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EDGE RETENTION/ROLLING PART II
#21
Ask and you shall receive Bud:

                                

Rare (HRC50), Medium Rare (HRC54), Medium (HRC58) and Well Done (HRC62)

And just in case you missed what they looked like before going on the grill:

                                 
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#22
Here's a little sneak peek at our testing with one of the twelve A2 heat treated samples.

We were very interested in a couple of things that we can quickly and easily test for; (1) Can we, in fact, sharpen edges,  then send them to heat treat and expect to receive back still-sharp edges and (2) do these pre-sharpened, post heat treated edges, roll?

If the initial results reported below hold up through the balance of the testing, then we are well on our way to  answering both of these questions .

                                   

We picked our #6 sample that was ground with a double bevel and then sharpened and deburred to BESS 340 and that number represents an average sharpness level across the edge. It was very difficult to obtain a consistent sharpness level across the edge working with unhardened steel. #6 was hardened to HRC50. Out of the box it measured 760. It was obvious that the steel was covered in heat treat residue and hand stropping on plain leather began to remove the residue. We stopped stropping/cleaning at 420 because that was good enough for this intended short test. It was obvious to us that edges can be pre- sharpened before heat treat without disastrous consequences. We could have applied our Kally's leather belt to the cleanup process but we didn't want to introduce any power elements to this particular test. Later we will  see if the original sharpness level can be returned to this edge without the use of abrasives. 

We know, from previous Stage I (one cycle) tests, that edges sharpened to 400 roll. Not nearly as much as 150 edges but they still roll. The question was, will this 420, pre-sharpened and post heat treated, edge roll as well? The answer is yes, it did. To be honest, we all predicted, here at EOU, that it wouldn't...but it did. After a Phase I test (five back and forths over the edge (one cycle)) the edge sharpness was reduced to 480. After four additional cycles it rolled to 590. This is all very much in line with what we have witnessed in previous tests with edges sharpened to the 400 level. But... did it roll or did the apex just crumble as a result of the lateral force applied to it? We have two good tests that answer that question. (1) Edges that have rolled 170 points often can be detected (felt) with a fingernail. This roll was easily detected with a fingernail on the rolled section of #6's edge. (2) Edges that have rolled less than 300 points can usually be stropped straight again and returned to at or very near their pre-roll sharpness levels. After edge straightening, our 590 edge then measured 380 or forty points better than where we began the test. We attributed (best guess) the improvement to simply more removal of  gunk on the edge. We anticipate that further stropping would likely return the edge, at least, to it's pre-heat treat level and we'll let you know later where it did finally end up.  

So we have, what we think, are some pretty telling initial results that very well might have ramifications upon other areas of the sharpening debate. We have plenty more edges to test and we'll see if these initial results hold across the board. We also have other factors to test for including the original goal of these tests, how rolling of sharpened edges is affected by HRC level. Curiosity got the best of us with this first short test. From here on out we'll have to get a little better organized.
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#23
Here's the bookend to our HRC50 #6. It's HRC62 #11. Stropped/cleaned to 190. After one cycle - 320. After 4 additional cycles - 455. Applying the leather belt on the Kally to #6 yielded a final score of 220. Applying the leather belt to #11 improved the score only slightly - 185. Here's a picture of #6 and #11 taken together. The buildup on #6 is noticeably greater. We assume as a result of higher tempering temperature.

                                                   
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#24
I had hopes that this test was going to give us some clues on how to reduce edge rolling but it doesn't look that way. If heat treated edges roll and soft edges roll and hard edges roll its starting to look like all edges just roll. On the bright side, maybe we can forget about wasting money on $150.00 knives. Still looking forward to the rest of the tests and thank you to EOU for the time spent testing all this.
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#25
That’s some very interesting stuff there Mr. EOU.  

I am aware that the blades used in previous rolling tests referred to here for comparison were commercial knives, meaning that they were originally factory hardened and sharpened.  The blades were then sharpened again on a Kally before rolling tests were performed.  So the commercial blades were sharpened after hardening.

This latest test data shows that steel edges that have been hardened and not sharpened after hardening roll approximately the same amount as the previous blades that were sharpened with a Kally before roll testing.

