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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #1  
Old 08-23-2006, 03:34 AM
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Andrew Garrett Andrew Garrett is offline
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Hamon styles

In looking at a Hanwei tanto recently, I noticed a significant difference in the look of a Japanese hamon and one commonly found on custom knives.

A japanese hamon is almost always (in my experience--always) frosty all the way to the edge, such as this katana:


My knives as well as all others I've seen herein never have that Japanese style hamon. Rather, They have a frosty line, like my EDC here:


In further study, I found out that Hanwei and other Japanese style sword and blade makers, cover the entire blade with clay instead of just the spine. The edge gets a thin coat while the spine gets a heavy dose. The thin clay on the edge allows the steel to harden during the quench, but makes the whole region frosty after an etch and polish.

My question is this: Which steels could be hardened this way? It seems that a barrier of clay, even a thin one, would prevent the steel from becoming as hard as it could be. I also might point out that no mention of tempering after the covered quench was made. Does this type of clay quenching mean that they can forgo the tempering since the blade was maybe just quenched to final hardness?

Explainations are welcome. Thanks.


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  #2  
Old 08-23-2006, 03:49 AM
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AUBE AUBE is offline
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[QUOTE=Andrew Garrett


Explainations are welcome. Thanks.[/QUOTE]

how about guessplanations?

im thinking the frosty look is due to how they finish the knives and not necessarily heat treating. ive noticed some of my japanese sword suppliers sell chemicals to "bring out the color" in the blade...this may help bring out that frosted look. i have done the fully clay coated blade thing and my edge still didnt look any more frosted than it normally would (perhaps i did the wrong thickness?) it is my understanding that they apply the thin coating on the front of the blade to control curvature and prevent cracking. ive read they still temper after quench.

its completely possible im 100% wrong on this.
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Old 08-23-2006, 07:19 AM
EdStreet EdStreet is offline
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from all my research into togi the answer to this is in the polishing method. Not many custom knives have I seen with a traditional polish out there. This seems to be a very deficent area.

There's several stones and some liquid that will give the results you want. Careful tho that line of polishing is not easy to do and very easy to botch. So far from all the stuff I have been looking at there's only ONE way to get that look and it does not involve torches, acid and sandpaper, it's stone and the powder stuff.

Ed


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Old 08-23-2006, 09:23 AM
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Andrew Garrett Andrew Garrett is offline
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I appreciate those responses, but I'm not convinced that's it.

Reason: The Hanwei Practical swords and other combat quality blades from similar makers are mass produced to a degree. The costs are kept to a minimum by eliminating such things as hundred of hours of folding steel and handpolishing with stones.

I am convinced that the hamon is produced the same way one of mine is. Follow me here: When I apply clay (satanite), it is thinnest at the edge of the clay. It is exactly at this thin edge where the frosty line appears later. I THINK the exact same process happens on the Japanese blades with one difference. The thin clay at the edge of the thicker stuff is extended to cover the blade down to the cutting edge making that whole area frosty. So, where mine has three distinct areas of hardness (the soft back which polishes, the frosty, hard-to-some-degree line area which does not polish as easily, and the hardened area which also polishes), while the Japanese blade has only two areas of differential hardness (the soft back which polishes and the frosty hard-to-some-degree area which does not).

Please continue to debate me here, because I'd love to understand this better. I just don't buy the mysterious stone polish thing because in essense, it's not any different scientifically than hand rubbing a blade with a very fine grit paper (which does not produce this finish). And the point is mute anyway if I am correct in that these $400 combat quality katanas are not polished by hand.

As always I could be very wrong! I think some testing is in order here. I guess I have to go back to the original question too: Is this or can this be achieved by quenching a covered blade to final hardness without tempering? Would a sword perhaps benefit in the area of flexibilty this way?

Thanks for the input fellas.


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Old 08-23-2006, 10:04 AM
Joe Walters Joe Walters is offline
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Please continue to debate me here, because I'd love to understand this better. I just don't buy the mysterious stone polish thing because in essense, it's not any different scientifically than hand rubbing a blade with a very fine grit paper (which does not produce this finish). And the point is mute anyway if I am correct in that these $400 combat quality katanas are not polished by hand.

It's just a surface effect brought out by different finishing stones. Some of the contrast has to do with the steel itself, but the frosty look is only due to the stones. It is an entirely different process to use sandpaper, as these abrasives work very differently on the steel. You can get that frosty look by using different finishing compounds after you etch, rubbing out the jigane area with an aggressive compound (flitz) and the hamon/habuchi with cerium oxide or a finer agent.

Edges on Japanese blades can be very hard, all the way from the habuchi line down to the cutting edge. Many were not tempered after hardening. All blades, fully hardened or not, should be tempered. It will have little effect on the finished look of the piece.

Get some hazuya and jizuya stones for finishing out some blades if you want to learn about the differences in sandpaper vs. finishing stones. On modern monosteel blades, they are not always the best finish to show off the activites. Dilute nitric acid makes a very good etchant for getting that frosty look.

