Why is there a wave on the band sawmill? Important to know when working with band sawmills! Band saw sharpening

OPERATING INSTRUCTIONS FOR WOOD-MIZER BAND SAWS

The WOOD-MAIZER saw is made of high-carbon steel and heat-treated in such a way as to ensure maximum stability of the saw in the cut, which is why our company recommends the use of the WOOD-MAIZER saw, however, any positive quality cannot but have accompanying side effects. WOODMAIZER saws also have them. They require a more strict attitude from operators and sharpeners.

1 BLADE TOOTH STEP

A blade's tooth pitch is the distance between the tips of two adjacent teeth. For WOOD-MIZER blades it is 22.0 mm. The tooth pitch is constant and does not change during the sharpening process.

2 TOOTH HEIGHT

Tooth height is the distance between the base of the interdental socket and the top of the tooth. Due to the presence of an interdental recess, sawdust is removed from the working area of ​​the blade during sawing. The height of the tooth must be sufficient to ensure the removal of sawdust that accumulates in the interdental recess during the sawing process.

The height of the teeth of the WOOD-MIZER blades is optimal for all types of sawing. When sharpening the blade, the tooth height decreases. To maintain the required tooth height, it is necessary to deepen the groove between the teeth until the tooth height corresponds to 4.8 mm. See Table 1 at the end of this section.

Blades with teeth 4.8 mm high. used for all types of sawing. Blades with teeth 4.0 mm high are used mainly for sawing frozen, hard wood. Blades with teeth 4.3-6.4 mm high can be used for processing very soft woods.

3 SHARPENING ANGLE

The sharpening angle, degree of sharpening and tooth set are the most important factors affecting the performance of the blade. All these factors affect the quality of sawing and the productivity of the sawing machine.

The sharpening angle is the angle of deviation of the tooth end from the vertical. Thanks to the sharpening angle, the tooth “hooks” the wood. The tooth must penetrate deep enough into the wood so that the blade itself can effectively eject the sawdust. If the sharpening angle is too large for a given saw feed speed, this can lead to vibrations and, as a result, deterioration in the quality of the cut. With a small sharpening angle, the tooth will not penetrate the wood to a sufficient depth, which can lead to additional loads during sawing and deterioration in the quality of the cut.

The sharpening angle depends on the type of wood being processed and the productivity of the installation. As a rule, the smaller the sharpening angle, the lower the productivity of the sawing machines. See Table 1 at the end of the section.

4 END ANGLE

The end angle is the angle of deviation of the end of the tooth relative to the blade itself.

When the tooth is not deviated, the end angle is 90 degrees. When setting the blade, the angle of the end changes by several degrees and becomes more than 90 degrees.

5 TEETH SETTING

The setting of the teeth is an important factor affecting the sawing characteristics of the blade.

The setting of the teeth is the linear value of the deviation of the tooth at a given angle relative to the plane of the blade. The greater the tooth set, the wider the cut and the greater the force required when sawing.

See Table 1. Recommended tooth set is typically 0.5 - 0.55 mm for 1.1 mm blades. When working with hard thresholds and frozen wood, the setting value should be in the range of 0.4 - 0.45 mm for 1.1 mm blades. Large setting is used when working with soft wood (0.55 - 0.6 mm for 1.1 mm blades).

Remember that when sharpening the teeth and reducing their height, the setting also decreases and the setting of the blade teeth is required.

The WOOD-MIZER saw is designed initially to be much more rigid than almost all of its main competitors, so it does not lose stability at a lower tension than other saws, and the lower the tension, the less stress that occurs in the blade and, as a result, the less likely it is to break saws.

In order to correctly set the blade tension on the sawmill, do the following:

Remove the guide rollers from the unit.

Position the saw blade correctly on the unit.

Reinstall all guards.

Start the saw.

Then begin to release the tension little by little until the saw begins to vibrate noticeably.

Note the pressure gauge reading at this point.

Stop the machine and put the roller in place;

Add 60 atmospheres to the pressure gauge readings and try to saw, if everything goes well, then you should work at this tension in the future, but if the saw worries, then add 5 atmospheres and try to saw again.

It is necessary to saw at the lowest possible tension (150 - 170 atm.) This will prolong the life of the saw.

