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

[Brian Holcombe]

With all of the sharpening threads at current I feel a bit left out, so I thought I'd blog away and post it up.

https://brianholcombewoodworker.com/...s-perspective/

Those asking to be pushed over the edge into natural stones territory may find this interesting (Patrick Chase).

[Patrick Chase]

Those asking to be pushed over the edge into natural stones territory may find this interesting (Patrick Chase).

Now when you say "natural stones" you mean a lapping compound consisting of natural diamonds, right? I can be TOTALLY down with that...

Very nice writeup!

[Patrick Chase]

Wait, you're slurrying a JNat with a DIAMOND PLATE? People have been burnt at the stake for lesser apostasies.

Of course given that one of the two stones you did that to is a Nagura it isn't clear to me what else you would use?

[Patrick Chase]

OK, I have but one concern, and it relates to the comparison to the synthetic 13K, presumably the Sigma?

I have that stone and know what it can do (based on examination under microscope) and your results look incompletely polished to me, by which I mean that I think those scratches came from the previous grit.

Most people wouldn't use a stone like that to polish the entire bevel of a chisel. They'd instead focus their efforts on the tip, whether by creating a flat microbevel or by creating convexity at the tip by lifting the handle a bit during final polishing. Doing that makes the polishing go faster at the edge and avoids this sort of issue.

It does seem that JNats are uniquely capable of polishing the entire face for what that's worth.

[Brian Holcombe]

I am going to revisit the 13k, Stan mentioned that he also saw that the finish looked a bit suspect. I attributed it to a raking light, in person it looked pretty normal, but it's worth taking another look.

Thanks for your comments, I knew this thread had the potential to be interesting.

Also fair point that I would normally not polish the entire bevel with that grit, in fact I had debating including it but thought it may make for an interesting data point.

The slurry created with a Jnat makes for evenly polishing a full bevel to be much more easily achievable.

Tsushima Nagura is not the same as a White Nagura stone, which would be used for slurrying finish stones. Many people are slurrying with a 1200 atoma plate currently.

[Phil Mueller]

Ok, Brian, you started this...so you get to deal with inexperienced questions.
And no, I didn't use search or google first...I read your blog, and I have some basic questions. You're just going to have to deal with the burden of being the credible source for all stones natural.

First, give me the basics of these natural stones. Do you use water, do you always create a slurry with some other medium first, do they need constant flattening like synthetics? Are all these stones actually mined only in Asia/Japan?Would there not be other stones around the world with similar qualities?

Second, that last pair of stones you pictured - Uchigumori - doesn't appear to have a flat face...or am I just not seeing it?

Third, I have a friend who's a geologist working in the mountains of Northern Turkey. Anything you want me to tell him to look for when he's digging up rocks?

Thanks for the write up...I enjoy learning...but be warned, this may not be the last of me on this subject.

[ken hatch]

Brian,

Good post. I've done several A&B's of natural vs. synthetic stones. My results tracked very well with yours. Both will sharpen steel very well but there is a different "look" in the finish. BTW, our stones are not too different but I'm still looking for nice Shinden Suita. I've promised myself that will be my last stone.....and yes I've heard that one before, but this time I really mean it....I promise .

ken

P.S. I really do make things but when shop time is limited and/or I'm knackered nothing is as relaxing as putting iron to stone and even better to a natural stone.

[Jim Koepke]

Just when I'm starting to spend some money on natural stones from Arkansas you come along with this.

jtk

[Patrick Chase]

I am going to revisit the 13k, Stan mentioned that he also saw that the finish looked a bit suspect. I attributed it to a raking light, in person it looked pretty normal, but it's worth taking another look.

You bring up an interesting implied point here by mentioning raking light: Directionality.

The scratches from the synthetic stones are strongly oriented in a single direction, while the ones from the slurried JNats appear to be more variable. The same thing happens with sandpaper vs loose grit, even using the same particle size and lapping motion. Basically loose particles (for example in a slurry) can "roll around" semi-randomly and thereby create scratches that aren't precisely parallel to the honing direction, whereas with fixed media (stones w/o slurry, sandpaper) the scratches always follow the honing direction. I can easily see how that could create at least some of the observed difference in your study.

