An Existential Hardness Question

[Cushing H.]

I spent yesterday afternoon and evening cooking a chinese banquet for our families with an old friend of mine (who is originally from china). He is an incredibly good cook - and it is always a pleasure to share the stove with him - so I was determined to offer him a wide selection of (sharp) knives for food prep. we both like extremely sharp knives.... The knife below I bought about 30 years ago, and over the years has been extremely well used:

this knife can no longer be found (except on Ebay), is from china, and is made from a pretty soft steel (guessing at something like 55-57 rockwell). Here is the point: about 12 years ago my wife decided to use this knife to chop through some bones - with the result of some really nasty chips at the heel of the edge. the knife has been sitting since then waiting for me to get around to "repairing" it. yesterday I decided to do so in case my friend would want to use it. (please ignore The rather nasty looking grind at the edge, which is a result of a test to see whether there was any way to re-bevel at least a portion of the blade (turns out not possible - way too much warp in the blade - to really bevel the edge would result in the spine making contact with t he belt - unless I played games with moving way up to the top of the platen, which I did not want to do).

Here is the point: once focusing just on the edge (not the bevel), with a 120 grit belt with this softer steel, I was able to re-profile the edge to convexity, then get enough of a local bevel in place, followed by a 15 degree edge (using 400 grit belt) to get this blade back to full usefullness, and screaming sharp. Took maybe 20 minutes. Now I fully realize that this edge will not keep long - but the conflict I have is that maintaining a blade and bringing it back to full sharpness with these softer steels is SO EASY and fast. If it gets a little dull which doing food prep, 30 seconds with the ribbed steel pretty much brings that performance back. If I really want back that screaming sharp blade (which I usually do!), it is 5 minutes work on the grinder and it is done.

Compare that with a harder steel, for example this VG-10 blade at 62 Rockwell:


Yes, the edge is sharp, and will stay that way longer than that softer old timer .... but if I am in the middle of food prep and I discover it is not performing, NO WAY would I expose the blade to a steel (can you say edge chips??). Working on the grinder would also take longer, and also require more heat management so as to not kill the temper.

I am truly torn: there is definitely something about the newer and harder steels in their ability to gain a really sharp edge - but it is what comes after, during wear and use and when you are in the middle of food prep, and it takes more time and care to bring back that edge (and you dont have that time, because you need to get that food onto the table.....) where the softer steels seem to be more "forgiving".

I strongly suspect I am going to get hammered on this, because so much focus here is on advanced, harder, steels during manufacture .... but I continue to wonder whether a softer steel is still quite beneficial from a maintainability/ quick sharpen-ability perspective. What say you all???

 

[lanternnate]

There is something to be said for a steel and heat treat combination that results in a blade that can be sharpened easily. Those ribed steels aren’t really sharpening the blade. They realign the blade. That works with a softer blade that just rolls a bit at the edge, which then gets rolled back to center by the steel. The harder stuff doesn’t roll, it dulls or chips. The steel isn’t going to do anything about that.

The same thing can be said about a knife in the field. Yes, there is value to a blade that holds its edge while cutting hide, but if it’s too hard and wear resistant it can backfire too. Field sharpening is less than ideal conditions, so a knife that is hard to sharpen is a real problem if it needs a touch up in the middle of processing the game. It could be argued that a blade that holds the edge a little less but can be easily brought back on a field stone would do the job better.

To me, it’s like most of life: balances, trade offs, and personal preferences.

 

[DeadboxHero]

I say with good HT, the right steel and Geometry you can have both.

That knife is not a good representation of all knives at 62rc.

Its a more complex subject than simplifying
hardness values as the exact reason why something is better or worse and telling us everything about edge performance fixed to a specific number.

The underlying microstructure that created that hardness is what's doing the work better or for worse.

The reason why hardness is important however is so the wonderful edge we create actually holds but we don't chase the highest hardness number if we can't balance it at that value with a solid microstructure.

