DIY Kiridashi Knives

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Introduction: DIY Kiridashi Knives

About: I am an industrial designer and a maker. I like to make prototypes, unique pieces, equipment and other stuff. In this channel I will show you what I do, and in particular the making of design pieces, with v...

Some time ago, I spent some relaxing days at my country house. I thought to make something with the few tools available there. What I had at hand were some tool steel and a small self-built forge. So I thought to make a couple of Kiridashi knives. The Kiridashi knife is a traditional wood carving knife, widely used in Japan. But it also is a marking knife, used by almost all the Japanese carpenters, as well as a versatile tool for general use.

Translated to English, 'kiridashi' means 'to carve out' in Japanese.

Step 1: Choosing the Right Steel

The knife steels I had at my disposal were some C70 (Aisi-1070) and some K720 (Aisi-O2). I chose to use a 5mm thick K720 because it is harder than the C70 and therefore more suitable for a knife like this that requires little flexibility but great sharpness.

Step 2: Marking the Steel for the Cuts

To begin with, I secured the metal to a desk with a C-clamp. Then, using a paper template and a Sharpie marker, I marked the shape of the two knives to be made.

Step 3: Cutting Out the Pieces

I then cut the two shapes with an angle grinder and a cutoff wheel. This operation is quite simple, you just have to be careful not to bend the wheel of the grinder and not to apply to much force when making the cut.
Always remember to wear all the necessary safety equipment when using an angle grinder. A face shield, in particular, is recommended.

Step 4: Hammered Decoration

I thought I would add a hammered texture on one of the two knives. This is for an aesthetic effect but also for a more secure grip. To do this I used a small forge built by me. The construction of the forge is very simple: I used a coffee can inside of which I poured some refractory cement. The heat source I used is a propane torch connected to a small gas cylinder. I then heated the knife to a red cherry color, hammering it repeatedly over a small anvil, made from a piece of railroad track.
During this operation, the knife tends to bend, so be sure to straighten it as far as possible before proceeding to the next step, otherwise sharpening will become almost impossible.

Step 5: Grinding the Main Bevel

The next step, after wearing all the necessary protections, was to create the main bevel of the knives. To do this I used a portable belt sander, mounted on a table I made.
The bevel should not create a sharp edge, at this point. It is necessary to leave about half a millimeter thickness to avoid ruining the knives in the next hardening step.

Step 6: Hardening

The hardening phase consists of bringing the steel up to the temperature where it no longer attracts a magnet, then quenching in oil. For this type of steel, the ideal temperature is about 800° C (1472° F), which corresponds to a cherry red color. For quickly cooling it (quenching) I used a canola oil at a temperature of about 50° C (122° F). I apologize for the dark image, but it helps to better understand the color of the metal at the moment of the quench.

Step 7: Tempering

Now the steel should be very hard so that a file should skate right off of it without leaving a mark. But it is also brittle, so it is necessary to temper it to give it some elasticity.
Not having to make the knives particularly flexible, but opting for more hardness, I put them in the oven at 200 ° C (392 ° F) for 60 minutes.

Step 8: Pre-sharpening

At this point, the knives can be sharpened. After the hardening, however, it is necessary to avoid overheating the metal because too much heat on the blade will damage the heat treatment previously made.
The belt sander can still be used but with a fine paper, a low speed, and continuously wetting the blade in fresh water. As you can see from the photos, I do this with bare hands so that I can immediately feel any increase in the knife temperature. First I flatten the bottom of the knife, and then I sand the bevel until it meets the flat surface of the underside. This is a pre-sharpening because the final sharpening have to be done manually afterward.

Step 9: Final Sharpening

For the final sharpening, I first used some diamond stones, up to 800 grit and then a couple of Japanese water stones, up to 6000 grit. For the final polishing, I used an abrasive paste on a leather strop.

Step 10: Final Shots

Here you can see some shots of the finished knives.

In the video on my YouTube channel, you can also see the cutting tests I've made to see the functionality of these knives, as well as have a better perception of the various steps.

Thank you for checking out this build.

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    42 Comments

    I agree, I think these knives will do great with a crowdfunding campaign : )

    Thank you very much for sharing this, I am going to attempt making some for my brother this year as for a Christmas present (he is mad for all things Japanese).
    I will post some pictures in November if I am successful :D
    Just 1 quick question you mentioned you heated the blades to 800 degrees, did you do this with the same home made furnace that you used to create the dimpled effect earlier in the video?

    Thanks again

    Chris

    I tried my hand at making a few knives when I was in my gunsmithing phase of my life, a couple turned out passable, one with real stag handles and one using walnut from an old gunstock. For steel, I used old files that had passed their use by date and no longer filed as well as they should have. It was great fun but when my blasted belt sander broke free from it's stand, and I did the natural thing and tried to grab a running belt sander to keep it from crashing into the floor. Man what a mess my right hand was; really messed up my day and put an end to my knife building days. My hand did eventually heal up, and you can't even see the scars any more, but I gotta tell you, that year when I wet to qualify with my hand gun, shooting left handed worked but I didn't get my normal average, instead of tying for the top where I usually did, I nearly tied for low score. That said, I am now stronger then ever in the weak hand portion of qualification.

    5 replies

    One thing I learnt in my early twenties is to never try to catch a flying jigsaw. When cutting out a laminate worktop for a glass kitchen hob I lifted the jigsaw when the blade was still active. The jig saw blade just nicked the work top and flew forward. Instinctively I went to stop it with the left hand, but cut through the leather glove I was wearing right through to the bone on my wedding ring finger.

    I consider myself lucky I didn't take the end of my finger off.

    Rule number 1 if anything can cut and its moving treat it safely as it will always find skin and bone

    It sounds painful! Thank you for sharing your experience.

    As he brought forth a real Hazzard I would suggest using a foot pedal switch for the sander that way if the sander breaks away as his did you step off the foot switch and the power is turned off !!

    The first rule I learned in wood working, metalworking is "Let it fall."

    When a heavy object that you own falls in your proximity, you no longer own it until it is stopped on the ground, it owns you.

    I work with glass (and knives) - never, ever catch a falling sharp (or buzzing) thing. I grabbed a piece of falling plate glass I was working on and let go immediately - my fingers were sliced to the tendons, but did not actually touch the tendons. It scared me spit-less but I learned; now, as soon as something begins to fall, I step back and let gravity take its course.

    Is a beautiful job and need a lot of patience I imagine the Samurai maker congratulations and God bless,

    1 reply

    Those are beautiful! I would display them as art!

    1 reply

    Very
    Nice Job. I have made similar knives using old turbine blades from our
    ships exhaust system

    Nice work! Love the hammered finish. Good explanation of your process.

    1 reply
    user

    Very nice. I'm curious about the hammered pattern. Did you just use a ball peen hammer or something that has a texture to it?