How to break out the band saw correctly. Cutting elements of band saws
Saw tooth set on larch
Band saws belong to the category of cutting tools and are an integral part of specialized woodworking equipment. It represents a closed band, on the outer edge of which there are teeth.
Special varieties of steel are used for manufacturing. 9KhF, B2F or C75. During production, the teeth are treated with high-frequency currents. This increases their hardness. It is this fact that affects the cutting edge setting and repairability. Often several types of steel are used in the manufacture. The main band is made of spring steel, and the cutting part is made of steel with a large m of tungsten or cobalt.
Features of wood band saws applications:
- wood requirements. The harder it is, the faster the blade will blunt;
- installation conditions. Tension value must be complied with. If it is less than required, sagging will occur. A strong tension will increase the chance of blade breakage;
- occasional sharpening. This requires a special machine.
The last point will increase the service life of the belt construction. However, sharpening on their own is problematic. you need to pick up the correct setting, observe the angle of processing blades.
When buying a used saw, you need to pay attention to the presence of repair welds on the blade. They are an indicator of frequent tool breaks.
Design of a band saw
Band saws belong to the category of cutting tools and are an integral part of specialized woodworking equipment. It is a closed band with teeth on the outer edge.
Special steels are used for production. 9XF, B2F or C75. During production, the teeth are treated with high-frequency currents. This increases their hardness. It is this fact that affects the separation of cutting edges and repairability. It is not uncommon to use several types of steel. The main band is made of spring steel, while the cutting part is made of steel with a large amount of tungsten or cobalt.
Features of wood band saws applications:
Band Saw Basics
- wood requirements. The harder it is, the faster the blade will blunt;
- installation conditions. Tension value must be observed. If it is less than required, there will be sagging. If the tension is too high the probability of blade breakage increases;
- periodic sharpening. This requires a special machine.
This last point will increase the life of the band construction. But it is difficult to sharpen it yourself. it is necessary to choose the right setting, to observe the angle of the blades.
When buying used band saws one should pay attention to welds on the blade. They indicate frequent tool breakage.
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saw blade material
Band saws are made of different materials. depending on what material they are designed to cut.
Wood band saws are made from tool alloy steel, which has a hardness of 40-45 HRC. Domestic manufacturers use steels 9KhF, V2F (for band saws on metal) and others., Foreign. their steel (C75, Uddeholm UHB 15, etc.).). Tooth hardening of such saws by high frequency currents leads to hardness up to 64 HRC and more.
Saws for cutting of carbon steels and non-ferrous metals with small thicknesses are also made of tool steel with teeth hardening by high-frequency currents. However, to cut metal more often bimetal saws are used, where the blade is made of spring steel and the band on which the teeth are cut is made of high-speed steel with high m of tungsten and cobalt. After quenching it gets hardness up to 65-69 HRC. Fast-cutting steel is welded to the base of the saw with an electron beam.
Bimetal band saw production
Bimetal saws can cut thick metal of tool, stainless, heat-resistant and other steels, titanium alloys and other metals.
1240 Wear-resistant teeth are made by welding over stellite (chromium-cobalt alloy with additions of tungsten and/or molybdenum) or by soldering hard alloy plates to them. These saws outperform bimetal saws in cutting ability. Used for cutting fiberglass, automotive tires, cables, reinforced plastics, heat-resistant alloys, graphite, aerated concrete, bricks, and other difficult-to-cut materials.
Bandsaw with carbide-tipped teeth
In band saws, the depth of cut is an important parameter. It indicates how thick the workpiece will be cut by the tool. For various band saws this parameter can be from 8 cm to 50 cm. It depends directly on the motor power. It is clear that household saws do not cut as deep as professional saws. There is also a parameter for the cutting width. Its value influences the maximum allowable width of the cutting board. For band saws for private use the cutting width is 190 to 300 to 400 mm. Professional band saws can cut a half-meter board and even 610 mm wide workpiece.
Saw blade: material, size and teeth The key to choosing a band saw. Choosing the right saw.
Material. The best band saw. Made of carbon steel. It is heat-treated and becomes very hard and durable
That’s why it’s worth looking at American band saws. They are considered the best in the industry.
Cutting parameters depend on them. The longer and wider, the more often you can cut workpieces. And the greater the working speed. But for domestic work, especially for curved and oblique cuts, it is better to choose medium-length parameters.
