How to make a do-it-yourself knife sharpening machine at home and what materials / tools will help in this matter?
Knives in everyday life should always be sharp enough to comfortably perform their functions. When cooking and cutting food, they constantly become dull, as a result of which they need to be sharpened.
To perform this work, many different machines and devices have been invented, ranging from the usual whetstone to complex electric grinders. Using a simple bar is quite inconvenient and takes a long period of time. Exists manual machines to carry out this work.
Manual knife sharpeners
Grinding machines American company Lansky, slightly improved the usual sharpening with a bar. With the help of such a device, you can quite accurately adjust the angle of work with the blade, from 17 to 30 degrees.
Lansky sharpener at work
A similar do-it-yourself knife sharpening machine can be made by any craftsman due to the simplicity of its design, as demonstrated in the video below.
Machines with fixed blades
These devices allow you to sharpen the knife much faster, because they allow you to apply more effort. Moreover, the efficiency due to the presence of a hard stop in the form of a table also rises several times.
SpitJack knife sharpening machine
As can be seen in the figure, in machines of this type, the sharpening bar moves along the fixed blade at a set angle. The sharpening angle is adjusted by changing the height of the bar attachment. Among the domestic analogues of such machines, one can mention the machine manufactured by the Ermak company.
Ermak sharpener
Machine tools with fixed sharpening surfaces
In devices of this type, there is no way to adjust the angle of sharpening yourself. Most often, several different angles for work are already installed on such a device. Using such machines, you just need to run the blade along the sharpening recess.
This recess consists of two planes, one or two of which is a sharpening bar. So in order to sharpen a kitchen appliance, it’s enough just to run the knife over the sharpened surface several times.
Mechanical sharpener Chief's Choice
Electrical Devices for Knife Point
You can also mention the professional tools that are used by most chefs, and it takes only a few seconds for the knife to become as sharp as possible again. These devices have an electric motor that rotates the grinding blades. 
Such canvases are often made with diamond abrasives, and the engine power does not exceed 100-150 kW. Although, of course, there are more powerful machines for sharpening blades that are used in production.
We make a device for sharpening with our own hands
To make a do-it-yourself knife sharpening machine, you will need: a piece of laminate, a wooden rail, sandpaper, and two lamb bots. Instead of laminate, you can use chipboard or plywood.
To make a knife holder, you need to cut off a piece of laminate. So that the bar does not touch the holder when sharpening, you need to clean off its edge at an angle, using emery.
- Marking and cutting upper part a vertical stand on which the bar will rest when sharpening. We choose an angle half that with which the knife will be sharpened, in our case it is 30 °. For kitchen appliances, it is better to use 10–15 °. In total, 2 such parts will be needed.
- In order to correctly calculate the length of the base and the height of the racks, you need to approximately make a design and markup. It should be borne in mind that the further installation of the transverse support will affect the height. After that, we cut off all the details, and clean their edges.
- Now we outline and drill holes in the base and the pressure plate at the same time for the bolts that fix the knife blade. When marking, it is important to maintain the distance of the holes from the edge of the base. This is necessary to ensure the versatility of the installation, since the knives have different blade widths. We fix the pressure plate with bolts.
- Vertical racks can be fixed with screws, but given that the load on them is small, it is better to use hot melt adhesive. In the same way we fix the horizontal crossbar. At this stage, the sharpener is already ready, it remains only to make a bar.
- To make a bar, cut a rail of suitable length. We glue emery with the required size of abrasive on one of its edges, in our case it is P1200. To improve the result, you can make several bars, with different grain sizes. The range P600 - P2000 is considered more optimal. To protect your hands from cuts, it is advisable to screw the handle on the top side of the rail.
- As a result, we get a functional and practical machine for sharpening kitchen knives. During operation, it rests with bolts on the edge of the table, which increases the comfort of use.
Video: how to make a knife sharpener from a piece of laminate?
Often, ordinary abrasive bars are used to sharpen knives at home. But their use requires special practice, since with the wrong angle for sharpening, the result will be disastrous. The blade will not have the proper sharpness, which will require additional processing.
Rules for sharpening knives
Before you start making a homemade device for sharpening knives, you need to familiarize yourself with the recommendations of experts. At the first stage, it is necessary to determine the angle between the working part of the blade and the bar. This can be done individually for each model.
The knife should be located strictly perpendicular to the direction of the bar. The angle in this case can be equal to half the sharpening. This is due to the fact that grooves are formed on the surface of the blade during processing. They appear due to the action of abrasive components. With the minimum graininess of the tools, they will be insignificant. But there will also be a small degree of impact on the knife.
In addition to this factor, when sharpening a knife with your own hands, you should consider:
- the average sharpening angle is 20-25 degrees;
- processing is performed from the beginning of the blade;
- to control the sharpening angle, you can paint over part of the blade with a marker. In this way, the actual area of influence can be controlled.
