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Cracked! 1075 Ko-Wakizashi fail!


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I heard the dreaded *tink..tink....tink TINK!!!!!*, and then my neighbors heard the F YOU's....this evening. Couldn't help being upset, it was my first cracked blade.

 

What we have here is a 1075 Ko-Waki, that I was rather proud of. Even had images posted elsewhere before this even occurred. Was confident with yaki-ire. I got off early today, had an ice cold pepsi, and my neighbors were watching with a camera rolling. What could go wrong? Pfft. Everything that's what!

 

I did learn a few things. Firstly, I need to practice applying clay very evenly. The blade took a slight curve to the right. This in my opinion was due to an improper normalizing cycle, or too thick of clay on one side. Granted this was my first time working 1075, and quenching it in 110F straight water at that. I have had much success with hamon production in the past with W1.

 

I also either need to modify or build a new forge for these longer blades. Currently do everything from a bottom blast coal forge. Has always treated me well in the past, but getting the entire blade evenly to critical was a PITA. Worked just fine and dandy doing 4 normalizing cycles. Decided to give me the middle finger when I needed it to work the same this evening though.

 

Not to mention I need to just spend a little bit of time and forge some box jaw tongs for tangs. My current tongs I use grab the tang from the sides, and with the tang of japanese blades having two different planes, it doesnt hold it too well as I need it edge end down. Just seemed to be too loose for control.

 

Also, I realized a little while ago that I had my grind marks are perpendicular to the edge. Not sure how I missed that before I started yaki-ire.

 

EDIT: Also I did a quick etch with Ferric to see where the hamon went, and it appears as in the photo that it was closer to the edge than it needed to be. Isn't this indicative of slightly too hot?

 

RE-EDIT: On the bright side, it took on nearly 1cm of sori!

 

RE-RE-EDIT: Please excuse my candidness. Been pretty hot over it this evening. Still in the fallout.

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Edited by Daniel Cauble
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I agree that you probably need a forge design that will allow you to heat the entire blade evenly to avoid uneven heating. I designed my forge based on Jim Hrirsoulas design in his book The complete bladesmith. Which allows me to normalize and heat treat any size blade up to 48" Also, water quench of 1075 or similar spring steel is less forgiving than oil quenching.

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I feel your pain, I just went through this with a tanto out of 1095. It was mainly due to no normalization and being too hot. I now quench in 130* brine for four seconds and switch to 140* sunflower oil and keep my temps at or just under critical. What I and other smiths have noticed is that Japanese sword smiths keep the spine cooler than the edge during quench, it's hard to do but I think it yields a higher success rate and gives the blade a softer spine.

 

 

I followed everything I was told and my last tanto survived two quenches( had to fix the hamon) and I even left the edge around .020 thick. Just made sure all the edges were uniform and rounded.

Edited by Silent Matt
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I've never done a Japanese blade before, but I noticed a few things on your blade that would be too risky in my book. Some of my precautions are: make sure everything is rounded, especially the edge, keep the spine cooler then the edge, never quench in tap/city/well/spring/creek water, and don't leave the blade in the quench any longer than you have to. Hope this advise can help you in the future.

By the way, I feel your pain too, I've cracked blades before as well, and it sucks, but that's one of the things we've got to deal with.

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Ah well it's annoying, but it happens to everyone! Rounding off as above helps as well as careful monitoring of the temp, even and just above critical, time for the next one!

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I'm with Gabin Haraldr Piedbois, the last picture shows a change in the edge right where your crack is. I've had a blade where a small grinder slip ment there was a 1 cm narrow spot and thats exactly where it broke.

 

It sucks but we normally learn the most when something breaks

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The one thing that really jumps out to me is the Rough sanding marks on the blade and all the sharp edges(not rounded) and the thin coat of clay you applied all could be the reason/factor that the blade cracked . you are not the first one to crack a blade Nor will you be the last .

 

Brother you just have to learn from it and Drive on ! Not being harsh it is what all smiths will, have and do when we make knives if you give up you will never know the joy of completing this type of project .

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Daniel,

 

Wow, I can empathize with you that moment...I am vey grateful you posted this, as I am about to do the very same thing later today or tonight when it is dark I hope I can remember the color of the rising sun.

The list of suggestions given by the replies you received is very helpful and will be put to good use.

 

Jan

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Now that Michael mentions it, the crack does seem to originate at a thicker part on the edge. I don't know if that created enough thermal mass to prevent that small section from converting to martensite or not but it is a possibility. It could have caused that section of the blade not to expand as much as the surrounding martensite. Make sure that you have everything even with gradual transitions. Even then there will be times when the forge gremlins strike from nowhere.

 

Doug

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Thanks for all the feedback guys. I am currently taking everything into consideration. Woke up this morning and went straight out to the forge, and started again. This is where I am at so far...

 

Waki.jpg

Waki2.jpg

Waki3.jpg

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I forged the bevels in, then belt sanded further, and am now down to draw-filing the rest to get lines even as possible. I am going to round off edges as suggested. Not sure what to do about the light wash of clay. I started doing it with W1 due to several sources suggesting it helps the blade survive during quench. Will also do this next heat treat at night instead of during the day, probably another hidden misstep.

 

Going to also make some tongs that will hold it firmly before yaki-ire. I think I may be able to heat it evenly with current forge if I had proper grip.

 

Also, this new one is 18" total. 14.5" from mune-machi to kissaki. Might shorten that a little bit to give a little more nakago.

 

EDIT: Good luck Jan!

Edited by Daniel Cauble
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The thin coat of clay can't be bad, if i'm not mistaken (just got out of bed ), in the case of a water quench, it helps the bubbles flowing around the blade and not sticking to it thus evening the hardening :)
and in either case, it protect the steel from oxidizing :)

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Yup, Yup. Btw guys this is Aldo's low manganese 1075. .25x1.25" stock. I have enough for one more if this one fails. I may forge another out for the sake of having another. A ton of fun forging these out. Really trying to get the Boshi just right. I swear, forging this last one out, I almost went all out and made a Katana. Held back however. Baby steps, hehe.

 

I have made sure this thing is straight as possible. No twisting or bending in it. I use a section of RR track for a straight surface. My 371# Peter Wright has a little sway in it, and I use that as a counter for the harder bends. Now sometime this week I will throw it in for some normalizing cycles, then the clay coat, and then...we'll see?

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Just working out the kissaki and the rest of the bevels before normalizing cycles and claying. I also tapered the blade slightly from ha-machi to the kissaki. The edge is over 2mm thick, so no worries.

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Edited by Daniel Cauble
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