They saw the teeth. Their quality and sharpening must be perfect. After all, they affect the smoothness of the cut. The more teeth a band saw has, the smoother the cut. An important nuance in the choice is the tooth pitch. For the band saw to work well, the number of teeth must be a multiple of three. There is an alternation of alignment of teeth: right, left, straight. The best variant. 210 teeth with ¾” pitch or 180 teeth with 7/8″ pitch.
If the band saw has more than one toothed tooth, cuts may occur.
Correct sharpening process
It is a proven fact that over 80 percent of tool breaks are caused by improperly sharpened band saw teeth. Check the condition of the kerf to determine if sharpening is necessary
Resharpening wheels for band saws depend on the hardness of the tooth. Corundum wheel is used for tool sharpening of tool steel. Bimetal saws are sharpened with diamond or borazon abrasive. Tool wheel shape must be determined according to the parameters of the saw. It can be cup-shaped, profiled, dished or flat.
Before using the saw in operation, it is necessary to keep it in a suspended twisted position for about eleven hours.
- it is necessary to remove metal evenly along the profile of the tooth;
- Excessive pressure on the wheel (this can cause damage to the tooth);
- mandatory use of coolant;
- Ensure the preservation of the geometry of the tooth;
- deburring prevention.
The standard instruction says that the tool should be sharpened either along the front edge of the tooth or along both the back and the front edge of the tooth. In practice, many craftsmen and professionals carry out sharpening only on the back side, so, in their opinion, it is more convenient.
This tool is rather unpretentious in terms of sharpening
, Despite the mass of requirements and rules. Sharpening can be performed either manually or with a special sharpening device; use different grinding wheels for processing, etc.д.
Before you sharpen the tool, you should familiarize yourself with the main types of implementation of this operation. Also on the Internet you can watch videos.
Types of sharpening
If you do not have an engraver or a machine, you can sharpen the tool by the usual old-fashioned method using a nail file
With diligent and regular practice you will quickly become proficient at sharpening by hand.
- When sharpening the tool on the machine it is necessary to make sure that the sharpening blade is positioned correctly in relation to the saw before starting the sharpening operation.
- It is necessary to remove such a layer of metal from the grooves to guarantee the elimination of all microcracks.
- If the saw has been operated without quality maintenance for longer than that allotted by the manufacturer, the layer of metal removed per sharpening should be increased.
- Always use a new sharpening tool as a reference.
- The shape of the saw’s cutting part is a parameter that has been fine-tuned and developed over the years. Therefore it is not necessary to deduce your parameters and hope for a good quality of work.
- If you follow the rules of operation and the manufacturer’s requirements, the band saw will last until its width is reduced to 65 percent of its original size. The width decreases as the teeth are resharpened.
- It is mandatory to remove burrs during tool sharpening, otherwise it will lead to the formation of micro-cracks in the process of sawing materials.
- The tool must be immediately cleaned of sawdust and resin after finishing work, and the saw must be carefully inspected before sharpening. Otherwise you will clog the sharpening disc with shavings, which will lead to improper sharpening of the band saw.
The procedure for deburring and sharpening a band saw
When choosing a band saw to organize production activities by processing wood, quite a lot of attention is paid to what characteristics the saw has: size, material of the cutting edge, production technology and so on. However, it is worth remembering that regardless of the type of cutting element, deburring and sharpening must be carried out periodically.
Preventing Bandsaw Blade Breakage and Proper Tension EthAnswers
This is due to the points below:
Sharpening and setting depends on how well the machine works
If the work was not done correctly, the sawing can take place with rapid wear of the teeth. It is important to work with maximum precision. The latest models are able to sharpen and set with an accuracy of up to 0.1 millimeter
Such a high degree of precision makes sawing easier and smoother. Depending on the production line capacity the procedure has to be repeated more often. That’s why a band saw sharpener has to work fast, the whole process is automated if possible, which also prevents the possibility of faulty setups.
In recent years the double-sided band saw blade sharpening machine from various producers is used more and more often.
Setting two teeth at once
Machines which produce two teeth at once are made of the following kinds: together with sharpening machine; separately only sharpening machine powered by motor; separately only sharpening machine with manual feed as a wheel ( photo 1 ) or lever.
For illustrations see the PDF version of the magazine
The manual wheel feed saw
Machines for this variant are advertised by salespeople the most because they seem to make the work of the sharper easier by setting two teeth at once on both sides of the band saw. This is a very good sales pitch to the ears of those who have never set up band saws on their own. Anyone who has ever set up a band saw knows that each tooth on the saw is set individually. The tooth is always set back by the plunger by more than the necessary amount. When you pull the pusher back the tooth always springs back by some value. And even for a single saw the spring back of each tooth can range from 5 to 25. So the sharpener almost always has to make two or three presses, often to different indicator values each (i.e. with different forces) to get the necessary degree of separation. There are also teeth that spring worse than others and already with one or two presses to the indicator readings, as with well-sprung teeth, remain at values greater than the necessary pitch, and they have to be bent back on purpose.
