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Sometimes you don't know as much as you think you know

Posted by CliffStamp 
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Sometimes you don't know as much as you think you know
March 12, 2014 03:08PM
Awhile ago I had one of Kyley's AEB-L knives which didn't have the performance of this other AEB-L knives and in fact behaved very similar to a generic 420HC blade from Buck for example. I wrote about this on the forum. Now to be clear Kyley also had problems with the knife in sharpening it and thought there was an issue and sent it to me to have a look at. I noted :

-edge retention on cardboard was lower than expected
-did not take a high sharpness as well as expected
-damage was onset more than expected

Kyley then sent two more knives, unlabeled to review against it.

I had a look at these and they were not significantly different from each other, but both were very different from the first one :

-edge retention was higher but inconsistent
-edges could suffer chipping and reduce sharpness in spots to essentially zero

They thus appeared to be stronger but more brittle. Kyley later revealed that one of them was from the same batch as the first but just had an additional temper and one was unchanged. I would not expect a second temper to do anything so I was satisfied that they were consistent with each other. However they were different from the first.

Now to be clear I am running much smaller bevels than most, 6 dps usually with micro-bevels and the same is constrained to the depth of the micro-bevel so this isn't catastrophic - it just isn't how AEB-L would be expected to behave. Kyley did have these HT'ed differently, but the change me made (no snap temper) should not if done properly affect the performance.

The question I have now - "Is the difference I have seen true?" I am fairly confident in the results due to the way they are done but nothing is ever 100%. I am going to do a few more experiments to verify in a few other ways.
Re: Sometimes you don't know as much as you think you know
March 12, 2014 07:41PM
Im very interested to see how this ends, in testing and in regards to "first" one..
Re: Sometimes you don't know as much as you think you know
March 25, 2014 12:49AM
As an update, just to give some insight into the reality of experimentation because often all you see are the end results which are perfectly presented and everything is well supported and documented - however getting there is a muddy and complicated mess.

--

I have been doing some hemp cutting with an Opinel and finally found a knife which can actually be damaged on hemp (!). A zero ground opinel took damage twice in a row on hemp cutting, just very light folding of the micro-bevel - but damage in any case. However the damage happened in the exact same place twice in a row, that is unlikely if it was just geometry and the cross section as it is the same cross section everywhere and thus random stress loads should induce random cites of damage.

Now it could be an isolated fault in the steel, that is what everyone jumps to, but that is really rare (and difficult to check) so it isn't a good hypothesis to start with as it is difficult to move beyond it. As I was flattening the edge (grinding it into the stone) on the Bester 700 it came to me that stone was not perfectly flat (derp) -AND- the edge could be picking up a slight recurve because it was taking the inverted shape of the stone. I then did a light pass on a DMT and sure enough the edge was not getting uniformly hit by the stone, it had a slight recurve.

Because the light recurve was just that, barely visible, it would actually be destressed, just not as deep as the rest of the edge and thus what was happening was that the stress was building up and not being completely removed and after three runs on the hemp the edge started collapsing in that area. I then flattened the edge (properly) and will check this the next time I run the Opinel on hemp. I also figured out why Opinels often take this kind of recurve after use because it becomes very difficult to flatten the edge right at the start as the cap gets in the way. I dropped the blade slightly to remove that problem as well.
Re: Sometimes you don't know as much as you think you know
March 25, 2014 01:50PM
What do you mean by dropped the blade?

Have you let anyone else use the opinel? It could be that they cut through something that stressed the edge there quite a bit.
Re: Sometimes you don't know as much as you think you know
March 25, 2014 03:03PM
Yes, and that is always a possibility, hence the edges are destressed and checked for evenness of response. But as I noted if the stone isn't true-flat then the edge could also be not flat and it would appear to be if you just looked at the reflection of light being even in response.
Re: Sometimes you don't know as much as you think you know
April 04, 2014 03:06AM
Here is the experiment :

-using a Surefire Delta with a zero grind
-cut the bevel off with 2 passes into a coarse benchstone
-apex it with the CBN rods

repeat the last two five times. The results as number of passes per side are :

CBN : 11, 11, 20, 17, 29, 26

Now this makes sense as you would expect as you keep apexing the bevel it gets wider and then takes more time to apex.

