Hardness Testing

David Wesner

David Wesner

Joined
Jan 5, 2005
Messages
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How do you guys accurately test the hardness of your blades ? I've been thinking about this for a while and Sams post "1095 Problems" prompted me to finally ask.

The obvious answer would be a Rockwell tester, which I have. Common sense tells me that deflection due to blade bevels makes for a less than perfect set-up for accurate results. Testing on a flat surface that may or may not exist on any given knife is usually too far away from the edge that I'm concerned about testing. Hollow ground bevels also create a unique set of issues for accurate testing.

Would a custom sine plate type anvil for a tester work or do you think there would be too much of a "mushy" factor ? Would a convex shaped anvil work for hollow ground bevels ? I'm beginning to think that the hardness testing file sets sold in various supply catalogs may be more appropriate ( or accurate ) for knifemaking applications. What are your thoughts, solutions etc. when it comes to accurate testing of your knife blades ? Thanks for any help or suggestions you can provide.
 
Wel,Yes, a custom anvil for your Rockwell tester would be fine.....IF YOU WANTED A LITTLE DIMPLE IN THE BLADE. I test the tang just above the ricasso (where it won't show after finishing). Most blades I forge or grind don't get Rc tested. I use a new file after the quench, and use a good pyrometer white doing the temper. Results are verified be "FEEL". This is how 98% of most smiths determine the hardness.

The hardness of any blade should be determined NOT as "Is it RcXX hardness ?" but as " Is it the right hardness for the job it will do". Controlling those factors through steel selection, quench media,HT, tempering, and blade geometry is more important than saying, "My blades are all Rc58.5."
Stacy
 
My personal feeling is that there is too much emphasis wrongly placed on the Rc hardness of a blade. Although it is a great tool for experimenting, and to acquire information about a given steel/heat treatment, I don't think hardness alone is a good indicator of whether a blade will perform. There is so much more to it than a blade being "hard". Having said all of that, there was a time when I went though a "testing phase", for about a year I had samples tested on nearly a daily basis.....after realizing that everything was coming out as I anticipated, I quit wasting the time and effort to Rc test.
The biggest issue I have with makers boasting about the Rc hardness of their blades is this: For an accurate reading, the test sample must be flat and true, which generally means performing the test on the ricasso. Thats usually the thickest part of the knife, and certainly isn't the "business end". All of my tests were conducted on a sample that was treated the same as the blade it was meant to represent, but that still doesn't mean I couldn't have messed up the blade. I personally believe that the brass rod test is a far better indicator of correct "working hardness" than a Rockwell test could ever be. Maybe I'm just tired of people basing their opinion as to whether a knife will be good or not on the Rc hardness.....sometimes a false and misleading judgement.
 
Ed knowing you, I must respect your belief even if I didn’t bear the respect that I do for you, belief is like opinion, not right or wrong just ours, and nobody can take that away. I have formed some opinions as well after my share of observations; they also are neither right nor wrong to anybody other than myself. In my opinion Rc hardness should not be used to judge a knife, it should be used to evaluate the effects of processing on the material. The finished knife is entirely a subjective object when determining good or bad, one mans perfect cutter is another mans headache in sharpening or a hand breaker. Almost anything on the finished product can come down to opinion as well.

I chased opinions for many years until I realized I was trying to pin down a feeling instead of facts. I found real progress and a whole new world in standardized testing of the materials, the processes, and then leaving human touch for the finished knife. One of the first things I found was that established, standardized tests left no wiggle room for what I wanted to see rather than what was, and this took some soul searching to surrender to. As I mentioned before, I agree that Rockwell testing can give very little to the overall package of the finished knife, but in determining the material properties is a very powerful tool because it measures one specific property in a way that is quantifiable and not open to interpretation, you just need to know from the start what it is you are looking to measure. The same simply cannot be said of flexing an edge over a brass rod. What does it measure? Not hardness by any definition that I have encountered. It can heavily measure elasticity (we wouldn’t call it “flexing” if we weren’t measuring elasticity) and hardness or softness (ductility) has no meaning within the elastic range. If it flexes well is it heat treatment or too thick or too thin? If the edge chips out is it too hard or was it overheated? If the edge deforms does that mean it also lacked abrasion resistance? Will it be easier or harder to sharpen. For me there were two reasons to shun the standard testing means- the testers were too expensive for backwoods bladesmith like me, or it left no room for me to interpret the results into something I preferred them to be. My hunger to the details caused me to bite the bullet on both so that I take the position that I take today. In my shop the Rc tester tells me one very specific thing – the penetrative hardness of the steel, this one little thing is but one piece of the overall puzzle, trying to make the whole picture out of it is fruitless, however here that brass rod flex doesn’t fly at all because it just doesn’t have any set shape to determine if it even belongs in the puzzle.

Just my opinion, based upon my observations, added to the mix in order to have a discussion from all sides. I gotta tell you though, that it is a lot tougher to have opposing opinions with guys you really like. Or perhaps it is easier since you know there are much bigger things you share the same opinion on to even have the smaller opposing ones matter.
 
