Oroshigane......making steel (1)

The weather gods have shown pity on us and granted a brief window of dry weather, just enough time for me to gutter the new roof…..and explore a new rabbit hole. With the drainage under  control, it's time for me to shift gears a bit and take on something that I've been wanting to try for years; making steel.

Why would anyone want to make their own steel when so many excellent carbon steel alloys are widely available? Is homemade steel better in some way then what is already out there? In a word….

No.

So then, why put time and effort into  working with such a ridiculously crude and outdated a material? After all, this is essentially a backdoor production method that hasn't seen the light of day in nearly 300 years. I could go on about the mystical alchemy inherent in the transformation of iron to steel, the connection to ironworkers ages past etc, and while that is certainly true, the short answer is that it's just plain cool. Come on now….who wouldn't want to make their own steel?

In the Japanese swordsmithing tradition, the blacksmith can select a variety of different steels and re-melt them into a more easily worked form. This blacksmith made steel is called Oroshigane, and while I am not especially interested in making swords, I AM interested in their steel. Broken blades that shatter during the quench, old cast iron teapots, even the steely crumbles that accumulate in the bottom of the forge, all of this can be combined and blended to create a steel with the specific qualities desired. Call it extreme up-cycling.

It's all about the carbon

Steel, at its heart, is a simple compound of elemental iron and carbon. The amount of carbon added to the iron is very small, but it's impact can be huge. Take iron and add only 0.2-0.3% of carbon and the result is mild steel, the most common structural steel in use. Kitchen appliances, “wrought iron” furniture, the list goes on and on, but most of what we see on a daily basis is made of iron that has been made tougher by a miniscule addition of carbon. Add 0.4-0.6% carbon and you start getting a steel that can be made harder and therefore suitable for more extreme duties. Car axles and shafts, hammer heads, nails, lawnmower blades, wrenches….generally medium carbon steel.

The sweet spot for carbon steel, at least for cutting edges, is around 0.8-1% carbon. Knife steel, Western woodworking plane blades and chisels, old car springs and such fall into this group. Steel with more than 1% is more of a rare animal, but Japanese woodworking tools (planes and chisels) generally use this very high carbon steel, likewise taps and dies, and some metal working files.

At the higher end of the carbon steel spectrum, steel with carbon in excess of 0.8% makes the material more difficult to work. Forging is physically harder as the material just doesn't like to move, even at a high forging temperature. Forge welding becomes more difficult too, particularly when joining wrought iron to steel as my favorite tools do. Without delving into the metallurgy, any carbon in excess of 0.8% has the potential to cause trouble, unless the smith really knows what they are doing.

Add 1.2%-2%% carbon and steel turns into a tricksy thing, and can exhibit a range of traits not normally associated with traditional carbon steel; superplasticity, extreme toughness, impact resistance and high elasticity…...all the while maintaining a very high degree of hardness. Again, this assumes that the blacksmith is highly skilled. Some of the tool steels used in laminated kanna blades use this UHCS (Ultra high carbon steel is the term) for the cutting edge, laminated to antique wrought iron.

A carbon content upwards of 2% is termed cast iron, and while cast iron is a wonderful thing for pots and pans or engine parts, it's of no direct use in hand forging. As the carbon content of iron rises, the melting temperature falls (a trait that will come into play shortly), so having a very high carbon content allows iron to more easily become fully molten, then be poured into a mold….cast into a usefully shaped component.

So, why all all of this blather about carbon content? At, or near melting temperature, iron is able to either take on (or lose) carbon, and that's what the oroshigane melting furnace is for.

This small shaft furnace heats the iron to a partially molten state as it descends towards the bottom of the column. Wood charcoal acts as both the fuel source and adds the carbon component, all brought to a furious heat by an air source that increases the rate of combustion. The concept is a simple one but, as they say, God is in the details. Shaft volume, air volume and pressure, carbon content of the starting materials, even the size and type of charcoal is important.

Of most importance perhaps, is the height above the floor where the air blast enters the column. The temperature of the furnace is highest proximal to the air inlet, so if your furnace floor is at a level with the air inlet (Tuyere is the term), the molten metal will be getting the full force of the air blast. This will actually burn out carbon, so if you are trying to lower the carbon content of cast iron to a more forgeable level, that's where you want to be. If your aim is to raise the carbon content to make some cutlery steel, you want the iron to be able to fall through the heat zone and collect underneath the air inlet, where it sits and absorbs more carbon, eventually resulting in...cast iron.

I'm just getting going with this, both the steel making and the long winded particulars. If you are truly interested in this field of inquiry, there are a few places to go, materials to read. Here's the shortlist …...

