Why does the band saw fly off?

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Why the band saw blows off

There are no secondary factors in sawing with band saws.

Any deviation from the norm leads to a decrease in cutting quality and loss of productivity.

If there is a problem with sawing you should pay attention to the following causes:

  • The saw jumps up when it enters the log and cuts straight up to the end of the log, then comes down. This is called “pushing back” or “squeezing”, in other words: The saw is being pushed back. This is most likely caused by too high an angle of sharpening of the tooth. Try reducing the angle of sharpening by a couple of degrees.
  • The saw jumps up as it enters the log and when you remove the board, it curves like a saber. This is most likely caused by the fact that the sharpening angle of the tooth is too large and the pitch is insufficient. Try reducing the angle of the sharpening of the tooth by a couple of degrees and increase the pitch per side by 0.05-0.1mm.
  • The saw “dives” down and when you remove the board, it curves like a saber. It is most likely caused by an insufficient sharpening angle and not enough degree at the same time. Look at the blade carefully, if the shape of the tooth seems to you ideal, you should increase the sharpening angle by a couple of degrees and increase the pitch per side by 0.05-0.1mm.
  • The saw “dives” down and cuts straight after that. This may be due to a number of reasons, such as the saw becoming dull, but it is more likely that this phenomenon is caused by insufficient sharpening angle of the saw, which may in turn be caused by the sharpener not tucking the stone in on time. Look at the blade carefully, if the tooth shape seems perfect to you, then you should increase the tooth sharpening angle by a couple of degrees.
  • Too much sawdust is left on the board and the sawdust is loose to the touch. This is most likely caused by too much rip and if you look carefully you can see some distinctive scratches across the board, the so called “tooth marks”. As you have probably already guessed, the saw’s pitch has to be slightly reduced.
  • The sawdust on the board is compressed and hot to the touch. The pitch is insufficient, you should increase the pitch by 0.1mm per side on the indicator. Reduce the angle of sharpening.
  • The kerf goes in waves. If the saw is sharp, it is because the pitch is too small, increase the pitch by 0,1 mm per side according to the indicator.

Important to know when working with band saws!

Any deviation from the norm leads to a decrease in sawing quality and loss of productivity. If there is a problem with sawing, look for the following: When entering the log, the saw jumps up and cuts straight through to the end of the log, after which it drops back down. This phenomenon is called “squeezing” or “pushing back,” that is to say: the saw is pushed back. This is most probably caused by too steep an angle of sharpening of the tooth. Try reducing the sharpening angle by a couple of degrees. The saw makes an upward leap when it enters the log and when you remove the board, it curves like a saber. This is most likely caused by the tooth sharpening angle being too large and the pitch being insufficient. Try reducing the tooth angle by a couple of degrees and increasing the pitch to the 0.05-0.1mm side. The saw “dives” down and when you remove the board, it is as crooked as a saber. This is most likely caused by inadequate sharpening angle and inadequate setting at the same time. Look at the blade carefully, if the shape of the tooth seems perfect to you, you should increase the sharpening angle by a couple of degrees and increase the pitch per side by 0.05-0.1mm. The saw dives down and cuts straight after that. There could be several reasons for this, e.g. the saw is blunt, but it is most likely caused by insufficient sharpening angle, which in turn could be caused by the sharpener not setting the stone in time. Look at the blade carefully, if the tooth shape seems perfect to you, you should increase the angle of the sharpening of the tooth by a couple of degrees. Too much sawdust is left on the board and the sawdust is loose to the touch. This is most likely caused by too much camber, and if you look closely, you will see characteristic scratches across the blade of the board, the so-called “tooth marks”. As you might have guessed already, the adjusting angle of the saw has to be slightly reduced. The sawdust on the board is pressed and hot to the touch. The arbor is too fine, increase the arbor by 0.1mm per side on indicator. Reduce the sharpening angle. The kerf goes in waves. If the saw is sharp, it is too small, you should increase the pitch by 0,1 mm per side according to the indicator. Do not forget that sawing with an unset saw. That’s the fastest way to break it! The saw is torn by cracks in the back. This is because 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 guide pulley stop should be at least 1mm. A new saw that has never been resharpened cracks in the tooth flanks. It is most often caused by the fact that the blade is not sufficiently set for the job they are trying to do, or by the fact that the blade kept sawing after it became blunt, or it could happen after the first cut if the log was sufficiently “rolled” in the sand. Sawdust is rolled on the saw blade. This is caused by the saw not being sufficiently diluted and not enough air remaining in the kerf, the saw blade rubs against the sawdust, heats up and the wood dust bakes up on the saw. Increase the pitch to zero.1 mm per side according to indicator. Sawdust is “rolling” on the inside surface of the tooth, but not on the surface of the saw. This is caused by poor grinding (too much feed or too much metal removal and the resulting poor surface quality at the tooth hollow), or by the tooth being ground too far back, or by the blade continuing to saw after it has dulled. After resharpening the blade becomes cracked in the tooth flanks. During resharpening, too much metal was removed at one time, resulting in a recalculation of the tooth surface. Or it is due to a change in tooth geometry. Compare the geometry of the tooth with that of your original saw by placing a piece of blade that has never been resharpened. The condition of the sharpening stone must be checked constantly. Profil it in good time. All of the above causes and cases can occur if the band saw is in stable operation! We wish you good luck in sawing!

