How and with what to cut a board, timber, or slats lengthwise, why is it difficult to cut wood lengthwise? Sawing techniques with hand saws Cross cutting of wood.

• " onclick="window.open(this.href," win2 return false >Print
• Email

Sawing with a carpenter's hacksaw

Sawing is one of the most critical operations in the wood processing process. The quality of manufacturing of parts and wood savings largely depend on the quality of its execution. By correctly performing the sawing, you can reduce the allowances for subsequent planing and the time for manufacturing the part.

Hand saws are divided into tension saws with a thin saw blade and loose saw blades with a loose, thicker blade. Tensioned saws include all bow saws, and for saws with a free blade - hacksaws.

Below you can watch a fragment of a film about making hand saws and hacksaws. Full version the film can be downloaded.

According to the direction of cutting the fibers, they are distinguished transverse, longitudinal and mixed Sawing
At transverse sawing the direction of the cut (cut) is perpendicular to the fibers.
At longitudinal sawing - parallel to the fibers. At mixed sawing - directed at an angle towards them.

Cutting element any saw is tape with teeth cut into it. Each tooth represents cutter. Saw teeth are also characterized step and height: height- the shortest distance between the base and the top of the tooth; step- the distance between the tops of adjacent teeth.
For cross cutting For workpieces, saws are used whose teeth have straight triangular profile, and for rip sawing - saws with inclined profile teeth

Hand saws are available with fine and coarse teeth.

Have saws for transverse sawing, the sharp cutting edges of the tops of the teeth alternately cut the wood fibers and remove the broken wood particles in the form of sawdust.
Have saws for longitudinal sawing, the cutting edges of inclined teeth protruding forward cut off the wood fibers and the cut particles are chipped along the fibers, forming sawdust. The figures below show the shapes of the teeth and the patterns for cutting fibers with longitudinal and transverse saws.

Technical characteristics of saw teeth

Purpose of sawing tools

When sawing, the saw blade rubs against the walls of the separated parts of the wood. And so that it does not get pinched in the cut, the saw teeth must be divorced(set of teeth), i.e., alternately bent in different directions. This makes the cut a little wider and makes sawing easier. Below is the views wiring for spreading the teeth.
There are wiring different forms. In the picture below on the left( A) shows the main types of wiring. On the image b And V- shows correctly set teeth for transverse ( b) and longitudinal sawing ( V).

When sawing workpieces, retreat from the marking line by 2-3 mm.

The hacksaw blade should move at right angles to the workpiece.

Sawing control carried out along the marking line. It should remain to the left of the sawing point on the workpiece.

For more precise sawing of wood or plywood blanks, saws with fine teeth are used. The inclination of the saw is shown in the figure.

This is how they work with a hacksaw. The marked workpiece is placed on a board (1) on a carpentry bench that has a stop (2). With your left hand you press the workpiece against the stop, and with your right hand you make a cut. In this case, the hacksaw is pressed against the stop and several short smooth movements are made towards you. After sawing, the hacksaw is moved along its entire length, aligning it with the marking line of the cut.

By moving the saw along the line, an incision is made, then the block is removed and the part is sawed off. At the end of sawing, the pressure on the saw is eased so as not to break off the wood fibers at the exit of the saw. The position of the hands when sawing is shown in the figure.

For precise sawing of bars and boards at angles of 90°, 45°, 60° and others, they are used miter box . Miter box has a grooved shape. It consists of a bottom 1, two sidewalls 2, between which the workpiece to be cut 3 is clamped. The sidewalls have cuts made at the desired angle. Saw blade 4 is inserted into these cuts and sawing is performed at the desired angle.

Application miter box eliminates part marking, increases cutting accuracy, reduces time spent on part marking, thus increasing labor productivity. The use of a miter box is especially effective in mass production details. The miter box may look like the one shown in the photo.

For ease of sawing, they also use tsulagu. Tsulaga very quickly made from a sheet of plywood or board and two bars. Thanks to the lower bar, it is easy to press it to the tabletop, and the upper one serves to support the workpiece. Tsulaga can be made with a movable sawing stop large quantity identical parts.

Sawing techniques using tsulagu, miter box, stops, are shown in the figures.

For sawing different workpieces and figure cutting, different saws and hacksaws are used. Examples are given in the figure.