It should be remembered that the deformation along the entire length of the working blade will be non-uniform. Therefore, when doing sharpening with your own hands, the “report point” should be the bluntest part of the knife.
The resulting grooves due to the impact of the bar must be strictly perpendicular to the line of the knife. This is the main condition correct sharpening.
The choice of whetstones for sharpening knives
The main component of a homemade sharpening machine will be a bar. This is an abrasive material that, when exposed to the blade, thins it, increasing its sharpness. Therefore, before choosing a design, you should choose the right bars.
The main indicator of the bar is the grain size, but the dimensions should also be taken into account. Ideally, the length of the tool should be no less than the length of the knife. This will ensure uniform processing, reduce the likelihood of defects.
To sharpen knives with your own hands, you will need the following types of bars:
- high graininess. With their help, primary processing takes place, the shape of the blade is corrected;
- medium grit. They are designed to remove the grooves formed during the first operation;
- whetstone or leather belt rubbed with GOM paste. This stage is called polishing or finishing the blade.
The main task of drawing up a design diagram is the correct location of the bars. Therefore, we will consider several options for fixing them relative to the knife blade.
For sharpening ordinary kitchen knives, two types of whetstones will suffice - with high and medium grit. Additionally, they will need a donkey.
Simple version of the machine
The simplest version of the machine design is two pairs wooden slats interconnected with adjustable screws. A bar is attached between these components.
The main condition in the manufacture of this design is stability. During operation, it should not change its location on the desktop. For better fixation of the bar, it is recommended to provide support strips located between the wooden components.
Despite the ease of manufacture with your own hands, this machine has several disadvantages:
- the blade is set manually relative to the stone. During prolonged work, it is not always possible to control the sharpening angle;
- an additional fixing unit is required. Since the design must be stable, it is researched to fix it rigidly on the desktop;
- during operation, the screeds can loosen, thereby changing the location of the bar.
The main advantage of this scheme is the ease of fabrication. The design is suitable for sharpening kitchen knives at home. As additional components, you will need a touchstone.
The thickness of the wooden slats can be different. Actually for self-manufacturing such a design, you can use any improvised materials.
Manual sharpening machine with bar adjustment
To achieve the best result, it is recommended to take the drawings of factory tool models as a basis. Their difference from the instructions described above lies in the rigid fixation of the knife, but this will require great effort to manufacture.
The design consists of support table on which the knife blade is attached. A screw rack is installed in a vertical position. A strap with a slot is attached to it. The sharpening stone is mounted on a guide rod. The sharpening angle is changed by moving the slotted bar along the screw post.
Features of the operation of a machine of this type:
- sharpening angle is set with high precision. Its change depends on the thread pitch of the rack;
- instead of a bar, you can use sandpaper. For this, the base is made of plexiglass. A hole is made along it for installation on a guide rod. Sandpaper is glued to the surface of the plexiglass;
- the support base is best made wide. This will make it possible to fix it with clamps on any countertop.
The main problem with this design is the long adjustment of the sharpening angle. This can affect the speed of work if several types of knives are being processed. Each of them requires a long setup of the machine.
To increase the quality, you can use water or oil. They are applied to the abrasive surface, thereby reducing the impact of the chipped particles of the bar on the blade.
Sharpening machine with knife position adjustment
An alternative manufacturing option for the machine is to change the position of the knife relative to the stone. In general, the design is in many ways similar to the one described above, but much easier to manufacture.
A movable fastening block for a pin with a stone is installed on the base. Two clamps are mounted on the same plane. One of them will be persistent, and the second - adjustable. By changing the distance between the clamps, you can adjust the angle of sharpening.
The main disadvantage of this design is the wear of the bar in one place. To solve this problem, it is recommended to make a long pin to adjust the position of the edge relative to the blade.
In addition to the above schemes, there are a lot of grinding machines that you can do yourself. When choosing the optimal model, one should proceed from the actual availability of improvised materials. It is also recommended to analyze factory machines. Often they are the basis for the manufacture of a unique design.
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To maintain the cutting properties of the knife, it is necessary to sharpen them regularly, and a do-it-yourself knife sharpener will help keep these tools in proper condition. With a good sharp knife, cooking is greatly accelerated, freeing up additional time for rest. V this material we will consider the manufacture of special devices for quick and high-quality sharpening of knives.
When the knife is factory-made, it is given the necessary sharpness. However, with frequent use, it gradually loses its cutting properties. To make a knife sharp again, you need to sharpen it, but doing it right is not so easy. Improper sharpening will not give the desired result, and time and effort will be wasted.
Knife makers have responded to requests from their customers by providing a range of sharpeners. But factory fixtures may not suit knife owners for various reasons. For example, an inappropriate sharpening angle or the high cost of the device. In this case, it is easier to make a sharpener with your own hands.
What you need for proper sharpening
The most important condition for obtaining sharp knife is the angle of its sharpening. It would seem that the smaller this parameter, the sharper our tool will be. This is partly true, since a cutting edge that is too thin will wear out and dull faster.
