Blade Edge Keeps Chipping While Sharpening.

G

Gene

Joined
Oct 2, 1998
Messages
1,781
Hello Folks,
I have a smaller fixed blade that is giving me fits! The blade was made from a file and I bought it second hand here on BF and this blade is SUPER HARD! This is the ONLY blade I've never been able to sharpen and I've sharpened blades made of anything you can think of.

When I received it, it had no edge whatsoever but I could see where a prior owner had tried to sharpen it and only caused scratches on the blade. I thought, "no big deal". I'll re-profile the edge and sharpen it. The reason I knew I'd have to reprofile it was it had no edge at all. It was as dull as a blunt butter knife!

I mainly use a Lansky system but substitute DMT diamond stones as the Lansky stones are okay but not for the newer, harder steels. I have used the Lansky system for about 15 years or so and have sharpened hundreds of knives sucessfully with it over those years. This one is different!

The problem is, is that everytime I get the edge close to a burr, the edge just chips out. I've tried over and over but I cannot get a burr and instead of a burr, the edge just chips. Again, I know how to sharpen and have used the Lansky system for years.

I found out who the maker of the knife was and e-mailed him and asked him since it was made from a file, if it could have been possibly been sent out without heat treating because this thing is still as hard as a file! He e-mailed back and said if it hadn't been heat treated, it would be super easy to sharpen but I'm not so sure.

He also said that it couldn't be sharpened with flat stones and should be stropped on a piece of sand paper over a leather stroppe and that would sharpen it. Maybe I'm wrong but I would hate to reprofile a blade using that method!

I've sharpened almost all steels, (including the modern steels), with all sizes of knives, (except very large fixed blades), with the Lansky and DMT diamond stones and this is the ONLY knife I haven't been able to sharpen because the edge keeps chipping out instead of bending to make a burr.

I give up with this and I think the edge is still hard as the original file and that's why it keeps chipping out. What do you guys think?
 
Ya, donny, I'm sure you're right. I wonder why the maker was so adamant that sharpening with sand paper and a stroppe would make all the difference?
 
The blade might not be tempered, try this, get another new file, drag it across the blade(not the edge) and if it just slips off the blade and doesn't grab it, then it's not tempered, if the file grabs on to it then it's tempered.

If it's not tempered, the good thing is that you can temper it in your own oven.
 
I've had one knife that did the same thing. Only thing I could do to prevent the chipping was put on a much higher angle edge. I suggest regrinding a very thin edge bevel then put on a high angle micro edge. Putting on a deeply curved convex edge would do pretty much the same as the two bevel edge also but if you use a Lansky the two bevel is going to be easier. Good luck.
Just as info. I have a fully hardened 1095 blade and it doesn't chip at all when being sharpened and takes a very sharp and thin edge. I'm just guessing that it being too hard isn't the problem. I don't have any clue what could be the problem with your knife or the one I had is, but it is probably a heat treat problem of some kind.
 
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Gene said:
Hello Folks,
I have a smaller fixed blade that is giving me fits! The blade was made from a file and I bought it second hand here on BF and this blade is SUPER HARD! This is the ONLY blade I've never been able to sharpen and I've sharpened blades made of anything you can think of.

When I received it, it had no edge whatsoever but I could see where a prior owner had tried to sharpen it and only caused scratches on the blade. I thought, "no big deal". I'll re-profile the edge and sharpen it. The reason I knew I'd have to reprofile it was it had no edge at all. It was as dull as a blunt butter knife!

I mainly use a Lansky system but substitute DMT diamond stones as the Lansky stones are okay but not for the newer, harder steels. I have used the Lansky system for about 15 years or so and have sharpened hundreds of knives sucessfully with it over those years. This one is different!

The problem is, is that everytime I get the edge close to a burr, the edge just chips out. I've tried over and over but I cannot get a burr and instead of a burr, the edge just chips. Again, I know how to sharpen and have used the Lansky system for years.

I found out who the maker of the knife was and e-mailed him and asked him since it was made from a file, if it could have been possibly been sent out without heat treating because this thing is still as hard as a file! He e-mailed back and said if it hadn't been heat treated, it would be super easy to sharpen but I'm not so sure.

He also said that it couldn't be sharpened with flat stones and should be stropped on a piece of sand paper over a leather stroppe and that would sharpen it. Maybe I'm wrong but I would hate to reprofile a blade using that method!

I've sharpened almost all steels, (including the modern steels), with all sizes of knives, (except very large fixed blades), with the Lansky and DMT diamond stones and this is the ONLY knife I haven't been able to sharpen because the edge keeps chipping out instead of bending to make a burr.

I give up with this and I think the edge is still hard as the original file and that's why it keeps chipping out. What do you guys think?
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I have similar problem with one of my Higonokami and one experimental bulat, and solution is - waterstones. Everything else just too hard.

Thanks, Vassili.
 
Blown heat treat. The last S30V blade I had did the same thing ... in fact you couldn't even apply a clean microbevel with Crocksticks/Sharpmaker using very light pressure.

