about edge retetion testing

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i found this rope cutting test interesting. he uses thick manila rope. and after only 5-10 cuts the edge is finished.

i can find manila, hemp, sisal, jute rope.
manila and hemp is about 15€/meter though for the thick stuff. 32-36mm
sisal only goes up to 16mm
jute i can find in 30mm+ for cheap. about 30€ for 15m

would any of these fibers be worse or better than the others?

I would like to avoid the thin ropes because then you end up doing several hundred cuts even for a global (since the blades/edges are so thin, compared to other regular knives).



 
also guys, where does one draw the line of "not sharp" anymore?

i just put a shapton 220 edge on a fiskars, no strop, no nothing. and it slices thin notebook paper cleanly...
now most people would not regard a 220 grit edge as particulary sharp.

so having the point where it stops slicing paper as the reference for dull might be a bit optimistic? or? for kitchen use i mean.
 
There are several dulling mechanisms for knives including wear, edge rolling/deformation, chipping, and corrosion. Slicing of abrasive materials seems to follow similar trends regardless of whether it is cardboard, rope, or CATRA paper. Despite the fact that push cutting does better with polished edges and slicing edge retention does better with coarse edges, the trends for wear are the same that I have looked at. There may be some finer details that aren’t well tested but overall trends are similar. Now if your knife is dulling by one of the other mechanisms then it doesn’t matter which wear test you are doing. You need to change the steel, heat treatment, and/or edge geometry to make sure you are losing sharpness to wear instead as that will last much longer than rolling or chipping.
 
panda said:
Neither rope or paper is food.
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no but my tomatos is probably very different to your tomatos, and i could even get 2 tomatos from the same lot that are different.
the variation is too wide with food to make it usable in some kind of test.
 
Larrin said:
There are several dulling mechanisms for knives including wear, edge rolling/deformation, chipping, and corrosion. Slicing of abrasive materials seems to follow similar trends regardless of whether it is cardboard, rope, or CATRA paper. Despite the fact that push cutting does better with polished edges and slicing edge retention does better with coarse edges, the trends for wear are the same that I have looked at. There may be some finer details that aren’t well tested but overall trends are similar. Now if your knife is dulling by one of the other mechanisms then it doesn’t matter which wear test you are doing. You need to change the steel, heat treatment, and/or edge geometry to make sure you are losing sharpness to wear instead as that will last much longer than rolling or chipping.
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what about plastic rope? i'm thinking this could be very destructive to high carbide steels.
 
pineapple skin
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This was the last fight I had with my Kato and when I realized we had to break up. Horrible.

I think Larrin is right about making sure you know what is the cause of poor cutting. Rolling and micro chipping are more prevalent in kitchen knives than is assumed in my opinion. A mix of sub optimal technique, hyper thin edges and wire edges makes retention info based on steel wear resistance claims dubious to me unless I have personally used the sharpening work of the person making the claim or somebody I trust vouches.
 
Michi said:
To me, it's dull once I can't effortlessly cut through the skin on a tomato, chilli, or bell pepper anymore.
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Same here.
If I gently touch the edge and can feel the knife biting into my skin, I know its sharp and good enough for work in the kitchen. If it's too blunt, or polished super-sharp, I won't be able to feel the bite and wouldn't like using it on the board.

It can be fun to mess about with polished silly-sharp stuff off the board though...
 
Yes I consider when it's no longer 3 finger sticky that is stolen needs to be sharpened. I will disagree though that a 220 grit Edge has a very sharp. It's just as sharp as a 10,000 grit edge if they were both sharpened correctly. The ten thousand grit Edge will be at a higher polish but it will not be any sharper.
 
Chuckles said:
This was the last fight I had with my Kato and when I realized we had to break up. Horrible.

