Case CV blade hardness and comment on measuring traditional knives

knarfeng

knarfeng

senex morosus moderator
Staff member
Super Mod
Moderator
Joined
Jul 30, 2006
Messages
45,333
Ok folks. This is a bit off topic. But we do tend to stray off the main path a bit in Traditional, so I will ask you to bear with me. Y'all can always just skip on to the next post if need be.

Recently I purchased two yeller Case knives with CV blades. One is a three spring stockman. The other, a two spring yeller sowbelly. I've mentioned them elsewhere.

The other day I measured the Rockwell hardness of one blade from each. The results were:
Sowbelly: 41
Stockman:55.6

Now, I've carried and used these knives enough to know that the edge retentions are about the same. Not phenomenal, but adequate. How can that be? you ask.

The answer lies both in the measurement technique and the methods of making a traditional knife.

First the measurement. To measure the Rockwell hardness, you need a sample which is flat with top and bottom parallel to one another. On most traditional knives, that means you have to measure the tang.

Now the knife making part. To fit three blades onto two springs, normally the blades have to be bent or to put it in cutler terms, "crinked". To do that, you have to soften the tang.

The sowbelly has three blades on two springs. The blades are most definitely crinked. Therefore, the tangs have to be softened. So the 41HRC I measured applies to the tang, not the blade.

The stockman has three blades on three springs. The blades on my stockman are straight. Therefore, the tangs do not have to be softened, and on mine, they obviously were not. The actual blade hardness is 55.6HRC.

In the past I have measured the hardness of several different traditionals:
Case CV Sodbuster__54__straight blade. tang not softened
Camillus stockman__42__crinked blades. tang softened
Camillus stockman__42__crinked blades. tang softened.

So. My conclusions are this:

  1. If you are measuring a hardness in the low 40's on a traditional knife, you may be measuring a tang that was softened
  2. Case CV blades are hardened to about 55HRC. This is a fairly common traditional hardness range, though a little softer than I would like. It has been reported that GEC claims a hardness of 58 for its 1095 blades. And it was reported that Camillus used to harden its 0170-6C blades also to about 58.
 
OOPS! I forgot about that one.
 
Frank,

Interesting post with good information. I did have a few questions. On the sowbelly and Camillus stockman are the master blades crinked also? I would guess not but you never know. If not, does the tang still measure at the lower RC?

I did want to mention that its fair to say that handmade slipjoints makers crink before heat treat and end up with a tang that is the same Rockwell hardness as the rest of the blade. Of course the sequence of operations will be different on a production scale. I also wonder if the company mark is stamped post heat treat on a softened tang?
 
Interesting... I am also wondering about any difference between the master blade and sheepfoot/spey on the sowbelly.
 
ken erickson said:
I did want to mention that its fair to say that handmade slipjoints makers crink before heat treat and end up with a tang that is the same Rockwell hardness as the rest of the blade. Of course the sequence of operations will be different on a production scale. I also wonder if the company mark is stamped post heat treat on a softened tang?
Click to expand...

If I understand what I learned at GEC correctly, they send their blades out for heat treat, then soften the tangs after the blades are returned (hardened) and before they stamp the tangs.

Which of course signifies nothing as far as other manufacturers' processes, but I do remember that for GEC the tang-softening was a separate, post-heat-treat step.

~ P.
 
Ken, the blades of the both Camillus stockman knives plus those of the sowbelly are crinked. Those are all three blade knives with two springs.
The Case 3347 stockman I measured has three straight blades and three springs.

Buck stockman models have three straight blades on three springs. They do not crink the blades, nor do they soften the tangs (I asked in the Buck Forum and Chuck Buck said they do not). The tangs are imprinted. I have measured several of them at 59HRC. Their stated hardness range for 420HC is 57-59, so I am not getting any impact from imprinting, at least on Buck knives.

I measured the sheepsfoot on the Case Sowbelly and the Case stockman. Both had imprinting on the other side of the sheepsfoot. (I measured the sheepsfoot blades because they had the biggest tangs. Need a certain amount of room for the Rockwell head.)

Jake, IIRC, on the Camillus knives I measured the main blade because it had the biggest tang. I'm guessing it does not make a difference.

P, Steve Pfeiffer said that Case uses the same sequence as GEC. He said Case heat treats the blades, then runs the tangs through an induction heater with a heat sink clamped above the tang to keep the rest of the blade from softening.
 
knarfeng said:
P, Steve Pfeiffer said that Case uses the same sequence as GEC. He said Case heat treats the blades, then runs the tangs through an induction heater with a heat sink clamped above the tang to keep the rest of the blade from softening.
Click to expand...

Okay, thanks.

P1014223.jpg


Photo courtesy of Johnny Twoshoes, with the equipment area for tang-softening now circled by yours truly. The heat-treated blades go onto the circular disc to the left with their tangs facing the middle, then the whole thing goes into the blue machine for the now-centered tangs to be heated and softened. Which is probably what you just described!

~ P.
 
IIRC, the How it's Made episode which featured Case knives showed this process.

ETA: Yup! Here it is for those who haven't seen it.

[youtube]LyTKaVE8olc[/youtube]
 
knarfeng said:
Ok folks. This is a bit off topic. But we do tend to stray off the main path a bit in Traditional, so I will ask you to bear with me. Y'all can always just skip on to the next post if need be.

