One finishing stone which one?

D

DavidL41

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Oct 12, 2014
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I watched a video of a Japanese knife sharpener with 40 years experience talk about using a finishing stone to sharpen a knife professionally, meaning that is the only stone he will use for sharpening a sushi knife. The reasoning he gave is that the lower grit stones wear away the knife faster so that it needs to be replaced and the higher grits (4k+).
The knifes I use need to be sharpened every couple of minutes, so the high grit stone look like a good fit.

What stone would work the best to quickly maintain the cutting edge? 6k,8k, 12k?
 
the jnats use one base stone and several smaller stones to make slurry in progression. they are costly a few hundred dollars for a base sone of any size. if you want a finisher look at the new apache strata it is strictly a finisher 10 to 12k estimated. I have 4 and they all work well, need only water and the stone.
 
I've been ridiculed for ONLY using a kitayama and chosera 8000 grit.

I have the 400 1000 2000 and 4000s, but I just bring a 8000 to work and have been excellent with it.

My 3 year old yanagi looks better than most 1 year yanagis I've seen.
 
DavidL41 said:
The knifes I use need to be sharpened every couple of minutes, so the high grit stone look like a good fit.
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What kind of cutting tasks are you doing and what kind of blades are you using? Every couple of minutes seems far faster of a wear cycle than I've heard of for working blades.

Brian.
 
Hwang is 12k too fine? In your opinion is 8k the sweet spot?
The 12k chinese water stone are cheap and from reviews are great for the cash . If it takes more than 3 minutes (preferably 30 seconds to a minute a side) to get the blade from slightly unsharp to sharp then it wont work. Would 12k work and not take too long?

Im using a curved exacto style knife (cpm154cm steel) and cutting vegetable tanned leather (stiff) and chrome tan leather (slightly elastic). The blade has to be at minimum 90 percent sharp or it will drag the chrome tan and stretch it.
 
david the apaches are very fast and a good size one is not as expensive as a jnat, the finish on my razors is somewhere around the jnat edge, some say they can tell a difference but I have plenty of stones and if blindfolded I couldn't tell the difference in feel or edge. the apache is a lot less than a comparable jnat setup. it is a hard stone as well, lap one and you will see what I mean, almost as bad as an Arkansas hard to lap. I haven't got one that really needed lapping but I do it anyway.i am very particular about my razor stones. I have a few that were several hundred bucks and I don't want to try to replace them. try a small apache he has some around 50 or so and you wont regret buying it ,just wish you had bought a bigger one
 
that Chinese 12k is a brick I bought one and use it for a door stop. the things are hit and miss over on b and b forums a survey 1 out of 5 was usable
 
This may be overthinking but..

For 1k, 5k, 12k progression where does the grits come in play in terms of sharpness.
In vague terms you would use 180 grit to get it from extra blunt(0 percent and sharpen to 60 percent) to just cuttable, and then 1k, 5k to get it razor sharp, 12k would put a super fine edge.

What percentage of sharpness would each grit be. Im mostly trying to figure out to get from 90 percent or 95 percent sharp to 100 percent sharpened.
Is this about right in general terms?

8k brings the knife from 80 percent sharpness to 100 percent.
10k brings the knife from 85 percent to 100 percent
12k brings the knife to 90 percent to 100 percent

Is there any value in going over 5k. Does 8k and over give better edge retention, and sharpness?
 
I've never used a stone over 8000 grit, but have heard from chefs who has, and there isn't too much a difference, not with chef knives anyways, as most chefs barely go over 1000 grit.

I use 8000 since it's what I have, and I didn't want to bring every stone with me to work so I just bring the 8000 and after a while it was clear to me that once your knife is sharp, there is almost no need to use coarse stones unless you damaged the edge badly.

My 400 1000 2000 and 4000 is just to fix other chefs bad knives, my knives have only been sharpened on the 8000.

I have jumped from a 400 to 8000 before, it works but will take a long time to remove the 400 scratches, a long timr lol
 
Respectfully, I think HwangJo and David are talking about two entirely different cutting tasks. It's worse than apples and oranges. It's soft fish versus tanned leather! I haven't cut much leather, but what I did cut was definitely harder use than any meat or vegetable I've ever cut. WAY WAY harder.

David, I think you should try a coarse edge. Coarse edges last longer than fine edges when cutting things that are moderately to very tough. There's been a bit of discussion about that here over the years with numerous members sharing their experiences with coarse edges. Over at the chef knives to go forum there's a discussion going on right now where Jason B tells about his experience with a 300 grit edge vastly outlasting an 8000 grit edge, as tested by a CATRA machine. That's controlled real testing.

Your question about sharpness is interesting because sharpness is about two things: Edge thinness at the apex. Polish of the edge bevel. With even a very coarse edge, you can get a very thin apex that will cut most things like a demon. An edge at 100 micron with just a tiny bit of stropping will shave some hair, and cut cardboard, rope, paper, etc VERY well and have a high degree of useable sharpness.