One more thing: that frosted look has an incredible amount to do with the lighting on the piece as well. Put a black reflection on your blade and a bright light at a 45 degree angle running lengthwise down the blade, and you'll see the same thing. Traditional polishes look very different depending on how the blade is oriented to the light. It's not supposed to be a jazzed-up attention drawer; rather it's more of a subtle balance and 'window into the steel.'

Last edited by Joe Walters; 08-23-2006 at 10:09 AM.
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  #6  
Old 08-23-2006, 11:10 AM
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AUBE AUBE is offline
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i should have worded my original repsonse better...

i think the potential for the frosted look is put there during heat treat...but only becomes apparent with the proper finishing.

for example i do a lot of differential heat treating on my knives lately and many of them i sell as affordable using knives. since they are geared towards being affordable and a user knife (that will get scratched up from use) i limit how much time i put into the finish. most of the time i only handsand to 500 grit then do a deep acid etch. using this method it will only show off the main hamon line and no activity. for example the following pic;



if i were to take that same blade and use a much more dilute acid blend and sand to a much finer grit it will show off lots of activity. the same thing applies in reverse if i were to take a blade such as the following fikes/fogg one that has some beautiful frosty looking activity and use my quickly applied user finish it wouldnt look nearly so good...it would just outline the basic shapes and have none of that cloud look to it. (btw i love that blade of theirs)



ive never used stones for finishing so i have no idea how different of a finish they would give than sandpaper (iwould have assumed the same looking finish if using the same grit)

as for all the time it takes hand polishing...depending on who they have do the polishing and what area they live in, it may be possible to sell a sword with a nice finish in the $400 range. if all work is done in japan from my understanding of it the cost would be too high to sell for $400....but if they had handwork done somewhere like china, philippines etc its possible. one of my filipina friends works 12-15 hour days...she brings home about $4 a day. a family i sponsor through childrens christian fund brings in about $30/month(to support 7 people). pay someone $100/month from the right region and they could do quite a bit of polishing for you and be happy to have the work.

Last edited by AUBE; 08-23-2006 at 04:20 PM.
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Old 08-23-2006, 04:27 PM
EdStreet EdStreet is offline
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are you refering to a frosty look like this?





This is a tanto, gunome midare hamon, 9 inch Nagasa, 1095 steel, clay coated and water quenched by Jesus Hernandez. This is something im working with currently and it's far from complete. in the sandpaper world you could say this is 400 grit sandpaper. As for lighting goes you can see this very same look in just about any lighting unless it's super harsh.

I did NOT use acid on this one at all for this look. As someone else stated those 2 stones for the final polish is the ticket, also the paste is essential for that look.

quite frankly this tanto is just starting to have the hamon developed by polishing, in the end it will be alot brighter and bolder than here.

With stone polishing (can be automated btw) it's no magic or miracle to it. plain and simple it's mud, compressed mud from animal skeletons from a very long time ago. they essentialy 'stain' the metal as they are polished. it developes with the grain of the metal and differences in the metal stick out differently with each stone.

Quote:
A sashikomi nugui finish will selectively lighten the hamon, but only inside the nioi line (hamon boundary) and effectively reduce the area of the white hamon to produce a more pleasing appearance on the sword. this type of finish will also lighten or emphasize only the area inside the hamon and not affect the ji

magnetite (jitekko), clove oil and cotton wool (cotton ball). add finely ground magnetite powder to clove oil to form the mix. it is not necessary to filter thru yoshino paper.
jizuya then hadori (modified) then add boiling water to the blade and immediately use sashikomi nugui. put the paste directly on sword with your fingers over a 3 inch section then rub it over the ji with the cotton wool. sashikomi is applied over the entire blade (including the hamon) except for the kussaki. the ji WILL darken but the ha will remain the same. sashikomi nugui should NOT be used on swords with a rough jigane (core exposed in the ji) or with a surface with nicks, gouges or depressions, it WILL highlight these defects.

FYI magnetite a.k.a. iron oxide. a.k.a. that black gritty stuff you get on the outside of a blade from heat treating that's sanded off.

Like I said there's nothing magical about this nor mystical

Ed


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Old 08-23-2006, 05:43 PM
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Andrew Garrett Andrew Garrett is offline
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Ok. It's starting to slowly sink in. I'm gonna re-read all this a few times today and do a little more reading elsewhere to figure out exactly what is going on.

THanks a ton fellas!

However, I still wonder how hard a blade can get when it's quenched in 100% clay coating?


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Old 08-23-2006, 05:48 PM
EdStreet EdStreet is offline
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from my understanding of all this is chame is used to make the temp even across the blade, not to inhibit heat.

Ed


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Gold is for the mistress - silver for the maid
Copper for the craftsman cunning in his trade.
"Good!" said the Baron, sitting in his hall
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Old 08-23-2006, 11:17 PM
Joe Walters Joe Walters is offline
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However, I still wonder how hard a blade can get when it's quenched in 100% clay coating?

It depends on how thick the clay is and how deep hardening the steel, grain size, quench method/medium, etc. With a thin wash of clay, you could still fully harden the blade.
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