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Yanagi forging...


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Tomorrow I need to forge a commissioned yanagi. It will be wrought iron/high carbon.. single bevel edge in the traditional manner. I was just watching Murray Carter's video on this topic which somebody posted in another topic recently:

 

 

So he forges this very close in the video.. and he even forges in the slight concave on the non-beveled side. Is there any benefit to forging in the concave rather than grinding? Or is it just due to the very close forging and is required to not remove too much of the high carbon material??

 

Also.. He spends a lot of time cold working the blade to correct warpage after heat treat. Is there anything at all that folks would recommend to avoid the warpage? i.e. put a little opposite warp in before heat treat so that it warps straight? Or I've heard of folks clamping it to some thicker straight stock. Or is it best to just forge it thin and just work out the warps/twists after heat treat?

 

In short.. any words of advice before I do this thing??

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That's over my pay grade, but it will warp with the high carbon curving towards the wrought. The thing is you won't know by how much, so putting in a counterbend might make things worse if it's not exactly right. If I were going to attempt it I'd do the traditional method, i.e. forge thin and tippy-tap out the warp after HT. Easy for me to say since I'm not attempting it, of course! :lol:

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Scott,

 

The video shows how he does it..the soft iron is cooled just ahead of the high carbon, by quenching at an angle .I have seen some videos where this is done at almost a 45 deg angle. Looking at the video here, I assume it is a right handed knife.

 

On a recent trip to Portland I had a chance to drop by his shop..it is a really clean, well tooled shop..Murray has written a very good book and produced some very good videos..I will be buying one of his knives this holiday season.

Jan

Edited by Jan Ysselstein
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Thanks Jan... Interesting. I will watch that part again. I have a feeling it's just one of those things you have to contend with.. but if I can minimize it then all the better.

 

Here is the forged blade by the way. I did a little clean up grinding of the profile. I may have to do more bevel forging depending on how things look during grinding. I really want to keep the iron as close to the edge as I can.. for once.

 

10620549_747772431930847_660567663445986

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]Scott,

 

I got so inspired by my visit to Murray's shop , I came home and put a motor (3 phase vfd) on this thing (this is an old pic) . I have no camera right now but will post a pic of it in operation. The wheel is rated for 1200 rpm I have had it up to 450 but run it between 200-250 RPM. Right now I am running a diamond point over it to true it..then a pump.

P1010998.jpg

Edited by Jan Ysselstein
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You have no idea how much I'd love something like that. A lot of the things I'm getting into require a bigger wheel than what is offered for the KMG. I have the 15" wheel.. still not big enough. I'm thinking of getting the radius platen the Nathan the Machinist makes.. which is eq. to 30" I think. But need more feedback on its use before I do that...

 

Well my blade warped like crazy of course. :-) I just heat treated it. But it's just a nice big even 'C'... those aren't bad. I had more fear of twisting and nose diving.

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Scott,

 

I have Murray Carter's book and I highly recommend it. He has a full, detailed chapter devoted to straightening. I won't steal his thunder but the hammering you see in the video, post heat treat, is on a wooden stump with a brass hammer. He also uses a magebo-pretty gentle and effective.

http://www.tharwavalleyforge.com/workshop/hints/73-straightening-blades

 

Both methods are for soft/hard laminate blades. I don't think it would work for full hard monosteel blades. He said the vast majority of his straightening is with these two methods.

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Thanks Dan. I guess I should make an actual magebo. I tend to use my vise too much for that application. Although most of my post heat treat correction is done with clamps and shims while tempering. But that takes so long!

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Scott,

I am not sure I am going to love that big thing,now that I am used to 2" belts ( this wheel requires a lot of pressure when using the 8" width). I have converted an old punch press to a grinder...by buying a belt tensioner from Jantz...the abbrasive belt runs on the flat flywheel of the press and the tracking is controlled by the tensioner...a v belt now drives the flywheel. This has a 17" contact wheel ( the flywheel) perfect for the knife you are making..it is my favorite grinder and I use it mostly with water/silicon carbide belts..I am looking at craigslist this week for another one which can be driven with a v belt. I would go this route before chasing a large stone.

 

Jan

Edited by Jan Ysselstein
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Ah too bad Jan. Yeah I guess those big wheels take a lot more time when you are used to a fast, modern grinding machine with ceramic belts! I'd love to see pictures of your apparatus.

