Each of us has encountered life situation when blunt tools, be it a regular knife or carpentry tools, get in the way normal operation. Dull tools require greater effort and therefore your hands get tired faster and possible dangerous situations. Sharpening the tool in advance will provide you with a quick and easy work process without any extra effort.

Each type of tool has a cutting edge with its own individual sharpening angle. Tools with sharpening angles up to 25° have sharper edges, but are not suitable for work that requires significant effort; in this case, tools with a large sharpening angle are used. It is necessary to take this fact into account and therefore, before starting the sharpening process, we advise you to familiarize yourself with optimal angles sharpening various instruments. By the way, good sharpeners are equipped with an angular scale for setting the supporting surface for a specific tool, which greatly facilitates the process of sharpening the tool.

Sharpening angles for some tools

• scissors – 60°;
• carpenter's ax – 40°;
• kitchen knife – 20-40°;
• vegetable and fish knives – 25°;
• chisel – 35-40°;
• chisel – 18-20°;
• plow – 20°;
• turning cutter – 15-25°;

For sharpening you will need an electric sharpener (recommended for beginners), sharpening stones various shapes and grain size and a container of water. The process of sharpening a tool requires some skill and experience, so it can take quite a while. long time, before you learn how to sharpen your tools as efficiently as possible.

Sharpening chisels and chisels

These popular tools are in every carpenter's kit. Typically, chisels with a width from 3 to 16 mm and various sharpening angles are used, as well as flat and semicircular chisels. The process of sharpening these tools begins with a sharpening wheel, and then the dressing is done on a whetstone. An important point is the position of the blade relative to the abrasive wheel; the plane being sharpened at the point of contact should be located strictly perpendicular to the radius of the wheel. After sharpening, you need to pay attention to the resulting chamfer. The length of the chamfer to obtain the desired angle of 20° must be 2.5 times greater than the thickness of the tool.

Tool sharpening with cooling

Sharpeners with a cooling function allow even beginners in turning to perform high-quality work, since the wheels in them rotate more slowly and are constantly cooled, preventing the tool from overheating. Sharpeners can also be equipped with special templates for setting sharpening parameters.

1. The necessary parameters are set on the template, and then the tool is installed in it and its position relative to the circle is adjusted.
2. The cutting surface of the tool must fit into the groove of the template until it stops - this allows you to control the correct sharpening.
3. Finishing of the cutting edge is done on a leather wheel.

Sharpening semicircular chisels

Sharpening large tools

For carpentry work that requires a plane or chisel that can easily remove thin curly shavings from wood. Here you can use a system that allows you to obtain cutting edges that are completely flat, exceptionally sharp and shiny like a mirror.

The main link of the system, how to sharpen a tool, is a set of four Japanese water stones. These artificial sharpening stones contain tiny abrasive particles such as natural clay and silicon carbide, bonded into blocks with a ceramic bond.

Rough stone 700 grit (grit) from Bester to remove large marks from grinding wheel on a new tool or after a serious resharpening.

Bester brand stone, 1200 grit, for intermediate dressing and removing marks from the previous rough stone.

2000 grit Shapton stone for fine finishing of the cutting edge.

8000 grit Takenoko stone for final polishing to a mirror finish.

Each stone is equally important to the sharpening process. If you miss one of the intermediate stones, you will encounter the same problems as when sanding wood sandpaper: It will take longer to remove marks and scratches left by a coarse abrasive than with successive transitions from coarse to finer grains.

Before working with water stones, have the following supplies ready: a container of water for soaking the stones, a clean cloth, napkins or towels for wiping the blades and wiping up puddles and drips, and a corrosion preventative. Sharpening devices that fix the blade at the desired angle, water ditches, templates for checking angles and other accessories will help make the sharpening process easy and neat.

Prepare the stones

Before starting work, immerse the stones in clean water for two to five minutes until small air bubbles stop coming out of them. After soaking, sand the working side of each stone to create a smooth surface for sharpening. You can use a completely flat Shapton diamond stone for this, it is no less effective and more cheap way: A sheet of 150 grit waterproof sandpaper on top of a square of thick glass about 300mm on a side.

Wet waterproof sandpaper well and place it on the glass. Water holds the paper on the glass, preventing it from moving. To avoid clogging fine-grained stones with coarse abrasive particles, first level the 8000-grit water stone, then successively coarser stones, ending with a 700-grit stone. Move the stone back and forth across the paper, making circular movements from time to time (photo A), until the marks of the previous sharpening are completely gone. The leveled surface of the stone should be completely covered with a thin layer of water, and not just in the center or at the edges.

A. Minor scratches on the working side, such as on the left stone, mean that its surface needs to be sanded using wet abrasive paper.

Rinse the abrasive paper thoroughly before smoothing the next stone. Rinse all stones under running water before you begin sharpening your blades.

Start sharpening

Let's look at the working techniques using a chisel as an example, but the principles of sharpening do not change for other cutting tools, such as a plane blade. Your task is to obtain a completely flat chamfer and the back of the blade, the intersection of which creates a straight and sharp cutting edge. While you have no experience, focus on developing coordinated movements and even pressure. Speed ​​will come with time.

Place the soaked and leveled stones on a flat surface to prevent them from shifting or rocking as you work. It is convenient to use a small anti-friction mat for this, but it can be replaced with several old newspapers.

B. Start by leveling the back of the chisel blade. With one hand, press the tool against the surface, and with the other, hold it perpendicular to the long side of the stone.

