Editing circular saws with compensators. Preparing to drink. Three types are hammer saws


Solid wood sawing

To carry out longitudinal as well as transverse sawing of solid wood, special circular saws are used today, which are equipped with special hard alloy plates. As a rule, in the process of transverse sawing, there are absolutely no problems with the use of saws, so we will focus on the features of using circular saws for longitudinal sawing.

In the process of processing solid wood, it is necessary to use saws that are fully consistent with the nature of the work being carried out, properly prepared, rolled according to all the rules or forged, and also which do not have any mechanical damage. Quite often, due to neglect and non-compliance with all the manufacturer's recommendations on the use of circular saws (DP), they prematurely fail (break down, wear out). Bulges appear on the canvas itself, as well as slacks with characteristic burn marks. In addition, the teeth may break out or break off, and finally, in the worst case, the saw may simply break. Such consequences of non-compliance with elementary rules and recommendations quite often can lead to disastrous consequences.

And so, how to save a really expensive tool from premature failure, while increasing the operator's safety level, as well as increasing the productivity of cutting using circular sawing equipment?

Saw design

To carry out certain work, it is necessary to choose such circular saws that will have the smallest permissible diameter. Saws with a small diameter are more stable, and also provide a very high level of cut quality, which in turn provides an opportunity 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 larger diameter. In order to ensure the free movement of the saw in the cut, the teeth of the cutting tool (this saw) must be bred or equipped with special hard alloy solders. It is worth noting that in case of tooth divorce, only 1/3 of the tooth height needs to be bent. Saws with brazed carbides (soldered special plates that are made of hard alloys), or stellite, this tooth setting is completely useless.

Longitudinal swaddling

In the process of longitudinal sawing, the sharpening of the tops of the teeth should be straight, without any inclination. The front as well as the rear grinding angle, depending on the type of material being processed (sawn), 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: S \u003d b + 2S1, where b is the thickness of the saw blade in millimeters, and S1 is the broadening to the side in millimeters.

Side broadening can be completely diverse. It depends on the hardness of the processed wood, as well as on its state of aggregation (in other words, warm, freshly chopped, dried or frozen, etc.). For example, in the conditions of processing raw wood (wet and soft wood, viscous), the maximum broadening to the side of the maximum can be from 0.8 to 0.8 millimeters. Moreover, in the case of processing dry (dried) solid wood, such a broadening can be at least 0.4-0.5 millimeters. This is due to the fact that due to the friction forces arising during the sawing of wood and at the same time leading to strong heating of the saw body, the elastic recovery of the treated wood in the cut of various aggregate states is performed differently. The smallest restoration in the cut is carried out precisely in dry, hard, and also frozen wood, while the maximum level of elastic recovery occurs in soft, moist and viscous wood.

Cleaning knives (multieks)

Special plates can be soldered into the body of the saw, which are made of hard alloy (the so-called cleaning knives or multieks). In the process of carrying out work (cutting), these plates, due to the fact that their width is less than the width of the tooth blade, does not rub against the walls of the cut. Moreover, even in conditions of loss of flatness (stability) of the disk, for some reason, the friction of the saw blade on the cut, thanks to the cleaning knives (multieks), is completely excluded. These soldered plates save and protect the saw blade, as well as the saw itself as a whole from the occurrence of too high a level of heating, which can disable 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 cartridges.

Preparing for the work of a circular saw (DP)

Before you install a circular saw (DP) on the equipment, it must be properly prepared for work. In particular, this applies specifically to the blade of such a cutting tool. In the canvas, it is necessary to create internal mechanical stresses. Modern circular saws without internal stresses are absolutely not suitable for use. This is due to the fact that they have inherent lateral beats, as well as a low level of blade stability during sawing. At the time of processing (sawing) the material, such saws “float”, in other words, the DP blade loses its stability, after which it gets quite large burns in the very near moments.

The presence of internal stresses in the saw blades is the most important prerequisite for the most successful operation of such a tool. This is due to the fact that in the process of performing work, the tooth region (crown) heats up more strongly, in comparison with other regions, and thermal compression stresses appear. It is on them that tangential stresses from centrifugal force are superimposed. Both of these stresses are summed up, which inevitably could entail the most negative consequences for the tool (circular saw). It is thanks to this that there is a need to take measures that will eliminate such phenomena, resorting to rolling or forging the body of the saw.

In order for the saw tooth region to not take a wave-like shape during the sawing process, it is necessary to extend the middle zone of the circular saw. At the same time, the edge of the saw itself gets freedom of stretching and the saw, rotating, remains flat. Stresses in the middle sector of the saw blade arise by rolling or forging (in other words, blows with a special hammer on a special straightening anvil). Rolling a circular saw blade is carried out using special equipment. In the process of performing manual dressing of a disk blade, hammer blows must be applied according to a special scheme, depending on the characteristics of the saw itself, on the cutting conditions, on the feed rate of the processed material, and also on many other factors. A properly strained circular saw, which is mounted vertically, absolutely must not vibrate from punching in the middle.

Voltage control

The control of internal stresses in a circular saw can be carried out by the following methods: it is necessary to tilt the disk slightly with your left hand, while with your right hand attach a special calibration ruler to the blade. In this case, a light gap should appear, which is a sign of the presence of internal stresses. Exactly the same light clearance should be present during the inspection of the other side of the saw blade. Indicative values \u200b\u200bof the light gap for a cutting speed of 50 meters per second: 0.3-0.5 millimeters, provided that the diameter of the saw is 400-800 millimeters and 1.6-1.8 millimeters for saws having a diameter of 1000 millimeters.

