How would you "quantify" the actual difference between ~60 vs ~62 HRC?

[bookgeek97]

So kind of a dumb question here:

How would you describe the practical differences -- all else generally being the same-- between a knife that's 60HRC vs 62HRC? (Note, i'm deliberately choosing this HRC range to avoid comparing german knives to j-knives, or comparing VG10 to say some super high-end 64hrc PM steel.)

Of course, it goes without being said that a harder knife might be able to obtain a more aggressive/acute angle, trade toughness for hardness, etc. but what else do you notice at a practical-level? For example: In your experience, would a 62 HRC knife really incur noticeably less frequent touch-ups than a 60 HRC knife? How less frequent? Would non-enthusiasts be even able to detect a difference?

Super curious to hear your thoughts, and if you're coming from a home-cook perspective or a professional kitchen Thank you!

 

[HRC_64]

i'd suggest you search for discussions about "lasers" and their edge retention.
in other steels and construction/grinds, you may not need as much emphasis on hardness
to achieve or maintain edge stability...as other considerations come into play.

 

[42537703]

A knife with high hardness doesn't mean that it has a good treatment. A simple high carbon steel like 1095 heat treated at 62hrc might have lower edge retention compared to a high wear resistant steel like M4 which is heat treated at 57hrc.

Walter Sorrells has made a video on YouTube explaining the hardness. America's Test Kitchen has compared the edge retention between a zwilling Kramer 51200 chef knife (60ish Hrc) to a victorinox chef knife (57ish Hrc). The victorinox hold up petty well against the zwilling Kramer. Finally, Going custom also on YouTube has a video about Steel testing. He tested several different steels with different heat treatment schedules. The results in general shown that the steels that are properly treated performed better in edge retention and toughness in the same with a bad heat treatment but with high hardness.

 

[K813zra]

Everyone always says there is more to it than just hrc but I am not into the science of these things. I can say that most of my white # 2 lasers are around 60hrc and all have very similar edge retention and dulling curves. In my home kitchen they will stay usable sharp for a long time but they lose the ability to freely slice a tomato after about 9-12 meal preps and need a light refresh on a loaded strop. My KS which is similar in thickness at and behind the edge is said to be slightly harder in the 61-62 hrc range and for me it shows. I get about 15-18 meal preps before the knife absolutely requires a stropping for the same purpose.

Now, dissimilar knives with the same steel also show different periods of edge retention. My Masakage Yuki, said to be 62-64 hrc, is one of the best white #2 knives I have ever used for edge retention but not so much above the KS that it blows it away. About 18-20 meal preps.

Of course all of this is relative to the way I use a knife in my kitchen on my board etc. What I can tell you is that I eat a lot of potatoes, carrots, celery, turnips, parsnips, chard, lettuce, cabbage, mushrooms onions and garlic. That is mostly what my knives seen on a weekly basis and probably about 15 minutes of prep meal per day. The average day is 2-3 meal preps.

Beyond that, when comparing other steel it is not so much the edge retention itself that matters but how the edge dulls. Example, when white steel dulls it loses bite very quickly but reminds usable dull for a very long time. Sharper than the average homes knife, for sure. 19c27 for example holds that bite for a long time and then goes dead dull right now! It loses everything it has all at once, ime. Maybe that is an exaggeration but my point is that it does not dull the same way as white #2 or even 13c26. I suppose things like this play a role in why people say it has to do with more than just the hrc.

Going ever further you will hear people talk about steel being tough and having good wear resistance and or whatever properties are needed to withstand impact from chopping yet retain a good edge. That vs more simplistic steel that will not take to such 'abuse' well. Again, I am sure this also plays a big factor.

But if you want to stick with generalities. A direct from Japan laser (pick your flavor) at 57-58 hrc should have lesser edge retention than one of the higher hardness models at 60-61 that you get from one of the approved vendors. How much of a difference will you notice? I don't know, an hour or two on the board? Maybe three? Good question. But if you strop after or before every meal prep you would not likely realize a difference over the long run.

As for edge acuteness. I have been able to get some very simple and very soft carbon extremely sharp, it just does not hold it as well. But me, compared to most here, I am but a fledgling so take that with a grain of salt. I have not noticed a huge difference in edge taking between various treats on the same steel so much as I have on different types of steel. Simple carbon seems to take a better edge, for me, followed by PM and tool steels and finally stainless with some exceptions such as 13c26.

Now, I have just had my first cup of coffee so forgive me if I just wrote down an ton of gibberish.

