RC hardness values

[WhyNot]

I've read in "The Spyderco Story" that "...for quite a while Spyderco catalogues have provided the Rockwell hardness values for each model".
Not anymore. :(
Does anybody know why? :confused:
I think it would be interesting to compare RC numbers for new steels, like ZDP-189, N690Co, etc. with older ones.
Interestingly, AG Russel web site has RC values for almost all Spydercos they sell.
Can anybody provide any additional information?
Your help would be very much appreciated!
Mark.

[psimonl]

I think RC is over rated.

I read on this forum how RC can vary on a single blade like on H-1. On A serrated blade, it goes from 61 to 67 IIRC, depending where you test !!!

And to say that ZDP has a higher value than S30V, but stays sharp longer and is easier to sharp.

There should be a ranking for heat treating!!!

Well, I don't think RC is a reference anymore....

Simon

[HoB]

I believe Sal once mentioned, that uneducated customers got a little carried away with that information. IIRC many customers did not understand the concept of an ideal Rc for a given steel but thought higher is better. But on the forums, Sal has always been very forthcoming with that information, so its definitely not a secret.

[bh49]

I think RC is over rated.

I read on this forum how RC can vary on a single blade like on H-1. On A serrated blade, it goes from 61 to 67 IIRC, depending where you test !!!

And to say that ZDP has a higher value than S30V, but stays sharp longer and is easier to sharp.

There should be a ranking for heat treating!!!

Well, I don't think RC is a reference anymore....

Simon

I disagree with you, absolutely.
Rc is a scale to measure hardness of hard alloys. Hardness is resistance of material to penetration. Higher hardness, material is stronger. If you use harder steel, knife can be sharpen at smaller angle, like 30 or 25 degrees, instead of 40, which can significantly increase performance of the knife. Each steel reaches pick of performance at certain hardness, if hardness too high steel can became too brittle.
With H-1 is totally different story; it is heat treated, I think, not sure to Rc 56-58 and become harder during use. Only cutting edge became harder, because this is the only area, which used.
If steel has high carbon content, it can be harden thru during heat treatment .
In the piece of steel you can see variation of hardness, but it should not be more than 1-2 points.
Steels with low carbon content, in general, can be only case hardened, in mostly up to .020" deep.

[psimonl]

Hello bh49,

What I meant is that you can't judge a steel blade by its Rc value.

In some situation, you want a softer steel (cf. Kitchen) and for other situation, you need a harder one (cf. wood chopping).

It's just that you have to more infos (the way it sharpens, does it brittle, what is its rust resistance...) than just it's Rc value.

Take care,

Simon

[Ookami]

edge geometry and user behaviour are other factors concerning the performance of a knife.

if you have a very acute edge geometry like in a kitchen knife and you go and chop with it, you will see that even the best steel with the best heat treatment won't hold up very long.

hardness/heat treatment is an important factor, but not the important factor.

Ookami
________
Yamaha Grizzly 600 Specifications (http://www.yamaha-tech.com/wiki/Yamaha_Grizzly_600)

[ghostrider]

I remember seeing a post some time ago where Sal explained why they no longer advertise the rockwell hardness of of various blades. It made sense at the time, but I don't remember what or where it was.

[Joyce Laituri]

Rc measurement can be variable. We did include it in our catalog several years ago but found it can vary minutely from batch to batch, can change where/when steel is work hardened, and can be influenced by other processes.

We felt that unless it was precisely consistent on every model all the time, the numbers in the catalog didn't represent absolutely accurate information.

In my mind I like to compare it to horsepower. More doesn't necessarily always mean faster.

Joyce @ Spyderco

[Franco G]

Rc measurement can be variable. We did include it in our catalog several years ago but found it can vary minutely from batch to batch, can change where/when steel is work hardened, and can be influenced by other processes.

We felt that unless it was precisely consistent on every model all the time, the numbers in the catalog didn't represent absolutely accurate information.

In my mind I like to compare it to horsepower. More doesn't necessarily always mean faster.

Joyce @ Spyderco

Rc measurement is a precise job in physics. It can vary minutely from batch to batch, as Joyce said, but should vary minutely - therefore the ranges 58-60, 60-61, etc.
If a company declares Rc 60-62, and gets Rc 57, then, it is a bad company. Why? Because, as a rule, ELU pays more for higher end steel with higher Rc. I wouldn't like to get an expensive CF Millie with BG-42 hardened to 57 Rc, because the advantage of that steel demands higher Rc.
I was surprised to find at the Ritter's Equipped to survive web, that Spyderco's VG-10 blades are Rc 57-60. Somehow, sounds too much dispersed values.
Some knifemakers put Rc value written on blade. I would prefer to have Rc 61 printed on CF Millie instead of quite funny Earth. It would be, IMO, more serious info - although, I admit, without 'Earth' mark somebody may think Spyderco were somewhere on Mars.
If I find Rc 61 printed on blade, I should consider it to be +/- 1, i.e. in the range 60-62.
Work hardened steel - it is just H-1 - - the only one peculiar Nitrogen steel in Spyderco arsenal.
Rc hardness is no way unimportant parameter.

Franco

[bh49]

Hello bh49,

What I meant is that you can't judge a steel blade by its Rc value.

In some situation, you want a softer steel (cf. Kitchen) and for other situation, you need a harder one (cf. wood chopping).

It's just that you have to more infos (the way it sharpens, does it brittle, what is its rust resistance...) than just it's Rc value.

Take care,

Simon

I believe, if knife designed and made by professionals, people, who know what, are they doing, than Rc value can tell a lot. It is possible to heat treat AUS-8 up to lower sixties, but professional would never do this, because steel would lose toughness and became brittle. Usually blade heat-treated not to max Rc, but to reach pick of performance for certain application. S30V blades of BM folders heat-treated to 58-60 Rc and Chris Reeves “Green Beret” S30V blade heat-treated to Rc 55-57, probably toughness is more important than strength. As you said, for different applications you need a blade with different properties.
Mr. Joe Talmadge, who is member of our forum, wrote an excellent “Steel FAQ”, it was posted on several web sites, including BF. I think you will find it very interesting.
http://www.bladeforums.com/forums/showthread.php?t=368828
I hope; I did not offend you. If I did, I am sorry, I did not have such intension. This is not my native tongue.

[d.g.g]

Here's a link about Rockwell testing that may be way overboard for the nontechnical knife owner.

http://www.gordonengland.co.uk/hardness/rockwell.htm

And if you want to get into "materials".

http://www.matweb.com/index.asp?ckck=1

[Tim8557]

In our litigious society that we have evolved (devolved?) to, publishing a finite number like RC could possibly open the doors to the slimeball parasitic lawyers out their who would throw together a Class Action lawsuit. Anybody whoever touched a knife would be allowed to sign up for this legal sweepstakes.

Sal would have to settle to keep from going to a trial in front of the village idiots who seem to generally hate any successful company. The lawyers would keep 98% of the settlement and the "victims" would get a coupon for 20 cents off of their next knife purchase.

Meanwhile the parasites would be looking for the next 19" TV screen that in reality only measures 18.87 inches so they could have another windfall.

Spare me.