The performance of a pencil sharpener depends on the characteristics of its blade. If it is made of bad steel or hardened incorrectly, then its edge quickly wears out. Here is an example of useless work:
The slice turned out slightly curved, the rod is slightly broken.
The situation can be corrected by giving up the heat treatment blade, and then sharpening it. This is painstaking work, perhaps even inappropriate for a conventional sharpener, but it will give an excellent experience that can be useful in the manufacture or improvement of knives.
Materials and tools:
- crosshead screwdriver;
- sunflower oil;
- polishing paste;
- sharpening angle holder.
Heat treatment and sharpening of a sharpener blade
The secret of an ideal cutting tool, in addition to good steel, lies in its proper heat treatment. The blade must be normalized, hardened and tempered. Normalization will make the metal structure uniform and relieve internal stress. Hardening will give the hardness that is needed to maintain sharpening. Vacation will return plasticity to the solid blade so that it does not break.
Remove the blade from the sharpener and place it over the fire with a screwdriver.
Since it is very thin, the combustion of gas is enough to heat steel to raspberry color. After that, the blade is removed from the fire and left to cool in the air. This will normalize the metal. If the blade has factory defects, it can be forged a little while it is hot.
The cooled blade warms up again, but not to the crimson hue, but to the appearance of a light orange color.
As soon as it is sufficiently heated, it is thrown into room temperature water for quenching.
Next, the hardened blade must be low tempered. To do this, it is rushed for 1 hour in vegetable oil heated in a frying pan to 200 degrees Celsius.
It is important to maintain just such a temperature throughout the hour. If there is no thermometer to control, then you can simply throw the blade into a container with oil in the oven with a thermostat.
The blade is ground with water on a grindstone with 2000 grain.
Then it is clamped in the angle holder and sharpened on the same stone in the direction along the edge.
Gradually, you need to switch to abrasive with finer grain. In the example, stones “6000”, “8000”, “12000” and “30000” are used.
At the end, the blade can be polished with a paste to make it look like a mirror.
Subject to proper heat treatment and sharpened to a mirror shine, the blade can perfectly grind pencils. It cuts paper perfectly.
Install the blade in the sharpener.
The hard metal of the cutting edge will cut for a very long time without the need for re-dressing.
Pencils now sharpen just perfect.
Such a sharpener is now enough for many, many years.