# Stainless san mai, core steel testing.......



## WillC (Oct 31, 2013)

Im very happy with 01 as an uber fine grained staple core steel. It takes a fantastic edge and gives reasonable edge retention whilst being very nice to sharpen. Exactly as you would want from a good carbon steel. 

I would like to flirt with some other options, not super wear resistant, but something a little less fine grained, toothier quality and greater wear resistance, whilst not being overly hard to sharpen. I have read lots of bad and good things about D2, many contradictory to each other. But from the offset and having read some excellent papers with heat treat tests on the steels grain structure and ultimate toughness I would say there is a lot in a heat treatment. So with my own testing Im aiming the the finest grain possible whilst being as hard as possible without being brittle. 

I tried a few different austenitizing temperatures which were quite close, these produced the finest grain to the naked eye.







I went with the later lower temperature for the rest of the samples. To me this grain is surprisingly small and even to what I have heard of D2. It is not as fine as 01 but finer than something like blue paper steel, which has a slightly courser structure to the naked eye. 
The pieces were 65hrc after a plate quench followed by cryo. They were also very very hard to break, Already some tough stuff over this thickness.

3 samples I then used to bracket my temper temperature. Each had 3 temper cycles at one hour. This is important to this steel it has been proven. I also gave them all a second cryo for good measure. 

Each piece I then ground and sharpened, a pretty crude grind but with a fairly low final angle about 15 degrees per side. With each I cut notches in some mild steel until they would no longer perform the task or until dulled significantly.





The one I have settled on as my ideal temper temperature managed this complete row without chipping in the slightest, just a little dulling which came out easily on a chosera 1000 grit stone.




This was the two with a lower temper temperature.





This is the piece with a slightly higher temper temperature and the HT I will settle on for further testing. Final hardness 61/62hrc





Next to make a knife out of it to get an idea how I like it on a much thinner edge and get a feel for edge retention vs sharpenability.

Im hoping to make same nice hard wearing slicey 210 line knives in this steel with stainless cladding. I am also waiting for some cpm 3v to arrive, which I believe I will like for different reasons.:cool2:

Ill update as I manage to get a san mai knife together with out melting the stuff


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## TB_London (Oct 31, 2013)

Looking good


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## HHH Knives (Oct 31, 2013)

Great testing photos. Thanks for sharing. I have worked with a few diffrent D2 steels and the D2 thats made of powder steel.. Is some amazing stuff! If ya really want to make it more wear resistant. Cryo it!! Takes it from tough to CRAZY tough!!


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## WillC (Oct 31, 2013)

Yep, these pieces were cryo'd twice. I did not try a piece without cryo, except for a hardness test prior to cryo and it brought it up 1-2hrc. Looking forward to trying it in context of a chef knife. Cheers Folks.


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## HHH Knives (Oct 31, 2013)

I missed that in your post. Sorry. Yep I have yet to try it as a kitchen knife. Mainly using it for camp knives, and or smaller carving knives. One you get the stuff sharp it stays that way a very very long time!! 

Have fun and thanks again for sharing


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## WillC (Oct 31, 2013)

Good to hear mate, thanks. Looking forward to trying the 3V too. I can only get it in 12mm so a fair bit of forging out if it works out in san mai. irate1:


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## Don Nguyen (Oct 31, 2013)

That's a really cool way of testing Will!


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## zitangy (Nov 1, 2013)

Hey Will,

It is always interesting to follow craftsmen trying out/testing new things which is a testament of their mastery of the basic skills required and is free to be creative and find new things, methods/ techniques to reach a new height of which is never ending.

Been following your tweaks as to handles, profiles, geometry, materials heat treats etc as it is informative and broadens my knowledge as to a well made knife in terms of form and function and what you guys go thru to make one. WIPS is always a joy to follow. Videoes.. can't ask for more.

Comparing your first few knives and the the recent few knives to your latest.... it has become a never ending quest for me too and I can't keep up with you.