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Stages of the band preparation

Setting up a band saw is conventionally divided into several stages:

The person responsible for the cutting quality (operator or maybe a technologist in a large factory) must choose the right band saw and set the sawing speed. Depending on the type of material the following settings are selected:

  • Experienced setters know that the sawing speed should be a little less than the limit. The quality of the material on the output depends on the speed: too high will lead to a “wavy” surface, and if low. will appear protrusions;
  • The next parameter must be the tensioning pressure of the belt. It should be seen in the machine’s datasheet. On the average, the machine is set pressure of 170 bar, if there is no sensor of the belt tension force, it should be installed, so you significantly save on quality and consumption of ribbons;
  • The tape protrusion over the pulley is from 0 to 3 mm;
  • Let’s not forget about the parallel alignment of the pulleys;
  • The rollers should be lowered a centimeter below the pulleys and give the ribbon parallelism.

Adjust Bandsaw | Drift, Resaw, Blade Guides, Tension, Sharpening

This adjustment must be done once a day. If the band saw blade tuning is made less frequently, for example every 7 days, the time for tuning itself will increase, and the quality of the material will decrease. After the wood has come into contact with the support roller, it is better to recheck the adjustment of the machine.

Metal band saw malfunctions

Bandsaw malfunctions, types and causes. This is what this article is about.

Wiping the teeth (Fig. 1, α). this band saw malfunction can be caused by too small tooth pitch, excessive feed (feed force), hard inclusions in the material of the workpiece. This can also be caused by incorrectly running the blade, a broken chip brush or a breakage during transport or installation of the blade.

Wear on the flank of the blade teeth (fig. 1, б). Another malfunction on the metal band saw, which is the result of too high cutting speed, or working with too hard or abrasive material. Also, there could be a rear guide that is allowing the teeth to rub against the guide, or the sides of the teeth are just rubbing against the kerf or the teeth are touching a part of the machine.

Wear on the upper part of the blade (fig. 1, в). This problem with band saws can be caused by the blade not sitting correctly and rubbing against the flange of the wheel or by problems with the guide rails:

  • The machine guides are too compressed;
  • Rear guide rail is worn or broken;
  • The guides of the band saw are unadjusted;
  • Guides stand too far apart from each other;
  • Chips penetrating into the guides and scoring the top of the blade.

Cracks from the inter-tooth groove (Fig. 1, г). Another frequent problem is caused by problems with the band saw guides:

Chipped and broken teeth (Fig. 2, α) can be caused by improper running-in of the blade; damage caused by installation, transport etc. п.Hard inclusions in the workpiece material. In addition to these, it can be a simple case of loose workpiece, too much feed pressure or overfeed.

Heavy wear on tooth tips (Fig. 2, б). such malfunctions in the band saws can be due to problems with the coolant:

In addition to the causes mentioned above, wear on the tooth tips can indicate too small a tooth pitch; too high a cutting speed; too low a feed; improper lapping procedure; the tooth is rubbing instead of cutting.

If the space between the teeth is clogged with chips (Fig. 2, c), this could indicate insufficient inter-tooth capacity, too small a tooth pitch, too much feed, a broken chip brush, or a coolant problem:

A curved cut (Fig. 2, d) as a next band saw fault could be caused by too low blade tension, high feed, low tooth pitch, broken teeth, worn blade. Also the curved cut of the band saw can be affected by problems with the guides, which are spaced far apart, worn, poorly adjusted, or the guide arms are loose.

If fatigue cracks appear on the belt blade (Fig. 3, α) it could be that the diameter of the wheels is too small, they are out of adjustment, the tooth pitch is too small, the feed rate is too high or the tension of the blade is too high.

