DIY wood band saw repair

Special machine for welding band saws

When might you need to weld bandsaw blades?

• During the operation of the band saw, it may break. In this case, repairs are required;
• Saws are supplied in coils and also require welding to prepare for work.

Technological difficulties of welding:

• Band saws are made of steels, alloys, bimetals, which are difficult to weld (for this reason, professional repairs do not use argon-arc, semi-automatic welding, and even more so brazing, which is much inferior in strength to any welding for obvious reasons). In addition, manufacturers keep secret information about what the saw is made of. Therefore, welding modes, as a rule, have to be established empirically.

• The shape of the tooth in the near-weld zone affects the magnitude of the load during operation.

The technological process ends with quality control of welded seams.

For the convenience of transporting band saws, they can be folded in two ways:
-ring;
- folding into a loop.

Further processing for wood saws.
If your saw is not prepared for work, you need to wire and sharpen it. The routing is done in half the thickness of the body, that is, if you have a 1 cm saw, respectively, the routing is done 0.5 cm per side. The setting goes: one tooth to the right, the second to the left, the third straight tooth - throwing out the shavings. On hard rock and on winter forest, it is advisable to do a ten less layout. When you sharpen, the stone must go through the entire profile, arson is not allowed.

For the convenience of work and to ensure accurate joining of the canvases, a simple device is made, consisting of a base, milled in such a way that it is possible to rest the back of the web against the side, and two clamping strips. The fixture can be made from regular black steel.

A saw welded on such a device can withstand more than thirty cuts in round timber (aluminum) with a diameter of 30 mm. The saw is cooked at the minimum current that is only possible to set on your inverter with the formation of a small reverse roller. Copper-bonded rod SV-08G2S is used as an additive. After welding, the saw should cool down in the tooling. The seam is cleaned mechanically to the plane of the saw.

The band saw soldering attachment can be used similar to the one we used for TIG welding. However, if during welding the edges to be welded came into contact with the metal of the tooling and provided a minimum heat dissipation, then for soldering the device in the place of joining the edges of the panels must be milled with a "draft". The ends of the saw are joined end-to-end along beveled edges, which can be obtained by machining on an abrasive wheel. Variable (c) depends on the thickness and can be up to 12mm. Beveled edges must be exactly and tightly fitted to each other, burrs, non-flatness of beveled surfaces are not allowed.

High-temperature brazing, its technology is no different from the technology of brazing any other products. As solders, it is rational to use silver solders with a high silver content PSr 40; PSr45, even better Psr65 (you can buy an imported analog of Castolin EcoBraz 38240 in the Svarportal online store in the "Consumables - Solders" section). Solders with a low silver content, for example, Psr25, are not suitable for soldering.Paste is used as a flux, or a dry powdery flux PV209 (read how to prepare it yourself). You can also prepare the paste yourself by taking ten parts of borax and mixing it with one part of ammonium chloride. Water is added to the resulting mixture to form a paste. When using Castolin EcoBraz 38240 self-fluxing solder, there is no need to use the above fluxes.

Brazing is carried out with a torch in an acetylene-oxygen flame, which has a sufficient heating intensity and a high combustion temperature. The solder should not melt from the burner flame, but from the heat of the heated metal. The molten solder will spontaneously be drawn into the tightly fitted saw joint due to the action of capillary forces.
The saw cools down to room temperature. Metal beads must be cleaned.

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Band saws are widely used in the entire woodworking industry, for joinery, furniture industry, etc. They are used in a variety of sawmills, band saws and band dividing machines.

A feature of band saws is a continuous cutting surface, which is a ring made of a metal band with teeth. For the manufacture of band saws, a previously prepared tape is welded into a ring. Welding is also used to repair torn saws. The technology of welding band saws will be discussed in the article.

It is divided into several stages - preparation, sharpening, welding and setting the teeth of the resulting saw. Due diligence must be observed at all stages. Let's consider the technology in more detail.

Repair of band saws has its own characteristics

As a rule, the machine for welding band saws works like this: the ends of the saw are clamped in the clamps, butted, and then a current is passed through them, which melts and welds the edges of the ends. The current is supplied through the electrodes, which are connected to the clamps.

There are different types of such devices. Next, we'll look at how they differ. They can be conditionally classified into three groups.