Securely secure the workpiece when sawing.
Use stops, miter boxes and other devices.
Sawing only with a serviceable, sharply sharpened saw.
Do not allow the saw to skew when sawing.
Do not make sudden movements with the saw.
Do not keep left hand close to the saw blade.
Place the saw on the workbench with the teeth facing away from you.
Do not blow away sawdust or sweep it away by hand. Use only a brush.

Lecture 11

Sawing wood. General information

1. Characteristics of the sawing process

Sawing is the process of dividing wood with a saw into volumetric, undeformed parts by turning the volume of wood between these parts into chips.

A saw is a multi-blade cutting tool that works in a closed cut. A kerf is a gap formed in wood when teeth cut narrow shavings (sawdust). The cut has side walls and a bottom with which the blades (teeth) interact.

2. Classification of types of sawing

Sawing wood is classified according to several criteria.

Depending on the position of the saw plane in relation to the wood fibers, longitudinal, transverse and mixed sawing is distinguished.

For longitudinal sawing The plane of the saw is parallel or approximately parallel to the grain of the wood. Saw frames, circular saws and band saws operate on the principle of longitudinal sawing, on which logs and beams are sawed into boards, lumber is cut to width or thickness in the longitudinal direction.

When cross cutting the plane of the saw is perpendicular or approximately perpendicular to the grain of the wood. Sawing is performed manually with cross-cut saws, hacksaws or on cross-cutting machines used for cutting logs into round logs, removing wood defects and wane areas from the ends of the lumber, as well as giving the lumber a given length and quality.

For mixed sawing the saw plane is located at an acute angle (10˚...80˚) to the direction of the fibers.

Depending on the type of saws used, there are different the following types sawing:

– longitudinal frame sawing, sawing with band, circular and jigsaws;

– cross-cutting with circular, chain and jigsaws;

– mixed sawing with circular, band and jigsaws.

Depending on the number of simultaneously working saws in the machine, a distinction is made between individual and group cutting methods. Cutting logs and lumber with one saw is called individual cutting, and cutting with several saws is called group cutting.

For individual sawing logs are sawn into lumber with separate cuts on circular saws, band saws, vertical or horizontal machines. The cutting is carried out taking into account individual characteristics quality zones of each log. This cutting method is effective when sawing valuable wood, cutting large-diameter logs and logs with significant defects.

For group sawing sawmill frames, multi-saw circular saws and band saws, as well as milling and sawing machines are used.

Depending on the position of the workpiece relative to the center of the circular saw, sawing with the peripheral zone of the saw, the middle zone and the central zone of the saw, as well as sawing with the upper and lower zone of the saw are distinguished.

When working in the peripheral zone saws, the teeth of the saw protrude above the surface of the workpiece by an amount approximately equal to the height of the tooth.

When working in the middle zone saw teeth protrude above the surface of the workpiece by an amount equal to approximately one third of the radius of the saw.

When working in the central zone The center of the saw is located at the middle of the cutting height. This type of sawing is used in milling and sawing machines.

The peripheral and middle working zones of the saw can be located on the upper or lower sections of the saw, which is observed in circular saws with a lower and upper saw shaft.

When cutting logs into lumber, the following methods are used (Fig. 1):

– log collapse;

– beam collapse;

– sawing with beams into one or two beams;

– cutting out asymmetrical timber (sleepers);

– camber-segment and beam-segment;

– circular;

– sectoral.

When sawing logs waddle On sawmill frames or multi-rip circular saws, unedged boards and slabs are formed in one pass. This sawing method is often used when cutting hardwood logs.

When sawing with lumber The log is sawn in two passes. On the first pass, one or two double-edged beams, unedged boards and two slabs are obtained from the log. On the second pass, the beam is collapsed and edged boards with a width equal to the thickness of the beam, unedged boards and two slabs are obtained. In this case, the boards cut from the middle part of the timber are radial. Boards cut from the peripheral zones of the timber are tangential. The remaining boards occupy an intermediate position.

With the split-segment cutting method, on the first pass from middle zone The logs are cut into several unedged boards, and two segments are obtained from the side zone.

With the circular method of sawing logs, each subsequent cut can be directed parallel, perpendicular or at any angle to the previous one. This makes it possible to obtain radial and tangential sawn timber. The log can be sawed parallel to its longitudinal axis or parallel to its generatrix. The circular method is especially effective when cutting large-sized raw materials.

