The sharpening angles of a knife.
Knowing the sharpening angles of a knife is essential to make the correct choices of angle of the wire according to the type and destination of the knife.
Working and using a sharp knife is the best way to do a clean job and gives a good feeling in using it.
When you try for the first time a quality and sharp knife this feeling is established in your memory and you will not be able to go back, you will only look for more quality and sharp knives.
As soon as you feel that after a certain period of use the knife no longer cuts as before and this is inevitable if you use it, you will be forced to sharpen it again because you will be annoyed by feeling your knife in those conditions.
At this point you can decide to sharpen it yourself or bring it to sharpen but if sharpening a knife needs knowledge and to develop a certain dexterity it is an operation that I recommend learning to do.
Today there are several ways and systems to do it as well as sharpening kits that make this operation easier and more affordable.
Ps. NEVER use those sharpeners that you will find in kitchen goods retailers if you care about your knife.
L’ affilatura e gli angoli di affilatura di un coltello
After you have built your knife one of the last operations to do is to sharpen your blade through rubbing using the:
- levigatrice a nastro,
- pietra affilatrice (quindi una superficie molto ruvida e dura),
- carta vetrata (quindi con una superficie morbide con particelle dure),
- cinghia del rasoio.
The smaller the sharpening angle between the blade and the stone/ribbon/paper/etc. and the sharper the knife will be but less resistant to blows that can chip the wire.
Come vedi dallo schema:
- Le lame molto affilate si affilano a 10 – 15 gradi.
- Le lame normali si affilano a 20 – 25 gradi.
- I coltelli che hanno bisogno di un bordo duro (come quelli per tagliare) si affilano a 30 – 35 gradi.
- Per un taglio estremamente duraturo le lame vengono affilate oltre i 30 gradi.
In general, the harder the material to be cut, the larger the angle of the blade.
The grain of the stone (composition) determines the blade wire (the finer the grains the sharper it is), the same applies to the type of steel of the blade because some metals take and keep the wire better than others.
For this reason, the intended use of the knife serves to better understand which steel to use to build it.
LA PIETRA ABRASIVA (o affilatrice)
The actual sharpening is carried out with the abrasive stone, usually composed of aluminum oxide or silicon carbide.
There are also diamond stones (inside the matrix of the stone is dispersed diamond powder), very expensive but more effective.
The grain of the stone can be more or less fine, ranging from 100 grit (coarse) to 1200 grit (extra fine).
A stone with a grain greater than 300 can effectively sharpen any type of knife.
On the market there are stones with double grain, coarse and fine ranging from 240 to 10,000.
They sell the bases to lock them during the sharpening operation.
Choose a large stone, at least 3-5 cm wide and 20 cm long.
In general, you can divide the stones for sharpening knives into 3 categories of stones:
Each of these types of stones depending on how it is used can then still be divided into stone:
- a secco
- ad acqua
- ad olio
Natural stones were the first stones to be used for sharpening knives, but today they are surpassed in effectiveness and practicality by synthetic stones.
Since each natural stone is a unique piece completely different from any other natural stone in the world (in fact, every natural stone differs in shape and structure) they are indispensable for knife enthusiasts, as they give the knife with them re-sharpened a unique micro serration of the blade.
Le pietre naturali vengono solitamente “fatte”:
- a olio che ha il solo compito di lubrificare,
- ad acqua che oltre a lubrificare ha il compito di trattenere parte della limatura di ferro che contribuisce alla ri-affilatura.
Synthetic stones are made industrially by appropriately manipulating materials with particularly high hardness.
They are in fact stones often made with ceramics, silicone dioxides, aluminum oxides and carbonites.
Being made with industrial processes, synthetic stones are much more uniform both in conformation and structure than natural stones;
This means that, especially in the final stages of re-sharpening, when using stones with grains greater than 1000 grit, much more homogeneous results are obtained and above all knives with micro serrations very similar to each other as opposed to what happened with natural ones.
Synthetic stones are usually “made” either dry or water which has, in this case, the purpose described above.
Diamond stones are relatively recent and are also made in the factory.
In practice, they are metal plates to which zircons are tied on the surface ( zirconium is ideal for quickly sharpening any type of steel).
Diamond stones are in fact often used to make portable field sharpeners.
Usually the diamond stones are “made” dry or water which, in this case, serves to lubricate and remove the iron filings, which would otherwise decrease the capacity of the stone itself.
Today there are apart from the stones a series of tools for those who do not have the skills or patience to acquire it and learn a valid re-sharpening technique that prevents ruining a knife.
Tools for clamp sharpening use a support with several holes, with predefined angles such as the Lansky sharpening system where the stone is mounted on a rod to be inserted into holes to keep the sharpening angle constant.
Another system is the crock stick, where two chopsticks are placed on a plastic or wooden base, so as to form a V-shaped angle.
When the knife is placed above the V, the angle is held until the blade is perpendicular to the base.
