Saw teeth sharpening
When working with a saw, its teeth become dull, the front and side edges of the teeth are rounded. To ensure that their cutting ability is not lost, it is necessary to regularly sharpen the saw teeth, and sometimes even cut new ones. The saw is sharpened with files. When sharpening, the profile of the saw is taken into account, because the shape, pitch or height of the sawtooth must not be changed.
If the saw has straight-sharpened teeth, then they are sharpened by removing the top layer of metal from both edges at the same time. This is how the saw is sharpened, which is designed for cross or longitudinal sawing. The angle between the front and back edges should be 60 °, this angle corresponds to the profile angle of the triangular file.
If the angle between the edges is less than 60º, then sharpening the saw requires only removing metal from the back edge. The front edge is sharpened only slightly to remove burrs. Rhombic files are used for sharpening this type of saws.
The level of sharpening of the teeth is determined by the number of burrs on the edges. Sharpening the saw does not give a perfect result. The use of a file makes it possible to obtain teeth with a surface roughness of 100 60 microns.
How to Sharpen a Woodworking Handsaw | Paul Sellers
The file also forms small burrs on the teeth, which lead to dullness. In order for the sharpening result to be close to ideal, it is necessary to perform additional processing of the saw teeth. After sharpening the teeth, you can remove the burrs on the side edges with a touchstone. In order to remove them, you need to run a wet donkey along the sides of the saw teeth. The roughness after such procedures will be about 32 4 microns.
The saw is sharpened as follows: the blade is set in a wooden vise and clamped in a workbench. The pressure should be even and smooth. Sharpening is only necessary when moving forward with a file. In the opposite direction, the file should go freely, without pressure.
Sharpening the saw in one direction increases the level of wear resistance of the teeth. If during sharpening some teeth are sharpened more, i.e. the bottom of the cut is broken, then they will bear the greatest load when cutting the material, which means they will wear out faster. Therefore, when sharpening the teeth, it is imperative to monitor their level, they must be strictly on one mowing line.
What is the quality of a hand saw cut? What determines the effort required to cut when using a hand saw? There is only one answer to these questions. First of all, these factors are influenced by the care of the saw teeth, namely the correct sharpening of the saw.
Saw Tooth Set
To reduce friction and clamp the saw blade in the cut, the following conditions are necessary: the kerf must be wider than the blade thickness. If their thicknesses are equal, then this can lead to friction, and, consequently, to heating of the web. When heated, the web expands and friction increases. This can lead to seizure.
For free movement of the blade in the cut, the teeth must be set apart. Divorce is performed as follows: through the tooth, it is necessary to bend all the teeth on both sides by the same amount.
The amount of set of teeth for a hand saw is 0.2 0.3 mm. The main condition is that the divorce should not be more than the thickness of the canvas.
It is necessary to spread the teeth with a special tool. wiring. It is not necessary to bend the teeth at the base, but at half the height of the tooth. Bending at the base may stretch the saw.
Sharpening the saw is a preventive measure. But sometimes it is too late to do such prevention. In this case, you have to cut new teeth. New teeth are also cut when they are broken.
Before you start cutting new teeth, you need to grind off the old ones to the ground. Next, the canvas is jointed.
Cutting new teeth is a long and tedious process. Several files are required for cutting.
In order to speed up the process of cutting teeth, a special device is used, which can be made in special workshops.
Planing the tops of the teeth. Tooth set. File sharpening saws.
Saw preparation consists of the processes of planing, setting and sharpening the saws.
First, the saws must be thoroughly cleaned of resin, adhering sawdust, rust, rinsed in kerosene. If the surfaces of the blades are uneven, they are straightened with a hammer on a flat metal plate. Then they proceed to jointing. alignment of the tips of the saw teeth, since they must be at the same height. A file 1 is inserted into a wooden block (Fig. 11, a), after which the block with a file is put on the saw 3 and moved along the blade, while aligning the tops of the teeth.
You can also align the tops of the saw teeth in another way. In the workbench 4, a board is strengthened (Fig. 11, b), into the slot of which a file is inserted, after which the saw blade is inserted into this slot with the teeth down and, moving the saw along the file, align the tops of the teeth. It is necessary to align the tops of the teeth periodically, otherwise they will unevenly participate in the sawing. The quality of the planing is checked by applying a ruler to the tops of the teeth. If the tops of the teeth are close to the edge of the ruler, the planer is correct.