 

[bookgeek97]

Beyond that, when comparing other steel it is not so much the edge retention itself that matters but how the edge dulls. Example, when white steel dulls it loses bite very quickly but reminds usable dull for a very long time. Sharper than the average homes knife, for sure. 19c27 for example holds that bite for a long time and then goes dead dull right now! It loses everything it has all at once, ime. Maybe that is an exaggeration but my point is that it does not dull the same way as white #2 or even 13c26. I suppose things like this play a role in why people say it has to do with more than just the hrc.

Kit, thanks for sharing your thoughts (and not gibberish at all-- was picking up what you were putting down) Super helpful.

A knife with high hardness doesn't mean that it has a good treatment. A simple high carbon steel like 1095 heat treated at 62hrc might have lower edge retention compared to a high wear resistant steel like M4 which is heat treated at 57hrc.

Walter Sorrells has made a video on YouTube explaining the hardness. America's Test Kitchen has compared the edge retention between a zwilling Kramer 51200 chef knife (60ish Hrc) to a victorinox chef knife (57ish Hrc). The victorinox hold up petty well against the zwilling Kramer. Finally, Going custom also on YouTube has a video about Steel testing. He tested several different steels with different heat treatment schedules. The results in general shown that the steels that are properly treated performed better in edge retention and toughness in the same with a bad heat treatment but with high hardness.

I'll be sure to check out that video-- thanks!

 

[dough]

Your question isn’t dumb and you got thoughtful replies. I just think as a user of knives the difference between 60 and 62 is basically not quantifiable. I’m sure Larrin could give you an incredibly accurate answer... maybe a maker will chime in what it means to them. Since knives love car analogies I think its like horsepower. 200 horsepower is certainly a useful measure but it’s hard to say what it means on its own.

 

[supersayan3]

You can tell the difference in hardness between two knives.
If one is 60 and the other 62, if you will not be able to spot the difference from the beginning, after some practice with both knives you will be able to tell.

Two knives from the same steel, both by makers that do good heat treatment, the one with higher HRC will have better edge retention

 

[Barmoley]

The knives would have to be exactly the same with the only difference being hardness. Otherwise you wouldn’t know what causes the difference you experience. Also, particular hardness is usually a target, so there could be a pretty significant variation even among individual knives from the same manufacturer. Moreover, many manufacturers give a range 61-62, 57-59, etc. In addition HRC scale is not linear it is exponential, meaning there is a larger jump between 64 and 65 than there is between 58 and 59, even though in the ranges that we care about we can assume it is almost linear. All of this is to say that to quantify the difference between 60 and 62 would be very difficult in a knife. There is definitely a difference, but the HRC number is such a minor attribute of knife's performance that it probably doesn’t mean a whole lot. There is about 3.2% difference in tenstile strength for each point in the low 60s range, for whatever that is worth.

 

[HRC_64]

The simple example than many
people don't understand the difference
in two different things, is just another form
of 'argument from ignorance'

 

[tsuriru]

(~62)- (~60)= (~2)

 

[Wdestate]

(~62)- (~60)= (~2)

lol

 

[42537703]

Gough custom not going custom, typo. He makes very nice outdoor knives in A2 Steel.

 

[LifeByA1000Cuts]

"There is about 3.2% difference in tenstile strength for each point"

Can that be understood as "if you happen to use the knife in an style that creates exactly the peak load on the edge which would be 99.8% of what 61HRC can take but 103% of what 60HRC can take, the 60HRC knife will suffer some plastic deformation making it duller while the 61HRC knife will not care as much by far"?

 

[HRC_64]

"There is about 3.2% difference in tenstile strength for each point"

Can that be understood as...

The point that really matters is that 57 vs 59 is a 2pt difference,
but a file will cut (=dull/sharpen) one a hell of a lot easier
than the other.

When you apply the file (will/wont) cut analogy
to what the cutting board will do to your edge (slower--over time),
you will see that 2pts is not trivial.

And that many, many data points
support the hypothesis that 2pts
is not immaterial or indistinguishable.

 

[inferno]

So kind of a dumb question here:

How would you describe the practical differences -- all else generally being the same-- between a knife that's 60HRC vs 62HRC? (Note, i'm deliberately choosing this HRC range to avoid comparing german knives to j-knives, or comparing VG10 to say some super high-end 64hrc PM steel.)

Of course, it goes without being said that a harder knife might be able to obtain a more aggressive/acute angle, trade toughness for hardness, etc. but what else do you notice at a practical-level? For example: In your experience, would a 62 HRC knife really incur noticeably less frequent touch-ups than a 60 HRC knife? How less frequent? Would non-enthusiasts be even able to detect a difference?

Super curious to hear your thoughts, and if you're coming from a home-cook perspective or a professional kitchen Thank you!