You should know by now that it’s not possible to set two teeth well apart with just one push. But the machines are selling well, and some are even happy with the result. When setting up the saw on a band saw blade you should always know that you are never guaranteed to get a good set. There will always be an unpredictable amount of separation. With small carriage feeds, an occasional batch of saws with more or less equal spring back, a new clean mechanism can sometimes make a good cut. But problems are bound to arise afterwards. But people start to look for the cause of these problems everywhere except in the saw blade, thinking it’s very good. Almost all such circulars manufacturers don’t even put indicators on. Explaining it by the fact that you set everything once, and after that you only sharpen it: hammers always hit the same way and there’s nothing to check. Check it out and see for yourself how much variation there really is in the setting values.
What’s more, the accuracy of the resulting camber on these machines is very much the same as on the classic machines: dirt in the mechanism, risks on the pusher stop and baseplates. Especially the height of the set part of the tooth has a big influence.
Design features of band saws
Please note! To keep your machine running reliably and efficiently you need to handle it with a great deal of responsibility. Sharpening and setting of band saws in wood has to be done in time and competently.
Profile, teeth and sharpening angle
International Classification of Tooth Profiles.
Band saws have different tooth geometries, depending on the type and characteristics of the materials to be cut. The woodworking tool can be a joinery tool and a dividing tool. There is also a third type, designed for sawing logs, logs. All these subspecies have their own parameters and shape of teeth.
The sharpening angle of band wood saws is chosen by the manufacturing company based on several points. The main one is that the harder the material, the smaller the front angle should be. Here is a table with the basic parameters of the saws.
How to properly sharpen a band saw
Immediately note that if there is no experience and skills to perform such works, it is better to entrust the sharpening of saws to professionals. Improperly set teeth geometry, scale on the metal, or improperly set teeth will markedly reduce blade life.
Deciding to sharpen a band saw with your own hands, it is not unreasonable to first become familiar with the key definitions, the knowledge of which may be required in the process of work. So, for the correct formation of a cutting edge you need:
- setback. deflection of teeth from the plane of the main saw blade;
- tooth height. the distance between the top point and the base;
- pitch. distance between teeth, usually varies from 19 to 25 mm.
- Sharpening angle. depends on the purpose of the tool; for example, the recommended sharpening angle for table saws is 35°, for circular saws. 18-22, for sawing timber. not more than 15°.
Angle of sharpening is defined by the manufacturer, therefore it is recommended to adhere to these parameters when dressing the saw yourself.
Here is a detailed instruction that will help to properly sharpen a closed circular saw without resorting to the services of specialists.
Deburring of band saws in wood is the first stage of cutting edge profile restoration. tooth location may change during the operation, so it does not make sense to sharpen the saw blade until the geometry is correct.
- classical. the teeth are alternately deflected to the right and left side;
- Stripping. 1st and 2nd teeth are deflected in different directions, the third one remains flat. This profile is created for cutting hard materials;
- wavy. the most complicated version, reminding of a wave shape. Each tooth is given an individual shape here, and this type of profile is usually made only in specialized workshops.
It should be noted that when cupping, not the entire tooth is cupped, but about 2/3 of the top part. The procedure is performed on a special machine for setting band saws. The cost of such a tool is quite high, so it is bought if several tools need to be adjusted. Its availability can become the basis of sharpening business.
Of course, you may not get it right the first time, even on the adjustable machine, so at least the geometry of the profile should remain the same as before the start of the work.
This is the main straightening stage of the cutting edge and can be done in two ways.
Full band saw sharpening is done with an CBN wheel mounted in a special sharpening machine.
This is a fully automated operation that is used by professionals. The wood band saw sharpener is controlled electronically, and the sharpening wheel processes the entire band in one pass. The disadvantage of this method is that the CBN is customized to the profile of the saw, so for straightening different tools the sharpening element must be in stock.
Tooth sharpening is either manual or using a sharpening machine.
Please note! This is the method used for resharpening band saws by yourself. A regular emery wheel or emery board can be used here.
In the first case, it is possible to restore the sharpness of the teeth in the shortest time, but the work requires certain skills. In the second, painstaking work: 4-5 movements on the edge of each tooth.