Jesus Hernandez wrote up his experiences forging a blade out of steel made in a so-called “Aristotle” furnace. The swordsmith’s oroshigane furnace I made is nearly identical to this, and it was in reading this forum thread that I first became really interested in making my own steel.

— BROKEN RECORD WARNING—

This thread is a perfect example of how information is disappearing daily from the web. If you find something of interest, document it well, because the original information might be gone before you know it. To view this post in its entirety with all of the important images, you need to go Wayback……the Wayback machine will take you there. Donate if you can.

A new way to make steel

https://web.archive.org/web/20150329053128/http://www.bladesmithsforum.com/index.php?showtopic=11327&page=1

Bladesmiths forum is one of my favorite resources for edgy inspiration. They have a whole topic section devoted to smelting ore and making steel, tons of information here….

https://www.bladesmithsforum.com/index.php?/forum/25-bloomers-and-buttons/

Daniel Cauble has had some laudable success in making his own oroshigane, really inspiring work, beautiful steel.

https://www.bladesmithsforum.com/index.php?/topic/36558-picture-hvy-some-of-my-orishigane-for-japanese-blades/

But my main source? The Japanese swordsmith Sumihira gifted us with actual particulars and details of how he raises and lowers carbon content in his work. It is from his writings that I got the measurements for my little furnace. Gold!

The forging process, beginning with making the oroshigane (Google translates oroshigane as “wholesaling”, but you can figure it out….mostly).

Sumihira process of the Japanese sword

Lowering the carbon content of cast iron = sageba = ”lowering place”

Sageba, lowering carbon

It's a start. More to come….

Rainy days getting you down? Build a Japanese blacksmithing bellows!

Thinking rationally for a bit, I realize that it doesn't REALLY rain every day here but…...it feels like it's been forever since we last had a solid day of sunshine. Rainy days are particularly bothersome for us in our open-air lifestyle ie: no windows that close, no doors and certainly no heating or dehumidifiers. Everything here is out in the open, and while that is nice when the weather is beautiful and sunny, wet days kinda suck. Three weeks of rain REALLY sucks!




There is a goodly long list of things that need doing ( replacing our sketchy tarp roof with real roofing, building a new bedroom addition for our soon-to-be teenage daughter, etc,etc,etc…..) but some tasks are better off being confined to drier days. Wooden body kanna tend to swell a bit in high humidity and can get out of whack. Lumber twists and warps, not a big problem for framing, but definitely a bad day for finer furniture projects. I don't know about you, but I hate working out in the rain anyways, so framing is out. Finish applications are verboten in this weather but given that I haven't built anything finer than a plywood box in God knows how long, that's pretty much a moot point. I can dig stuff up using the  backhoe, as long as it's not raining too hard. Sharpening tools is a good rainy day project. Working at the forge is a great thing to do on cold and dreary days. Now, if only I had set up the forge sooner……


I bought the materials for putting together a forge blower using a bathroom ventilation fan, oh, two years ago I think. Ventilation fans are high volume, low pressure, pretty much the opposite of what you really want in a forge blower, but since I'm doing all my forge work using charcoal, the bathroom fan is adequate. Best of all, it's really quiet. The thing that I DON'T like about using an electric fan is that, unless you install a momentary-on foot switch, you are burning up fuel constantly. When you are producing all your own charcoal, that's a real concern. A human powered forge bellows only makes air when you need it.

When working tool steel at the forge, temperature control is crucial so you need to regulate the air supply to make the fire hotter (or less so). You can install an inline gate valve to restrict the air volume, but the simple shaded pole induction motors used in small bathroom fans don't really like the increase in back pressure. You can wire in a rheostat, but they don't really like that either. Either of these means will work, so if that's all you got, work with it, but it's not exactly ideal. Bathroom fans use electricity of course, and that's something that is in short supply in our off grid lifestyle, so although that's another factor for me, it's probably not so much of a concern for you, hahaha.



So…..it's raining again, and everyone needs a rainy day project, right?



One of things holding me back from building said forge is my oh so strong desire for a proper Japanese blacksmith bellows ( 鞴 [ふいご (fuigo)). You know…..that funny wooden box that you see sitting to the left of the forge in nearly any Japanese blacksmithing video.

I've been wanting to build a true Japanese fuigo for a long time, pretty much as long as I've been interested in forging tools. One slight hang up though, is that there are very few resources for the details of their construction. Search the internet in any language you choose and you'll find a few examples of fuigo that others have built but they have been, shall we say...simplistic in design? A traditional Japanese fuigo box bellows IS a simple thing, being essentially a box (duh!) and piston, with a few flapper valves that keep the air moving in the direction you want to it to go. There are a few hints of construction to be found that indicate that the Japanese fuigo has some details that aren't obvious to the casual observer.