I spent yesterday afternoon and evening cooking a chinese banquet for our families with an old friend of mine (who is originally from china). He is an incredibly good cook - and it is always a pleasure to share the stove with him - so I was determined to offer him a wide selection of (sharp) knives for food prep. we both like extremely sharp knives.... The knife below I bought about 30 years ago, and over the years has been extremely well used:
View attachment 1252494
this knife can no longer be found (except on Ebay), is from china, and is made from a pretty soft steel (guessing at something like 55-57 rockwell). Here is the point: about 12 years ago my wife decided to use this knife to chop through some bones - with the result of some really nasty chips at the heel of the edge. the knife has been sitting since then waiting for me to get around to "repairing" it. yesterday I decided to do so in case my friend would want to use it. (please ignore The rather nasty looking grind at the edge, which is a result of a test to see whether there was any way to re-bevel at least a portion of the blade (turns out not possible - way too much warp in the blade - to really bevel the edge would result in the spine making contact with t he belt - unless I played games with moving way up to the top of the platen, which I did not want to do).

Here is the point: once focusing just on the edge (not the bevel), with a 120 grit belt with this softer steel, I was able to re-profile the edge to convexity, then get enough of a local bevel in place, followed by a 15 degree edge (using 400 grit belt) to get this blade back to full usefullness, and screaming sharp. Took maybe 20 minutes. Now I fully realize that this edge will not keep long - but the conflict I have is that maintaining a blade and bringing it back to full sharpness with these softer steels is SO EASY and fast. If it gets a little dull which doing food prep, 30 seconds with the ribbed steel pretty much brings that performance back. If I really want back that screaming sharp blade (which I usually do!), it is 5 minutes work on the grinder and it is done.

Compare that with a harder steel, for example this VG-10 blade at 62 Rockwell:
View attachment 1252499

Yes, the edge is sharp, and will stay that way longer than that softer old timer .... but if I am in the middle of food prep and I discover it is not performing, NO WAY would I expose the blade to a steel (can you say edge chips??). Working on the grinder would also take longer, and also require more heat management so as to not kill the temper.

I am truly torn: there is definitely something about the newer and harder steels in their ability to gain a really sharp edge - but it is what comes after, during wear and use and when you are in the middle of food prep, and it takes more time and care to bring back that edge (and you dont have that time, because you need to get that food onto the table.....) where the softer steels seem to be more "forgiving".

I strongly suspect I am going to get hammered on this, because so much focus here is on advanced, harder, steels during manufacture .... but I continue to wonder whether a softer steel is still quite beneficial from a maintainability/ quick sharpen-ability perspective. What say you all???

 

[John mc c]

I'm working on a 1.2519 gyuto at about 64 HRC
I can't believe how easy it is on the stones to sharpen
No compromises with the right steels

 

[Cushing H.]

Those ribed steels aren’t really sharpening the blade. They realign the blade.

Yeah I know - perhaps I should not have said "sharpen" - what you are really doing with a steel is straightening the edge and adding some micro serrations. But the end effect is renewed performance - the difference between slicing into a tomato skin, versus not doing so (again, something of a simplification). when I am in the middle of doing food prep - I just want to get the stuff cut - will worry later about the details of edge geometry

Its a more complex subject than simplifying
hardness values as the exact reason why something is better or worse

Yeah again I know - I used the phrase "advanced" steels to try to represent this - but my suspicion is that regardless of the underlying microstructure (which IS important), a harder blade will be more likely to chip (rather than being "mushed" back into performance. so again "hardness" is an incomplete stand-in for a much more complicated discussion - but I am thinking the basic point still holds?

I'm working on a 1.2519 gyuto at about 64 HRC
I can't believe how easy it is on the stones to sharpen

Unfortunately, if I am in the middle of food prep, as I said before, I just need to get the chopping and slicing done. I have stopped food prep to break out a stone, and frankly it is a PITA. The steel is 15 seconds, and you are then back in to chopping and slicing.

I recognize the ribbed steel is NOT a substitute for sharpening - with the right blade steel, it is nothing more than a temporary stop-gap to keep you chopping and slicing right "now" BUT it does keep you working on the food prep ... with the real sharpening on a stone or belt taking place at a different time. ....