 

Well correcting the warp was very easy on this blade. I just used my clamps and shims which is equivalent to a 3-point jig you see people using in vises. I just didn't have the courage to try hammering it yet. And I don't have a brass hammer anyway.

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okay now I'm getting into something I need to understand. Should I be able to get at least full spring hardness (in the iron clad section) with a laminated blade with soft/hard components about equal? This thing was easy to correct because it simply is bendy. The edge is certainly hard .. as tough as I'm able to get 1084. But it takes a set fairly easy. I'm not that concerned as this type of knife has a relatively thick spine and they are not used in a manner in which it would ever bend unless used to pry something. But this is really reminding me of the wrought iron/1095 san mai dao I made. In that case it seemed to be decarburization as I couldn't get the edge to harden.. and I also started with way more wrought iron than high carbon.. and a short fat billet. So lots of forging to shape and lots of opportunity for carbon migration. But in this case I kept the wrought as thin as the core.. and it was only on one side! It is possible that I didn't soak long enough for critical temp to reach the spine I suppose. But what if I did? Should I expect a spring with a blade like this??

Edited by Scott A. Roush
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Scott,

 

Murray mentions the profiles of the pieces welded can be the same size but it seems the thickness appears to be about 1/4" for the high carbon and 5/16 or 3/8 for the soft steel. Many of these blades were straightened using a blunt chisel to distort the softer steel...so there has to be a little extra at the start, if that is your method of straightening ( as the chisel marks get ground off).

 

Did you cold forge it? The dislocations in the softer steel may have left that material stiffer as it's critical temperature was not reached during your heat treatment(maybe not). That would be an easy test to do.

 

By the way I worked on the big grinder by cold forging some soft steel and removing the dents ( kind of a sword like thing) ..I am starting to love it..at the speed I am running the only place the wheel throws water off is where my face is while I am sitting at the wheel ( ha ha).

 

Jan

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Ha... that sounds like my own water cooling apparatus.

 

Sounds like I need to get Murray's book.

 

Another thing.. all the pictures of yanigaba show the shoulders of the tang sticking out just a bit. Were these blades designed to come out of the handle then??

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Scott,

I have seen that handle gap and cannot explain it...the relative stock size info did not come from the book but from the video you have at the top. The book is very good, but as with all the books associated with the traditional Japanese blade smithing/polishing methods, one is required to fill in where specific information is vague ( personally ..I like that type of writing , as it requires greater reader participation).

 

Jan

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I have a hard time following and paying attention to videos. :-) I need to READ.

 

Anyway.. turns out the gap is there because the tang is a pressure fit allowing the chef to remove the blade periodically. Frequent removal/return will loosen up so you have room on the tang to keep tapping it further down. So it starts with a gap...

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Hey Scott. I checked out those radius platens and seriously gave a "WHY DIDNT I THINK OF THAT!?". Solves all problems with not being able to get bigger wheels for my KMG, or needing a ginormous stone wheel. For this particular knife, and sashimi knives, would his 36" radius be the ticket you think? He makes a 3', 4 and 6'.

 

About that, he also just started making a new batch of them so get one while they last till his next batch.

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Scott,

Do you know why the blade needs to be removed from the handle by the user....Yes I would highly recommend you get his book, if you get more from reading than looking. In his book, Murray describes a method of improvising a curved platen ..I saw it in use in his shop and it may work for you as well.

 

I have invited a local Sushi Chef to come to the shop and play with steel and grinders ( he also makes knives ) , I will try to get some of his thoughts on this particular knife style.

 

Jan

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Scott, you are correct on the reason for the gap. If you are using a friction fit, you need the gap. However you can make it flush if you permanently epoxy the blade in the handle. I have heard the reasoning for the ease of removing the handle is that handles wear out much faster than the blade and are thought of as a consumable. That is true for the the simple ho wood handles but a more durable handle will last a long time too.

 

The blade taking a set is the product of the lamination with non hardening steel, you will not get a spring hardness on the mild side of the blade. I believe this is the reason that many Japanese smiths include cold forging. You can straighten twists and bends before and after heat treat with this method. As I am sure you know, fully hardened mono steel blades are a bear to straighten after heat treat and it usually involves doing it at tempering temps with clamps. I pretty much only make kitchen knives and long, thin tapered mono steel invariably warps in some direction. I have recently begun making damascus out of non hardening steels and using it in a san mai configuration with high carbon steel or high carbon damascus in the middle. I am still working it out but I think the hassle of setting up the san mai is a better trade off then trying (often in vein) to straighten mono steel after heat treat. Time will tell....