Here is a couple of links to a repair that was performed for the Miki city ancient rite preservation society.

Fuigo repair (1)

Fuigo repair (2)



The fuigo being repaired had been used by one of the most highly regarded Japanese toolsmiths, Chiyozuru Sadahide I, a name that is well known to any Japanese tool aficionado. It's hard to find a more legitimate example of fuigo construction than this, and those blog posts highlight a few interesting details.

• The long sides of the fuigo are bowed inward in both height and width (although just how much isn't specified) to better resist the force of air pressure.
• The flapper valves are tapered, thin at top and thicker at the bottom, and are covered with rice paper to provide an improved seal. Dave Friesen of Island blacksmith did an excellent write up of this detail here……making-valves-for-fuigo-box-bellows
• The long side panels of the fuigo are only about 9mm thick and are made up of two planks of cedar glued and reinforced using iron pins (like brads or dowels, but I can't find any pics of that detail).

Some interesting clues, to be sure. But that's not all…..


This YouTube video highlights a reproduction fuigo, skillfully built by California craftsman John Burt.

Making a Japanese box bellows

This reproduction fuigo was built for the upcoming United States visit of another well known Japanese blacksmith, sawsmith Miyano Dai Endo, better known on this side of the ocean as Yataiki (You can read more about Yataiki at the Daiku dojo website http://www.daikudojo.org/Archive/gallery_yataiki/)



The YouTube video mentions the bowed sides of the traditional fuigo, but also says that the bellows is tapered in length, a full 5mm from one end to the other. That's interesting……I wonder what else there is to learn here.






A few years back, Gabe Dwiggins of Granite Mountain Woodcraft wrote up the best fuigo build ever.

http://granitemountainwoodcraft.com/category/fuigo/


To top that off, the next year he drove all the way across the country to visit with Japanese saw metate Mark Grable and while there, took detailed and meticulous measures of a REAL Japanese box bellows.

There are clues here, to be sure. More than clues actually, because Gabe was able to get accurate measurements.

hirotas-fuigo

Ironically, this fuigo is the exact same bellows that John Burt copied in that YouTube video... cool! Small world, isn't it?

Gabe, being the awesome guy that he is, took it upon himself to draw up detailed plans, then shared this hard earned bit of intellectual gold with others. It's taken me far too long to get going on this project, but it's finally time to build this sucker!

I'm not going to give a step by step build log, because I suspect that Gabe has one of his own in the works (and if not…...hint hint!) , plus he will do a much better job of detailing this important tool build, far better than I ever could. I am just digging the opportunity to build something I've wanted for quite some time and didn't even need to do the difficult design work. I can't think of the last time I got to built something to a plan, haha.

Easy peasy. I owe you big time, Gabe!

----------


Starting these types of projects, I start to remember certain things. Things like……


I dislike gluing up large stock and….

....I hate yellow glue ( but I'm also leary about using hide glue in this warm and humid Hawaiian enviroment).

The prospect of gluing up the various sizes required for this project was probably the single greatest obstacle to me not building this thing sooner.


I love working with different species of wood, especially when they agree with my kanna.

Most of this fuigo will be constructed of your basic western red Cedar, but when I didn't find any 20mm thick stock hidden in my lumber stash/treasure hoard (and felt too lazy to head over to the lumber yard), I decided to use this mystery wood. Harder than cedar, I suspect it's some species of mahogany. I've got a fair bit Honduran mahogany buried in my lumber pile, but this isn't it. Spanish cedar? Toon? Nope, not Toon (Australian cedar). Whatever it is, it's got a nice reddish hue and it works nicely with my edged tools, not something that I can say about the many varieties of eucalyptus we have here in Hawaii.

Doesn't matter what kind of wood it is, pig loves to dig in and take a nap.

The list of stock thicknesses for this project are various : 9mm, 18mm, 20mm and 25mm. Convert these measures into the old-school Japanese shakkanhō (尺貫法, "shaku–kan system") measurement units of bu (3.03mm=1bu), and you've got some readily available stock that conveniently matches your chisels…..at least if you are in Japan, haha. I'm making due with what's more commonly found in his part of the globe.


There is one final hurdle for me, concerning this build. If Gabe went through all the effort of making detailed measurements of an honest-to-god Japanese fuigo, it would only be fitting that I should make my reproduction as authentic as possible. I've already fudged some stock thicknesses to what I had on hand, but not by any huge amount, ditto the wood species. My hangup is the nails used to fasten the sides of the fuigo.