Of all, my favourites are still the "USA Passaround" ( http://www.kitchenknifeforums.com/showthread.php/2796-300mm-Damascus-Suji-U-S-Pass-around) and the Twin Petty (( 68,000 layersdidn't manage to snag the Feather damascus) as it constantly reminds me of your journey... and I did't make a mistake is spotting a budding craftsman then.

Have fun.. always

D


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## WillC (Nov 1, 2013)

Thanks David, your, confidence in my work, support and advise has and is very helpful along the way


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## WillC (Nov 1, 2013)

D2 core san mai...




Stress relieving before doing a full anneal on two stainless damascus clad D2 core blades.


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## Lefty (Nov 5, 2013)

Me likey!


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## WillC (Nov 6, 2013)

Got these two ht'd, cryo'd and first temper cycle, two more full hour temper cycles to go. With forging more complex steels, makes the pre-heat treatment and heat treatment processes take much longer. The anneal cycles were 3 hours and cool in furnace, so basically 2 days of annealing before HT can begin. 



I also did a billet in plain stainless clad D2 as it was the perfect test for my new furnace, very narrow temperature band for success, it was a success A bar of 12mm x 50 x 1000 cpm 3V is on its way to me from germany.


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## Mucho Bocho (Nov 6, 2013)

Looking good Will. Some day I'll understand how all the processes come together annealing, tempering, forgiving, cryo...


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## jigert (Nov 6, 2013)

Mucho Bocho said:


> Looking good Will. Some day I'll understand how all the processes come together annealing, tempering, forgiving, cryo...


Forgiving is my favorite step.


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## WillC (Nov 6, 2013)

In simple terms
The main reason to heat cycle and anneal after forging is that the grain structure will be very large and crystalline after heating it up to welding temperature, then forging. Also during forging it may have become somewhat hardened, these are air cooling steels in this instance, so it is hard to avoid. The heat cycling reduces the grain size and removes stresses, Annealing ensures that it is in its fully un-hardened condition. 
Now you have a piece ready to heat up to critical temperature and quench to harden, in oil or air. In this case I used my hydraulic press to plate quench the blades, the plates under pressure take the heat quickly from the blade and this also helps keep it straight as a bonus.

After this you have cryo treatment - Short answer this helps you achieve greater hardness, especially in stainless and not at the expense of toughness.... and tempering, Tempering takes some hardness from the steel to ensure a good balance of toughness. In this case triple tempering is also shown to help reduce carbide size....therefore giving greater toughness at a given hardness......

Looking forward to testing these blades now........... Will have to wait till next week


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## WillC (Nov 6, 2013)

You should always forgive the steel, as its much harder than you.


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## chinacats (Nov 6, 2013)

WillC said:


> In simple terms
> The main reason to heat cycle and anneal after forging is that the grain structure will be very large and crystalline after heating it up to welding temperature, then forging. Also during forging it may have become somewhat hardened, these are air cooling steels in this instance, so it is hard to avoid. The heat cycling reduces the grain size and removes stresses, Annealing ensures that it is in its fully un-hardened condition.
> Now you have a piece ready to heat up to critical temperature and quench to harden, in oil or air. In this case I used my hydraulic press to plate quench the blades, the plates under pressure take the heat quickly from the blade and this also helps keep it straight as a bonus.
> 
> ...



Thanks, I needed that!


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## Mucho Bocho (Nov 6, 2013)

Thanks Will for taking the time to explain that. I've got to get over there, my buddy lives in Worchester and has been telling me for years to come and visit.


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## WillC (Nov 6, 2013)

Worcester? Only about half an hour from my workshop.
Here is a good paper on Metallurgy for bladesmiths. 
http://www.feine-klingen.de/PDFs/verhoeven.pdf
I often refer to this as I could never remember it all, well maybe one day. I have not really that type of brain, I just like to know enough to get a feel for what Im doing and take it from there with some real world tests. Where as the science would explain what is happening during the processes and transformations, in general I only wish to know what will achieve the best results, though I can see how a greater understanding of the chemistry can help so i do try to understand.
There is a great chapter on AEB-L in the above.