Selecting the number of teeth on a circular saw

In order to achieve a high level of quality of sawing, the number of teeth of a circular saw is very important. The general rule is as follows: for sawing finer materials, it is necessary to use saws that have a large number of teeth, while for sawing thicker materials, it is necessary to use circular saws with fewer teeth. For sawing a massive tree, at least two and a maximum of four teeth should work simultaneously. In the event that there will be less than two saw teeth in the material to be sawed, then the DP will not be able to function stably and reliably. However, in this case, if there are more than four teeth in the processed material (in the cut), then the outer (crown) region of the circular saw will be unacceptably very hot. In this case, the saw loses its flatness and may well fail due to the friction force of the disk on the walls of the material being sawed.

The most optimal number of teeth (Z), which should be in the material to be processed, can be calculated using the simple formula: Z \u003d (H / t) +1, where N is the cut 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 guarantees of straightforward sawing. The most optimal number of teeth in the cut is two to three teeth. Too many teeth a saw has is the main reason for increasing the load on the drive motor. For this reason, the drive motor must have a sufficiently high level of power. The tooth pitch t (in millimeters) can be determined by the following formula: t \u003d Dπ / z, where “D” is the diameter of the saw itself (in millimeters), and “n” in turn is 3.14, while Z is the number teeth of a circular saw (in units / pcs).

Tooth tooth pitch

A large step of the teeth of a circular saw, which is within 30-45 millimeters, is recommended to be used in the process of longitudinal sawing of wood, at a high sawing height, or when performing softwood sawing. In turn, the fine pitch of the teeth of circular saws is recommended to be used in the conditions of transverse sawing of wood, in conditions of low cutting height, or in the process of cutting the hardest wood species. The shape of the tooth profile is quite significant in the process of selecting a circular saw for sawing massive wood. It should be remembered 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 greatly affects the quality level, as well as the speed of sawing.

In conditions of a sufficiently large number of teeth and, accordingly, a small one between the dental cavities, very small filings form. Moreover, the removal of such sawdust from the cut is difficult, and part of the sawdust falls 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 tar, as well as dust, adheres to the saw blade. At the same time, the saw begins to burn and, as a result, dull quite quickly. Thanks to this, the operator is forced to sharpen such a saw quite often. In addition, electricity consumption sharply increases in terms of one unit of manufactured products.

Feed rate

In the process of carrying out a mechanical feed of material to the sawing area, it is worth choosing a level of speed at which the feed per tooth (Uz) will be 0.2-0.7 millimeters in the conditions of processing raw wood and 0.1-0.3 millimeters if dry wood is being processed. This value is influenced by the number of teeth and is provided provided that the material being processed is supplied to the cutting area with a feed rate (m / min): U \u003d UzZn / 1000, where Uz is the feed per tooth (in millimeters), Z is the number of teeth used saw, and ”n” is the rotational speed of the saw shaft - 1 / min. (revolution / per minute).

In the event that we know the feed rate, the saw rotation speed, as well as the optimal tooth feed value for various types of wood, as well as types of materials, then we have the opportunity to independently choose the most correct and suitable number of teeth that the circular saw will have. The values \u200b\u200bof the feed per tooth for different materials are shown in the table.

The minimum feed rate of the processed material

The level of the speed of the mechanical feed of the processed material should be at least 20-30 meters per minute. Under conditions of lower feed speeds, enhanced (quick) wear of the saw teeth occurs, overheating of the cutting tool and, as a result, the failure of this saw. For processing materials, saws must be extremely sharp. Sawing wood using blunt tools significantly increases the consumption of electric energy, as well as worsens the quality level of manufactured products and, undoubtedly, is one of the main causes of breakage of the saw.

The technical condition of the processing equipment, as well as the method of supplying the processed material to the processing area (direct sawing) is extremely important for the most stable operation, as well as the durability of the circular saw. In the event that there is a significant (exceeding 0.02 mm per 100 mm length) in the equipment, the radial runout of the saw shaft, it is imperative to immediately eliminate all problems. It is most advisable to put the saw on the shaft, as well as check the saw for side runouts using a special indicator. Depending on the diameter of the tool (saw), maximum deviations from the plane of the stroke are allowed, which are from 0.01 mm to 0.03 mm.

On equipment with a roller feed, in the vast majority of cases, as a rule, an exhaust system that eliminates the sawdust formed during processing from the saw box is attached to the machine from below. Together with the resulting sawdust, pieces of breakaway bark, as well as other industrial waste, which are capable of quickly clogging the chip exit channel, fall into the exhaust system. At the same time, the productivity of the exhaust system will significantly decrease after the sawing of 10-15 bars. As a result of such actions, the chips from the saw box practically ceases to be removed, which in turn entails a very fast heating of the blade used for processing the saw, 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 to the sawing area.

The most common problems in the process of sharpening circular saws:

  • The resource of a circular saw does not correspond (is less) to the declared resource by the seller of this tool;
  • Circular saw is not able to withstand a sufficiently large number of sharpenings.