These forged nails have a head that is first flattened, then rolled back on itself. Way cool, and there is even a YouTube video showing them being forged.

Forging traditional Japanese nails

This would be another ideal and appropriate little side project…...if I had a fuigo, haha.

Chicken or the egg….chicken or the egg…...

Guesstimating carbon content using the "Spark Test".

I've been using old machinists metal working files for the cutting edges on my laminated blades. Of course this begs the question; What's in this stuff anyway?

It has long been thought that files are made from 1095 (0.95% Carbon) high carbon steel. I really wish that I had some 1095 to compare against, haha! What I DO have is a handful of old files and a grinder (a camera, too), so I'll start with what I've got.




I don't profess any sort of expertise at this, in fact, rather the contrary. Mostly, they just look like sparks, right? I've looked at the stream of sparks shooting aft of the grinder many a time, but this time I figured that if I took some pictures, I might be able to see something interesting. I'm gonna warn you now, this is a very monotonous series of photos that is only going to be of interest to a few people (kind of like the rest of this blog, haha!

It was dark, and I was outside anyways.

The first time I tried the spark test on this Heller file, I knew that I had better start paying close attention. This is an old 8" file, of unknown age. It was old, rusty and dull when I got it, so I can't attest to its value as a file or how hard it is.

Usually the sparks that get thrown off of high carbon steel look like long, red streamers. This file was different.

These sparks are short, red, frilly little things. Also, extremely numerous and active. Notice the many forks and branches, ending with the smallest of explosions. It's like the 4th of July!


The cameras exposure time means that these photos make it look like there are more sparks than you would see in real life. That is one thing that was always throwing me off  when comparing my results to what I was finding online. An actual volume of 2/3 to 1/2 might be more accurate.

These sparks feel soft, delicate, fuzzy.



Next is an old 12" Heller. Again, old, rusty, and dull.

I have read that sometimes the carbon content might be slightly lower in a large file like this one, but that doesn't appear to be the case here.

In real life at least, these sparks look the same (to my eye, that is).

This picture is more accurate in terms of the volume of sparks that I was seeing.

Volume, length, color and intensity, all are indicative. If you apply more pressure to the grinder, you get a longer spark trail and maybe a more fully developed spark, but then it gets hard for me to take the picture, so....

Now for something that I am more familiar with, a Nicholson 4-in-hand file. I've bought a bunch of these in the past and have never been particularly thrilled with their longevity. There they are handy to keep in the toolbox though.

A very different spark here. 

A more intense yellow, a longer stream, and not as much "activity". Fewer sparks, but what is there looks to be intense. Many of the tracers end with a little burst and a branching fork.

Notice how the sparks are bouncing off the tin wall? The spark stream is nearly 4x longer than the Heller files showed.

These sparks feel harsh, coarse.

Now.

I am probably guilty of promoting the same information, right or wrong, as everything that I've found written on the net, but again, we work with the tools we have. 

It has been said that in the old days, Nicholson files were made from a special type of C1095 high carbon steel that had1.22%(+/-) carbon, but since the '80's have been made from plain 'ol 1095. I've seen a number of old technical reference books online that list files as having a carbon content of anywhere from 1.20%-1.50%, and made from the same type of steel that taps and dies are made from. Just the other day I was reading a technical paper that specified using Vallorbe (Swiss) files, made with a 1.22% carbon steel.

I can say with absolutely NO certainty that certain files are made using a particular type of steel. What I am comfortable stating, is that the spark pattern from these Nicholson files is significantly different from the spark pattern from these old Heller files. I would also say that these particular files are NOT overwhelmingly hard.

How about an old Simmons "Red tang"?

This is my current favorite, and an absolute brute when it comes to chewing through metal. It's age is anyone's guess, and it's still sharp, though certainly not anywhere close to being new.

The sparks are starting to look familiar now.

They look nearly identical to those of the Heller files.

Another Simmons Red tang, this time a triangular tapered saw file.

Same (or near enough).

Now for something interesting.....

This rasp sprays a very impressive stream of yellow/red sparks, but there is almost no branching, explosions dots or dashes. It shows just a stream of large tracers that only fork at the ends (if at all).

This is one of those cheap China files that are pitifully soft, and absolutely worthless at removing metal.

The length of the stream is telling as well. See how the sparks are rebounding off of the back wall?

All right, I am beginning to associate long, intense, yellow/red, boring looking sparks with really crappy files. I have a few of these (I know a bargain when I see it!), and they all behave in a similar fashion. In my entire stash of miscellaneous metal, the only thing that I've found that compares to this spark pattern is some dead soft, iron tie wire used for wrapping rebar bundles (a great source for free 1/4" iron, BTW, and easy as hell to straighten!).

