VIDEO: Polish and Reprofile (Part 2) -- Edge degradation

unit

unit

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The first video explored how stock and reprofiled edges performed on a VERY basic push cut through rope, this video takes a look into how the edges perform after some cutting intended to degrade the edges. I will let you draw your own conclusions. Thanks for your interest, hope you enjoy!

http://www.youtube.com/watch?v=4l2fItEFXFA

The first video was discussed in this thread.
 
I like your testing... would you consider doing some slicing cuts and then testing the edge? I think it might be interesting to see the result.

cbw
 
I liked it. I can't fully understand which knife bevel degraded the "most" or "least." It appears that the 20* inclusive won out. Is that correct?

I used to think those FRN Endura 4's were not too cool compared to the pricier G-10 FFG version. Now I want to test mine out on my daughter's, boyfriend's car. It looks almost effortless and a fun prank (kidding) . :D :thumbup:

I'd like you to interject some of your personal opinions on the test - if not on the video - then here for us if you'd care to.

Good job!
 
cbwx34 said:
I like your testing... would you consider doing some slicing cuts and then testing the edge? I think it might be interesting to see the result.

cbw
Click to expand...
I am sure I could try something like that at some point;)
 
cziv said:
I liked it. I can't fully understand which knife bevel degraded the "most" or "least." It appears that the 20* inclusive won out. Is that correct?

I used to think those FRN Endura 4's were not too cool compared to the pricier G-10 FFG version. Now I want to test mine out on my daughter's, boyfriend's car. It looks almost effortless and a fun prank (kidding) . :D :thumbup:

I'd like you to interject some of your personal opinions on the test - if not on the video - then here for us if you'd care to.

Good job!
Click to expand...

I'm on my phone for the rest of the morning but I will share some thoughts when I get home.
 
unit said:
I'm on my phone for the rest of the morning but I will share some thoughts when I get home.
Click to expand...

No need to really, I was going to post back. I watched it 2 more times to let the numbers sink in, and IMHO the 20* inclusive was just flat out sharper and retained the same or better than the others.

That doesn't address chipping and stuff like that, but I don't cut stuff that has hidden particles etc. so for me the 20* is the best slicer and has the best edge retention for the test you performed. :)
 
Looks to me like the thinner bevel might degrade a little faster than the others, BUT, even after dulling some, its still above the other blades. Basically, you cut the entire sidewall out of a tire before the 10 degree blade even made it to the starting force of the other knives.
 
unit not only an impressive informative tests but a totally new medium to show results from. i'm sure you are aware of this variable , but i thought i would mention it before a flood of comments came thru. all of us certainly should realize [as yourself does] that steel belts, multiple plies, tire size are variables that effect results. i'm sure all the testing you preformed was on identical type tires.two fantastic facts come from your tests.
tires are free for the taking in most areas
your tests can be performed with a minimum of effort & time
i'm certainly gratified by your initiative & original medium in this session which certainly shows how important edge bevels & polishing can affect edge degradation .although some persons may chip at the empirical factors ,i for one can see a positive correlation of the factors you choose to demonstrate. thank you dennis.
 
Another nice test, Unit. I'm still trying to wrap my head around it. Conventional wisdom would expect the 20-degree edge to dull more quickly, but the medium being cut plays a big role. Rubber is very soft, so that is a factor. But I don't know what kind of belts are being cut within the sidewalls and what they could do to an edge.

Cool stuff to think about. And thanks for cushioning the knife edge after the string cut. Using metal as a back stop in your first test was hard to watch.
 
Several users have reported better edgeholding with thinner edges, as long as the edges are not used to cut material that will damage the edge. This is the reason for the general trend toward higher hardness/strength and thinner edges with increasing toughness.
 
DennisStrickland said:
unit not only an impressive informative tests but a totally new medium to show results from. i'm sure you are aware of this variable , but i thought i would mention it before a flood of comments came thru. all of us certainly should realize [as yourself does] that steel belts, multiple plies, tire size are variables that effect results. i'm sure all the testing you preformed was on identical type tires.two fantastic facts come from your tests.
tires are free for the taking in most areas
your tests can be performed with a minimum of effort & time
i'm certainly gratified by your initiative & original medium in this session which certainly shows how important edge bevels & polishing can affect edge degradation .although some persons may chip at the empirical factors ,i for one can see a positive correlation of the factors you choose to demonstrate. thank you dennis.
Click to expand...