Polishing the edge makes it work better for push cutting tasks like shaving hair, whittling wood, etc. I'm not sure what kind of cutting stroke you use on leather, but I suspect a low grit edge would cut very well and outlast your high grit edges by a factor of 2 to 3. That's what my experience is when comparing a 100 micron edge with a 4 micron edge.

When trying a coarse edge, the mistake most people make is to not fully deburr the edge. Spend some extra time making sure the edge is very clean. Maybe draw the edge through cork or soft wood. Perhaps strop 5 to 10 times per side on loaded leather. Then your coarse edge should really sing.

This is a really interesting topic. I'm anxious to hear what you figure out with your cutting and sharpening!

Brian.
 
bgentry said:
Respectfully, I think HwangJo and David are talking about two entirely different cutting tasks. It's worse than apples and oranges. It's soft fish versus tanned leather! I haven't cut much leather, but what I did cut was definitely harder use than any meat or vegetable I've ever cut. WAY WAY harder.

David, I think you should try a coarse edge. Coarse edges last longer than fine edges when cutting things that are moderately to very tough. There's been a bit of discussion about that here over the years with numerous members sharing their experiences with coarse edges. Over at the chef knives to go forum there's a discussion going on right now where Jason B tells about his experience with a 300 grit edge vastly outlasting an 8000 grit edge, as tested by a CATRA machine. That's controlled real testing.

Your question about sharpness is interesting because sharpness is about two things: Edge thinness at the apex. Polish of the edge bevel. With even a very coarse edge, you can get a very thin apex that will cut most things like a demon. An edge at 100 micron with just a tiny bit of stropping will shave some hair, and cut cardboard, rope, paper, etc VERY well and have a high degree of useable sharpness.

Polishing the edge makes it work better for push cutting tasks like shaving hair, whittling wood, etc. I'm not sure what kind of cutting stroke you use on leather, but I suspect a low grit edge would cut very well and outlast your high grit edges by a factor of 2 to 3. That's what my experience is when comparing a 100 micron edge with a 4 micron edge.

When trying a coarse edge, the mistake most people make is to not fully deburr the edge. Spend some extra time making sure the edge is very clean. Maybe draw the edge through cork or soft wood. Perhaps strop 5 to 10 times per side on loaded leather. Then your coarse edge should really sing.

This is a really interesting topic. I'm anxious to hear what you figure out with your cutting and sharpening!

Brian.
Click to expand...


Very good points ^
Awhile back I had to figure out the best possible edge for my work environment of the time. Highly polished edges were failing in under two days, and one week saw them unserviceable. As I began to drop down in finish, edge retention went up. I stopped at 80 grit - this edge stayed serviceable for weeks instead of days. It will not cut well with a press, but with a draw is capable of severing some very tough materials with relatively little applied force. Have come to conclude that whatever edge/cutting method gets the job done with least applied force will generally have the longest life.

I did have a project at work where I was cutting a lot of Dow Tuff board. A few long passes through this stuff and the knife blade was almost too hot to press against skin. I glued some 300 grit AlOx lapping film to a heavy pressboard shipping tube and used the opposite side for a strop. Cut for ten minutes, spend two doing a quick burr, flip, remove most of the burr, strop on the tube. Edge was armhair shaving sharp, knife blade was very thin stock.

Sometimes if the task is very specific, you have to think outside the box. I wouldn't want to be touching up a knife on a waterstone with that kind of regularity.
 
Can we get a picture of the knife, or a link to one? Can you also explain what you consider 100% sharp and how you determine it? I have suggestions for finer stones and some for coarser. but i don't think we have enough information to "sell" you something.
 
http://www.knipknives.com/leather.php. I sharpen only the first 2 cm with a stone. The blade has to be sharp enough to cut upholstery type leather and veg (has some stretch) with a pull cut for an exact pattern, a bit off and its not usable. When the blade gets slightly dull it pulls the leather, because the material is has stretch.

Im thinking of a dmt fine/ef because I wont have to wet the stone and can keep it on my work bench. Im still trying to figure out whether to go coarse or fine for my needs and what grit.
 
Generally speaking you can go quite fine. And so long as the edge is not allowed to degrade below what that stone can restore you would never need a coarser stone. At least until such a time as you either damage the edge or it needs thinning.

That said if I were limited to one finisher it would probably be a JNat , maybe a Nakayama Iromono or something.

If the edge is not holding up under current constraints , consider getting a custom in something a little more specefic. This will depend of course as to how the edge is failing. Chipping , more durable steel. Rolling/Deformation go to a harder steel.

For sharpening that look at some diamond films. Low cost with a large range of grits. Keep your finest one handy for touchups.
 
All the leather working knives I just finished up were finished on a Shapton pro 5k. This included 4 round knives and and several straight knives. No need for anything finer IMO.
 
Sorry I didn't know the knives in question was for leather working. I mainly cut food, so coarse edges aren't great for food.

yes for other items a coarse edge works better.
 
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