I think that this may be a case of.... Case hardened steel.

How about another cheap China file? 

Here is one of those super hard, little detail files that I bought at Wal-Mart, and am always raving about.

Short-ish red sparks, very active, with a multitude of branching, forks, and explosions.

Last one (for now)....

An "Oregon" brand chainaw file.

Can anyone else see the similarity here, or is it just me, haha!

Interestingly enough, the "Oregon" files are made in Switzerland....

.... By Vallorbe.

Using the "Point of a sword" knife

Yesterday was just one of those days.....

I seem to be direly lacking in practice, woodworking wise. Things seem to be going quite well and I'm in the groove, but then you offer up the piece at the final fitting...... Too short! Cut a new one....... Even better, but again, too short! It's not quite the old joke "I cut it, and I cut it, but it's still too short!", but it feels pretty damn close.

Working larger pieces (in this case I'm rebuilding our back deck) while trying to maintain close tolerances, is an art unto it's own. I guess that there are two approaches that could be taken.

You can:

1. Cut every piece flat, straight, and true. Every piece is reduced to a common dimension. 
2. " Cut to fit ". Each piece is an entity and construction proceeds in a linear fashion. Fit each piece to the previous one.

I love and admire " Flat, straight, and true ", but this way of building just doesn't work for ME. This is like my imagined ideal. Layout is perfect and exact, joints are simple(er) to cut, and things come out as planned. For this to work, all components must be oversize, to end at the desired dimension, so there often must be huge amounts of waste. It's also a lot of work reducing the stock, so power tools are most often used. This is " Set it and forget it ".

" Cut to fit " is my reality. Each piece is different and must be sculpted to fit the way that you want it. NOTHING is flat, straight or true, so scribing (as opposed to measuring) is the rule. This can work well, but you need the proper mindset. A minimum of material is wasted, but you get tired of walking back and forth, and few corners can be cut. Trying to save time often results in errors further down the road.

I try for a hybrid approach. For small stuff like a cabinet, this works well. You make the case perfectly, then scribe fit it for installation. For bigger stuff it gets more difficult. Boats are all scribe work, while houses are somewhere in the middle. Our house would list heavily towards the scribe end of things.

We are taught to think in terms of "Flat, straight, and true" (FST), and when things don't work out as planned, we get frustrated and confused. When you do enough if this work (say carpentry) you learn a multitude of little tricks that help you accommodate the inevitable inconsistencies. You assume FST, then work the reality. This works great for machines, OK for groups of people, but makes me (the individual) a bit nuts.

It is a mindset thing. I measure, then cut, always anticipating the next step. My mind is centered on a whole, looking at the goal as a finished project, in this case a deck. My attention and energies are diffuse and thinly spread, because I only have so much to invest at any given time. The usual outcome is a finished product that looks acceptable, and a perfect job is one that gets comments like "And you made that by hand? Really?!! It's as good as that one I saw at the store!". My problem is that I am concentrating on being "done", and therefore not fully present. This makes me feel tired. Big projects get delayed, because you are already anticipating how much work something will be, and how tired you will be when it is finished.

Yesterday's work was me falling into the hybrid FST trap. I cut things close, leaving a margin for adjustment, and thinking ahead. Thinking efficiently. Measure, cut, fit, and finish. Offer it up, often in pairs. A very minor thing (like refining a joint to a hair thin line), can cause two pieces to be essentially too short. Because you ALWAYS start with the longest piece, you can reuse the miscut pieces somewhere else, at least. My time (and the energy invested) are gone, but at least I get more practice this way.

If I look at each step as an individual project, I find that I do dramatically better work. I GAIN energy as the project progresses, rather than feel relief at being finished. This change in mindset is such a simple thing, and it alters EVERYTHING. Instead of thinking about the most efficient way of doing something, I try to do this ONE thing well. My tools have never been sharper, and my cuts have never been straighter.

That said.........



The "Point of a sword" knife has leaped up into my top 10 list of "Tools that I didn't know that I needed ". When "Good enough" isn't, and my joints need a little bit of finessing.....it's a little bit like an eraser for wood.

Separate the joint, only enough for access. I can use it one handed, but it's big enough to use with two.

Combined with my favorite kerfing saw.

Best friends forever!


The knife excels at endgrain. The knife coming to a point means that it cuts with a shearing action. The point can access tight areas like corners.