In order to obtain lumber High Quality without overpaying for saws, you need to comply with a number of simple requirements:

a) It is necessary to monitor the condition of the belts on the pulleys; two belts cost less than one saw, so you can afford to change them a little more often and save absolutely incomparable money on saws. It is absolutely unacceptable for the saw blade to pass through metal; if this happens, the saw will not last even one hour.

b) It is important to correctly align the saw blade on the pulleys: the distance from the tooth cavity to the edge of the pulley may vary depending on the type of machine.

c) Correctly align the guide rollers:

• The rollers must be aligned horizontally and vertically
• The roller should not push the saw down from its free state by more than the amount specified by the manufacturer depending on the type of machine.
• The rear side of the saw should not be more than the amount specified by the manufacturer depending on the type of machine from the stop protrusion of the roller.

d) When sharpening a saw, the shape of the tooth must be exactly the same as the sample.

e) The layout of the blade must correspond to the work being performed, since the blade,
confidently sawing a log with a diameter of 30 cm, will not cut with the same success
log with a diameter of 60 cm, because the volume of sawdust removed from the cut is approximately twice as large.

f)Choose the right lubricant for your saw. The optimal lubricant is a mixture of 50% diesel fuel and 50% oil for lubrication of chainsaw tires (for sawing at temperatures below -15°C). This mixture should be applied to the saw in a thin layer by spraying. There should not be a lot of lubricant; one spray will be enough for a while. You will easily notice that it is time to lubricate by the return of the sound that disappeared after applying the lubricant. Apply lubricant so that it reaches both sides of the saw. The use of lubricant will also allow you to reduce the number of “blooming” boards caused by sawdust and water getting on them

g) RELEASE THE TENSION ON THE SAW AS SOON AS YOU HAVE STOP SETTING

During the sawing process, the saws WARM UP and, as a result, increase in length. As the saws cool down, they tend to shrink back to their original size and in the process, excess stress arises in the saw. In addition, the saw retains the memory of the shape of the two pulleys, which does not extend the life of the saw.

Besides. the belts on the pulleys are wrinkled, which makes them, firstly, not round and adds additional vibration to the saw, and secondly, it jams the “hump” on the belt, which ensures that the saw itself is centered on the pulleys.

HOW TO KNOW IF YOUR SAW IS CORRECTLY SETTED?

The split can be considered optimal when there is a mixture of 65-70% sawdust and 30-35% air between the saw blade and the tree it is sawing. An external manifestation that the saw is set up correctly is that it throws out approximately 80-85% of the sawdust from the cut.

If the saw's spread is insufficient, tightly compressed hot sawdust remains on the surface of the board; it is impossible to think of anything worse for the saw. The sawdust should be warm, not hot or cold.

A saw that is set too far will likely cut jerkily, and a saw that is not set too far will likely cut jerkily.

If you are sawing logs with a diameter of 30 cm at a good speed and the sawdust is warm to the touch, then you should not try to saw a log with a diameter of 60 cm with a saw with the same spread, because it will have to remove twice as much sawdust from the cut, which means you should increase the spread (approximately by 20%).

Conclusion: Logs should be sorted by thickness before cutting them.

Another very important point: only the upper third of the tooth should be spread, do not spread the tooth under the root; only the sharp corner at the very top of the tooth should be involved in the sawing process.

Don't forget what softer wood, which you saw, the larger the divorce should be.

The saw should be sharpened after freely sagging for 4-5 hours in an inverted state with minimal metal removal (several times if necessary), and then remove the burrs and spread. The basic rule: you get the best cut experimentally, you don’t need to look for formulas in order to calculate.

Do not forget that the indicator on your sharpening device is a thin device. It doesn't cost anything to reset it. It works under extremely intense conditions, judge for yourself: your saw has approximately 220 teeth. You sharpen the saw 15 times, it turns out that the life of the saw is; the indicator is triggered when it is set at least 3.5-4 thousand times (often it is necessary to set the tooth in several steps). This example is given to remind you of that. that the indicator wears out over time and that You should check its installation more often .

It has been repeatedly proven that the quality of the cut largely depends on the shape of the teeth of your saw. The tooth shape was developed and verified
years and it is impractical to conduct these experiments again. Therefore, it is advisable to have a sample (30 centimeters) of the saw and control the shape of the tooth every time you sharpen the saw.

WAYS TO RESOLVE POSSIBLE PROBLEMS WITH SATTING

1. When entering a log, the saw makes an upward leap and when you remove the board, it is curved like a saber. This is most likely caused by the fact that the sharpening angle of the tooth is too large and the spread is insufficient. Try reducing the sharpening angle of the tooth by a couple of degrees and increasing the setting by 2-3 thousandths; to the side.

2. When entering a log, the saw makes a leap upward and cuts exactly almost to the end of the log, after which it falls down. This phenomenon is called “squeezing” or “squeezing”, that is, they say: the saw is squeezing out. This is most likely caused by the tooth sharpening angle being too large. Try reducing the sharpening angle a couple of degrees.

3. The saw “dives” down and cuts smoothly after that. This may be due to several reasons, for example, the fact that the saw is dull, however, most likely, the cause of this phenomenon is the insufficient sharpening angle of the saw, which in turn can be caused by the fact that the sharpener does not refill the stone in a timely manner; inspect the blade carefully if the shape If the tooth seems ideal to you, then you should increase the sharpening angle of the tooth by a couple of degrees.

4. The saw “dives” down and when you remove the board, it is curved like a saber. This is most likely caused by an insufficient sharpening angle and insufficient setting at the same time. Look at the blade carefully, if the shape of the tooth seems ideal to you, then you should increase the sharpening angle by a couple of degrees and increase the spread by 2-3 thousandths per side.