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Jan I've been thinking about getting some local chefs involved with my stuff as well. I need feedback!

 

JM... thanks for that. I feel like I'm missing something on the hardness of these iron/high carbon san mai blades. I would think that the exposed side of the high carbon would fully harden even though it has low carbon on the other side. Is it just the physical mass of the unhardened counters the hardness of the other side?? I suppose if you had a much higher ratio of the hardenable to the unhardenable then you would get a springy blade? But I can sure see the benefit in styles of kitchen knives that don't require flexing in their normal everyday use to be this way. You are right.. very easy to straighten..and in the yanigaba there is no reason to ever flex them.

Scott, you are correct on the reason for the gap. If you are using a friction fit, you need the gap. However you can make it flush if you permanently epoxy the blade in the handle. I have heard the reasoning for the ease of removing the handle is that handles wear out much faster than the blade and are thought of as a consumable. That is true for the the simple ho wood handles but a more durable handle will last a long time too.

 

The blade taking a set is the product of the lamination with non hardening steel, you will not get a spring hardness on the mild side of the blade. I believe this is the reason that many Japanese smiths include cold forging. You can straighten twists and bends before and after heat treat with this method. As I am sure you know, fully hardened mono steel blades are a bear to straighten after heat treat and it usually involves doing it at tempering temps with clamps. I pretty much only make kitchen knives and long, thin tapered mono steel invariably warps in some direction. I have recently begun making damascus out of non hardening steels and using it in a san mai configuration with high carbon steel or high carbon damascus in the middle. I am still working it out but I think the hassle of setting up the san mai is a better trade off then trying (often in vein) to straighten mono steel after heat treat. Time will tell....

 

 

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Scott,

 

It is important to put a thin ( I mean read the paper though thin) clay wash on the blade and let dry. The clay defeats, for the most part, the vapor jacket that insulates the blade. The vapor jacket slows the cooling ever so slightly. Maybe even the clay particles create more surface area for faster cooling. Dunno for sure about that one. Cuts down on the scale as well. As you know it is the vapor jacket in a water quench that contributes heavily to cracking the blade (uneven cooling). Brine is another way to defeat the vapor jacket. Can't say which is better. Not enough experience with either one. Point is you have to cool the whole blade quickly in the quench.

 

The trick is the right clay the right consistency. Not sure yet if there is other things besides just clay in it. The base clay needs to be a low fire earthenware with some iron in it (6% or so, iron oxide will act as a mild flux in a reducing atmosphere) I have had a few successes (and failures) with the limited experiments I have so far. Not confident enough to say what exactly works or not. I am thinkin' this is enough info for you to run with. :)

Edited by Danocon
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Scott,

 

It is important to put a thin ( I mean read the paper though thin) clay wash on the blade and let dry. The clay defeats, for the most part, the vapor jacket that insulates the blade. The vapor jacket slows the cooling ever so slightly. Maybe even the clay particles create more surface area for faster cooling. Dunno for sure about that one. Cuts down on the scale as well. As you know it is the vapor jacket in a water quench that contributes heavily to cracking the blade (uneven cooling). Brine is another way to defeat the vapor jacket. Can't say which is better. Not enough experience with either one. Point is you have to cool the whole blade quickly in the quench.

 

The trick is the right clay the right consistency. Not sure yet if there is other things besides just clay in it. The base clay needs to be a low fire earthenware with some iron in it (6% or so, iron oxide will act as a mild flux in a reducing atmosphere) I have had a few successes (and failures) with the limited experiments I have so far. Not confident enough to say what exactly works or not. I am thinkin' this is enough info for you to run with. :)

Yeah Dan.. I do need to get in the habit of doing that. It's probably beneficial for just about any kind of heat treat.. especially if you are going into heat treat with fairly close geometry.. which I'm increasingly doing with my little carving knives and tools.

 

As to iron in the clay mix.. I had read somewhere that this was done so that the smith could get an accurate color of the temperature. The iron flakes coming up to temp the same as the blade. Again.. not sure if this is true or even makes sense. But I read it. :-)

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