Start sharpening your chisel or plane blade by leveling the back. When starting to work on a 700 grit waterstone, hold the tool blade perpendicular to the long side of the stone, pressing the flat side of it against the abrasive 12-15mm wide (photo B). Do not straighten the entire plane of the blade at once; you only need to remove rough marks near the cutting edge.

Using light pressure, move the tool back and forth along the entire length of the stone. Develop coordination of movements and constant hand position so that the tilt of the blade and the pressure on it do not change when working on the other three stones. You will have to sand the back and bevel before moving on to the next water stones and finishing the job by polishing the blade on an 8000 grit stone.

Now finish the chamfer.

Use one hand to hold the tool at the desired angle. Using the fingertips of your other hand, press the bevel of the blade firmly and with constant force onto the surface of the water stone (Photo C).

C. When sharpening any chisels (except the narrowest ones), use two fingers to press the bevel of the blade evenly and firmly against the stone. With your other hand, hold the tool at the desired angle.

Use the entire working side of the stone to avoid uneven wear of the abrasive in the middle or at one edge. Sharpening technique will certainly improve with practice, so don't start with the best chisels. Sharpen plane plane blades and narrow chisels last as you become more proficient. With wide chisels, it is easier to maintain the desired sharpening angle, since the fingers better feel that the blade is adjacent to the stone with the entire chamfer.

If you are unsure of your hand stability and need help holding the blade at the desired angle, use simple sharpening devices like the one shown in photo D. Use it sharpening device until you learn to press the chamfer of the plane or chisel blade onto the surface of the stone with its entire plane and maintain a constant tilt of the tool.

From the many available models, choose a device with a support roller of sufficient width to reduce wear on the stone surface. First check the quality of work by inspecting the chamfer after three or four movements in order to notice in time possible mistakes. The chart below will help you spot any weaknesses in your technique before they become bad habits.

Once the back of the blade and bevel are evenly finished, move on to the next waterstone up to 8000 grit. You can change the stone as soon as all traces of previous polishing have been removed. But before doing this, be sure to rinse the tool with water and wipe it thoroughly to remove all remaining abrasive and not clog the finer-grained stone with it.

During the sharpening process on the first two rough stones, you will feel, and perhaps even see, a very fine burr forming on the cutting edge. It should disappear by the end of sharpening.

When finished grinding the blade on an 8000 grit stone, the cutting edge will shine like a mirror. Rinse the blade clean water, wipe it dry and apply thin layer light lubricant to protect against rust. (Do not let the lubricant get on the stones!) Check the quality of sharpening of the blade at the end of the cutting board (photo E). E. The flat bevel and flat back create a sharp cutting edge capable of cutting fine chips even on the end of wood.

Before storing stones, wash and dry them. Cover sharpened chisel blades with plastic protective caps.

Caring for water stones

Water sharpening stones will last you for many years, requiring only minimal maintenance.

■ Some craftsmen constantly keep stones in water, but this sometimes leads to damage to certain types of stones, and corrosion of metal flakes embedded in the pores of the stone causes a change in its color.

■ Avoid contact with oil or silicone grease on water stones. This leads to a decrease in abrasive properties and irreversible loss of performance.

■ Protect wet stones from frost. Freezing water can cause cracks.

■ Store stones away from falls and impacts. A plastic container with a lid is an excellent container for storing stones and for soaking them.

It is suggested to delete wooden coasters on the stones, carefully cutting them down band saw. This is not necessary, but without stands it is easier to store and soak the stones. If you want to separate the stand from the stone, do not try to tear it off with a chisel or hammer blows - rough chips will appear on the stone before the glue gives in to your efforts.

1. The sharpening marks are shifted to one edge of the chamfer.

Solution. Narrow chisels (6-12 mm) have a small contact area between the chamfer and the stone, making it difficult to press with the entire plane. Use a sharpener or gain skill by sharpening wide blades.

1. The sharpening marks are wider at the front end of the chamfer or are visible only on one end.

Solution. Stop working often to monitor the results. Concentrate on maintaining a consistent blade angle, even if this means releasing pressure.

1. Sharpening marks do not reach the center of the chamfer.

Solution. The abrasive wheel of the sharpener makes the chamfer slightly concave, so rough marks in its center when finishing on a flat stone will disappear in last resort. Continue sharpening until you obtain a uniform shine, indicating a smooth and flat bevel.

1. Numerous edges on the chamfer.

Solution. If the chisel looks like this after sharpening on the sharpener, resharpen the bevel. If edges appear when sharpening on water stones, focus on keeping the tool at the same angle as you move back and forth across the surface of the stone.

1. Problem. Don't know when to stop?

Solution. The chamfer is almost complete (notice a few marks at the top left). A few more strokes on the 8000 grit stone are required to achieve a sharp cutting edge and final polish. A perfectly sharpened bevel reflects a ray of light just like a mirror.

1. Materials and assembly rules
2. Assembling a sharpening machine
3. Edit

If you are passionate about carpentry and make wood products, then you know how uncomfortable and even dangerous a dull tool can be. It is advisable to have sharp cutters on hand, for sharpening which you can make a special device yourself.

On a sharpening machine, with the proper approach, in 10–15 minutes, depending on the hardness of the steel, you get a sharp tool. The process may take a little longer if the cutting edge is significantly damaged. Once straightened, the chisel will cut wood easily without the risk of damaging the surface being worked on or, worse, causing injury.

