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Sawing. Saws and sawing Rip and cross saws for circular saws

Circular saws

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Woodworking machinery

Circular saws

Circular saws are used on circular saws with a diameter of up to 800 mm and a thickness of up to 2.5 mm. On formatting machines, in addition to saws, cutters are installed.

Depending on the profile, circular saws are divided into flat (Fig. 1, a, b), in which the thickness of the disk is the same throughout the entire cross-section, and into “undercut” saws, i.e., with a thickened peripheral part of the disk (Fig. 1, V). Saws with undercuts are called planing saws. Saws are also used, on the tips of the teeth of which hard alloy plates are soldered (Fig. 1, d).

Saws with hard alloy blades are widely used in the woodworking industry for processing furniture blanks, cutting and filing slabs, plywood, veneered panels, and for sawing solid and laminated wood. The durability of the teeth of such saws is 30 - 40 times higher than the durability of the teeth of saws made of alloy steel. The diameter of saws from resharpening decreases slightly. The width of the cut when sawing with a tool with carbide blades is slightly greater than the width of the cut obtained when sawing with conventional saws, but this (especially when cutting sheet materials) does not have of great importance In addition, appropriate preparation of saws with hard alloy blades (grinding the side edges of the blades after soldering them) makes it possible to obtain a high-quality cut surface, which compensates for the loss of wood to sawdust.

Rice. 1. Circular saws: a - general form, b - profile of a flat saw, c - profile of a planing saw, d - saw tooth with a carbide plate

The outer diameter D of circular saws is the diameter of the circle drawn along the tops of the teeth. Each circular saw has an internal hole for mounting it on the saw shaft. The diameter of this hole is the internal diameter d of the saw blade and must match the diameter of the saw shaft. A gap of no more than 0.1 - 0.2 mm is allowed between the saw shaft and the hole.

The machine operator selects a saw depending on the material being processed. For example, when cutting chipboards and fiberboards, saws with carbide or hard alloy plates are used. fine teeth. For longitudinal cutting, saws with tooth profile I and II are used (Fig. 2, a), for transverse sawing, with profile III and IV (Fig. 2, b). The diameter of the circular saws is selected depending on the thickness of the material, and the profile - on the required roughness of the cut. So, if the surface is intended for gluing (for example, onto a smooth fugue), planing saws are used.

Rice. 2. Profiles of saw teeth: a - for longitudinal sawing, b - for pepper sawing

Rice. 3. Checking the forging of circular saws: 1 - saw, 2 - ruler

You should use saws of the smallest diameter for these cutting conditions, as this allows you to reduce power consumption, reduce the width of the cut and the tooth set. Saws of small diameters are more stable in operation and give best quality cutting surfaces, their teeth are easier to sharpen, and saw editing is also easier.

The requirements that circular saws must meet are as follows:

1. The saw blade must be forged, that is, its central part must be somewhat weakened by hitting it with a hammer on both sides of a blade placed on an anvil. Flat saws with a diameter of 250 mm or more need to be forged. The correctness of forging is determined by using a straight edge, placing it on the disk in the direction of the radii (Fig. 3). There should be a gap between the ruler and the saw blade in its central part, which is the same for any position of the ruler. In case of poor forging, in one position of the ruler there is a gap between it and the disk, in another there is no gap or a bulge appears.

The amount of clearance characterizes the concavity of the saw and depends on its diameter and thickness.

The need to forge saws is explained by their working conditions. During the sawing process, the saw teeth, in contact with the wood, heat up and, if the middle of the saw is not weakened by forging, the saw blade becomes bent. If the curvature is significant (exceeds the boundaries of elastic deformations), then the shape of the disk is not restored even when it is cooled. When forged correctly, the crown circular saw, heating up, slightly increases its size due to the weakened middle. This saw is stable in operation.

2. The teeth of a flat saw must be set apart, that is, their tips must be bent alternately: one tooth per right side, the neighboring one - to the left. The amount of spread on one side is 0.3 - 0.5 mm. Saws designed for longitudinal sawing of dry wood and hardwood have a smaller offset; saws for sawing freshly cut coniferous and soft hardwood have a larger offset.

Setting the teeth can be replaced by flattening them. When flattening, the width of the teeth, which are shaped like a spatula, increases. Flattened teeth are more stable and less dull than set teeth; energy consumption when using them is reduced by 12-15%.

3. Saw teeth must be sharpened. Large burrs and tip curls are not allowed. The teeth of a crosscut saw should be beveled at an angle of 40° for soft wood, 60° for hard wood, and their tips should be at the same distance from each other and from the center of the blade.

4. Saws that have at least one broken tooth or cracks on the peripheral part of the blade are considered defective; install them on. the machine is prohibited.