5. The cut goes in a wave. If the saw is sharp, then this is due to too small a gap, you should increase the gap by 0.006-0.008 inches per side according to the indicator.

6. There is too much sawdust left on the board and it feels loose to the touch. This is most likely caused by too much smudge and if you look closely, you will see characteristic scratches across the board, the so-called “tooth marks”. As you probably already guessed, you should slightly reduce the saw spread.

7. Sawdust “rolls” onto the saw blade. This is caused by the fact that the saw is not set apart enough and there is not enough air left in the cut, the saw blade rubs against sawdust, heats up and wood dust gets baked onto the saw. Increase the spread by 0.005 inches per side according to the indicator.

8. Sawdust “rolls” on the top surface of the tooth, but this does not happen on the surface of the saw. This is due to poor sharpening quality (too much feed or too much metal removal and, as a result, poor quality surface on the cavity of the tooth), either due to the sharpening angle of the tooth being too large, or because they continued to saw with the blade after it had already become dull.

9. The sawdust on the board is compressed and hot to the touch. The spread is not sufficient, the spread should be increased by 0.003 inches per side according to the indicator. Reduce the sharpening angle.

DON'T FORGET THAT SAWING WITH A JUST SAW IS THE FASTEST WAY TO TEAR IT

10. The saw becomes cracked at the back. This is caused by the fact that the rear stops of the guide rollers are too far from the back of the blade. The distance from the back side of the blade to the stop of the guide roller should not exceed the value indicated on the back, depending on the type of machine.

11. A new, never sharpened saw cracks along the tooth cavities. This is most often caused by the fact that the blade is not cut enough for the work that they are trying to do with it (see paragraph 4 of the basic rules of sawing), or by the fact that they continued to saw with the blade after it became dull), or could happen after the first cutting if the log was sufficiently “rolled” in sand.

12. After re-sharpening, the blade becomes covered with cracks in the tooth cavities. During re-sharpening, too much metal was removed at one time, resulting in over-correction of the tooth surface. Or this is due to a change in tooth geometry. Compare the tooth geometry to what it was originally by holding a piece of blade to the saw that has never been sharpened.

Blade parameters.

Table 1.

Table 2-1. is not a postulate, i.e. For each type of wood you need to individually select saw parameters. Good sawing largely depends on the selection of these parameters, as well as in what region you are sawing, or where the wood for sawing is brought to you from, since the same species may differ in density and resin content depending on a particular region

Sometimes when sawing, an uneven, wavy surface of the board appears, which naturally reduces the quality of the product.

• correct machine settings
• sawing speed
• saw quality
• wood quality

Setting up the machine.
The machine settings should be checked daily, and always after possible contact of the saw support rollers with the log. The saw guide rollers determine the position of the saw relative to the machine support table. The correctness of their installation is controlled using an adjusting ruler. The rollers themselves should not have signs of wear on the working surface - this leads to vibration of the saw. There should be no deep marks on the sides of the rollers (they are obtained if the rollers do not rotate when the saw moves). The condition of the bearings is also checked. If bearings are being replaced, it is necessary to check the condition of the mounting holes in the roller housing - they should not be broken. In this case, the roller assembly should be replaced.

Next, the fastening of the roller axis (pin) in the housing is checked. If play is detected (all the studs securing the axle are tightened), the housing is replaced. Often during operation the place where the roller body is attached to the carriage guide is damaged, so it is not possible to correctly adjust the position of the rollers (there is no adjustment margin). You can try to straighten the bend by first dismantling the roller body. True, this can damage the welding site, so it is better to replace the defective body with a new one. It is better to immediately replace broken adjusting pins and folded locknuts with new ones.

After replacing defective components and parts, the saw rollers are completely adjusted. To ensure uniform pressure of the rollers on the saw when moving the movable roller from one extreme position to another, the guide of the movable roller must move in a plane parallel to the plane support table. Without such adjustment, when the cutting width changes, the rigidity of the saw blade changes, and this provokes the appearance of a “wave”.

Please note: there should not be even slight play in the movable roller guide drive unit.

Bed rollers.
After adjusting the perpendicularity of the vertical guides to the bed, it is necessary to check the fit of the upper and lower rollers to the corresponding guides. If necessary, the lower pressure rollers (if any) are also adjusted.

Adjusting the position of the saw on the working pulleys.
A large run-off of the saw from the pulleys leads to stretching of the trailing edge, and as a result, the saw becomes unstable in the cut. In this case, the defect does not appear immediately, sometimes after the second or third sharpening

Installation of the machine.
This is especially important in cases where the support legs of the machine are not secured with anchor bolts, as recommended in the machine’s operating instructions. All supporting legs must touch the floor without any gaps. If a gap is detected, it must be eliminated.

Sawing speed.