The sharpening angle depends on the functional use of the knife:
- Up to 15 degrees - shaving and surgical instruments.
- Up to 20 degrees - devices for cutting vegetables, fillets or bread
- Up to 25 degrees - knives of multidirectional functionality.
- Up to 30 degrees - hunting and tourist knives.
- Up to 40 degrees - cutting tools for special purposes. For example, axes or machetes.
Outcome! The whole process comes down to restoring the cutting ability of the tool, while maintaining the factory sharpening angle. Violation of the angle can lead to deterioration of the knife.
Sharpening devices
It is very difficult to sharpen a knife at a certain angle without special tools, and not every professional can do it. They can be purchased in specialized stores, or made by hand. Below we will look at a few simple and affordable devices that allow you to sharpen most household cutting tools.
A simple wooden block machine
This method is considered the easiest to manufacture and use. Sharpening material securely fixed at the desired angle, and sharpening is carried out by holding the knife blade strictly vertically.
To make a simple knife sharpening tool, you will need:
- Four identical wooden blocks.
- Bolts and nuts for connecting bars to each other.
- Sharpening bar.
- Protractor for determining the angle of sharpening.
- Drill or other tool for drilling holes in wooden blocks.
The bars are connected in pairs, and through holes are drilled through them for fastening with bolts. Pairs of bars are installed perpendicular to each other at an angle of 90 degrees. A grindstone is installed between the parts of the structure at the required angle, measured with a protractor. The nuts on the bolts are tightened, tightly fixing the abrasive.
The advantage of this device lies in the relative cheapness of materials and ease of manufacture. Everyone can cope with it, even without the appropriate experience. The main disadvantages include the impossibility of smoothly adjusting the desired angle.
Grinding machine from mounting brackets
This turning method is considered the most convenient, however, additional efforts will be required to create such a device. It is based on technology famous company Lansky Sharpeners. You can buy the original machine in company stores, but its cost will be quite high. Below we will look at how to make a similar mechanism yourself.
To assemble the structure, you will need the following materials and tools:
- Two metal corners with dimensions of 90 × 90 mm and a thickness of 6 mm. They are the basis of the mechanism that holds the knife blade.
- A metal hairpin with a thread with a total length of at least 16 cm. It will be the basis for holding the whetstone.
- Two metal bars needed to fix the abrasive.
- A thin long rod or knitting needle.
- Pliers. Required for bending.
- Saw for working with metal.
- Tool for processing metal surfaces.
- Nuts and bolts for fastening and fixing.
- Drill and a set of drill bits for metal.
Having bought necessary materials in a specialized store, you can begin to assemble the structure. Make without drawing correct design will be practically impossible, since it is necessary to comply with all dimensions to obtain right angle sharpening. To do this, use the drawing below.
V metal corners holes are drilled according to the drawing attached above. The edge of the corner that will hold the blade is thinned by grinding. This is necessary so that when sharpening the knife, it would not be a hindrance. All drilling sites are processed to remove all possible traumatic places.
In two metal bars, a thread is cut to the diameter of the connecting pin and grooves in which the abrasive will be attached. The clamp diagram below will help you quickly and without unnecessary difficulties to assemble it.
A metal rod or knitting needle on one side is bent with pliers. The bent end is inserted into the hole of one of the bars. Its purpose is to guide when turning to set the desired angle.
The principle of turning on this device:
The main advantages of this machine are compactness, simplicity and efficiency of sharpening, the ability to select and fix the angle. The device can be held in the hands, or installed using the holder in a vise. This allows you to take it with you on a hike and use it in the field.
Among the shortcomings, it is worth noting the limited set of angle parameters and the inability to set an arbitrary value.
This video details how to make a do-it-yourself knife sharpener using the Lansky system:
Blade locking machine
This method is a modified version of the previous method. The knife is fixed on the base of the machine, and its owner himself adjusts the turning angle. At the same time, the compactness and mobility of the machine are lost. It can only be used at home.
To make such a device you will need:
- Sheet plywood or chipboard. You can use parts from old furniture.
- Threaded pin. It will act as a tripod.
- Bar of solid wood.
- A metal plate for attaching and holding a knife blade to the base.
- Mounting Consumables- nuts, bolts.
The assembly of the structure begins with the preparation of the base. We make the base and legs from wood. They are cut so that after their connection, the slope of the base is 20 degrees. A threaded stud is installed in the lower part forming a tripod. For additional strength, all places can be treated with a sealant or a special adhesive.
A metal plate is installed in the center of the base. First, you need to drill a hole in it corresponding to the hole in the base of the machine. Through it, the plate will be pressed against the plate, and thus the knife blade is held.
It is recommended to purchase an aluminum plate, as it will not damage the blade when squeezed hard. Also suitable for this purpose rubber gaskets, reducing negative impact metal to metal and increase the coefficient of friction, which prevents accidental displacement of the blade during the point.
