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» »Hardening the cutting edge of the knife with graphite
I will tell and show you a simple way of hardening any knife at home. And then, I will not temper the entire knife, but only its cutting edge, which greatly simplifies the task.
Hardening the cutting edge of the knife with graphite

If you go into details, it will be more likely not hardening, but cementation, which aims to increase the hardness and wear resistance of the metal.

Knife edge hardening


Take a knife.
Hardening the cutting edge of the knife with graphite

We pass along the edge of the file, while paying attention to a dull sound and easy grinding of metal. All indications are that the knife is made of ordinary steel and has not been hardened before.
Hardening the cutting edge of the knife with graphite

For hardening, you need graphite. It is best to get graphite from the graphite brushes of a generator, a brush motor. Of course, I have not tried it, but you can also get graphite rods from finger batteries, simple pencils.
In general, we grind this graphite into powder in any way. Grinding is not particularly necessary, without fanaticism.
Hardening the cutting edge of the knife with graphite

Next, I need a metal base on which graphite powder will lie. I took a piece of galvanized profile from drywall.
Hardening the cutting edge of the knife with graphite

For the process of hardening the edges of the knife, you also need a power source. Ideally, this is a pulsed DC welding machine set to a minimum. You can also try to repeat the process using another source, a voltage of 30-60 AC or DC. There is still a dangerous option: use the 220 V network directly, in series with an incandescent lamp, but this is already fraught, so I do not recommend it.
Hardening the cutting edge of the knife with graphite

Hardening the cutting edge of the knife with graphite

Pour graphite. We connect the plus of the welding machine to the base of the substrate, and minus to the knife.
We set the inverter to the minimum settings and turn it on.
We begin the process of edge hardening. To do this, very carefully draw the edge of the knife along the graphite pile.
Our task is to: first - prevent the blade from touching the base. And the second is to prevent the burning of graphite. In both cases, the blade will be damaged.
Hardening the cutting edge of the knife with graphite

Hardening the cutting edge of the knife with graphite

Hardening the cutting edge of the knife with graphite

Ideally, the blade should be moved slowly, and graphite should flicker. Strongly the knife naturally does not need to be lowered.
As soon as you notice the contact point is warming up, immediately raise the knife.
Hardening the cutting edge of the knife with graphite

Hardening the cutting edge of the knife with graphite

The whole process does not last relatively long, about 5 minutes. During this time, I managed to walk several times along the entire length of the blade.

Knife hardening result


Hardening the cutting edge of the knife with graphite

Take the file and shuffle the blade as the first time. Immediately audible sound is heard, indicating the high hardness of the metal. Plus, the edge is almost impossible to process.
Hardening the cutting edge of the knife with graphite

We cut a glass jar.
Hardening the cutting edge of the knife with graphite

Notches leaves bless you!
We knock on a steel nail.
Hardening the cutting edge of the knife with graphite

The result is excellent - there is not a scratch on the knife.
Hardening the cutting edge of the knife with graphite

In the end, I chopped a nail with a knife, hitting it with a hammer.
Hardening the cutting edge of the knife with graphite

The knife was not hurt!
I'm not a big expert in hardening steel, but the method really clearly works. Local craftsmen say that such hardening increases the hardness of the metal section to almost 90 units.I can not disagree or refute, since there is no hardness tester. If you have questions or suggestions, as well as comments - write in the comments. Good luck to all!

Watch a video of the knife hardening process


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Comments (8)
  1. feelloff
    #1 feelloff Guests 23 november 2017 14:16
    6
    I do not recommend using mains voltage -

  2. Oltaviro oltaviro
    #2 Oltaviro oltaviro Guests November 24, 2017 12:04
    1
    “Ideally, the blade should be moved slowly, and the graphite should sparkle twinkling” - how exactly should the graphite sparkle?
    1. Valentine
      #3 Valentine Guests November 24, 2017 1:04 p.m.
      3
      I always wondered where such pseudo clever people come from. It is clear to everyone - to spark without burning an arc.
  3. Vladimir
    #4 Vladimir Guests November 26, 2017 11:59
    3
    If it turns out, then it is possible. The problem is that the powder does not conduct low voltage current. Even metal filings (Popov’s experiments with the barter) Most likely, not all the powder, but some are pieces for seeding the arc. The polarity is correct - the anode dissolves. Cemented steel is brittle with high hardness, in the production depth of 1-3 mm for subsequent processing, hardening and grinding.
    1. Guest Andrey
      #5 Guest Andrey Guests December 4, 2017 12:44
      3
      But only 90 units will not work, the maximum is 60-63 HRC. It's just carbon, albeit cemented
  4. Rozakhusainov
    #6 Rozakhusainov Guests December 22, 2017 07:45
    2
    Super! Exactly what is needed.
  5. Guest Yuri
    #7 Guest Yuri Guests May 25, 2019 12:39
    0
    This is not graphite, but coal powder. Graphite is gray and slippery to the touch, it is necessary to look for graphite brushes. They leave a mark on paper no worse than a pencil. A pencil lead does not work, there is a lot of clay. Or, if possible, contact the nearest foundry, there is an abundance of ground graphite on it.
  6. Skeptic
    #8 Skeptic Guests July 17, 2019 2:54 p.m.
    0
    What the hell is hardening - on the face is cementation of the product, and not the highest quality ...

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