The cutting speed should be as close as possible to the maximum speed for the type of wood. If the sawing speed is insufficient or, conversely, too high, there is a possibility of getting a “wave”. Saw quality. The cutting speed directly depends on the quality of the saw. Often a “wave” occurs if the saw is dull, or its setting is insufficient - all this reduces the sawing speed. The sharpening angle also has the same effect. If this angle is greater than optimal for a given type of wood, the saw is overloaded (stuck), and if it is insufficient, the sawing speed decreases.

The unevenness of the wiring deserves special consideration. If the setting is different from tooth to tooth, the “wave” will be random in nature, and will depend mainly on the uneven density of the wood. If the routing differs for different sides of the saw blade, the “wave” will depend on the predominance of the routing value (in one direction or the other) and will appear when the sawing speed changes. The presence of such a defect can be assumed if, after entering the wood, the saw dives down or rises up.

A saw whose tooth pitch or tooth height changes from tooth to tooth will cut jerkily and with significant vibration - and as a result, with a "wave". If there are burrs on the saw that have not been removed, this leads to heating of the saw, and therefore to the appearance of a “wave”.

If the saw has been damaged, then, as a rule, even after straightening it cannot provide a quality cut.

Wood quality.

Wood is to blame for the occurrence of waves. Basically, the point here is the uneven density of the various layers of the log, which is due either to the type of wood, the presence of knots, or the degree of frostbite. It is difficult to combat this: it is almost impossible to select the parameters of the saw in such a way that it cuts both the hard outer and soft inner layers equally well at the same time. We recommend changing the cutting pattern or leveling the surface after receiving the timber.

When sawing knotty wood, the risk of a “wave” increases. Care is required here: you will have to smoothly reduce and then just as smoothly increase the feed speed when passing a knot.

If the wood is very resinous, the adhesion of sawdust and resin to the saw blade significantly increases its thickness, the saw heats up and, as a result, the tension drops and a “wave” appears. Cleaning liquid should be used.

Any deviation from the norm leads to a decrease in the quality of sawing and loss of productivity.
If you have a problem with sawing, you should pay attention to the following reasons:
When entering a log, the saw makes a leap upward and cuts straight almost to the end of the log, after which it falls down. This phenomenon is called “squeezing” or “squeezing”, that is, saying: the saw is squeezing out. This is most likely caused by the tooth sharpening angle being too large. Try reducing the sharpening angle a couple of degrees.
When entering a log, the saw jumps upward and when you remove the board, it is curved like a saber. This is most likely caused by the fact that the sharpening angle of the tooth is too large and the spread is insufficient. Try reducing the sharpening angle of the tooth by a couple of degrees and increasing the spread on the side by 0.05-0.1 mm.
The saw "dives" down and when you remove the board, it is curved like a saber. This is most likely caused by an insufficient sharpening angle and insufficient setting at the same time. Look at the blade carefully, if the shape of the tooth seems ideal to you, then you should increase the sharpening angle by a couple of degrees and increase the spread on the side by 0.05-0.1 mm.
The saw “dives” down and cuts smoothly after that. This may be due to several reasons, for example, the fact that the saw is dull, but most likely the cause of this phenomenon is the insufficient sharpening angle of the saw, which in turn can be caused by the fact that the sharpener does not refill the stone in a timely manner. Look at the blade carefully, if the shape of the tooth seems ideal to you, then you should increase the sharpening angle of the tooth by a couple of degrees.
There is too much sawdust left on the board and it feels loose to the touch. This is most likely caused by too much smudge and, if you look closely, you will see characteristic scratches across the board, the so-called “tooth marks”. As you probably already guessed, you should slightly reduce the saw spread.
The sawdust on the board is compressed and hot to the touch. The spread is not sufficient; the spread should be increased by 0.1 mm per side according to the indicator. Reduce the sharpening angle.
The cut goes like a wave. If the saw is sharp, then this is due to too small a gap; the gap should be increased by 0.1 mm per side according to the indicator.
Don't forget that sawing with a straight saw is the most quick way tear it up!
The saw is bursting with cracks at the back. This is caused by the fact that the rear stops of the guide rollers are too close to the back of the blade. The distance from the back of the saw blade to the stop of the guide roller must be at least 1 mm.
A new, never sharpened saw cracks along the tooth sockets. This is most often caused by the blade not being cut enough for the job they are trying to do, or by the blade being continued to be cut after it became dull, or could happen after the first cut if the log was sufficiently “rolled” in sand.
Sawdust rolls onto the saw blade. This is caused by the fact that the saw is not set apart enough and there is not enough air left in the cut, the saw blade rubs against the sawdust, heats up and wood dust gets baked onto the saw. Increase the spread by 0.1 mm per side according to the indicator.
The sawdust "rolls" on the inner surface of the tooth, but this does not happen on the surface of the saw. This is due to poor sharpening quality (too much feed or too much metal removal and, as a result, poor surface quality in the tooth cavity), or too high a sharpening angle of the tooth, or the fact that the blade continued to be sawed after it had already become dull.
After regrinding, the blade becomes covered with cracks in the tooth cavities. During regrinding, too much metal was removed at one time, resulting in over-grinding of the tooth surface. Or this is due to a change in tooth geometry. Compare the tooth geometry to what it was originally by holding a piece of blade to the saw that has never been sharpened.
It is necessary to constantly monitor the condition of the sharpening stone. Profile it in a timely manner.
All of the above reasons and cases can occur provided that the band saw machine is in stable operation!
Good luck with your sawmilling!