During the sawing process, the saw blade rubs against the walls of the board being sawn and is clamped in the cut. To avoid jamming the saw blade in the cut, the teeth must be set.
The spread of saw teeth is that they are bent one by one: even teeth in one direction, and odd ones. to another. When separating the teeth, it is necessary to bend to the side not the entire tooth, but only its upper part approximately at a height of up to 2/3 of the base. When sawing hardwood, the teeth are set at 0.25. 0.5 mm on the side, but soft rocks. 0.5. 0.7 mm.
The teeth of hand saws are bred using the wiring (Fig. 12, a) as follows. The saw blade is tightly clamped in a vice, and then the teeth are bent alternately in one direction or the other. It is necessary to spread the saw teeth evenly, without applying great efforts and sudden movements, as otherwise the tooth can be broken.
In addition to the usual one, a universal wiring is used (Fig. 12, c), consisting of a lever 3, designed to bend the saw tooth, plate 4, which regulates the width of the gap for the saw passage, and adjusting screws 5. In the upper part of the wiring there is a scale 7 showing the amount of divorce. and a screw 8 with a stop, which regulates the height of the bent tooth. Spring 9 serves to return the lever 3 to its original position after compression of the wiring.
but. simple wiring with stops, b. template for checking the correct setting of the saw teeth, c. universal wiring, g. indicator divider, type RI; 1.saw, 2. template, 3. lever, 4. plate, 5. adjusting screws, 6. swivel adjuster, 7. scale, 8. screw with stop, 9. spring, 10. support surface, 11. indicator
The correctness of the spread of the saw teeth is checked with a template 2 (Fig. 12, b), applying it to the saw blade 1, clamped in a vice. The even teeth are checked first, and then the odd ones. Incorrectly bent teeth need to be corrected.
The correctness of the saws divorce can be checked more accurately with an indicator divider of the RI type (Fig. 12, d). When measuring, the water meter is pressed tightly against the saw blade with the supporting surface, and the indicator tip is placed opposite the top of the controlled tooth. By the deviation of the indicator arrow, the amount of divorce is determined.
Next operation. sharpening saw teeth with double and single cut files. Files are distinguished by shape, triangular, rhombic and flat. Hand saws are usually sharpened with triangular or rhombic files.
When sharpening, the saw blade is clamped in a vice, fixed on a workbench. The file is pressed against the tooth when moving away from you, and when it is returned, it is slightly raised so that it does not touch the saw. Do not press the file strongly against the tooth, as this will heat up, which will lead to a decrease in the strength of the saw teeth. Straight-cut teeth for ripping saws are sharpened on one side, with the file held perpendicular to the saw blade.
Saws for cross-cutting wood have an oblique sharpening, so their teeth are sharpened with a file, which is held at an angle of 60.70 °. For these saws, the teeth are sharpened after one. Having sharpened the teeth on one side, the saw is turned towards itself with the other side and, having strengthened in a vice, the remaining teeth are sharpened.
Bow saws are sharpened with triangular files, which are selected according to the size of the saw teeth. Sharpened saws should be free of burrs, stains and other defects. Manual saw sharpening techniques are shown in Fig. 13.