While these results are preliminary and obviously based on a very limited data set, they indicate that sharpening on a Kally does not weaken the edge, or increase the propensity of the edge to roll.  Any weakening or softening of the edge caused by sharpening with a Kally is negligible.

If it is true that sharpening with a Kally does not decrease edge strength, we could further conclude that hand sharpening with a stone would have similar results.  No better or worse than sharpening on a Kally.  Obviously, hand sharpening would not actually increase blade edge strength, so basically the same as sharpening with a belt grinder.

Of course this is considering that the blade is sharpened normally, and not carelessly and grossly overheated when sharpening on the Kally or any other belt grinder, but given that, there is little or no difference between powered and hand sharpening as far as the final edge strength and resistance to rolling is concerned.
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#26
Those are some excellent results and great efforts for valuable findings.

Just to double check, was the original intent of this test to see if the process of sharpening changed the properties of the steel at the edge, making it behave differently to the rest of the blade steel? (and therefore potentially casting doubt over the validity of the results from the SET)

Of course careless sharpening will cause issues, but as long as the sharpening process does not introduce heat treat issues or work harden the edge, then it would seem these early results are suggesting that the SET results are indeed valid for directly checking the performance of the steel. One variable removed.
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#27
Thanks for the responses Bud, Grepper and Subwoofer. For Bud and Grepper your logic follows ours with regard to the evidence that has been presented to date. Both of you have recognized, however, that the information presented to-date is far from complete or definitive and that realization is much appreciated. If the following study data turns around or contradicts as we and our fellow outside SET testers progress with this study it would be far from the first time that a research project did a 180° (or a 90°) midstream. 

Subwoofer, the results we have obtained so far may be interpreted by the reader as they see fit but we guess that you are asking "how we interpret" the information gathered so far. So here goes:

You wrote "Just to double check, was the original intent of this test to see if the process of sharpening changed the properties of the steel at the edge, making it behave differently to the rest of the blade steel? " 

This is absolutely correct in reflecting our purpose.

Then you followed that sentence with this in parenthesis "(and therefore potentially casting doubt over the validity of the results from the SET)"

This was not our purpose. Let's just stick with the first part of your statement for a moment. We know that edge apexes behave differently than the steel behind the edge apex. We know that HRC60-62 edge apexes can be rolled past 90° and then returned to their original orientation and done so repeatedly. Edge apexes therefore demonstrate a level of ductility that the balance of the blade seems not to enjoy. Edge apexes also do not seem to demonstrate the general yield strength characteristics of the blade as a whole. Edge apexes, deflected a mere 10°, do not demonstrate elastic deformation properties (they don't return to their original state/position post deflection). The blade, as a whole does. So the question then is "why is this?" One theory was that the very act and process of sharpening the edge creates this ductility in the apex. If this were true then two possibilities came to the forefront; "plastic deformation" and/or "foil properties". The very act of grinding an edge can be defined as an exercise in plastic deformation so the question then becomes " does the plastic deformation that may occur during the grinding operation change the hardness characteristics of the steel?"  Soft steel is ductile, hardened steel is more brittle. This seemed to be a logical place to begin so we designed an experiment where the hardening process was conducted post sharpening. What are the initial findings of this experiment? Post hardened edges still demonstrate significant rolling characteristics. At first blush, it would appear that plastic deformation during the sharpening process is not, at the least, the major contributor to edge rolling. What remains? Foil properties and/or some physical property that we have yet to consider.

Please remember that that this test was merely a subset of the work we hope to achieve. We think that the inference you took away from the test is an interesting one and worthy of further thought so thank you. We look forward to your own findings with the SET tester and thank you very much for contributing to this work with your thoughts and questions.
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#28
All very interesting EOU. I'll reserve most of my thoughts for when the tests are complete but I can assure you that I have been following along faithfully because this could all have very big implications for my company. Thank you to everyone with SET testers for your work!
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#29
From its inception it was hoped the SET could provide insight into a variety of questions.  Some examples are:

Does simply sharpening increase edge ductility?
Do different methods of sharpening, i.e., powered vs hand, produce different results?
How does steel hardness relate to rolling?
How does initial sharpness relate to rolling?
How does bevel angle relate to rolling?

So the SET was not designed with only one use in mind, but rather as a multipurpose instrument that could be useful in pondering a plethora of puzzling questions.
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