BDS 440C vs CPM440V

D

dragon2

Joined
Jul 18, 2001
Messages
87
Here we go with the first post.
A few weeks ago I read a thread asking how
Boye Dendritic Steel compared to CPM 440V,
but there were no replies. So, I grabbed
my Kershaw Random Task and my Boye Prophet
Companion and found some cardboard to cut.
The test took nearly 2 days but the question
was answered to my satisfaction. I won't
give specific numbers of cuts, since the error
is at least +/- 40, but I will say that the
two were very close, and outperformed any other
knife I had put through the same test. The
advantage went to the 440V, predictably enough.

Whoever asked that question, I hope this gives
you some information.
 
I asked that question Dragon.
Thanks for your findings, although u're a little late...
Hey, where in Raleigh do you live?
 
dragon2 -- thanks for the info. So few comparitive tests are done, I'm always interested in them.

Accepting your +/- #, could you give us a percentage difference? I know that with different shapes of blades, probably lengths, and almost certainly geometry, that getting real specific isn't possible. But still, I'd like to know if a 440V knife I have is likely to outcut a Boye blade by 5% or 25%. I mean that 5%, with your +/- figure could be meaningless if we're talking 100 or 200 cuts. But if you're up into the thousands, then 5% is significant. Twenty five percent would be a large difference at any level, but more impressive the higher the number of cuts made.

So, any comparitive #s you could provide would be really appreciated. Thank you,
 
The percentages related to the margin of error I estimated
were roughly 5%. The total number of cuts was close to 1000
for both pieces. The Kershaw out cut the Boye by around 200
slices. Keep in mind these are not very scientific, just some
shade tree experimentation.
To give an idea of the edge conditions of the knives used, both
were sharpened on the medium grit rod of a Sharpmaker, using the
20 degree slots. Both were also backbeveled to about 17 degrees
using a DMT blue bench stone.
 
To address the blade length question, I made a
concious effort to use only the first inch or
so of the blade. This section on both knives
is relatively straight and easier to control.
In terms of edge geometry, the Boye edge is
ground a bit thinner when new. This particular
Boye has been used hard and the edge has been
thickened a little by nearly 3 years of use and
honing.
 
dragon2, I assume you cut until the blades had suffered some specific level of edge degredation, how did you determine the stopping point?

The percentages related to the margin of error I estimated were roughly 5%.
Click to expand...

How did you estimate that?

Do you know how Kershaw is heat treating the 440V, are they going hard like 59-61, or ~55 RC like Spyderco?

Did you see any evidence of chipping after the cutting?

Any comments on sharpening? Was one blade significantly easier to restore than the other? Did steeling have any significant effect on either blade?

-Cliff
 
The Random Task as well as all of Kershaw's and my 440-v blades are heat treated no harder than 55-57 Rc any harder and this alloy becomes brittle and will not take a good edge without crumbling. Any harder and it has no impact resistance or toughness.
So in my experience 440-v is useless in the 59-61 Rc levels,two or three Rc points are critical with this alloy
 
In responce to Cliff's questions, I did not try steeling. I really dont know how hard the Boye steel is. I have never seen it published anywhere. I'll take Ken Onion's word on the Random Task hardness. I cut until the blade would no longer shave easily. "Shave easily" is where the unscientific part and the margin of error come in. Both would still shave, but took considerable effort.

While I'm at it, I would like to ask a question on steeling. I've never had any noticable degree of success at it. Do harder blades respond poorly? Are the steels that come w/ kitchen cutlery sets any good? The grooves on these steels seem very course for their intended purpose.
 
In relation to chipping, I didnt notice any on either knife. I have noticed that the Random Task is more prone to chipping than the Boye for similar tasks. Both sharpen very easily, I think. The Random Task took only about 20 strokes per side on the Sharpmaker the other day. This was after I had dulled it w/ the medium sharpmaker rods so I could take it apart and not loose any fingers.
 
dragon2 :

I cut until the blade would no longer shave easily.
Click to expand...