With the sector sawing method, the log is first sawed along the axis of the log into parts that have the shape of sectors in cross section. Then one block is cut from each sector, the face of which is parallel or perpendicular to the radius of the log. If the annual layers of wood are located to the face at an angle of less than 45˚, then tangential sawing lumber is obtained; at an angle of more than 45˚, but less than 60˚, mixed sawing lumber is obtained, and at an angle of more than 60˚, radial sawing is obtained.

3. Widening the cut

When sawing, the side cutting edges of the teeth deform the walls of the cut. After the teeth pass, the walls of the cut are elastically restored, the distance between them is reduced, and the saw blade can be clamped. Due to friction, the saw becomes so hot that it becomes impossible to work with it, it loses stability.

To prevent the saw from clamping, its serrated edge is widened. The width of the cut should always be greater than the thickness of the saw blade. If this condition is not met, then the walls of the cut clamp the saw.

The widening of the cut is carried out by setting or flattening the teeth, or using saws with a lateral undercut, or the saws are equipped with plates made of hard alloys, the teeth of which are sharpened with a lateral undercut.

At divorce (Fig. 2, A) the tips of the teeth with a length of 0.3...0.5 of the tooth height are bent alternately in different directions. At flattening (Fig. 2, b) the tips of the teeth are flattened and shaped, giving them the shape of blades located symmetrically relative to the saw body.

Round planing saws (Fig. 2, V), have a lateral undercut at an angle of 15¢ and 25¢.

Saw teeth with carbide inserts (Fig. 2, G) have the shape of spatulas with a lateral undercut.

The cutting width in this case is found as follows:

Where b– cutting width, mm;

S– saw blade thickness, mm;

S’ – widening of teeth on each side, mm.

Values S’ it is recommended to use the reference book in the range of 0.2...1.1 mm. Its value depends on the type of wood (density), humidity and working conditions.

4. Specific friction force

A kerf is a narrow gap formed by a saw. Cutting chip width b falls into the cut width b P.

Due to the elasticity of wood, the walls of the cut are partially restored after the passage of the tooth. Kerf width b P< b. Thus, the chips are clamped from the sides by the walls of the cut (Fig. 3).

With further movement of the tooth, the chips overcome frictional forces F t along the walls of the cut and the front surface of the tooth, is pressed into the interdental cavity, gradually filling it. The longer the path of the tooth in the wood, the more chips accumulate in the cavity, the more it is compressed and rubs against the walls of the cut.

Average friction force per tooth passage in the workpiece

where a is the tangential pressure on the tooth from the friction of the chips in the cut (specific friction force of the chips on the walls of the cut), MPa.

The specific friction force of the chips in the cut is equal to the ratio of the average friction force to the cross section of the cut layer:

. (2)

The values ​​of a for saws with set teeth al and flattened teeth aD are found from (Table 1).

Table 1

Tangential pressure a on the saw tooth due to chip friction in the cut

The specific friction force is the tangential pressure of the chips on the tooth, created by the friction forces in the cut.

5. Saw performance in terms of cavity capacity

Sawing performance is characterized by the amount of feed per tooth, determined by the capacity of the interdental cavity.

The sawdust formed during sawing is placed between the teeth and removed from the cut.

Based on numerous studies of cutting theory, the following formulas are recommended for calculating the feed per tooth by filling the cavities with sawdust:

when sawing with frame saws

; (3)

when sawing with band saws

when sawing with circular saws

Where t max – maximum cutting height.

6. Thickness of the cut layer when working with flattened and set teeth

In Fig. 4 shows three cuts of the same width b, in which layers of wood are cut at the same feed per tooth S z. The first cut shows the set teeth of the saw, and the second cut shows the shapes of the layers cut by these teeth. The third cut shows the shape of the layers being cut by flattened teeth. The areas of the layers cut by set and flattened teeth are the same and equal bS z. Average feed per tooth along the length of the cutting edge found by dividing the cut area by the length of the cutting edge bl:

.

Usually taken

, (6)

where m is the feed angle (the angle between the directions of the feed and main movement speeds).

7. Saw tooth shape for longitudinal and cross cutting

The sawing rule can be formulated as follows: when inserting a tooth into wood, you first need to cut the fibers, and then, with the least resistance, separate them from the massif and remove the chips from the cut.