The fastening mechanism for an emery stone is made from the rest of the hairpin and two wooden or metal bars. Holes are drilled in the bars to fit the size of the stud, fixed with nuts on both sides. The fixing of the stone will be carried out by tightening the nuts. This process can be simplified by improving the holder with a spring on the side of the handle.
To set the sharpening angle, you will need two wooden bars fastened together by a hinged mechanism. In one part, it is necessary to drill a vertical hole for the diameter of the stud. With this part, it will be put on a tripod, adjust the sharpening angle and at the same time be a rotary mechanism along the horizontal axis.
Drilled out in the second part horizontal hole slightly larger diameter. A pin with an emery stone will move in this hole, so it is necessary to completely eliminate the possibility of getting stuck.
Sharpening order:
The main advantages of this method are the ability to set any angle of sharpening and the quick replacement of the abrasive element. Such homemade machine will help bring any blade to perfect condition.
The disadvantages include relative bulkiness and increased manufacturing complexity. Some parts may require special tools to make.
If you still have any questions about the installation and use of this device, then this video will help you fully understand the essence of the process:
Choice of abrasive element
An important role in sharpening blades is played by a whetstone. Most often, to determine the roughness of the abrasive, a system of digital designation of grains per unit of measurement is used.
Depending on the functional need, the following gradation is distinguished:
- Up to 250 - rudeness is high. It is not used for sharpening knives and other cutting tools.
- Up to 350 - coarse abrasive. It is used to correct physical defects or very dull blades.
- Up to 500 - medium abrasive. Used for fitting instruments. It has little demand and is rarely used.
- Up to 700 - fine abrasive. The most used type of sharpening tool in everyday use. Allows you to sharpen the blade to an acceptable sharpness.
- Up to 1000 - ultra-fine abrasive. Suitable for grinding surfaces and bringing already sharpened tools to perfect sharpness. Not effective for sharpening dull knives.
Thus, if you want to sharpen your cutting tools with maximum efficiency, you need to combine different types abrasives. For example, especially blunt knives are brought to an acceptable state with coarse stones, then sharpened with a fine abrasive. At the end of the process, grinding with ultra-fine stones is carried out.
Emery also differs in its origin:
- Natural. These include the Japanese water stone, which requires special skills and great patience to work with.
- Diamond. The most resistant to wear and varied in roughness. The most effective and relatively cheap.
- Ceramic. They are considered something in between, between stones of natural and diamond origin.
- Artificial. They differ in their cheapness, but with frequent use they quickly become unusable.
There are many ways to sharpen knives. modern industry, promptly responding to the requests of professionals and just private craftsmen who want to use quality tool, has developed and introduces into production special grinding devices.
With the help of a homemade knife sharpener, you can sharpen a knife at any angle, since the sharpening angle is adjustable independently.
But it happens that the factory device, for one reason or another, does not suit the customer. In this case, you can make a device for sharpening knives with your own hands. It will most likely be much cheaper and, it is possible, much more convenient for its creator.
Necessary condition for the correct sharpening of knives
The purpose of any sharpening of a dull tool is simple and clear at first glance. But making the knife sharp is only part of the solution. The most important factor for long and efficient operation of the product is the angle of sharpening.
Figure 1. Cross section of the blade: 1 - cutting edge (RK), 2 - supply, 3 - sharpening angle, 4 - descent, 5 - butt.
The significance of this factor can be assessed in practice. It would seem that the smaller we make the angle between the edges of the blade, the sharper the knife becomes. But such an action leads to the fact that our object will not be able to demonstrate its improved cutting qualities for a very short time. Moreover, the sharper the knife is, the faster it becomes dull, since a direct pattern appears here - the smaller the sharpening angle, the less strength the cutting edge of the blade has.
Thus, the task of high-quality sharpening of knives is reduced to restoring the sharpness of the blade while maintaining the correct sharpening angle. In a sense, sharpening is the process of restoring a previously set angle. And it can be considered correct in the case when it fully complies with certain technological standards and most effectively, freely and quickly cuts the material for which the knife is intended.
Therefore, each blade is sharpened at its own optimal angle for it.
However, it is generally difficult to do this without having a special device. The fact is that, holding the knife with your hands, it is difficult to ensure uniform sharpening with the given angles of inclination of the cutting edges.
To eliminate this problem, there are special tools for sharpening knives that you can make yourself. It is worth noting that usually their designs, despite the great variety, do not differ in any way. increased complexity, and the manufacture of such devices takes relatively little time.
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Materials and tools needed for sharpening knives
The following blanks and tools will help to make simple and quite solid adaptations:
- wooden bars;
- a set of abrasive bars (musats);
- hacksaws (for metal and wood);
- electric drill;
- chisel;
- files;
- plane;
- clamp;
- a set of various sandpaper;
- marking devices;
- screws, nuts.