These machines are cheap, compact, not very productive and are intended for small amounts of work - for example, for repairing saws in production sawmills.

The peculiarities of the technology require high quality of preparation of the seam, high quality of electrodes, good adjustment of the clamps and correct setting of the mode.

The performance is much higher, such devices can be ranked as middle class. They work on the principle of continuous flashing and are intended for welding all types of blades, including bimetallic ones.

Features of the technology - high requirements for the surface of cloths and electrodes, the need to maintain the correct pitch of the teeth, taking into account the loss of metal. A correctly selected mode is characterized by a good, smooth flashing process throughout the entire welding process.

The welding process is automated; the operator is only required to install the saws into the machine and remove the welded blades. Such devices are distinguished by good performance and are used, as a rule, in service centers.

In addition to welding machines, when welding band saws, some auxiliary devices are required - blade guillotines, stripping machines, pyrometers, and so on.

Consider the welding technology. As mentioned above, it is divided into several stages, which will be considered in order.

Before welding the canvas, it must be prepared. Saw preparation consists of several steps.

The blade is cut by means of special guillotine shears. If these are not available, you can cut the blade with a chisel or a cutting machine. If the welding is supposed to be carried out along the section that was welded before, then on each side of the last seam it is necessary to cut off 5 millimeters.

The blade is cut between the tips of the teeth. An allowance of about one and a half millimeters is left on each side. The cutting line should be strictly perpendicular to the back of the saw.

Band saw, very flexible but fragile tool

The prepared canvas must be cleaned. To do this, they are cleaned of contamination, if necessary, cleaned with acetone or alcohol. The edges are treated with an abrasive material, removing burrs and irregularities - it is convenient to do this on a sharpening machine.

This is followed by welding of the web. The prepared web is fixed in the machine and welded.

The prepared blade is mounted in the clamping mechanism of an apparatus for welding band saws so that the edges of the blade completely coincide and are in the middle of the space between the clamps. Effort, upsetting mode and upsetting course are selected depending on the web - the documentation for the devices contains tables with information on modes for different canvases. The selected mode is set by turning the control knobs.

The machine is started by turning the switch or pressing a button. In this case, the current begins to be supplied to the electrodes and melts the metal at the junction. The movable clamp goes to the fixed one and forms a weld bead in place of the seam.

An important parameter is the current supply time. As a rule, with automatic welding it is one to two seconds, with manual welding it is controlled by the operator.

If the welding was unsatisfactory, the appropriate settings are selected and recorded; later they are used for welding similar fabrics.

The electrodes must be clean. Poor contact between the electrodes and the blade increases resistance and disrupts the welding process.

To connect the saws, a special installation is required

The saw is unusable immediately after welding. In order to bring it into proper condition, several operations are carried out.

When welding, the blade material hardens and becomes brittle. Annealing allows it to return plasticity and toughness. The saw is not removed from the machine, the draft is set to zero, a different current mode is selected. By pressing the button for annealing current, the seam is heated, and then slowly cooled. If there is no pyrometer, the temperature is monitored visually. The optimal color of the heated metal is cherry red. Orange or yellow color indicates overheating.

Cooling lasts three to five minutes. Some canvases require two cycles.

When cleaning the blade from the welded section, the influx of metal is removed, and the correct shape of the cavity between the teeth of the blade is also deduced. Any abrasive is suitable for cleaning, the best of all is a sharpening machine.

• The alloys from which the saw blade is made are difficult to weld;
• When working, the welding seam is subject to extreme loads;
• The geometry of the teeth in the seam area affects the stresses during operation.

From what you read above, you learned how the welding of band saws is carried out, what machines exist for welding band saws and what features this process has. We hope this information is helpful to you.

There are two main ways of joining band saws: resistance butt welding on special welding machines and brazing.

A large number of models of machines for resistance welding of band saws are produced. The most advanced of these provide an automated weld and anneal cycle that eliminates the possibility of operator error in timing the electrical impulse during welding and annealing. In the simplest devices, the welding and annealing times are controlled by the operator.

The simplest machine for welding band saws is shown in the photo below. It consists of a body (1), a welding transformer (2), a clamping mechanism with electrodes and clamping levers (3), a start button (4). The clamping mechanism, in turn, consists of a fixed (5) and a movable (6) clamps.The latter has a free play necessary for upsetting - the movement of the saw ends towards each other with the formation of a welding bead. Under the action of a spring that creates upset pressure, the ends of the saw are pressed against each other with a certain force.