For longitudinal sawing (Fig. 5, A) the tooth with its main cutting edge cuts into the wood and cuts its fibers. The wedge of the tooth penetrates the wood and the front edge tends to press the cut chips away from the wood. Since the strength of the wood in the plane of the fibers is weak, the cut part of the chips breaks off and falls into the interdental cavity.

The saw tooth must have a cutting angle at the main cutting edge that is always less than 90°. The side cutting edges are not sharpened and are left with a cutting angle of 90°.

When cross cutting (Fig. 5, b) the work of cutting wood fibers is performed by the side cutting edges. For this purpose, the teeth are made with side sharpening. When teeth are inserted into wood to a depth of 0.8 mm, stresses at the bottom of the cut created by the beveled front edges of the teeth (Fig. 5, V), reach the limit of shear strength along the fibers and the cut fibers split either to the left or to the right along the fibers.

When cross-cutting wood, the main work is performed by the side cutting edges of the teeth, inclined forward and having beveled front edges. To ensure these conditions, the saw teeth are sharpened as follows: cutting angle at the main cutting edge d > 90 ° , and the side cutting edge is made with an oblique sharpening anglej = 40...45 ° .

Test questions and assignments

Please indicate the number of the correct answer.

1. When sawing wood circular saw, in which the thickness of the disk is 2 mm and the widening of the teeth on the side is 0.6 mm, the cutting width is equal, mm

2. Widening of saw teeth is achieved by

1) divorce,

2) flattening,

3) use of saws with side undercut,

4) soldering of plates followed by oblique sharpening,

5) increasing the thickness of the saw.

3. What is the difference between rip and cross saws?

4. How to take into account the friction of the saw in the cut in the calculations?

5. What cutting methods do you know?

As you know, sawing is one of the variations of the wood cutting process, as a result of which the workpiece is divided into parts. In this case, part of the workpiece turns into waste - shavings or sawdust. Sawing is carried out with a special cutting tool - saws, which work in a closed cut.

A kerf is a gap formed in wood when narrow shavings and sawdust are cut by the teeth of a cutting tool. At the cut, we can identify several parameters with which the teeth of the cutting tool interact, such as the side walls and bottom. Also, the width of the cut, which determines the amount of wood material sent to waste, which in turn is determined by the size of the cutting part of the tool.

Due to the characteristics of the structure of the wood material, sawing directed along the grain, sawing across the grain and mixed sawing are distinguished.

Sawing in the direction along the grain of the wood is called “longitudinal”. When longitudinally sawing wood, the main cutting edge of the cutter, which is one saw tooth, performs end or longitudinal end cutting. The side edges of the saw tooth produce transverse or longitudinal-transverse cutting. An example of longitudinal sawing is cutting a carriage into boards on a multi-rip machine, sawing a log into unedged boards on a band saw, or trimming the edge of an unedged board on a specialized edging machine.

Sawing in a direction across the grain of the wood is called cross-cutting. When cross-cutting wood, the main cutting edge of the saw tooth cuts across the grain, and the side edges at the end. An example of cross-cutting is the operation of “trimming” workpieces, carried out on cross-cutting machines.

In the case of mixed cutting or cutting at an angle to the direction of the wood fibers, the main cutting edge of the saw tooth produces a face-transverse or face-transverse-longitudinal cutting. The side edges of the saw tooth produce transverse end cutting.

Sawing when cutting different wood materials such as plywood, particleboard or fibreboard will always be mixed. This is due to the multidirectional orientation of the fibers that make up the board along the thickness of the treatment.

Sawing tools - Saws.

Sawing wood is usually done with a special sawing tool, i.e. saws. A saw is a cutting tool equipped with many cutters mounted on the saw blade one after the other. Saws come in several different types - frame, band, chain and disk.

Frame saws are a final, relatively rigid blade with cutter teeth installed on one side. An example of a frame saw - a two-handed saw for home use. Sawing with frame saws is carried out with a straight-return motion of the saw blade.

Band saws are similar in structure to frame saws. The difference is that the band saw body is narrower and more flexible and can be welded into a ring. This creates a tool with an endless row of cutter teeth, the sawing of which is carried out due to continuous rotation in one direction.

Chain saws are similar in operating principle to band saws, although their design, of course, is radically different. This is an endless rotating sequence of teeth mounted on a special carrier - a chain.

And finally - circular saws. In a tool of this type, the teeth-cutters are located along outside disk, usually steel. The diameters of blades for saws of this type can be very different, which, in combination with the combination of the number of teeth themselves, makes it possible to use them in the most various areas applications.

