Stainless Heat Treating question

S

Siddhi

Joined
Jul 14, 2014
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6
Hello all,
So I had a piece of M390 laying around my shop for some time now. I decided to make a Sushi knife out of it. I have read it has good hardness and corrosion resistance. Plus I needed something to do. haha.

Anyway I have just a few questions. I have made a few knifes in the past but everything has been with carbon steels. This is my first attempt at stainless.

1. Does M390 make a good Sushi knife?

2. Since I am making a sushi knife ground only on one side can I go ahead and grind the bevel in or should I wait until after heat treat? I am basically wondering if since I am plate quenching will it help minimize warping? If I do it in carbon steel I heat treat prior to grinding cause I don't want it to warp on me.

3. With M390 is cryo treating a must? I have read mixed reviews. Can I get it hard enough to work as a heavily used Sushi knife.

Thanks for any replies,
-Barry
 
1. I'd say Nah, the usual clientele prefer Carbon so it's easier to maintain the large thin bevel on ceramic and natural stones, also will finish better. M390 will have less stability for that type of use and the increased wear resistance may not be appreciated in that application.

2.Plate Quenching helps but is never a guarantee against warping so you best have your straightening game and quenching game squared away. I prefer to grind partially or not at all to mitigate this, also grind only with fresh abrasive and lots of water to protect the heat treatment.


3. It's not about hardness, it's about Microstructure. Cryo improves the Microstructure for better edges. Increased hardness depends on what Austenitizing temperture you harden from. With cryo you can run hotter and get harder since you'll be converting more softer structured retained austenite to martensite. Retained austenite is not desirable for a thin strong and stable edge, neither is a soft matrix (overall hardness) so they go hand in hand. Using M390 without a cryo is a waste of m390.







Siddhi said:
Hello all,
So I had a piece of M390 laying around my shop for some time now. I decided to make a Sushi knife out of it. I have read it has good hardness and corrosion resistance. Plus I needed something to do. haha.

Anyway I have just a few questions. I have made a few knifes in the past but everything has been with carbon steels. This is my first attempt at stainless.

1. Does M390 make a good Sushi knife?

2. Since I am making a sushi knife ground only on one side can I go ahead and grind the bevel in or should I wait until after heat treat? I am basically wondering if since I am plate quenching will it help minimize warping? If I do it in carbon steel I heat treat prior to grinding cause I don't want it to warp on me.

3. With M390 is cryo treating a must? I have read mixed reviews. Can I get it hard enough to work as a heavily used Sushi knife.

Thanks for any replies,
-Barry
Click to expand...
 
Thanks DeadBoxHero for the information. too bad it will not make a good steel for Sushi. I have it profiled and flattened already so I guess I will finish it for myself and see how it works. Thanks for the clarification on cryo. That makes much more sense now.
 
Can you make a slicing kn ife out of M390 - sure. It doesn't reach the hardness of most slicers, though.
I like to grind the bevel after HT.
Cryo or sub-zero treatment in a dry ice slurry is needed.

I make a fair number of yanagiba (AKA sushi knife). The edge is almost always carbon steel. These knives have to be regularly touched up to remain at the sharpness level needed. Stainless and other super steels usually won't attain as good an edge as high carbon without a lot of sharpening work. I have made some in CPM-S35VN which can be made very sharp. However, they aren't what the chefs want because that steel is a bear to re-sharpen.

I suggest 1095, W2, or the Hitachi/Takefu paper steels. My favorite is suminagashi with white core.
 
Hey Stacy,
Thanks for the info. I have made a yanagiba out of some Cru forge V that I had. The edge was great and it was easy to sharpen. The problem is it stained VERY badly once used on some raw fish. Since you make a fair number of them do you mind giving me a run down on what I should shoot for? You say your favorite is Suminagashi with white core. Is this your edge steel? What do you use as your base steel? I have never made anything with a base and an edge steel so I am unfamiliar with the technique. But I would love to know how to do it. Any info would be greatly appreciated. I love trying new things.

Thanks a lot for anything you are happy to share. If not I completely understand.
-B
 
One of the questions I have is when creating the San Mai how many layers do you use on each side? Since the Yanagiba is chisel ground how do you makes sure you have the edge steel in the correct spot to take the edge? I am searching this topic now to get some info. I ran across a post you made back in 2016 on Japanese steels.
 
Siddhi said:
One of the questions I have is when creating the San Mai how many layers do you use on each side? Since the Yanagiba is chisel ground how do you makes sure you have the edge steel in the correct spot to take the edge? I am searching this topic now to get some info. I ran across a post you made back in 2016 on Japanese steels.
Click to expand...

Um, San-Mai means 3 layers. I actually think it translates to “three flat things”.
 
Thanks JTknives for the clarification. What is the process called for using a core steel and an edge steel to make a Yanagiba? I have only made a handful of knives and swords so I am new to the terminalogy.
Thanks,
-B
 
"Ni-Mai"
二枚 Two Layers/sheets.

"San-Mai"
三枚 Three Layers/Sheets

I'd recommend you doing some reading on japanese knife construction, also perhaps purchase a yanagi to compare construction and geometry to your work and practice sharpening and using it so you can understand how it works. May help you figure it out.
Good luck.
Siddhi said:
Thanks JTknives for the clarification. What is the process called for using a core steel and an edge steel to make a Yanagiba? I have only made a handful of knives and swords so I am new to the terminalogy.
Thanks,
-B
Click to expand...
 
DeadboxHero,
Thanks for the info. Like I mentioned I have already made one out of some Cru Forge V that I had. It turned out great and my friend who owns a sushi restaurant and is a master sushi chef used it and told me the design and handling was great. The edge retention was fine, but the biggest complaint was the staining of the metal after cutting some fish with it. So I thought I would try a stainless and had the m390 sitting around. Here is a pic of my first attempt (Well I am not sure if the image will show up. It is acting strange and I followed the instructions).

By the way I do make my own damascus and am pretty familiar with forge welding. I just have never done anything where I have a core steel and an edge steel. From what I have read some actually forge weld a high carbon steel to a stainless core steel. I have been searching the subject but I cannot find much info on the process. I did see a few youtube videos (Murry Carter makes a sashimi knife) but there is not a lot of details.
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A single grind edge blade is usually ni-mai, sometimes just called "laminated steel". You can buy it from Dictum, IIRC.

Many folks weld up their own billets. W2 and iron (anything from pure iron to 1030, to 203E ) makes a good combo.

In a two layer billet, make sure you keep track of the hardenable side by dunking it in some FC before you start shaping the knifes. The hardenable steel goes on the ura (back side) of the blade. If you do it backwards, the knife will be left handed (or right handed if you are making the knife for a leftie). Don't ask why I know this :D

HT on ni-mai is a bit tricky, as warp can be a big issue. Quench plates are a must.

When using san-mai ( three layers) or suminagashi ( three layers, with the outside layers being damascus), you have to modify the ura ( back side) a bit from the classic grind. The simplest way is to grind a full flat grind on the ura until it just reaches the core. Then shape the urasuki ( large hollow grind) as normal. You can also skip the urasuki and leave the back flat. Once the ura is established, grind the omote (front side) as normal to create the edge. You want to get/make a slightly thicker than normal billet so the thinning of the backside doesn't make the final blade too thin.

Dictum sells many forms of blade steel with a Hitachi white or blue core and various cladding ranging from pure iron to stainless steel damascus. Takefu also sells a lot of the same billets.
 
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