The number of DP sharpenings equipped with carbide tipped depends on a number of factors:

  • From the quality level of hard alloy;
  • From material that needs to be cut;
  • From the correct operation (compliance with all rules and recommendations);
  • From the amount of sawn material;
  • From the timeliness of sharpening the saw;
  • From the technical condition of the technological equipment, with the help of which sawing is carried out;
  • From the culture of production, 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

The most good tool, accordingly, has a high cost, however, such a tool serves for a long time. The quality of the saw depends on which carbide is used by the manufacturer. In turn, the mechanical properties of hard alloys are established using the percentage of carbides, as well as binders, by the size of the particles of the powder of the hard alloy. In addition, they can be influenced by the technological process of the preparation of the mixture, the modes of baking, the modes of processing during the grinding process, as well as methods of soldering the cutting inserts on the body of the cutting tool itself (saw). It is worth adding that the plates with the lowest cobalt content (3-5%) differ in the highest hardness levels. However, provided that a certain amount of titanium carbide is present in the composition of the hard alloy, the flexural and impact strengths of the alloy will decrease. An increase in the cobalt content in the composition of the binder decreases the level of hardness, however, this increases the bending, as well as the impact strength of the alloy. Thus, low-quality alloy is quickly destroyed, and also wears out. In the process of sharpening to correct the geometry of the tooth, it becomes necessary to remove a large layer of soldered hard alloy, which in turn entails a reduction in the number of sharpenings of the saw (in other words, a decrease in the tool life).

Selection of a saw depending on the processed material

Among other things, the material to be sawn is also able to influence the operational (mechanical) parameters of the cutting tool (saw). Due to this, there is a need for the most appropriate selection of the tool in absolute accordance with its purpose. In this task, special catalogs will be able to help you, in which the largest manufacturers indicate for which particular material this or that tool (saw) is intended. In addition, in these catalogs there are all the necessary information on the diameter, as well as the number of saw teeth for processing the relevant materials. The implementation of the processing of low-quality (contaminated) material is also capable of entailing the destruction (destruction) of brazing from carbide. 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 high-quality hard alloy.

The proper use of the 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 volumetric tasks posed before production for which this tool is absolutely not intended (it is worth remembering that the catalog of the manufacturer of the cutting tool contains information about the approximate amount of sawing before sharpening, and level of feed rate of the processed material, and the number of revolutions of the circular saw), sooner or later (sooner rather) such a tool will start to fail. Unfortunately, quite often manufacturers ignore the recommendations of tool manufacturers on the use of circular saws, which contain information on how much sawing (duration) between sharpening operations they are designed to. Such unlucky owners of the tool use its flesh until fringe, mossiness or chips on the material, which is extremely unacceptable and entails extremely negative consequences.

Equipment for sharpening a circular saw

One of the most important factors in the productivity of a tool is the equipment on which the saw blade is sharpened. Here, quite a lot depends on whether this equipment is automatic or semi-automatic. For example, sharpening a circular saw with hard alloy soldering using automatic equipment from European companies makes it possible to perfectly maintain the distance between the teeth, the configuration of the teeth, as well as the factory grinding angles. One of the main advantages of this equipment is the minimum level of movement of the grinding head, which is 0.01 mm. In one pass of the sharpened area with its help, it is possible to remove a layer of hard alloy with a thickness of not more than 0.02 mm. The geometric ratio of the height and thickness of the tooth for a circular saw in order to increase the level of tooth stability in the cut is approximately 1: 3-5 (in other words, if the tooth thickness is three millimeters, then its height will be from about 9, up to 15 millimeters). 1: leave from 3 to 5 as it is - this means that in the case when during grinding the front edge of the tooth needs to be removed, for example, 0.02 mm (thickness), then 0.06-0 should be taken along the back edge, 1 millimeter of hard alloy (height) so as not to violate the geometric relationship and, therefore, the mechanical properties of the tooth.

In practical terms, it was found that by removing such a quantity of hard alloy in one sharpening using automatic grinding equipment, the saw can be sharpened up to 25 times. Thus, in the process of sharpening with the help of such equipment, the life of the tool increases, which in turn reduces the cost of updating the saw. In the process of sharpening with the help of semi-automatic, and even more so with the help of simple grinding equipment, the operational resources of the tool are reduced by no less than 30-40% in comparison with the implementation of sharpening with the help of automatic equipment for sharpening the tool.

FOR WHAT REASONS ON THE TOOL CAN CHAINS APPEAR IN THE INITIAL PERIOD OF PERFORMANCE?

During operation of the cutting tool, the time during which it is worn out can be divided into two periods:

  • The period of emergency wear. At the very beginning of the implementation of the use of a cutting tool, at the time when the microchipping of the cutting edge is carried out, which is the cause of the appearance of chips;
  • The time of gradual (monotonous) wear. In this case, wear (abrasion, dulling) of the working surface of the tooth cutting blade occurs gradually during operation of the saw.

In the catalogs of manufacturers of tools that have already managed to prove themselves exclusively on the positive side, there are without fail tables of the speed of supply of the processed material, as well as the speed of cutting of circular saws. All this data is absolutely consistent with certain saws, as well as materials. In the event that 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, chips appear on the cutting edge, the properties of such an edge are lost, which entails a reduction in the life of such a saw (a decrease in its resource), and there is a significant waste of electrical energy.

The saw cutting speed V (m / s) is determined using the rotational speed of this tool, as well as by its diameter: V \u003d Dπn / 60, where D is the diameter of the tool itself (in millimeters), “p” is 3.14, and “N”, in turn, is the number of revolutions of the tool (1 / min, rpm).

