How to sharpen a knife
It is told about the preliminary sharpening of knives with a simple file.
We will talk about budget universal, tourist and kitchen knives that you need to work with, and not set cutting records.
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• Как ЗАТОЧИТЬ НОЖ
With a strong bluntness, the knives are first sharpened - previously - on an abrasive with a large grain. Usually sharpened on grinding machines.
This method has several disadvantages.
1. Not everyone has a grinder.
2. When processing, you can overheat the cutting edge of the knife and release it.
3. There is a lot of metal removal on the wheel, so the blade wears off quickly and becomes narrow.
4. You have to sharpen blindly, the surface that is being processed is not visible, and therefore it turns out rough and uneven.
5. There is not always convenient access to the abrasive wheel due to the electric motor.
I suggest sharpening knives first with a simple file.
Many sharpen on a sharpening machine, because they think that the knives are hard and the file will not take them.
For kitchen, universal, tourist knives, a hardness of 48-57 HRC is recommended.
I measured the hardness of different knives and found that it is, indeed, for all knives within 50 HRC, from 44 to 56.
Files take material of such hardness.
Knives don't make it harder, because otherwise the material of the knife will be brittle, and the edge of the knife may chip, like on this razor.
And with low hardness, the cutting edge can bend, like this knife.
To prevent chipping or bending, it is necessary to sharpen the cutting edge with a more obtuse angle.
But then the knife will cut worse.
A coarse file (bastard) can sharpen softer steels, and harder steels must be sharpened with a personal or velvet file.
The removal of metal with a file is small, and the knife grinds slowly, the knife will last for a long time. A knife is shown, which was sharpened on a grinding machine, the blade has already become quite narrow.
If the knife blade has a coating, then on a grinding machine, blindly, it is easy to tear off this coating, spoil it.
File work does not have all the disadvantages of grinding on a grinding machine, which were mentioned earlier.
Shows how I sharpen a knife with a file. It is convenient to maintain the desired angle with a file. The metal removal process is clearly visible.
But after the file, as well as after the grinding machine, the cutting edge is rough, rough. This is clearly visible under a microscope.
Therefore, it is necessary to sharpen the cutting edge completely. I sharpen on sandpaper of different grain sizes. First - more grit, then - less. And finally I polish and fill up the cutting edge on the skin with GOI paste.
It is shown how the cutting edge looks under a microscope after processing with sandpaper of medium grit and after polishing.
My advice: pre-sharpen household knives with simple files.