Before installing the saw blade, thoroughly clean the washers and shaft journal with a rag or ends and check the supporting surfaces of the washers. If even minor protrusions are detected on the supporting surface, the washers are replaced.

If diameter internal hole saws exceed the diameter of the saw shaft by more than 0.1 - 0.2 mm, insert bushings should be used for precise installation of saws. The saw is secured to the shaft using a washer and nut.

Round flat saws for cross-cutting with teeth set (Fig. 1, a, b) are used for preliminary trimming of the part, since high quality No sawing is required here. To secure it to the spindle, the saw has a mounting hole, the diameter d of which depends on the diameter of the disk D and the thickness of the saw b. The number of saw teeth should be 48, 60 or 72. The profile of the teeth for cross-cutting is shown in Fig. 1, b. The teeth must have a lateral oblique sharpening along the front and rear edges, as well as a negative front contour angle equal to minus 25°.

Rice. 4. Circular saws: a - general view, b, c - for cross cutting

In this case, the angle of sharpening of the side cutting edges of the tooth, measured in the normal section to the edges, should be 45° when sawing softwood and 55° when sawing hardwood. Circular saws with carbide inserts are used for cross cutting. Saw teeth are made with an inclined back surface, as shown in Fig. 4, f. Depending on the inclination, if you look at the tooth from the front, saws are distinguished, left-handed, right-handed, or with a symmetrical alternating inclination.

Solid steel rip saws are shown in Fig. 4, d. and with hard alloy plates - in Fig. 4, e. Circular saws for mixed sawing must have teeth whose front contour angle is 0° (Fig. 4, e).

If high cutting quality is required, planer saws with a negative rake angle are used (Fig. 4, g), as well as carbide saws with an alternating symmetrical bevel back surface teeth

Preparing round flat saws for work includes straightening, sharpening and setting the teeth. Saws after preparation for work must meet the following requirements. The number of teeth and their profile must correspond to the type of sawing. The saw blade must be flat. Deviation from flatness (warping, bulging, etc.) on each side of a disk with a diameter of up to 450 mm should be no more than 0.1 mm. The flatness of the saw is checked using a straight edge or a special device.

The required angular parameters of the teeth and the sharpness of the cutting edges must be ensured by sharpening. The sharpened teeth should not have shine at the corners formed by the intersection of the working edges of the cutter. Shine indicates that during sharpening an insufficient layer of metal was removed from the tooth. The difference in the size of the front angles and the sharpening angles is allowed no more than ±2°.

The roughness of the end surfaces of the saws and the surfaces of the mounting hole should be microns. The cutting teeth of a sharpened saw must be free of burrs, breaks and twists. Burrs from the side faces of the teeth are removed with a fine-grained grinding stone. The quality of saw sharpening is checked with a universal goniometer or a template for checking the angular elements of the teeth. The tops of the teeth should be located on the same circle with a deviation of no more than 0.15 mm. To align the gear rim in height and width, the saw teeth are planed, i.e. grind off the material from the tips of the most protruding teeth while rotating the saw at operating frequency.

After sharpening, the teeth of steel saws are set apart. In this case, the tips of adjacent teeth are bent in different directions by 1/3 of their height (counting from the top). The amount of bending of each tooth (set to one side) is set depending on the cutting mode and wood species. For cross-cutting with saws with a diameter of 500 mm, the side spread should be 0.3 mm for dry wood and 0.4 mm for wood with a moisture content of over 30%. The accuracy of the teeth set is controlled by an indicator gauge or a template. Permissible deviation ±0.05 mm.

Preparing for use of circular saws with carbide plates involves soldering the plates, sharpening and finishing the teeth. In addition, they must be balanced. Unbalanced discs due to their uneven thickness can cause loss of stability of the saw blade during operation, severe spindle runout and unsatisfactory cutting quality.

The strength of the soldering is checked by testing the saws by rotation at a peripheral speed of the teeth of at least 100 m/s. Sharpening and finishing of saws equipped with hard alloy plates is carried out on semi-automatic machines of increased accuracy and rigidity. Pre-sharpening is done with abrasive (carborundum) wheels, and finishing sharpening and finishing is done with diamond wheels.

Static balancing of saws is carried out using a special device. Disc imbalance is characterized by residual imbalance, which is equal to the product of the unbalanced mass and the amount of its displacement relative to the axis of rotation (eccentricity). The amount of residual imbalance depends on the diameter of the saw blade.

Types and sizes of saws.

The shape of the teeth of circular saws depends on the cutting direction and the hardness of the wood being cut. For longitudinal sawing, oblique teeth with a straight, broken (wolf tooth) and convex back are used; for cross cutting - isosceles (symmetrical), asymmetrical and rectangular.