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## WillC (Nov 6, 2013)

This is the paper I read on getting the best toughness and as fine and even distribution of carbides in D2 as possible.
https://tspace.library.utoronto.ca/bitstream/1807/13366/1/MQ45596.pdf

I will be interested in the results in terms of a kitchen knife because that is my field of comparison with everything else in terms of how it sharpens, how sharp it gets, how the edge feels to the touch and in cutting and edge retention. Im sure it will be tough at this HT. D2 has been reported as many things, hard to sharpen, very toothy, tough, chippy. There is allot in a heat treatment for sure.
I hope with this heat treatment, I will have an optimum level of the toothy character of the steel, but tough with no microchipping, easy to sharpen, relatively fine edge. Its never going to be as fine and get as sharp as a super fine carbide steel like AEB-L or 14c28n, but I'm going for a different effect here, some teeth and an increase in wear resistance over fine carbides. For a real hard wearing slicer, that retains its teeth long after loosing the shine from the strop.
Will be very interesting to compare to cpm 3v, which should be a very tough steel also with good wear resistance, but with finer carbides, given correct treatment. So they should feel and cut slightly different. There are a few others I would like to try. None are particularly in the super wear resistant area. I might play with this later, but at the moment Im interested mostly in steels which are at least relatively easy to sharpen and work with.
Something like cpm 10v is an interesting proposition but poses issues in all areas as far as forging, grinding and maintaining a knife made from it.


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## Lefty (Nov 6, 2013)

Those were some prett amazing posts, Will. Now, I'll follow it up with this. Ready for it... :

Pierre made a slicer from D2 (I believe), and if I'm not mistaken, the owner was really impressed. I think you're onto something. And, I like ice cream.


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## WillC (Nov 6, 2013)

Yep lets see. I expect the D2 and 3v will be chalk and cheese. Its fun to play in these extremes to learn. Yeah the main concern is the D2 will not be terribly stable on a very thin edge due to larger carbides. Although the grain looks fine would need a micrograph to show up the large undissolved carbides. So I'm hoping I have pulled off something with my moderate HT in not going for extreme hardness and multiple temper cycles, cryo, all this should help reduce the larger carbides and give a more even distribution, but we will see. 
I have just found an excellent source for samples of many Bohler and latrobe steels, so more testing to come over future months. Obviously the pm steels get expensive so will be done gradually.


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## Don Nguyen (Nov 7, 2013)

How much of a difference would CPM D2 make Will? I imagine it would have all the neat properties of D2 but with finer carbides?


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## Timthebeaver (Nov 7, 2013)

Can I ask why you chose D2 over A2 steel Will?


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## WillC (Nov 7, 2013)

I really could not say without trying them side by side. If I find a use for D2, I may give it a try. 
I tried my sample piece with a very very thin edge, taken to zero in fact at a very shallow angle to see what happened. On a brass rod I got neat semi circular chips about 0.5mm diameter with not too much force. So I took the sample up in temper temperature by about 20 degrees, this stopped the chipping. But with this thin an edge, It was not exactly stable either there were instead little folds in the edge pushed to destruction, but these very limited. But on this thin an edge my 01 would show allot of flex before distorting slightly or ultimately chipping. Putting a secondary bevel on the sample totally changed it, I could now not mark the edge what so ever with a brass rod and again take notches out of my steel bench with no damage at all. So so far it seems the shape of the edge makes a difference, a little bit thicker at the edge gets the most out of this steel and it becomes very very tough in this format. Still thin at the edge but I would not choose this for a line knife I don't think. Just off the strength of this sample I think it would be fantastic for any thicker boning or filleting knife, or even a big carving knife, would be no worries being hammered or sliced through and against bone so long as there is a distinct secondary bevel, and it can still be thin, it just needs to be there and more so than the tiniest of micro bevels as with my carbon/14c28n knives. I will keep this in mind with my test blades. Im now thinking Honesuki:knight: 
The 3v has arrived also, its a huge chunk, nearly 14mm thick, by 50mm by 1000mm, (smallest they had)! I'll have to grind it down a little to san mai it with some 12mm for plain stainless clad.


