How to sharpen a knife

Without a sharp, comfortable knife in the hand, cooking is quite tedious and annoying. Before you sharpen a knife, you need to figure out how to do it correctly, since it is not only more convenient to work with a sharp knife, but also safer and faster. For good sharpening you need a good tool, a good knife and patience to master all the subtleties of this skill.

Kitchen knives

As a result of long use knives become blunt and need sharpening.

Sooner or later, you will need to grind even the nicest, high-quality brand knife. The sharpness of the blade is tested in various ways, including such quite ancient ones as the possibility of using a knife to shave or easily cut several folds of a rope. In order to sharpen knives, you will need:

  • knife;
  • grinding bars;
  • musat
  • grinder;
  • sanding belt.
Graph of knife thickness versus steel hardness

Graph of knife thickness versus steel hardness.

Steel, from which knives are most often made, has an indicator of hardness. For a knife, this indicator should be within the limits of average values, since mild steel is crushed too easily, and it is therefore inconvenient to work with it, while solid material begins to crumble from excessive efforts. When sharpening, it is good to know the hardness indicator, since the blade is harder, the sharpening angle is made more. Approximate hardness indicators are checked by a file in home conditions, by swiping them along the blade. In the case that when lightly pressed, the file slides freely, and when strong, the surface is scratched, the hardness can be considered good. It will not work at home and determine the quality of the blade by its appearance. It depends not on the initial characteristics of the raw materials, but on the technology and on how conscientiously it was observed.

Sharpening tool selection

It is much more difficult than a knife to choose good grinding tools. In today's market there is a very large selection of tools to sharpen, polish and straighten the blade. These are grinding stones, bars or musat, electric or mechanical sharpeners, sanding belts. Sharpening each of these tools will require special treatment and some habit. A professional tool is worth a lot, but you should not save money in this case, as it is easy to spoil a knife with a bad bar and it will not give a good level of sharpening.

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Grinding bars and musat

Grinding bars with different grit

Grinding bars vary in granularity.

A good bar is expensive, but it also serves for centuries. Bars of different quality are produced, their number differs by 1 cm³ of abrasive grains. This number is indicated on the packaging, but depending on the country of origin, different grain systems may be used. To sharpen the quality of even the simplest knife, you will need at least a couple of bars, with larger and smaller grain. One is used for grinding, and the other is used to grind the blade, and ideally and according to all the rules, several bars should be used. Domestic manufacturers do not mark grinding bars for sale, and choose them by eye or on the recommendations of sellers.

Mousats are designed to straighten the cutting edge of knives and to support the sharpness of the blades without sharpening. This tool looks like a long round file, and you can select and buy it at any store with knives and household goods. With the help of musat, constantly used kitchen knives rule. This tool is useful only for some time after sharpening, since you cannot replace high-quality grinding with editing.

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Sharpening machines and belts

Sharpening belt

For sharpening knives are sold special grinding belts.

Machines equipped with abrasive circles and circles of felt, as well as a variety of grinding belts are considered professional equipment. It is with the help of such tools that the initial grinding and grinding of new blades is carried out at the manufacturing plants. As a rule, to work on such machines requires experience and professionalism, therefore, sharpening the knife on the grinding wheel is not recommended for beginners. Much more likely that the knife will be so ruined. Since hardening of steel requires a certain temperature, and when grinding it on a grinding wheel, it is easy to achieve, this uncontrolled heating will ruin the blade very much. It is also believed that factory sharpening makes the blade very sharp, but at the same time it is short-lived, manual sharpening keeps the effect longer.

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Mechanical and Electrical Sharpeners

Electric Knife Sharpener

The electric knife sharpener is simple and convenient to use.

Most often they are used for sharpening household scissors and kitchen knives. They are inexpensive, such sharpeners can be found everywhere, and it is relatively easy to use them. Although the blade is sharpened quickly, the quality of the sharpening remains low, and it also becomes dull quickly. For ordinary knives used in the kitchen, such sharpening is well suited, but it’s better not to spoil sporting and hunting blades in this way.

