Geometry for Yanagi Bocho sashimi knife?

S

stezann

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Apr 13, 2011
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I'm dreaming about making a right hand japanese kitchen knife; since i don't have a contact wheel, i'm going to build a convexe platen for my grinder...can someone indicate me the radius fitting the "flat" side (the left) of the blade? Also, the right side bevel is it flat or concave? The max thickness at the spine?

When forging the blade, am i going to hammer "to shape" or just distal taper and then make it asimmetrical by grinding after the heat treatment? I'm asking just in case the asimmetrical geometry might or not lead to serious warping when quenching. Is it a real concern or the blade might behave like a simmetrical one?

I have not yet decided if it is a plain w2 or a mild/w2/mild otherwise 52100.

Thank you for any insight into my project. :)
 
Let me preface this by saying that I've not made a yanagi before.

I believe you want the hollow grind on the "flat" side to be a very large radius, approximating the grind you'd get from a 36"-48" contact wheel. Max thickness at the spine I'd think shouldn't be above .100. The right side bevel will be flat.

I don't know if a chisel type grind like this will warp more than a symmetrical grind.

There will be people here who know more about these than I, like Butch Harner and probably Stacy, another good place to ask questions like these would be over at Kitchen Knife Forums. I mean it in the best possible way when I say that there are some kitchen knife NERDS over there.
 
Ohhhh...that sounds interesting.

Are you heat treating before grinding bevels?
 
Salem Straub said:
Let me preface this by saying that I've not made a yanagi before.

I believe you want the hollow grind on the "flat" side to be a very large radius, approximating the grind you'd get from a 36"-48" contact wheel. Max thickness at the spine I'd think shouldn't be above .100. The right side bevel will be flat.

I don't know if a chisel type grind like this will warp more than a symmetrical grind.

There will be people here who know more about these than I, like Butch Harner and probably Stacy, another good place to ask questions like these would be over at Kitchen Knife Forums. I mean it in the best possible way when I say that there are some kitchen knife NERDS over there.
Click to expand...

Eh eh! :) thank you very much for the kind reply... I think I will leave quite a bit of meat before heat treatment and do consistent normalizations...and finger-cross to the quench. Now i'm going to build the 40" or alike convexe platen for the first thing. have a nice day
 
AVigil said:
Ohhhh...that sounds interesting.

Are you heat treating before grinding bevels?
Click to expand...

Depending on how close to shape is it possible to put into a quench, having an asymmetrical geometry involved...of course i know is a pita :) I would like SOOO much if someone who did it would tell me to go and quench a 600grit finished blade without worring ;)
 
I've not made a single bevel knife either, but I've talked to enough people who have about doing it and therefore feel comfortable enough stating this:

Warping will likely be an issue if you grind the knife before heat treating.

Spine thickness varies tremendously based on length. 180mm is not nearly as thick over the heel as a 300mm yanagi. This will also vary based on design. A fuguhiki is, for lack of a longer explanation, a thinner yanagi made specifically for fugu (puffer fish). You can make a yanagi thinner or thicker if you want. A "typical" 270mm (common length) yanagi is probably going to be in the 4 - 5mm thick over the spine (0.15"+). This information comes from using/owning/etc. quite a few yanagi. I don't currently own one as I just never found good uses for mine, so I can't actually measure one at the moment for you.

The right, bevel, side is (I need to be careful here) traditionally convex on a real proper yanagi as I understand it. Most often they are ground rather flat though and a small secondary bevel is put on and then blended in. That's how I always sharpened mine.
 
watercrawl said:
I've not made a single bevel knife either, but I've talked to enough people who have about doing it and therefore feel comfortable enough stating this:

Warping will likely be an issue if you grind the knife before heat treating.

Spine thickness varies tremendously based on length. 180mm is not nearly as thick over the heel as a 300mm yanagi. This will also vary based on design. A fuguhiki is, for lack of a longer explanation, a thinner yanagi made specifically for fugu (puffer fish). You can make a yanagi thinner or thicker if you want. A "typical" 270mm (common length) yanagi is probably going to be in the 4 - 5mm thick over the spine (0.15"+). This information comes from using/owning/etc. quite a few yanagi. I don't currently own one as I just never found good uses for mine, so I can't actually measure one at the moment for you.

The right, bevel, side is (I need to be careful here) traditionally convex on a real proper yanagi as I understand it. Most often they are ground rather flat though and a small secondary bevel is put on and then blended in. That's how I always sharpened mine.
Click to expand...

Thank you for the information: is exacty what i was fearing... more, if you consider i am not confortable yet with straightenig doing interrupted quench if it bends!!! I like this type of knives and i like honing on whetstones...relaxing time

I tought the backside was slightly hollow...to put it flat on the stone making contact only spine-edge like as honing straigh razor but i think in a japanese kitchen could be a 10000 of different design very specific for different meals...maybe the design i had in my mind is not the yanagi
 
The backside is hollow, I don't believe I said anything to the contrary...but sorry if I did. There is a flat spot at the spine and the edge that ride on the stone, and the middle is hollow/concave. As Salem mentioned, the hollow can be approximated with a convex platen with a radious of 36 to 48".
 
sorry i misread right side for back side...here in italy is 18:00 and i was working all the day so i'm little boiled ;) Thank again for the info...i'will try to make a good use of them...if my project won't explode in the quench i will post the photographs.
 
I have made a few but far from expert, I did use a 4' diameter hollow on the back but it seemed to shallow so now I use a 3' and like it much better. I do a flat grind on the face to about 0.015 and then hand sand or stone to 0.010. Like mentioned the length determine the thickness, the long yani in the pic is 3/16 the short 1/8. I like thinner but traditionally I think they would be thicker. I only grind the face bevel prior to heat treat to reduce the potential or warping, the hollow is not very deep and easy to grind after heat treat.