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## WillC (Nov 7, 2013)

@Tim

One steel at a time. This experiment is about taming something with notorious teeth and putting them to best use and with the best possible heat treatment. I do like a challenge. I have pretty much decided D2 will not be suitable for an all-round chef knife, it looks like it can be made to be more suitable with the right HT, but it seems to really excel with a slightly thicker edge, where as others would excel on a thin edge, so I think it would be wasted on anything else. I will still take my samples blades to the thinest possible edge and test them and can thicken the secondary bevel till I reach that magic point. I think they will make some incredible Honesuki or Big sunday joint carver.

A2 looks like a contender for a more wear resistant line knife, I think that would be a vs 3V experiment. But 3V will come first, as a girt big chunk of it just turned up from germany.


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## Mucho Bocho (Nov 7, 2013)

WillC said:


> Big sunday joint carver.



Will, your really tryin to meet the demands of the US market, thats for sure. Several states are changing their laws so that soon there may actully be a market for a Big Sunday Joint Carver. 

Myself, I'm looking forward to it. 

:biggrin:


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## WillC (Nov 7, 2013)

Ah I think your confusing meat on the bone with camberwell carrots.:lol2:


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## Mucho Bocho (Nov 7, 2013)

WillC said:


> Ah I think your confusing meat on the bone with camberwell carrots.:lol2:



Ya had me on that one Will, Had to look it up.

camberwell carrot 
A Camberwell is made up of 12 papers that's about 18" long and filled with pure grass. The term comes from the cult classic film Withnail and I.


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## WillC (Nov 7, 2013)

Thats the baby, great film:biggrin:


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## zitangy (Nov 7, 2013)

WillC said:


> Yep lets see. I expect the D2 and 3v will be chalk and cheese. Its fun to play in these extremes to learn. Yeah the main concern is the D2 will not be terribly stable on a very thin edge due to larger carbides. Although the grain looks fine would need a micrograph to show up the large undissolved carbides. So I'm hoping I have pulled off something with my moderate HT in not going for extreme hardness and multiple temper cycles, cryo, all this should help reduce the larger carbides and give a more even distribution, but we will see.
> I have just found an excellent source for samples of many Bohler and latrobe steels, so more testing to come over future months. Obviously the pm steels get expensive so will be done gradually.



Hi Will,

Dont know enough abt steel..

reading metallurgy .. quite hard for me to absorb. Based on the above, you are attempting to get the best out pf the steel ( mono steel) in terms of performance and edge retention.

A possibility could be folding the 2 different type of steel each excelling in the specific criteria and making a solid damascus of it provided that they both have the same HT treatment process/ criteria with less priority on how the contrasting damascus would look like.. .. a thought inspired by your early piece where by the damascus was not so contrasting.

In terms of percentage increase of edge retention, are you expecting a significant jump?

Have fun.


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## WillC (Nov 7, 2013)

Yes damascus of the right choice can give a nice toothy nature and excellent edge stability. Old school damascus of 1080/15n20 does offer a nice toothy edge, especially if all the weld cross the edge like in a W's based pattern like feather. 

This is just me taking opportunity to test some different and more complex steels to offer another option or two eventually in san mai. It also gives me an introduction to welding a few different steels. This might come to play in damascus work later, its all good learning, and while I'm learning about the steels I'm also learning the critical measures to welding them together and how to treat them after forging.

But for now its just to offer some new options in san mai and have an opportunity to test them. 

With regard to wear resistance, yeah there will always be a big leap as you add wear resistant alloys or more carbon but its going to be at the expense of something else. So its about finding a balance for me. Having said that I will have to try one of the super wear resistant steels eventually, like 10V, or a more moderate one like rex cpm M4, just so I can try it.


