If no preliminary operations are required when driving in nails, preparatory work must be carried out before screwing in the screws. A hole is first made in the workpiece with a size of 2/3 of the diameter and 1/2 of the length of the screw. A screw is inserted into this hole, which is easily screwed in the desired direction, without splitting the wood. For small screws, the hole can be made with a nail.
The point of the screw must be straight and pointed, and the slot in the head must be worn. The screw can be screwed into the wood better if it is covered with a thin layer of soap. To prevent the tip of the screw from coming out on the other side of the parts to be joined, its length should not exceed their total thickness. Rusted screws should not be used, but if others are not at hand, the screw should be covered with a layer of oil.
To connect wooden parts, in addition to screws and nails, adhesives are widely used.
Of the warm (heated) adhesives, bone and flesh adhesives are the best, which are diluted in water in a 1: 3 ratio. These adhesives are marketed in the form of tiles. The surface of the adhesive tile must be free of oil and paint stains, cavities and cracks.
The glue is diluted immediately before use. Most often, pieces of glue are soaked in water for about 6 hours. During this time, harmful impurities such as fats and oils will float in the water. When the glue softens, the excess water is drained and heated to a temperature of 55-60 ° C. It is best to place a jar of glue in a dish filled with water and heat it, and it is necessary to ensure that the heating temperature does not exceed 70 ° C. Stir the glue constantly until it is completely dissolved. The glue applied to the glued surfaces dries up after 5-25 minutes (even sooner in a warm place), so it should be used immediately after preparation.
Cold (unheated) glue, such as casein glue, dries more slowly, but metal surfaces rust from it. In addition, cold glue changes the color of wood products that contain tannic acid. The advantage of cold glue is that it has good waterproofing properties and does not require heating before use.
The cold glue is dissolved in water with the addition of alkali with constant stirring (1 kg of glue dissolves in 1.5-2 liters in about 30 minutes). The air temperature in the room must be at least 10-20 ° С.
When stirring, the cold glue quickly thickens, but after a while it again acquires the necessary consistency, so there is no need to rush to pour water into it. Apply 50 g of cold glue in a uniform layer on 1 m2 of surface. Well mixed cold glue can be used even 5 hours after preparation.
Among the adhesives based on synthetic resins, epoxy is widely used. It is used for glued joints requiring special strength. At room temperature, epoxy glue dries in 24 hours.
The general rules for gluing are as follows: surfaces completely cleaned from the remnants of old glue or paint must be precisely adjusted, the glue must be applied evenly over the entire gluing area, the parts to be glued must be pressed tightly against each other, and then the product must be thoroughly cleaned of the squeezed glue. After that, it is necessary to put bars or strips on the parts to be glued and fix the clamping devices on them..
Thanks to such gaskets, the product will not be damaged and the crimp will cover the entire area of the glued surface.
Sawing is one of the most important operations when working with wood. Sawing is done with various saws (Fig. 1). A frame (bow) saw is used for sawing large-sized boards and bars, for arcuate cuts – a hacksaw or a cut (narrow knife) saw. In addition to these saws for a home workshop, you must also purchase a small-sized hand-held frame saw with a steel frame and a set of interchangeable hacksaw blades. Hacksaw blades must have different tooth sizes, sharpened at different angles. For work, it is more convenient to use a saw with teeth sharpened at an angle of 90 ° (such teeth can be easily sharpened with a triangular file). You must also have a hacksaw blade with 110 ° teeth. The hand-held frame saw can be used to attach a hacksaw blade for cutting metal.
The saw teeth must be set correctly. The degree to which the teeth are set depends on the precision with which the cut needs to be made. Toothed set prevents the saw blade from getting stuck in the wood being cut. The teeth are separated with adjustable pliers (an experienced craftsman can use pliers for this). It is difficult to make a saw with a saw with the correct set of teeth, therefore, first a notch is applied to the workpiece with a chisel or other cutting tool, and then the workpiece is sawn through this notch.
If the saw teeth are dull, they are sharpened with a triangular file, holding the saw blade in a vice. The saw blade should protrude no more than 0.5 cm above the vise jaws.
The saw blade on frame saws is tightened by twisting the connecting cord with a peg, on metal frame saws – tightening the wing nut.
The saw blade can be tilted to one side or the other from the plane of the frame. Even when making a straight cut, the saw must be tilted about 30 ° to the right in order to see the direction of movement of the saw blade. It is also necessary to ensure that the saw blade is not twisted, i.e. it must have the same angle of inclination at both ends..
Before starting sawing, the workpiece must be marked out. To indicate the direction of the cut, use a square made of hard wood or steel. With its help, a marking line is applied to the workpiece, then the square is turned 180 ° and another line is drawn. If the lines do not coincide or are not parallel, then the correct cutting line is drawn in the middle of these lines.
The workpiece to be sawn must be held to the left of the marking line with your left hand so that your thumb can guide the movement of the saw blade (Fig. 2, a). The finger should rest 1.5 cm above the saw blade to avoid injury if the saw blade jumps out of the cut.
When sawing, the saw stroke should be as long as possible so that the teeth enter the wood along the entire length of the blade. The saw must be moved evenly, without jerking and swinging from side to side or from top to bottom (Fig. 2, b). Make sure that the saw blade does not deviate from the marking line. The workpiece can be firmly clamped in a vice or on a joiner’s workbench, but so that the sawn end is not too long (Fig. 2, c).
In damp wood, a low-set saw often gets stuck. This can be avoided by coating the saw blade with a layer of soap or oil. It is necessary to monitor the moment when the sawing ends. At the end of sawing, the saw stroke should be short without excessive pressure, so that the edge of the sawn piece of workpiece does not split.
After finishing work, the saw with a steel frame, cleaned of sawdust, is coated with oil so that it does not rust, and the saw blade is turned with the teeth inward.
CHILLING IN WOOD
When making furniture, inserting a lock, replacing door hinges, you cannot do without chiselling. As with any work, chiselling requires certain skills and is performed with a special tool – a chisel. For carpentry work, the following types of chisels are most often used: chisel with rectangular edges, wide chisel with cut edges, carpentry hollow chisel, narrow spike chisel (chisel).
The metal part of the chisel is made of steel, its handle and hammer for chiseling are made of wood. To make the handle of the chisel strong enough to withstand hammer blows, an iron ring is stuffed at its end. The main part of the bit is the cutting edge, which is usually sharpened at an angle of 25 ° (Fig. 3, a).
The bottom uncut side of the bit is always straight (only on hollow bits it is rounded). When chiseling, the straight side of the bit faces the workpiece, and the cut-off sharpened edge – towards the cut-off part of the workpiece (Fig. 3d). When chiselling, the direction of the grain and the structure of the wood must be taken into account. For example, if you hammer in the direction of the wood grain, then if the impact is too strong, the product can split (Fig. 3, e).
When gouging a groove or socket, the chisel is first directed perpendicular to the fibers (Fig. 3, b), and then along the direction of the fibers, chipping off the wood layer by layer (Fig. 3, c). Do not forget that the support on which the workpiece rests must be stable and not springy upon impact. The wood is chopped off in thin layers. The chisel must be firmly held, tightly grasping the handle with the whole hand.
Narrow deep grooves and sockets are made with a chisel. Through grooves are hammered from both sides of the board (Fig. 3, e). Hollow chisels hollow out grooves and nests of round and oval shape, and also round off the edges of the product.