Recently I purchased two yeller Case knives with CV blades. One is a three spring stockman. The other, a two spring yeller sowbelly. I've mentioned them elsewhere.

The other day I measured the Rockwell hardness of one blade from each. The results were:
Sowbelly: 41
Stockman:55.6

Now, I've carried and used these knives enough to know that the edge retentions are about the same. Not phenomenal, but adequate. How can that be? you ask.

The answer lies both in the measurement technique and the methods of making a traditional knife.

First the measurement. To measure the Rockwell hardness, you need a sample which is flat with top and bottom parallel to one another. On most traditional knives, that means you have to measure the tang.

Now the knife making part. To fit three blades onto two springs, normally the blades have to be bent or to put it in cutler terms, "crinked". To do that, you have to soften the tang.

The sowbelly has three blades on two springs. The blades are most definitely crinked. Therefore, the tangs have to be softened. So the 41HRC I measured applies to the tang, not the blade.

The stockman has three blades on three springs. The blades on my stockman are straight. Therefore, the tangs do not have to be softened, and on mine, they obviously were not. The actual blade hardness is 55.6HRC.

In the past I have measured the hardness of several different traditionals:
Case CV Sodbuster__54__straight blade. tang not softened
Camillus stockman__42__crinked blades. tang softened
Camillus stockman__42__crinked blades. tang softened.

So. My conclusions are this:

  1. If you are measuring a hardness in the low 40's on a traditional knife, you may be measuring a tang that was softened
  2. Case CV blades are hardened to about 55HRC. This is a fairly common traditional hardness range, though a little softer than I would like. It has been reported that GEC claims a hardness of 58 for its 1095 blades. And it was reported that Camillus used to harden its 0170-6C blades also to about 58.
Click to expand...


I wondered about that. I've asked a co-worker to test hardness on blades for me and he explained the need for parallel surfaces. We have an old tester which drops the ball on to the surface and you look at the mark. We make packaging machinery so our heat treating doesn't need to be too elaborate, just hardening of chain wear parts and the like.
 
I've been surprised and impressed with Case CV, one example, is when I have carved peach pits, which are hard as stone, there is a lot of scraping involved to smooth out sections of the piece, I use my peanut and after I'm done I am always surprised the blades are still razor sharp, no bends, chips, folds of edge. Another Forum member who started carving peach pits has had the same results with Case CV and the way it retained its edge after using in the same manner as I had.
 
Good info, Frank.

Just to add, I've found Case CV from the 80s' forward to be harder than older knives. And some of the softest blades were Case XX, pre 1965.

I also have some old English pocket knife blades that were never used, no stamp or pivot hole. Blades are hard, but tangs are soft.
 
GEC blades are actually 58-59 rockwell. Also, it bothers me that that tang on your stockman wasnt as soft as your sowbelly. Tells me that case might be skipping a step. Softening the tang has more than one purpose. Yes it allows the blades to be bent, if needed, to lay side by side without rubbing. However, softening the tangs also adds a bit of strength. Heres why, when the blade is open and being used all the pressure is being placed on the tang. If the tang is not softened it may be more susceptible to snap or brake because of the hardness. Whereas, a blade that has a softened tang will absorb the force better and if need be will bend slightly.
 
pertinux said:
If I understand what I learned at GEC correctly, they send their blades out for heat treat, then soften the tangs after the blades are returned (hardened) and before they stamp the tangs.

Which of course signifies nothing as far as other manufacturers' processes, but I do remember that for GEC the tang-softening was a separate, post-heat-treat step.

~ P.
Click to expand...

Fab work such as nail marks and tang stamps have to be done before heat treating while the steal is still soft.
 
I would love to know how a steel like CV (or any steel) is heat treated for knives specifically. For our machinery parts the 1095 or O1 is heated and quenched which brings it to the 60's in Rockwell and drawn (annealed) at a lower temp in the oven for various times (there's a chart) to lower it to various Rockwells.

I know something similar is done for hand forged knives and, I guess, in a knife factory.

Then there is stainless... who knows about that.
 
Great post, very informative!:thumbup:

I know that some manufacturers make their blade a bit higher on the RC scale, and in theory that may be better. But I wonder how much the everyday knife user will notice. If working folks used and loved Case in the old days, even with softer steel, it must have worked for them. Numbers are nice, but in the end it always coems down to a subjective personal judgement. Does it work for you. I think in the old days, the working man may have used his knife more for what the kids now call hard use. A slightly softer blade would not have broken as easy as a harder one that may have held an edge better. I recall the Uncle of a friend who was an old times, andhe bought a Buck knife. He broke three blades on that thing, each time sending it back to Buck and getting a new one. IN the end He deemed Buck "not worth a spit on a warm day."

I asked him what he was doing with his knife, and he told me and showed me how he would pry with it. When I commented that it's not a good thing to pry with a knife, his short comment was "Well my old knife would do it!".

He knew what he knew, and that was that. Hs old cheap knife with a soft blade stood up to his abuse.

Carl.
 
Frank,

Thank you also for the info about the heat sink past the tang. I always wondered how they kept it from affecting the blade.

Kevin
 
Two comments.
- Yeah, I actually do notice the difference in hardness in everyday usage between Case and GEC.
- And I remember when I used to use my pocket knife to scrape carbon off spark plugs. Then I'd re-gap them and put them back in the engine. I think, but do not know, that I could use a GEC for that job.
 
You must log in or register to reply here.
Back
Top