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## Timthebeaver (Nov 8, 2013)

WillC said:


> Thats the baby, great film:biggrin:



Scrubbers!

Thanks for the answer Will, your contributions here are most awesome.


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## WillC (Nov 8, 2013)

So many classic lines

Due to small tool breakage I got to get the two samples together for a weekend of abuse.
One all rounder petty gyuto profile and another Pettysuki style. Both ground double bevel, coves, and taken as thin as normal at this stage. That is they have not been hand finished yet, so they would go a bit further after that. But they are relatively thin on the edge for sure. Here are the sample blades. 










And some geometry and bevel shots. The blades sharpened very easily. I set the bevels on 400 grit, and took them to 5000 with a brief strop. Anymore would be wasted, they push cut hairs nicely. No issues with sharpening at all. The bevels I set at 15 degrees per side. 






















They are basically like a knife which as been thinned as far as it will go, after a couple of sharpenings, so just about the best place in terms of thinness vs edge retention.

Will see what it takes to chip or distort the edge over the weekend and see what it takes to break a tip etc.

So far a flex test on very thin edge towards the tip was very promising. The edge flexed a long way and returned. I was expecting to see damage to be honest on such a thin edge, judging from what I saw with my test piece, so that is a very nice surprise. I will push one to destruction at some point over the weekend, will see what happens in normal use and fair tests first.

One thing to consider is that my core may have lost a tiny percentage of carbon, I did not use a carbon barrier or see the need as the start materials were very thick so I doubt it would be much and lets face it D2 has plenty to spare so it could only improve things. Plus a little carbon escaping is very pretty on a well finished blade.

So far neither showing any sighs of distortion of chipping so actually looking good.

The nature and feel of the edge is toothy. Even polished it really sticks in a nail, a nice edge for food at the moment I have to say.
Will give a full report and updates and some horror damage abuse shots over the weekend.

Yes I used damascus cladding for test blades, not very clever, but I think we will get a couple of nice knives out of these even if they may be a mill or two shorter after some abuse.


And......... for laters.....

Cpm 3v core san mai cooling in the furnace.


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## WillC (Nov 9, 2013)

So far I have been abusing the Pettysuki in a most un kitchen knife like way, to establish the parameters of the steel.

I cut through a steel can on a polished thin edge, this was expected to destroy the edge in someway, it was done with very little care. The edge rolled towards the thinest part towards the tip. Damage was very minimal however and any hint of ripple to the edge was removed on a *400 stone.

I jabbed the tip in my board and bent the tip around to destruction. The thinest part on the end stayed bent, on bending it back the other way it came away. No more than 2mm was lost.

Some edge further edge deformation tests, I hacked badly and while deliberately twisting the knife out of the wood through a 2 x 2 inch piece of wood. It took a while with a petty with no handle:knight: But there was no edge deformation whatsoever, intact the knife still cleanly shaved arm hair though was duller to the touch on the central part used for the hacking.

Brass rod test once again, edge shows a very acceptable amount of flex, pushed to destruction and with considerable effort the edge distorts on a thin edge rather than chipping. I have not managed to chip the blade yet. 

So what does all that tell me, well , Im happy with the HT and the steel at around hrc 60/61, any more hardness than that and any less care during the prep and ht would lead to those little cemi circle half mill chips on a thin edge. I think the HT has made this steel stable enough on a very thin edge if required and it excels where the edge is just a fraction thicker. 

It gets no where near as fine a sharp edge as a fine grained steel like 01, it has teeth and bite from the off however, so this is as hoped and expected from nature of the steel. 

On edge retention. Hard to say, I will comment more on this tomorrow. But from these test it will handle some very heavy tasks even abuse and still make fine cuts.

I will try the other blade on a pile of food tomorrow. 