So even if you could get it to take an edge without chipping, it isn't going to give good edge retention. I would return it.
 
Thanks for all the replies. Richard j has graciously volunteered to help me out with this so we'll see what happens.
 
Gene said:
Thanks for all the replies. Richard j has graciously volunteered to help me out with this so we'll see what happens.
Click to expand...

See the thread I just posted, he did a perfect job on rebeveling my Spyderco Superhawk and is great to work with. I would think if the problem can be fixed he could do it.

Mike
 
Sounds like it's not tempered back enough. Even if you manage to get it sharp, the edge will be brittle and weak. It can probably be fixed.
 
James_Terrio said:
The good old brass rod test will give you a good clue as well. If you have access to a Rockwell tester, by all means use it.
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Just to nitpick... unless you have side-by-side samples and a reliable (if not quantifiable) way to measure force, the brass rod test is pretty useless. Young's Modulus (Elastic Modulus, the ratio between force applied and distance compressed (that's overly simplified, but work with me here)) is essentially constant for all steels. The difference between hardened and tempered steel lies in how much force they take before the deviate from that line. Basically, every steel will flex the same amount for a given amount of force (within the elastic range), so you need to be able to (justifiably) judge how much force it takes to put a bend or chip into your edge (which is an easy way of describing the end of the elastic range, which is (non-linearly) related to hardness.) Problem is, you then have a chip or bend in your edge.

You know what, Kevin Cashen knows his material science pretty bloody well, and is much more eloquent about it than I am, so I'll refer you to him:
Kevin R. Cashen said:
The edge flex thing is like the file test, adequate if you are not all that particular. It will get you in a wide range but will not tell you anything specific. I would say that the file test can be more accurate since it at least measures a form of hardness (abrasion or scratch hardness but not penetration), while the brass rod flex test tells you a whole lot about how thin you ground the blade and not as much about heat treatment as people would like to think. People who hold it up as the definitive test are simply blowing hot gas. The only way the test can tell you about heat treatment is if you push it to the point of yielding and then you have a kink in your edge- kind of like the nice fellows in the middle ages who would tie rocks to your daughter, toss her in pond and then tell you the great news that she was not a witch after all! Hey that’s great, but it is rather moot point now isn’t it? And of course if you have a good hardness on your edge it will flex like crazy if it is thin. Are we looking for a certain amount of deflection every time? Are we looking for a certain amount of force required every time? If it is a set amount of deflection forget about however you heat treated it and just grind it thinner to meet your mark. If you want to really lay on it and not deform it at all simply grind it thicker. I personally think there has been a lot of slight of hand and misdirection involved in many of these popular tests that make the presenters knives look great, either in their own mind or in the public. Flexing over a rod will get you inside a huge ball park if that is all you need, but it is not a real definitive or even accurate test overall.
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If I'm being a pretentious engineering student, sorry, it just gets under my skin when people ignore science.
 
Lucky Bob said:
If I'm being a pretentious engineering student, sorry, it just gets under my skin when people ignore science.
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I don't find your post nitpicky or pretentious, friend :) You raise good points; that's why I said the brass-rod test provides a CLUE, and a Rockwell test is recommended if available. The brass-rod test is indeed highly subjective and I never said otherwise, nor did the article I referenced. I offered it as a beginning step that's easily demonstrable to folks with little or no experience. I would like to clarify that deflection isn't the only thing you measure with it; returning to true is a HUGE part of this admittedly simplistic procedure. I'm just sayin' ;)

Even a Rockwell test doesn't provide all the info we would need to truly explain what's going on with this blade, though it's a good start. Different alloys with the same RC will have different toughness and abrasion-resistance attributes.

The only tests that really matter to me are performance-oriented. Clearly the OP's blade has failed early and needs work; if he can't sharpen it without the edge chipping, it definitely needs work and will never stand up to general use, much less rough use. Frankly, if I had made/sold that knife, I would be ashamed and offer a full refund or replacement. Assuming (yes, I know what "assume" stands for ;) ) he's not trying to sharpen it by throwing rocks at it or something... which is doubtful.

Mr. Cashen has been a strong and welcome influence on me just through his posts here; he has clearly and succinctly dispelled a heckuva lotta myths I grew up taking as gospel. My understanding and my knives are much better because of him and others like him.

I always welcome input from folks more educated than I am. :thumbup: I certainly don't ignore science, even when I don't fully understand it. Fair enough?

please note my liberal use of smileys... I'm not upset and don't want anyone to think so. these are just my honest, good-natured observations in response to valid criticism... we all benefit from that!
 
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More than fair. I guess I'm just a dilettante (and readily admitted so, yada yada yada), but I've never seen any value to the brass rod test short of having a force gauge and a known-good (and -identical!) model for comparison... which seems to be much more work and precision than the original purpose/usage.

My $.0002 (yes, .02 cents) on the original subject: sounds to me like the blade was under (or never?) tempered, like you (and others) had suspected.
 
Again, thanks much for all your informative replies. I sent it off to richard j today to see what he can do with it.
 
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