I think Larrin is right about making sure you know what is the cause of poor cutting. Rolling and micro chipping are more prevalent in kitchen knives than is assumed in my opinion. A mix of sub optimal technique, hyper thin edges and wire edges makes retention info based on steel wear resistance claims dubious to me unless I have personally used the sharpening work of the person making the claim or somebody I trust vouches.
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example, take two identical knives. have chuckles sharpen one, and i sharpen the other one. i bet you quite a few people would be able to notice a difference purely from variation in peoples sharpening techniques. for example, my technique is very raw and not refined at all, quick n dirty. chuckles is the opposite.
 
inferno said:
also guys, where does one draw the line of "not sharp" anymore?
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It depends on what you want to do! But in the kitchen....

Michi said:
To me, it's dull once I can't effortlessly cut through the skin on a tomato, chilli, or bell pepper anymore.
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This is my litmus test!


But really.... an acute angle behind the edge on a hard steel with a laserish grind can be a bit like the Duracell bunny in a home kitchen.



panda said:
Neither rope or paper is food.
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Dont be naughty! :p



inferno said:
what about plastic rope? i'm thinking this could be very destructive to high carbide steels.
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It does not matter what material you choose to cut so long as the material is consistent between tests (as you point out). The decision amounts to changing one constant. I also doubt (by and large) it matters how much wear it imparts on the knife. You will either make more cuts to reach some end point or less. From the testers point of view, you may as well choose a more difficult material (within reason) so that you need to perform less cuts. Plastic is repeatable and cheap.

On that 'end point'.... going back to

inferno said:
where does one draw the line of "not sharp" anymore?
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That barely matters either - so long as it is measurable. Your goal is to quantify 'edge retention' by exposing a maximally sharp knife to constant wear until it reaches some lower sharpness (or bluntness) threshold. Again you will want to choose a test that is sensitive and repeatable enough to reliably illuminate the difference between knives in a manageable number of cuts. Of course... you'll probably have to hand wave the observer effect away :p
 
i got some polyethylene fake hemp rope 36mm. sharpened up my fiskars beater. its some krupp low carbon crap SS at 52hrc. took it to 4k on glass.
after about 30 cuts it started to tear paper in one spot. and after 70 cuts its tearing for the entire front half. but you can still make it cut clean if you know how to cut paper cleanly.
i'm thinking the edge is rolled more or less. either way 70 cuts with the shittiest steel is not good for testing. since this could translate to 700-7000 cuts with good steel. :)

i just sharpened up my handleless (it cracked during the last test) r2 kurosaki on the 4k. we'll see how it goes. i only got 5m rope and i have feeling i could be running out of rope soon.
i have to get some natural rope.

testing5.JPG
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testing2.JPG
testing1.JPG
 
inferno said:
i got some polyethylene fake hemp rope 36mm.
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I have a polyester secondary on one of my razor strops that is the most aggressive fabric strop that I have ever used. I wondered what could make polyester so abrasive. Then I read that fumed silica is often used to thicken polyester resin. I would assume that the amount of fumed silica would vary quite a bit from different manufacturers, products, runs, etc.

Edit; Just noticed that you said polyethylene and not polyester. I don't know if fumed silica is used in polyethylene fiber, but it certainly wouldn't surprise me.
 
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i tested an r2 blade. and it managed 142 cuts then i simply ran out of rope, 5m sounds much but its not that much really. and it was about 85-90% as bad as the fiskars at 70. probably could have gone 160 or so really.

gonna get natural rope and see what happens. preferably i would want the fiskars to get dull at 10 or so cuts. so i dont have to do this all day long.
 
no i just sawed through, but for this to happen you have to use maybe 1/3 of the blade pretty much. so its the same for all knives i guess.
 
inferno said:
i got some polyethylene fake hemp rope 36mm. sharpened up my fiskars beater. its some krupp low carbon crap SS at 52hrc. took it to 4k on glass.
after about 30 cuts it started to tear paper in one spot. and after 70 cuts its tearing for the entire front half
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Nice of you to document it for us!

:goodjob:
 
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