Advantages of a homemade sharpener

There are devices on sale designed for sharpening chisels and plane knives. They differ in type and material of manufacture. These can be synthetic or diamond shards, natural minerals and other mechanical objects. For carpentry workshops they often purchase special electrical machines vertical or horizontal design. However, sandpaper is in no way inferior to all these advertised devices. It does an excellent job of grinding down metal, giving it thin and clear edges, and its cost is extremely low.

Materials and assembly rules

An excellent result is guaranteed by black sandpaper, the abrasive side of which consists of silicon carbide. It is suitable for wet and dry grinding, and due to the hardness of the material, which is superior in similar parameters to garnet or aluminum oxide, it copes with the task better and wears out longer.

Sharpening a chisel at home requires sheets of paper with different grain sizes (from 100 to 600 units). The final grinding of the cutting edges is carried out with a fine abrasive powder, which can be replaced with a kitchen cleaner containing feldspar, soda or oxalic acid.

To ensure comfortable work on sharpening tools for wood carving, the master needs to create an even base from thick plywood or MDF, on which sheets of emery will be laid. To enhance the adhesion between the paper and the smooth base, you can spray the plywood with water.

No matter how sharp the vision of a craftsman may be, it is difficult to complete the job without the help of a magnifying glass. Therefore, it is better to play it safe and purchase a simple lens with eight times magnifying power. Such an optical device does not obscure the light and makes it possible to see most of the flaws in the cutting tool.

When working with sandpaper, it is necessary to maintain the sharpening angle, which is not easy to do manually without special device. This problem is solved wooden device, providing control over the process at all its stages. With its help, the blade will be fixed at a given angle, deviations will be excluded. In this case, the chamfer of the product will acquire an optimal plane. In this way, it is possible to ensure uniform abrasion of the sandpaper when performing movements in opposite directions.

Assembling a sharpening machine

Below in the picture you can see a device used to sharpen carpentry chisels and plane blades with a length of 75 mm at an angle of 25°. Such drawings are also suitable for assembling a similar machine for straightening blades at different angles. Sharpening semicircular chisels is performed using other equipment.

The beginning of assembly involves sawing out the base from hardwood with a margin of length. We recommend focusing on workpiece dimensions of approximately 13x76x255 mm. At a distance of 19 mm from the back of the workpiece, it is necessary to cut out a tongue and groove (5x45 mm - DxW), for which a groove-forming cutter is installed in the sawing unit. Then, using a longitudinal cutting disc, a bevel is sawed at an angle of 25°, and the workpiece itself is fixed with double-sided tape to the load-bearing surface. Now a vertical cut sets the final length of the product to 190 mm.

To make a trolley holder, you will need a workpiece measuring 19x45x255 mm, on which a bevel is sawed off at an angle of 25° and vertically cut to a length of 190 mm. Then, on its lower side, at a distance of 32 mm from each edge, two holes are drilled with a recess for the nut. After this, a groove 102x1.5 mm (WxD) is made with a groove disk, in which a chisel or chisel will be fixed at a right angle.

On next stage The clamp is cut out and holes are made for screws in the middle of the workpiece at a distance of 32 mm from each edge. The handle of the device is glued to the clamp, and after drying adhesive composition carried out final assembly. So that the sharpening machine can function normally and the holder slides without unnecessary effort, a special wax composition is applied to the tongue of the base.

The process of sharpening on a homemade machine

To sharpen a dull tool, you need to place the device on coarse sandpaper. The cutting part of the chisel is installed in the holder under the clamping mechanism with the chamfer down, after which the nuts are tightened to secure the tool tightly. The blade should be perpendicular to the working plane.

When you start sharpening the cutter, pay attention: characteristic marks will be visible on the sandpaper, so you need to move the structure so as to continue the process on the untouched part of the material. The work is carried out until the cutting segment acquires a uniform matte surface. Before changing the sandpaper to a finer abrasive, walk around a couple of times. reverse side blades on coarse paper, removing any burrs. Each time you change the abrasive, repeat the process until the sharpened tool becomes optimally sharp.

Edit

Sharpening the chisel is completed by straightening it using leather belt, grated with GOI paste. The cutting edge is polished to a mirror finish. The paste can be replaced with a kitchen cleaner, which does the job just as well as the paste. The powder is poured onto a flat wooden surface. A hand-held machine will come in handy here; you need to sharpen it according to the principle discussed earlier.

Device for sharpening semicircular chisels

Sharpening a semicircular chisel is performed on wooden block with an edge processed to the shape of the tool. During the work you will need:

• silicon block;
• plywood;
• abrasive powder;
• leather;
• sandpaper of different grits (400, 800, 1000, 2000).

You need to start the process by wetting the bar in a soap solution, and then you can start working by pressing the chamfer to the touchstone and performing sideways movements (as in the photo below).

After a burr has formed, take a piece of wood with a rounded edge, onto which sandpaper is glued (replace it, gradually moving from coarse to fine abrasive).

At the final stage, the chisel is polished and straightened using leather. When the blade acquires a smooth, sharp edge, it is necessary to check its cutting ability.

Any cutting tool (knives, chisels, scissors) wears out and becomes dull during operation, that is, the radius of dullness at its tip (cutting edge) increases. For normal cutting, the tool blade must have smooth surface and the thickness of the blade at the tip is only 6-8 microns. A dull tool stops cutting during operation, but begins to crumble and crush the material, as a result of which the quality of the processed surface deteriorates and the force required for cutting increases. Because of this, by the way, people are more often injured not with a sharp instrument, but with a blunt one. So any self-respecting master simply must be able to sharpen and edit home tool(knives, scissors, drills) using an electric sharpener or manually.