The band saw welding process includes the following operations:

• saw cutting;
• stripping the ends to be joined;
• installation of the blade in the welding machine, selection of the current mode, setting the required force and upsetting stroke;
• welding of the blade;
• annealing the saw;
• cleaning the seam.

Cutting... Blades are best cut with guillotine shears, but can be cut with a cut-off wheel or chiselled. If the web has already been welded before, when re-welding, cut about 5 mm from each end.

In any case, the following conditions must be met when cutting:

• the junction should be located between the tops of the teeth;
• when cutting, an allowance for upsetting should be left (approximately 1.5 mm for each end of the tape);
• the cutting line should be straight and perpendicular to the back of the saw.

The latter is necessary so that the saw blade of the welded saw does not have a bend at the junction (along the back line).

There is a fairly simple way to accurately cut the band to be welded. It consists in placing the saw as shown in the figure below (middle image) and trimming or deburring both ends of the blade at the same time (complete). With this processing of the ends, even if the cutting line is not perpendicular to the back of the saw, its ends will nevertheless dock as expected, and the evenness of the blade after welding will be ensured.

Stripping... The saw ends are cleaned of dirt and degreased with acetone or alcohol. The edges to be joined are cleaned with an abrasive. They should be smooth and free from burrs.

Installing the blade into the apparatus... The prepared saw is installed in the clamping mechanism (one end in a fixed clamp, the other in a movable one) so that its edges meet in the middle of the free space between the clamps. In this case, their complete coincidence must be ensured.

The corresponding control knobs are used to set the force and stroke of the upsetting, the welding mode. All these parameters depend on the dimensions of the saws to be welded. The larger the cross-section of the saw, the more welding current is required and the higher the upsetting force.

In the instructions for the welding machines there are tables containing all the necessary settings, depending on the size of the saw to be welded. Often the welding modes are set without specifying a specific value for the welding current and voltage. To weld a specific saw, you just need to set the control handle to a specific position (I, II or III, for example).

Welding... The welding process is started by pressing a button or turning the handle. In this case, the current is supplied to the clamps, and from them to the ends of the saw, as a result of which the metal melts in the joint zone. Under the action of the spring, the movable clamp begins to shift towards the stationary one by the amount of the upsetting stroke, as a result of which a welded bead is formed in the joint zone, connecting the ends of the saw.

In addition to the value of the current strength, the most important parameter is the time of supply of the current pulse. Welding machines with automatic welding mode turn off the power supply after a certain time (usually 1-2 seconds). When working on machines that do not have an automatic mode, the welding time must be controlled by the operator.

The whole difficulty of welding band saws lies in the difference in the sizes of their blades and the materials from which they are made. Therefore, often after the first welding, which ended unsatisfactorily, the welder is forced to experimentally select suitable modes. It is better to do this on unnecessary scraps of the canvas.After the optimal mode has been selected, it is advisable to write down its parameters so that the correct mode can be applied to all saws with the same parameters.

It is very important to keep the electrode surfaces in contact with the saw clean. The presence of foreign substances between the web and the electrodes increases the resistance of the circuit and disrupts the welding mode.

Annealing... Annealing is necessary in order for the metal, which has acquired increased hardness and brittleness as a result of welding, to return its original (or close to it) structure, i.e. became plastic and viscous again. Annealing is performed in the same clamps as welding, but in the absence of upsetting force and in a different current mode.

Heating up to the annealing temperature (about 600 ° C) and slow cooling is sometimes carried out by pressing, holding and releasing the button that supplies the annealing current to the electrodes, while the annealing current supply button is periodically pressed to slow down the cooling. If the apparatus is not equipped with a pyrometer, the temperature is controlled by the color of the metal - when it reaches the annealing temperature, it should be cherry red. Do not heat up to orange or yellow, indicating a higher temperature. The gradual cooling during annealing can take about 3-5 minutes. Some canvases require two bake cycles. Sometimes welding and annealing are combined in one process, increasing the seam cooling time after welding by periodic inclusions of the heating current.

Cleaning the canvas... When scraping, the sag in the weld zone must be removed from the blade and the correct geometry must be given to the interdental cavity at the joint. You can clean it with almost any abrasive tool. The main thing is that the treated surface is flat and flush with the adjacent areas. When stripping, the circle should be guided along the seam, not across it.