I looked at this sometime ago, I thought it was unrealistic at first, but after some work found that it did correlate very strongly with edge degredation during use. It is one of the fastest and easiest edge tests to use, however as you note it involves a subjective element. What I found best was to stop and check only every so often, as if you did it too frequently you can fail to see the small differences that creep in. As well have a razor sharp blade on hand to serve as a clear reference.

I've never had any noticable degree of success at it. Do harder blades respond poorly?
Click to expand...

The critical factor is how the edge blunted. If the edge just rolls it should respond well to steeling. If it has worn or broken away steeling will do next to nothing. Both steels you are using are not known for high toughness, and as well cutting cardboard can induce a lot of wear on a knife because its abrasive nature. However considering the high inherent wear resistance of 440V I am surprised that it didn't respond strongly to steeling. The edge might have broken away though.

Are the steels that come w/ kitchen cutlery sets any good? The grooves on these steels seem very course for their intended purpose.
Click to expand...

You can use them as files, which is not steeling but sharpening, this really only works on knives made from soft steels. To use it on harder knives you use really light pressure. I prefer a smooth steel though as you can damage a fine edge readily on a grooved steel. Any hard smooth surface will do though.

I have noticed that the Random Task is more prone to chipping than the Boye for similar tasks.
Click to expand...

That is interesting, Boye's Dendritic 440C is not exactly a high standard for durability.

Ken :

n my experience 440-v is useless in the 59-61 Rc levels
Click to expand...

How hot are you soaking it? What temperature are you using for the temper? Are you using deep cryo? Multiple tempers?

What do you mean by "brittle", on what kind of tasks would the knife chip out readily?

-Cliff
 
Ken, was that 440V experience based on factory blades or some that were heat treated as customs in small lots? I haven't worked with 440V in a very long time, but I didn't experience any problems at Rc60, and one of those blades has seen a LOT of hard hunting use in the past 3 years.

Certainly, it could be an edge geometry issue as well, I suppose.
 
I agree with Cliff's comment that smooth steels work best. The one I have is a Japanese model that I actually purchased in a "used items" store. It has ultra fine lines running parallel with the steel's shaft and is a fairly inexpensive one and is NOT diamond coated. Dragon, they are easy to use with just a bit of practice. You don't have to look like those chef's whose hands are a blur when they use them. Just get an even flow and don't bear down, just let the steel and the knife do the work. Hold the spine of the blade up until you feel the edge is lined up and guide the blade down while sliding across at the same time. Flip over and reverse. It's really easy and you'll get a "feel" for it after just a short time and to me is much easier than trying free hand with a flat stone. Pratice on some cheap kitchen knives until you've got it down. I even touch up my S60&90V knives with it. Like any knife though, when they get DULL, it's time for a complete re-sharpening but the steel lets you keep them sharp for a long, long time.
 
In responce to Cliff's last question, both were used to remove fireproofing from structural steel members. The testing agency I work for tests the density of the sprayed on fireproofing that replaced asbestos. The test requires small samples be cut from the steel. Structural steel is usually only about 50,000 psi yield strength, so its much softer than the blades I use. The Boye knife would dull after 1-2 passes through the material. The Kershaw would take 3-4, but if I put too much pressure on it, the Kershaw would chip, where the BDS would not.
 
With regard to steeling, I have not used a smooth steel. Actually, the only ones I've tried were of the rough variety. They usually did more harm than good. I'll see if I can find one and use it on the next test.
 
Gene :

Dragon, they are easy to use with just a bit of practice.
Click to expand...

Sal Glesser noted awhile ago he uses the rods from the Razor Edge folding steel in the Sharpmaker. That would be one way to take all the guesswork out of the angle. Spyderco should come out with a set of such rods for the Sharpmaker.

Dragon, interesting results.

-Cliff
 
Cliff,
Thanks. Its good to see more than a little interest in my first post. I'm considering getting rid of some of my knives, but just to get different ones. I may do a comparison between a couple of big knives later. Hopefully the tests will have less of a fudge factor.
 
I agree Cliff and forgot to mention that I use the Razor Edge rods myself occasionally but not in the Sharpmaker system. Nice idea and I agree that Sal might consider that option in future systems. Steeling really is a simple, easy way to keep that edge pointing down!

Nice report Dragon!
 
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