Also causes may be problems with the guides, which:

If another problem with the band saw blade is that metal chips are welded to the top of the tooth (fig. 3, b), it can indicate:

This problem with band saws can also be due to a lack of coolant, an incorrect type of cutting fluid, coolant levels that are too low, or the cutting fluid does not enter the metal cutting zone

If the band saw blade tears. Check belts and rollers

First, check the condition of the saw rollers and pulley belts. The surface of the rollers in contact with the saw must not show any signs of wear and there must not be any deep scratches on the rim of the roller. The danger on the surface of the rollers is that the machine will vibrate, resulting in periodic changes in the tension of the saw, and as a result the band saw will tear. The change in tension can occur at high frequencies.

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It is inadmissible to have tears, frayed surface and excessive contamination with sawdust on the belts. If the distance between the saw and the pulley is less than 0,8 mm when the saw is tensioned to working pressure, the pulley belt should be replaced. Usually both belts have to be replaced at the same time. The reason is that worn belts cause the saw blade to come into contact with the pulley surfaces and the life of the saw is shortened.

Cause 7. Aggressive saw feed.

If all of the above on your machine is okay, pay attention to the sawing technique. Operators may be cutting too fast in an effort to overshoot. This almost always results in an overloading of the saw and a reduction in product quality.

Aggressive saw feed causes overloading of blade and causes it to “wobble” in the kerf. In this case there are obvious signs of contact with the trailing edge of the saw on the flanges of the saw’s guide rollers.

If after the entrance of the saw into the wood the saw “dives” and results in a wavy board surface, with the article “What to do if there is a “wave” when sawing on the band saw”.

The saw is also overloaded if its parameters. tooth profile and pitch. are too high. do not match the type of wood.

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Permissible saw tension

Another reason for band breakage could be that the saw blade is too taut on the sawmill. In addition a wrong calculation of the saw’s load during its operation.

Above all, the tensioning of the band saw must be done according to the instructions that come with the machine. While, experienced sawyers determine the tension of the band saw by pressing the tensioned band from above by hand. The saw may have a slight sag, but does not move away from the guide rollers.

The load on the saw is also listed in the manual, but again, let’s turn to experience. During the sawing process a properly sharpened band should run relatively smoothly and gently. At the exit of the log, it has a slight temperature of heat. But improperly sharpened tape, or blunted during work, goes rather hard and at the output has a rather high temperature of heating.

From such a cause of tape break can only help its timely replacement. How to sharpen and deburr the saw blade correctly. How to sharpen and deburr, is described in our previous articles. Sharpening band saws.

And lastly, it is simply the fatigue of the metal itself. When using the same band for a long time, the metal gets tired and cracks on the stretching, which causes the band to tear. That’s why it is recommended to give the saw a rest for 24 hours after the two-hour’s work. Also, after removing it from the machine, turn it inside out.

Working at low temperatures on the sawmill.

Above all, at.it is not desirable to make all works connected with sawmill, and with woodworking in general, at 30 degrees. over, at this temperature, the wood hardens, making it brittle and quite brittle. As a result, all our efforts will lead to zero results, or even to the damage of raw materials.

For this reason, the most important question arises “so what to do?”. The answer is simple, sit and warm up by the stove and wait for the temperature to reach a warmer. It is not worth risking your property and people, and there will be an opportunity to catch up in the future. Eventually, the low temperatures will sooner or later run out, which gives this opportunity.

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over, let’s remind, that according to the instructions for band saws it is clearly said “that the work on the band saw is from 30 degrees up to.10 degrees”.

Of course, we should not wait for the arrival of the spring heat because of the frost. In this case, experienced sawmill workers tell Us. That such work, on sawing on the band sawmill, can also be done at lower temperatures.

So sawmill workers recommend sawing to.25 degrees. If the temperature is below twenty five degrees, it is simply impossible to maintain the quality of the material. And that is why the best option would be, the production of sawing to.20 degrees. As the experts note that after.20 degrees with each decrease of at least one degree, the work of the sawmill itself becomes harder. And accordingly the quality of the material produced is lost.

Also at the beginning of the temperature drop there is a problem on the setting of the sawmill, which we have briefly discussed earlier, just go to the link https://moyapodsobka.ru/.

But again we note, such settings are effective in the case when frosty weather has set in and the forest is completely frozen. And if not, you have to adjust depending on the freezing of the forest. In a particular case, it depends on how frozen the log is.

Bandsaw selection and maintenance

You earn money only when sawdust flies from under the saw!

There is no place for trifles in sawing with the narrow saws and any deviation from the ideal will have tragic consequences!

The surest way to kill the saw is not to set it up enough!

There is no point in expecting outstanding results from saws if the machine is out of order!

Make sure the sharpening area is bright, this will save you a lot of trouble!

A customized fitting is what enables an unsightly-looking sharpening machine to produce outstanding results.

Watch the shape of the sharpening wheel carefully.