I formed the point on this knife at a 90° angled tip, but a lower angle would be useful for detailed work. I plan on making another style that has a "sharper" point, and has beveled sides like a dovetail chisel (shinogi-nomi)


Here's an easy one. The tongue on this finger joint is crowned slightly (probably from "crowding" the saw and driving it to hard).

Not perfect, but better. If each thing is better than before, after a while they get pretty darn good.



I thought that this knife would maybe be as useful as a paring chisel, but really more of a curiosity. Interesting.........but how often will you really use it, you know? To the contrary, I am finding it to be one of my most used tools. Two handed, you can take very thin,  controlled, shearing cuts. One hand is fixed and provides the anchor/pivot point, while the other gives drive. Or, you can just stab it at the area that needs adjusting, and the wood curls out of the way. The knife cuts with a unique plunge cutting action that is unlike any other tool that I have. A joinery shiv, haha!

The pointed shape of the tip seems to provide balance to the cut, and the flat back helps to keep the cut planar. There is occasionally a tendency for the blade to dive, so perhaps an ultra-flat back isn't necessary. I'm not sure, and am withholding judgment.

This knife was forged from a small piece of old Nicholson file (O-F) steel, forge welded to a larger piece of mild steel (something that my daughter and I dug out of the muck at the marina). Clay slip, water quench,  3 temper cycles at 325°F for 1 hour. The O-F steel is proving very interesting. Very easy to sharpen, it feels very different on the stones than even, say, YSS white steel #2 (a simple 1.00%-1.20% high carbon steel). It sharpens like a soft chisel, but has shown no edge degradation and hasn't needed honing yet, after 4 days of fiddling with Port Orford cedar. Now that I think of it, when sharpening, it feels similar to how carbide sharpened with diamond feels. Carbide is VERY easy to sharpen, if you use diamond.

The knife cuts lightly, but feels toothy somehow (even though I polished the edge using my finest stones), and the edge LOOKS great under the microscope. Weird. I'm curious to see how the edge chips (as it inevitably will).

There is a guy named Murray Carter that makes Japanese style knives professionally. He has an edge sharpness test that he calls the "3 finger" test. Maybe it's 4 fingers, I can't remember, but the gist of it, is that if you touch the edge of a knife using 3 or 4 fingers simultaneously, and your hair kind of stands up in alarm...... That's sharp. It sounds goofy, but it does kind of work and it certainly is an interesting metric. This knife still feels that way, after 4 days of use. I wonder how hard it is? I would guess around Rc60-62, but people terms to overshoot their numbers, so.... It is harder than my hardest file, anyways. What I REALLY want to know is how TOUGH it is.





These are from the tool kit of a Japanese pro.

I wonder why he has 4 sizes? The second from the left (24mm?) looks like it sees a bit more use.


Eye aspire.

Clean. Nice. Candy.

After quench straightening -and- Connecting the dots

So it's time for the final quench, the action that determines the ultimate usefulness of an edged tool. This is where the steel becomes hard. Or shatters. That can happen, too (but usually doesn't..... Yet another wonderful aspect of laminated blades).


In preparation for the quenching process, I coat the entire blade in a very thin coat of mud (more of a wash, really). The reason that this is done is twofold. The clay covers and protects the steel, isolating it from the oxidizing environment of the forge, which can strip carbon from the steel, reducing its ultimate hardness.

When you plunge a red hot piece of steel into water, vapor is formed at the steel/water interface. The water vapor actual isolates the steel to a certain degree, lengthening the amount of time required to cool the steel. We are talking fractions of a second here but, for this stuff, time is of the essence.

The ultra-high carbon steels used for this style of construction require an extremely fast quench time to achieve maximum hardness. The clay wash acts to disturb the formation of the vapor jacket, making for the quickest cooling time possible. So again, clay makes for a harder blade.

I just love imagining how these traditional techniques must have evolved. You are a blacksmith. If you leave metal in the forge for too long, it will burn (oxidize), so you want to put something on the metal to protect it from the harsh flame. Everyone knows that clay soothes burns. And hey! The blade gets harder too! Let's keep doing this!

A charcoal fire provides a gentle heat that minimizes the possibility overheating and oxidation. When you combine the charcoal heat with a clay coating, a distinctive oxide skin is formed on the metal, giving it a soft appearance, something like finely brushed velvet. While not extremely durable, the oxide coating does protect the metal to a degree, and looks WAY nicer than paint, haha!

Quality tool makers like the charcoal oxide, because it displays, to a knowledgeable person, that the tool was made with care. I knew that a charcoal skin (as it's called) was a desirable trait. All of the really nice (expensive!) tools seem to feature it as a selling point, and now I know why. Now I need to figure out how to actually DO it. There is little information that I can find. Water, natural sharpening stone residue, and a bit of charcoal dust..... That's all that I've found, so far. I need to experiment. More charcoal? Add iron oxide powder to the mix? Any ideas?