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What are sharpening devices: a few examples
It is quite difficult to describe in detail all the grinding devices that exist today. Let's dwell on some of the most characteristic and common.
The first fixture is made from two wooden and two abrasive bars of the same size. All burrs should be carefully removed from wooden blanks with sandpaper. Then, depending on the required angle of sharpening knives, a preliminary marking of wooden bars is made. To do this, a corresponding line is drawn on the bar.
Methods for sharpening knife saws: a - jointing of the saw teeth (1 - file, 2 - block, 3 - saw blade), b - soldered the sinuses with a hacksaw to a shallow depth, c - setting the saw teeth, d - sharpening the saw teeth (1 - rubber pipe , 2 - rubber safety cover, 3 - wooden clamp, 4 - vise).
Further, a whetstone is applied to the intended line in order to fix its width on the wood. On the opposite side wooden block according to the principle of mirror reflection, the corresponding lines are applied.
On the marked lines on both wooden bars cuts are made with a depth of 1 cm to 1.5 cm. Bars of abrasive material are inserted into the recesses thus obtained. When performing these operations, you need to make sure that all the grooves coincide with the grindstones. After that, the abrasive elements are fixed with bolts. In order for the resulting sharpening device to be stable and not slip on the desktop, a piece of rubber can be attached to its lower surface.
The second device is based on the principle vertical arrangement knife blade. In this case, the blade being sharpened will move along the abrasive bar, which is fixed at a certain angle to the horizontal and vertical surfaces. As practical experience shows, keeping the blade in a vertical position is much easier and more functional than driving the blade along the horizontal plane of the abrasive bar, while trying to maintain a given sharpening angle.
This device is very easy to make. To do this, you need to take a pair of ready-made, identical in size wooden squares. You can also make such square blanks yourself, providing strictly right angles in them. In several places of both squares, holes are drilled symmetrically, into which clamp screws are inserted.
Then it is necessary to mark the horizontal and vertical bars with a centimeter scale. According to it, the angle of inclination of the abrasive bar will subsequently be set. After setting the desired angle, the sharpener is rigidly fixed in the device by means of clamping screws.
Using this type of device in his practice, the grinder will have to make friends with trigonometry. With the help of its formulas, it will be possible to accurately determine at which points of the horizontal and vertical bases of the square the edges of the abrasive bar should be fixed. So, for example, with a sharpening angle x = 30 °, the horizontal extension of the bar should be 4 cm, and vertically - 15 cm.
The third version of the device for sharpening knives considered here is somewhat similar to the previous one. In this case, it is made wooden base, on which two side and one central lining are then placed. They are also made of wood, so that it is easier to cut their side edges at the angle that will be needed for high-quality sharpening.
This option involves the rigid fastening of two side plates on the base and a removable (with a screw) central plate. This pad will act as a clamp for the bars. The mating inclined faces of the side and central elements must have the same cut angles.
Thanks to this, it will be possible to clamp the bars at the required angle for sharpening. But, unlike the previous version with square clamps, this method does not involve smooth adjustment of the angle of inclination of the grindstone. Therefore, it is possible to sharpen the knife blade here only in two rigidly fixed positions.
The following device is based on a principle that is directly opposite to the two previous options. In this case, it is not the abrasive bar that is rigidly fixed, but the workpiece to be sharpened. The sharpening element is mounted on a sufficiently long rod.
With its supporting side, the bar is attached to the vertical rack. In this case, the connection of the rod with the rack should provide free horizontal movement of the bar together with the rod in different directions. Defined is set by the height at which the movable bar is fixed on the vertical stand.
Interest in making knife sharpeners with your own hands arises for a reason. The consumer qualities of a hand cutting tool are enhanced by the use of modern materials and technologies for blade manufacturing and precise factory sharpening. At the same time, the price of the product is also growing, but it is becoming easier to spoil a fairly expensive thing with primitive sharpening. Therefore, various household appliances for sharpening knives are needed not only for convenience. To figure out why a knife sharpener is still needed and how to make it right, you have to start with the ideology and evolution of the knife.
Why you need a sharpener
A living relic of our days is a Finnish hunting knife. Not a bandit finca, sometimes of a bizarre shape, but a Finnish-type hunting knife, on the left in fig. Traditional hunting knives (center and left) are similar in shape to it, but the difference between them is very large.
The blade of a Finnish knife is forged from bloomery iron, which can be smelted right in your yard from swamp ore in a domnitsa furnace, without resorting to the blast furnace process, puddling, and other methods of converting cast iron into iron and steel. The viscosity of bloom iron is excellent, it is very difficult to break a blade from it. But the hardness is also low, somewhere around HRS55, the knife gets dull pretty quickly. Finnish hunters did not care: a blade of such hardness can be directed (sharpened) by beating on many natural stones, and smoothed moraine boulders in Fennoscandia have always been enough.