Quality control of welding and annealing... When welding band saws, the following defects may occur.

• The welded edges of the web are displaced relative to each other (the surfaces of the ends of the web are not in the same plane). This happens when the upsetting stroke is too large or the current strength is insufficient.
• Ejection of melt onto the surface of the web. Observed when the current is too high.
• Lack of penetration. Occurs due to low pressure and low stroke of settlement or too little current.

In well-welded saws, the weld seam should protrude at least 1.5 mm above the surface of the blade.

The quality of annealing can be checked as follows - bend the fabric around a circle with a bending radius of 20-25 cm and look at its behavior. If the bending arc is close in shape to a circle, and the seam does not crack, then the welding and annealing were performed well. If the curved blade takes a V-shape, then the metal in the weld zone is too soft due to excessive annealing. Cracks in the weld zone indicate insufficient annealing (too fast cooling).

Preparing the canvas... Before soldering, the edges of the fabric to be joined must be free of dirt.

The connection of the ends of the saw is carried out end-to-end along the beveled edges obtained by sharpening on an abrasive wheel. The shape of the bevel is shown in the figure below, its value (c) fluctuates depending on the width of the web and ranges from 8 to 12 mm, but often the bevel is made much less. It is very important that the beveled surfaces are flat and that they fit snugly together. It is also necessary to ensure the value of the pitch of the teeth in the connection zone characteristic of the given saw.

Solders... The best solders for soldering band saws are silver (PSr-45, and even better - PSr-65). You should not use silver solders with a lower silver content, for example PSr-25 is not suitable.

Fluxes... It is best to purchase some kind of special paste-like flux designed for high-temperature brazing of alloy steels.The pasty form of the flux is most convenient for this job.

If there is no special flux, you can prepare a pasty composition yourself. Take 10 parts borax and mix them with one part ammonium chloride. Water is added to the resulting mixture until a thick paste is obtained.

In principle, one drill can be used as a flux, but it is inconvenient to apply it to the joint.

Equipment and fixtures... Brazing heating can be done in different ways, but the most common is heating with various gas burners. The flame on a gas burner should be either slightly oxygen deficient (if possible) or neutral.

The soldering temperature depends on the grade of the solder. If PSr-45 solder is used with a melting range of 660-725 ° C, then a heating temperature of about 800 ° C will be sufficient. Do not overheat the joint unnecessarily to avoid unwanted structural changes in the metal.

It is necessary to have a device in which you can clamp the ends of the saw in the desired position, precisely aligning the blades along the bevel and the back of the blade. A drawing of one of the possible options for such a device is shown in the figure below.

But simpler do-it-yourself options are possible.

Soldering process... Brazing of band saws does not differ in its essence from brazing with high-temperature brazing alloys of other products (for more information on brazing, see the articles Soldering metals and Brazing). It is performed in the following sequence.

The beveled edges are coated with flux, and the ends of the saw are clamped in the fixture so that the edges fit snugly against each other, and the backs of the ends of the blade are pressed against the protrusion in the fixture. When applying the flux, care should be taken to ensure that it does not cover any other saw surfaces other than the bevels themselves. This will prevent the solder from flowing to those planes where it is not needed, and from where it will have to be removed after soldering.

The connection is heated with a torch to the desired temperature and solder is fed into the joint joint. The melted solder spontaneously, due to capillary forces, is pulled into the joint between the canvases, as evidenced by the appearance of its strip along the entire perimeter of the joint. Very little solder is required, so there is no need to melt the excess.

It is necessary to allow time for the connection to cool down for several minutes, and only then remove the saw from the device. If everything is done correctly, then there should be practically no beads of solder on the canvas. If there are any, they need to be removed by careful cleaning.

For the band saw to function properly, it is welded. The method by which this process is performed is selected individually, in accordance with the peculiarities of the operation of this material. About equipment for welding band saws, we will consider further.

There are a large number of different saws, which have individual characteristics of use and a peculiar design. Some use a disc as a cutting tool, while others use a tape.

Installation of the saw band is carried out on the pulleys of the driving and driven directions. To tighten it, you should make great efforts, only in this case, the cutting line will be uniform.