David Wesner said:
How do you guys accurately test the hardness of your blades ? I've been thinking about this for a while and Sams post "1095 Problems" prompted me to finally ask.

The obvious answer would be a Rockwell tester, which I have. Common sense tells me that deflection due to blade bevels makes for a less than perfect set-up for accurate results. Testing on a flat surface that may or may not exist on any given knife is usually too far away from the edge that I'm concerned about testing. Hollow ground bevels also create a unique set of issues for accurate testing.

Would a custom sine plate type anvil for a tester work or do you think there would be too much of a "mushy" factor ? Would a convex shaped anvil work for hollow ground bevels ? I'm beginning to think that the hardness testing file sets sold in various supply catalogs may be more appropriate ( or accurate ) for knifemaking applications. What are your thoughts, solutions etc. when it comes to accurate testing of your knife blades ? Thanks for any help or suggestions you can provide.
Click to expand...

David I think the best situation would be a Rockwell tester in conjuction with a Rockwell hardness file set so that the two can verify each other. They both measure hardness but in different forms, penatrative and scratch. The direct edge could be done with the files and to be certain that the Rc reading on the flat jives with the edge (though the nice thing is that one can almost count on the edge being at least as hard as the thicker portions), and that the scratch hardness coincides with the penetrative hardness. But then a Knoop micorhardness tester would be a really nice addition to the mix as well:D A guy can dream can't he?;)
 
I'm not an expert, but I say through harden before grinding and test on the rockwell tester. You can then use files after grinding to see if you maintained hardness.
 
Kevin,

I think we're both saying basically the same thing, just in different terminology. I agree 100% in that each maker must determine what he/she expects, and how best to achieve it. The rockwell testing can offer a specific piece of the puzzle, but I feel that many rely way too much on it's results, rather than combining that/those results with practical testing and use to determine the end value of a blade. I've read many posts you've made over the years, and applaud you for the depth and thoroughness you utilize in your testing methodology. Your one, in my opinion, of a small number who would not rely solely on a single scientific fact to determine the overall end assessment.
There is certainly a place for the scientific results, but I do not subscribe to them being the absolute final word in anything, especially blades. I have had far too many "experts" in my shop over the years, who witnessed things with their own eyes, and still insisted that it was impossible to do that with steel. What you described as chasing a "feeling", I term as experience. That's not to say that I'm right and your wrong, it only means we might look at it from different perspectives, which is OK. If I had to put it into words, I would say that your research is much more scientific, where as mine is more practicality based. It might also be that I've not yet reached the level/depth of testing that you do/have, and someday maybe I will. I've always told my students two things.... There are as many ways to do something as their are Bladesmiths/knifemakers doing it, and that if anyone says "this is the way it MUST be done, or is the ONLY way", to be polite, and thank that person for their time....then walk away. Even though I may not subscribe to everyone's methodology, that doesn't mean that I don't respect it and appreciate it. Just because we disagree on something doesn't make us rivals, just friends with different opinions. :)
 
Ed, I can guarantee that if we were side by side at a show and across the isle from some guy whose only answer to every question was that his knives are Rockwell 60, that we would both be shaking our heads and chuckling together. We all get those question and conversations from the public that can get listed in the top ten clichés that get thrown at knifemakers. I can always tell a guy who is really trying too hard to look like he knows something about knives when the first and only questions he asks are about the Rockwell hardness. It is so pervasive that it is one of the only things that virtually every guy, who just found out that there are shows to see knives at, will know about. The sad part is I believe 9 times out of 10 I could throw out some jibberish like my knives all check out at 412 on the zagmoid Rockwell scale only to get very impressed nods of approval.

I get odd readings (not wrong, just unexpected) from the Rockwell tester all the time, taken entirely by themselves they could send me in all kinds of wrong directions, that is why it is so important to triangulate with another method of analysis. The Rockwell tester is like putting your hands in a dark and covered box to feel what is inside, you may be able to tell general shapes and whether it is animal, vegetable or mineral, but beyond that you are guessing until you take the lid off and look inside and begin to use your other four senses to eliminate all other possibilities but one. That is my thing, and my pursuit; not stopping at narrowing it down to 10 possibilities but keeping at it until I have eliminated all but one.

I don’t view my approach as scientific versus practical since I see hard quantifiable numbers and precise measurements as the ultimate in practical. If I can borrow a term from our friend Tai Goo, I see it as logically technical versus intuitive. Some of us like to trust our instincts that something is there and some of us need to see it, measure it, and verify our instincts before we trust them.

In fact the word “science” has been thrown at me so often as a pejorative lately that I have been thinking of all the “scientists” whom I have met that were totally full of #$$&. Certain academics are some the most ignorant people I have encountered. When theory becomes dogma, textbooks become scripture and PhD’s are seen as prophets, you have the makings of a religion uglier than any radical fundamentalist sects operating today. Metallurgy is a material science but is not an orthodoxy or creed, but just a powerful tool for understanding the material we all work with, nothing more, nothing less. I have ran into many of those same “scientists” who see anything not covered in their specific studies as impossible. But then I have had just as many plain common sense guys visit my shop and see only what they want to see in the results, and looking any deeper would threaten their comfortable conclusions. Just the other day I had a guy on the phone who was still telling me about proper edge packing, I knew he wasn’t looking for answers but just sharing what he firmly believed, so I politely listened and said “Hmmm, mmm huh, no kidding?”, this guys world would not benefit from contrary data, in fact I only would have ticked him off, just as sharing contrary observations with a scientific zealot would only have invited disdain for my pursuits unsanctioned by official academia.

