Among carpentry tools, bow saws have long occupied an honorable place. And, although their construction and design have changed significantly over the years, the basic principle of operation of these saws remains the same. What is the advantage of this tool and what sets it apart from the rest?
Why do you need a bow saw?
It is convenient to make short, mainly transverse cuts with a jigsaw, and long, longitudinal hacksaw. And only with the help of a beam saw it is possible to produce a variety of dividing cuts, both with dry and wet wood. In addition, for a beam saw on wood, the method of cutting wood does not matter. along or across the fibers. If we add to this the possibility of working with one hand (the first "beams" were exclusively two-armed), it turns out that the tool in question can be used to cut the tree:
- in the longitudinal;
- in the transverse;
- in figured;
- in the angular direction.
The only insurmountable obstacle for beam saws is the transverse dimensions of the workpieces. for thick logs it is still better to use a mechanized tool. However, with thick logs you have to work much less.
Three things give universality to wood saws:
- Adjustable tension of the saw blade (in some ways, this process is similar to pulling a bow string, from where the name of the tool appeared). Testing shows that in beam saws tensile forces of up to 100. 120 kg can be created without destroying the saw blade.
- A special shape of the teeth that allows both roughing and finishing cuts.
- The compact size of the saw, which ensures its use even in confined spaces.
Modern manufacturers of hole saws and accessories for them. trademarks Bahco, Stanley, Intertool, Fiskars and others. complete their products with different types and designs of saw blades, which increases the ease of use of the tool.
Arbor saw device for wood
Modern "onion" includes:
- Frame from profile hire. Depending on the dimensions of the saw blade. and they are usually standard: 350 mm, 530 mm or 760 mm, the frame can be made in the form of a weaved trapezoid (for longer canvases) or a forged triangle (for shorter ones).
- A handle, the profile of which eliminates sudden injury to the fingers of a worker.
- Saw blade.
- Devices for tensioning the saw blade.
- Fixture of a cloth to a frame.
Video: Wood Saw For What You Need
There are special requirements to the frame of a bow saw on wood. it must be rigid and at the same time light so as not to increase physical activity during sawing. The task is satisfied by a special tubular profile with a very small width. This makes it easy to bend it during the manufacturing process to the desired frame configuration, without losing the strength of the part, providing the saw with the necessary mobility.
One of the main differences in the design of modern wood saws is the principle of saw blade tension. For example, Gardena or Proline brands use a handle with an eccentric for tension: by changing the angle of the handle with respect to the longitudinal axis of the saw, the tension can be adjusted in this way.
Bahco Stanley saw manufacturers went the other way: a special screw mechanism for saw blade tension is mounted in the handle there. The choice is determined by the ease of use, however, the presence of a screw mechanism provides increased accuracy to the tension, and does not depend on random movements of the user, when the position of the handle during sawing can randomly change. Therefore, the rotary tension mechanism is recommended to be used in the presence of some experience with a beam saw.
To fasten the saw blade to the opposite part of the “bowstring” (frame), removable cotter pins or wing screws are used. The latter are more reliable since the cotter pin, usually made of mild steel, wears out over time and can spontaneously exit the mounting hole.
Bow saw blade
The versatility of this tool also determines changes in the design of the saw blade, in particular, its teeth. Most commonly used:
- Saw blades with uniform tooth pitch. They are designed for smooth cutting of wood with a relatively short length.
- Cloths with the so-called “American” tooth, when after 3.4 ordinary teeth a double or “Kremlin” tooth is encountered. This configuration of the cutting part of the saw blade allows for a longer and more complex cut. The frequency of rotation determines the accuracy of the result: the closer the twin teeth are, the less the line will be less clean.
- Spatial teeth with wide dilution. Canvas with such teeth is useful at maximum cross-sectional sizes of cut wood. At the same time, the cutting force and the amount of waste increase, however, sawing performance becomes the maximum possible.
Depending on the tasks, the material of the saw blade changes. For tools of relatively small sizes (350 mm, partly 530 mm), uniformly spaced webs are used, which are made of structural chromium-nickel steel of type 45X, 40XH or 45G. The blades undergo hardening of the HDTV, as a result of which their surface hardness reaches 45. 48 HRC. However, such blades are very sensitive to a change in the sawing axis, which easily changes due to the flexibility of the blade, and break under extreme bends.
For double-tooth blades, 7XF high-carbon steel or even high-speed steel is used. The durability of such canvases (if they are not made in China) is very high, because with an increase in the percentage of carbon in steel, its elastic properties increase. In addition, the blades do not need to be cooled, since vanadium and tungsten, which are part of such steels, are characterized by high heat resistance.
For teeth with wide breeding, abrasion due to friction of wood against metal is considered a decisive factor in durability. Therefore, the Finnish company Fiskars applies a teflon coating to the tool it produces, which reduces the coefficient of friction, thereby increasing the durability of the saw blade. Other manufacturers (for example, Bahco) produce bimetallic blades: the base is made of structural steel, and the cutting part is made of tool steel.