But it should be taken into account that hardening leads, along with the strengthening of the metal, to an increase in its fragility.
Here is a screwdriver with the tip broken off. This occurred either from a large torque applied to it, or from improper hardening, which caused increased brittleness of the metal.
Let's see how to properly harden steel so that it becomes strong and not too brittle, and be sure of it. At the same time, tools such as chisels, chisels, etc. must also have a sharp working edge.
Will need
For work we will need the following materials and tools:
- container with water;
- gas-burner;
- mechanical emery wheel;
- file;
- 220 grit sandpaper;
- magnet.
Water for cooling steel after heating is often replaced with various oils and salt compounds.And with a magnet we will check, along with the color changing when the steel is heated, the sufficient hardening temperature, since when it is reached, the hot metal loses its magnetic properties.
That is, a specific color and lack of magnetization are sure signs of the end of heating of the steel and its cooling in water.
Hardening a screwdriver with your own hands
To harden a screwdriver, we first form a new end with a file and a sharpening stone, because after hardening the steel will become so hardened that the file will simply slide along it without cutting off the metal.
If the damage to the screwdriver tip is minor, then you can do without hardening. It is enough to process it on a grinding wheel for no more than two seconds and immediately cool it in cold water.
Using a gas torch, heat the end of the screwdriver with the newly formed tip. You can see how its color changes when heated, which is important for hardening. We will also check the readiness of the tool for magnetic hardening. It stops being attracted to metal when the temperature reaches 760 degrees Celsius and needs to be cooled quickly.
After cooling in water, you can see that the screwdriver is covered with carbon deposits, which we remove with sandpaper.
This is necessary for the tempering process, in order to observe the temperature by the tarnish colors that the oxides take on, and to cool the screwdriver in time.
To heat a tool without a plastic handle to 260 degrees Celsius, we can use an electric oven, placing it there for 20 minutes. Then, grab it with pliers and lower it into the water.
Under the influence of the gas burner flame, the color of the screwdriver changes from light yellow through others and becomes purple, then dark blue, reaching the tip of the screwdriver. This color becomes a signal to stop heating and cooling the screwdriver in the water.
The same blue color will be a signal for the end of heating of the spring steel, since its temperature will reach 288-316 degrees Celsius, while the purple color signals a temperature of about 260 degrees Celsius, used for tempering the metal if it has become too brittle.
To temper the knives, heat the blades until the color tarnishes from light orange to dark yellow, i.e., to a temperature of 148-177 degrees Celsius. Let's still have a light yellow color, after which we cool the knife in water.
We harden the tip of the screwdriver. When heated, a light yellow color first appears, then yellow, purple, when approaching the tip - light blue and, finally, dark blue, after which we lower the instrument into water.
We'll do the same with a dull chisel, starting by sharpening it with a file, and then hardening it when the end turns purple. Warm up carefully so as not to overheat the tip.
We warm up from top to bottom. Yellow appears first, then successively orange, purple and blue. After this, cool the chisel and clean it with sandpaper and a grinding wheel.