Diamond, CBN and corundum grinding wheels are used for automatic sharpening. It is important to realize that this procedure only sharpens the teeth, the geometry created after setting the blade must remain unchanged.
Types of sharpening. The nuances of performing the operation
Before making a tapering on a band saw, you must first decide on the type of deflection. There are several types in total:
- classic set. Distinguished by the fact that the teeth are alternately bent in different directions. That is, one element is bent to the left, the second to the right;
- scraping. Slightly different from the first variant. The essence of it is that two teeth are set in different directions, and the third is left unchanged. The band saw’s head in this way is done in the case of cutting hardwood;
- wavy. The most difficult method in the performance. Here the bending amount of each tooth is individual, ensuring a wavy configuration of the cutting edge.
There are several important nuances to keep in mind before making the cut on band saws:
- The size of the bend on all teeth must be the same (does not apply to the wavy method);
- The cutting element must not be bent at its base, but only in its part;
- the force should be applied in a strictly defined point.
Now about how to properly bend band saws for sawmills. As already noted, this operation is performed on a special machine. The essence of the work boils down to the fact that the blade is fixed in the frame. Then calibrate the indicator. Next, the operator sets the lever that will be used for bending (selects the place where the force is applied).
After the installation work, the operator unbends the tooth, checking the indicator for the amount of bending. Then the band is moved in the frame and the operation repeats, but with a different cutting element.
An outward indication that your saw is properly bred is that 80-85% of sawdust is ejected from the kerf.
If you saw too much air and not enough sawdust removed.
if the saw is not wound up, dense, hot sawdust will remain on the board surface.
A saw that is set too far apart will cut jerkily, a saw that is not set apart enough will cut in waves.
one more very important point: only the top third of the tooth should be turned, and only the sharp corner on the tip of the tooth should be involved in the sawing process.
Sharpen the saw with minimal metal removal (t.е. deburr) and then sharpen.
If you have a sawing problem, read the 13 points below. this will help you.
The saw jumps up when it enters the log and cuts straight up to the end of the log, then drops back down. This phenomenon is called “squeezing”.е. the saw is pressed off. This is caused by too high an angle of sharpening of the tooth. Sharpening angle has to be reduced by a couple of degrees.
The saw jumps up when entering the log and the board tends to get “saber-like” curves. This is most likely because the sharpening angle is too great and the pitch is too narrow. The sharpening angle of the tooth should be reduced and the degree of separation increased. The saw plunges downwards and the board is curved “like a sabre. This is caused by an insufficient sharpening angle and insufficient setting at the same time. Sharpening angle needs to be increased by a couple of degrees and the pitch needs to be increased.
Too much sawdust is left on the board and the sawdust is loose to the touch. The pitch is insufficient, it needs to be increased. Sharpening angle should be decreased.
The kerf comes in waves. If the saw is too sharp, the pitch is too small, increase the pitch.
Blunt, never resharpened saw cracks in the tooth flanks. This is caused by the blade not being sufficiently set for the job it is trying to do, or by the blade continuing to saw after it has blunted.
Saw is covered with cracks on the back. This is caused by the rear stops of the guide rollers being too far back from the back of the blade.
Sawdust is “rolling in” on the saw blade. This is caused by the saw not being sufficiently set and not enough air remaining in the kerf, the saw blade rubs against the sawdust, it heats up and the wood dust bakes up on the saw. Increase the amount of separation.
Sawdust is “rolling” on the inside of the tooth, but not on the saw blade. This is caused by poor quality of sharpening (too much feed or too much metal removal and the resulting poor surface quality at the tooth tip), or by the tooth being ground too far back, or by the blade continuing to saw after it had already dulled.
After sharpening, the blade is covered with cracks in the tooth flanks. During resharpening, too much metal is removed in one sharpening and it will result in overcalculation of tooth surface.
Many problems are created if the sharpening stone is not sharpened often and accurately enough.
Remember that no matter how good your sawmill is, it’s only a device that “pulls” the saw through the log. The end result depends 90% on proper saw maintenance and only 10% on the overall machine setup.
Do not forget that sawing with an unsharpened saw. is the fastest way to break it.
Sharpening angle. is the deflection angle of the tooth face from the vertical. The sharpening angle recommended for most applications is 10 to 12 degrees. For sawing hardwood and frozen wood, a sharpening angle of 8 to 10 degrees. For softwood 12 to 15 degrees.
Tooth setting. is an important factor in blade performance. Keep in mind that when you sharpen the teeth and decrease their height, the tap also decreases.
Resharpening parameters of band saw blades depending on the type of wood (see table below).).