They sharpen the knife with a beating in much the same way as they beat off a scythe, only the touchstone is motionless, and the blade is moved. First, he is pulled along the donkey with the butt away from himself, then he is turned over and pulled with the butt towards him. The position of the cutting edge (RK) on the touchstone is always dragging; the movements are fast: shirk-shirk! On each movement, you need to keep the contact patch of the blade with the touchstone (see below), but the requirements for maintaining the angle of inclination are not so strict. Learning how to sharpen a knife with a bevel is not very difficult, and with some skill, you can also aim a smoothly running profile at the blade, see below. However, the Finnish knife is, in general, a dead end in the evolution of a cutting tool that has survived in special natural conditions.
A good knife has never been cheap, but in extreme situation the durability of the blade, combined with the toughness of the blade, became vital circumstances. Therefore, even in ancient times, knife blades learned to be hardened from the surface and cemented: the core remained viscous, not brittle, and a hard, hardened crust formed on the outside, see next. rice.:
It is still possible to direct a knife with a cemented blade with a beating, but a skill is needed that is not given to everyone. And the abrasive is already needed from a special breed of stone - lithographic grunstein shale. It is scarce in nature; grunstein is still considered a strategic raw material. There is no artificial grunstein and is not expected. To spoil a cemented knife with an inept chop is as easy as shelling pears - a little somewhere, the cementation bark will be torn off to raw metal (this is not visible to the eye), the knife will only be thrown away, the blade will immediately become dull and will crumble.
Note: if you have an old slightly greenish scythe touchstone lying around somewhere, do not throw it away, it is a valuable rarity.
Knife blades don't need the toughness and toughness of hunting and camping knives, and they should cost a lot less. As a result, special steels and powder metallurgy are widely used in the production of home knives. The blade of the "eternal" kitchen knife is structured like a rodent cutter: in longitudinal layers, the hardness of which decreases from the core outwards. In any case, you have to sharpen the knife less often, but the beating is definitely excluded - the blade from it immediately crumbles.
How do you sharpen a knife?
For these reasons, the push-pull sharpening technology (push-pull sharpening or push-pull sharpening technique) has long been invented:
- The blade is pushed along the touchstone away from oneself with a twist, holding the butt towards oneself, the position of the RK is running (scraping);
- Then, without tearing the blade from the touchstone, pull it with the butt towards you with a twist in the opposite direction, the position of the RK is dragging;
- The blade is turned over and repeat paragraphs. 1 and 2;
- Pp. 1-3 are repeated, in each cycle reducing the pressure, until the burr formed on the RC comes to naught (does not stick together).
Note: when they say or write “the burr will go away”, etc., this is not true. Metalheads have a slang word for slang; electricians have a “switch”. But in Russian, a burr and a switch are masculine.
Push-pull sharpening saves the blade, but requires high skill from the operator, because. during the sharpening process, a number of conditions must be continuously and precisely observed, see also fig. below:
- Maintain the angle of inclination of the blade to the touchstone, smoothly changing it in accordance with the curvature of the RK.
- Make sure that the tangent to the generatrix of the blade and the transverse axis of the contact patch of the RC with the touchstone coincide.
- Also make sure that the axis of the contact patch is always perpendicular to the longitudinal axis of the touchstone.
- Smoothly change the pressure on the blade as the area of the contact patch changes.
It is very difficult to comply with all these conditions at the same time, completely symmetrically on the forward and reverse stroke of the blade along the touchstone, and a modern knife, as mentioned above, can be damaged by improper sharpening. Any household knife sharpening device is designed to save the grinder from continuous control of at least part of these conditions.
Note: for successful push-pull sharpening, the length of the whetstone (see below) must be at least 2 lengths of the knife blade from shank to tip.
Sharpening profiles
The profile of a knife blade is linked to the properties of the material and the structure of the blade, as well as to the properties of the materials for which the tool is intended to be processed. Sharpening on a simple blunt wedge (pos. 1 in the figure) gives a stable but rough blade: cutting resistance is high, and the knife tears quite viscous materials. A sharp wedge (pos. 2) quickly becomes dull or chipped; on viscous and / or fibrous materials, the cutting resistance may be greater than a blunt wedge due to the friction of the cut against the blade.
Ideal in all respects is an animated (smoothly escaping) profile, pos. 3. Experts are still arguing which generator is better - evolvent, hyperbola or exponential. But one thing is indisputable - it is difficult and expensive to make an ogival blade under production conditions, and it is impossible to direct it yourself. Therefore, knives with ogive sharpening are used only in special equipment, for example. microtomes - biological devices for obtaining the thinnest tissue sections.
For disposable blades, e.g. blades of safety razors, faceted sharpening is used, pos. 4, i.e. An ogive generatrix, as mathematicians say, is approximated by line segments. The number of sharpening edges is indicated in the certificate or on the manufacturer's website. For thick coarse bristles, 3-4-faced is better; for delicate hair not on the face - 8-sided. Universal is considered 6-sided.