General rules for using a circular saw

  • The processing equipment used must be in good condition, and absolutely no spindle runout is allowed;
  • Clamping flanges (saw washers) must have exactly the same 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 \u003d 5√D, where D is the diameter of the cutting tool (in millimeters), and d is the diameter of the flange (in millimeters), respectively;
  • Mounting rings, as well as washers, must be perfectly parallel;
  • The cutting tool (saw) must protrude above the workpiece at least to the height of the tooth, but not less than 5 millimeters;
  • The rounding of the tooth insert (blade) before the next sharpening, should not exceed 0.2 mm;
  • Before proceeding with the installation of the cutting tool on the processing equipment, their surface must be cleaned best with a solvent. ATTENTION: do not use solvents made on a caustic basis !;
  • It is necessary to strictly observe the cleanliness of the flanges, as well as the rings;
  • In the strictest possible manner, make sure that the saw body is always parallel to the guides, as well as the ruler.

Preparation of saws for work consists in preparing blades, teeth, installing saws in a machine and repairing saws. The operations for preparing the saw gears of various designs are practically the same.

Preparation of frame saws.  Preparation of frame saws consists of the following operations: identification and correction of defects in the shape of the blade; control the stress state of the canvas; rolling; final control of flatness and stress state of the saw blade.

Defects are detected by applying a control ruler to the surface of the saw laid on a calibration plate. The gap between the ruler and the web should not exceed 0.15 mm. Editing the saw is to correct local defects of the blade: bulges IN, tight places T  weak points FROM,  bending And (pic .. 44, a) Defective places are repaired by blows of the forging hammer at certain points of the saw laid on the anvil.

The stress state of the blade is estimated by the magnitude of the deflection of the saw blade 2, bent with a radius R \u003d  1.75 m (Fig. 44, b)The deflection arrow is measured with a test ruler and probes or a special ruler 1   with indicators 3   and evaluate the arithmetic average of two measurements: when the saw is positioned up, first with one side and then with the other. The optimum deflection value depends on the size of the saw and lies in the range from 0.8 to 0.35 mm.

Rolling of frame saws is one of the measures to increase the rigidity and stability of saws in work. In the process, the frame saw heats up, especially at the ring gear. The cutting edge lengthens and under the action of cutting forces loses a stable flat shape. The saw wanders in the cut, which leads to a wavy or curved cut. The rigidity of the frame saws is provided mainly by their longitudinal tension in the saw frame. However, only due to the longitudinal tension, it is not possible to provide the necessary rigidity of the saws, since the tension force is limited by the strength of the grips and the saw frame, which perceives the tension forces of all the set saws.

The essence of rolling is that the middle part of the saw blade 4 rolled under pressure between two rotating barrel-shaped rollers 5 and 7 (Fig. 44, in),  basing on a roller with a non-working edge. In the place of passage of the roller, the saw lengthens and stretches adjacent, non-rolled parts of the blade. As a result of the tension of the milled saw in the saw frame in the extreme parts of the saw there will be sufficient tensile stresses with relatively small tensile forces (Fig. 44, d, e).The number, location and order of drawing traces of rolling 1-5 is shown in Fig. 44, g.

At the end of the rolling, the flatness and stress state of the saw are evaluated as described above for non-rolled saws. If local defects are detected (deviation from flatness exceeds 0.15 mm), additional editing is performed.


Fig. 44. Preparation of frame saws for work:

a  - local defects of the canvas and the order of strokes during editing; b -  control of the stress state of the canvas; rolling of frame saws; in  -principal scheme: g -  location of rolling traces; d -  stress distribution in the saw after rolling and tensioning the saw; e - stress distribution in the saw after rolling

Preparation of circular saws.  Preparation of circular saw blades includes the following operations: assessment of the flatness and stress state of the blade, straightening the blade, forging and rolling the saw blade. The flatness of the canvas is evaluated by two indicators: the straightness of the disk in various sections and the end (axial) runout.

The maximum permissible deviations (mm) from flatness depend on the diameter of the saw and are in the range from 0.1 (for saws with a diameter of up to 200 mm) to 0.6 (for saws with a diameter of 1600 mm). To determine the end runout, the saw is mounted on the horizontal shaft of the device. The runout is measured with an indicator located perpendicular to the saw blade at a distance of 5 mm from the circumference of the tooth depressions during slow rotation of the saw with the shaft (Fig. 46).

Before starting measurements, the indicator 2 oriented relative to the plane passing through the end surface

of the main washer 7. For this, a calibration ruler is applied to the surface of the main washer and the indicator leg. The zero mark of the dial is brought to the big arrow of the indicator. When determining the flatness of the saw 3   mounted on a shaft 4,   clamped with a washer 5   and slowly rotate the handle 6.   The value of permissible face runout (mm) is from 0.15 (for saws with a diameter of up to 200 mm) to 0.6 (for saws with a diameter of 1600 mm).

Exceeding the standard values \u200b\u200bof non-flatness indicates the presence of defects in the canvas, which are divided into general (dish-shaped, winged, bending around the circumference) and local (weak spot, tight place, bulging, bending). All defects are corrected by editing the canvas (Fig. 47).