Some common features of saws.

The design of the above types of saws will be described in separate articles on our website; here I will only touch on some general points. The area of ​​the saw where the teeth are installed is called the “ring gear”. The saw tooth profile can be straight sharpened, used for longitudinal sawing, with oblique sharpening, for transverse sawing, more complex profiles are also used, as well as their combinations.

When sawing, the side cutting edges of the saw teeth exert pressure on the walls of the cut. After the saw teeth pass, the walls of the cut are partially restored, the distance between them is reduced, which can lead to the saw blade being pinched in the cut. When the saw rubs against the walls of the cut, the load on the mechanisms that drive the saw increases, and the saw can heat up to the point of losing stability.

To ensure free movement of the saw blade during sawing and to eliminate power loss from friction of the side walls of the cut on the saw blade, it is necessary that the width of the cut exceed the thickness of the saw blade. One of the ways to ensure this condition was the so-called “set apart” of the saw teeth, i.e. alternating bending of the teeth outward. If soldered carbide plates are used as saw cutters, their size must exceed the thickness of the saw body.

An important characteristic of any type of saw is the “capacity of the interdental cavity”. Sawing productivity is characterized by the amount of feed per tooth, determined precisely by the capacity of the interdental cavity, filled with sawdust formed during sawing. There are recommendations created on the basis of numerous studies for calculating the feed per tooth by filling the cavities with sawdust, and we will talk about them when describing the features of sawing with specific types of saws.

Some features of sawing.

Sawing can be carried out according to an individual or group plan. With individual sawing, the original wood material is sawed with one saw and separate cuts, which makes it possible to take into account its individual characteristics.

Individual sawing is typical for processing on circular saws, bandsaws, vertical or horizontal machines and is effective when sawing valuable wood, cutting large-diameter logs and logs with significant defects.

In other cases, group sawing is possible; saw frames, multi-saw circular saws and band saws, as well as milling and sawing machines are used for this.

The processes of sawing wood materials is a complex physical and mechanical process of destruction of not only the material being processed, but also the cutting tool itself, under the influence of escaping chips and the cutting surface on the working edges of the tool.

The complexity of the cutting process is determined by the variability of the properties of wood and wood materials, changes in the cutting ability of the cutter due to a violation of the geometry of the blade, a variety of technological factors and their complex relationships. We will talk about this more in future articles.

Saws and sawing. Saws are made of high quality steel with cut teeth. For carpentry and joinery work, use a wide hacksaw, a hacksaw with a butt, or a narrow hacksaw; a saw with a cutting depth limiter (reward), a bow saw, and also a plywood file (knife) (Fig. 1).

A wide hacksaw is made from a steel strip 0.7 m long, 11 cm wide at the handle and 2...7 cm at the narrow end. The handle can be wooden, metal or plastic. A narrow hacksaw is used for cutting curved through holes in large-width parts. The jigsaw (Fig. 2) has a narrow and thin (0.3 mm thick, 1...2 mm wide) file with fine teeth. The file is fixed in an arched frame and can be easily removed. Thin parts (plywood) of a curved shape are cut out with a jigsaw. Before starting work, the end of the file is inserted into a pre-made hole, and the other end is secured in the frame. Sawing is carried out according to the markings. At the end of the work, release the end of the file and remove it from the hole in the part.

Hacksaws with a back are used for shallow sawing, for example, sawing grooves in wide workpieces, for fitting parts during their assembly. The top of the canvas is reinforced with a steel backing, which increases the rigidity of the canvas. The fine teeth are shaped isosceles triangle. Use a hacksaw to cut in both directions (Fig. 1, c).

Based on the shape of the teeth, saws for longitudinal, mixed and cross-cutting are distinguished (Fig. 3).

For sawing along the grain, saws with oblique teeth are used. They cut wood in one direction - away from themselves. The cavity between the teeth is called the sinus. The tooth pitch is the distance between the tips of adjacent teeth. The height of a tooth is equal to a perpendicular drawn from the top of the tooth to its base. There are three edges in the saw tooth (Fig. 3, a). In rip saws, the cutting is performed by a short cutting part - the front edge, and the side edge only separates the wood fibers.