Now with the diamond :

-zero grind the Delta on a Bester 700
-cut the bevel off with 2 passes into a coarse benchstone
-apex it with the diamond rods

What would you expect as the results, I bet it isn't this :

Diamond : 3, 7, 10, 14, 20, 31

The diamond rods apex the bevel much faster initially, and so it would appear that the diamond rods are in fact more aggressive. However I don't think this is the case because at the end note the pps numbers almost equalize. I think that the reason for this is that the second time I flattened the Surefire I took out a small curvature near the edge and thus the diamond rods had less work to do initially.

This seems to be indicated by the pictures of the microbevels :

CBN :



Diamond :



Note how the diamond one is much more narrow initially. Now if my hypothesis is correct then when I flatten the Surefire and repeat this that dramatic early difference will disappear. If it doesn't then that would be kind of interesting, but I don't think that will happen.
Re: Sometimes you don't know as much as you think you know
April 14, 2014 01:01AM
Another experiment that didn't go as planned.

I had been doing a lot of cutting with Joe's 1095 blades and it is very time consuming, I do two trials with each blade per run (hemp and cardboard) and it takes hundreds of measurements per run. To take a break I decided to do a much looser comparison.

I wanted to see if the difference in edge retention as a function of finish would be large enough to see readily with just very coarse observations. The plan was very simple :

-apex the blade on the Havalon with the Sharpmaker rods (of each grit)
-cut 3/8" very dirty polyethylene rope until it could not perform basic cutting

There were no quantitative measurements of sharpness, just standard sharpening and a quick check on paper. For the test cutting I was planning to stop when it could not slice thin expanded polystyrene without tearing it. As I was using a rope so dirty if I dropped it you could see the dirt / dust on the floor and the Havalon uses a basic stainless steel and it takes a decently sharp blade to slice foam without tearing it I figure I would quickly be able to compare all four grits on the Sharpmaker (diamond, CBN, medium and fine rods) and do a very runs to verify.

Not even close.

It took 200 cuts with the CBN finish before the blade even stopped shaving and it was just barely reflecting light then and could still slice the foam, no issues. I then jumped to the fine rod and it could do the same.

While it didn't allow me to check what I wanted to check, it should make the basic point that anyone claiming to need something beyond an extremely basic steel to do regular cutting simply is showing they can't sharpen a knife as I doubt few people are needing to make 200+ cuts into dirty synthetic ropes.

As an aside, it took < 5 pps with the CBN rods to restore it to the initial sharpness.
me2
Re: Sometimes you don't know as much as you think you know
April 14, 2014 01:15AM
Thanks for that. I'm still a little warped by that thread from BFC about 300 cuts and it didn't cleanly slice paper anymore. I'm planning to pick up some 3/8" rope from Home Depot tomorrow and try it with the Hampton Forge Gyuto I got from my wife for Christmas. 17/20 dps then on to the 12/15.
Re: Sometimes you don't know as much as you think you know
April 14, 2014 01:20AM
Yeah that is interesting, when I was first looking into edge retention I was cutting cardboard and figured that when it would not slice copy paper any more I would stop. I ran out of cardboard. And made 250' of strips maybe more I would have to check.
Re: Sometimes you don't know as much as you think you know
April 14, 2014 03:18AM
If you are using clean rope, even simple blades cut through it easily. If you are struggling to make a few hundred slices then the blade simply isn't sharpened properly. For some perspective, forget about the rope cutters who have become popular in recent years and go back to the OG's of rope cutting, Boye, Fikes and the like. Those guys did *thousands* of rope cuts (on much thicker rope) and would get blades back to razor sharpness in literally seconds.

In order for me to see a difference in a small amount of rope I have to measure the sharpness in a way which can detect very small changes in sharpness and even then I have to do hundreds of cuts. To even get a reasonable level of confidence on just one blade with one edge finish at one angle I need 30'. If I want to check just a few angles/finishes I have buy hundreds of feet, and again that is just one knife.



I could cut up that entire roll with that knife and in total I would spend less than a minute sharpening it throughout the process.

Even buying it in bulk I am beginning to understand why I stopped using hemp as if I used this as my main medium I would spend enough on hemp in one year to match the cost of a custom damascus sword from Kevin Cashen.



Edited 3 time(s). Last edit at 04/14/2014 03:24AM by CliffStamp.
Re: Sometimes you don't know as much as you think you know
April 14, 2014 03:23AM
Why does it matter what side is up?
Re: Sometimes you don't know as much as you think you know
April 14, 2014 03:28AM
Quote
Mark a
Why does it matter what side is up?

