A sharpening thread of my very own (Japanese Natural Stones).

[Brian Holcombe]

Exactly, I've worked A2 on Jnats and the visual effect seems like what you are describing, abrasion around very hard carbides.

[Phil Mueller]

Thank you Brian.

[Mike Holbrook]

My goal when trekking down this path was a durable edge on HC steel. Ultimate sharpness can be fleeting but an edge that stays intact makes for a better cut after that initial extreme sharpness is gone. A durable edge is also easier to bring back to life as it only requires quick work.

I think what I'll do is post up a video of sharpening some fairly hard steel very quickly with these stones, working the full bevel.

I am trying to understand this information. I have read a good deal of discussion on knife forums about how deceptive Rockwell "hardness" testing can be. The argument being that "hard" at some point can become brittle, resulting in chipping, whereas "tougher", but softer, may hold it's shape longer. Tougher may bend but not break.

Brian, I am wondering if you feel the Jnats (Japanese natural stones?) are capable of producing a superior edge in some regards? I think you were directing your comments toward HCS (high carbon steel?) Patrick mentions the myriad of new "other" steels that are available in recent years which certainly come into consideration. There are so many different types of steel available today though. I am not sure we can even "scratch the surface" of those options without writing multiple volumes.

[ken hatch]

...

Hah, I do the same, this and setting hoops are both very enjoyable when time is very limited. I wonder if your finish stone is very similar to my Yaginoshima or maybe a bit finer (not the Nakayama, but the other one whose name escapes me). My shinden stone is very odd looking and that was the only way for me to keep it fairly reasonable in terms of price, you can probably still get a brick but wow, they will be out there, it's a great stone to use though, nice action and is often where I stop in normal use (the Nakayama is for times when an extra measure of sharpness is needed).

I built that sharpening bench so that I would run out of space for additional stones and that would be a barrier to new stones...we'll see if it works (not likely).






...

Brian,

I'll bet it works as well as my promise . I was on So's web site looking earlier tonight.

I use two finish stones, I'm still trying to sort out which I like better, one is an old stock Takashima the other a Aiiwatani Kiita. They both do a good job and get to about the same place but have different feels. The Takashima is a little soft and chalky feeling while the Kiita is harder and slicker. Looking at the finished product my old eyes can't see any difference.

BTW, I spent a couple of hours this evening working on the sharpening bench and sharpening a couple of push chisels. One I finished on the Takashima the other on the Kiita, it would take a better man than I to tell the difference.

ken

[Brian Holcombe]

I am trying to understand this information. I have read a good deal of discussion on knife forums about how deceptive Rockwell "hardness" testing can be. The argument being that "hard" at some point can become brittle, resulting in chipping, whereas "tougher", but softer, may hold it's shape longer. Tougher may bend but not break.

Brian, I am wondering if you feel the Jnats (Japanese natural stones?) are capable of producing a superior edge in some regards? I think you were directing your comments toward HCS (high carbon steel?) Patrick mentions the myriad of new "other" steels that are available in recent years which certainly come into consideration. There are so many different types of steel available today though. I am not sure we can even "scratch the surface" of those options without writing multiple volumes.

Exactly, I'm not interested in having something that works ok with everything, rather I want two things which work very well together. That, plus the time factor of experience will produce superior results in what I need them to. I use HCS and workable alloys like Blue 1, 2 and Togo Kou. Blue Steels and Togo Kou are harder to work on natural stones, but they still work on them and produce excellent results. Experience on a stone is important, they reveal a lot as you put real time on them, you start to understand the personality of the stone and what works best for it.

Like most things there are many factors involved which drive the whole in a given direction, in my case it stems from ease of use in the context of how I use what I use. I often touch up an edge while I'm working, rather than using it to the point where it is dulled and cannot work I'll revisit the edge and touch it up, I do this for months and months before completely reworking a bevel from a low grit (like 1000 grit). With that said I like stones that I can just splash with water, build a quick slurry and start working them. It's hard for me to describe, but the natural stones I use have a nice feel to them in use, the slurry becomes useful rather than a nuisance. They remain mostly flat so I'm not constantly reflattening them, ect.