The fastest and most convenient way is to sharpen and straighten a tool on an electric sharpener, on the shaft of which abrasive and finishing wheels are installed. To provide required angle When sharpening a tool on an electric sharpener, it is necessary to provide a movable stop.

When starting to sharpen, remember that the abrasive wheels must be covered with a casing at the top, and the gap between the stop (thrust) and the abrasive wheel must be maintained within 1.5-3 mm.

a - after sharpening and finishing; b - blunt edge; c - restoration of the sharpness of the edge by removing a part of the metal from the chamfer with an abrasive

To master correct technique When sharpening tools, novice craftsmen will have to work a little to gain some experience in working with an emery wheel. First of all, you should choose the right abrasive wheel with a grain size and hardness suitable for the job. Remember, the larger the grain, the more productive the sharpening process, but the greater the roughness of the processed surface. Abrasive wheels with fine grains become clogged (greasy) faster and begin to set the blade on fire. Typically, these circles are used for final finishing of the tip, that is, removing micro-irregularities from its surface.

When choosing a wheel of one or another hardness for sharpening, take into account that if the wheel is too hard for the tool, it clogs faster and overheats (sets fire) the blade, and when the wheel is too soft, it wears out faster, losing its original shape.

To determine the hardness of a tool material at home, a finely cut file is often used. They do it like this. They are simply trying to sharpen the blade of a tool with a file. If the file simply slides along the blade without removing metal, the hardness of the metal of the tool and the file is the same and is approximately 61-62 HRC. This is the hardness of knives, chisels, etc. happens rarely. If the file does remove some of the metal from the blade, the hardness of the tool blade is quite good - 58-60 HRC (this is the usual hardness of the tool). When the file removes metal from the blade quite easily, the hardness of the cutting part of the tool is unsatisfactory - less than 40-45 HRC. At the same time, a novice sharpener should know that it is almost impossible to sharpen a kitchen knife or chisel made from low-quality or unhardened steel with a hardness below 40 HRC, and it is difficult to work with such a tool, since it will become dull immediately after sharpening.

Forged ball bearing steels ШХ15, surgical steel 40X13 (stainless steel for kitchen knives), tool steel U8-U11A, alloy steels 9ХС, 9ХФ, Р18, the hardness of which after heat treatment reaches 58-60 HRC.

For sharpening household and woodworking tools, abrasive wheels of the EB brand (electrocorundum white) on a ceramic bond K, with a grain size of 40-25 and a hardness degree of CM1 (medium softness No. 1), are used.

When a suitable wheel is fixed, the sharpening angle of the tool is selected, guided by the considerations that as the sharpening angle decreases, the cutting properties of the tool increase, but the strength of its blade, especially during impacts and contacts with solids, is decreasing. Taking into account the above, certain sharpening angles shown in the table are recommended in practice for a particular tool.

As can be seen from the table, the harder the material being processed, the greater the sharpening angle, and this rule is true even for ordinary kitchen knives. By the way, knives intended for one purpose or another have not only different sharpenings, but also their own blade cross-section.

Tool sharpening angles and blade hardness

So, the sharpening angle of the tool (chisel, jointer knife) is known. Now you will have to attach the stop to the electric sharpener so as to ensure this angle when sharpening. The rotation of the abrasive stone should not be accompanied by vibration and beating. If the latter are present, the wheel is edited (with a piece of KZ type abrasive). Of course, sharpening is carried out by rotating the wheel towards the cutting edge of the blade.

a - a knife for vegetables and bread; b - knife for root vegetables; c - meat knife; G - hunting knife; d - metal scissors

The ability to chamfer a cutting tool, that is, to shape its blade, is the main prerequisite for proper sharpening of the tool. When chamfering, take the tool in your right hand, and with your left hand lightly press the blade (below the sharpening point) to the abrasive wheel. During the sharpening process, make sure that the chamfer is ground evenly in one plane across the entire width of the cutting part of the tool, for which purpose this cutting part is constantly “driven” along the sandpaper to the right and left. Periodically, the tool is cooled in water, preventing the appearance of tarnish on the blade, that is, its overheating.

At first, when sharpening, it is better to use a stop, and when experience comes, the need for a stop will disappear by itself. An ordinary kitchen knife is not very difficult to sharpen even without a stop, but the blade of the knife must be held firmly enough in your hands, constantly monitoring the process of forming a chamfer, which is removed evenly on both sides of the blade, preventing it from overheating. For novice sharpeners, we recommend a very simple stop in the form of a plate for sharpening knives. During operation, the butt of the blade rests on the plate, helping the sharpener keep the blade in the same position relative to the abrasive (in this case, the sharpening angle is controlled by the sharpener itself).

Sharpening a tool on an electric sharpener is considered complete when there are no chips or other flaws left on the blade, and a continuous line of burr is formed on the cutting edge of the blade, that is, a thin roller of scraped metal particles. Such a burr is easy to detect by touching with your thumb. right hand, if you hold it along the “tangent” to the cutting edge. The burr can also be seen by holding the tool blade up to the light towards the cutting edge. You should, of course, not break off this burr after sharpening, since in this case, jagged edges will probably form on the cutting edge, which will then be difficult to remove. To get rid of a burr, an abrasive wheel with a finer grain is placed on the sharpener. As a result, after sharpening the chamfer, the burr becomes completely invisible.