 

[John mc c]

With the right steel you shouldn't have to stop in the middle of food prep to steel,your edge will last

 

[Cushing H.]

With the right steel you shouldn't have to stop in the middle of food prep to steel,your edge will last

I suspected someone would say that ... however That presumes I sharpened it ahead of time or that I somehow Have a schedule for keeping working knives sharp ... which due to practicalities is not the case. Over the course of days or weeks of use, I detect a blade is in need of attention when I use it ... which again hits that “Im In the middle of food prep” thing...

 

[DeadboxHero]

I feel this thread doesn't have much to due with hardness and steel, I feel you just need to throw your metal sharpening steel away and get into ceramic honing rods and strops so you can maintain your knives better rather than bottoming the knives out to fit the honing steel.

Just curious,
Do you make knives?

I suspected someone would say that ... however That presumes I sharpened it ahead of time or that I somehow Have a schedule for keeping working knives sharp ... which due to practicalities is not the case. Over the course of days or weeks of use, I detect a blade is in need of attention when I use it ... which again hits that “Im In the middle of food prep” thing...

 

[tkroenlein]

I don't find hardness really a factor in sharpening any knife on a grinder. Some steels develop a burr that is tougher to deal with.

I don't know much about chef knives. I don't have any primo chef knives and I don't make them. But I know any steel is harder than a carrot or the wood it's cut on. So thin, hard edges in a wear steel resistant should last a long time.

There is more validity to your question for something like butcher knives, where edges are steeled frequently. A high hardness, wear resistant steel maybe wouldn't be the best choice there.

 

[Willie71]

I only have to sharpen daily use knives about every 6 months at most, using z-wear, for example. Harder steel supports a finer edge without rolling. Too soft, and you lose fine edge stability, I have O1 knives at Rc60 that I find way too soft in the kitchen. For carbon steel knives, a loaded strop in the cutlery drawer will bring mild wear back to sharp quickly.

 

[3fifty7]

So which knife did your friend choose and did he give any reasoning for said choice?

 

[jake pogg]

There is more validity to your question for something like butcher knives, where edges are steeled frequently. A high hardness, wear resistant steel maybe wouldn't be the best choice there.

If i may ask,how come you differentiate so between chef and butcher knives?

The reason i ask is that i do a Lot of cutting up of fish...In very harsh conditions,every cut through the skin,And against a surface of a board...Moreover,most of the fish are out of a gill-net set in a really silty river,where in addition to everything there's a % of basaltic glacial silt stuck to the outside of skin...
So things being discussed here are of a vital importance to me...I'm having a very tough time keeping my knives sharp(shaving-sharp is plenty,but very difficult to maintain on production SS processing knives such as Dexter or Victorinox).

 

[Cushing H.]

If i may ask,how come you differentiate so between chef and butcher knives?

I was going to ask the same thing. I dont really see a difference (if your are thinking about bones ... most butchers I see use bandsaws to make their way through bones ... otherwise the knives are just cutting through meat....)

 

[Cushing H.]

I don't have any primo chef knives and I don't make them. But I know any steel is harder than a carrot or the wood it's cut on. So thin, hard edges in a wear steel resistant should last a long time.

First of all, most of the "primo" chefs knives sold commercially are (at least in my opinion) lousy (bolster gets in the way of sharpening, bevel too thick BTE, steel uncertain in terms of hardness and microstructure, etc). despite the question I am raising here, if you want to experience a good cooking knife, get one from one of the Makers on this forum . Beyond that, unfortunately, even the best wood cutting boards WILL dull a knife ( plastic are much much worse :-( ). So ... a sharp knife pushed repeatedly against a wood cutting board WILL dull surprisingly fast.

so you can maintain your knives better rather than bottoming the knives out to fit the honing steel.

DeadboxHero - response to you: I keep my knives EXTREMELY sharp. Anyone visiting my home has never had any complaints about my knives. Professional chefs who have experienced them basically say something like "Oh. My. God.". I am talking about even the slightest hint whether they easily cut through the skin of a tomato. If they show any hesitancy to do so, they are not sharp enough. If they dont ... I want that corrected NOW.