62 chips/60 rolls??

maybe.

but from my perspective there are no 1 to 1 comparisons.

since if you harden steel x to 60 and steel x to 62 one of them is gonna be suboptimal for the application compared to the other one.

and if you compare steel y at 60 to steel x at 62 it could be an enormous difference. you really cant compare them side by side. since it 2 different steels.

Its better to compare steels at their very peak, best toughness and "workable" hrc. some steels perform better at 58 and some at 62. but almost always a 58hrc steel will be less chippy. talking SS here.

I say: either you harden to max potential or you get a tougher lower hrc steel to begin with. there is no reason to harden an 62hrc steel to 58 when you can get some cheap ass steel and just harden it to max, 58, and it will be tougher and better than the 62 at 58. IMO that is. toughness is king.

 

[K813zra]

62 chips/60 rolls??

maybe.

but from my perspective there are no 1 to 1 comparisons.

since if you harden steel x to 60 and steel x to 62 one of them is gonna be suboptimal for the application compared to the other one.

and if you compare steel y at 60 to steel x at 62 it could be an enormous difference. you really cant compare them side by side. since it 2 different steels.

Its better to compare steels at their very peak, best toughness and "workable" hrc. some steels perform better at 58 and some at 62. but almost always a 58hrc steel will be less chippy. talking SS here.

I say: either you harden to max potential or you get a tougher lower hrc steel to begin with. there is no reason to harden an 62hrc steel to 58 when you can get some cheap ass steel and just harden it to max, 58, and it will be tougher and better than the 62 at 58. IMO that is. toughness is king.

But it is done. I have seen white # 2 range from 57 to 64 (target). What it actually is, your guess is as good as mine. I have white at 57-59 (stated) and it rolls. I have white at 61-63 (stated) and it chips. Has that actually anything to do with hardness, again, I have no idea. It could be how the steel itself was treated, I have no clue.

 

[inferno]

these are very simple steels. they dont respond to cryo. so your hardening at 850c or so, then quench, then temper. where you gonna temper??
150C gives max hrc hardness at the cost of ductility and overall toughness. 500C gives you lowest possible hrc hardness and lets just "say" it gives us max toughness.

so both of these extremes sucks ass. what to do? middle of the road?

no!

read a fukking book! yeah no joke
read a fukking book. about steel and their heat treatment.

I had lots of questions starting out in like 2000 or so and i had lots of very technical questions that i wanted answered. and no one could answer them.
then I got a good tip from a member on bladeforums. go to a library and borrow books. then read them. then you will be at leat 90% as smart as the real metallurgists.

So i did that.

And now pretty much everything that every blader maker does seems like mumbo jumbo to me.
no wonder sh!t suck ass!

HT is everything,

if if your target hrc is above what "your" steel can deliver. then guess what, you go up to another grade instead of hardening to the moon with the **** you got. and if you dont understand that maybe you should be making non knife products. instead

very few steels perform best at 64hrc. but quite a lot perform great at 60 hrc. yet many makers want to sell 64hrc knives. and they will chip out like a motherfukker.
i wonder why.

you really need to read some books. astm whatever books.

One good example is mora of sweden, they harden their 1095 blades to like 58-59 hrc. and this is too low to be good. for this steel. but its cheap, and consitet. you can do it all week long. but usually its higher harness at the cost of toughness. because there is always a cost.

 

[panda]

i dont know about the numbers, but i can definitely sense differences in steels through use. for example out of my white steel knives masamoto ks is too soft, hinoura is too hard, but my yoshikane is in the sweet spot. masamoto is easiest to sharpen, but the hinoura takes the best edge. trade offs.. i like it in the middle.

 

[supersayan3]

Which Hinoura?

 

[tsuriru]

these are very simple steels. they dont respond to cryo. so your hardening at 850c or so, then quench, then temper. where you gonna temper??
150C gives max hrc hardness at the cost of ductility and overall toughness. 500C gives you lowest possible hrc hardness and lets just "say" it gives us max toughness.

so both of these extremes sucks ass. what to do? middle of the road?

no!

read a fukking book! yeah no joke
read a fukking book. about steel and their heat treatment.

I had lots of questions starting out in like 2000 or so and i had lots of very technical questions that i wanted answered. and no one could answer them.
then I got a good tip from a member on bladeforums. go to a library and borrow books. then read them. then you will be at leat 90% as smart as the real metallurgists.

So i did that.

And now pretty much everything that every blader maker does seems like mumbo jumbo to me.
no wonder sh!t suck ass!

