Introduction: Kiridashi Kogatana Marking Knife - With a BBQ and Grinder
Before we start off, a little background on why I wanted to try out a knife making project.
As teenager I had a little hobby of collecting pocket knives, bacl then I was interested in the emchanics of an object so it didn't take long before I did some reseach how a knife was made. Ever since I wanted to try to make one!
I do not have wide array of metal working tools, not even a bench grinder. Also I don't have a forge or big propane torch. I do have a BBQ grill, multiple acctually and I sell them as a side hustle, so BBQ's in abundance :p But could I heat up steel hot enough to anneal or quench it?
So I set off only having a grinder and a BBQ.
A Kiridashi knife is a Japanese utility knife If I understood the internet correctly. It is the same as we would name a 'stanly' knife. I really like this design of a knife with one sided bevels so that's why I chose this design.
I have 1:1 plans and drafts available from my website so if you are interested check it out:
Step 1: A File
My friend Paul gave me an old file. So without spending anything I had small chunck of good quality steel. Steel from a file is quite good material because you can harden it by quenching it. After this hardening process the material is still tough, not too brittle so that is good combination.
Steel is always an combination of iron and a small amount of carbon, the small carbon particles strengthen the metal crystals. In the case of the file there might have been a small amount of chrome and vanadium. This is typical for a cost effective steel used in tools.
Step 2: Annealing
So Ilined op the BBQ and fired up the charcoal, put in the file without the handle. Positioned it in the hottest part of the grill waited for 1 hour and kept it at temperature, every now and then, by waving air with a news paper. Afterwards the steel was quite soft, I could 'file' this old file with a new file so you can anneal a file with your BBQ.
There are ofcourse temperature differencies in the grill so the whole file has not the same hardness. but in my case it functioned adequately.
Step 3: Make the Template
I made a design on paper just by drawing and experimenting with different shapes. I then put this design on a piece of thin wood. I check the size by putting the file onto the wood.
I used a coping saw to remove the facets of the design. With a standard file the round radius are smoothend and finished.
Step 4: GRRRinding Away!
With the pattern I could mark the desing onto the steel. I used a thin cutting wheel and started grinding away. The grinder made quick work of removing material so I did take care not too cross my lines.
I love the shape of these sparks, because the higher carbon content the sparks look 'fuller'
Step 5: Creating the Bevel
I made 'round' bevel on the knife, that way the tip of the blade was the sharpest. This will be a making knife so that is good.
Step 6: Quenching
I repeated the process of heating up the steel with the BBQ and made sure the tip of the blade was in the hottest spot of the grill. This time around the tip needed even be hotter so I kept adding heat until the steel was 'orange' hot.
At that point I put this in a glass container filled with light machine oil. When quickly lowering the hot metal in the container I was carful and mindfull the glass did not explode or the oil caught fire.
This process of quenching is actually trying to 'freeze' or forcefully holding the metal crystal in the most 'dense' configuration making the steel object harder. So with 'colder' oil the steel freezes in an instand to this configuration.
After quenching and everything was cool again I checked if the tip was hard. I tried to file it but I didn't succeeded. The file slide across the hard tip. After this you could temper the steel by putting it in an oven to soften it again and make it less brittle but the tip was nicely hardened the rest was tough so I skipped the tempering step.
Step 7: Sharpening
I used my oil stone to sharpen the tip of the blade. The trick is to keep your hands steady and the bevel in the same position while 'grinding' away the metal. I only got this right by practicing, you cannot fail in this step if you try hard enough and keep looking and assess if you sharpend correctly.
After this I repeated with a finer grit and ended by polishing the facets of the blade with a leather strop. I charged the leather with a green block of polishing wax, other colors are fine as well.
Step 8: Test!
And now check if it actually works!
The tip was sharp enough so knife lines could be drawn with it! The bevel is on one side so that's a bit different when using but it works conveniently enough!
I would encourage anyone to do this If you want to make knife the easy way!
I hope you enjoyed this!