 

[Cushing H.]

....rather than bottoming the knives out to fit the honing steel.

I am not talking about "bottoming out" the the steel. Between you and me, I LOVE the newer steels coming out. I am just trying to raise the question the assumption that taking them (or any steel) to the highest rockwell is best, when given the needs of the user. for example, I am talking here about the dulling that occurs with a cooking knife exposed to a cutting board. I think I would have a VERY different statement with, for example, a skinner, that is only exposed to meat, and does not have do deal with dulling from contacting a cutting board....

 

[Cushing H.]

So which knife did your friend choose and did he give any reasoning for said choice?

lol, lol, lol. He actually chose the VG10 blade (despite a lifetime of using blades like the first one). that said ... he was at times actually rather rough with the thing, and it was noticeably more dull after he finished. that is ok, he is a very good friend. . I might need to make him one of the VTG10 blades ... but he is used to sharpening blades with softer steel ... so he may reject the thing saying something like "I cant get this darned thing sharp"!!!! (this is part of the mental exercise that led me to post this thread in the first place.

 

[Cushing H.]

I have O1 knives at Rc60 that I find way too soft in the kitchen. For carbon steel knives, a loaded strop in the cutlery drawer will bring mild wear back to sharp quickly.

but if you have that strop ... and in 30-60 seconds you are back in business prepping food ... is that not a good place to be???

 

[Cushing H.]

Moreover,most of the fish are out of a gill-net set in a really silty river,where in addition to everything there's a % of basaltic glacial silt stuck to the outside of skin...

yuck ... that glacial silt is ... nasty :-( . though cant help but think it emphasizes the point of the benefit of being able to sharpen quickly at the point of use??? and .... (sorry about this)... does driving to a higher hardness interfere with that????

 

[jake pogg]

yuck ... that glacial silt is ... nasty :-( . though cant help but think it emphasizes the point of the benefit of being able to sharpen quickly at the point of use??? and .... (sorry about this)... does driving to a higher hardness interfere with that????

Yessir,indeed it seems like it would...

Your (aptly-named)topic caught my eye because it seems to be an ancient quandary...Many old-school butchers(and chefs too though i know too few of these)have come to that very decision,soft/quickly restorable is better...

I'm a metalworker in my spare time(not a knifemaker),but not too knowledgeble in finer metallurgy...I Do try to wrap my pea-brain around the relative size of carbides and all that,but inevitably end up getting lost in this perennial balancing-act,Traditional (low-alloy Carbon ) vs assorted Unobtainium-type alloys....(of which there seems to be more and more every year

 

[DeadboxHero]

This is Spicy White Steel, 26C3.
at 66rc.




This knife has a fine array of iron carbides with very fine grain with a good HT, very high edge stability steel.

There are many benefits to higher hardness as seen in the video.

1. Burr falls off. This translates to the knife getting sharper rather than the gummy stubborn burr on softer steels.

2. Thinner Geometry can be supported.
The higher yield strength in the microstructure means we have higher resliance, a softer steel would deform permanently easier if this thin. Harder blade means more from wear resistance, lower edge angle, thinner behind the edge Geometry and superior cutting ability.

3. No damage from cutting board.
In the video I demonstrate cutting a metal can, this is more abuse than any proper wood or soft plastic cutting board. At this Geometry, if the steel was softer it would have stopped cutting the can due to plastic deformation from lower strength. The deformation would be so bad a sharpening steel would not have saved it.


4. Use a ceramic rod. I was able to restore the harder steel with a ceramic honing rod to same effect your argument is for using a softer steel.

I am not talking about "bottoming out" the the steel. Between you and me, I LOVE the newer steels coming out. I am just trying to raise the question the assumption that taking them (or any steel) to the highest rockwell is best, when given the needs of the user. for example, I am talking here about the dulling that occurs with a cooking knife exposed to a cutting board. I think I would have a VERY different statement with, for example, a skinner, that is only exposed to meat, and does not have do deal with dulling from contacting a cutting board....