When processing wood on a band sawmill, probably everyone has encountered problems such as “waves”, constantly breaking saws, and so on. But not everyone wondered about the true causes of these problems; it is much easier to blame everything on low-quality or defective band saws. But this does not solve the problem and you will constantly find yourself in search of some ideal brands of saws. From this article you will learn that the cutting quality and durability of band saws largely depends on their care, proper maintenance and proper handling of the tool.

Selection and maintenance of band saws

General rules:

You only make money when sawdust is flying out from under the saw!

There are no trifles in sawing with narrow saws; any deviation from the ideal leads to sad consequences!

Most the right way If you ruin your saw, it’s not enough to loosen it!

There is no point in expecting outstanding results from saws when the machine is not working properly!

Make sure there is light in the sharpening area, this will save you from a lot of trouble!

It is the individual fit that allows you to achieve outstanding results from an unprepossessing-looking sharpening machine.

Pay close attention to the shape of the grinding wheel.

Types of band saws.

In small sawmills, regardless of the number of heads, blades with a width of 25, 32, 38 and 50 mm are mainly used. Basically, there are two main thicknesses of canvas on the market - 0.035” (0.9 mm) and 0.042” (1.1 mm). Naturally, there are blades of other standard sizes, but they are mainly used in specific cases. Carbon steel blades are most widespread in sawmilling. These fabrics are distinguished by the type of heat treatment to which they have been subjected:

Constant hardness (Constant hardness) blade with equal hardness across the entire width of the blade. The carbon content in such a material is not high, and this does not allow it to be hardened to a hardness of more than 45-48 units on the HRc scale. This blade works well on small diameter pulleys. However, it has to be sharpened quite often.

Flex back - Hard Edge (Hard edges) – a blade with a flexible body/hard tooth. This canvas is called both. In the production of this blade, a tape with a high content is used, which allows its teeth to be hardened to HRc 63-65. Usually only the upper half of the tooth is hardened, which leaves the saw body practically unhardened and quite flexible. Saw body hardness – HRc 30-33. The advantage of this type of saw is that it holds an edge better while remaining quite flexible. Sometimes manufacturers heat a narrow strip on the very back of the saw, this allows the blade to be straight. Do not confuse such canvases with Hard Back type canvases.

Double Hard – (Twice Hard ) blade hardened over the entire width. This is the most technologically advanced and difficult to produce type of tape. Its tooth has a hardness of HRc 63-68, and its body HRc 48-53, and the saw body is hardened in a stretched state. High tooth hardness provides good resistance to dulling (the blade lasts longer between sharpenings), and the increased rigidity of the blade body allows sawing at high feed rates. These saws cut smoothly and straight at those feeds at which any other blade would have produced a “wave” long ago.

There are also saws with various types of soldering and surfacing, as well as so-called bimetallic saws. All of these types of saws combine flexibility with tooth resistance, but they are high price puts them in the category of exotic products, and we will not waste time describing them.

How to choose the right band saw

Before we move on to considering this problem, let’s take it as an axiom that there are no eternal band saws; sooner or later they all break from fatigue and overexertion. This means that if you put a new blade on your sawmill and just turn it on, it will tear, even if you don't cut with it at all. The lifetime of the canvas in this case is determined by its rigidity. Hard fabric will tear faster. However, on the other hand, the stiffer and harder the blade, the longer it remains sharp. On the contrary, a soft blade will not tear for a long time from fatigue, but it is completely impossible to saw with it due to its permanent dullness. The golden mean is, as usual, somewhere between these extremes and is individual for each specific case.

Let's consider the behavior options of all three types of canvas:

Constant hardness – a blade with equal hardness across its entire width. The blade will not tear for a long time as a result of a lack of flexibility - it is not lacking in flexibility, but it quickly becomes dull, as a result of which it can be recommended for use on low-power manual sawmills with small diameter pulleys. In such sawmills, the saw mostly spins idle on pulleys while workers edge or secure the log. The undoubted advantages of this blade include the fact that it can be sharpened many times without compromising tooth durability, which, unfortunately, is not high.

An excellent replacement for canvas with equal hardness over the entire width, a blade with a flexible body/hard tooth, the so-calledFlex back. This blade has excellent flexibility and holds an edge well, so in addition to being used on low-power manual sawmills, it can be used on cutting saws, regardless of the number of heads. The disadvantage of this type of blade is the fact that it can be re-sharpened until you grind down the hardened area on the tooth. After this, you just have to throw the canvas away.