Angle α
The sharpening angle is always given in half the value of α, because many tools and, for example, bayonet-knives, are sharpened on one side. For knives for various purposes angle α is maintained in the next. limits:
- 10-15 degrees - medical scalpels, straight razors, knives for artistic carving.
- 15-20 degrees - confectionery (for cakes) and vegetable knives.
- 20-25 degrees - bread and fillet knives.
- 25-30 degrees - hunting, camping, survival knives.
- 30-35 degrees - general purpose household knives.
- 35-40 degrees - carpentry tools, shoe knives, axes.
One and a half
Sharpening knives, except for special ones, is done almost exclusively with a one-and-a-half profile, on the left in fig. One-and-a-half sharpening is so named because the flat edge of the blade (descent) is formed during the manufacture of the blade and cannot be sharpened. In fact, guiding a knife with one and a half sharpening is no more difficult than sharpening a simple wedge. One and a half sharpening is optimal for a knife that works with the most different materials, and making a sharpener for knives with one and a half sharpening is much easier than for sharpening a faceted one.
In the center and on the right in Fig. the stages of sharpening the blade and the numbers of abrasives used on them are shown. The abrasive number corresponds to the number of its grains per 1 sq. mm surface. The finishing stage has some features:
- Hunting and camping knives are not brought. So it is easier to cut hard (eg, bones) with a broach (with filing) with them. In addition, if you accidentally cut yourself, then a slightly lacerated wound stops bleeding faster, heals more easily, and there is less danger of infection entering it.
- The blades of dangerous razors, shoe knives and for artistic carving after abrasive are brought to a mirror smoothness on a leather whetstone with GOI paste.
- Guiding and finishing the blades of kitchen knives can be reduced to one operation with abrasive No. 800-1100.
Touchstone
A home-made knife sharpener will be much more convenient and accurate if you don’t buy a donkey for it, but make it from a piece of a square professional pipe 200-300 mm long (on the left in the figure below) or a wooden bar.
The edges of the base are pasted over with emery cloth acc. numbers. Glue - clerical glue stick. The advantages of a skin-based touchstone are obvious:
- Much cheaper than an emery bar.
- It can be made on 4 abrasive numbers, while emery stones are maximum 2-sided.
- Wear (development) of the abrasive is possible no more than the thickness of the abrasive layer of the skin; the waviness of the RK due to the rotation of the touchstone on the sharpener rod (see below) is also no more than this value.
- As a result, the error in the angle of sharpening from the development and rotation of the touchstone does not exceed fractions of a degree.
- The whetstone from the pipe can be put on a threaded rod (in the center in the figure), which speeds up and facilitates the change of abrasive.
- A whetstone made of a pipe or a wooden block is held in any clamps for an emery block no worse than the latter, on the right in fig.
Knife sharpeners
The simplest manual knife sharpener is an angular frame in which a whetstone is clamped, pos. 1 next. rice. The same type of “company” is on sale, and this is marketing, marketing: for a plastic board with inclined sockets for donkeys, they want up to $50 or more. Touchstones - non-standard sizes; Ordinary holes won't fit. Worked out - you need to buy the original ones. Price - you know. And all the convenience - when sharpening, keeping the blade strictly vertical is still easier than maintaining its angle of inclination.
The use of a simple knife sharpener can be further simplified to total absence the need for skills, if supplemented with a sliding shoe with a magnetic knife holder, pos. 2. The order of sharpening in this case is the following:
- Knife right hand hold the handle, turning in the direction of travel according to the curvature of the blade;
- With the fingers of the left hand, except for the big one, they press the shoe to the touchstone;
- With the thumb of the left hand, they press on the butt of the blade, pressing the RC to the abrasive.
The function of maintaining the angle of inclination is removed from the operator, and the rest are distributed to 2 hands. In this case, the skill of sharpening with one's own hands is developed immediately, but a holder is needed that firmly holds the knife and at the same time allows it to slide over its surface. This can be done from the magnets of the carriage drive of the write-read heads from an unusable HDD drive (hard drive). The “screw” carriage drive magnets are niobium, thin, flat, smooth and very strong (shown by red arrows in pos. 3). They are glued with DIFFERENT poles on a steel strip, the force of attraction of the blade will then double. And to ensure sliding, the holder is covered with a fluoroplastic film 0.05-0.07 mm thick. PET from bottles will also work, but it is thicker and the attraction will be weaker. Polyethylene is not suitable, it will be wiped immediately.
Note: remember this holder, we will need it later.
LM
It does not require any special skills and the use of a manual sharpener for knives such as Lansky-Metabo, pos. 1 in fig. The scheme of its device is given in pos. 2, and the order of use - on pos. 3. The disadvantage of the Lansky-Metabo sharpener is the instability of the sharpening angle along the length of the blade: a rod with a whetstone is driven along it. The offset of the touch point is constantly changing, because it describes an arc of a circle, and the blade has a different configuration. Resp. "floats" and the corner. Therefore, the Lansky-Metabo sharpener is mainly used for sharpening hiking and hunting knives with a relatively short blade.
but this shortcoming it is possible to turn it into dignity if the blade is clamped in the terminals with the root part A (at the handle) and the tip slightly turned away from you, pos. 4. Then, at the root of the blade, the sharpening angle will be the largest, which is optimal for processing hard materials or using the knife as a cleaver. So after all, they work in such cases, so that the outer arm of the arm-blade lever is shorter.
