knowledge of wood

Knowledge of wood

Wood is probably, next to stone, the first material from which man is made made tools and accessories for himself. The first aid of primitive man was not could be nothing but some club, stake, branch, or thorn, the trace of which disappeared in the centuries of past time.
Wood did not only have an advantage over others in the past materials, it still has primacy as the most widely usedout material. However, as a tool - especially after occurrences plastic mass - is suppressed, because the multitude of "wooden" tools such as tool handles, planer bodies, etc. they make today from plastics. Today, wood is mainly used as material, starting from the roof structure to the skeleton moparts of the plane, from bulkheads to wooden figures.
Knowledge of wood
At first glance, it seems very easy to find your way among the treesmaterials. However, this is not so: for discernment, classification, use and processing of wood is necessary professional knowledge.
When working under his own direction, man meets wood as with sawn timber, i.e. semi-finished product. Such mothersthey were: laths, beams, planks, boards and slabs. All these materials they can be made of soft or hard wood. Difference between these materials both in the field of processing and in durationburden is great. Soft wood is recognized by its larger fibers, apparently weak structure and easy compressibility. Almost the most the soft wood used is fir. Fir wood is easy and good can be shaped. In the house and around the house, it is used to make: doors, windows, frames, etc. The elders used to say that us soft wood follows through its entire life, starting from the cradle to coffin.
Hardwood is fuller, more massive and heavier. One cubic a decimeter of roughwood has a weight of 830 g, and the same volume of soft wood only 450 gr. Hardwood fibers are dense distributed and show fine lines. Hardwood is more difficult to split and there are fewer splinters. A good example for displaying traits hardwood is a broom handle, handles of various tools and parquet. Trees with needle-like leaves, evergreen, are soft, and from deciduous, birch, poplar, willow and linden are considered soft.
Only dry wood with less than 13% is suitable for processing. moisture. Wood contains moisture not only when immediately after felling is processed (it is often jokingly said "on this tree was recently sung by a blackbird"), but also when it is in progressthe puppy had the opportunity to absorb moisture. It is known that wood is hygroscopic, but quickly absorbed water is slowly released from it evaporates. Soft wood must be aged for at least two years after cutting years, and hard four, in order to dry enough for processing. Of course, this is the case when drying is done in free conditions, i.e. naturally. Now there are modern computer systems and condensing dryers that manage the wood drying process and the time for quality dried wood has been reduced many times over.
When water evaporates from wet wood - especially when drying and moistening several times in succession, the wood is significantly deformedmouse, it "works". This is understandable if you consider that the moisture absorbed by the tree can amount to 130% of the dry matter tree. Deformation largely depends on the placelasting cross-section of the tree, from where the lumber was cut. If the understanding of the deformation would not, due to some concepts, remaino incomplete, let's first familiarize ourselves with the names of the parts that form the structure of the tree, using Figure 1.
wood structure
Figure 2 shows how planks and beams are deformed cut from individual parts of the body. The most important characteristic of wood is: the volume of wet wood decreases due to drying. Working that's what you need when making objects from wood elements "fit" well and cut them to a slightly larger size instead of less. (One obvious example: in a wooden trough that the housekeeper pours water so that the tree swells and the trough swells stopped leaking water. The board absorbs water and swells so much that the cracks "close" and the trough no longer leaks).
wood deformation
A characteristic feature of wood is that it is more resistant to in the direction of the fibers, but it is easy to screw up, while it is perpendicular to the direction fibers break easily. Resistance varies greatly with addiction from the density and uniformity of fiber distribution. Thicker fibers provide greater resistance, and in the place of looseness and unevennessthe resistance of evenly spaced fibers decreases.
Sawn timber is cut lengthwise in the direction of the grain, except when the log was warped, the grenade. Place of growth of branches they are marked by knots, and the twists and turns of the fibers.
If the cut lumber is much wider than the thickness, up to a thickness of 40 mm is called a board, and above that thickness crowd. If the timber has a square cross-section, regular polygonal or rectangular then up to 10x10 dimensions is called a batten, and above those dimensions are beams. If the cross section has a more complex form, such as, for example, prepared materi-frame for pictures, then it is called a profiled batten.
Lumber that is not sawn on the sides has at least one unprocessed side and as such cannot be grazed hkind of next to each other. It is planed, however, after scraping smooth, and has smooth surfaces, without cracks.
In practice, veneers, plywood and the latest: panel boards and veneered boards. often spe-boards are wrongly called veneer! Usually the veneer is made by the peeling of large trees, which turn, about the same as when the rolled canvas is unrolled. Sawed veneer se obtained by cutting board after board along the tree, and the veneer peeled with a knife, by cutting the plates with a knife transversely on the length of the tree. The thickness of the plates varies between 0,6-1,2 mm. Veneer without damage, without knots, with a nice texture is a veneer for covering the "face", and less beautiful, possibly damaged and continuous, glued, is the veneer for the reverse side. External, visible bythe top of most furniture is covered with veneer, while another type of veneer is used, for example, for the back furniture.
Spruce boards are made by gluing several dry fursnir plates on top of each other. If the mutual directions arehenna normal or diagonal, strength and weight per several times exceed the strength and weight of a board of the same thickness. Thickness plate according to the number of layers is: 3-5 mm for three-layer, 6-8 mm for five-layer and 9-12 mm for six-layer.
Veneer and plywood are made only from hardwood and therefore they are heavier than boards of similar thickness. Their weight increases and because of the glue.
Panel-boards are made from slats of soft wood glued between two veneer or plywood boards, which increases thickness, a hard and beautiful surface is obtained, and weight and strength they are slightly larger than soft wood boards of the same thickness. U in the furniture industry, panel boards have found wide application.
Clad boards are wooden boards (plywood, panel boards, chipboards, hard fiber boards etc.) covered with plastic boards masses. They have one or both sides smooth, shiny and optional painted (imitation of wooden board, etc.). They're not exactly cheap, though are due to their strength, appearance and easy surface cleaning wide application.
Hard fiber boards (fiber boards) are made from crushed hemp fibers or softwood shavings mixed with artificial resin, which after thermal processing is pressed under high pressure into plates. Specific their weight is high and with hard boards it can reach i 150% of the specific gravity of water. These plates are often called artificial plates.
And finally, this group of plates also includes hollow plates made of a lattice construction of softwood slats, covered with plates. Since they cannot be cut, from these plates only certain elements are made, such as, for example, doors.

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