Working out what to cook, I might get some chickens to deck with it for paprika chicken and a pile of veg and tomatoes for before and after test. Any other ideas or requests let me know within reason and bearing in mind a big test will keep me in dinner for a week


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## WillC (Nov 9, 2013)

Right, just processed some dinner, with the more petty shaped one. I've worked up a fair appetite
Quick strop and straight off into tomatoes so I can see how the edge feels. It push cuts and slices acceptably, sticks once on the skin. Feels nice in onions especially on horizontal cuts, and slicing. Felt a bit aggressive on push cut on onion. Carrots and leeks feels great and Peppers no matter if they are skin side up. So for all the veg prep it works and actually feels very nice through some tougher stuff and slicing. Then the chicken, it has a relatively thin edge for a knife to be pushed and sliced through bone, it really excels at this task. Made very very light work of the chicken indeed and I have the feeling it could have down it all day. 
Back to tomato and it cuts exactly the same, push cuts but doesn't feel great as before. No damage whatsoever to the edge, quick strop and good as new.



















So in conclusion for D2, yes with the right heat treat I can get a decent all round kitchen knife out of it. But there are better steels for that purpose, it just does not get as super fine sharp enough to give satisfaction on push cuts.
But for tough stuff this steel with this HT I really like. I think I would like to consider this steel for hard use boning knives, that can turn its hand to finer stuff where required. It really excels over carbon in offering confidence going through bone etc on an edge which you would think too fine for that purpose.


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## zitangy (Nov 9, 2013)

WillC said:


> So in conclusion for D2, yes with the right heat treat I can get a decent all round kitchen knife out of it. But there are better steels for that purpose, it just does not get as super fine sharp enough to give satisfaction on push cuts.



Hi Will,

Interesting observation..

*Push Cuts.* Being superfine sharp may not have direct relation to ability to do a satisfying Push cut.

I have problems with push cuts on paper with my sharpening and I do not quite understand as to why it can do a pull cut beautifully and not the opposite ( push cut) when doing paper testing. In real life application I do not see much of a problem as a push cut exerts more pressure on the item being cut.

One of the main reasons I suspect is the angle of the striations in relation to the edge or it cld be that there is more pressure on the item being cut and hence the feel is not the same.

I could be wrong on these two points.

Thanks for posting the WIPs.

RGds
d


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## WillC (Nov 9, 2013)

Push cuts in tissue paper is a good one beyond thin rizla paper..........certainly not all steels are capable of being sharpened to that fine an edge. Or the hanging hair test. Damascus is a mistake for the edge of a straight razor, there is no way I would make a razor from D2 either
Once you have ruled out the variations, angle, level of polish on the edge, etc....you realise its a steel thing.
01 I can get sharp enough to push cut tissue paper as can 14c28n. Larrin has put up some excellent micrographs of the edges of cpm 154 vs aeb-l. A steel with larger carbides, won't be able to take as small a radius edge as a fine carbide steel. 
Its a feel thing really, but the result is D2 feels different in food than 01. Its subtle but there. And in some cases it gives some advantage in slicing and cutting through bone.


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## Timthebeaver (Nov 10, 2013)

That pettysuki looks like a cracker Will. If it ever fancies a short trip to Bristol for further testing... :O


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## WillC (Nov 10, 2013)

Tim it could be really handy to have an individual near by for quick second opinions. Do please shoot me a pm with your details and usage. I actually get over to bristol quite allot, I have friends in the area. 
These two, as are damascus and i'm happy with them, I will finish and sell in the next couple of week to help balance costs.
I have another plain stainless clad blank in D2 core I would like to be a Garsuki, I enjoyed this on chicken so much, 
I think that would be a cool knife to use D2 for as would Atso Deba and Hankotsu was another idea. I have other steels to try too though.
Then there are the two in cpm 3v core. These will be medium size Gyuto, 220mm ish.


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## Lefty (Nov 10, 2013)

Will. Now that Tim is covered - what about your good buddy Tom?


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## WillC (Nov 10, 2013)

Tom if I send something your way to Saya and sell, then you will get to have a play, won't you


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## Lefty (Nov 10, 2013)

Yes. But it won't make sense when I buy it from myself....


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