The effect is very similar to nice Arkansas stones, which are also enjoyable to use. I use Arkansas stones for inside curves and really enjoy them.

What originally caught my attention WTR Japanese Natural stones, all of the users talk about their use and their results in a positive way.

Brian,

I'll bet it works as well as my promise . I was on So's web site looking earlier tonight.

I use two finish stones, I'm still trying to sort out which I like better, one is an old stock Takashima the other a Aiiwatani Kiita. They both do a good job and get to about the same place but have different feels. The Takashima is a little soft and chalky feeling while the Kiita is harder and slicker. Looking at the finished product my old eyes can't see any difference.

BTW, I spent a couple of hours this evening working on the sharpening bench and sharpening a couple of push chisels. One I finished on the Takashima the other on the Kiita, it would take a better man than I to tell the difference.

ken

Haha, I'm sure thats true! I will likely just make more bench space. I keep raising the barrier to entry and it seems to have little effect.

Oh cool an Aiiwadani Kiita! Yours must be on the harder side? How do you compare them to your Nakayama? If I had to guess (and it would be just a guess since I have not used an Aiiwadani Kiita, I would guess that it's similar to my Yaginoshima Asagi, does the finish on the bevel look similar to that one in my photos, or more like that of the Shinden?

[ken hatch]

Exactly, I'm not interested in having something that works ok with everything, rather I want two things which work very well together.

...

Haha, I'm sure thats true! I will likely just make more bench space. I keep raising the barrier to entry and it seems to have little effect.

Oh cool an Aiiwadani Kiita! Yours must be on the harder side? How do you compare them to your Nakayama? If I had to guess (and it would be just a guess since I have not used an Aiiwadani Kiita, I would guess that it's similar to my Yaginoshima Asagi, does the finish on the bevel look similar to that one in my photos, or more like that of the Shinden?

Brian,

My wishes exactly, I want stones I can use with minimum fuss, that work reasonably fast on steel that is capable of getting very sharp. Long working time with a less than sharp iron is not on my wish list. My sharpening bench is less than a meter off the working end of the main work bench and is always set up. Work, step over and do a quick touch up, go back to work, repeat as needed.

The Aliwadani Kiita is almost razor hard. I expect the finish is not as nice as your Shinden but close. looking at the finish with the eye it has a nice smooth mirror finish with a slight haze and the Ji is well defined. Looking with a 10X lupe the Ha is not a near perfect matt like with the Nakayama but is close enough for most jobs.

ken

[Stanley Covington]

I am trying to understand this information. I have read a good deal of discussion on knife forums about how deceptive Rockwell "hardness" testing can be. The argument being that "hard" at some point can become brittle, resulting in chipping, whereas "tougher", but softer, may hold it's shape longer. Tougher may bend but not break.

Brian, I am wondering if you feel the Jnats (Japanese natural stones?) are capable of producing a superior edge in some regards? I think you were directing your comments toward HCS (high carbon steel?) Patrick mentions the myriad of new "other" steels that are available in recent years which certainly come into consideration. There are so many different types of steel available today though. I am not sure we can even "scratch the surface" of those options without writing multiple volumes.

Mike, allow me to insert some additional opinions.

Two points I would like to remind you of before I share my opinions:
1. Remember, what really determines the sharpness of a blade at the microscopic level where the cutting of wood gets done are the last few strokes on the last stone in the process. Everything before that is prep.
2. It is very difficult to objectively measure sharpness, and objectively measuring how long a blade remains "sharp" (whatever "sharp" means) is even more difficult. Anyone who tells you otherwise is blowing smoke up your skirt.

Let's compare synthetic and manmade stones a bit, sans the romance and history and Japanese words.