The cutting edge is straightened and fine-tuned using GOI paste applied to a hard felt wheel. Please note that when finishing the tool, its blade is positioned along the direction of rotation of the felt circle (from the butt of the blade to the blade), and not towards the edge. The completion of finishing is determined by the appearance of a thin shiny line 0.5-1 mm wide at the cutting edge and the disappearance of the burr (it must be ground off). To prevent the formation of a “false tip” from a burr on a sharpened tool after finishing, the blade is drawn with pressure along hard wood. After this, finishing is carried out again. The sharpness of a tool is usually checked by lightly running the blade along a sheet of paper. A sharp blade cuts silently, but a dull blade crushes and does not cut.

To sharpen and straighten the tool manually, you need whetstones with a grit number from 40 to 16 and a hardness of CM1, SM2, ST1, and for finishing you will need whetstones with a grit number of 6-4 and a hardness of VT or 4T.

1- whetstone for sharpening EK50SM18K; 2- straightening block type EK25SM1; 3 - touchstone type EK4 VT 8K

to make it more convenient to work, bars and whetstones are embedded (recessed) into wooden board, coated with drying oil or waterproof varnish. First, the tool is sharpened on a coarse-grained whetstone of type EK50SM1 8K until a burr forms on the cutting edge. Manual sharpening tedious and time-consuming, but let us remember our ancestors, who only used it, and achieved excellent results. The tool to be sharpened is held so that the entire surface of the chamfer is adjacent to the block. Sharpening is carried out with even and smooth movements, moving the blade along the block forward or backward or in a circle. Work continues until a thin burr forms on the edge of the blade.

If a tool is sharpened “with one chamfer,” once a burr appears, they proceed to straightening and fine-tuning the cutting edge. For knives whose cutting edge is formed by two chamfers, after sharpening one chamfer to a burr, they proceed to processing the other chamfer. Both chamfers are sharpened evenly until the burr becomes barely noticeable.

a - correct; b - wrong

During sharpening, the bars must be moistened with water, which improves the sharpening process (instead of water, either kerosene or a mixture of glycerin and ethyl alcohol will do). Next, the cutting edge of the tool is straightened on a block with a grit number of 20-16. After editing, finishing is carried out with a touchstone. Finishing of kitchen knives is usually not carried out, but for other cutting tools it is required.

To polish the tool, bars of size are usually used. 200x50x20 mm, made of electrocorundum or silicon carbide (abrasive grain number 4, hardness VT). First, the back edge of the cutting edge is ground using circular movements of the block, gradually reducing the pressure of the whetstone (the latter is placed at an angle of 1-2° to the plane of the back edge). When creating a finishing chamfer with a width of 0.5 mm, they move on to finishing the front edge, then start processing the back edge again.

Finally, finishing of the cutting edge is carried out on a leather belt rubbed with GOI paste. There is another method of sharpening and dressing a tool, when the tool blade remains motionless, and sharpening is carried out by making circular movements with a chamfer (with a certain pressure) until a burr forms on the cutting edge. In this case, the block is held firmly, tightly pressing its edge to the chamfer plane, without under any circumstances collapsing the cutting edge.

The working edge of any bar should be as flat as possible. To give the edges this shape, the bars are ground with micropowder on a cast iron plate greased with oil. And remember that it is easier to maintain the sharpness of the blade than to sharpen and straighten a completely dull tool. By the way, to maintain the sharpness of the blade of kitchen knives, the following method is recommended: a T15K6 carbide plate is passed along the blade of a dull knife (such plates are used for turning cutters). In this case, the plate is held with an inclination of 1-2° to the chamfer, so that when moving it removes part of the metal from the chamfer. For a knife, of course, the chamfers on both sides of the blade are processed this way. It is clear that such sharpening is quick and easy. But as soon as the dull radius exceeds 60 microns, the cutting shape of the blade will have to be restored using an abrasive.

Never cut the sandpaper with scissors to restore the cutting properties of the scissors. The effect will be temporary, and the blades will lose their desired shape. Sometimes it is enough just to bend the blades, after which the scissors begin to cut normally again.