Rice. 1. : a - wide hacksaw: b - the same, narrow; c - axing hacksaw; g - reward; d - plywood saw.
Rice. 2. Jigsaw.	Rice. 3. : a - saw elements; b - saw tooth angles; I - for longitudinal sawing; II - for mixed sawing; III - for cross cutting: 1 - side cutting edges; 2 - front edge; 3 - front cutting edge; 4 - step; 5 - top; 6 - sinus; 7 - height; 8 - line of the base of the teeth.

A bow saw is used for longitudinal and cross cutting. It consists of a beam frame with a tensioned saw blade. The latter is made of steel strip about 1 m long, 45...60 wide and 0.4...0.7 mm thick. The pitch of the teeth is 4...5 mm, the height of the teeth is 5...6 mm. The ends of the saw blade are fixed at the bottom of the beam frame posts. The canvas is stretched with a string of twine secured between the upper ends of the posts and twists. The saw blade is rotated using handles. This saw can be operated by one person. The cut is smooth and even. The teeth of crosscut saws cut the fibers, the side edges of the teeth, and the leading edge only separates them. In rip saws, the leading edge of the tooth cuts the wood. This is taken into account when determining the sharpening angles of saw teeth for transverse and longitudinal sawing.

Rice. 4. Sawing along the grain with a bow saw if the material is in horizontal position: to the right - the position of the worker’s feet while sawing.
Rice. 5. Stands: a - wooden with a movable support: b - metal with a roller; c - wooden with a roller.	Rice. 6. Sawing with a bow saw along the grain while vertically securing the material: a - the position of the worker’s hands during sawing; b - the same, feet.	Rice. 7. Cross cutting: a - sawing techniques; b - supporting the sawn part with your hand at the end of sawing.

In saws for longitudinal sawing of soft wood, the sharpening angle is 40...45°, in saws for hard wood - up to 70°, in cross-cut saws, the angle between the cutting edges of the teeth is 60...70°, and the sharpening angle is 45... 80°. Saws for mixed sawing have a sharpening angle of 50… 60°. The angles of the saw teeth are as follows: for longitudinal sawing - 60...80°, for transverse sawing - 90 -120°, for mixed sawing - 90°. For sawing shallow grooves and sockets of tenon joints, the so-called reward is used. To regulate the cutting depth, it has a movable stop. Saw blade thickness 0.4…0.7 mm, length -100…120 mm.

Types and techniques of sawing. According to the type of fastening of the part in the workbench, they are distinguished: horizontal sawing along the grain, vertical sawing along the grain, horizontal sawing across the grain and sawing at an angle. When sawing horizontally along the grain, the workpiece is secured by pressing it against the table with clamps (Fig. 4) so ​​that the sawn part protrudes beyond the edge of the workbench. In this case, the worker’s body should be slightly tilted forward, and the saw should be held vertically. First, they make a cut, moving the saw up several times, after the cut becomes deep, they begin sawing, moving the saw up and down. A wedge inserted into the cut prevents the saw blade from jamming.

When vertical sawing along the grain, the workpiece is secured in the workbench with a front or rear clamp (Fig. 6). The figure shows the position of the worker's legs during the sawing process. When sawing a thin board, it is clamped so that it does not bend, lifting it upward as it is sawed. Sawing begins with a cut, after which they work to the full swing of the saw blade, without pressing on it. Short workpieces are sawed starting from one end, and then, turning the workpiece over, from the other. Sawing long boards (along the grain) is carried out by resting their ends on stands (see Fig. 5).

Rice. 8. : a - correct; b - incorrect (cutting angle is too large); c - splintered cut, due to improper sawing, flakes and damage to the edges are possible; d - sawing along the fibers with a hacksaw; d - sawing with a bow saw using a template (miter box); e - sawing with a narrow hacksaw through drilled holes; g - template for trimming the ends of boards placed in bags; 1 and 2 - side posts - guides for the saw; 3 - board attached to the racks; 4 - fastening nail of the auxiliary device; detail A - the position of the hand on the frame of the bow saw during sawing.

When sawing the workpiece across the grain, the sawn end is pushed beyond the edge of the workbench (Fig. 7). Before starting sawing, make a gash; during the sawing process, monitor the position and inclination of the saw blade and ensure that the cut is straight and the sawn surface is flat.