Modern manmade stones cut HC steel very, very well. This capability is extremely useful for wasting metal. Why do I believe that synthetic stones cut steel so effectively, and why are they more effective than natural stones, you may ask? The chemical particles used to make synthetic stones are measurably harder than the stone particles that comprise natural stones, so they cut steel more efficiently. In addition to being harder, the individual particles in synthetic stones have distinct, sharp corners, whereas the particles in natural stones (at least the Japanese version) tend to be rounder. Hard and angular versus soft and round. Oops, starting to sound a like a romance novel, perhaps "Love's Savage Secret?"

That reminds me of an old Japanese saying that goes something like this (not intended to be erotic): "A wife should be a stone to polish the blade that is her husband." Sharpening stones have a place deep in Japanese culture.

Anyway, back to the subject at hand.

While it is difficult to quantify the results, the process of sharpening a blade is straightforward. When you finish (vs "shape" or "prep") a blade on a any stone, whether synthetic or natural, the stone's particles plow a parallel row of furrows in the surface of the blade. The extreme leading edge of the finished blade viewed under a microscope looks quite jagged. The sharper a blade is, the thinner and more uniform this jagged edge will be. How long it will stay sharp is driven by how long it takes for the carbides exposed at this thin jagged edge to be torn off, and for the edge to round over. The sharpening stone can increase the amount of wood a blade can cut before dulling by creating furrows that tend to support the carbide particles and protect them from being torn off.

According to Ron Hock, and consistent with other studies I have seen, synthetic stone particles, being sharp and jagged, tend to plow furrows that are deep and V-shaped with walls sloped at relatively uniform angles, and narrow bottoms. The angled sides of these parallel furrows reflect light in a uniform manner, which explains perfectly why blades worked on synthetic stones easily achieve a mirror finish. By comparison, the rounder particles of natural stones cut shallower furrows with curved sides, and of course, rounded bottoms, diffusing reflected light, and producing a cloudy, misty appearance (at least ideally).

Appearance aside, I believe a high-quality high-carbon steel blade containing fine, evenly-distributed carbides as found in most hand-forged blades made of high-purity steel, and finished on a natural stone will stay sharper longer than the same blade finished on a synthetic stone of the same grit size. I have no hard data to support this opinion. But I believe the shallower, rounder furrows (or scratches) created by natural stones tend to support and hold in place the carbide crystals longer. This seems consistent with the SEM photographs I have seen, and feels consistent with how my blades perform when cutting wood.

I have been using natural Japanese finishing stones for a long time, but I don't care what mountain, or mine they came from, or what goofy name they have stamped on them. All I care about is how they perform during those last few strokes. I know the job is complete when the blade is free of visible scratches and the HC steel edge is a beautiful misty white color, and the low-carbon supporting steel is a matt grey. I don't have to test such a blade for sharpness, because I can sense it is very sharp. This is a very satisfying feeling, and one that is difficult (but not impossible) to obtain with a synthetic stone.

My advice is don't venture too close to the edge of this rabbit hole until you are truly ready to jump.

Stan

[Brian Holcombe]

Ken,

Interesting, they must have a big range in hardness. It seems the Yaginoshima Asagi are the same way, people use them for razors and for knives, which as you know are totally different, so my assumption is that there is a pretty wide range of hardness for some mines. The stone I have is fairly hard for how fast it cuts.

Sounds like you have one on the harder side, which is great. Is it easier to use than the Nakayama?

[Brian Holcombe]

Stan,

Thanks for commenting! That is a great post and describes much better the durable edge that I am experiencing with natural stones. I haven't tested them back to back per-say, but I might do so as it would be interesting.

[Normand Leblanc]

According to Ron Hock, and consistent with other studies I have seen, synthetic stone particles, being sharp and jagged, tend to plow furrows that are deep and V-shaped with walls sloped at relatively uniform angles, and narrow bottoms. The angled sides of these parallel furrows reflect light in a uniform manner, which explains perfectly why blades worked on synthetic stones easily achieve a mirror finish. By comparison, the rounder particles of natural stones cut shallower furrows with curved sides, and of course, rounded bottoms, diffusing reflected light, and producing a cloudy, misty appearance (at least ideally).