The main features of this design are individual blocks, which are supplemented and built up independently. On a simple device, the material for cutting into which is fed manually, additional mechanisms are installed, such as an electronic system for monitoring the device's performance, thanks to which it works without the outside participation of a person.

Among the main structural elements of the band saw, we note the presence of:

• a frame on which there are guides with which the tape moves;
• in order to tighten the belt, a mechanism is used, which has a spring, mechanical and hydraulic drive;
• tape holder for cutting;
• a screw-type lifting mechanism, which is installed near the belt;
• belt-type transmission, on which the wedges are located;
• an electric motor with a capacity of about fifteen kilowatts or a gasoline engine with the same capacity;
• eccentrics, with the help of which the log is fixed on the frame;
• a water tank and a tap that soaks the part during the sawing process;
• rail strip on which the structure moves.

Also, each saw features individual design features such as guardrails and thrust mechanisms that enhance safety. In order to regulate and customize the work on the working surface, there are strips on which the markings are applied.

The principle of operation of the mechanism is based on the laying of a log between two guides and its rigid fixation. To determine the thickness of the board, it should be lifted using a special mechanism.

In order to connect the two ends of the saw band, weld them together. This process is carried out using special equipment for welding band saws. Resistance welding of a band saw consists in the fact that electricity passes through the two connected ends of the saw, which leads to their overheating and melting of the edges on the blade. For supplying current, electrodes are used, connected to the clamps.

There are a huge number of welding machines with which resistance welding is performed. Some advanced options are capable of automating the welding and annealing cycle. Therefore, errors associated with excessive welding or incorrect timing during which the impulse is transmitted are excluded. In simpler mechanisms, the control of the annealing and welding feed is carried out by the operator.

Self-welding of a saw band is possible only if you have experience with this kind of equipment. Among the main design features of the band saw welding machine, we note the presence of:

• body part;
• welding transformer;
• clamping mechanisms with electrodes and clamping levers;
• start button;
• clamps: movable and fixed.

The main function of the movable clamp is free travel, with the help of which upsetting is carried out. As the saw ends move towards each other, a bead is formed. In order for the ends of the saw to be pressed against each other, a special spring is used to create pressure.

Do-it-yourself band saw welding consists of the following stages:

• saw cutting;
• cleaning of its end sections;
• installation of the blade into the structure of the welding machine, determination of the operating mode: stroke and shrinkage;
• welding of canvases;
• performing annealing;
• cleaning of seams.

The first step, cutting, involves determining the size of the saw. Use guillotine shears or a cut-off wheel to cut off the desired section of the blade. When using a blade that was previously welded, about five centimeters is cut off on each side.

In this situation, when performing cutting, a number of rules should be taken into account:

• the place at which the blades are connected to each other should be located between the upper parts of the teeth;
• in the process of cutting, a little allowance should be left to compensate for the shrinkage of the metal, the optimal allowance is one and a half millimeters on each side;
• try to make the cutting line as flat as possible, the quality of further welding depends on it.

Only in this case, the canvases will have a straight line at the bend.

A fairly simple way to perform cutting is to place the saw in a certain position, trim and clean each of the ends separately.In this case, even if there is a non-perpendicular cutting line, its end sections will still be joined. In this case, the fabric after welding will differ in an even seam.

Further actions are related to the performance of cleaning the canvas. These areas should be cleaned of dirt, degreased with acetone or alcohol. Use an abrasive to sand the edges. As a result, you should get perfectly flat and smooth areas.

This is followed by the installation of the canvas on the surface of the device. The prepared saw should be installed inside the clamping mechanism. At the same time, one part of it remains mobile, while the other does not. In the central part, the saw edges are connected to each other. The coincidence of the edges must be perfect.

With the help of the control knobs on the device, the effort, stroke, shrinkage, operating mode of the device are regulated. These parameters for each saw are selected individually and depend on its size, steel thickness, operating characteristics, etc. With an increase in the cross-section of the saw, the current required for welding increases.

In order to more accurately determine these parameters, use the instructions for the device. It should contain a table according to which the operating mode of the equipment should be determined. In some devices, it is enough to select only the welding mode, without specifying the current and voltage for operation. In order to weld the saw, the lever must be set in a certain position.

Saw band welding is done by pressing a button or turning a lever. After that, the current is applied to each clamp, and from them is transferred to the saw. Thus, the metal in the junction zone of the two sections is melted and joined together.