The method of editing depends on the type of defect. Weak spots C (/) are corrected by striking the forging hammer with a round striker around the defective spot, gradually weakening the blows as they move away from it. Impacts are applied on both sides of the saw. Tight places T (u  corrected by blows of the forging hammer inside the defect zone from the borders to the middle. Impacts are applied on both sides of the saw. Bulging In (III)  corrected by blows of the forging hammer from the side of the bulge. In order not to change the overall tension of the blade, a cardboard or leather pad is placed between the saw, which is raised upward, and the anvil. Bending of the saw (folds at the serrated edge, bent sections of the edge, humping and one-sided wing-likeness of the disk) is corrected by blows of a regular hammer (with an oblong striker) either along the bend ridge itself, or, if the size of the defect is significant, from the edges of the bend to the ridge from the convex side. The axis of the striker should coincide with the direction of the axis of the bend.

Fig. 46. \u200b\u200bDetection of defects in the shape of a circular saw blade

Fig. 47. Editing the saw blade:

  a -  defect detection circuit by double-sided verification;

b -location of hammer blows when correcting defects

Assessment of the stress state of the saw blade is made by the magnitude of the deflection of the saw under the action of its own weight. The saw is installed first with one side up, and then the other in a horizontal position with three supports spaced at equal distances from each other and at a distance of 5 mm from the circumference of the tooth cavities. The saw deflection is measured with a dial gauge (or with a straightedge and a set of probes) at three points on a circle with a radius of 50 mm and the average deflection is calculated. If this value does not meet the standard, the saw blade is forged or rolled.

Rolling consists in weakening the middle part of the saw due to its elongation when rolling between two working rollers under pressure (see Fig. 44, in).  The milled saw gains lateral stability of the gear during operation.

It is enough to roll a saw along one circle with a radius of 0.8 /? (Where K - radius of the saw without teeth) for three to four revolutions of the saw under the action of the rollers. Clamping force of rollers for new non-forged saws during rolling along one circle with a radius of 0.87? it is set depending on the diameter and thickness of the saw blade and is 15.5 ... 24 kN (for saws with a diameter of 315 ... 710 mm and a thickness of 1.8 ... 3.2 mm).

Correctly milled saw should acquire uniform concavity (plate). The concavity value of the milled saws working with cutting speeds of 40 ... 60 m / s, | measured on both sides at a distance of 10 ... 15 mm from the edge of the price- | the saw hole must correspond to the values \u200b\u200bspecified in the standard for saws (0.2 ... 0.6 mm for saws with a diameter of 315 ... 710 mm). After rolling, flatness is checked and the saw blade is corrected.

Equipment, instruments and tools for rolling circular saws: machine PV-35 or PV-20 with an attachment for rolling saws with a diameter of up to 800 mm; a device for controlling the degree of forging for rolling a circular saw with an hour indicator (saw diameter up to 710 mm); rulers for sawing, a set of probes. Forging saws is not mechanized and requires high qualifications. It consists in striking the forging hammer with a lump on the central pre-marked part of the saw lying on the anvil.

Fig. 48. Installation of saws on the machine:

a -  self-centering flange design; b -  installation of a proppant knife; in -  disk guide installation diagram

The degree of attenuation of the middle part of the saw is checked in the same way as when rolling (the standards are the same). If the middle part is not sufficiently weakened, the forging is repeated, striking between places of impacts of the first forging.

Installation of circular saws.  When installing circular saws, the following conditions must be met:

1. Saw plane 2   must be strictly perpendicular to the axis of the shaft, and the end runout of the radical flange 3   should not exceed 0.03 mm at a radius of 50 mm (Fig. 48, a).

2. The axis of rotation of the saw should coincide with the axis of the shaft. For this, the diameter of the saw’s bore hole should not exceed the shaft diameter by more than 0.1 ... 0.2 mm. With a larger gap, you must bore the hole and insert the sleeve into it. It is more rational to use flanges with a centering pin or with a centering cone 7 (see Fig. 48, a).

3. To ensure reliable clamping of the saw, the flanges contact the saw only with external rims 20 ... 25 mm wide. The diameter of the clamping flanges is selected depending on the diameter of the saw: d? F \u003d 5U7), where IN -  diameter of a saw, mm.

To prevent spontaneous loosening of the nut during operation, it must have a thread that is inverse to the direction of rotation of the shaft.

4. When sawing along the fibers in the plane of the saw, a proppant knife is installed behind it 4   at a distance of 10 ... 15 mm from the tops of the teeth (Fig. 48, b)  For flat saws, the thickness of the knife is equal to the width of the cut or 0.2 mm exceeds it. For conical saws, the knife has the shape of a wedge and its maximum thickness is 3 ... 4 mm greater than the thickness of the central part of the saw.

5. For saws with a diameter of more than 400 ... 500 mm, lateral guides 5 and 6   (Fig. 48, in),  axial limiting saw deviations. The guide pins are made of PCB, fluoroplastic or other antifriction materials.

The gap between the saw and the guides depends on the diameter of the saw:

Diameter of a saw, mm .... 125 ... 200 250 ... 300 400 ... 503 560 ... 800 More than 800

Clearance, mm ................. 0.22 0.30 0.35 0.42 0.55

6. The protrusion of the teeth above the material to be sawed should not exceed 10 ... 20 mm, if the design of the machine provides the possibility of its regulation.

Preparation of teeth saws for work.  In the preparation of the teeth of the saws to work includes notching the teeth, broadening the gear, sharpening and jointing of the teeth.

