Knife hardness and kitchen/utility knives

[evert67]

Yesterday I sharpened two knifes (using the Spyderco Sharpmaker) for the first time in my life. The first one was a cheap no-brand kitchen knife, the second one a Global kitchen knife. The second one was noticeably harder to sharpen (probably because the no-brand had quite a soft steel).

In the kitchen world, Global are apparently known for using a very hard steel. Yet, when I looked it up, they use a steel called Cromovo (anyone heard of it?) with an HRC of 54-56. Again apparently, other well-known knife makers, particularly the German ones (Zwilling, Henckels, …) use softer steels.

Can anyone comment on this? And why is it that utility knives I see discussed here often have a much higher HRC?

 

[Noctis3880]

Yesterday I sharpened two knifes (using the Spyderco Sharpmaker) for the first time in my life. The first one was a cheap no-brand kitchen knife, the second one a Global kitchen knife. The second one was noticeably harder to sharpen (probably because the no-brand had quite a soft steel).

In the kitchen world, Global are apparently known for using a very hard steel. Yet, when I looked it up, they use a steel called Cromovo (anyone heard of it?) with an HRC of 54-56. Again apparently, other well-known knife makers, particularly the German ones (Zwilling, Henckels, …) use softer steels.

Can anyone comment on this? And why is it that utility knives I see discussed here often have a much higher HRC?

Uh, I have to laugh at that one. The Global Chef knife I'm looking at has Rc 56-58. My CRK Umnumzaan in S30V, which I consider to be underhardened has RC 58-59. I have a Tojiro Flash Paring Knife at Rc 62 and a Miyabi 7000MC Chef's Knife at Rc 66. It's certainly harder than German knives, but it pales in comparison to Japanese knives and even a lot of folding knives are harder than that.

One member has a review of Global knives and the mentioned steel here:
http://zknives.com/knives/kitchen/ktknv/global/glogf33.shtml

Utility knives are harder because 1) the steel used is generally capable of being hardened to higher Rockwell points and 2) the blade doesn't need to be that tough given that it is shorter and won't be subject to as much stress.

Also, I want to point out that the Sharpmaker while good for touching up a knife is absolutely terrible at actually sharpening a dull knife. IIRC the medium ceramic rods are 15 microns in grit size and would take a few hours to even raise a burr on a dull edge. If you were to buy some coarse grit(60-120 grit) sandpaper and clamp them to the rods with a binder clip, I would expect sharpening would only take a few minutes.

As for the steel, the reviewer mentions that VG-10 would be a better alternative. And I for one would not use such a soft steel unless I was cutting bone. And even then something with 18% chromium would not be recommended for that. It's mostly why I avoid German knives in favor of the super hard Japanese knives. That, and since I can sharpen even CPM-S125V without trouble, I figure I'd just go for the hardest steel I could get my hands on short of a ceramic blade:thumbup:.

 

[Cynic2701]

Can anyone comment on this? And why is it that utility knives I see discussed here often have a much higher HRC?

Like Noctis said, mid 50's Rockwell isn't really all that hard compared to the "norm" that we knife knuts generally deal with.

 

[evert67]

Like Noctis said, mid 50's Rockwell isn't really all that hard compared to the "norm" that we knife knuts generally deal with.

So why? It appears Global are among the best valued kitchen knife companies in the world, but according to "our" norms they are not that special. What is the difference between the utility+ knife world and the kitchen knife world?

 

[OrdnanceBubbaUSMC]

If you read the link it mentions the steel having 18% chromium, it probably means that it can't go too hard without being brittle but has the ability to sit in a sink for awhile. Some manufacturers choose that over edge retention. Victorinox swiss army knives are really soft with low edge retention but you have to really try to make them rust or chip. I wouldn't care about kitchen knives with super edge holding unless I was a pro chef.

 

[Cynic2701]

So why? It appears Global are among the best valued kitchen knife companies in the world, but according to "our" norms they are not that special. What is the difference between the utility+ knife world and the kitchen knife world?

It's pretty simple: think about their end users or their "audience." Yes, professional chefs use their knives day in an day out, and probably are actually using a knife more frequently than many of the members here.

Yet, the environment they operate in is much different.

Different steels, and even different HRC values all have their place and usefulness in different applications. Pocket knives are generally used to cut tougher, and more abrasive material than what is most frequently encountered in the kitchen--there aren't too many chefs who use their chef's knife to cut down cardboard, or to cut carpeting/ceiling tiles or the like. Pocket knives also usually have a much shorter blade--the longer the blade, the higher the stresses that the knife is put under. Therefore, it would be more desirable for the chef to have a blade with a softer steel, resistant to corrosion, which can stand up to the abuses of hacking through bone, or accidentally hitting those ubiquitous stainless steel surfaces in commercial kitchens.

More specialized knives require more specialized care. The best knives for cutting fish (especially for high-end sushi and sashimi) are chisel ground, and are typically made of carbon steel--they can utilize a high hardness and a very acute edge because the end user understands that they won't be using it to hack apart ribs.

The same thing with the more popular pocket knife steels occurs as with kitchen knives. The big companies like Buck use 420HC in the mid 50's HRC (IIRC) because most users aren't going to be as careful with their knives as we knife knuts are. To a knife knut it may be perfectly acceptable to trade in toughness for edge retention--ZDP-189 at 66+ HRC's can be ground down to a very acute edge, but there will be the danger of chipping or rolling of the edge if the user attempts to cut metal or cement.

 

[knarfeng]

Yesterday I sharpened two knifes (using the Spyderco Sharpmaker) for the first time in my life. The first one was a cheap no-brand kitchen knife, the second one a Global kitchen knife. The second one was noticeably harder to sharpen (probably because the no-brand had quite a soft steel).

In the kitchen world, Global are apparently known for using a very hard steel. Yet, when I looked it up, they use a steel called Cromovo (anyone heard of it?) with an HRC of 54-56. Again apparently, other well-known knife makers, particularly the German ones (Zwilling, Henckels, &#8230 use softer steels.

Can anyone comment on this? And why is it that utility knives I see discussed here often have a much higher HRC?

I doubt any Henkels or other name brand kitchen knife has softer steel than that. 54-56HRC is pretty common for kitchen knives. Cheapie no-name knives may be softer. As others have said, 54-56 roughly the bottom of the hardness range for pocket knives.

The amount of difficulty in sharpening a knife on the Sharpmaker is not actually an indication of relative hardness because there are other factors that play a part in that. Starting sharpness, edge angles, and overall thickness of the blade also enter into determining how hard it is to sharpen a blade.