Teeth with a broken and convex back are more stable than with a straight one, so saws with such teeth are used for sawing hardwood. Softwood and soft hardwood can be cut with saws that have straight-backed teeth. In Fig. Figure 31 shows a method for determining the tooth angles of a circular saw.

Rice. 5. Profiles of circular saw teeth: a - for longitudinal sawing; b - for cross cutting

When setting, the tops of the teeth are bent by 0.3-0.5 of their height. A break in the back of the wolf tooth is made from the top at a distance equal to 0.4 step sizes. Sharpening saw teeth for rip saws

sawing - straight continuous, for saws for cross-cutting - oblique through the tooth at an angle of 65 - 80° to the plane of the saw.

Planing saws are a special type of circular saws. They are used to obtain a clean cut that does not require planing.

The thickness of the planing circular saw from the toothed rim to the center along 2/3 of the radius gradually decreases at an angle of 8 - 15°. Therefore, the saw teeth do not move apart; The cutting edges of the teeth are the short front and side ones. The teeth of planing saws are grouped, or, as they say, cut with “scallops”. Each group (comb) has a large “working” tooth with a pointed angle of 45°. This tooth cuts wood. Behind the working tooth there are from 3 to 10 small teeth with a sharpening angle of 40°. The shape of the teeth on planer saws for longitudinal and transverse sawing is different.

Rice. 6. Determining the tooth angles of a circular saw

The industry produces planing saws with a diameter of 100 to 650 mm, and a tooth thickness of 1.7 to 3.8 mm. Planing saws for last years are becoming more and more widely used.

Rice. 7. Planing saws

Installation and fastening of circular saws. The circular saw is mounted on the working shaft using two clamping washers (flanges), one of which is usually machined together with the shaft; its clamping plane is strictly perpendicular to the shaft. The second washer is tightened with a nut in the direction opposite to the rotation of the saw, to prevent it from unscrewing during operation.

The washers should not protrude above the surface of the work table.

The nut must be fully tightened. A saw installed in the machine should produce a clear, ringing sound when lightly tapped.

The height of the cut when working with a circular saw is approximately equal to 1/3 of the diameter of the saw.

When choosing a saw, depending on the thickness of the material to be cut, you can be guided by the following ratios (dimensions in mm):

material thickness: 60 80 100 120 140 160 200 220 240 260 saw diameter: 200 250 300 350 400 450 500 600 650 700

Such ratios of the thickness of the material being cut and the diameter of the saw are correct when the material is pushed straight onto the saw or saws onto the material. If the saw is pushed onto the material in an arc, as, for example, in a pendulum saw, the diameter of the saw should be larger.

Requirements for circular saws and their care.

The saw blade must be well ground and free from cracks, bulges and burns. The teeth must be sharpened and evenly spaced; Burrs and burns are not allowed on them. The teeth of machine saws for longitudinal cutting are often riveted or flattened instead of being set, that is, their ends (tops) are widened by blows or pressure. For this purpose, special riveters and conditioners are used. Riveting and flattening of teeth is most often done with large round and wide band saws.

When working with a well-polished disc, the friction between the disc and the sawdust falling into the cut is reduced, so the disc heats up less.

If the disc becomes too hot, it may warp. Bulges form on it, which will quickly heat up, resulting in local tempering of the steel, causing so-called burns. These burns can be identified by their darker color, by applying a ruler to the saw, or by touch.

A saw with burns is not suitable for work; it must be straightened by forging.

Forging a circular saw is done on both sides on an anvil using a hand hammer. The parts of the disc surrounding the burn (bulge) are forged, not the burn itself. Forging begins from the areas most distant from the burn, gradually approaching it and gradually reducing the force of the blows. The straightened disc should be completely flat.

A circular saw often experiences stretching along the teeth, causing the stretched areas to become loose. Such a saw does not make a straight cut; it, as they say, “cuts.”

Stretching is eliminated by straightening, i.e., forging the saw in the middle annular part in the direction from the washers to the gear rim. This achieves some elongation of the middle annular part of the saw. The straightening is repeated from time to time. Straightening is done on a planed cast iron plate with a handbrake, selected by weight at the rate of 1 kg per 300 mm saw diameter.

If the saw has only one small crack, then in cases where it is impossible to replace it with a completely serviceable saw, a small hole is drilled at the end of the crack; This prevents the crack from increasing in length - you can continue working with such a saw. However, such a measure is always forced, temporary, and cannot be resorted to constantly.

The industry produces circular saws with balanced rotating parts. The saws are also balanced. However, in the future, the balance may be disturbed due to grinding of saws, due to the replacement of some machine parts (working shaft, washers, nuts).

The balance of the saws is checked on parallel horizontal balancing knives. The working shaft placed on the knives with the saw blade mounted on it is rotated by hand around the axis of rotation, stopping it in various positions around the circumference. If the shaft with the disk remains motionless in its given position during all such stops, then it is considered balanced. If the shaft makes some additional rotational movement, then this indicates that it is not sufficiently balanced.