HT is everything,

if if your target hrc is above what "your" steel can deliver. then guess what, you go up to another grade instead of hardening to the moon with the **** you got. and if you dont understand that maybe you should be making non knife products. instead

very few steels perform best at 64hrc. but quite a lot perform great at 60 hrc. yet many makers want to sell 64hrc knives. and they will chip out like a motherfukker.
i wonder why.

you really need to read some books. astm whatever books.

One good example is mora of sweden, they harden their 1095 blades to like 58-59 hrc. and this is too low to be good. for this steel. but its cheap, and consitet. you can do it all week long. but usually its higher harness at the cost of toughness. because there is always a cost.

Hey Inferno, do you suffer from tourette syndrome in it's textutal form? Because if so, I guess it's a legitimate medical disability, and I am perfectly willing to accept it. Short of that, it sounds like you feel it is necessary to use nasty language in order to make a point. Do you think it gets your point across better? Im not judging or anything.... everyone has their own style I guess. Just so you know - you lost me way back at that ass sucking part at the top.
:blahblah:

 

[Nemo]

Hey Inferno, do you suffer from tourette syndrome in it's textutal form? Because if so, I guess it's a legitimate medical disability, and I am perfectly willing to accept it. Short of that, it sounds like you feel it is necessary to use nasty language in order to make a point. Do you think it gets your point across better? Im not judging or anything.... everyone has their own style I guess. Just so you know - you lost me way back at that ass sucking part at the top.
:blahblah:

Well put.

 

[Benuser]

+1

 

[gaijin]

Whoops. Sorry. Wrong place. Move along, nothging to see here.

 

[panda]

first of all, LMAO @ tsuriru's comment, hahahahaha, sarcasm on point!! :rofl2::lol2:

Which Hinoura?

http://bernal-cutlery.shoplightspeed.com/mutsumi-hinoura-shirogami-240mm-wa-gyuto.html

 

[supersayan3]

Thank you for the link

 

[42537703]

I do read metallurgy papers and books about heat treatment and steels. But what I found is that most of the information about metallurgy is not so much knife related. I think it is overkill for most of us in this forum.

If you are really in to testing. I found tests like rope cutting is more practical. Make sure the test is standardised and repeatable like using the same thickness and rope, sharpening the edge at a fix angle and same grit, and using same type of cutting (push cut or rocking cut) over the same section of the blade, etc. Or just simply go to work and see how long the knife can hold the edge till it is not longer hair shaving sharp or paper cutting sharp.

 

[LifeByA1000Cuts]

I think inferno's post would make an excellent script for a "cooking hostile" episode on knife maintenance...

I guess the roll vs chip thing would be about the yield strength to breaking strength ratio you get at a certain hardness?

 

[HRC_64]

I guess the roll vs chip thing would be about the yield strength to breaking strength ratio you get at a certain hardness?

basically it's the definition of brittle you are talking about.

where brittle (facture) is for each knife of course is not at the same HRC.
HT comes into play, underlyingalloy comes into play,
and so does actual edge mass/TBD etc

all (variables) of which can prevent brittle fracture,
should they be altered with such intent.

Of course, at the limite of all of the above,
there is also possible there is only one
variable left to alter...HRC

But just for fun, keep in mind,
HRC is matrix hardness, not
actual edge hardness...which is carbides
and the carbides are easily harder than
the matrix in high-alloy steels.

just in the same way a stone
is hard or soft but not really
the hardness/softness is a measure
of cutting of the stone, same is true

for steels. you can have edges with
hard carbides on the edge, (tough)
but the overal matrix is softer than the carbides.

ie, HRC 57 tool steel full of
HRC 65-75 carbides on the edge

this will be a tough and possibly
hard-edge at the same time
as not being as prone to brittle fracture
as a pure steel honyaki at hrc 65
or similar.

if that makes sense.

edit: sorry for long post :rofl:

 

[LifeByA1000Cuts]

"HRC is matrix hardness, not actual edge hardness."

Sure? I thought the "vanadium carbide in soft toffee" method was what gave most european stainless any respectable HRC at all?

 

[Yet-Another-Dave]

"HRC is matrix hardness, not actual edge hardness."

Sure? I thought the "vanadium carbide in soft toffee" method was what gave most european stainless any respectable HRC at all?

I'm sure the carbides affect the result, but I'm not sure it's very much. Standard measurement is a calibrated system, that is basically a press with a stylus (of specified shape & hardness), and you punch a divot in the sample piece. The softer the metal the bigger the divot. (It's literally been more than 40 years since I used such a tester. Details are fuzzy and might be slightly wrong. E.g. I don't remember if an impact or gradual compression force drives the stylus.)

At any rate, my point is the stylus point is much larger than individual carbides.