How sharp is sharp enough?

[AlbuquerqueDan]

Being new to Japanese knives and sharpening, I'm struggling to figure out how sharp "really sharp" is.

I've purchased three knives through CKTG recently, and have opted to get all three sharpened before they were shipped out. After a few weeks of sharpening practice, I can get any blade as sharp as the CKTG edges. However, there's a part of me (the obsessive part) that wants an even sharper blade. I'm sure there are others like me. (Maybe?)

Anyway, how do others determine when a knife is sharp enough? Personally, I dice an onion to test my edge, and if the onion makes any noise, or feels like it's being crushed in any way, the blade is not sharp enough, and it's back to the stones/strops. I would love to know how othet people on this forum know when to quit.

Also, on a related note, I've been getting the best results on my gyutos by sharpening up to a 6000, then stropping on loaded leather, then going back down to a 4000 and doing a few stropping passes. (This is for my onion test). What progression seems to get the best results for you guys?

[Ourorboros]

The line is where you decide it is. Really. It is possible to put on an overly fragile edge, which is where microbevels come in.
The best progression depends on steel & intended use. I never go backwards though.

[Kit Craft]

I could easily live with an edge in the 700 grit range if I had too. As long as it is a clean edge free of burr and well formed it should crush nothing. But why settle if you don't have to.

[AlbuquerqueDan]

The best progression depends on steel & intended use. I never go backwards though.

Yeah, I've never heard of anyone recommending going backwards, so there may be something to be learned from that (i.e., don't do it!). However, I'm still experimenting and I found very lightly stropping on a mid-high stone as the last step really puts on an awesome edge (maybe not the ultimate best edge, but so far the best edge I've created for chopping onions with a HAP40 gyuto).

I decided to try a backward progression after reading The Science of Sharp blog for straight rasors. (If you haven't browsed through it, do yourself a favor and check it out. The electron microscope images are stunning). The blog concludes that stropping on denim, then on leather produces a very sharp, very resiliant edge. This edge, though, is very smooth, so I decided to rough it up a bit on the 4000. Anyway, I sure am having a blast learning all this stuff.

To get back to my original question: how sharp is sharp enough, I guess it's about functionality and finding the balance between sharp and resilient. I guess the problem I have right now is, I can always imagine finding a better balance, so it's back to the stones to try something nttew and never leaving well enough alone.

Kit, I like your attitude. Why settle if you don't have to? I'm just wondering where to stop when settling isn't an issue. How do you test/know when your knife is done?

[Kit Craft]

The best progression depends on steel & intended use. I never go backwards though.

Yeah, I've never heard of anyone recommending going backwards, so there may be something to be learned from that (i.e., don't do it!). However, I'm still experimenting and I found very lightly stropping on a mid-high stone as the last step really puts on an awesome edge (maybe not the ultimate best edge, but so far the best edge I've created for chopping onions with a HAP40 gyuto).

I decided to try a backward progression after reading The Science of Sharp blog for straight rasors. (If you haven't browsed through it, do yourself a favor and check it out. The electron microscope images are stunning). The blog concludes that stropping on denim, then on leather produces a very sharp, very resiliant edge. This edge, though, is very smooth, so I decided to rough it up a bit on the 4000. Anyway, I sure am having a blast learning all this stuff.

To get back to my original question: how sharp is sharp enough, I guess it's about functionality and finding the balance between sharp and resilient. I guess the problem I have right now is, I can always imagine finding a better balance, so it's back to the stones to try something nttew and never leaving well enough alone.

Kit, I like your attitude. Why settle if you don't have to? I'm just wondering where to stop when settling isn't an issue. How do you test/know when your knife is done?

I would not say that I have never heard someone suggest going back because I have but that may not be the whole truth. These people are taking their relief bevel to say 6-8k and putting a 3-5k micro bevel at 35 degrees on each side.

Testing I have done a number of ways over the years but often times I use newsprint as a strop between stones and I will simply test my edge with that. As long as I can cleanly push cut at 90 degrees with and against the grain then I know that the knife will perform the way I want it to. That can happen as low as 400-600 grit on a very good stone but is more typical at around the 1k mark. Now, depending on what I am cutting I will refine my edge from there but only lightly. I have done other tests such as seeing if the edge snags on the hair on the back of my head or if it stick to my fingernail, obviously testing for bite. It should still do this after a 5-8k stone if you do not over polish the edge. However, how that translates in use is another story.

If we are talking about actual food testing then my go to is carrots. I square off a lot of carrots and I know how I want the edge to feel going through them. I do not want any initial hesitation which I often get from a 6k+ edge. The edge is very sharp but I don't like the way it feels. Now, a 3-5k edge can offer slight resistance all the way through but give a consistent feel while cutting from start to finish and this is what I define as feedback within the cut and I like that feeling. An edge that feels like this, for me, through carrots will work just fine on tomato and pepper skins but the opposite is not always true. What I mean to say is that if I make the test and build an edge purpose built for tomatoes it does not always give me the feel that I want for other produce.