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Details Category: Wood processing

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

Tool	(triangle)	Point angle
*Bow saws*
Transverse	Isosceles
Dissolute	Oblique
	Rectangular
Fine-toothed	Rectangular
Circular	Rectangular	50-60 or 80-85	Straight or small boring
*Hacksaws*
	Isosceles or rectangular	Depends on the shape of the teeth
	Rectangular
Obushkova	Rectangular
Award	Isosceles

Purpose of sawing tools

Types of hacksaws and special saws	Purpose	Appearance and device
Wide	Cross rough sawing
Narrow (trigger)	Through sawing on a plane and curved sawing
Obushkovaya (slotted)	Finishing shallow cuts and adjusting products during assembly
Award (blade made from scraps of old saws)	Shallow sawing of grooves

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 blanks and figure sawing, 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 your 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.

A hand saw, at first glance, is a fairly simple tool that does not require much maintenance. However, few people know about the criteria for choosing a saw and its types. Like other tools, a hand saw has certain signs of quality and characteristics.

Basic parameters of hand tools for cutting wood

The hacksaw is one of the most necessary tools in every man's inventory. This device allows you to easily change the dimensions of wood and plastic lumber. Using a hacksaw, you can perform a lot of operations in construction, cut branches in the garden, shorten fence poles, and so on.

A hand saw is used to work with lumber

But when purchasing such a seemingly simple tool, not everyone thinks about how to make the right choice and what criteria need to be taken into account. A hacksaw has its own special parameters that can affect the quality of work. There are four basic parameters when choosing a hacksaw: blade length, tooth size, steel type and handle type.

Blade length

For ease of use, the length of the hacksaw blade is chosen so that it is twice the size of the material at the cut site. This allows you to effectively remove sawdust during work due to the fact that all the teeth of the blade will come out of the board/log. In addition, this ratio of the size of the hacksaw and lumber contributes to a greater range of hand movement. This, in turn, takes much less effort. In construction, a universal hacksaw with a blade length of 45–50 centimeters is most often used. To work with small bars and boards, a blade 30–35 centimeters long will be sufficient.

Tooth size

This is perhaps the most important parameter. After all, the speed and accuracy of cutting depends on the size of the tooth.. The number of teeth per inch of blade is usually denoted by the TPI coefficient. To work more accurately with the material, it is necessary to use a hacksaw with a high TPI coefficient, that is, with big amount teeth. When choosing a blade with a TPI of at least 7–9, and a distance between teeth of no more than 2–4 mm, the surface at the cutting site will be smoother and without torn edges. For working with large beams and garden trees, a blade with a TPI of 3–6 and a tooth spacing of over 4 mm will work well. Using such a hacksaw will reduce the effort required and increase the speed of cutting the working material.

Tooth pitch correspondence table

1 TPI = 25.5mm	10 TPI = 2.5mm
2 TPI = 12mm	11 TPI = 2.3mm
3 TPI = 8.5mm	12 TPI = 2mm
4 TPI = 6.5mm	13 TPI = 2mm
5 TPI = 5mm	14 TPI = 1.8mm
6 TPI = 4mm	17 TPI = 1.5mm
7 TPI = 3.5mm	19 TPI = 1.3mm
8 TPI = 3mm	22 TPI = 1.1mm
9 TPI = 2.8mm	25 TPI = 1mm

Sharpening teeth

The usual triangular shape of hacksaw teeth is taken as standard. The teeth are made in the form of an acute triangle or isosceles, depending on the purpose of the cut. Such a blade can be sharpened with particular ease by repeating all the angles of the teeth. This blade can be used for both longitudinal and transverse cuts to avoid rough notches.

The teeth of a classic hacksaw are made in the shape of a triangle and can be sharpened

Video: self-sharpening hacksaw teeth for wood

But modern hacksaws, unlike classic ones, have hardened teeth with a non-standard trapezoidal shape. Such saws are endowed with increased strength and are resistant to wear. Their steel cannot be sharpened, and it is very difficult to maintain all the angles of the sharpened teeth.

Modern hacksaws are made with hardened teeth in the shape of a trapezoid.

Steel type

High-grade stainless steel is most often used to produce hacksaw blades. Typically, wood saws are made of steel with a hardness of HRC45. Very often, manufacturers combine steel in the canvas. In a hacksaw with a combined blade most of also made of 45 steel, but cutting part made of steel 55 and 60. When the cutting edge is hardened, wear resistance increases. This type of tool can be easily distinguished from a regular hacksaw by its dark, hardened teeth.

The first forged saws were made back in Ancient Greece. Forging gave high hardness to the metal and improved the quality of the tool.

