of the material being processed, and the number of revolutions of the circular saw), then sooner or later (or rather sooner) such a tool will begin to fail. Unfortunately, quite often manufacturers ignore the recommendations of tool manufacturers on the use of circular saws, which contain information about the volume of sawing (duration) between sharpenings they are designed for. Such unlucky owners of the instrument use its flesh until fringes, mossiness or chips appear on the material, which is extremely unacceptable and entails extremely negative consequences.
Circular saw sharpening equipment
One of the most important factors The productivity of the tool lies in the equipment on which the circular saw is sharpened. Here, quite a lot depends on what kind of equipment it is - automatic or semi-automatic. For example, sharpening a circular saw with carbide tips using automatic equipment from European companies makes it possible to ideally maintain the distance between the teeth, the configuration of the teeth, as well as the factory sharpening angles. One of the main advantages of this equipment is the minimum level of movement of the sharpening head, which is 0.01 millimeters. In one pass of the sharpened area, with its help it is possible to remove a layer of hard alloy with a thickness of no more than 0.02 millimeters. The geometric ratio of the height and thickness of the tooth for a circular saw in order to increase the level of stability of the teeth in the cut is approximately 1: 3-5 (in other words, if the thickness of the tooth is three millimeters, then its height will be approximately 9. up to 15 millimeters). 1: from 3 to 5, leave as is - this means that in the case when, in the process of sharpening the front edge of a tooth, it is necessary to remove, for example, 0.02 millimeters (thickness), then along the rear edge it is necessary to remove 0.06-0, 1 millimeter of carbide (height) so as not to disturb the geometric relationship and therefore the mechanical properties of the tooth.
In practice, it was found that by removing such an amount of hard alloy in one sharpening using automatic sharpening equipment, the saw can be sharpened up to 25 times. Thus, in the process of sharpening with the help of such equipment, the service life of the tool increases, which in turn reduces the cost of updating the saw. In the process of sharpening using semi-automatic, and even more so using the simplest sharpening equipment, the service life of the tool is reduced by at least 30-40% in comparison with sharpening using automatic equipment for sharpening the tool.
FOR WHAT REASONS CAN CHIPS APPEAR ON A TOOL DURING THE INITIAL PERIOD OF WORK?
During the operation of a cutting tool, the time during which it wears out can be divided into two periods:
- Emergency wear period. At the very beginning of using a cutting tool, at a time when micro-chipping of the cutting edge occurs, which is the cause of chipping;
- Time of gradual (monotonous) wear. In this case, wear (abrasion, dullness) work surface The cutting of the tooth blade occurs gradually during the operation of the saw.
In the catalogs of tool manufacturers who have already proven themselves exclusively with positive side, there are necessarily tables of the speed of feeding the material being processed, as well as the speed of cutting of circular saws. All these data are absolutely consistent with specific saws, as well as materials. If these parameters do not correspond to reality (are not maintained), then the level of quality of the processed surfaces decreases, and the working tool is subjected to high loads. As a result of this, on cutting edge chips occur, the properties of such an edge are lost, which entails a decrease in the service life of such a saw (a decrease in its service life), while a significant overconsumption of electrical energy occurs.
The cutting speed of the saw V (m/s) is determined using the rotation speed of this tool, as well as its diameter: V = Dπn/60, where D is the diameter of the tool itself (in millimeters), “n” is equal to 3.14, and “n” in turn is the number of tool revolutions (1/min, rpm).
Basic rules for using a circular saw
- The processing equipment used must be in good working order, and absolutely no spindle runout is allowed;
- The clamping flanges (saw washers) must have absolutely identical diameters, which are equal to at least 1/3 of the diameter of the cutting tool (saw) used. The diameter of the flanges (d) is determined by the following formula: d = 5√D, where D is the diameter of the cutting tool (in millimeters), and d is the diameter of the flange (in millimeters);
- The installation rings and washers must be perfectly parallel;
- The cutting tool (saw) must protrude above the workpiece by at least the height of the tooth, but not less than 5 millimeters;
- The rounding of the cutting plate of the tooth (blade) before the next sharpening should not exceed 0.2 millimeters;
- Before proceeding with the installation of cutting tools on processing equipment, their surface must be cleaned the best way using a solvent. ATTENTION: do not use caustic-based solvents!;
- It is necessary to strictly observe the cleanliness of the flanges, as well as the rings;
- It is strictly necessary to ensure that the saw body is always parallel to the guides, as well as the ruler.