And finally, saws like Double Hard – canvas hardened over the entire width. Technological tricks in the production of this fabric are not in vain. These blades not only hold an edge perfectly, but also, as a result of their high rigidity, allow sawing at significantly higher feed rates. This allows them to be used in much more power-equipped sawmills, achieving significantly higher productivity. You can resharpen such a saw as long as its width allows. Even after the particularly hard tip of the tooth is ground off, the saw will hold its edge perfectly.

Factors affecting the durability of the saw include:

Type of material being cut. The harder and more resinous the material, the sooner the saw will break.

The speed at which the saw enters the workpiece. The sharper the saw enters the workpiece and the more often it does this, the worse it is for the saw. This is especially true for second-row installations, where the workpieces can be quite short and the method of feeding the workpiece into the machine (end to end or at intervals) can have a decisive impact on the performance of the saw.

Idle rotation of the saw. The most important factor influencing its vitality. This is especially true for first-line sawmills working with logs. In these sawmills the operator actually saws 50 percent of the time at best. The rest of the time he works with the log, that is, he turns it over, clamps it, unclenches it, and so on. If you stop it while the saw is not directly sawing the tree, this will significantly prolong its life. (Ed.: In no case should you follow this recommendation literally, stopping the engine after each pass of the saw - the harm from this will be much more than good! When starting the engine, the saw is subjected to large overloads, and this is not good for the starting equipment. Stop engine only during breaks in work for loading logs, turning, etc.)

Leaving the saw in tension after a change. If this occurs, immediately remove the saw, turn it inside out, and hang it up to rest. Otherwise, you will throw it away on the same day with a very high degree probabilities. This is not to mention the fact that leaving the saw in a tense state overnight you statically deform the bandage belts, they lose their shape and begin to “beat”, which also does not prolong the life of the saw.

Finally, improper sharpening. The next section will be devoted to sharpening as such, selecting the tooth shape and saw alignment for each specific type of wood and external conditions.

Band saw resharpening

Let me start with the fact that resharpening band saws is more of an economic problem than a technical one.

There are three approaches to solve this problem:

The first approach is this: You cut with the saw until it cuts, and then just throw it away. Some manufacturers of band saws, for example Morse in the USA, produce a disposable saw that is practically unsuitable for resharpening. It's a blade of cheap steel that gets thrown away after it gets dull the first time.

The second approach can be formulated this way: You cut with a saw until the saw “waves”, after which you remove it and resharpen it.

The third approach can be boiled down to the following: You remove the still almost completely sharp saw from the machine and only slightly adjust it.

Let's look at the advantages and disadvantages of all three approaches:

The first approach reduces the sawmill's time wasted on blade replacement, and also eliminates the need for a sharpener and sharpening area, which represents real savings. If we add to this that such a saw costs about half as much as a saw hardened over the entire width, then the savings become obvious. In Russia, however, for some reason such saws cost the same as their technologically advanced counterparts, and the savings from using this method seem unlikely to me. The sawing length of such a saw before breaking can be 10-12 cubic meters (On second-row installations). On first-line installations, it may not last even an hour.

The second approach also reduces sawmill downtime associated with saw replacement. Saw sharpening occurs less frequently, which saves the sharpener’s time, which costs quite a bit of money. However, this approach leads to excessive fatigue of the saw and greater removal of saw material during resharpening. As a result, the sharpening stone loses its geometry, which inevitably leads to a loss of saw tooth geometry, and, as a consequence, to rapid failure of the saw. The saw cut before the saw breaks with this approach is usually 20-25 cubic meters.

The third approach comes down to the fact that the saw is removed from the sawmill every hour and after a rest it is slightly adjusted, after which it goes back to work. The disadvantages of this method include frequent stops of the sawmill to change the saw, but this rarely takes more than one minute. The small amount of metal removed during sharpening ensures that the tooth shape remains almost ideal, which in turn leads to increased productivity. With this approach, it is possible to resharpen the saw up to fifty times, and the cutting capacity reaches 80 cubic meters.

Objectively assess the cost of sawmill downtime per minute, this will allow you to objectively assess which of the methods described above for working with the blade to follow, and will also help when communicating with staff. When regrinding, pay attention to the following:

Firstly, it is extremely important to maintain the shape of the stone unchanged. How to achieve this: Take a harder stone (remember that tooth hardness can be up to HRc 68). It is better to use imported one. Give the stone the correct shape, based on the manufacturer’s recommendations and your own experience. Sharpen the tooth not only along the front and back surfaces, but also along the entire cavity. Shoot as much as possible less metal, it is better to go through the saw several times. Touch up the stone after each full round of sharpening. And one more practical advice: make sure there is light in the sharpening area, this will save you from a lot of trouble.