To avoid flakes, the sawn part of the workpiece (Fig. 7, b) should be supported by hand at the end of sawing. For tenon joints or other parts that require mating at an angle of 45 or 90°, use a template (miter box) (Fig. 8, e). With repeated use, the cuts on the wall of the miter box may become excessively wide and it will not give the exact size of the angle. To extend the durability of the miter box, its side walls are made of hardwood boards. To trim boards (one width), use a special template (Fig. 8, jar). The side posts of the template serve as guides for the saw; they are made of hard wood. For boards of a certain width, a custom template is required. Sawing wood by hand is acceptable for small volumes of work.

Sawing wood

Sawing is the process of cutting wood into pieces with the formation of a gap between them - the so-called kerf. The wood is divided into pieces using special multi-cutting tools - hand and mechanized saws. The saw has the form of a tape, blade or disk with teeth (cutters) cut on their edges.

Hand saws include two-handed saws, bow saws, hacksaws (wide and narrow), axle saws, bore saws and jigsaws.

Two-handed saws are used for rough sawing of timber and lumber across the grain (previously, special two-handed saws were also used for longitudinal cutting). Bow saws with different blades are used for sawing material across, along and at an angle to the wood fibers, sawing down tenons and eyes, sawing off ends “on a miter”, and accurately trimming bars. Wide hacksaws are used for sawing wide boards across the grain, sawing tenons and lugs, narrow ones are used for sawing thin lumber, cutting curved parts and making through cuts. A hacksaw with an edge is used for sawing small parts, precise trimming, shallow cuts, and miter cuts. The reinforcement is used mainly for sawing grooves and slits to a certain depth. A special award, the small teeth of which are located along a curved convex line, is used for cutting veneer. Jigsaws different sizes used for sawing out small parts from thin planks, plywood, bone and other materials, as well as for cutting out holes in the central part of a board or shield.

When sawing wood hand saws the canvas performs reciprocating rectilinear movements when the workpiece is stationary, and the teeth cut off shavings (sawdust) and remove them from the closed cut. As a result of sawing, flat or curved side surfaces and bottom are formed.

Depending on the profile and sharpening angles of the saw teeth, saws are intended for transverse (across the grain), longitudinal (along the grain) and mixed (universal tools) sawing.

Two people work with a two-handed crosscut saw. The wood is placed on a stand (table, sawhorse), the cut location is marked, and then a saw is installed at this location. You need to start cutting with the middle of the saw, and when the middle teeth go deeper into the wood, gradually increase the span of the saw to its entire length. When sawing, do not press the saw too hard, otherwise it may get stuck in the cut.

A bow saw is one of the main cutting tools of a carpenter. It consists of a glass (beam) and a thin saw blade fixed in it. The tension of the canvas is carried out using a bowstring and a strip or with a wire with a thread at the end, into which a wing nut is screwed. To avoid bending of the saw posts, the required blade tension is set immediately before work, and after the operation is completed, it is loosened again. In order to better monitor the cutting location and ensure the ability to make long cuts, it is advisable to rotate the tool blade before tensioning it by 30–40° relative to the machine. The saw blade should be straight, without distortion and well tensioned.

They saw slowly, but with confident movements; If you rush, the cut will turn out uneven. Sawing is carried out according to the markings with allowance for subsequent processing. The main thing when cutting is to follow the marking lines as accurately as possible.

The greatest resistance to working with a saw is created by the friction of the sidewalls of the blade against the walls of the cut. The thicker the workpiece, the narrower the canvas should be taken or the larger the spread it should have. If there is no canvas freewheel in the cut, it is difficult to control and the saw moves to the side. Very thick workpieces are sawn in a circle according to precise markings. When cutting lengthwise, at the slightest pressure, spacer wedges should be inserted into the cut. The accuracy of the cutting line depends on the evenness of the line of the teeth, the uniformity of their spread and sharpness.

When moving towards itself, the saw goes a little deeper into the wood, but it doesn’t jump to the side and it’s easy to hold the blade with your joint thumb or fingernail in place. When moving away from itself, the saw cuts into the wood, but can move to the side due to buckling forces. Therefore, to make an accurate cut, you should start sawing by moving towards yourself, repeating it as many times as necessary to mark a clear and precise cutting line, and only then start sawing. If you start sawing away from you, you may not follow the markings exactly or break off an edge of the workpiece. It is also necessary to monitor the accuracy of the start of sawing because with an accurate rectangular cut there will be significantly less trimming work.