There are many western blade makers that use clay coatings on a blade to induce the formation of a "hamon". This is the stereotypical smoky wave shape that you see on samurai swords. In hamon formation, you are using a thicker clay coat to dramatically alter the quench speed on different portions of the blade.

If you are making a sword, you want a rock hard edge capable of great sharpness. If the entire sword were that hard, it would shatter in use, so you need the core and spine of the blade to be softer. This gives strength and durability. The hamon is a manifestation of steel transformation. It is considered beautiful in its own right, but loses its relevance when used indiscriminately. Form should not supersede function.

This is a form of differential hardening. This isn't what I am doing. I am using the clay to make a harder blade, not soften it. All of this is fascinating........Earth, iron, and water. Elemental.




Before I perform the quench, I want to refine the grain of the steel, to get it as fine as possible. The way that this is done in the modern bladesmith protocol is to perform a process called normalization. To normalize the steel is to homogenize the grain structure as much as possible, while concurrently reducing the overall grain size.

I normalize in three stages. I heat the blade in the forge to an even bright orange heat, then remove the blade and let it air cool. This is pretty hot, which makes for a large grain size, but at least they are ALL large. I do this a second time, but this time, I only bring the blade to a bright red, then let it cool. Finally, a third time at a dull red, just above the point where the steel become non-magnetic. In theory, this will give the steel an optimal (small) grain size.

Japanese blacksmith's don't do this normalization process, as far as I know. If you do stuff like this day in and day out, over multiple generations, any process will go through an outcome driven evolution. Good ideas gets preserved while the bad idea get discarded. I am certain that there are hundreds of minute details inherent in the traditional forging process that make normalization unnecessary or irrelevant in this case, but because I am working in isolation (and a total beginner), I just use my best judgment. This three stage normalization shouldn't hurt, and might actual help a novice make a successful blade. It seems like a good idea, right?


OK, NOW it's time for the final quench. Fingers are crossed.....

Seems OK.

Things happen swiftly at this point, so photos are lacking.


Before the quench, I had bent the blade opposite to the expected direction of distortion. A laminated blade will tend to warp towards the steel side (EDIT!! See below, my bad.....) so I induced about 1/8" over a 5" length.

This was too much.

I saw very little distortion at all, but surely there was some. Within the 1/32" to 1/16" range? When I quenched the blade, I plunged the blade into the water vertically for a 3 second count (the steel used requires less than 1 second to harden), then pulled it from the water. The moisture immediately evaporates, then I dip it back into the water very quickly, splash, splash. I hope that this interrupted quench will help keep the blade from tearing itself apart. The stresses imposed on the blade during this process are varied and immense.

***********EDIT!!!***********

 I've got this one completely wrong! The blade warps towards the iron side! High carbon steel expansion locked into a physically larger structure, so I need to counter bend to the high carbon side. There is a problem with this, however......

Sometimes the blade doesn't warp! This is one of those details/experience/luck kind of things. Temperature of the metal at quench, temperature of the quenching media (ei: water), grain structure of the steel compared to the grain of the iron, all of these components will effect the final outcome.

As an example.....

I made a blade the other day, but the weld was a partial fail. Perfect for some destructive testing! First, though, I want to practice my quench technique. I am currently doing an interrupted, 1-2-3 in (until the red disappears), then removing the blade hot from the water. Water is at ambient (60° F), thin clay slip coating. Charcoal fire, bringing to barely above nonmagnetic.

First quench warped badly towards the iron side centered at the bad weld location. The weld had sheared, allowing the different metals to move independently, producing a larger than normal warp. I hammered the blade flat, using a log as an anvil, but otherwise took no particular care.

Next, I practiced some grain refinement/normalizing, by bringing the blade to a high heat, a bright red/low orange, then out to cool to a black heat. Repeat, but only to a medium/bright red, then again to a red...... You get the picture.

This time, there was no warpage at all. I cut through the iron of the blade, right at the failed weld, then broke the blade in the vise. The grain of the steel was very fine (this stuff just amazes me! Metal crystals!), as hoped. I pried the iron away from the steel, to test the peel strength and find the extent of the bad weld, the cut the blade fully through, leaving a presumably good blade, 4" long.

I next brought the blade to a full red, then cooled to black, thinking to relieve some of the stress that I had imposed on the blade. Three perfect quenches, with little to no warpage, resulted.