Secondly, the saw body is dirty (rusty). The longitudinal feed drive on most band saw sharpening machines is low-power and even minor changes in the quality of the blade surface can lead to underfeed (remember that we are talking about hundredths of a millimeter). The way to combat this cause is very simple: After removing the saw from the sawmill, the operator wipes it with a rag soaked in a mixture of diesel fuel and machine oil, removing sawdust that has rolled onto it and protecting the saw from corrosion.

Thirdly, a faulty bipod-pusher. Most sharpening machines move the saw by pushing the tooth with a special bipod. The uniformity of the feed and, as a consequence, the constancy of the saw pitch largely depends on the condition of this bipod and its drive. The worst thing is if the bipod dangles from side to side. This can lead to the fact that it pushes some teeth with a more worked part, and others with a less worked part, which leads to a change in the pitch of the saw. This defect can be easily eliminated using an ordinary rubber band. Lightly pull the bipod to something with an elastic band - and all the play is eliminated. Now the bipod pushes the canvas in the same place. Do not try to combat backlash by adjusting parts of the cam mechanism, this is a waste of time. The bipod itself must be made of hardened steel, or have a hardened insert with which it must push the saw. The radius of the pusher should not exceed one millimeter. Monitor its condition, if necessary, correct the shape of the pusher, or change the insert. By the way, the bipod should push exactly the tooth that will be sharpened, and in no case the previous one.

Fourthly, the clamping force of the saw blade in the machine. I cannot say that the blade should be clamped with a force of so many newtons. There are machines in which the saw is clamped by a spring, on other machines this role is played by permanent magnets, on others the sharpener clamps the saw with a screw, determining the clamping force of the saw by the load of the feed servomotor. Each of these methods has its pros and cons, but they all allow you to achieve excellent results if used correctly. General rule is this: the feed servomotor must push the web through the clamp with some force. Unfortunately, as I said above, I cannot give figures in newtons. I will only say that the feed motor should not stop due to excessive load, but it should not rotate idle either - you can hear it very well, just practice. Let me explain why weak clamping of the blade is dangerous. If the blade is clamped weakly, it can “play” back after the bipod moves away and the tooth will simply be ruined.

Sharpening angle. It has a significant impact on both cut quality and productivity. The sharpening angle depends on the type of wood being processed and its condition. The general rule is: the harder the wood, the smaller the angle, but even when sawing the softest types of wood, you should not make an angle greater than 15 degrees. This will lead to an increase in pressure at the base of the tooth, overheating of the blade at the base of the tooth, and as a result, sawdust rolling onto the blade, which is actually equivalent to reducing the streak. A larger amount of sawdust will be sprinkled into the cut, instead of being removed from it, which in turn will also lead to overheating of the saw and its premature fatigue and, as a result, to the appearance of cracks. On the other hand, even when sawing frozen oak, you should not make the sharpening angle less than 4 degrees. This will lead to excessive tensile stresses along the saw body, spillage of sawdust into the cut, overheating of the saw and the appearance of cracks. However, if in the first case the cracks will most likely be at the base of the tooth, then in the second - right in the middle of the cavity.

Tooth height. It also has a significant impact on the productivity and quality of the cut. The size of the tooth depends on the type of wood being processed and its condition. The general rule is: the harder the wood, the smaller the tooth. Further in the table you will find recommendations for tooth height when sawing different breeds wood

Divorce - The most important parameter band saw. The split can be considered ideal when a mixture of 70% sawdust and 30% air remains between the saw blade and the tree it is sawing. That is, the saw should remove 80-85 percent of the sawdust generated by it from the cut. If the saw is set too far apart, characteristic marks of the saw teeth remain on the surface of the board - lines across the entire board. If the saw is not widened enough, tightly compressed hot sawdust remains on the surface of the board. At the same time, the saw will strive to “give a wave.” There's nothing worse for a saw than an insufficient divorce.

The saw parameters indicated in this table are not the ultimate truth. These are just guidelines from which you should build. Select saw parameters that are optimal for your type of wood. Do not forget that even trees of the same species grown in the same region can differ significantly from each other in density and resin content, and, therefore, will require an individual approach to the selection of modes and saws with which you will cut.

Specialists who professionally cut wood know how to deal with many pitfalls that may arise during the work process. One of the serious problems that occurs when cutting wood is the presence of an uneven surface on the cutting line after finishing the work, the appearance of a so-called “wave”. Professionals know that this is a fairly common occurrence and know how to avoid it. They believe that the sawing process is influenced by four main factors:

1. Operator skill
2. Machine operation
3. Saw quality
4. Sawing material

It is clear that the human factor is often the main one. Therefore, if a band sawmill is serviced by a highly qualified specialist, it may happen that the other three factors simply disappear by themselves.

Operator- this is the person who makes all the necessary settings for the operation of the machine: selection correct speed sawing, choosing the right saw, depending on the type and characteristics of the lumber.

Optimal sawing speed- the most important point: if the speed is insufficient, the cut area will look like a washboard, and if the speed is too high, the notorious “wave” will appear due to poor quality of the cut.