There must be something in between both the average Joes and scientists who believe more than they look, and I believe that is the path I prefer to take. :)
 
Kevin, I would hope that wasn't a blanket condemnation. :)

I would like to simply point out that a person trained in science who has lost their objectivity and openmindedness is no longer truly a scientist, regardless of the title. Inquisitiveness is at the core of a good scientist. Science is populated with the same spectrum of personality quirks as every other endeavor. Some are better practitioners than others.

In 30+ years in laboratories, I saw people who are exactly as you describe, dogmatic people who had lost their effectiveness. I also saw many more who were vibrantly creative, knowing that the "rules" were there as tools, and a moment of discovery might well rewrite what was currently accepted.

Generalizations are always difficult, much like saying that knifemaking is totally hogwash because of some of the misconceptions that flourish.
 
Not at all Mike but then I am sure you know that;) I prefer to hang around the scientifically minded until any of them become foolish enough to mix their science with that plague of humanity, that killer of reason and logical thought... the dreaded "P" word.

You see I got thinking about it recently when reflecting upon the age old concept of science versus religion. Both are very powerful forces for good and can advance and uplift mankind whenever they are incorporated properly. Both are good until they get mixed with POLITICS. The corrupting power of politics can putrefy anything it touches and oddly enough breads almost identical results of intolerance and irrationality in both religion and science. With enough politics religion becomes Godless and science becomes dogmatic and fanatical, and then we start getting the guys you mentioned, the guys I have encountered, and the mounds of junk science that mete so rightfully despises and often points out.
 
Kevin R. Cashen said:
Not at all Mike but then I am sure you know that;) I prefer to hang around the scientifically minded until any of them become foolish enough to mix their science with that plague of humanity, that killer of reason and logical thought... the dreaded "P" word.
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I would have found it difficult to believe that you had gone over to the dark side, though I thought there was perhaps the outside possibility that some dread mix of grinder grit and stag dust had accidentally found its way into that calabash and chemically lobotomized you. ;)

As you have stated previously, science is one thing, and scientists are another. The former deals with truth, the latter sometimes not. We are, after all, human and subject to frailties.

You are absolutely right about that "P" word and its pervasively obnoxious effects. It was rife in the corporate research world, too. To the point, once, that I got called on the carpet for referring to a decision in a meeting as "political chemistry and corporate science". Sometimes one just can't hold their tongue, though. :D

Sadly, history is a long story of politics intruding in both science and religion, to the detrimant of everyone. One would think that knifemaking would be a straightforward enough activity to avoid it, but where there's money, status, and advantage on the line, BS & politics will soon follow.

That says more about human nature than anything else.
 
Thanks guys for taking the time to discuss this, I learned a lot.

FWIW, the little dimple on the edge is completely removed by finish grinding. Austenitizing and tempering are always done in a digitally controlled kiln or oven. I'm trying very hard to learn as much as I can about different steels, HT techniques, blade geometry etc. Rockwell testing is just one more tool in my arsenal and I'm trying to figure out how to use the tool properly for knifemaking. I'm sure you'll all have to agree that knifemaking requires many new or different techniques than are used in machining in general.

Thanks again Guys, very much appreciated :thumbup: :thumbup:
 
fitzo said:
...Sadly, history is a long story of politics intruding in both science and religion, to the detrimant of everyone. One would think that knifemaking would be a straightforward enough activity to avoid it, but where there's money, status, and advantage on the line, BS & politics will soon follow.

That says more about human nature than anything else.
Click to expand...

Statements such as this gives me hope that it is not just me, that it is rather plain to see and other people are looking. Sometimes it feel like some strange science fiction movie, where you are screaming at the masses of vacant stares asking if anybody else sees what is obvious only to receive monotone suggestions that you imediately go to a re-education center so that you may clear your thoughts and belong to the collective again. Thank you Fitzo for letting me know there is at least an underground resistance out there:thumbup:. Forget heavy metals in the calabash, politics has lobotomized most of our country much more thoroughly, than a chainsaw in the cerebrum.:(
 
As a friend of mine, another geologist, used to be fond of telling people, "Science is a verb."

The process is the reason the truth can be reached. Ask a question and look for answers. If one thinks he always has the answer, he had lost any scientific credibility he might have had.
 
man you guys are getting toooo deep :eek: :) which came first the product or the science, :D
I think science is trying to over come the work needed to produce good things through the absolute duplication of the works laid out before it.. if we keep our secrets science will never prevail :D

I found if My knives don't work right I did something wrong
and then I change things until it works to my likings .. :D
I really think a Rockwell range is a guide line for new guys to shoot for until they get to know their trade well and the ability's of their working with steel,,..good home work in the shop and then using that homework well should bear good fruit for them. just my 2cents..
 
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