This is very interesting. Would you say that hard Arkansas stones, being natural stones, achieve the same kind of results?

I'm asking this because when I use a translucent Arkansas the surface finish looks like milky/cloudy compared to a strop with green compound where the result is shiny.

Normand

[Stanley Covington]

This is very interesting. Would you say that hard Arkansas stones, being natural stones, achieve the same kind of results?

I'm asking this because when I use a translucent Arkansas the surface finish looks like milky/cloudy compared to a strop with green compound where the result is shiny.

Normand

Normand:

It seems likely that Arkansas stones could achieve similar results if the particle size is small enough, and one is careful to prevent burnishing.

Stan

[Mike Holbrook]

Thanks Brian and Stan, this is the information I have been missing, which explains why and how natural stones may actually work to provide a very good or excellent final surface. Stan thanks for your extensive effort here to demystify these stones and the methodology to use to get the most from them. It all makes sense in relation to those other "truths" I have clung too in regard to sharpening. Stan thanks for warning me of the edge of the rabbit hole. I worry about that smoke up the skirt too, IMHO there is always a great deal more theory than fact. Even the best theory eventually seems to find variations that are even better....

I am wondering if a similar final result can be achieved with very hard ceramic stones like the Spydercos and green compound? I am guessing this is debatable. It may be that the nature of the fine but still sharp particles in these man made stones tends to cut or rub off softer steel vs pressing it between carbides?

Brian, I try to sharpen with a similar methodology to yours. I try to sharpen before my tool gets completely dull, at the time I can feel it slowing down/meeting more resistance..It takes less time and allows me to use a sharper blade more of the time for a similar amount of sharpening effort. Short breaks from the work do not interrupt ones flow whereas sharpening very dull tools can.

Thanks for the replies, sorry to steer a little off course Brian.

[ken hatch]

Mike, allow me to insert some additional opinions.

...(S)ynthetic stone particles, being sharp and jagged, tend to plow furrows that are deep and V-shaped with walls sloped at relatively uniform angles, and narrow bottoms. The angled sides of these parallel furrows reflect light in a uniform manner, which explains perfectly why blades worked on synthetic stones easily achieve a mirror finish. By comparison, the rounder particles of natural stones cut shallower furrows with curved sides, and of course, rounded bottoms, diffusing reflected light, and producing a cloudy, misty appearance (at least ideally).

Appearance aside, I believe a high-quality high-carbon steel blade containing fine, evenly-distributed carbides as found in most hand-forged blades made of high-purity steel, and finished on a natural stone will stay sharper longer than the same blade finished on a synthetic stone of the same grit size. I have no hard data to support this opinion. But I believe the shallower, rounder furrows (or scratches) created by natural stones tend to support and hold in place the carbide crystals longer. This seems consistent with the SEM photographs I have seen, and feels consistent with how my blades perform when cutting wood.

... I know the job is complete when the blade is free of visible scratches and the HC steel edge is a beautiful misty white color, and the low-carbon supporting steel is a matt grey. I don't have to test such a blade for sharpness, because I can sense it is very sharp. This is a very satisfying feeling, and one that is difficult (but not impossible) to obtain with a synthetic stone.

My advice is don't venture too close to the edge of this rabbit hole until you are truly ready to jump.

Stan

Stan,

That has been my understanding and it has proven to be true (at least the sharp part) in practice. I have often said "shiny is not necessarily sharp". Sharp is a fine, can be almost matt, scratch pattern that holds up after the first contact with wood. Good Ark stones will produce the same fine matt finish, I've just recently jumped down the rabbit hole but I'm finding the same is true with JNats.

ken

[Kees Heiden]

Normand:

It seems likely that Arkansas stones could achieve similar results if the particle size is small enough, and one is careful to prevent burnishing.

Stan

How do you prevent burnishing on a fine Arkansas and why would you?

[Normand Leblanc]

How do you prevent burnishing on a fine Arkansas and why would you?

If someone could explain what burnishing is it would be appreciated. Must be my frenchglish!
Normand