VIDEO: Hard cutting comparison/demonstration

unit

unit

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Nov 22, 2009
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I have been playing around a with thinning out edges lately. This Stretch II seemed to offer the opportunity to try something really thin, so did.

While the results were impressive for push cutting through light rope, they seemed a little more pronounced when I performed some harder/heavier cuts. Hope some of you find this interesting.

It is not intended for conclusions beyond a demonstration of how this particular knife compares to other (perhaps known) blades that some of you may be familiar with.

I attempt to compare a well known example of a brand new Spyderco knife (the Military) to two other Spyderco models that were modified (not stock). One is the Stretch II that was reprofiled to 13 degrees inclusive, the other is an Endura that was reprofiled to 20 degrees inclusive.

Originally, I was not going to post this here, but the recent discussion I had regarding "hard use" and "hard cutting" in this forum made me change my mind. Make no mistake, I am not claiming anything regarding hard use here, I think this demonstration shows the value of thin edges for performing some types of hard cuts...that is all...nothing more.

http://www.youtube.com/watch?v=tTTpFqO-viI
 
Very cool, Its a amazing thing the difference you can make just by playing with the bevel. Hopefully all of this is has given you some useful information. Thanks for sharing :thumbup:
 
knifenut1013 said:
Very cool, Its a amazing thing the difference you can make just by playing with the bevel. Hopefully all of this is has given you some useful information. Thanks for sharing :thumbup:
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It has given me some very useful information...and so have you. I have learned a lot from your posts here, Thanks for that!
 
Nice video. How well does ZDP189 hold up with a super thin edge like that? Does M4 hold up as well?
 
mjolnir74 said:
Nice video. How well does ZDP189 hold up with a super thin edge like that? Does M4 hold up as well?
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I can not answer that yet...I just do not know.

I can tell you that ZDP holds up better than many steels probably would at this angle...but I expect that any steel taken this thin will give up some retention (compared to wider angles) over a wider range of uses. No surprise there...

FWIW, I inspected all three edges under a lens after this video was made. All three had compressions/rolls (not visible without the lens) from this cut...and all three appeared to be "about the same" in terms of extent of damage. I attribute it to lateral stresses at the point of contact (the edge "bit" into the rubber, then that slack pulled out of the loop and imparted a slight lateral stress one way or the other...that is conjecture, but it seems like a logical guess).

To go a bit further, these compressions/rolls were only noticeable when doing long cuts in newsprint...there was a very slight snag as I passed the area of damage.

The VG-10 was easiest to repair for what that is worth!?!
 
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love the way you set up your tests. makes comparing the edges easy. also kevlar is really strong, i never realized until i tried to cut kevlar fishing line.
dennis
 
Very interesting, enjoyed watching your video. I was too scared to go as thin as you did on your zdp stretch but I just may have to try it out :thumbup:.
 
Nicely done unit. As one peels back the onion , more is revealed.

We make mules of the same size. We have a dedicated grinder set up to grind the mules with the same edge thickness. We have a heat treater that works with the foundry we're testing for. Our guys in finishing are really good. We always use the same CATRA paper to keep the medium consistent. We use a large Goniometer to determine angles and we have found that generally the thinner edge will cut better.

Thanx much for the effort.

sal
 
Nice, video man. Well thought out and very well laid out. Really liked the way you did the details about knife and edge/bevel before each cut and the numbers at the end. Very well done.

I noticed that from the 30 inclusive to 20 inclusive it was 10lbs less, then from 20 inclusive to 13 inclusive it was also 10lbs less. From 30 to 20 is essentially 1lb less per degree and then in the jump form 20 to 13 somewhere in there is a tipping point whereby the difference accelerates to greater than 1lb per degree. Very interesting and I'd be willing to bet the cut off point is around 15 inlcusive at that point is where you start seeing the gain greater than 1lb per degree. It would also be interesting to see the point whereby the law of diminishing returns begins, meaning that less what ever the greatest ratio of degree to lbs force is starts to go back the other way and it no longer pays to sharpen past that degree? Or perhaps it just keeps increasing to zero degrees or very near zero.

Thank You
 
Sal Glesser said:
Nicely done unit. As one peels back the onion , more is revealed.

We make mules of the same size. We have a dedicated grinder set up to grind the mules with the same edge thickness. We have a heat treater that works with the foundry we're testing for. Our guys in finishing are really good. We always use the same CATRA paper to keep the medium consistent. We use a large Goniometer to determine angles and we have found that generally the thinner edge will cut better.

Thanx much for the effort.

sal
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Thanks so much, it is nice to hear from you. I enjoy learning more and more about these things (peeling the onion, so to speak...I have quite a few layers to go).

I would like to have access to some more Mules (I got into this a little late relative to the Mule project).
 
That was incredible...I guess you could have guessed at the results, but to see the process play out was fantastic. Thanks!
 
unit said:
Thanks so much, it is nice to hear from you. I enjoy learning more and more about these things (peeling the onion, so to speak...I have quite a few layers to go).

I would like to have access to some more Mules (I got into this a little late relative to the Mule project).
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You are most welcome. Knives have much depth; steel, history, design, materials, etc. each is a cavern with many tunnels.

We make about 4 mules per year. They were the closest we could get to actually having real world testing on different steels. We've finally got the foundries on board so getting different steels will be easier for a couple of years.

sal
 
Great stuff, Unit. Thank you.

Are you sure the edges rolled slightly because of the cuts and not from slamming into the cushion. It sounded like hard strikes to the cushion.
 
Twindog said:
Great stuff, Unit. Thank you.

Are you sure the edges rolled slightly because of the cuts and not from slamming into the cushion. It sounded like hard strikes to the cushion.
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Thanks a lot.

I think that based on the shape and size of the deformations, they were not likely from something flat and broad like that rubber pad.

You are right though, the blades pounded into it pretty hard! I would not want anything between those edges and that pad!
 
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