It must be remembered that the thinner the part, the finer the saw teeth should be. Therefore, for sawing small glazing beads or strips, we can recommend a slotted metal saw, but work with it in a miter box - a special tray that is used for sawing lumber at the desired angle. When sawing thin laminated plywood, the hacksaw should be held with a minimum inclination to the surface of the sheet and force should be applied only when moving towards you. The movement from oneself must be idle. This technique eliminates flakes and the saw jumping off the intended line.

The edges of plywood or blockboard will not chip when cutting across the jacket layer if the cut area is pre-moistened with water. If, when cutting, the saw leaves the line of the mark and goes to the side, you should take it back, make a cut by moving the saw in place and guide it along the mark. It is not recommended to correct the cutting line by bending the blade.

If, when sawing a board, you made a mistake by 2-3 mm on the larger side, then to correct the mistake, fold the sawn parts, place a board under them and press both parts to it with clamps. Saw again in the right place, and the extra millimeters will be removed.

The greatest difficulty is sawing very thick workpieces, in particular hard wood. The difficulty lies in the need to maintain a straight cut. In such cases, use a special saw with a very wide blade (10–12 cm) and fine teeth (3–4 mm). You can make it from half a two-handed saw by sharpening the teeth to smaller size rectangular shape and riveted handle. In this case, the workpiece is inserted into the miter box.

Despite the markings, it is quite difficult to achieve great accuracy when sawing by hand; This is especially true for parts mating at an angle or for several parts of the same type. That is why miter boxes are also often used in this case. Precise cuts are made in the sides of the miter box at an angle of 90° and 45°, along which the saw blade moves. In this case, the workpiece rests on one of the sides, depending on the nature of the cut and the direction of sawing.

Although at first glance a box miter box is more accurate than a corner miter box, preference should still be given to the corner miter box, since it does not limit the width of the part. In a box miter box, the part is practically not pressed against the near wall due to the fact that the saw teeth are asymmetrical and push the part towards the rear side of the miter box; the front side serves only to guide the web. It is much more convenient to work if the width of the box miter box corresponds to a similar parameter of the workpiece.

During operation, the guide cuts in the walls of a miter box made of wood wear out and the processing accuracy decreases. This can be avoided if you use a saw box with replaceable blocks for guiding the cut.

To prevent the sawn-off part from breaking off and damaging the lower rib, it should be held with your hand and at the end of sawing, the saw should only be pulled towards you. Using a miter box, sawing is more convenient and accurate, and the risk of chipping is eliminated. When sawing, long boards are supported on bench stands (servers).

To cut a polished board without crumbling its surface, you must first use a ruler to scratch a groove in the varnish along the cut line. A cutter for this purpose can be made from a piece of hacksaw blade. When cutting a groove, the cutter must be pressed lightly so that the varnish is removed thin layer. The width of the groove should be 1–1.5 mm wider than the tooth set of the hacksaw.

If the varnish is applied to the board on both sides, you need to cut two grooves and only then saw it. You can saw a round stick lengthwise using a template made from a metal tube.

Although a jigsaw is a saw, it is actually very different from other types of saws.

The file of this tool is mounted in a frame so that the tops of the teeth are directed towards the handle. To stretch the canvas, the frame must be compressed.

When sawing, the workpiece must be on a special stand attached to a table or workbench, and the saw must move in a vertical direction. Work sitting or standing, so that the workpiece is at chest level.

When cutting out internal contours in the workpiece, one or more holes are first made with an awl, a gimlet or a thin spiral drill, through which a file is inserted inside. It is advisable to pierce holes at sharp turns, since turning the cutting tool is quite difficult.

One of the serious drawbacks of industrially produced jigsaw files is that they simply do not cut. And if you can work with them, then only not along the drawn line. The cutting line constantly moves to the side. Therefore, we recommend a simple way to refine industrial canvases. Their main disadvantage is a one-sided burr formed during the manufacture of teeth. Bringing the wiring to the required form is not difficult at all. You need to clamp the blade along the smooth part in the jaws of a small vice, leaving only the teeth on the outside, and then using the tip of a screwdriver, carefully bend them one by one in different directions. The same operation can be done by hitting the screwdriver handle with a light hammer.

It is a pleasure to work with a jigsaw after such fine-tuning. The service life of a jigsaw file can be significantly increased if you periodically (every 100 cm of cut) re-clamp the file in the lower clamp, releasing it by 2–3 mm.