In small sawmills, regardless of the number of heads, blades in widths of 25, 32, 38 and 50 mm are mostly used. Basically, there are two basic thicknesses of blades available on the market. 0.035″ (0.9 mm) and 0.042″ (1.1 mm). Naturally there are also other band saw blades, but they are mostly used in special cases The most common band saw blades are made of carbon steel. These blades are distinguished by the type of heat treatment they have undergone:

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Constant hardness (Constant Hardness) is the same hardness across the entire width of the laminate flooring. There is not much carbon in such blade and it doesn’t let you harden it to more than 45-48 HRc. It works well on small diameter pulleys. However, it needs to be resharpened quite often.

Flex back. Hard Edge. a blade with a flexible body/hard tooth. These blades are called both. In the manufacture of this type of saw blade a band with a higher hardness of the tooth up to HRc 63-65 is used. Only the upper half of the tooth is usually hardened, which leaves the body of the saw almost unhardened and sufficiently flexible. The hardness of the body of the saw is HRc 30-33. The advantage of this type of band saw is that it keeps sharpening better and is very flexible. Sometimes manufacturers harden the narrow band on the back of the saw itself to achieve a straight blade. Not to be confused with Hard Back blades.

Double Hard. (Double Hard) blade, hardened across the entire width. It is the most technologically advanced and hardest to produce type of band saw blade. Its tooth has hardness HRc 63-68 and body HRc 48-53, where the body is subject to tensile hardening. High hardness of tooth gives good resistance to blunting (blade stays between overcutting longer), and increased rigidity of blade body allows to saw at high feeds. These saws cut evenly and directly at feeds where any other blade would have produced a “wave” a long time ago.

There are also saws with different kinds of dressings and coatings, as well as so-called bimetal saws. All these types of saws combine flexibility with durability of tooth, but their high price puts them in the category of exotic products, and we won’t waste our time to describe them.

How to choose a band saw

Before we get into the problem, it is axiomatic that bandsaws are never immortal, they all break sooner or later due to fatigue and overloading. This means that if you put a new blade on your sawmill and just turn it on, it will break even if you do not saw with it at all. The life time of a blade in this case is determined by its hardness. A stiff blade will tear quicker. But, on the other hand, the stiffer and harder the blade, the longer it will stay sharp. A soft blade, on the other hand, will not tear from fatigue for long, but it is completely impossible to saw with it because of its permanent bluntness. The golden mean is, as usual, somewhere in between these extremes and is specific to each case.

Consider the behavior of all three types of blade:

Constant hardness. a blade with equal hardness across the whole width. The blade will not tear for a long time due to lack of flexibility. It is not very flexible, but it blunts quickly, which is why it is recommended for low-power manual sawmills with small pulley diameters. On these sawmills, the saw is mostly idling on the pulleys while workers are tilting or securing the log. The advantage of this blade is that it can be reworked many times without compromising the durability of the tooth, which is unfortunately not very high.

An excellent substitute for a blade with equal hardness across the whole width is a blade with a flexible body/hard tooth, the so-called Flex back. The blade is very flexible and has good sharpening resistance, so it can be used on thin-cutting saws no matter how many heads are on it, except for small power hand saws. One disadvantage of this type of blade is the fact that it can be resharpened until you grind away the hardened area on the tooth. After that you just have to throw the blade away.

And finally, the Double Hard saw blade. a blade that is hardened across its entire width. Technological tricks in the production of this blade do not go to waste. Not only do these blades hold their sharpening power excellently, but their high rigidity allows sawing at significantly higher feeds. This allows them to be used in much more energy-efficient sawmills, achieving significantly higher productivity. Such a saw can be turned for as long as its width allows. The saw keeps sharpening perfectly even after the hard tooth tip has been worn out.

Factors that affect the durability of the saw should include:

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

Speed of entry of saw into the billet. The sharper the saw enters the workpiece and the more often it does so, the worse for the saw. This is especially true in second row installations, where blanks can be quite short and the method of feeding the workpiece into the machine (end-to-end or with gaps) can have a decisive influence on the performance of the saw.

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Saws rotating at idle speed. The most important factor that affects its durability. This is especially true for first row sawmills working with logs. On these sawmills, the operator really only saws at best 50 percent of the time. The rest of the time it is working on the log, i.e. canting, clamping, unclamping, etc. If you stop the saw when it is not directly sawing the wood, it will significantly prolong its life. (Ed.But this recommendation should not be taken literally: if you stop the engine after every cut, you do more harm than good! When starting the engine the saw is exposed to great overloads, and it is not good for the starter gear. Stop the engine only when you are not working to load logs, turn the sawmill, etc.п.)

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