Handle type

The ease of use of the saw depends on the correct choice of saw handle. Handles are made of wood or plastic. Very important point- the surface at the grip site should be such that the hand does not slip. This can be eliminated by scarring the handle or covering it with a rubber layer. The hacksaw can be either a classic cast saw or with a reversible blade. The latter allows you to replace the canvas, which is very convenient.

How to choose a hand saw

By combining all the basic parameters of the saw, everyone can easily decide for themselves which one suits them best. When choosing a tool, you need to decide for yourself which saw is more suitable - a carpenter's or a carpenter's saw. If the most important thing is cutting speed, then, of course, you need to purchase a carpenter's tool. A carpenter's hacksaw has fewer teeth per inch, which helps fast performance and removal of sawdust. If cutting accuracy is a priority, then you should use a carpentry shop.

The quality of a hacksaw can be determined in simple ways. First you need to visually verify the evenness of the canvas. Then you need to bend the canvas with a little effort and release it as soon as resistance appears. After the blade plays back and calms down, you should again check the evenness of the blade. If it is slightly deviated from the original position, then the tool is of poor quality and it is not recommended to buy it.

If you need a rip saw, you need to choose a hacksaw with sharp teeth. The teeth of such saws are sharpened only on one side, so the cut will be made only in one direction - away from you.

The teeth of the rip saw blade are sharpened in the shape of an acute triangle

When longitudinal sawing, the cut occurs parallel to the fibers of the material. For rip sawing, circular saws and bow saws are well suited.

Crosscut saws are the most common. Their teeth are shaped like isosceles triangle and sharpened on both sides. This allows you to cut in both directions.

For cross cutting, the teeth of the blade are made in the shape of an isosceles triangle and sharpened on both sides

When cross-cutting, the material is cut across the grain. For such sawing, classic hacksaws, hacksaws with a backrest, and, for large material thicknesses, two-handed saws are suitable.

The price of the saw is also an equally important factor when choosing. A more expensive hacksaw guarantees reliability and wear resistance. Those saws whose price is significantly lower than average are made from cheaper raw materials and do not guarantee you long-term service.

What types of hand saws are used for what purposes?

Photo gallery: types of hand saws

This classic hacksaw can be easily sharpened. This hacksaw has hardened teeth and increased wear resistance. A hacksaw with a back or butt minimizes vibrations of the blade during work. A hacksaw with a narrow blade is well suited for cutting holes and grooves.
This type of saw has an adjustable handle, which allows you to work at the desired angle. A bow saw is well suited for cutting parts from plywood. This type of hacksaw is similar to a plane and is used for cutting tenons and slots. A two-handed saw is suitable for cutting large logs.
Garden saws with curved blades are well suited for cutting down knots and small tree branches.
The hand chain saw is compact and well suited for sawing logs while camping and branches in the garden.

Thus, having carefully studied all the nuances regarding hand saws, everyone can choose the most suitable option for themselves. Right choice the tool will provide you with high-quality and pleasant work.

Longitudinal sawing of wood with a circular saw - difficult process closed cutting with a multi-cutting rotating tool in the shape of a disk (circular saw), in which the feed speed vector coincides with the direction of the wood fibers and the cut is parallel to the fibers.

Rice. Kinematics and geometry of the cut layer during longitudinal sawing with a circular saw - sawing scheme with the saw located at the top relative to the workpiece.

Ripping is the operating process of a large and diverse group of circular saws designed for dividing by width and thickness in the technological operation of longitudinal cutting of logs, beams, boards, slabs, bars and slats.

When longitudinal sawing, the main (short) blade of the tooth cuts the wood fibers and forms the bottom of the cut, and the side blades participate in the formation of the cut wall. This distribution of functions predetermines the requirements for the geometry of the saw teeth for longitudinal sawing: the short blade must be moved forward in the direction of rotation relative to the front edge due to the positive angle y. This will cut the fibers before they begin to separate at the front edge. With increased requirements for the quality of the cut walls, a positive rake angle must be created at the side blades due to oblique sharpening along the front edge. Since the teeth form two walls of the cut, oblique sharpening must be done through the tooth: for even teeth - in one direction, for odd teeth - in the other.

The cutting diameter (saw diameter) D = 2R, mm, is assumed to be the same for all teeth. The rotation speed of the saw n, min "1, is considered constant. Then the speed of the main movement vr (m/s) will be

V CP = pi*D*n/60*1000, (m/s).

The feed movement is usually applied to the workpiece. The mechanical feed speed vs in machine tools reaches 100 m/min or more.

The feed per revolution of the saw S0 and per tooth Sz (mm) is determined by the formulas:

So=1000*Vs/n, Sz=So/z. N = k*Apopr*Vopr*t*Vs/60.

