SOTW #6 - Yaki-Ire - A Tanto Blade is Born
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- Опубліковано 9 лип 2024
- islandblacksmith.ca/process/
Process of Clay Tempering a Tanto Blade
Once the steel is shaped as much as possible in its softer state, it is coated with a thin layer of clay along the edge and a thicker layer on the body and spine. During the hardening process, the split second difference in cooling time caused by the clay layer creates two different hardness areas in the same piece of steel. The edge cools faster and forms a very hard steel structure called martensite while the body cools slower and forms a very tough steel structure made of ferrite and pearlite. The boundary between these two areas is called hamon and is commonly seen as a frosted wavy line down the length of a polished sword blade.
When the clay is fully dry, a charcoal fire is used to heat the steel slowly and evenly, taking care not to overheat any part of it and working in the dark for accurate colour viewing. First the spine is heated to bring the whole blade to just below temperature, and then it is flipped over to focus heat on the edge. When the entire edge is at the correct temperature, it is plunged into a hot water bath, edge down, and held until cool (yaki-ire). The hardness is checked with a file and the process repeated if necessary. After hardening, the clay is removed and the steel is heated slightly again to remove some of the internal stresses (yaki-modoshi). Once this process is finished, and if the steel survives, the blade is ready for Togi, hand polishing.
more: islandblacksmith.ca/process/ya...
islandblacksmith.ca/process/
Process of Clay Tempering a Tanto Blade
Once the steel is shaped as much as possible in its softer state, it is coated with a thin layer of clay along the edge and a thicker layer on the body and spine. During the hardening process, the split second difference in cooling time caused by the clay layer creates two different hardness areas in the same piece of steel. The edge cools faster and forms a very hard steel structure called martensite while the body cools slower and forms a very tough steel structure made of ferrite and pearlite. The boundary between these two areas is called hamon and is commonly seen as a frosted wavy line down the length of a polished sword blade.
When the clay is fully dry, a charcoal fire is used to heat the steel slowly and evenly, taking care not to overheat any part of it and working in the dark for accurate colour viewing. First the spine is heated to bring the whole blade to just below temperature, and then it is flipped over to focus heat on the edge. When the entire edge is at the correct temperature, it is plunged into a hot water bath, edge down, and held until cool (yaki-ire). The hardness is checked with a file and the process repeated if necessary. After hardening, the clay is removed and the steel is heated slightly again to remove some of the internal stresses (yaki-modoshi). Once this process is finished, and if the steel survives, the blade is ready for Togi, hand polishing.
more: islandblacksmith.ca/process/yaki-ire-clay-tempering
Bueatiful blade, beautiful vid, beautiful process! Loved it, please keep them commin! :)
Beautiful blade work.
Good video
I have a question, I'm making a tanto out of a hot rolled steel. Not forging, just using a file to shape it. But I am now on the step of clay tempering. Is it okay for me to quench hot rolled steel, or will it crack?
depends on the type of steel (carbon content and other alloying ingredients) but if it is called hot rolled steel (mill finished) it is likely structural/mild steel, so quenching won't crack it and will only very mildly increase hardness and won't produce a hamon...here are some tests to use before starting the next knife project: islandblacksmith.ca/2016/12/testing-reclaimed-steel-for-knife-making/
Why do you close the doors every time you quench something? Is it so the wind doesn't cool the piece before you get to the quench? Is it so you can see the colour of the steel more accurately to tell if its ready? Or is it just a tradition from japan?
yep, it is for lighting conditions to be consistent...exact colour is very important at this stage...and it is a tradition from japan as well, for the same good reason. ^_____^
Ah, it makes sense. Nothing is done if it didn't work.
Thanks for the reply~
yes, the proper form of tradition is a way of preserving knowledge, even for those who don't understand, to be able to pass along to the next generation...
Boa tarde gostaria de saber qual o produto usado que o sr. passa na lamina da Tanto . Por acaso e massa Termica ! .
~1:1:1 clay, charcoal, ground sand or stone powder...but it takes some experiment and testing... islandblacksmith.ca/process/yaki-ire-clay-tempering/
Are you no worried about your steel cracking during a water quench? Ive used leaf spring steal for a knife and quenched it in water and it cracked. I just forged a tanto for a friend and I used high carbon steel from a leaf spring for the edge. the rest imild steel folded over. do you just heat up the water or something before the quench? I would use oil, but I want to keep the process as authentic as possible.
always! modern leaf spring (made in the last 100 years) is not designed for water quench, the springs i am using have less alloy so they behave differently...but still a risk, yes! there are many parameters that can cause cracking, water and temperature are two of them...each piece of steel should be tested to learn how to best water quench it before you commit to sacrificing a fully completed tanto...try used file steel...
oh ok thank you. one more question, do you have to use water for a quench if you want a successful hamon line? or will oil work too. thank you
i don't know about oil, i am only studying the traditional japanese swordsmithing method with charcoal, clay, water...
Can a khukri knife be tamper like tempering a katana?
i am sure it can with some practice...it must be made slightly more curved because the quenching will straighten it a little bit...