Dressing circular saws is performed to eliminate local defects: tight and weak spots, bulges or wingedness that appear as a result of improper use of saws. The location and nature of the defects are determined before editing using a long (equal to the diameter of the saw) and short, equal to ½, control rulers, applying them to the surface of the disk. When determining defects, the saw is placed vertically on its edge or put on a testing spindle. In order not to make mistakes during editing, the boundaries of the detected defects are outlined with chalk, and the nature of the defect is noted conventional signs(+ bulge, - depression).
Weakness characterized by the fact that when the saw blade is bent in any direction, a depression is formed on the inner (concave) side, and a bulge (hump) is formed on the opposite side. A control ruler attached to the disk with inside, forms a light slit in the middle of the length of the ruler (Fig. 1, d). Weak spots are eliminated by hammering near and along the edges of the weak spot.
Tight spot characterized by the fact that when the saw blade is bent in any direction, a bulge is formed on the inner (concave) side, and a depression is formed on the opposite side. A control ruler, applied to the disk from the inside, where there is a tight spot, forms a light slit at the ends (Fig. 1, g). This defect is eliminated by double-sided forging in a tight spot.
Bulge- local unilateral convexity. It is characterized by the fact that when the saw is bent in any direction, a hump is always formed on one side of the disk, and a bulge is formed on the opposite side, i.e., the hump and depression do not pass from one side of the disk to the other, this is what distinguishes a bulge from a tight spot. The bulge is eliminated by hitting the hump with a hammer (Fig. 1, j).
wingedness defined as double and bending of the saw blade. It can be eliminated by straightening the disc along the ridge of the bend on the side of the convexity.
Forging circular saws is performed to increase the lateral stability of the ring gear. It is carried out manually on an anvil with special forging hammers. The section of the saw being forged must lie tightly on the anvil, which is made somewhat convex for this purpose. If the saw does not have any defects, forging is performed along 12-16 radii, 6-8 blows are applied to each of them, moving them from the periphery to the center. For a more correct distribution of blows, before editing, mark the saw, apply a series of concentric circles and radii. The blows are applied at the points where the circles intersect with the radii (Fig. 1, b). Forging begins at a distance of 20-30 mm from the cavity of the teeth and ends before reaching the central part of the saw, covered with a washer at 30-40 mm.
Having forged the saw on one side, you need to forge it on the other side in the same order, striking the impact marks on the first side. To obtain more visible imprints, the surface of the anvil should be lubricated with oil.
The degree of forging is determined by the amount of deflection of the middle part of the saw. Check the deflection arrow using a long control ruler, setting the saw in a horizontal position so that its middle part can sag freely (Fig. 1, a). With proper forging, a gap is formed between the ruler and the middle part of the saw, which evenly increases from the edge of the teeth to the center of the saw. The clearance of the other side of the disk should be the same as the first, i.e. ±0.2 mm. The amount of clearance is determined with a probe or indicator ruler. The optimal amount of deflection in the middle part of the saw, depending on the diameter and number of revolutions, is taken from the table. 
If, after forging, the deflection of the middle part of the saw is insufficient, the editing is repeated. The hammer blows during repeated straightening are located between the blows of the first forging (Fig. 1, c).
A correctly forged saw, placed with a hole on a finger or a wooden pin, produces a clear sound when struck lightly with the hand on the bottom.
During operation, the condition of the saws is checked at least after 3-4 sharpenings.
Conical saws are forged in the same way as saws with a flat disk, and the clearance value is determined only from the flat side and is taken equal to 0.3-0.5 mm for a saw diameter of 500-800 mm.