but. location of the pilot hole for direct sharpening, b. the location of the pilot hole when sharpening obliquely, c. sharpening a bow saw in a vice, d. sharpening a bow saw in a wooden block
Sharpening saw teeth
Sharpening of circular saws and cutters on this device is carried out in the usual way. by grinding the front edges of their teeth. In this case, the saw teeth for longitudinal sawing are sharpened at right angles to the side surface (Fig. 180 a), and the saw teeth for cross sawing. at an angle of 60-70 ° (Fig. 180 b). If necessary, this device allows you to restore the correct backing of the cutting edge of the teeth, as well as eliminate the beating of the saw blades in diameter. [. ]
The sharpening of the teeth provides the specified angular parameters of the teeth and the sharpness of the cutting edges. For sharpening circular saws, it is recommended to use grinding wheels of the EB25ST2B and EB40STV brands. The feed per wheel stroke should not exceed 0.06 mm. At the same time, 2-3 easy passes are made with the amount of penetration per wheel stroke of no more than 0.02 mm. Burrs from the lateral edges of the teeth are removed with a fine-grained grinding bar. [. ]
The saw teeth are the main part of it. There are front, rear and side edges. Front. the main edges of the teeth. When sawing, they form the bottom of the cut, the side front edges create the side surfaces of the cut. The straight line passing through the tops of the teeth is called the line of the tops, and the line that defines the bottom of the valleys is called the line of the bottom of the valleys. The shortest distance between the vertex line and the valley line is the height of the tooth. The distance between the front cutting edges of adjacent teeth is called the tooth pitch. When sharpening the saw, keep in mind that the teeth must have the same height. [. ]
After sharpening, the saw teeth are bred. At the same time, the tips of adjacent teeth are bent in different directions by 1/3 of their height. The amount of bend of each tooth (spread on the side) is set depending on the cutting and type of wood. [. ]
The shape of the saw tooth and its sharpening must correspond to the nature of sawing: for longitudinal sawing, the tooth must have the form of an oblique triangle, for transverse. view of an isosceles or equilateral triangle, but for a mixed one. view of a right triangle. At its base, the tooth is connected to the body of the saw blade. In this case, the height of the tooth is the distance from its base to the top. The distance between the tops of adjacent teeth is called pitch, and the gaps between the teeth. sinuses. [. ]
The shape and angles of the teeth are different depending on the type of sawing. For rip saws, teeth are straight sharpened, that is, the front cutting part of the tooth is at right angles to the side edges. When ripping, the front edge of the pick separates the chips from the bottom of the cut. Each tooth in this process plays the role of a straight chisel with an angle of inclination to the wood at an angle of less than 90 °, that is, a cutting angle of 60-80 °, and with mixed sawing it should be at a right angle [. ]
Dull teeth are sharpened and adjusted with abrasive wheels and automatic sharpening machines. Sharpening is performed when a small (up to 0.05 mm) metal layer is removed in one pass. In this case, the saw is passed through the automatic machine 3.4 times. In order to align the toothed wheel in height and width, the teeth are planed or the material is co-grinded from the protruding teeth. [. ]
Garden saws are sharpened with fine abrasive discs on special sharpening machines or with triangular and rhombic files with a fine notch. The filing angle of the teeth should be approximately 45 °. At the hand point, the saw must be firmly clamped in a vice. If the blade is loosely clamped and it vibrates, then it is not possible to get sharp cutting edges at the teeth. [. ]
The cutting edges of the sawing tool teeth become dull during operation, so band saws are periodically sharpened. The quality of sharpening depends on the correctly selected modes, the size and sharpness of the abrasive grains. Sharpening is done with grinding wheels of appropriate grain size, bond type, hardness and structure. Electrocorundum, silicon carbide, boron carbide, diamond are used as the grinding material. For sharpening steel band saws, fused alumina grades 16A, 15A, 14A, 13A, 12A or white fused alumina 25A, 24A, 23A, 22A are used. [. ]
Before sharpening the saw, you need to separate the teeth, that is, bend them through one in different directions by 0.5-1 of the blade thickness, for which they use the wiring For lack of wiring, you can use an ordinary chisel or a wide screwdriver. For sharpening, semicircular, triangular files are used, and for a very small tooth, needle files. The saw must be clamped in a yew. In the absence of yews or special clamping devices, you can sharpen the saw by pressing the blade against the stop, for example, against the edge of the table. Saws, whose teeth are in the form of rectangular or isosceles triangles with oblique sharpening, go through the tooth with a file on one side, then turn the saw and sharpen on the other side (Fig. 25-32). [. ]
Improving the durability of saw teeth can be achieved by grinding the processed edges after sharpening in order to make them smoother and after deburring. If they are not removed, they break off during cutting and significantly reduce the sharpness of the cutter. [. ]
The last operation in the preparation of saws. sharpening of the teeth is carried out after each flattening and setting to restore the cutting properties of the saw. When sharpening, it is necessary to keep the profile of the teeth unchanged. The cutting edges of the teeth should have a flat smooth surface without burrs, twists and. Defects. semiautomatic machines T TchPB and TchPA-6. The notch of teeth on the saws is carried out with the sawstamp PSh6. [.]
The durability of the toothed edges of the frame saws can be significantly increased by surfacing the tips of the teeth with hard alloys. Saws, hardfaced steels are widely used.The period of operation of such saws between sharpening increases. 2.5 times, the quality of the sawn surface is improved. [. ]
Preparation for work of circular flat saws includes dressing, sharpening and setting of teeth. Saws after preparation 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. The deviation from flatness (warpage) on each side of a disc with a diameter of up to 450 mm should be no more than 0.1 mm. The flatness of the saw is checked with a straight edge or on a special device. If flatness is violated, local and general defects in the shape of the blade are corrected by straightening with a forging hammer. Before this, the established boundaries of defects are outlined with chalk. [. ]
Torn cuts occur when working with blunt saws of an irregular profile and sharpening saw teeth. To make this defect, it is necessary to change the profile of the teeth or sharpen the saws. [. ]
The main operations of preparing circular saws for work are cutting and notching teeth, dressing, rolling or forging, sharpening teeth, setting them or flattening them, installing the saw on the machine. [. ]
A triangular personal file is required for sharpening and dressing saws. Before sharpening, the saw teeth are spread using a special device called a set. It can be replaced with a wide screwdriver, pliers, pliers. In the future, you will need to acquire a set of files: a velvet file for deburring, flat, square, round, as well as a rasp. a file with a large notch. for processing curved wooden parts, grinding ends. [. ]
The correct setting can be checked by looking along the blade: not a single tooth should protrude from the general row. If protruding tooth tips are visible, they should be aligned. To do this, the saw blade is pulled between two metal plates, slightly clamped in a vice. The saw is bred every two to three years, that is, after four to six sharpenings. [. ]
To prepare the cutting tool, the following are used: semiautomatic device RPK-8 for setting the teeth of circular saws with a diameter of. 160-800 mm; ASLP18 and ASLP35 machines for butt welding of band saws with a width of 50–180 and 150–350 mm, respectively; AB-20 machine for rolling frame band saws up to 200 mm wide and circular saws up to 800 mm in diameter, maximum saw thickness 2.5 mm; semi-automatic machine TchPR-2 for sharpening frame saws of the following dimensions, mm: length 1100-1950, width 80-200, thickness 16-2.5, tooth pitch 18-40 mm; machine TchPA-5 for sharpening frame saws 50-200 mm wide and circular saws with a diameter of 200-300 mm; semi-automatic machine TchA35 for sharpening band and dividing saws with a width of 180-350 mm, a blade thickness of 1.4-2.2 mm. the height of the teeth of the sharpened saws is 16-24 mm; semiautomatic device TchN6-4 for sharpening steel flat knives with a straight cutting edge. [. ]
The wood is sawn across, along the fibers and at an angle to them, for each of these cases saws with different shapes of teeth and sharpening are used. Saws are divided into cross, rip, and mixed saws. The latter can cut both across and along the fibers. For manual sawing of wood, two-handed, bow saws and hacksaws are used. [. ]
Sharpening a Crosscut Handsaw | Paul Sellers
Hollow cylindrical drills are used to obtain through holes or semicircles at the edges of parts, as well as for cutting out plugs. These drills are available with or without a wooden circle ejector. The teeth of a cylindrical saw blade have a profile similar to that of circular saws for cross-cutting with oblique sharpening of the front and rear surfaces. [. ]
Drills for drilling holes. Holes for plugs are drilled with spiral and screw center drills (Fig. 28, a, b) or cylindrical files (Fig. 28, c) with a diameter of 20 and 30 mm, depending on the size of the knot being drilled. Twist drills for wood are made with a maximum diameter of 20 mm. Therefore, for drilling holes with a diameter of 30 mm, twist drills with an angle of inclination of the groove of 45 ° should be used, since in this case the cutting force is significantly reduced and the conditions for placing the chips are improved. The cylindrical saw (Fig. 28, c) consists of a shank 1, a saw 2 with cutting teeth 4, a pusher 3 and a spring 5. The teeth of a cylindrical saw have a profile similar to the profile of saw teeth for cross cutting with oblique sharpening of the front and rear edges. The contour angles of the teeth are equal: a = 30 °, p = 60 °; oblique sharpening angle d) = 25 °. The gap between the saw teeth is 0.2-0.3 mm. [. ]