HARDENING AND SHARPENING OF JOINERY TOOLS

1. Hardening of the tool

Not every steel can be subjected to heat treatment at home. The most common carbon steel, from which many tools are made, including files, can be easily hardened. Old files are convenient blanks for making, for example, straight and semicircular chisels, especially semicircular cutters. Hardening includes two operations.
During the first operation, the instrument is heated to a cherry-red glow on a gas burner or in another way. Well cleaned kitchen gas-burner It is quite suitable for heating small instruments. The heated tool is quickly lowered into water, the vessel with which is located as close as possible to the burner, and it is moved sharply to get rid of the steam shell that forms around it, which prevents contact of the metal with water.
The second operation (tempering) consists of softening the steel, hardened to the point of brittleness. Now the cutter is heated slightly, controlling the color of the tarnish. Therefore, the scale formed on the tool during the first operation must be removed by light polishing to a shine on fine sandpaper (at least a sharpening chamfer), trying not to damage the blade. A section at a distance of 1-2 cm from the end of the cutter is heated on a flame. Do not heat the cutting tip itself, which can quickly overheat. The tip should get hot internal heat, coming from the rod. You need to monitor the color of the tarnish on the polished surface, catch the moment when the cutting tip begins to turn from blue to cherry, and sharply lower it into water (preferably with a layer of oil on the surface).
Then the tool, such as a chisel, is tested on wood and sharpened again. If the cutting edge chips during carving, it is necessary to increase the temperature of the second heating to a straw-colored tarnish.
A crumpled tool blade indicates that the hardening regime does not correspond to the type of steel or that the operation was unsuccessfully carried out: the temperature of the first heating was not high enough, slowdown when lowered into water, not a sharp cooling due to a layer of steam formed in the grooves and bosoms of the tools, or a tempering temperature that was too high.
In other cases, when the tool is not made of carbon steel, it is better to seek help from a specialist, since at home it will not be possible to obtain a high enough temperature to harden high-quality steels.
For a carpenter who has the ability to heat the tool, for example, in muffle furnace or blacksmith's forge, here are some basic recommendations.
The grade of steel can be approximately determined by a spark on a grinding wheel in a dark place. Thus, a white beam of sparks with individual stars indicates that the steel is carbon, requires slight heating during hardening (up to a temperature of 780 ° C - cherry-red glow) and tempering when the tarnish color changes from violet (for cutting tools) to straw (for work with a mallet). Heat treatment of such steel can be carried out at home using a gas burner.
If there is a short beam of dark red sparks with almost no stars, the high-speed steel is R18. She demands high temperature hardening - about 1270°C, which corresponds to a bright white glow. This can only be achieved in a large muffle furnace or in a forge.
The hardening temperature is slightly lower (about 1230°C) for P9 high-speed steel. It hardens with a light yellow glow and produces reddish-orange sparkles with a small number of stars on the grinding wheel.
Other alloy steels (chrome produces subtle yellow sparks, tungsten produces well-defined red sparks) are hardened with a light red glow (temperature 820-900°C). Alloy steels are best quenched in oil or in water heated to a temperature of 70°C.
Approximately the same temperature is required for annealing steel before processing: alloy steels are heated to 1000°C, high-speed steels to 1200°C. After heating, they should cool slowly along with the oven.
It should be noted that with high and prolonged heating, carbon burns out. Therefore, it is better not to harden a tool with a very thin section, or after hardening, remove the sharp decarburized tip on a whetstone or sharpener while cooling. For the same reason, you should not be afraid to sharpen the tool, especially the first one, until a burr forms along the entire length of the blade. Also, if the first trial work with a hardened and sharpened tool does not give the desired result, sharpening must be repeated.

