What is the finish with least amount of drag?

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Tethien

Tethien

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I thinned a knife recently and finished it with some 320 grit sandpaper and it has crazy high drag, like barely cutting an onion with a really thin bte.
 
The finer the finish, the lower the drag. It's why you see a lot of mirror polished yanagi. At the same time, the finer the finish, the greater the propensity of food to stick. Last I looked into it seriously, 600-800 grit was what most people recommended to be the optimal range.
 
800 is my sweet spot for sandpaper. Stones are a bit trickier, especially naturals. You'll have to experiment with various ones there. And note that stone grit is not the same as sandpaper grit. An 800 sandpaper grit is closer to 2-3k on my synthetic stones.
 
MSicardCutlery said:
The finer the finish, the lower the drag. It's why you see a lot of mirror polished yanagi. At the same time, the finer the finish, the greater the propensity of food to stick. Last I looked into it seriously, 600-800 grit was what most people recommended to be the optimal range.
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Im not sure this is strictly true. Higher polish means more surface area in contact with the food and I know some have said that it leads to more "stiction". Idk how much truth there is to this but it may not be quite so straightforward.
 
In physics they are different, to my knowledge, e.g. drag depends on velocity, stiction doesn't. I don't really know any physics, but I think what's happening when wet stuff sticks to the blade has to do with surface tension / capillary action. See e.g. section 2.1 of this paper.

https://ris.utwente.nl/ws/files/6645982/stiction.pdf
There's also this line from section 6.3, that indicates that often surface roughness plays a role in stiction. "The model predicts a sharp decay of the pull-off force, if the roughness is increased beyond a value predicted by the adhesion parameter." I'm a little confused by that section since I'm not sure which parts are relevant to stiction from capillary action vs other reasons, but maybe there's more going on with stiction of product on knives than just capillary action too. Idk. Anecdotally I think I've noticed that the few mirror polished knives I've used have been pretty sticky on wet product.
 
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I wonder if the capillary and other forces described in the paper would be sufficient to trigger macro-scale movement – imagine a V where outside the V we have a rough 120 grit surface full of asperities and channels, while inside the V we have a 12000 grit mirror polish with high capillary bonding. If we place a potato slice at the apex of the V, would the potato spontaneously travel from the apex to the base of the triangle motivated by energy considerations alone? i.e. if the stabler configuration sees the potato at the base of the triangle, touching as much mirror as possible, would it actively seek that low-energy state by crawling along the V?
 
I like 400-800 finish, the mirror polish on a double bevel is sticky as hell.
MSicardCutlery said:
The finer the finish, the lower the drag. It's why you see a lot of mirror polished yanagi. At the same time, the finer the finish, the greater the propensity of food to stick. Last I looked into it seriously, 600-800 grit was what most people recommended to be the optimal range.
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I think it works well for Yanagi, since most just have mirror polish above the shinogi, the bevel is still Kasumi unless we are talking about honyakis.
 
mengwong said:
I wonder if the capillary and other forces described in the paper would be sufficient to trigger macro-scale movement – imagine a V where outside the V we have a rough 120 grit surface full of asperities and channels, while inside the V we have a 12000 grit mirror polish with high capillary bonding. If we place a potato slice at the apex of the V, would the potato spontaneously travel from the apex to the base of the triangle motivated by energy considerations alone? i.e. if the stabler configuration sees the potato at the base of the triangle, touching as much mirror as possible, would it actively seek that low-energy state by crawling along the V?
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I'm not sure I understood everything correctly, but considering other forces in action (gravity, friction) I'm not sure there could be such a mouvement on a macro scale. Maybe the initial position could also be a semi-stable position and would require something to make it move to a more stable position.
 
ian said:
In physics they are different, to my knowledge, e.g. drag depends on velocity, stiction doesn't. I don't really know any physics, but I think what's happening when wet stuff sticks to the blade has to do with surface tension / capillary action. See e.g. section 2.1 of this paper.

https://ris.utwente.nl/ws/files/6645982/stiction.pdf
There's also this line from section 6.3, that indicates that often surface roughness plays a role in stiction. "The model predicts a sharp decay of the pull-off force, if the roughness is increased beyond a value predicted by the adhesion parameter." I'm a little confused by that section since I'm not sure which parts are relevant to stiction from capillary action vs other reasons, but maybe there's more going on with stiction of product on knives than just capillary action too. Idk. Anecdotally I think I've noticed that the few mirror polished knives I've used have been pretty sticky on wet product.
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This is basically what I was thinking of, since stiction is influenced differently by coefficiency of friction, it can't be the same. I guess in the knife world, terms aren't always exact, though.
 
I've been wondering about this subject in the past and one thing I can definitively tell you from experience is that mirror finish does indeed create more stiction and is an absolute utter waste of time. :D
But still figuring out the sweetspot.
 
I think sometimes what gets lost in the shuffle is that many attributes of knives are about relationships with product. I would think the relative stiffness of what’s being cut factors in too.

Some soft/moist stuff can have a tendency to ‘scrunch’ on the blade if there is too much stiction. The product is not stiff enough to overcome the stiction.

Think about cutting a piece fresh fish thinly vs. cutting a potato thinly. Assuming there’s a lot of stiction, the fish would ‘scrunch’ but the potato wouldn’t (because it can’t, because it’s stiffer). Of course, the potato could still stick to the blade, just not ‘scrunched’.

I guess my point is: It’s hard to discuss ‘stiction’ in the absolute, because there is the potential for it to matter in different ways depending on what’s being cut.
 
Best all around user finish, in my opinion, is sandpaper in the 400-800 grit range. Fine enough finish to not create tons of drag. Coarse enough to hide miner scratches.
 
M1k3 said:
Best all around user finish, in my opinion, is sandpaper in the 400-800 grit range. Fine enough finish to not create tons of drag. Coarse enough to hide miner scratches.
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400-800... JIS? FEPA?
 
blokey said:
Celsius
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Don't give them any ideas... before you know it it someone discoveres some obscure ancient imperial measurement based on the size of gunpowder grains and the new US norm is to measure everything in 'gunpowder grains per shotgunshell width', aka GGSSW.
 
You know what? At 400-800 Celsius any food with water content will evaporate and form a steam wall, so there will be no stiction and anything falls right off, since they are not even contacting! Best part you will have cooked food right off your cutting board.
 
Jovidah said:
400-800... JIS? FEPA?
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ANSI
FEPA I suppose. Whatever standard American sandpaper companies use to market their sandpaper with for American retail outlet stores, whether they have a physical store front or only online (besides the massive warehouses they have scattered around the country and run by someone that has a last name that's similar to Bozos last name).
 
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M1k3 said:
FEPA I suppose. Whatever standard American sandpaper companies use to market their sandpaper with for American retail outlet stores, whether they have a physical store front or only online (besides the massive warehouses they have scattered around the country and run by someone that has a last name that's similar to Bozos last name).
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ANSI. American National Standards Institute.

FEPA is European.
 
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