Towards the middle of the blade B, the sharpening angle will gradually decrease and reach a minimum at the bend of its generatrix B1, which is convenient for fine workmanship. Then, towards the B tip, the angle will increase again, which will make the tip more resistant to drilling, gouging/impact and breakdown (piercing).
Note: Another disadvantage of the Lansky-Metabo sharpener is the difficulty of execution in the desktop version. But this shortcoming, as they say, is fake, see pos. 5.
Detail drawings of the original Lansky-Metabo sharpener are given in fig. The numbers at the windows for the bar (guide) correspond to the FULL sharpening angles.
On the trail. rice. Dan Assembly drawing clamp, and then - the drawings and dimensions of the Lansky-Metabo terminals, made from a corner 90x90x6 mm. The author of the development hides under the pseudonym Serjant. It is certainly a matter of his modesty. But, by the way, in production, technological innovations that make it possible to use standard profiles for the manufacture of shaped parts are sometimes valued more than serious inventions.
Note: on the trail. rice. given the assembly drawing of the sharpener Serjant. As for the inconvenience of fixing in a vice - see above.
Knife sharpening machine
The most advanced household manual sharpener today is the Apex type knife sharpener. His appearance, device diagrams and how to use, see fig. Apex can be made with a continuously variable sharpening angle (pos. 2) or fixed angles like Lansky-Metabo (pos. 3). Normally, they work on Apex as on Lansky-Metabo (pos. 4), but other options are possible for more accurate sharpening, see below.
A homemade version of the Apex sharpener - a sharpener for knives Skomorokh
In 2016, in Runet, it made a noise, perhaps, no less than once the bubafon stove, the desktop modification of Apex by Ivan Skomorokhov, see fig. on right.
Skomorokh sharpeners are much simpler than the prototype and in no way inferior to it in functionality.
How to make a knife sharpener Skomorokh, see video:
Not only knives...
The original Apex sharpener is not very suitable for sharpening carpentry tools- chisel, planer iron. Apex's sharpening angle floats for the same reasons as Lansky-Metabo. Meanwhile, if the angle of sharpening the chisel along the width of the blade “walks” by more than 1-1.5 degrees, then the tool strives to go sideways, crawl out or go deep into the solid wood along its fibers. It is very difficult to choose a groove for a spike / comb evenly and accurately with such a chisel.
There are special devices for sharpening carpentry tools, about which a special conversation is needed. Homemade products like a roller cart sharpener, see fig. on the right, rather curiosities: not to mention the complexity, they require a stone or steel table, and, most importantly, they do not guarantee against misalignment of the blade on the whetstone, which leads to the same undesirable result.
Meanwhile, 2-3 years ago, in one of the Chinese magazines on technical creativity, Apex’s refinement flashed for sharpening, not inferior to that on a factory electric grinding semi-automatic. The alteration is not difficult, see Fig.: the bar is set horizontally according to the level and the horizon of the bar is held along it, leading to sharpening. Within the angle of rotation of the rod in the horizontal plane of 10-12 degrees to the right and left, the sharpening angle error is less than 1 degree. If the extension of the point of contact is from 250 mm, it is possible to sharpen chisels and pieces of iron planers up to 120 mm wide.
In this mode of operation, zero (theoretically) sharpening angle error can be achieved by keeping the bar stationary and moving the knife held by the magnetic holder, see above. Thus, it is also possible to sharpen the irons of shaped planes if a round, semicircular, elliptical or segmental whetstone is placed in the clamps. The main thing is that the touch spot should always be a point.
...but also scissors
Another refinement of the Apex sharpener for sharpening scissors (also a necessary thing in the household) is shown in fig. on right. Total work - a couple of pieces of a corner or scraps of galvanization and 4 additional holes in the sharpener table. About the process of making do-it-yourself attachments for sharpening scissors to the Skomorokh sharpener, see next. video:
Video: sharpening scissors, attachment to the sharpener Skomorokh
One last thing about scissors
Before grabbing badly cutting scissors and sticking them in the sharpener, check to see if the hinge is loose. Open the scissors and look at them from the side. See how the tip is wrapped with a screw towards each other? That's why scissors cut: the point of contact of the blades during cutting shifts from the roots to the ends. And therefore it is difficult to cut with scissors with the left hand: the inversion of the ends is designed for the kinematics of the right. And if the hinge of the scissors is loose, the blades will move away from each other and will not even cope with paper. In this case, you just need to tighten the riveted hinge with a hammer, and the screw hinge with a screwdriver.