2.Sharpening the tool

The whole secret of making good carpentry tools consists of two factors: correct sharpening and the right type of steel, which retains this sharpening for a long time, does not wrinkle and does not crumble from any wood. If the grade of steel does not always depend on the master, then sharpening depends only on him. But for her correct execution you need to have some knowledge. Sharpening a tool consists of two operations.
The task of the first operation is to achieve an even plane of grinding (it is called a chamfer) without rounding it at the very edge and without burning the steel. During this operation, metal is ground off on one side of the cutting part of the tool (like a chisel) or on both sides (like a knife) to form the blade shape required for a given tool. Another task of the first operation is to place a chamfer at a certain angle relative to the second plane (face or chamfer) with the blade tip required specifically for a given tool. This angle, called the sharpening angle, can be different: 7-8° for a knife, 15-25° for chisels, 37-42° for planes and 50-53° for a special plane - a grinder.
The sharpening angle of the tool is strictly dependent on the angle of inclination of the cutting edge (plane) of the blade relative to the surface of the wood, which is determined complex formula. If in tools such as a knife, chisels, axes, we can adapt to the angle of inclination of the cutting edge during work, and therefore the sharpening angle of the blade can vary depending on the need (cutting wood by hand or by hitting it with a hammer or mallet), then in other tools, such as planes, this sharpening angle must be maintained more strictly.
The task of the second operation - editing - is not to spoil the sharpening angle and to achieve a sharp tip of the blade, which is associated with removing irregularities, small notches, burrs from it, and polishing both surfaces of the blade to a shine.
The first operation is usually performed on a mechanical sharpener - a rotating abrasive wheel. It is finished by hand on a large flat block. It is dangerous to sharpen the blade on a sharpener to a sharp point, since in this case it is difficult to control overheating of the steel at high wheel speeds, when unexpectedly a tarnished color appears on the thin edge of the blade during sharpening - a sign that the strength of the steel is compromised and the sharpening is damaged. Such a place will have to be completely cut off on the same sharpener and sharpened again.
In order to reduce subsequent manual work on the whetstone, they try to remove as much metal as possible on the sharpener along the entire chamfer, except for its edge, which is not difficult to do on a cylindrical sharpener: it allows you to remove excess metal from its entire middle using a notch on the chamfer.
To prevent the steel from overheating, the tool is periodically dipped in water and the sharpener itself is also soaked in water. The disappearance of water droplets on the tip of the blade or their boiling is a sign that it is time to put it in water.
It is advisable for a novice sharpener to sharpen the tool on a sharpener so that the circle does not rotate towards the blade, but vice versa or at a certain angle to it (in different directions). This way, if you move incorrectly, there is less danger of crashing into the blade with a sharpener and ruining the whole work. However, throughout the literature it is recommended that any tool be sharpened on a sharpener only when it is rotated towards the blade. But this rule is only suitable for a specialist or craftsman with extensive sharpening experience. There is no doubt that when the surface of the circle moves towards the blade, its sharpening is better: there is less chipping of metal particles on the very edge of the blade - they seem to be pressed during rotation, and do not come off from it when the sharpener moves away from the blade. Also, this does not produce such large burrs as when sharpening “along the blade,” where there are more opportunities for bending the edge, which is what gives the burr. In addition, with strict observance of the rules for sharpening the tool towards the blade, if it is precisely fixed (using a special stop or trained hands), a clearly defined edge of the blade is obtained. These are the positive aspects of sharpening using the method towards the blade. But it also has negative sides, the weight of which is more significant, especially for a novice sharpener. Main disadvantage- this is that we cannot bring the sharpening to the sharp tip of the blade, since in this case the danger of burning it is too great. The tool blade can be brought to the required sharpness only on a water sharpener, the rotation speed of which is very low (as the speed increases, water floods your hands). On all other mechanical sharpeners, sharpening is carried out without water. But even after a water sharpener, the blade becomes sharp only due to good angle sharpening and clearly defined edges. In fact, it is cut with notches from grains of abrasive sand and looks like a file with very small teeth. Such a blade will cut wood, but the cut mark will be uneven and not shiny. The blade will require thorough editing - complete removal of the tip and formation of a new one.
In order to complete sharpening of a tool on a hard block, it is better to clamp the block in a vice or secure it on a workbench. Then the work can be carried out with a clamp, with two hands. The block must first and then periodically be washed with soap and water using a brush, since it becomes greasy and clogged with small metal filings and abrasive dust; it is good to soak it in water. During operation, it is more convenient to wipe the surface of the bar with a wet cloth. It is under such conditions that the surface of the bar grinds off the metal well.
When sharpening a tool, you need to be especially careful that the chamfer is in contact with the surface of the block with its entire plane, so as not to spoil the sharpening angle. You can move the tool along the block in any direction, but as the blade sharpens and a burr appears on it - a thin shiny strip of bent metal on the tip of the blade - you should be more careful with the direction of movements when sharpening. To avoid the risk of cutting into the abrasive with the tool blade, it is better to completely stop its movement towards and along the blade. It is preferable to make movements at an angle of 45° in both one and the other direction in relation to the edge of the blade, in the direction away from it. This is how we reduce the force that bends the tip of the blade into a burr. This sharpening method is confirmed by the practice of experienced craftsmen. Hairdressers have been known to shave straight razors in a similar manner.
The second sharpening operation - straightening - is performed first on a fine-grained whetstone or a special refueling board, then on a whetstone or on a smooth area of ​​the refueling board worn during sharpening, sometimes on a whetstone or refueling board, covered in leather, using a special paste.
The filling board is covered with fine sandpaper (preferably sandpaper on a cloth). Its edges are glued end-to-end on one of the narrow sides of the board. One side of the filling board should be pre-rounded, with different curvature along the edge. On it we will edit the concave face of semicircular chisels.
When editing on a whetstone, you can first make circular movements with a tool (for example, a chisel), emphasizing the efforts when moving away from the blade, but on the dressing board you must immediately beware of making movements towards the blade: soft fabric or the sandpaper paper bends even slightly under pressure and the blade “attacks” the sanding surface at a large angle, which will lead to the chamfer becoming full, i.e. to change the sharpening angle. Also, for the reasons described above, the blade may be damaged by touching uneven surfaces on the sharpening surface. For example, when sharpening a knife on a cutting board towards the blade, it even happens that it cuts off part of the glued skin.
During editing, you must periodically turn the tool from one side to the other until both edges of the blade are polished to a shine and the burr disappears completely. As the editing is completed, hand movements should become more frequent and easier, and the sharpened edges should be replaced more often.
After straightening, you need to make a test thread, testing the tool in cutting techniques along and across wood, especially hard wood. It is likely that the bladeIn this case, the instrument will “sit down” and will not give the desired result. This is not always a sign of bad steel, but is most likely the result of carbon burning out of the edge of the blade during hardening, as discussed above. True, this also happens with tools that have not been subjected to heat treatment. In any case, it needs to be adjusted again and checked until the cutting edge is stable.
A well-sharpened tool lasts a long time and does not require frequent refilling. It is corrected only after many hours of work. To achieve results faster, if the tool has been in use for a long time, when refilling, you can slightly increase the contact of the edge of the blade being sharpened with the block, taking into account that during initial sharpening its sharpening angle was quite sharp. In this case, the sharpening angle increases slightly and a secondary chamfer is formed. Naturally, after some time you will have to again straighten the angle of sharpening the blade on a block, or even on a wheel hand drill. Practice has shown that using polishing paste or oil paint"Chromium oxide" is not necessary for final tool dressing. As you work, smoother (worked) and harder places will appear on the dressing board, which will allow you to use the same sandpaper on the board for consistent sharpening: from rough to clean.