The spring acts on the surface of the movable clamp, which is displaced towards the fixed clamp, on the draft. At the same time, a weld bead is formed in the butt zone, with the help of which the saws are connected.

Determining the welding parameters, you should choose the time during which the current pulses are applied. Welding machines with an automatic mode of operation turn off the current after a few seconds from the moment they were supplied. However, if this parameter is manually adjusted on the welding machine, then you need to monitor it.

In the process of welding, certain difficulties arise associated with the material from which the saw is made. In accordance with this parameter, the operating mode of the welding machine is determined. In some cases, it is very difficult to determine this parameter without experience. If in the end the welding did not satisfy you, then you should experiment, choosing the necessary mode for unnecessary trimming of the canvas. After selecting the optimal operating mode, write down its parameters in order to apply it in the future.

Please note that the electrodes that come into contact with the saw must be clean. Foreign substances or dirt on their surface adversely affect the quality of the saw welding.

Further actions are associated with performing annealing, which helps the metal, which has become brittle and rather hard during the welding process, to acquire strength, toughness and ductility. For annealing, the same clamps are used as in the welding process. However, a different current supply mode is used for operation.

The optimum temperature for annealing is about six hundred degrees. At the same time, the cooling of the device should be maintained at a slow pace; for this, the current supply button should be held, pressed and released at a certain time. In order for the metal to cool down gradually, periodically press the current supply button for annealing.

If there is no pyrometer on the welding machine, then the temperature is controlled by the external characteristics of the metal surface. During the firing process, the steel takes on a cherry red hue.In no case do not heat the metal to orange or even more saturated red. The process of gradual cooling of the metal takes no more than five minutes. Some canvases will require two annealing cycles. In some cases, welding and annealing are performed in the same process. In this situation, the time for cooling the seams is increased by periodically supplying current to the metal.

After welding, the fabric should be cleaned from the bead formed on the welded seam. Almost any abrasive tool is suitable for cleaning seams. The main condition for high-quality cleaning is to obtain a flat and smooth surface.

We suggest that you familiarize yourself with the main errors that occur during the welding process:

1. Offset of welded edges - in this case, the blades are in different planes. This problem occurs when there is insufficient amperage during the welding process or when there is a very large settlement.

2. The melt on the web is observed during the supply of a very high current.

3. Uncooked spots are formed when the pressure supplied to the system is too low.

The minimum value of the seam protrusion on a well-welded plate is about one and a half millimeters.

To check the quality of annealing, the web is bent within a radius of twenty centimeters and inspected. If the arc resembles a standard circle and the seam remains intact, then the quality of the weld is at the proper level.

The cost of welding band saws is determined primarily by their size, steel thickness and operating characteristics. However, there is another way to connect the saw - this is soldering. This option is easier to do at home than welding.

First of all, you should prepare the blade, for this the saw edges are cleaned of dirt and degreased. The ends of the web are connected in a butted position, however, the edges must be beveled.

Use an abrasive wheel to make the bevelled edges. The optimum bevel is eight to twelve centimeters. The beveled areas should be connected as evenly as possible.

In order to solder the saw, you will need solders, the best option is silver PSR45 or PSR65. Solders with a lower silver content are not recommended.

As a flux, it is preferable to use a paste, which is used in the process of metal soldering. This version of the flux is easy to use. In the absence of this substance, it is possible to make it independently. For this, ammonium chloride is combined with borax in a ratio of one to ten. With the help of water, the consistency of the composition is regulated, which should become pasty.

A gas burner is used to heat the saw during the soldering process. The heating temperature is determined by the type of solder, the optimal value is from 650 to 600 degrees. Do not overheat the metal in order not to destroy its structure. With the help of a special device, the ends of the saw are connected to each other. The soldering process is as follows. First of all, the flux should be applied to the surface of the edges. Try to apply the paste exclusively to beveled areas.

Further, the joints are heated to a certain temperature and the solder is fed to the junction of the saw ends. After that, a strip appears on the surface, indicating that the soldering is done correctly. The solder is melted not under the influence of the torch, but from the previously heated metal. After a few minutes, the metal cools down, only after that, the saw is removed from the mechanism. In the presence of small nodules, the seam is cleaned with any abrasive material.

Welding band saws video: