Why Spread Saw Teeth Than Spread Teeth
Sharpening and setting the saw
The main cutting element of any hand saw. a series of teeth cut into the blade and representing wedge-shaped cutters. Wood, in the manufacture of all kinds of products from it, is sawn along, across and at an angle Θ to its fibers, in this regard, transverse, longitudinal sawing and sawing at an angle to its fibers are distinguished and in each case use the appropriate type of saw, which differs from others in shape teeth.
When crosscutting, cross saws are used, the cutting edges of the teeth of which, when moving in the wood, cut its fibers like a knife and form a cut. Longitudinal sawing differs from transverse sawing in that the direction of movement of the saw is parallel to the grain of the wood. The leading edges of the rip saws cut the wood like knives in planers and, going deeper, form a cut. When sawing wood at an angle Θ, universal (mixed) saws with teeth that are an intermediate form of teeth for cross and longitudinal saws are used to its fibers.
Saw teeth sharpening. a kind of art that requires loyalty of hands, a good eye, and attention. It is not difficult to learn this business, you must have the desire and clearly adhere to the following rules:
- The saw blade must be firmly fixed in a special device made of wood, which is also firmly installed on a well-lit work table. Sharpening saw teeth on stools or on your knees does not give a satisfactory result.
- You should use a personal file, followed by cleaning the sharpened edges of the teeth with a velvet (with a fine notch) or file. It is desirable that the file is new, sharp and with a fitted handle. If at the right time there was not one, then you can use a second-hand one, but it must be brushed with a steel brush and rubbed with charcoal so that the file does not get clogged and does not become dull. When sharpening a tooth, the file should grip its metal and remove its layer depending on the pressure. And if it slides over the tooth without removing the metal, then the saw teeth are overheated or the file is worn out. In this case it is necessary to repeat the sharpening with a new file. If in this case he slips over the tooth, then it remains to take another saw.
- The file handle is clamped with the right hand, and the end of it is held by the left hand and the file is directed to the saw teeth. Working with a file, depending on the type of saw, is described below.
- The pressure of the file on the teeth should be smooth and even and only to one side. When returning the file to its original position, it must not touch the teeth.
- It is necessary to try to grind the metal from the edges of the teeth of at least the same thickness, driving the file the same number of times with the same pressure, which allows you to maintain the angles, pitch and height of the teeth after sharpening.
- Burrs are formed on the edges of the tooth from the side of the file exit, which reduce the sharpness of the tooth, and if they are not removed, then during the operation of the saw they chip out, and the teeth become significantly dull. To remove burrs, the edges of the teeth are sharpened with a file with a velvet notch and deburred from the side edges with a wet donkey.
- After sharpening the teeth, check their sharpness. Look at the tip of the needle and the edge of the razor blade: they are sharp and do not shine in the light. And if they are blunt, then rounded surfaces appear at the tip of the needle and on the edge of the blade, which reflect light and shine well. The quality control of saw teeth sharpening is based on this principle. To do this, place the saw in front of your eyes and examine its teeth along the blade. If their cutting edges and tops are not shiny, then the saw teeth are sharpened satisfactorily, and if some of the teeth are shiny (this often happens), then they must be sharpened with a velvet file, deburred and re-check the light reflection from their edges and tops.
Cross saws. The teeth of the cross-cut saws are sharpened using a triangular file with a fine notch with a 60 ° point angle.
To sharpen the teeth, the saw is clamped into a special device that allows its blade to be installed at an angle of 45-50 ° to the plane of the desktop. The file is led parallel to the working table at an angle of 60-75 ° to the saw blade and thus the left edge A1A2B2B1 is sharpened in the first tooth.
Saw teeth are sharpened in several stages. First, with a file, they pass along the left edges of the odd teeth located in the far row, adjusting the hands to the same movement. Then they pass the file along the right edges of the same odd teeth, completing the sharpening of the main cutting edges with very sharp peaks. After finishing the sharpening of the odd teeth, the saw blade in the sharpening device is turned over and thus the even teeth that are in the far row are sharpened. When sharpening the teeth of cross-cut saws, it is necessary to carefully ensure that sharp main cutting edges with a dihedral angle φ = 60-75 °, a short cutting edge and a sharp point are obtained in each tooth.
Longitudinal saws. Rip saw teeth, in which the angle π
Wood and metal processing
For a flat steel saw to move freely in the cut, its serrated edge must be wider than the bearing part of the blade. This is achieved by setting the saw teeth or flattening followed by shaping. In the sawmill industry, the most common flat saws with set or crimped teeth.
The spreading of saw teeth consists in alternately bending them to one side and the other. Bevel teeth are bent outward with a sharpened side cutting edge. This method of broadening the saw blade is an easier way to prepare circular, frame and band saws, as well as various special and hand saws for work.
For teeth with an oblique sharpening, as well as with a pitch of less than 16 mm, the cutting part is broadened only by divorcing. When spreading by a simple bending of the teeth to the side, the resistance against settlement of the broadening of the saw crown in the first period is insufficient. In such saws, already in the first meters of the cut, the divorce quickly decreases on average by 0.05. 0.1 mm, and then it stabilizes and occurs rather slowly.
During sawing, the set teeth of the saw are elastically deformed under the influence of the lateral components of the cutting forces. Considering this, the set of teeth on the side is assigned approximately 0.1 mm more than the size of the crimping. For saws of all shapes and sizes, the gap should not be more than half the thickness of the sawtooth. Otherwise, a non-overlapping of the divorce occurs, leading to the formation of an uncut wedge at the bottom of the cut, which worsens the conditions and quality of sawing. The simplest and at the same time the most common tool for setting saws is the slot setting, which consists of a handle and a working part with one or more slots for saws of different thicknesses.
When working with manual setting, it is advisable, bending the tooth, while slightly turning the front edge towards the bend. This increases the resistance of the tooth against upsetting and allows a good cut quality to be achieved. saw tooth bend line should be perpendicular to the bisector of the taper angle.
complex setups are equipped with adjustable stops that allow the teeth to be bent in an elastic state by the same amount. Wiring is also used in which the gap is adjusted.
The semiautomatic device RPK.8 is used to set the teeth of circular saws with a diameter of 160. 800 mm. The high accuracy of setting the teeth (± 0.05 mm) of the saws is achieved due to the use of the method of re-spreading in it, the essence of which is that the saw teeth are initially set to a large value, and then bent back to a predetermined level. Counter-spreading pin trims soft saw teeth that project wider.
The semiautomatic device includes a mechanism for feeding, clamping and spreading saws and is arranged as follows. A support with a saw attachment center is installed on a hollow single-column cast bed. The caliper is adjusted to the saw diameter using a handle connected by helical gears with a helical pair installed on the back of the caliper. An electrical cabinet is located inside the bed, on it is an adjustable head with a worm-type gearbox and mechanisms for feeding, clamping and spreading the saw, as well as an indicator-type mechanism for controlling the size of the divorce. In the right front part, the adjustable head, there is a control panel, in the front lower part there is a screw for adjusting the clamping mechanism to the thickness of the saw to be adjustable, above and to the left are indicators (control of the size of the divorce). Indicators can be locked with a lever installed on the left side of the adjustable head. In the upper left part of the adjustable head there are screws for adjusting the size of the bend of the saw tooth and the back (calibrating) spin.
The screws are connected to linkages driven by two radial cams. The symmetry of the divorce is adjusted by adjusting screws.
The saw feed mechanism is housed in a box-type housing and is driven by an end cam mounted on the end of the camshaft. The screw is used to adjust the pitch of the retracted saw, and the screw is used to adjust the position of the tooth relative to the adjustable pins. The handwheel of the manual camshaft drive is used to adjust the machine and control the set of teeth. When removing the saw from the machine, the clamping blocks are unclasped using a handle mounted on the left wall of the adjustable head. In this case, the camshaft of the machine must be in the position corresponding to the end of the set-up cycle (clamping wedge raised).
Crimping and forming consists in the increase in thickness (transverse deformation) of the tops of the saw teeth as a result of the action of the crimping roller on them and their subsequent reduction with forming dies.
SADA & STRAUMANN GROUP: Implant Failures. Dr Corlene SchnetlerMy Webinar
Crimping differs from divorce in a number of advantages. So, the simultaneous formation of both sides of the cut by each tooth and the symmetry of their loading during operation allow, with the same processing quality, to choose for saws with crimped teeth an increased feed (by 30. 50%) and a smaller blade thickness (by 10%) than for saws with set teeth. However, flattening is used only for longitudinal sawing with saws with straight teeth sharpening.
The broadening of saw teeth by crimping is performed as follows. The saw tooth is installed between the crimping roller and the anvil so that the rear edge of the saw tooth rests against the anvil, and the front edge touches the working profile of the roller at the point of the smallest radius. In this position, the tooth is fixed and the roller is turned, which, by smoothly increasing the radius of the working profile, is introduced into the front face of the tooth and causes its widening. Then the crimped tooth is given the correct geometric shape by molding (crimping) or abrasive and sharpened along the profile.
Semiautomatic device PKhF.3 is intended for cold crimping and shaping of teeth of frame and container saws of all standard sizes in accordance with GOST 5524-75 and 10482-74, as well as round ones in accordance with GOST 980-80 with a diameter of 300. 900 mm and a thickness of up to 3.6 mm. According to the general layout, the semiautomatic device is a two-section rectangular parallelepiped, its lower section is a box-type frame, to the rear wall of which a hydraulic station is attached. A table is mounted on the front wall of the bed, on which height-adjustable devices are mounted with one or another tool (frame, circular or container saw).
A second section of the same type is mounted on the bed. Inside and in front of it, the following main mechanisms of the semiautomatic device are installed: turning the crimping head, crimping, clamping and shaping the saw teeth. The mechanisms are closed with a fence. The saw feed mechanism is mounted on the right wall of the second section, the control panel is on top, and a cabinet with electrical equipment is attached to the back wall.
The semiautomatic device is arranged as follows. A frame, circular or container saw is installed in an appropriate device fixed on the machine table. In this case, the table is in the lowest position. The table with the saw is lifted into the crimping and forming area by means of a drive with an electric motor and a V-belt transmission. The screw pair drives the table with the fixture and the tool to be processed. Manual adjustment of the table with the tool according to the lifting height is carried out by rotating the handwheel after pressing it in the axial direction and engaging the bevel gears.
What’s the gary shadow on my tooth Premolar Series 2 of 3
After turning on the semiautomatic device, the hydraulic cylinder rod with the pawl mounted on the rod moves to the left. The tip of the pawl rests against the front edge of the tooth and sets the saw to the starting position for flattening. To prevent the saw from being thrown forward by inertia, it is braked by a block with a spring and a block, adjustable to the thickness of the saw with a screw.
This is followed by simultaneously two movements of the mechanisms of the semiautomatic device. The hydraulic cylinder rod moves to the left, lowering the lower end of the lever and through the shackle. the conditioning and forming head. At the same time, the feed dog under the action of the hydraulic cylinder rod returns to the right up to the stop adjustable by the saw pitch.
By lowering the conditioning head, the saw tooth is precisely set into the conditioning position. In this case, the anvil rests on the back of the tooth, and the conditioner roller touches its front edge. The anvil can be adjusted to the crimping height with screws and can be positioned on the clearance angle of the saw tooth.
The saw is clamped when the hydraulic cylinder rod is raised, which is connected by shackles to the levers. The lower arms of the levers, acting on the screws and rods of the clamping blocks, clamp the saw blade.
Tooth crimping occurs when the roller is turned by levers, under the action of the hydraulic cylinder rods. The roller is adjusted to the required rake angle of the saw tooth with face-toothed couplings. Screws are used for the longitudinal movement of the conditioning roller when its working profile is worn. The roller is returned to its original position by the rods, the hydraulic cylinders simultaneously with the unclamping of the saw blade, by the hydraulic cylinder rod.
Preparation for shaping the saw tooth begins with moving the hydraulic cylinder rod to the right, turning the lever and lifting the head by the shackle to the shaping position. In this case, the rods of the forming mechanism will be located coaxially with the screws 8, 23 of the clamping mechanism.
During molding, the clamping mechanism under the action of a hydraulic cylinder with a rod presses through the rods, onto the dies and produces plastic deformation of the flattened tooth tip, creating the required lateral angles and widening of the gear rim (on both sides). The widening on each side of the saw blade can be adjusted by offsetting the dies. To do this, preliminarily loosen, and after adjustment, tighten the screws securing the dies.
In automatic mode, the operating cycle of the semiautomatic device is repeated until the processing of the last (set by the counter on the control panel) saw tooth is completed.
The semiautomatic device is prepared for operation in the following sequence.
The clutches are unlocked, the crimping roller is turned and adjusted (on a scale) to the rake angle of the saw teeth, after which the clutches are tightened with locknuts.
The screws are loosened and the anvil is adjusted (on a scale) to the rear angle of the saw teeth, after which the anvil is fixed in the required position (with screws). The gap between the anvil and the cylindrical surface of the crimping roller, adjusted by the screw, should be 0.1. 0.15 mm.
Shaping dies are adjusted and fixed with screws only if it is necessary to change the widening of the saw teeth on each side.
They work on the machine in the following sequence. The tool to be processed is installed in the device, fixed on the table, and the saw lifting limit switch is turned on. The circular saw is displaced relative to the table to the left along a horizontal guide and, after adjustment, returns to its original position.
After that, the electric motor for lifting the table with the tool being processed is turned on from the control panel. The exact adjustment of the lifting height of the tool is done with a handwheel, and the thickness of the saw to be processed. with the screw handwheel. With the handle, with the hydraulic station turned off, adjust the pitch of the saw teeth on the scale. After adjustment, the adjusting screw is tightened with a lock nut. Using the handwheels of the screws, the scales are adjusted in accordance with the thickness of the saw being processed. Access to the screws is provided by turning the shaping head guard to the left and removing the shield on the right wall of the upper section of the machine. After adjusting the screws, tighten them with locknuts. Switching on the hydraulic station from the control panel, the pressure gauge is controlled at the hydraulic station. By adjusting the throttle, the pressure in the hydraulic system is brought to 4 MPa.
The switches of the type of work (on the control panel) are set to the positions “Adjustment”, “One tooth”, “Crimping with forming”, turn on the machine and perform control processing of one tooth. Check the quality of crimping and forming and, if necessary, adjust the machine additionally.
The switches are set to the positions “Cycle”, “Group of teeth”, “Crimping with forming”, the counter sets the number of teeth on the saw and turns on the machine for automatic operation. When all teeth are finished, the machine automatically shuts down.
Crimping of saw teeth in the mode without forming is used only in the case of their subsequent surfacing with stellite.
When working on a conditioning machine, it is important to select the correct diameter of the conditioning roller. The size of the roller is chosen depending on the pitch of the teeth of the saw being processed. At a step of 16 mm, a roller with a diameter of 8 mm is used, at a step of 22 mm. with a diameter of 10 mm, at a step of 26 mm and more. with a diameter of 14 mm (for saws with a thickness of more than 3 mm. a roller with a diameter of 16 mm).
To control the size of crimping and spreading, indicator-type or lever-type water meters are used. The basic elements in these devices are the protrusions of the reference platform, the measuring rod is the heel of the measuring rod, connected with the lever mechanism and the hand or with a standard dial indicator. When checking, the measuring heel should touch the tip of the tooth, the base pads should fit snugly against the side surface of the saw. Before starting work, the water meter is verified on the control plate.
Standardizing the size of spreading and conditioning is the most important condition for high-quality and high-performance sawing with optimal consumption of wood and cutting tools.
The widening of the saw teeth to the side depends on the physical and mechanical properties of the wood, its moisture content, the season, the equipment used and its condition. When sawing harder wood, as well as frozen wood, the spreading (or crushing) should be less. For soft, fibrous and damp wood, in which the ability to resilient fiber recovery is more pronounced, the broadening of the saw teeth on the side should be greater.
The recommended widening of the saw teeth on each side by the method of spreading or flattening followed by shaping for circular and band saws is given in the appendix to GOST 980-80, 6532-77 10670-77. When sawing softwood for saws in accordance with GOST 5524-75, the broadening of the tops of the teeth to the side after molding should be (0.65 ± 0.05) mm at any time of the year at an absolute humidity of 30%. For saws in accordance with GOST 10482-74 for similar sawing conditions, these values should be respectively (0.35 ± 0.05) and (0.5 ± 0.05) mm.
How to sharpen a saw and set its teeth correctly?
The hand saw is truly one of the most indispensable tools on the farm, but even the best saw dulls over time. Sharpening it yourself is not at all difficult, you do not need to have any special skills for this. you just need to strictly follow the recommendations. For sharpening you need the following tools:
Sharpening a hand saw for wood.
- File (flat and round).
If the saw is sharpened correctly, then there is no doubt that it will function properly. However, saws that are designed for woodworking not only become dull over time, but often go dull on sale. This situation is especially true for those tools that have large teeth. Thus, for those for whom the efficiency of the saw is an important issue, sharpening must be taken care of in advance.
How to sharpen and raise a saw correctly
In this case, when engaging with the workpiece, fewer teeth are involved in the sawing process, while the pressure increases and the saw performs better.
Figure 51 shows the sequence for preparing the hacksaw for work.
The handle is of great importance. It can be wooden or plastic, as long as it is comfortable to hold in your hand. The stamped iron handle is very inconvenient in work. the hand gets tired from it faster, calluses are formed.
When storing the saw, it is better to put on a lengthwise cut of a hose or PVC tube on its teeth.
To prevent the saw from getting stuck in the wood, its teeth must be spread apart. bent one through one to the left and right. As a result, the kerf is slightly larger than the thickness of the saw blade, so it does not get stuck in the kerf.