I brought the blade to a bright red, then quenched. This resulted in a substantial warp to the iron side. Interesting! I hammered the blade flat. By this time there are a few areas where the hard steel laminate has shattered, so that's about it. Exposed steel grain is predictably large.

Final treatment was two reducing heats to bring the grain size down, then quench at barely magnetic. The blade was then broken, to reveal good weld adhesion and a fine grain structure of the steel. Fun stuff....... Poor little knife :-(

OK, boring to read, but really fun to actually perform. Short form is that a series of reducing heats may serve to refine steel grain size to a minimum, and may reduce the likelihood of post quench warpage. In addition, tempering releases some of the tensions induced during the quenching process, and may reduce some of the warpage. I may wait until after tempering, then straighten a blade.


This brings me to my second warpage point.

A warp to the iron side is easy to correct, because the soft iron will stretch, to accommodate the iron.  This process is essentially a stress relief. A warp to the steel side is hard to correct, and possibly fatal to the knife. To correct this condition puts the steel in tension, and requires the iron to compress. This is not likely.


***********End edit************
While the blade is still warm, I sight along the length to determine the degree of warpage. Little to none..... Hmmm.

I haven't done this enough to determine the reason for the lack of distortion, but it may have something to do with the normalizing procedure. There are so many factors to consider. In any event, I grab my instruments of torture, and start tapping, then banging. This is tough stuff!

I use a hardwood block and cedar shims to cushion the blade and to minimize the amount of scarring. I would like to preserve the forge black oxide finish as much as possible.

A few strikes get me to this point, where the 5" length of the blade is fairly flat.

The blade (at the very tip) is still high.

A little rubbing on a (flat!) sharpening stone reveal the highs and lows.

I do what I can, using a soft mallet on this difficult and vulnerable location. This helps a bit, but this is too general an application of force.

 I need more precision. Ura-dashi!

My lead-filled tin-can anvil is nice for this. It absorbs some force, making the hammer blows less effective, but it also cushions the blade nicely.

The very tip is still not there yet. The shape of the urasuki is...... Not nice.

I need to think on this a while.



The charcoal skin is interesting (and hard for me to photograph).

The upper surface was left rough, so there is a strong surface profile, lots of texture.

The adhesion of the clay seems to have been inconsistent. This is particularly evident on the finely file finished fundament (Say that 10x fast!).

Here you can see the area of the handle to the left where the oxide coating looks good (except where the clay was scarred by my careless tonging). The middle area is spotty. This was the quench depth, as my water bucket is not deep enough. Some of the clay was applied when the metal was already hot, and flash dried. That probably contributed to the inconsistent adhesion.

This also needs work, and will take a bit of experimentation. As I said, information is scarce, so any additional information would be very welcome! I suspect that the real blacksmiths use a chemical treatment of some sort, to enhance the oxide formation. I also might be missing a key component in the clay wash...... I use a residue from natural sharpening stones, but different types of stone would show different chemical compositions.




I go back to watch my favorite chisel blacksmith at work.......

https://www.youtube.com/watch?v=1Ij9z9J6T1c&app=desktop

The process of quenching is called yaki-ire. Before this, the blacksmith shows how he carefully coats the chisel with an even thickness of thin mud, using an old toothbrush. The mud is in a clay pot, which he gently stirs, before applying a smooth coat of even thickness.

There are two pots, implying two different mixtures. The mixes look very similar, so I am guessing that one pot holds the thin clay wash. The second pot must be thicker (maybe that's my problem?), and this is the stuff that goes on the top surface of the chisel.

He dries the clay, using gentle heat from the forge. For yaki-ire, he uses a charcoal forge. He heats the chisel to what LOOKS like a bright red (but is probably not that bright in real life, bright red is awfully hot!), but then quickly tests the heat of the chisel, using a magnet to confirm that he has reached the Curie temperature, and the metal has become paramagnetic. This is important.

I am inferring a lot. He tests the chisel very quickly, then plunges it straight into the water quench tub. He does this pretty fast, and doesn't make eye contact with the interviewer, implying that this is not just for show, that this is how he normally does things, and that being VERY close to nonmagnetic is important.

If I understand things properly, to achieve maximum hardness (with minimal grain growth), you want to quench these ultra-high carbon steels at (+/-)100° over the nonmagnetic transformation. This guy sweats the details.





The other night, as I was watching the chisel blacksmith video, I connected the dots. Yamazaki-san, the chisel blacksmith, is  Yamazaki Shouzou....... Hidari Ichihiro, the most highly regarded tool blacksmith of the modern day. Others are compared to him, as in "He's as good as Ichihiro!". He has become a benchmark. The film was made in 2001. Yamazaki-san died in 2007.