A distinction is made between sawing with counter feed, when the projection of the cutting speed ve on the direction of feed and the vector of feed speed of the workpiece vs are directed towards each other, and with cutting feed, when they coincide in direction.

In rip sawing, downfeed is rarely used. Climb feed is often found in crosscut sawing when the workpiece is stationary. In Fig. Sawing with counter feed is shown. Changing the direction of the vs vector will correspond to the sawing pattern with a passing feed.

Geometry of the cut layer. The layer is cut along the arc AB, which is called the arc of tooth-wood contact. Point A is the entry point, point B is the exit point of the tooth from the wood. Midpoint C bisects the arc of contact.

Forces and cutting power. Forces Fx and Fz on one saw tooth. The lateral force Fy is defined as the projection onto the Y axis of the resultant interaction force of the teeth, the interaction force of the chips and the interaction force of the saw blade with the wood.

For longitudinal sawing, solid steel saws are used (Fig. 3, c, e). For finishing sawing, saws with a negative rake angle are used (Fig. 3g), as well as saws with carbide blades.

For cross-cutting, round flat saws with teeth are used (Fig. 3, a, b, c), (number of teeth, Z = 48, 60, 72, 96 pcs.).

Cross-cutting is a circular sawing formed as a result of sawing the end surfaces.

Power characteristics of cross cutting.

Nres = k*Vpopr*t*Vs/1000*60. Px cp = Px table * Vpr * Appr.

When cross-sawing, the operating conditions of the tool blades are much more complicated; based on this, the calculation of the cutting forces on the tooth is carried out using experimental data, i.e., P x avg. calculated through P xt, related to the unit of cutting width: P x av = P xt V right and right;

P z avg on a tooth is calculated by P x avg: P z avg = mP x avg; P x env, and P z env are calculated

identical to sawing along the grain of wood.

K category: Carpentry work

Sawing by hand

Sawing is a type of cutting in which wood is separated to form a cut and separate sawdust. The cut is limited by three faces, of which the bottom is called the bottom, and the other two are called the side surfaces.

Sawing involves cutting boards lengthwise into sections, sawing boards or sections widthwise into bars or slats, trimming parts to length, trimming edges, sawing boards and plywood, as well as curved and openwork sawing.

A saw for hand sawing (is a steel strip, on one edge of which there are teeth-cutters located sequentially one after another (Fig. 38). Between the teeth there are depressions, the so-called sinuses. Each saw tooth has three cutting edges corresponding to the number of cutting planes.

The cutting edge of the tooth, which serves to form the bottom of the cut, is called the short or front cutting edge; the side surfaces of the cut are formed by the side cutting edges of the tooth. The lateral cutting edge is formed by the front edge and the side surface of the tooth.

The dimensions of the saw tooth are determined by the pitch and height. The tooth pitch is the distance between the tips of two adjacent teeth. The height of a tooth is the distance from its top to its base, determined by a perpendicular drawn from the top of the tooth to the base line.

The front edge of the saw tooth for longitudinal sawing is called the breast, the back - the back. Saw teeth have different shapes.

For longitudinal sawing, saws with oblique (oblique) teeth are used. The cutting edge of such a tooth is its front, short edge. The side edges chip away sawdust. Sharpening saw teeth for longitudinal sawing is done at a right angle to the saw blade. This sharpening is called straight. The teeth only work when the saw moves forward, i.e. in the direction in which the teeth are tilted. The sharpening angles of saw teeth for longitudinal sawing of soft rocks are from 40 to 50° and hard rocks up to 70°. Cutting angle up to 80°.

Rice. 1. Saws: a - saw tooth elements; b - saw tooth angles: 1 - for longitudinal, 2 - for mixed, 3 - for cross cutting

For cross cutting, saws with teeth in the form of an isosceles or equilateral triangle are used. The cutting edges of such teeth are the side edges. Sharpening of the teeth is done with an oblique at an acute angle to the saw blade. The top of the tooth is a triangular incisor. Oblique sharpening, often called boring or pointing, is performed through a tooth. The teeth of such a saw work when moving in both directions. The angle between the cutting side edges of the saw teeth for cross-cutting is 60-70°, and the sharpening angle between the chamfer and the side edge of the saw blade is from 45 to 80°. Cutting angle more than 90°.

For mixed longitudinal-transverse sawing (along curved outlines), saws with a tooth in the form of right triangle. Teeth for mixed sawing are cut with all edges of the breast. These teeth are sharpened at right angles to the saw blade or with a small bore (75-80°). The teeth of such a saw only work when moving forward. The sharpening angle of the saw teeth for mixed sawing is 50-60°; cutting angle 90°.

Rice. 2. Bow saw

Hand saws

Hand-held joinery saws come in tensioned thin blades and loose, thicker blades. Tension saws include all bow saws; for saws with a free blade - hacksaws.