Correct machine setup- here is another important point. For optimal performance the machine must be set up correctly. It is recommended to set up the machine taking into account the duration of work on it. It has been experimentally established that, on average, the adjustment of a band sawmill should be done once every four 8-hour shifts, but in general a lot depends on the machine itself. For example, all line of sawmills "CEDAR" may not require adjustment for up to 14 days with daily intensive use. However, to prevent the appearance of “waves”, we recommend checking the machine settings daily. If no deviations from the norms are found, the geometry and alignment of the saw pulleys are preserved, then you don’t have to do any adjustments. Examination Necessarily must be performed if there was contact between the log and the support rollers.

Machine operation

Machine is a simple set of parts and assemblies. However, some of them can provoke the appearance of a “wave”.

• Saw guide rollers. The position of the saw in relation to the support table depends on them. The main tool for monitoring correct installation is a special adjustment ruler. You must avoid damaging it in every possible way and do not try to make it yourself if it is damaged. A visual inspection of the rollers should show the absence of potholes on the working surface. It leads to vibration. Deep potholes indicate that the rollers were stationary when the saw moved. Checking the bearings in the roller should show that they have no play or very little play. Otherwise, the roller assembly must be replaced, since if the mounting holes have changed sizes and the play cannot be eliminated. The next point is to check the fastening of the roller axis in the housing. If, with all the studs tightened, there is play, the body must be replaced. It happens that the housing itself at the attachment point is damaged. Repair is difficult and can lead to other problems, such as damage to the weld, so replacement is the best option.

• Machine installation. The machine must have maximum support. There should be no gap between the supporting legs and the surface. Ideally, this is when the support legs are secured with anchor bolts.

Saw quality

After all the settings have been checked, you need to pay attention to one of the most vulnerable points of the sawmill - the band saw. She may just be the culprit of the notorious “wave”. There is only one recommendation here: follow the appropriate instructions when sharpening and setting the teeth of a band saw. All teeth must be sharpened at exactly the same angle. A large angle for one type of wood leads to the fact that the saw begins to get stuck in the material and the load on the saw increases sharply, but if the angle is small, the sawing speed decreases. Conclusion: the main reason for the appearance of “waves” is the lack of proper sharpening or working with a dull saw.

The saw must also be positioned correctly. If the wiring is small, it begins to heat up, even if it is well sharpened. Heating weakens the tension of the saw and it has to be constantly adjusted. The sawing speed drops sharply.

By her own, wiring can tell a lot about the appearance of a “wave”. If it is not the same across the teeth, then the “wave” will not have a systematic character. It will appear in places where the density of the tree is uneven. If different sides of the saw have different layouts, then the appearance of the “wave” will depend on which direction is predominant, and its appearance will coincide with the change in sawing speed. By the way, if after entering a tree the saw begins to rise up or, conversely, dive down, then this may indicate incorrect wiring.
It is quite clear that unevenness in the pitch of the teeth, as well as in their height, when moving from one to another, will cause vibration. The risk of saw rupture is high if burrs are not removed. They also lead to significant overheating of the metal and, as a result, the appearance of a “wave”. We must remember that it is difficult to achieve a high-quality cut from a damaged saw, even if it is corrected.

Features of wood

The “wave” formed during sawing also relates to the wood itself that is being sawed. It is known that wood is a heterogeneous material. The density of its outer layer is much higher than the middle and center. It is clear that the amount of sawdust increases when processing the core. When sawing such areas, the saw may not cope with the full removal of sawdust outside the cutting area. The result is known - heating of its rear part, leading, in accordance with the law of physics, to the expansion of the metal. Expansion helps to relax the tension, and the relaxation of tension causes a “wave”.

To prevent the saw from heating up, the design of the KEDR sawmills includes a special tank for coolant, which is supplied to the saw using special tubes. Before starting sawing, you just need to open the special valve. Plain water is used as a coolant in summer, and soap solution is used in winter.

Today, it is virtually impossible to select a saw that will cut both hard and soft layers equally. But you can change the cutting pattern itself, and also, after receiving the timber, carefully level the surface.

Frozen wood is another factor in producing a “wave”. All operators know this. Moreover, in the case of a completely frozen tree, cutting proceeds without problems. But partially frozen logs create quite serious difficulties when working with them. That is, the situation completely repeats the situation with wood with uneven density, so the sawing technique is similar here.

Particular attention should be paid to working with highly knotty wood. A large number of knots increases the likelihood of a “wave” occurring many times over. Such wood must be sawed very carefully, the cutting intensity must be changed very smoothly, varying it as each knot passes.

Logs with big amount resin. As you know, the resin is very viscous. It promotes the adhesion of sawdust to the saw blade. Sawdust, and even the resin itself, which stick to the canvas, naturally increase its thickness. Accordingly, heating begins and all the ensuing consequences that we have already seen in previous cases - the saw tension drops, a “wave” appears. The way out of this situation is to use coolant, which also serves as a good lubricant that prevents sticking of the material being cut.