3.Sharpening wheel

An abrasive wheel driven by mechanical or electric drive, usually called a sharpener, grinding wheel or grinding wheel. Abrasive discs sold in hardware and tool stores, like other grinding wheels, are made from artificial minerals: electrocorundum, silicon carbide (carborundum), boron carbide, etc., sometimes from emery (emery is a natural mineral and is currently used in mainly for the production of abrasive skins). It is better to buy an abrasive disc made of white electrocorundum (its marking on the wheel begins with EB) or monocorundum (marked M). In terms of grain hardness, they are more suitable for finishing processing, and in our case, for sharpening hardened tools; they have proven themselves well in grinding very hard metal surfaces with a shallow grinding depth.
The hardness marking on abrasive wheels is indicated by the initial letters of the words: soft (M), medium-soft (SM) and then similarly - medium, medium-hard, hard, very hard, extremely hard and by adding numbers 1 and 2 (sometimes 3), specifying the degree of hardness .
Modern grinding wheels are molded on a strong binder and have high tensile strength, providing them with two to three times higher rotation speed than that of an electric drill. Nevertheless, after purchasing a grinding disc, especially if it is not marked, you should definitely check it at a high rotation speed, taking safety measures (not to be in the plane of rotation of the disc) in case of rupture. And in the future, it is advisable not to keep your head in the plane of its rotation at idle (i.e., maximum) revolutions of the circle. These measures are needed in case of a defective or defective disc.
And to make sure that the rotation of the new grinding wheel in the drill is safe, it is useful to know the following information. Typically, the disc marking does not indicate the rotation speed (in rpm), but the peripheral speed (in m/s). This is due to the fact that the centrifugal force (and therefore the breaking force) depends not only on the rotation speed, but also on the diameter of the circle. For example, let's calculate the peripheral speed of the grains on the rim of a grinding wheel with a diameter of 175 mm, inserted into an electric drill giving 2000 rpm. With a rim circumference of 0.175? 3.14 = 0.55 m, the rotation speed will be approximately 33 rpm (2000:60), and the peripheral speed of the grains on it will be 0.55? 33 = 18.15 m/s. And the permissible rotation speed of modern grinding wheels ranges from 35 to 40 m/s, which is more than twice our calculated value.
It should be noted that it is more advisable to use circles with a diameter of less than 175 mm for sharpening an electric drill. This is more convenient for many reasons. Often, in the process of work, you have to sharpen a tool by holding the drill with a sharpener in your left hand and turning it on with short pulses - this way you are more confident not to spoil the sharpening and not to burn the steel. In this case, the mass of the circle, which affects its inertia, will prevent the drill from turning on every time. For the same reasons, excessive peripheral speed of the sharpening surface, which is related to the diameter of the circle, is also undesirable. It is clear that as the diameter of the circle decreases, our calculated peripheral speed will also decrease, i.e. the degree of work safety will increase.
It is in this sense that abrasive fingers with a length of 25 mm and a diameter of 10 mm on a metal axis of rotation, manufactured specifically for an electric drill and sometimes available for sale, are very convenient for sharpening tools.
Grinding wheels have the ability to self-sharpen, i.e. worn out and dull abrasive grains gradually fly off, giving way to new ones. But they also require certain conditions operation: you must try to sharpen the tool in such a way that the wheel is ground evenly over the entire surface, without the formation of grooves. Therefore, it cannot be used for sharpening a tool manually, as a whetstone - this will lead to local damage to its surface and to eccentricity during rotation.
Industrial discs are made in such a way that the hole of each of them is coordinated with the center of gravity and with the geometric center of the rim circumference. Also, when mounting a circle on the axis of rotation, these conditions must be met. Such an axis, with a diameter of up to 9 mm, can be made from a bolt from which the head is sawed off. At the threaded end, a disc is clamped between washers, plate spacers and nuts. First, a hardwood insert is driven into the hole of the disk, its center is precisely found relative to the outer cylindrical surface of the disk, and a hole is drilled for the selected axis. The diameter of the washers and spacers for them must exceed the diameter of the liner, and the liner must be cut flush with the disk. Then, at low speeds of the drill, you need to check the alignment of the disk by touching its cylindrical surface with the tip of a pencil or chalk.

Selecting the hardness of the grinding tool.

Table 1.

Grinding wheels for rough hand grinding.

Table 2.

Grinding wheels for cutting and finishing grinding.

Table3.

Table4.

Cutting tool	Sharpening area	Grinding wheel grade
Turning cutters from high speed steel	Back and front edges	25A 30-20-N SM2
Turning cutters with plates of hard alloy	Rear and front edges of the chipbreaker.	64C 40-16N SM2 64C 16-5-N SM2
Saw blades	Large teeth Fine teeth	25A 25-N ST1 18A 16-N SM2
Saw blades from high speed steel		25A 10-8-N-ST1
Saw segments from high speed steel		25A 25-N ST1
Twist drills from high speed steel: Not large diameter large diameter	Cone part	25A 25-N ST1 25A 30-25-N ST1
Twist drills with carbide inserts		64S 16-5-N SM2-ST1

Grinding wheels.

Table 5

Circle brand	Purpose of grinding wheels
55S 100-25-N SM2-T2 K 65S 30-16-N SM2-ST1 B 64S 40-5-N SM2-ST1 K 64S 40-6-N SM2-ST1 K	Sanding materials with low tensile strength: gray cast iron, brass, hard alloys, glass, stone, ceramics and plastics
25A 30-5-N SM2-ST2K 94A 40-16-N SM2-ST1 K	quality steel of all grades
25A 25-N SM2 K	Grinding at peripheral speeds up to 50 m/s
18A 100-16-N-ST1-T1 K 55С 100-40-Н Т1 B 18A 100-60-N ST2-T1 B	Sanding by hand and by machine structural steel, circles with bakelite (B) bond - for circumferential speeds up to 50 m/s
94A 40-13-N SM2-ST1 K	Grinding extra hard steel
55С 25-Н М1 В 64С 6-Н М1 В 18A 30-16-N M1 V 25A 16-N M1 V	Polishing
64S 25-13-N ST1 K 25A 10-5-N ST2 K

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