A bow saw (Fig. 2) consists of a wooden machine (beam) and a saw blade stretched on it. The bow consists of two posts, a spacer, two handles, a bowstring made of string or wire and a twist.

According to their purpose, bow saws are divided into transverse, open, tenon, fine-tooth and rotary.

Cross-cut saws have a length of 750-800 mm, a blade width of 20-25 mm and a blade thickness of 0.4-0.7 mm. Their teeth have the shape of an isosceles triangle 5 mm high, pitch 4-5 mm, oblique sharpening (boring).

Opening (swing) saws are used for longitudinal sawing of long boards; they have a length of 1000-800 mm, a blade width of 45-55 mm and a thickness of 0.4-0.7 mm. Their teeth have an inclined shape, height 5-6 mm, pitch 5-6 mm, sharpening angle 40-50°, cutting angle up to 80°, straight sharpening. The tooth spread is equal to twice the thickness of the blade. Saws work quickly, produce rough cuts, and require a lot of effort.

Tenon saws are intended for clean cutting of ends and sawing of tenons; they have a length of 600-800 mm, a blade width of 40-50 mm and a thickness of 0.4-0.5 mm. Their teeth have the shape of a right triangle with a height of 3-4 mm, a sharpening angle of 80-85° (to the blade), and a bore. The tooth set is 12/3 of the thickness of the saw blade. Compared to a loose saw, a tenon saw requires significantly less effort when cutting.

Rice. 3. Knife saws: a - wide, b - narrow, c - butt saws, d - awards

Fine-tooth saws are used for clean cross-cutting, have a length of 700 mm, a blade width of 30-40 mm and a thickness of 0.4-0.5 mm. Their teeth have the shape of a right triangle with a height of 2-3 mm, a pitch of 2-3 mm, a sharpening angle of 60-80°, and a bore. The tooth spread is 1/3 of the thickness of the saw blade. The saw requires little effort when cutting.

Rotary (circular) saws are designed for figure sawing, have a length of 350-500 mm, a width of 4-15 mm, and a thickness of 0.4-1 mm. Their teeth have the shape of a right triangle 2-3 mm high, pitch 2-4 mm, sharpening angle 50-60°, straight sharpening or small boring.

Knife saws (hacksaws) can be wide or narrow.

Wide hacksaws (Fig. 3, a) are used for transverse, straight cutting of boards. The thickness of the canvas is up to 1.5 mm. Saw length 400-700 mm. The teeth of wide hacksaws have the shape of an isosceles triangle with a sharpening angle of 55°. The teeth set is 0.4-0.6 mm per side.

Narrow hacksaws (Fig. 3, b) for figured sawing are used in cases where sawing is carried out along the internal contour of the workpiece. Narrow hacksaws are usually made smaller than wide ones (300-400 mm). The thickness of the canvas is 1.5 mm. The divorce is done very small; the teeth are shaped like a right triangle.

Back saws (Fig. 3, c) have a thin rectangular blade with a thickness of 0.6-0.8 mm. A steel butt is riveted to the upper edge of the backing saw to give it rigidity. The saw teeth have the shape of a right triangle with a fine pitch and a very slight set. The teeth cut when moving away from you. Backing saws are used for fitting joints, shallow sawing, sawing small parts and mitering corner joints.

Rewards (Fig. 3, d) with a blade fixed in a wooden frame are used for sawing slots (grooves, grooves) to a certain depth, not across the entire width of the surface being processed. Saw with a reward along a ruler at any angle to the plane with the initial movement of the saw only towards you. The teeth of the teeth are directed towards the worker. The teeth have the shape of a right triangle with a fine pitch and a very slight set.

Plywood saw is a special award with fine teeth located along a curved convex line. Used for cutting planed plywood.

To eliminate jamming of the saw in the cut, change the shape of its teeth or set them apart (Fig. 4, a, b, c, d). For the same purpose, the saw blade is made of a trapezoidal cross-section with the teeth located at a wider base.

The amount of set of all teeth must be the same, otherwise the less bent teeth will not participate in sawing, and the most bent teeth will not carry heavy load. The saw teeth are set using special sets, clamping the saw blade at the base line of the teeth in a wooden vice (Fig. 5). The best sets provide the same amount of set of all teeth. In Fig. 6 shows universal wiring. When working with it, the saw blade is clamped in a vice mounted in a workbench.

Rice. 4. Different kinds changes in the shape of the saw teeth: a - setting, b - flattening, a - trapezoidal widening, d - times. vodka with side sharpening for cross cutting

Rice. 5. Saw teeth set

Rice. 6. Vise

After setting, the saw teeth are sharpened. This is done with a triangular file with a fine notch. When sharpening straight, the file is held perpendicular to the blade, and when sharpening - at an angle of 45-80° (Fig. 8, a, b). When sharpening directly, the edges of the file during operation should coincide with the breast and back of the tooth (Fig. 8, c). The file is pressed against the saw tooth when moving away from you, and when moving back, it is raised so that it does not touch the saw.