Tooth notching is performed if it is necessary to change the tooth profile or three (in total) or two teeth in a row are broken on the saw. Manual (type ПШ) or mechanical (type ПШП-2) saw benches are used for notching. Stamps and knives are made of 9XC steel with hardness after sharpening and tempering NKSd 55 ... 60. An allowance of 1 ... 1.5 mm relative to the required profile should be provided in the stamped tooth contour. The final shape of the teeth is achieved by sharpening them on the pilot machines. At the same time, the metal layer with defects formed during stamping is grinded off.

Gear broadening. The optimal broadening of the ring gear depends on the breed and the state of the sawn wood and lie in the range from 0.3 (hardwood) to 1.0 ... 1.3 mm  (soft rocks at high humidity) for circular saws.

Preparation for work of circular saws

The main operations for preparing circular saws for work are cutting and notching teeth, dressing, rolling or forging, sharpening teeth, their bending or flattening, installing the saw on the machine.

Trimming and notching teeth. These operations are performed in cases where the size of the tool does not correspond to the conditions of its operation, breakage of several adjacent saw teeth or the appearance of cracks in the blade.

Fig. 102. Detection and elimination of defects in the shape of a circular saw blade: a-circuit detection of disk defects by checking from two sides; b-location of impacts when correcting defects; C-weaknesses; T-tight places; B-bulges; I-bends

When cutting teeth, the gap between the punch and the die should not exceed 0.5 mm. The stamped contour of the teeth should include an allowance of 1 -1.5 mm relative to the desired profile. The final shape of the teeth is achieved by sharpening them on the machines.

Editing drank. Editing eliminate local and general defects in the shape of the canvas. The device for editing circular saws is 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 calibration ruler on both sides. Defined boundaries of the defects are outlined with chalk (Fig. 102).

The method of editing depends on the type of defect. Weaknesses “C” are corrected by striking the forging hammer with a round hammer around the defect with a gradual weakening as it moves away from it.

Impacts are applied on both sides of the saw (Fig. 102 I). Tight spots “T” are corrected by blows of the forging hammer inside the defect zone, starting from the borders and ending in the middle. Impacts are applied on both sides of the saw (Fig. 102 II).

The bulge “B” is corrected by striking the forging hammer from the bulging side (Fig. 102 III). In order not to change the overall tension of the blade, a cardboard or leather gasket is placed between the saw, which is placed upstream of the bulge and the anvil.

The bend of the “I” saw (folds at the serrated edge, bent sections, humps and one-sided wing-likeness of the disk) is corrected by blows of the correct bend of the hammer (with an oblong striker) either along the ridge 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 bulge. The axis of the striker should coincide with the direction of the axis of the bend (Fig. 102III).

It is recommended to check the quality of the saw straightening with a special tool (Fig. 101). In this case, the verification takes place under conditions close to operational. The criterion for assessing the quality of editing is the value 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.

A saw is considered straightened if deviations (in mm) from flatness (warping, bulges, etc.) on each side of the saw blade do not exceed for saws with a diameter (mm) up to 450-0.1; from 450 to 800 - 0.2; from 800 to 1000-0.3. Deviations from the flatness of the central part of the saw in the area of \u200b\u200bthe flanges should not exceed 0.05 mm.

For straightening circular flat saws, use saw-saw anvil PI -38, forging hammers PI -40, PI -41; correct hammers PI - 42, PI - 43; device for checking the quality of editing; rulers testing PI - 44, PI - 45, PI - 46, PI - 47 and G1I - 48.

The length of the handles of the right hammers should be 30 cm; the mass of hammers with cross strikers -1 kg, with oblique strikers - 1.5 kg; convex radius is 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 sawing and to reduce the risk of resonant states of the tool.

The essence of rolling is to weaken the middle part of the saw, due to its elongation when rolling between two working rollers under pressure.

The milled saw acquires lateral stability of the gear during operation, i.e., the ability to withstand unbalanced lateral forces acting on the blade during sawing, and thereby ensure the straightness of the cut

Rolling the saw is enough in 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 values \u200b\u200bof the roller clamp for new unforged saws during rolling along one circle with a radius of 6.8 R should be set in accordance with the data in table 25.

Table 25. Clamping force of rollers when rolling round flat saws

   Sizes of saws * mm

Average clamping force rshshkov

   meter

   thickness

   kge

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, one hundred pressure rollers may fluctuate.

A correctly milled saw, when placed in a horizontal plane on three evenly spaced bearings located inside the circumference of the tooth cavities at a distance of 3-5 mm from it, with free sagging of the middle part should acquire uniform concavity (tare). The curvature of milled 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, should correspond to the values \u200b\u200bindicated in table 26.

If the necessary weakening of the middle part of the saw is not achieved, the saw is turned over and re-rolled with the previous value of the pressure force of the rollers. Turning the saw helps to reduce the bending of the blade somewhat by the rollers. If the middle part of the saw has not received the necessary attenuation, the rolling process is continued along the same circumference with an increased force of pressure of the rollers.

Excessive weakening of the middle part of the saw during its rolling is corrected by rolling around a circle spaced 3 to 5 mm from the circumference of the tooth cavities. In this case, the pressure force of the rrlik is taken from 10 to 30 kg, depending
   from the initial stress state of the tool.