That does not mean that I have to use a 1k+3k combo or 1-2-5k progression to get said edge. I can use larger jumps and not fully polish the edge on each. I can set the edge on a 1k, clean it up on a 6/8k and do a few finishing strops on some 1 micron CBN on balsa or even some newsprint for example. The grit itself is not so important but the type of edge you choose to get from the stones.

Now, for other edges I do like them "smooth" for slicing raw boneless and fat free meats. In this case I do a full progression polishing at every point all the way to 1 micron or about 16k. However, for trimming fat I put a 1k edge on a knife as fat and hair seem to dull knives quickly and I can touch them up without thought. (I do a lot of butchery at specific times of the year.)

Where to stop, imo, is really a personal thing. My mother and wife both like an edge off of the Shapton pro 2k and nothing higher. My grandfather likes an edge off of a soft Arkansas or something in the 1k range but he does loads and loads of butchery and not so much anything in the kitchen. Plus he uses soft knives and a steel to maintain his edges.

[salemj]

I like a knife to cut paper towels cleanly while also going through tough skins (like a grape tomato) without a thought. Often, this means a middle-grit edge for me (maybe around 2k plus stropping with compound).

Honestly, I think my real limiting factor is that I like to sharpen several knives at once, which means using the same stones for a variety of steels and heat treatments. I know some of my knives can take and hold a high-grit finish with no problem and still go through skins for days, but many of my knives simply cannot do that particularly well at higher grits while also surviving mincing, etc, but they do not seem to have as much of a problem at lower grits.

I think that, if i had more stones, I would start putting special edges on every knife, and then only using them for certain applications. Perhaps this is my "real" answer to your question: sharp, for me, is practical performance, and the limit of practical performance in terms of refinement can vary tremendously from knife to knife.

Oddly enough, we are probably opposites, because I also like a lot of feedback in the cut, but you seem to define sharpness by a lack of feedback in the cut (silence, effortlessness)!

Haha. I see Kit just posted about this same thing, but with much more detail. Thanks, Kit!

[Kit Craft]

I like a knife to cut paper towels cleanly while also going through tough skins (like a grape tomato) without a thought. Often, this means a middle-grit edge for me (maybe around 2k plus stropping with compound).

Honestly, I think my real limiting factor is that I like to sharpen several knives at once, which means using the same stones for a variety of steels and heat treatments. I know some of my knives can take and hold a high-grit finish with no problem and still go through skins for days, but many of my knives simply cannot do that particularly well at higher grits while also surviving mincing, etc, but they do not seem to have as much of a problem at lower grits.

I think that, if i had more stones, I would start putting special edges on every knife, and then only using them for certain applications. Perhaps this is my "real" answer to your question: sharp, for me, is practical performance, and the limit of practical performance in terms of refinement can vary tremendously from knife to knife.

Oddly enough, we are probably opposites, because I also like a lot of feedback in the cut, but you seem to define sharpness by a lack of feedback in the cut (silence, effortlessness)!

Haha. I see Kit just posted about this same thing, but with much more detail. Thanks, Kit!

Heh, I have told you before that I like the way you think. You need more stones though!

[salemj]

Very true! Oddly enough, I'm most interested in diversifying my 1-3k range...but people seem to obsess a lot more over higher ranges when it comes to naturals. Oddly enough, I do think this is relevant to the OP: we talk a lot about how sharpness is relative and how there are different types of sharp. I'm still wondering at what point a 3-4k edge really feels less sharp than an 8k edge. Certainly not through potatoes, or other root veggies. And certainly not through cooked meats. But raw fish? Sure. Some wet skins? Sure. Paper-thin push-cuts through diakon? Ok. Still, in some ways, even feeling the difference of a higher-grit or more refined edge is a matter of paying way more attention to the cut and cutting certain ingredients. That is fine, of course, but it also highlights a shift from practical applications to ideal conditions. And it also highlights the fact that when working with higher grits, we tend to be much more careful and precise. Bringing that precision down to a lower grit on the stones and strops can make a real difference...but this is often smoothed over if one knows there are still 2-3 more stones left in a progression. Are we really getting the full potential out of our 2k range?

[Kit Craft]

Very true! Oddly enough, I'm most interested in diversifying my 1-3k range...but people seem to obsess a lot more over higher ranges when it comes to naturals. Oddly enough, I do think this is relevant to the OP: we talk a lot about how sharpness is relative and how there are different types of sharp. I'm still wondering at what point a 3-4k edge really feels less sharp than an 8k edge. Certainly not through potatoes, or other root veggies. And certainly not through cooked meats. But raw fish? Sure. Some wet skins? Sure. Paper-thin push-cuts through diakon? Ok. Still, in some ways, even feeling the difference of a higher-grit or more refined edge is a matter of paying way more attention to the cut and cutting certain ingredients. That is fine, of course, but it also highlights a shift from practical applications to ideal conditions. And it also highlights the fact that when working with higher grits, we tend to be much more careful and precise. Bringing that precision down to a lower grit on the stones and strops can make a real difference...but this is often smoothed over if one knows there are still 2-3 more stones left in a progression. Are we really getting the full potential out of our 2k range?

