Things you always wanted to know but were afraid to ask Kevin

Kevin R. Cashen said:
I think it would be great if the questions in this thread where broken down into seperate threads with titles that invited all to participate and I could contribute to my hearts content. Believe me I don't need my name attached to it to know if a person wants my input, folks have learned the topics that will press my buttons and get my attention.
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I hear ya!

... might be a good opportunity for the rest of us to work on our question asking and listening skills though... a little different anyway... without so many opinions to weed through. :)
 
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One more thing I'd like to add, (because I started this thread) , since Kevin is taking the questions seriously and doing his best to give honest answers is that we keep the questions sincere. If you think you already know the answers, then don't bother asking. Don't waste your time and his.

This isn't a stump the expert thread.

One of the things I've noticed is that some of us become so accustom to answering questions, we forget how to ask,... including myself. However, I don't think there is anything more important than learning how to ask quality questions and listening to the answers…

I'm sure there are some things we can all learn by this.

So, let's give Kevin the floor and try to show some courtesy and respect. :)
 
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Tai Goo said:
... If you think you already know the answers, then don't bother asking. Don't waste your time and his...
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That is an interesting phenomenon Tai. On a rare occasion I get it in e-mail, but it is common on forums. Very often people will ask questions for the sole purpose of validation of what they are already doing, when they do not get this validation they are not happy. I guess all of us are guilty of occasionally asking a question that we would accept only certain answers to, but as you said if we feel we already have the answers, why are we asking a non rhetorical question? I think it should also tell us whether we are really confident in our position if we feel a need for validation from another’s answers, and we are shaken when those answers don't match our own.
 
Kevin R. Cashen said:
To test the final blade I would cut very abrasive things (cardboard can be pretty nasty) for my slicers. I wouldn’t really bother with rope cutting as I find it very subjective and unreliable for consistent results. For the choppers I would hit seasoned hardwood and see if it like it before whacking something of more substance like deer antler, if I still had doubts I would smack that edge dead on and then impact at 45 degrees with a brass rod, but as I have indicated I wouldn’t bother slowly pushing the edge against anything unless I was checking for abrasion resistance. Unless I am measuring a specific property I am a firm believer in just using the knife for what it was intended to do and seeing how it works. If I am checking a specific material property I insist on tight controls and quantifiable results or I will devote my efforts to more useful things.
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Kevin,

It seems you have little use for "The Brass Rod Test"... flexing edge at low angle and ideally finding no chipping and no folding. Would you say why, please?

Mike
 
Mike Krall said:
Kevin,

It seems you have little use for "The Brass Rod Test"... flexing edge at low angle and ideally finding no chipping and no folding. Would you say why, please?

Mike
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If I may,... I believe Kevin has already answered that on another thread. You might try doing a search.

What he said, as I recall, is that it just won't tell you very much, and I agree. It will only tell you that the blade is somewhere in the ball park and that there isn't anything "seriously" wrong with it, but that's about all it's good for.

Although there are a lot of variables, and it takes some common sense, comparison testing, etc., to know what you are looking for... the chopping into a brass rod at a 45 degree angle, as he suggested, is a much better test.

... Just trying to save Kevin some time, so he doesn’t have to keep repeating himself.

If he has anything to add I'm sure he'll chime in. :)
 
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Mike Krall said:
Kevin,

It seems you have little use for "The Brass Rod Test"... flexing edge at low angle and ideally finding no chipping and no folding. Would you say why, please?

Mike
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While I have covered it previously I can still sum it up fairly quickly, The answer is right there - I personally have little use for it. If it works for others then they are welcome to use it, but I feel folks should know what it is and what it isn't as well. It can only give an indication of overall strength if the yield point is exceeded (bend or chip). Within the elastic range all it can tell you is how thick or thin the blade is ground regardless of the heat treatment.

I have no use for any test involving "flex" because I understand (along with the rest of the industrial world outside of bladesmithing) that flex is mostly a function of cross section. One doesn't need a brass rod, a torque wrench or even the blade being "tested" as long as they have a the cross sectional measurements, a calculator and an understanding of Young's modulus. Although it has been pointed out that some understand that it is not a direct indication of hardness, virtually everytime it has been discussed in print and other authoritative sources it is held up as a replacement for actual hardness tests. One thing to remember is that in any actual penetrative hardness test if the sample "flexes" at all the readings are worthless and thrown out until the flexing is eliminated.