There are also even more professional systems that allow you to make excellent sharpening by controlling the angles and symmetries of the wire.
These are expensive tools but they allow you to have professional sharpening such as the Wicked Edge Generation 3 Pro.
There are homemade solutions such as the base of the ceramic cup but these are strategies to use if you have nothing available, it is not a method that I recommend if you have stones or other systems.
Everyone has seen this tool used in shops and supermarkets and some believe that kitchen knives are sharpened with steel
Actually this tool only serves to correct and maintain sharpening.
This tool realigns the molecules that make up the sharp edge, which have been displaced by continuous shocks, “restoring” sharpening.
If a knife is of quality and is made of a very hard material with a high Rockwell HRC that keeps the sharpening for a long time, the use of steel can also be superfluous because it does nothing.
Better to lose half an hour every two to three weeks, to sharpen the knives we use most often, rather than sharpen them with steel every time we use them to ruin them.
A good steel, which must have a very fine grain, can cost like a knife and can not replace a real sharpening with the abrasive stone.
If the material of the knife is not particularly hard, then it may be necessary to frequent use the steel to maintain a decent level of sharpening.
One more reason to buy quality knives.
Breve guida per affilare con le pietre
The secret of proper sharpening is the maintenance of thesharpening angle during the operation.
For this purpose there are special plastic guides that allow you to maintain a constant angle.
Some quality knife brands provide them with the knife so even the angle will be optimized according to the sharp ness of the knife.
1) Place the abrasive stone on a stand that does not allow it to slide on the support plane. Usually the stones are provided with a special rubber support.
2) Choose thesharpening angle for, for example, for kitchen knives that are common to maintain a 15-20 degree angle but follow the pattern you’ve seen before based on the type of knife and its type of use.
With higher angles the blade stays sharp for longer, but cuts less.
Larger angles are used for knives (such as cleaver) that have to cut hard objects such as animal bones.
Depending on the type of cut you need to apply it can be a good advice to have multiple knives with different sharpening angles to make the wire last.
To maintain the sharpening angle, use your thumbas as in the figure below as a reference: if the blade is smaller than 13-15 cm, it only takes one inch, for larger knives use both of them.
3) Apply a continuous, circular or alternating movement to the blade on the stone, being careful to keep the sharpening angle constant and to keep the blade always in contact with the surface of the stone.
To calculate the exact slope of the blade, rely on the following table:
measure the l width of the blade, and take from the table the height at which you need to place the blade on your thumb.
Important!! Always count alternating rotations or movements and repeat the same number from both sides.
The number of movements varies depending on the hardness of the steel of the blade, it takes at least 50, up to 100 for the hardest steels.
So the real key to a nice sharpening of the knife is a suitable and constant angle on the bevel of the blade.
This is easy to say, but difficult to make freehand, some make supports, use montetes, plastic supports.
There are 2 problems that you have to overcome and check:
- Trovare l’angolo corretto per il suo impiego.
- Creare quel angolo sulla pietra affilatrice costante.
Ecco una guida generale:
10 to 15 degrees
This is the extreme. Razor blades and scalpels are in this group. Even quality knives with high-tenor steel can take this thin angle of sharpening and hold it for a long time.
15 to 20 degrees
Angles in this series are great for knives that serve for slicing or in domestic work although many commercial kitchen knives are factory sharpened to about 22 degrees.
25 to 35 degrees
Many types of knife can fit well in this series. Usually sharpening with this angle is good for both openable and fixed blade in general, survival / bushcraft knives and for general use;
35 to 40 degrees
A cleaver sharpens well to 35 degrees (some sharpen it even at 25 degrees). So all those heavy work knife models, like Bowie, Machete, Accept, etc.
Controllo della lama per verificare l’affilatura
The blade is sharp enlated when the dross chip is formed on the edge of the blade.
You can feel it by gently passing a finger on the blade, in a cross direction (notalong the blade!), passing from one side of the cutting edge to the other (be careful not to cut yourself!): on the one hand the blade will seem rougher than on the other.
Remove the dross chip by gently passing on the blade a pumice stone, or an abrasive stone fineter than 600 grits or on a leather belt.
Once you have removed the dross chip, you can check if your blade is a perfect blade.
A perfect blade has the following characteristics:
– it is perfectly smooth: take a pen with plastic cap and slide the cap on the blade: you do not have to feel any step or obstacle;
– does not reflect thelight: look at the blade in front: the light must not be reflected by the blade at any point.
Also follow these 5 ways to see if the blade is sharp.
Learning to sharpen requires a lot of practice, a lot of practice.
Do not expect to get great results right away but try, try again and if you follow all the instructions calmly and precisely you will get a good sharpening.
In the house people always have knives that they do not use because they no longer cut ask people to let them give and sharpen them, exercise.
With time and experience, you will be able to get a blade with an incredible cutting ability!
Make a good sharpening!
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