There is a special tool for cutting the saw. wiring. with which the saw teeth are bent to the sides by about 0.5 mm (Fig. 52).
In this case, the set of teeth on each side must be the same. If, after setting, individual teeth turn out to be bent more than others, they are corrected. they are bent into one line with the rest. If the teeth are different in height, then before sharpening they are leveled with a file (Fig. 52, b).
You can also set and sharpen the teeth of a hacksaw using a vice, pliers and a triangular file with a fine notch (fig. 53).
First, with the help of a wooden spacer, the canvas is fixed in a vice and with pliers they begin to carefully move the tops of the teeth alternately in one direction or the other (Fig. 53, a), but not more than half the thickness of the canvas. A wider cut will only hurt, as the cut will be too wide and uneven. It is also necessary to ensure that the set of all teeth is the same, otherwise not all teeth will participate in the sawing process, but only the most bent ones and it will be difficult to work with such a saw. The set teeth must be within the spacer, so the position of the blade changes from time to time.
The saw is sharpened with a triangular file. The blade is clamped in a vise and moved as the teeth are sharpened. There are two types of sharpening. oblique and straight.
If the saw is intended for mixed rip-and-cross sawing and its teeth are in the shape of a right-angled triangle, a simpler straight sharpening is used, during which the file is held perpendicular to the blade (Fig. 53, b).
Inserting it alternately into each gap between the teeth, with light pressure, it is carried out along their edges in the direction away from you. In this case, the edges of the file must fit snugly against the edges. The reverse movement is performed by raising the file so that it does not touch the saw. It is not worth driving a file in the same place for a long time, it is enough to walk over each tooth 3 times, and with repeated sharpening, one will be enough.
From the book: Korshever N.G.Wood and glass works
How to sharpen a hand saw
After the divorce, the saw must be sharpened. For this procedure, no special equipment is required; here you can do with an ordinary triangular file. The sharpening technique with this tool is as follows. The file is taken with one hand by the handle, the other by the tip of the tool and moved away from you, pressing the teeth smoothly and evenly, then in the opposite direction, without touching the teeth. Handsaw teeth need to be sharpened on both sides, from top to bottom.
After sharpening, burrs can form on the edges of the teeth, which will negatively affect the operation of the tool, chipping and dulling the teeth. They must be removed with a fine cut file.
During operation, the saw becomes dull, so sometimes the teeth are sharpened with an emery bar. Continuous sharpening evens out the setting so that the saw remains in working order, the setting of the teeth must be repeated periodically. However, it is not necessary to overhaul and sharpen the teeth too often.
Hand saw setting methods
It is best to do this on special equipment. an adjustable machine. On it, using an indicator, you can determine the correct deviation of the tooth, so the work can be done in a matter of minutes.
If the machine is difficult to find, you can manually spread the hacksaw. However, it will take a lot of time and effort to complete the procedure, and besides, you cannot do without a special tool. wiring, which you can make on your own. It is a metal plate with a sawn groove 1.5 mm wide and 5 mm high. The saw is clamped in a vice and with this groove the tooth of the tool is grasped and retracted in the desired direction.
This must be done in a specific order. First, the teeth are deflected through one in one direction, then the rest in the other. In this case, there should be no distortions, and the teeth should be unbent symmetrically. Not the entire tooth is bent, but only its tip (that is, its third part), otherwise it may break. The width of the setting should be equal to twice the thickness of the blade, if the teeth are spread too wide, then the hacksaw will go tight, and too much wood will go into the sawdust. In addition, if the setting is incorrect, the tool will “wedge” and an even cut will not work.
You can also spread the saw with a screwdriver or chisel. The tool is placed between the teeth and turned, the saw should also be clamped in a vice before this.
The ways One of the easiest ways to set saw teeth is with pliers. You just need to take each clove and bend it alternately in different directions.
The tooth must be clamped by two-thirds, then the slope will be correct.
As a result of this work, half of the teeth will be bent to the right and half to the left. Another wiring method is carried out using a special tool.
Types of band saws
Band saws vary in tooth size.
Types of band saws
Band saws vary in tooth size. You should also highlight:
- two-handed saws;
- single saws.
Two-handed saws are sharpened and set in the same way as regular single saws. The whole difference between such a tool is that two people work with it at once.
With the help of band saws, wood and varieties of this material are most often sawed. Wood does not require too much impact, it is a soft material that is easy to saw and drill. However, in the process of work, it is still desirable to fix the logs and boards. When cutting, be careful not to keep your hand too close to the cutting furrow. This can lead to serious injury.