Thanks for the kind words and great points.

Tires would be a poor test media in that they are highly variable from one tire to the next. Even seemingly identical tires will have different rubber compounds (which are proprietary) and components like carbon black are used in different fractions (carbon is quite abrasive).

I tried to use some common ground here...there is exactly one tire in the video and we can assume that construction of it is consistent, and each cut was the same size (roughly).

The intent was not to establish a way to compare these with other knives, but rather to subject all three of these edges to the same level of stress (ideally). The last tire cut in the video is the back side of the same tire...I was a little surprised at the results and wanted to see what the thinnest edge required to dull.

I was and am surprised at the result. It is still "hair popping" sharp.
 
Twindog said:
Another nice test, Unit. I'm still trying to wrap my head around it. Conventional wisdom would expect the 20-degree edge to dull more quickly, but the medium being cut plays a big role. Rubber is very soft, so that is a factor. But I don't know what kind of belts are being cut within the sidewalls and what they could do to an edge.

Cool stuff to think about. And thanks for cushioning the knife edge after the string cut. Using metal as a back stop in your first test was hard to watch.
Click to expand...

Thanks. Rubber is soft, but it contains abrasive compounds for the purpose of extending life, reducing wear and improving toughness (even on sidewalls, so they do not scuff as easily on curbs and such). There are several types of rubber used (in layers) and the compounds are proprietary. This particular tire has polyester belts (fabric) in the sidewall.

As I said in another response, tires are variable (I have some with Kevlar belts, some with silica compounds similar to sanding grit, and various other materials). It is probably not worthwhile to try and compare one tire to another, so I used only one and tried to stress all edges the same way (same length of cut and same tire) and then look at how much of an impact it made on the cutting rope.

You are right, what you are cutting and how you are cutting it will likely be GIANT variables in how an edge performs and lasts. This demonstration (like most) is very limited in that capacity.
 
I think the test should be looked at "by the numbers reported" talk of what different tires and compounds would produce really is not important.
unit tested everything on the exact same tire, so there really were no variables to consider other than the numbers.

A proper and well exceuted test of 3 exact knives with his "3 edges" criteria, tested on the same media - perfect. :thumbup:
 
Twindog said:
Conventional wisdom would expect the 20-degree edge to dull more quickly
Click to expand...
I don't know where we got the original notion from. How many people knew what the edge angle of their knives were 20, 50, or 100 years ago? How many know now? Is 30 appreciably more robust than 20? Is 20 too acute, or too obtuse to get good cutting performance and edge life? Are the factories sharpening to a consistent edge angle, is it predetermined, and what is their criteria? How important is hardness and alloy? How consistent are these factors for the knives in people's hands and pockets?

And I like to think of this when the question comes up. Take a kitchen knife, with a 20, 30, or 40 degree edge. Do some cutting with it, and try to see how much the edge wears/dulls. Now flip it over and 'cut' with the spine. How quickly does it 'dull'? Well, not at all. But how well does it cut? There's a tradeoff at both ends, and the trick is finding where the tradeoffs balance to your liking. There are quite a few guys with single digit per side edge angles. It was also calculated that at least one maker's competition cutter was sharpened to about 7 degrees inclusive.
 
if i understood units demo he was'nt trying to establish that any certain bevel was optimum.only that for 3 identical knives of same alloy but with different bevels & polishing cutting the same medium demonstrated interesting variibles in final results. unit did'nt announce any set in stone conclusions he only listed his personal findings. leaving members to draw their own opinions from the test. certainly what followed shows how each member interpreted the sequence. dennis. one conclusion seemed to come from another planet.just my own somewhat biased opinion.
 
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DennisStrickland said:
if i understood units demo he was'nt trying to establish that any certain bevel was optimum.only that for 3 identical knives of same alloy but with different bevels & polishing cutting the same medium demonstrated interesting varibiles in final results. unit did'nt announce any set in stone conclusions he only listed his personal findings. leaving members to draw their own opinions from the test. certainly what followed shows how each member interpreted the sequence. dennis
Click to expand...

;)

I am enjoying learning from the comments here and elsewhere.
 
I really enjoy your video... thanks for your effort in making and posting it...
 
I really appreciate the comments and kind words.

I hope that the entertainment from these videos pays forward in some small way the incredible amount of free knowledge that has been shared with me on these forums! The way I see it I have a lot more paying to do!
 
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