If you are forging with carbon steel a hamon is a must!!! That will make a killer blade.. Good luck

Two Yani.jpg
 
wonderful knives of yours!!!! i started the forging of the blank, but starting from a file it resulted only in a 7" blade lenght x 2" high, 5,5 mm at the "ricasso" and full tapered to a point. I choose a file because here in sardinia we have only k720 (o2) c70, wich contains a lot of manganese and stainless, wich i don't like/manage to treat properly. The file i'm going to consider as a plain high carbon steel, and i'm going to shoot for a clayless hamon...i can always try at least.
Patrick: so You grind in the bevel, and go in the quench with asymmetry? the shinogi ridge is going to help with warping issue giving rigidity?
I also made a billette with mild/c70/mild wich is bigger and i'm saving for the day i decide to make a bigger one, when i find the time!!!! :) I'm going to build the convexe platen 3' radius as per your suggestion. Thank You all!!!
 
butcher_block said:
i think most all is covered btu i ll offer a pic or 2
http://www.harnerknives.com/wp-content/gallery/holding/dsc06637sm.jpg
http://www.harnerknives.com/wp-content/gallery/holding/dsc07695sm.jpg
http://www.harnerknives.com/wp-content/gallery/holding/dsc07718sm.jpg
http://www.harnerknives.com/wp-content/gallery/holding/dsc07714sm.jpg
Click to expand...

I like it a lot!!! appreciate the hollow side, underlined by the high end honed contour at the spine/edge, and the beautiful handle! am i seeing the bevel side is hollow too, am i right or is it the picture? is it to speed the honing process? And can You tell me how do You go to the heat treating process regarding the shape?
 
Lloyd's photos pretty much show it all.

I only forge in a very rough flat and bevel on the face side. The edge is very thick at HT. I grind and stone the final face to shape after HT. Once the bevel is pretty well shaped, I form a 48" hollow grind on the back. Then I give the back a light stoning to make a small flat at the edge and spine. About 1/16" is all you need. I take that flat to a surface plate with 220 grit paper and make the flat as crisp as possible. This forms a straight edge. From there you just refine the face bevel and get the edge angle set. Progressively finer stones/grits will finish the edge. The last step is to bring the small flat on the back and the bevel on the face to a perfect honed edge.

As for laminating the steel, you need the cutting steel on the back side, so a mild/W2/mild san-mai would have the mild steel doing the cutting....this would be bad.
Make a two layer billet with mild steel and W2 and use the W2 as the back side. A low layer count damascus also makes a nice look for the upper flat on the face side. Wrought iron does good, too.

If you truly want san-mai, there is an alternate method of forming the billet. Make it with the core running diagonal. Use a low to medium layer damascus for the outside layers , and a hard mono-steel for the core.That way the hard mono-steel core will become the edge when the back is ground, and the damascus will become the upper part of the face and the upper part of the back.
I had a batch of damascus san-mai made up by a well known maker several years back and the billet twisted in the hammering....resulting in a diagonal core. At first I thought it was useless, because it was intended to be sword stock. But I realized that it would make chisel grind blades just fine...so I made some kata-kiri-tsukuri blades from it, as well as some kitchen blades. I still have a good bit of it left...time to make some big kitchen blades.
 
bladsmth said:
Lloyd's photos pretty much show it all.

I only forge in a very rough flat and bevel on the face side. The edge is very thick at HT. I grind and stone the final face to shape after HT. Once the bevel is pretty well shaped, I form a 48" hollow grind on the back. Then I give the back a light stoning to make a small flat at the edge and spine. About 1/16" is all you need. I take that flat to a surface plate with 220 grit paper and make the flat as crisp as possible. This forms a straight edge. From there you just refine the face bevel and get the edge angle set. Progressively finer stones/grits will finish the edge. The last step is to bring the small flat on the back and the bevel on the face to a perfect honed edge.

As for laminating the steel, you need the cutting steel on the back side, so a mild/W2/mild san-mai would have the mild steel doing the cutting....this would be bad.
Make a two layer billet with mild steel and W2 and use the W2 as the back side. A low layer count damascus also makes a nice look for the upper flat on the face side. Wrought iron does good, too.

If you truly want san-mai, there is an alternate method of forming the billet. Make it with the core running diagonal. Use a low to medium layer damascus for the outside layers , and a hard mono-steel for the core.That way the hard mono-steel core will become the edge when the back is ground, and the damascus will become the upper part of the face and the upper part of the back.
I had a batch of damascus san-mai made up by a well known maker several years back and the billet twisted in the hammering....resulting in a diagonal core. At first I thought it was useless, because it was intended to be sword stock. But I realized that it would make chisel grind blades just fine...so I made some kata-kiri-tsukuri blades from it, as well as some kitchen blades. I still have a good bit of it left...time to make some big kitchen blades.
Click to expand...

Thanks Stacy!! the san mai is to be cheated ;) I was planning to expose the core grinding the back and then proceeding forging...resulting in something like an offset-diagonal core! I'm so grate to You all answering to my questions, since i take in great consideration Your work and i'm crawling around this forum for a couple of years, trying to adsorb your immense knowledge; i have print all the info within the stickies on heat treatment and i got them aside my bed!! When i'll be confident enough with my blades i'll be honoured to post to share with You all!! :thumbup:
 
the first few sushi knives i made hollow front side with the same 4 foot wheel now i just make them flat

most the guys i have met end up flat grinding the factory beveled knives (they start slightly convexed )

if a buyer wants i will now hollow the front for them but 99% of the ones i have made lately are flat ground (tho i much perfer honing the hollow ground fronts )
 
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