It is round, it has to be on one of the flat sides to stack stable. It doesn't matter which one, but if you put a <> arrow on it then it confuses people, if you put a -> on it everyone knows how to follow it. The fact that you have to tell people to stack cylinders on their ends is another issue.
Re: Sometimes you don't know as much as you think you know
April 24, 2014 09:36PM
Just for comparison, how much is that rope, lets say 1m?

Here in one store where i found it, it was something like 2.50usd for 1m
Re: Sometimes you don't know as much as you think you know
April 24, 2014 09:39PM
If you buy it off the shelf it can be as much as 0.81/ft, I paid about 0.2/ft .
Re: Sometimes you don't know as much as you think you know
July 22, 2014 02:00PM
I recently did a comparison of edge retention for slicing on abrasive media on Stanley blades : [www.cliffstamp.com]

As a complement to this I planned on doing an edge retention comparison on push cutting on a hard and non-abrasive media, to be particular, thick plastic (screw ties). I figured a simple comparison using the TCE statistic and initial sharpness :

-four runs with the as-boxed blades
-four runs with the CBN blades

I expected that the CBN would be behind here because the finish is much more coarse and while it does well for slicing it would not do that well for push cutting. However the experiment hit a snag because :

-cutting thick plastics causes a very low rate of blunting
-the blunting is not at all consistent

I needed to make a 1000 cuts into the screw ties (similar to common zip-ties but only heavier) to even produce a significant loss of sharpness and even then it was only on certain parts of the edge, the vast majority of the edge, > 90% is still almost as boxed in sharpness.

--

This is why planning experiments is good, but you really need to actually do work to develop the proper experiments because on paper it can often look very simple but in practice it isn't. I still think I will see a difference with the CBN rods but the scatter is so high that it might not be nearly as obvious as I expected.
Re: Sometimes you don't know as much as you think you know
July 23, 2014 03:17PM
Quote
CliffStamp

I expected that the CBN would be behind here because the finish is much more coarse and while it does well for slicing it would not do that well for push cutting.

Ha, this didn't happen at all.

The initial sharpness is lower however the edge retention and durability are way higher, so much so I can't even determine the stopping point on the CBN rods even though I went 4X longer I still didn't see the type of degradation on the CBN rods as I did on the as-boxed finish. Now I think I understand why, but I have to repeat it (unfortunately) just to make sure it stabilizes.
Re: Sometimes you don't know as much as you think you know
July 23, 2014 08:28PM
Ohh, a cliff hanger. I'm excited to here the explanation. (No pun intended either)

_______________________________________________________________________________________________

Always in search of a good choppa'
Re: Sometimes you don't know as much as you think you know
July 24, 2014 05:26PM
Re: Sometimes you don't know as much as you think you know
July 29, 2014 05:21PM
I had attempted to do edge retention comparisons on wood before, but it takes a LONG time as wood isn't abrasive, just take a look at the wood comparison here : [www.cliffstamp.com] . I did 1500 slices and barely made any impact on sharpness.

In line with the stanley blade work I was curious if I used those and used a pretty horrible finish for it, the CBN, could I see a significant rate of blunting, well the answer is no you can't. It took 3500 slices into pine before the edges lost the ability to shave, I repeated it once (did two runs total), and measured the sharpness cutting thread as well before and after.

Now the curious thing is how will the medium finish compare, I just need to find the right movie to watch as it could take much longer for the edge degradation with that finish.
Re: Sometimes you don't know as much as you think you know
August 05, 2014 01:03PM
I have not updated the cardboard table in awhile and the reason being was that the results became erratic and toward to low end. It took me awhile to figure out what was happening as I had to sort out the new data and figure out what was correlated to the change.

To blind the results I often give the edges once prepped to friends who I have shown how to apply the final micro-bevel. They then apply that and they don't know anything about the knives/steels so it eliminates one source of bias.

Well one of them took it on his own initiative to see if I really was doing what I said I was doing and would change the angle dramatically on occasion to see if I would pick it up. As he didn't do it consistently it took awhile before I could sort it out.

Now it is impossible to tell, even under high magnification the edge angle because it is literally only micron's wide and if you do a decent sharpening job it will be just as sharp but it has a significant effect on edge retention.

