3V vs S35VN characteristics?

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CrimsonTideShooter said:
That is just a range, the actual HRC number can be + or - 1.

Same with Jim's hardness tests. Keep in mind all HRC testing is + or - 1 accuracy.
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Yeah, I get that. But Jim's doesn't appear to be in the range... officially being 58-59 and his testing out at 59.5. If the difference between, say, 58.5 and 59.5 in s30v is so "night an day", maybe CRK should kick it up a notch...
 
I thought it had something to do with the references and calibrations.

I was told that you could do a run of tests and all the samples would have correct *relative* hardnesses (i.e. relative to other samples in the run...as in, this is one point harder than that, etc.), but if you have a single sample tested, the results will be returned as xx.x plus or minus 1.0

I could be wrong, but that was what I was told a year or so ago when I looked into it.
 
ohmyheckinslc said:
Yeah, I get that. But Jim's doesn't appear to be in the range... officially being 58-59 and his testing out at 59.5. If the difference between, say, 58.5 and 59.5 in s30v is so "night an day", maybe CRK should kick it up a notch...
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I don't think you understand what I'm saying. You can get any result from the hardness tester, but the accuracy of that result will be + or - 1. In other words, 59.5 is the result, but it could really be anything from 58.5 to 60.5. Make sense?


A company like CRK can state that their knives are 58-58 hrc all day long, but there will be knives that exceed that range. They won't test every single knife, it's not feasible.


ETA: I didn't mean for this post to sound rude at all, if it came off that way. Had to type it up in a hurry.
 
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CrimsonTideShooter said:
I don't think you understand what I'm saying. You can get any result from the hardness tester, but the accuracy of that result will be + or - 1. In other words, 59.5 is the result, but it could really be anything from 58.5 to 60.5. Make sense?


A company like CRK can state that their knives are 58-58 hrc all day long, but there will be knives that exceed that range. They won't test every single knife, it's not feasible.
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Just wondering if you or anyone wants to hazard a guess - how many blades do you think a maker like CRK treats a one time? Do you think they should (or do) test one from each batch?
 
Back in the 90's, I remember that Gryphon knives used to advertise that each of their blades had a divot just behind the ricasso where it was tested for hardness. For a small knife company, I don't think it would be that big of a deal to test each blade, especially if each one is supposedly assembled and finished by hand. There's just no excuse for that kind of failure where quality and precision are the key selling points. I can foresee a joke based on this, looming over the horizon...
 
gooeytek said:
Back in the 90's, I remember that Gryphon knives used to advertise that each of their blades had a divot just behind the ricasso where it was tested for hardness. For a small knife company, I don't think it would be that big of a deal to test each blade, especially if each one is supposedly assembled and finished by hand. There's just no excuse for that kind of failure where quality and precision are the key selling points. I can foresee a joke based on this, looming over the horizon...
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The test is what it is and what happened is apparent.

The real issue here IMO is how CRK will address the issue.

In the end that is CRK's choice and decision to make.
 
CrimsonTideShooter said:
I don't think you understand what I'm saying. You can get any result from the hardness tester, but the accuracy of that result will be + or - 1.
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About a year ago I was researching RC testers, wanted to buy one. There were quite a few models with 0.1 HRC accuracy. Although, price was too high to justify the purchase just for knife reviewing.
As for the +-1 testers, doing 2-3 tests will provide more accurate result.
 
unit said:
I thought it had something to do with the references and calibrations.

I was told that you could do a run of tests and all the samples would have correct *relative* hardnesses (i.e. relative to other samples in the run...as in, this is one point harder than that, etc.), but if you have a single sample tested, the results will be returned as xx.x plus or minus 1.0

I could be wrong, but that was what I was told a year or so ago when I looked into it.
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reference blocks are needed to check calibration, and repeating the test on a piece to get a more accurate measurement requires separating the indentations by at least four times the diameter of the indentation. Testers can give a measurement resolution down to one-hundredth of a point. Changes in the performance of the test can alter the hardness measurement. This online document will probably address most questions. http://westportcorp.com/resources/rockwell_hardness_test/index.php
 
Gator97 said:
About a year ago I was researching RC testers, wanted to buy one. There were quite a few models with 0.1 HRC accuracy. Although, price was too high to justify the purchase just for knife reviewing.
As for the +-1 testers, doing 2-3 tests will provide more accurate result.
Click to expand...

Wow, .1 is some very high resolution!

Yeah that's true. I wonder if most places do use an average?
 
cziv said:
Just wondering if you or anyone wants to hazard a guess - how many blades do you think a maker like CRK treats a one time? Do you think they should (or do) test one from each batch?
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I honestly have no clue. It would be cool to know, though.

If I had to guess, I'd say they did batches with hundreds of knives at once. But, that's just conjecture.
 
CrimsonTideShooter said:
Wow, .1 is some very high resolution!

Yeah that's true. I wonder if most places do use an average?
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Ave for Production knives is set by the manufactor, if they want + or - 1 rc or + or - 2 rc ect.

That also depends on the heat treater and how tight they can get it, that can vary.
 
Ankerson said:
Ave for Production knives is set by the manufactor, if they want + or - 1 rc or + or - 2 rc ect.

That also depends on the heat treater and how tight they can get it, that can vary.
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Ahh, so there is really no way to know what type of accuracy you can expect?
 
I think RC tester's accuracy gets mixed up with heat treatment accuracy. Getting a tester with 0.1RC precision isn't a problem, but heat treating few hundred blades in one oven to the same precision is much more challenging. Even if the oven is heating all of its area perfectly uniformly, there are other factors that can affect each blade... In the end, +-1 RC is pretty good result for batch HT.
 
Gator97 said:
I think RC tester's accuracy gets mixed up with heat treatment accuracy. Getting a tester with 0.1RC precision isn't a problem, but heat treating few hundred blades in one oven to the same precision is much more challenging. Even if the oven is heating all of its area perfectly uniformly, there are other factors that can affect each blade... In the end, +-1 RC is pretty good result for batch HT.
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Yeah I'd be happy with that. Now if a manufacturer states 59-60 and you end up getting blades closer to 56, there's an issue.

Also I think it would depend on where the sample was taken from the austenizing chamber. If there is a cool or hot spot, you'd never know if the sample wasn't taken from a blade sitting in the spot. You could have 99% of knives coming out fine, but that 1% from the cold/hot spot could be leaking out without being caught.
 
To John / CTS Re the CRK Sebenza S35VN edge issue.

It would be surprising if getting your blade Rockwell tested voided CRK warranty, that is provided it was done in a suitable location so as not to interfere with operation or act as a stress raiser. Maybe somewhere on the tang area might be suitable. The result could be very interesting as a starting point to help understand the problem with your CPM S35VN.

My experience with hardness testing on the Rockwell scale is that it’s not expensive. I’d be willing to make a financial contribution to that end if you decide to proceed. Send me a PM if it’s a go.
 
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