For the saw to work well, it is important that the teeth are not only sharpened and set apart, but also have the same height. During operation of the saw, the teeth work differently, so before sharpening they should be aligned in height or ground. The tool for jointing saws is a file inserted into a wooden block (Fig. 9).

Rice. 7. Universal wiring: 1 - bending lever, 2 - plate for adjusting the width of the saw blade, 3 - adjusting screws, 4 - hinge adjuster. adjuster for the amount of adjustment, 5 - scale for setting the amount of adjustment, 6 - screw with a stop for teeth of different sizes, 7 - spring

Rice. 8. Sharpening saws: a - direction of the file during straight sharpening, b - direction of the file during oblique sharpening, c - position of the file on the saw teeth

Rice. 9. Device for jointing saw teeth

Job hand saws

There are three main types of hand sawing wood:
a) longitudinal at horizontal position material;
b) longitudinal when the material is in a vertical position;
c) transverse.

The least labor-intensive is sawing the board longitudinally in a horizontal position. Before starting sawing, cut lines are marked on the selected board using a surface planer. The cutting line is marked in such a way that after sawing there remains a certain supply of material for subsequent processing. Then the board is secured to the workbench along its front edge so that the sawn part protrudes beyond the edge of the workbench. The board is secured with a clamp or a bench blade.

The saw blade is rotated at a certain angle relative to the plane of the beam and tensioned. The opening saw is held by the handle and the angle of the spacer. Its position during the sawing process should remain vertical (Fig. 10).

Rice. 10. The position of the worker’s legs when longitudinally sawing a board installed horizontally

The legs of the worker in relation to the material should be positioned as shown in Fig. 10.

Sawing should be done with free movements, pressing the saw to the bottom of the cut as it moves downward and forward. When the saw is idling upward, it should be moved back slightly. If the saw is clamped, a small wedge is inserted into the cut behind it. Sawing long boards is done using bench stands.

Rice. 11. Longitudinal sawing of a horizontal board

When longitudinally sawing material located vertically, there can be two types of sawing: perpendicular and parallel to the face. In the first case, the material is secured in the rear vice of the workbench, and in the second case, in the front.

Hold the saw while cutting right hand behind the counter, as close to the handle as possible. With the left hand, support the material being cut. The movement of the saw during operation should be horizontal.

The legs and body of the material working when sawing, installed vertically, are positioned as shown in Fig. 13. Body and left hand must remain motionless during operation.

When the board is in a vertical position, the start of the cut should not be placed very high. The saw is first set on the mark and a short, slow movement of the saw towards itself makes a shallow cut. Before the formation of a gash, it is impossible to saw in a sweeping manner. When sawing, do not press the saw too hard, as this will not speed up the work. You should also not press with your left hand on the sawn block.

Rice. 12. The position of the worker’s legs when longitudinally sawing a board installed vertically

Rice. 13. Sawing across the grain of material located horizontally

When sawing across the grain with a bow saw, the board is laid on the edge of the workbench so that the part to be sawn protrudes beyond the back bar of the lid, and the end rests against the folding stop.

The saw is held with the right hand by the stand near the handle, and the material being cut is supported and pressed against the stop with the left hand. The saw should be held at an angle of no more than 10-15° to the upper plane of the material being cut (Fig. 13).

The worker stands so that his left foot is located perpendicular to the board being cut, and his right foot steps back and to the right with a turn at an angle of about 80° (Fig. 14).

The body is motionless during sawing, slightly tilted forward.

Sawing across the grain is the most labor-intensive type of sawing and requires some pressure on the material. In order to make a cut, the saw blade is directed along the nail or along the second joint thumb left hand.

Rice. 14. The position of the worker’s legs when sawing horizontally located material across the grain

Rice. 15. Sawing along the thumb joint

In this case, the joint should be kept above the teeth (Fig. 15). The cut is made by smoothly moving the saw towards you.

At the end of the cut, the part of the board to be sawn should be supported with your left hand to avoid chipping the wood.

To cut parts at an angle, a so-called miter box is used (Fig. 16). It is a tray made of boards with slots for saws located in the sides at a certain angle. When using a miter box, it is clamped into the workbench.

Rice. 16. Miter box

Defects when sawing with hand saws can be the result of improper sharpening or misalignment of the saw. This results in an uneven, non-straight or rough cut. Due to the skew of the saw blade during operation or incorrect working posture, the cut may not be perpendicular to the face or edge of the board.

- Sawing by hand