On the positive it is another flag about the data being unbiased and accurate but now I have to go through all the data and separate out the ones from the time he started adjusting the edge angles which was months ago.
Re: Sometimes you don't know as much as you think you know
August 05, 2014 01:28PM
I think I might have perceived that as less than positive.

www.theflatearthsociety.org

BIGFOOT FINDS YOU, YOU DON'T FIND BIGFOOT!



IT IS THE E-NEP THROWING BROTHERHOOD
Re: Sometimes you don't know as much as you think you know
August 05, 2014 01:32PM
Do they have those Jack Links Sasquatch commercials up there in Canada?

Because that's how I would have acted when I found this out:

[www.youtube.com]

_______________________________________________________________________________________________

Always in search of a good choppa'
me2
Re: Sometimes you don't know as much as you think you know
August 05, 2014 08:08PM
That was really funny.
Re: Sometimes you don't know as much as you think you know
August 06, 2014 01:34AM
Quote
Mark a
I think I might have perceived that as less than positive.

As an u-grad I was assigned a very simple experiment :

-mix two gasses
-wait for them to stabilize
-record a set of spectra
-note the stabilization time

I knew the stabilization time was about a week. The procedure is :

-run a data log every day (takes five minutes)
-when they are stable run five logs and produce an average

This is just used to check some basic abilities (measurement, equipment control, etc.). I however could not get it to stabilize. I spent an extra week and finally went to the grad student and noted I was doing something wrong but didn't know what it was it was like there was some random thing changing the gas on a random basis. I had checked the system for leaks, I had checked all the equipment and swapped it out piece by piece. He was doing it. He would come in, bleed out some of the mixture and put in fresh gas periodically.

He wanted to ensure :

-I would actually follow the procedure and not just wait a week and run five traces or just make up five traces and do nothing
-that I would attempt to solve it and not just spaz out immediately

It is easy to make claims, it is easy in fact to do some work, it is really hard to figure out how to do the work so it means you can know something. A lot of the things you have to do are kind of annoying but that is the price for being able to know.

I like to know things.
Re: Sometimes you don't know as much as you think you know
August 06, 2014 02:25AM
Quote
Cliff
-I would actually follow the procedure and not just wait a week and run five traces or just make up five traces and do nothing
-that I would attempt to solve it and not just spaz out immediately

Was he concerned that you were a liberal arts major that had snuck into the department?
Re: Sometimes you don't know as much as you think you know
August 14, 2014 12:16AM
In the Washboard trials with the #1260 Mora on Pine I thought I had discovered something interesting :

-the first round the edge went from the Bester 700 to very high push cutting sharpness quickly
-cleaning the paper and applying the compound new took much longer, so much that I stopped and recut the edge on the Bester
-I then put on new paper and put compound on it and it responded much faster, similar to the first round

I thought then that I had seen how a compressed paper is producing a flatter bevel (or maybe the compound doesn't load as well on compressed paper). However in the third round when I put on new paper again it was much longer to sharpen and when I kept that paper and just reloaded it then the sharpening time was no different.

In short all I was seeing is just a difference in initial sharpness from the shape/condition of the edge off of the Bester. However for about 2 minutes I thought I had discovered something interesting.
Re: Sometimes you don't know as much as you think you know
September 12, 2014 04:24PM
Re: Sometimes you don't know as much as you think you know
September 12, 2014 04:43PM
There are laser systems which are even used in process : www.lzh.de/sites/default/files/9_ps-pho_laserdressing-wz.pdf
Re: Sometimes you don't know as much as you think you know
September 12, 2014 08:04PM
Quote
CliffStamp
There are laser systems which are even used in process : www.lzh.de/sites/default/files/9_ps-pho_laserdressing-wz.pdf

interesting pdf thanks for posting it Cliff... But the issue is that while that may work to some extent on certain blades for limited sharpness, I do not think it would even be possible to do on a knife blade without destroying the edge several microns deep into the edge itself. A laser works off of melting/burning whatever it is cutting through. If it did this to establish a knife edge then the edge would be damaged and you would have to remove the damage by hand. I have had an offer to have knife blanks lasered out for me but I am extremely leerie of doing this... and this is pre HT! This will change the micro-structure near the burn marks I believe... that is one reason why Kevin Cashen says that you don't want to heat your knife blade up while grinding pre-ht to where it changes colors.
Re: Sometimes you don't know as much as you think you know
September 13, 2014 03:18AM
I wouldn't jump to say its impossible so fast.