Edit  Saw consists in eliminating local defects - bulges, bends, tight and weak spots and giving the disk a flat shape. They correct the saw before forging, after checking the condition of the disk on both sides with the help of control rulers: short, not more than the radius, and long, equal to the diameter of the saw (Fig. 37). Laying a long ruler in various places along the diameter of the disk, determine the location and nature of the defect. By applying a short ruler to the surface of the disc, defect boundaries are established. First, defects that violate the flatness of the saw are eliminated: bends, folds, bulges. Further eliminate taut and weak points. Defects are corrected manually on the anvil using the correct hammers (CM. Fig. 30, b). The procedure for finding and editing defects in circular saws is similar to the order for frame saws.
Forging  represents a weakening of the middle part of the saw blade to increase its stability during sawing. Under the stability of a forged saw blade means the ability to withstand the impact on it of the lateral forces arising from sawing. Disk stability is determined by the following factors; thickness, uneven heating along the radius of the saw and the nature of its transverse vibrations. The following describes the working conditions of circular saws and the nature of the stresses they experience.

In a rotating disk under the action of centrifugal inertia, tangential and radial stresses arise. Tangential stresses on the periphery of the disk, depending on the speed of rotation of the saw shaft and the radius of the saw, are tensile (positive), they increase its stability. However, their value when working on woodworking machines does not exceed 60-200 kgf / cm2. The stresses from the cutting forces are also small and therefore cannot cause a loss of stability of the saw in the cut. Hazards to the stability of circular saws are stresses in the disk from uneven heating along the radius during the cutting process.
  The work of cutting, including the elastic-plastic deformation of wood and chips, friction, etc., is equivalently converted into heat, which is spent on heating the chips, material, tool and the environment. In this case, up to 12% of all the heat generated during cutting is used to heat the tool. The heat entering the saw body (body) through its end part extends in two directions: to the center of the saw (along the radius) due to the heat conductivity of its material and in the axial direction (normal to the plane of the saw blade) due to heat transfer by the side surfaces of the saw. Thermal resistance in the radial direction is 1000-1100 times higher than in the axial. As a result, a decrease in the maximum temperature at the tooth cavity to ambient temperature occurs on a relatively narrow section of the peripheral zone of the saw, limited by an internal radius equal to 0.8-0.85 of the maximum radius of the saw (including the teeth). These findings are confirmed by theoretical and experimental studies of the temperature fields of circular saws.
  In fig. 38, and a typical graph of the temperature distribution along the radius of the saw. The temperature drop during cutting is inevitable. The heating of the saws depends on many factors: sawing conditions, wood species, the geometry of the teeth of the saws, etc. Under normal (unforced) sawing conditions, the temperature difference ranges from 15-30 ° C. As a result of heating the narrow peripheral part, the saw lengthens, which is less heated (cold) middle part of the saw. The peripheral zone therefore receives negative compression stresses.

The nature of the stresses (σtτ, σtr) of uneven heating is shown in Fig. 38, b.
Stresses can reach 500-800 kgf / cm2 at temperature differences of up to 30-50 ° C. Excessive elongation of the cutting crown leads to its curvature and a general loss of flat balance of the saw. This circumstance is the main reason for the failure of the saw or its poor performance. Forging reduces the harmful effects of compressive temperature stresses. The weakening of the middle zone of the saw by blows with a forging hammer on an anvil or on a special forging machine (see Fig. 37, a, b, c) causes tension of the peripheral part of the saw and the appearance of tensile stresses in it, which compensate for compressive stresses from heating. The weakened middle zone does not prevent the peripheral extension under the action of centrifugal forces and the growth of tangential tensile stresses in it.
  Before forging, the saw should be marked out by drawing a series of concentric circles. Impacts must be applied along the radius from the periphery to the center at the points where the radius intersects the circle. The saw zone is subjected to forging, located at a distance of 20-30 mm from its periphery and 30-50 mm from the end surface of the clamping washers. When forging, it is necessary to ensure that strikes are made by the central part of the striker.
  To check the degree of forging, the saw is installed in a horizontal position on three cone-shaped supports and a test ruler is applied to its surface. The amount of clearance due to the sagging of the saw under its own weight characterizes the degree of forging. The clearance of the back side should be the same as the first.
  During operation, the tension of the outer part is gradually lost due to wear, heating during cutting, sharpening, etc. Therefore, the condition of the saw should be checked periodically (after 3-4 regrindings) and the necessary tension should be restored by secondary forging (see Fig. 37, c). The clearance (deflection arrow) for new circular saws, according to GOST 980-63, depends on the diameter, thickness of the saw and is approximately: for saws with a diameter of D \u003d 250 ÷ 360 mm, 0.1-0.4 mm; D \u003d 400 ÷ 710 mm 0.2-0.5 mm; D \u003d 800 ÷ 1500 mm 0.5-2 mm.
  Conical saws are forged in the same way as flat saws, and the clearance value is determined only on one side - flat. The deflection of the conical saws, depending on their diameter, should correspond approximately to the following values: for D \u003d 500 mm 0.3-0.35 mm, for D \u003d 600 mm 0.35-0.4 mm and for D \u003d 700 ÷ 800 mm 0.4-0.5 mm. Planing saws and saws equipped with carbide inserts are not forged.
A less common, but good method, having the same purpose as forging, is the method of rolling the middle zone of the saw along concentric circles. Rolling of circular saws can be performed with the same equipment as rolling of frame saws. For this, a prefix is \u200b\u200binstalled on the PV-5 milling machine to fix the saw (Fig. 39, a). Rolling of the middle zone can be replaced by rolling in one trace of the peripheral part at a radius equal to approximately 0.85 of the outer radius of the saw. The purpose of rolling, as well as forging, is to create tensile tangential stresses in the peripheral part of the saw. The degree of rolling is determined by the arrow deflection of the saw mounted on three supports.