Why do you use hot water over cooler water?
based on my observation, it seems to be about the formation of the vapour jacket, which affects how quickly and evenly the heat transfers from the steel to the water...similarly, in traditional water casting (yuwake), the water must be very hot, just off the boil, or the molten copper/shibuichi will cause trouble with steam explosions and cooling rates...
islandblacksmith.ca/process/yaki-ire-clay-tempering/
question for you, I've clayed up a blade twice, consisting of the 1:1:1 clay, charcoal, and sand in your tutorial. But once I come back it's dried in a way that it separates and curves off the blade for some reason. on both sides. it's about 2 mm thick. any ideas why? too warm when drying maybe, I do leave it inside to dry
2mm is plenty thick, a bit thinner might be better...1:1:1 is just a starting point, you may need to adjust to your ratios slightly, use some test scraps at first...
Thanks alot. Appreciate it
Crossed Heart Forge - islandblacksmith Got another question. I adjusted my clay and worked great! I'm using 1080 and I'm on to tempering, I've tempered it 3 times at 400 for an hour and the blade is definitely straw gold color but the blade still resists a file. the part that is clayed up is soft but I can't work the edge to bring it to its angle that it needs to be. should I just continue to do intervals of an hour at 400?
you will never be able to file a properly hardened and tempered blade...3 rounds is plenty enough, just gotta get out the waterstones and set your final geometry...
Crossed Heart Forge - islandblacksmith 👍 thanks for the fast feedback!
Very good work just two questions i did the same process on a yanagiba and it cracked in 9... this was white paper steel the temperature looked ok to me i heard that clay thickness was a matter as well because i put kind of a lot of (clay charcoal powder and lime stone powder) any idea of what wet wrong? Maybe water was too violent? and which steel did you use?
if you used white paper you probably didn't do the *exact* same process or you might have succeeded...there are many many parameters that can cause cracking; water and steel temperature are two of them, also steel thickness and geometry, hamon size and style, thickness and composition of clay, preparation of the steel and evenly heating...each new type of steel should be tested to learn how to best water quench it before you commit to sacrificing a fully completed blade...keep at it, the journey toward excellence is long but worth the effort!
Yes that's true but since white paper is expenssive and hard to find i didn't want to "waste" it even though i should have. By the way i realy apreciate your work i learnt a lot from it
i recommend experimenting and practicing on old files as your source steel, similar ingredients to white paper, not so hard to find (usually for free), and make great knives...when you get down to one or zero cracks, try the whitepaper again!
You say this to the right moments i just picked up a dozen files for free
excellent! step one may be to do some temperature tests in controlled lighting conditions and learn the lowest possible temperature you can use and still harden the steel...and when you try hamon for thinner knives very hot water is safer, like a very hot hotspring bath...
more sharpening? I have seen the traditional setup I wonder about a simplified version. hmm.. theres a lot of sharpening vids but nothing premium. I use the shapton 1k - 12k all the steps.
on the long term list...but my recommendation is keep it simple, murray carter advocates two stones and a strop on newspaper, simple and good...
Just ordinary clay do you use?
yes, ordinary clay...mixed with charcoal and polishing stone powder.
Thanks a lot. the proportion is the same of the three items (1/3 clay + 1/3 charcoal + 1/3 stone powder)?
Or it doesn't matter?
that is a good starting point, with some adjustment to your personal needs...
Thanks again.
And again, congratulations for the wonderful job.
what are the temperatures for quenching and tempering?
Urban Vrhovnik what we used here in the Philippines is regular water straight from the tank or well.. our average temperature here is about 27 Deg. Celsius to 33 gets hotter in summer.. if you live in very cold country, I guest you could adjust the water temp there just like here.. it could work for you but knows.. but I guarantee you it always worked here in the tropics..
each smith has their own method and preference for water temperature and tempering, and even quenching is somewhat subjective...each known steel has a specific critical temperature chart but unless you have an accurate method for measuring quenching temperature a number isn't going to help very much ^______^
Does the clay on the blade vitrify or is it just caked?
a little bit of both, depending on the mixture and the steel it is close to the line...but it is usually quite hard when it comes off...
I really enjoy your videos they are so meditative and relaxing and all the varied skills and techniques are so fascinating. I enjoy that the sound is just the sound of a hammer on metal or chisel cutting wood and the occasional turkey, that said the other day I was picturing what it would be like if it was cut to an hour long for television and narrated by Liam Neeson or the late John Hurt.
much appreciated! haha, i wonder!
water is very good in quenching but requires training.. it can easily crack metal during the process.. here in the Philippines water is the most oftenly used...
yes, water can be quite difficult for some steels, but worth the challenge i think!
Q es lo que le pone al comienzo? ??
natural clay, charcoal, and polishing stone powder: islandblacksmith.ca/process/yaki-ire-clay-tempering/
Hello thanks for video, what tou use at minute 0:27
natural clay, charcoal, and polishing stone powder: islandblacksmith.ca/process/yaki-ire-clay-tempering/
Crossed Heart Forge - islandblacksmith thanks
Where are you come from
I like your videos and work; what steel do you typically use?
1085 or 1095
for the satoyama knives i use old files or harrow teeth, for the classical tanto i use steel that is 125+ years old so it doesn't have a number, just simple iron and carbon, shear steel if i can find it...
すごいよ！お前は鍛冶を何と学びましたか。
ありがとうございます。。。i still have much to learn! ^___^
Crossed Heart Forge - islandblacksmith Sorry, I got excited and assumed you knew Japanese. How did you learn Japanese blacksmithing?
^___^ i had a pretty good idea from your writing that you were not in your first language either...it is a long journey, with a long ways to go yet! がんばて！
覆土烧刃666