It is a test that some find use in, but for me it is so broad in what it reads that it is not worth the confusion it can create. However I do know that it is popular enough that I would be fighting quite a losing battle to oppose its use, the regular contributers to Blade magazine are far too popular for that. So all I really hope for is that people may understand its limitations, without wanting to stone me to death for doubting scripture. :)
 
kevin...if it's not too much trouble .....i know u frown upon some of the tests for hardness and other aspects of knives.....can u briefly explain what tests you use on your blades.....ryan
 
ryan9977 said:
kevin...if it's not too much trouble .....i know u frown upon some of the tests for hardness and other aspects of knives.....can u briefly explain what tests you use on your blades.....ryan
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Look at post #31 in this thread, Ryan... page 2... last paragraph
 
Tai Goo said:
If I may,... I believe Kevin has already answered that on another thread. You might try doing a search.
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Thanks, Tai...

Does anyone have a link to the previous discussion... I can't search here and the Google search for BF doesn't work anymore.

Mike
 
Mike Krall said:
Thanks, Tai...

Does anyone have a link to the previous discussion... I can't search here and the Google search for BF doesn't work anymore.

Mike
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you can go to google and:

site:bladeforums.com whateveryou'relookingforhere
 
Kevin R. Cashen said:
It can only give an indication of overall strength if the yield point is exceeded (bend or chip). Within the elastic range all it can tell you is how thick or thin the blade is ground regardless of the heat treatment.
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Tapio Manner SFI http://forums.swordforum.com/showthread.php?t=78219&highlight=Young%27s+Modulus
"High hardness leads to notch and brittle fracture risk and tempering lowers yield stress, what is looked for is a compromise between these - as so often."

I ain't arguing...

I learned about "The Brass Rod Test" from Wayne Goddard books (now termed "The Rod Test"). His discription sometimes included applying 30 to 35 pounds of pressure. In relation to what Tapio Manner said, which I am assuming is correct, does the consistently applied pressure cause any useful information to be found or does this still fall within the realm of, "within the elastic range"?

Mike
 
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Mike Krall said:
Tapio Manner SFI http://forums.swordforum.com/showthread.php?t=78219&highlight=Young%27s+Modulus
"High hardness leads to notch and brittle fracture risk and tempering lowers yield stress, what is looked for is a compromise between these - as so often."

I ain't arguing...
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Indeed since that thread confirms what I have been saying quite well.

I learned about "The Brass Rod Test" from Wayne Goddard books
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I was fairly certain that you had ;)

His discription always included applying 30 to 35 pounds of pressure.
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Hiw is this determined? I have never seen the load applied with anything but hand pressure. At any rate it is irrelevant anyhow since...

In relation to what Tapio Manner said, which I am assuming is correct, does the consistently applied pressure cause any useful information to be found or does this still fall within the realm of, "within the elastic range"?..
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as long as you are within the elastic region even if you can measure the exact pressure applied to 33.5687 lbs exactly, it still means nothing since the modulus of elasticity for steel is around 30psi x 106 whether it is 65HRC or 35HRC. Fully hard or fully soft it takes the exact same ammount of force to flex that steel to a given degree, unless you grind it thicker or thinner, then it all changes and you start over from square one. Tempering can indeed affect whether it will fail in ductile mode or brittle mode but the entire spectrum of blade heat treatment falls between these two, so this "test" is about as exacting as a definite maybe. :confused: A broad side of a barn comes to mind.

For more information right here on Bladeforums try these:

http://www.bladeforums.com/forums/showthread.php?t=530366

And page 3 of :

http://www.bladeforums.com/forums/showthread.php?t=440355
 
Kevin, would the rod test atleast show you you have a nice thin geometry, and actually be an acute enough of an angle to be a knife and not a KSA(knife shaped axe)? If I understand it right, if you try this test on a very thick spined blade with a steep geometry IE a heavy chopper the edge will not flex over the rod, as opposed to a thinner ground slicing knife which will flex over the rod. So maybe it is useful for a approximation of a successful geometry for beginners? I know my early blades were MUCH too steep beveled to do much of ANYTHING rather than just crush. After heat treatment I think geometry is a little understood technique in itself, after all it is where you get your flex and strength in a knife from (right?).
 
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