There is another way to control the degree of preparation of the saw - determining the frequency of natural vibrations, which depends on its stress state. This method is relatively laborious and is used so far only in laboratory conditions.
  Circular saws have a number of critical revolutions at which the frequency of natural oscillations is equal to or a multiple of the rotational speed of the saw shaft, which leads to an increase in the amplitude of transverse vibrations of the saws at these revolutions or even to their loss of a flat equilibrium shape. The most dangerous are the second and third fan-shaped forms of loss of stability of the saw, and their frequency just lies in the range of revolutions of the saw shaft on the most widespread woodworking machines. Forging allows, due to an increase in the frequency of natural vibrations, to shift these dangerous forms of vibrations into the region of increased revolutions not used on machines.

The main operations for preparing circular saws for work are cutting and notching, straightening, rolling or forging, sharpening teeth, spreading or flattening them, and installing the saw on the machine.

Trimming and notching teeth. These operations are performed in cases where the size of the tool does not correspond to the conditions of its operation, breakage of several adjacent saw teeth or the appearance of cracks in the blade.

Fig. 102. Detection and elimination of defects in the shape of a circular saw blade: a-circuit detection of disk defects by checking from two sides; b-location of impacts when correcting defects; C-weaknesses; T-tight places; B-bulges; I-bends

When cutting teeth, the gap between the punch and the die should not exceed 0.5 mm. The stamped contour of the teeth should include an allowance of 1 -1.5 mm relative to the desired profile. The final shape of the teeth is achieved by sharpening them on the machines.

Editing drank. Editing eliminate local and general defects in the shape of the canvas. The device for editing circular saws is 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 calibration ruler on both sides. Defined boundaries of the defects are outlined with chalk (Fig. 102).

The method of editing depends on the type of defect. Weaknesses “C” are corrected by striking the forging hammer with a round striker around the defect with a gradual weakening as it moves away from it.

Impacts are applied on both sides of the saw (Fig. 102 I). Tight spots “T” are corrected by blows of the forging hammer inside the defect zone, starting from the borders and ending in the middle. Impacts are applied on both sides of the saw (Fig. 102 II).

The bulge “B” is corrected by striking the forging hammer from the bulging side (Fig. 102 III). In order not to change the overall tension of the blade, a cardboard or leather gasket is placed between the saw, which is placed upstream of the bulge and the anvil.

The bend of the “I” saw (folds at the serrated edge, bent sections, humps and one-sided wing-likeness of the disk) is corrected by striking the correct bend of the hammer (with an oblong striker) either along the ridge 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 bulge. The axis of the striker should coincide with the direction of the axis of the bend (Fig. 102III).

It is recommended to check the quality of the saw straightening with a special tool (Fig. 101). In this case, the verification takes place under conditions close to operational. The criterion for assessing the quality of editing is the value 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.

A saw is considered straightened if deviations (in mm) from flatness (warping, bulges, etc.) on each side of the saw blade do not exceed for saws with a diameter (mm) up to 450-0.1; from 450 to 800 - 0.2; from 800 to 1000-0.3. Deviations from the flatness of the central part of the saw in the area of \u200b\u200bthe flanges should not exceed 0.05 mm.

For straightening circular saws, use the saw-saw anvil PI -38, forging hammers PI -40, PI -41; correct hammers PI - 42, PI - 43; device for checking the quality of editing; rulers testing PI - 44, PI - 45, PI - 46, PI - 47 and G1I - 48.

The length of the handles of the right hammers should be 30 cm; the mass of hammers with cross strikers -1 kg, with oblique strikers - 1.5 kg; convex radius is 75 mm.

Sawing is carried out in order to create the initial stresses necessary to compensate for the temperature stresses arising from uneven heating of the saw blade during sawing and to reduce the risk of resonant states of the tool.

The essence of rolling is to weaken the middle part of the saw, due to its elongation when rolling between two working rollers under pressure.

The milled saw acquires lateral stability of the gear during operation, i.e., the ability to withstand unbalanced lateral forces acting on the blade 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 turns of the saw under the influence of the rollers. Average values \u200b\u200bof the roller clamp for new unforged saws when rolling along one circle with a radius of 6 , 8 R should be installed in accordance with the data in table 25.

Table 25. Clamping force of rollers when rolling round flat saws

Depending on the initial stress state of the saw, one hundred pressure rollers may fluctuate.

A correctly milled saw, when placed in a horizontal plane on three evenly spaced bearings located inside the circumference of the tooth cavities at a distance of 3-5 mm from it, with free sagging of the middle part should acquire uniform concavity (tare). The curvature values \u200b\u200bof the milled 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, should correspond to the values \u200b\u200bindicated in table 26.
  If the necessary weakening of the middle part of the saw is not achieved, the saw is turned over and re-rolled with the previous value of the pressure force of the rollers. Turning the saw helps to reduce the bending of the blade somewhat by the rollers. If the middle part of the saw has not received the necessary attenuation, the rolling process is continued along the same circumference with an increased force of pressure of the rollers.

Excessive weakening of the middle part of the saw during its rolling is corrected by rolling along a circle spaced 3 to 5 mm from the circumference of the tooth cavities. In this case, the pressure force of the rrlik is taken from 10 to 30 kg, depending
  from the initial stress state of the tool.


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