Electric sharpeners are somewhat different from mechanical ones for the better, and they can be used to sharpen and finish the grinding. It is possible to use both for kitchen, and for sports or hunting knives, the optimum angle of sharpening is determined automatically. Electric knives can be used for scissors, screwdrivers, straight and wavy blades, with their help even severely dull knives are restored. Previously, such devices could not afford the kitchen of every restaurant, but now they are available to everyone.

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How to sharpen a blade with your own hands correctly?

The angle of sharpening of knives depending on their mission

Angle of sharpening of knives depending on their mission.

Hunting and folding knives are sharpened at an angle of 30-35º, if you need a very sharp edge, and at an angle of 40-45º, when you need to make a blunt-resistant blade. Tactical knives are sharpened at an angle from 25 to 40 º, home kitchen - 25-30 º, but the angle will be 10-20 º, if the knife is Japanese, as for a dangerous razor. In boning, filet and other professional cook knives, the angle of inclination when grinding the blade is 25º. The smaller the sharpening angle, the sharper the knife will be, and the larger, the longer the knife will remain sharp.

To sharpen the blade on the grinding bar, it takes at least half an hour of work. If this forged blade, curved, long, then on its careful processing can take up to 2 days. The sharpening begins with the work of a rough bar, it continues until a burr appears on the blade, as the strip of metal is called at the very edge of the cutting edge. After that, you need to change the bar to another, smaller fraction.

To feel the sharpening process, it is recommended to place the bar on a stationary, level surface, on a table or a workbench. To avoid scratching the surface, a soft cloth is put under the bar. The length of the bar matters, and the longer it is, the better. The optimal length is 1.5-2 times longer than the blade. The beginning of the movement of the blade on the bar should be close to perpendicular to the cutting edge, the passage begins cutting edge forward. Keeping the angle close to 90º provides uniform sharpening along the entire length of the blade, thus giving it excellent cutting properties.

Manual knife sharpening scheme

Scheme manual sharpening knife.

Between the working surface of the grinding bar and the plane of the blade to be sharpened, an angle of 20-25º should be maintained, and it should be kept in operation all the time. To do this, having reached the bending point on the blade in sharpening, the handle is slightly raised. The angles of knives, designed for different jobs, can be different when sharpening, it is important to adhere to this inclination constantly. When the sharpening reaches the end of the bar, the blade should also end at the same time, and you need to make sure that the tip does not slip off the grindstone, because it will ruin the side surfaces. Such movements will have to be repeated several times for each side of the knife.

Strong pressure on the bar, contrary to popular belief, will not help to finish the work faster, but accuracy will almost certainly be lost. The blade should go evenly, carefully, without changing the angle, since with one careless movement you can spoil everything that has already been done. This skill comes only with experience, and you have to grind a lot of knives to bring your actions to automatism.

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Grinding and finishing of the knife blade

Grinding the knife with natural leather

For grinding a knife, you can use a belt made of genuine leather.

After sharpening, the blade must be ground, and this is what allows you to keep the sharpness for a long time. Grinding not only gives sharpening durability, but also removes the burrs formed during the grinding process, and the surface becomes completely smooth. The rules of work and movement during grinding are the same as in grinding, but the bar is taken with fine grain. To make the blade very sharp, after a fine-grained stone, you can additionally go through it with a special belt or even a piece of leather.

Lapping on the belt is slightly different from sharpening and grinding, there are no special rules when working, and you should use these tools in the same way. The skin is treated with an abrasive paste, GOI or any other. Often, in the absence of the necessary tools, a ceramic plate or mug is used. They turn over and use the rough surface at the bottom.

You can check the grinding and finishing of the knife in several simple ways, and the safest way to check is to try the knife at work.

Using a knife, cut a newspaper sheet or a tomato, since a newspaper sheet is thin and difficult to cut, and vegetables such as a soft tomato can not be cut with a thin blade. The quality of work is checked and by touch, but this method requires accuracy and is unsafe at work. To identify defects that often occur when sharpening with grinding stones or small stones, carefully, without pressing, you need to hold the ground blade with a small pad of your thumb. The dull blade is smooth and clearly has a rounded shape to the touch, and if the edge is clearly expressed along the entire length, this shows a good job. The blade is also checked on the eye, since the blunt areas glint at the light.

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