Good points all around. Particularly those that speak of people rushing through the mid grit stone to get to the fine stone. I can not speak for others but I can say that I have found myself doing that in the past. However, I can say that unless I am dealing with finishing a bevel for cosmetic reasons I like a two stone progression, barring repairs. I go one of two ways with this. A medium coarse stone 400-800 grit and a medium stone 2000-4000 or a medium and fine stone in the 1-2k range and then the 3-8k range. However I have done a lot of experimenting with using only a medium grit stone in the 2-4k range to keep my edges in order between full progressions and for that I am just in love with a Shapton Pro 2k.

As for naturals in the Naka-to range I think they are grossly underrated and people spread so much misinformation. I find this particularly true about people saying that mid range naturals are not efficient in the same sense as finisher and I find that to be pure hogwash. Sure, there are slow naturals in that range but there are some turds in the Awase-to range too! Not just a few either. I think a lot of people do not fully put into the Naka-to stones what they deserve. Just because a stone is listed at being in the 1-2k range does not mean that is how it should be used. These stones don't work the same way as synthetics and neither do natural finishing stones which are often used AFTER a synthetic finisher so why not do the same with a Naka-to? As an example, my Igarashi is in the 2k ish range but works best after a synthetic 2k or even a coarser natural like an Omura or Amakusa. Not so much a stone I want to set an edge on but a stone to push that edge further and yes, even finish on.

There are just so many offerings in the Naka-to range and everyone just say "my $20 bisnui sucked so all naka-to suck" and it is not the case at all. Hell, I wouldn't buy a $20-30 binsui unless I was looking for a gamble. Mine cost much more than that and I think its quality is reflected. It is by no means a bevel setter but it is a great stone to follow one or use as finisher for butchery. In fact, this leads into what you say about getting the most out of a 2k. I think is people would put more effort into not only mid grit synthetics but naturals their eyes would light up when they tested the edge! Look at it in its own right rather than as a means to an end.

In that same vein I think that a lot of people who really want to get into this as a hobby rather than as a means to an end should spend some time dedicating their sharpening to only a Naka-to range stone, be that natural or synthetic and forget about the coarse stone and finish stone for some months. Learn what it takes to raise that burr, flip it, reduce it remove it and refine the edge all on a 2-4k stone. I assure you that it makes you have a new found respect for the range of stones that we have.

Er...yeah...I went off the rails a bit.

[cwillett]

As long as I can cleanly push cut at 90 degrees with and against the grain then I know that the knife will perform the way I want it to. That can happen as low as 400-600 grit on a very good stone but is more typical at around the 1k mark.

Man, I need to up my game.

[Jason H]

Very interesting thread here... caused me to think about the SG 30000 stone. What possible use or value does it hold? At what point can a human no longer detect further progression on stones?

[salemj]

I posted a reply but it didn't take. I wouldn't consider your post "off the rails," Kit. I think you are spot-on.

To give credit where it is due, I have noticed that when a question is asked about about 1-3/4k stones, people have lots of preferences, experience, and opinions. It is clear that a lot of people think deeply about this range. However, what is interesting is how, if it ISN'T about a question, but is rather a discussion about sharpening, it seems to always push toward higher grits. Even questions initially about lower grits seem to push toward discussion about ideal refinements that are higher. This isn't always the case, of course, but it is a trend.

So, even while I recognize that many members do try to master the middle grit stone, I still assume that many - like me - also tend to treat the edge of a knife within a progression differently than they treat it at the end of that progression...which means they are not necessarily finessing the edge/mud/potential of a mid-grit stone if they ultimately go higher.

In relation to the OP, this again shifts to question to one of defining "sharpness" not in terms of how effortless a cut is in a hypothetical sense, but rather how sharp a knife "feels" in a given application. Depending on how the knife is finished, it can definitely feel sharper to me at lower grits when actually cutting food - especially meat - even if it is "technically" not as "sharp" in terms of the refinement of the edge. The OP seems very open-minded about this, but I think I would prefer to discuss "how do you finish your edges" rather than focusing on progression or grit values for specifically.

FWIW, the idea of going to 6k and dropping to 4k sounds a lot to me like...trying to get the effect of a natural stone in that same range. Haha.

[Chefcallari]

Your knife is sharp enough when you can cut space/time....
In a pro setting anything less is really inadequate....

[Chefcallari]

I could easily live with an edge in the 700 grit range if I had too. As long as it is a clean edge free of burr and well formed it should crush nothing. But why settle if you don't have to.

Funny you say that.... My naniwa pro 400 has been my "island" stone since i bought it.

Best $25 i ever spent

However.... The more i dick around with the kohetsu 2k... Its slowly becoming my "island" stone.

[Igalor]

I don't think I've gone though a full progression (finishing stone included) in a while, I usually stop at an aoto most of the time, that is plenty sharp for my uses, if I'm doing touch ups, which usually happens at work, my sp2k is all I need.