With that said, I've actually looked at results from the 13k under highly directional light and I still think yours look a bit rough :-).

[Patrick Chase]

Sorry to double-double reply again, but...

My two main reservations w.r.t. JNats are the likelihood of serious marital strife (hiding the invoices only gets you so far), and the fact that I like to play with weird steels. I have a whole lot of PM-V11, which is basically PM-D2 but with more Chromium. My only current set of Japanese chisels are HAP40 (basically PM-M4 HSS). My pigstickers are D2 (no PM). It goes on in that vein.

Basically I have a heap of tools that won't play all that well with natural Silicate abrasives. Heck, some of them don't even work all that well on Sigma Select IIs, though diamond paste/film works with everything so that's become my "final line of defense".

[Brian Holcombe]

Ok, Brian, you started this...so you get to deal with inexperienced questions.
And no, I didn't use search or google first...I read your blog, and I have some basic questions. You're just going to have to deal with the burden of being the credible source for all stones natural.

First, give me the basics of these natural stones. Do you use water, do you always create a slurry with some other medium first, do they need constant flattening like synthetics? Are all these stones actually mined only in Asia/Japan?Would there not be other stones around the world with similar qualities?

Second, that last pair of stones you pictured - Uchigumori - doesn't appear to have a flat face...or am I just not seeing it?

Third, I have a friend who's a geologist working in the mountains of Northern Turkey. Anything you want me to tell him to look for when he's digging up rocks?

Thanks for the write up...I enjoy learning...but be warned, this may not be the last of me on this subject.

Haha, great post Phil! I flatten them initially much like a synthetic, and I make them very flat to the point where I can't see light under a precision straight edge, and I can check them with my granite plate as well. During use I make a slurry with a 1200 Atoma plate and doing so will keep the finish stones flat (so long as I use it correctly), the Tsushima stone I work over with a 400 atoma after each use.

If you use the full surface of the stone they will remain basically flat and are generally much less maintenance than synthetic stones, sounds ridiculous but that was my main reason for moving in this direction. The mess of synthetic stones is tough for me to deal with without a shop sink, but natural stones are relatively low mess.

The stones all come from Japan and they're unique to specific strata of specific mountains in and around their respective prefectures. I believe they are all near Kyoto, except Tsushima which is an island and the stones are quarried underwater, but there are better sources than myself on where exactly each stone is from.

Uchigurmori are fairly soft stones, while both of those shown actually do have one flat face, I use them for putting a kasumi finish on rounded bevel blades so I build a heavy slurry with them and dont necessarily keep them flat in use.

Sounds like your friend may be in for a wild goose chase in Turkey .

Brian,

Good post. I've done several A&B's of natural vs. synthetic stones. My results tracked very well with yours. Both will sharpen steel very well but there is a different "look" in the finish. BTW, our stones are not too different but I'm still looking for nice Shinden Suita. I've promised myself that will be my last stone.....and yes I've heard that one before, but this time I really mean it....I promise .

ken

P.S. I really do make things but when shop time is limited and/or I'm knackered nothing is as relaxing as putting iron to stone and even better to a natural stone.

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).

Just when I'm starting to spend some money on natural stones from Arkansas you come along with this.

jtk

You bring up an interesting implied point here by mentioning raking light: Directionality.

The scratches from the synthetic stones are strongly oriented in a single direction, while the ones from the slurried JNats appear to be more variable. The same thing happens with sandpaper vs loose grit, even using the same particle size and lapping motion. Basically loose particles (for example in a slurry) can "roll around" semi-randomly and thereby create scratches that aren't precisely parallel to the honing direction, whereas with fixed media (stones w/o slurry, sandpaper) the scratches always follow the honing direction. I can easily see how that could create at least some of the observed difference in your study.

With that said, I've actually looked at results from the 13k under highly directional light and I still think yours look a bit rough :-).

Fair to say is probably showing scratches that shouldn't be there. That is a good explanation of the effect that I suspect works on the surface of a Jnat, once the slurry is created the loose grit, metal particles and water are sort of pushed around on the stone and worked under the bevel, so I would imagine they're doing just as you say.

Sorry to double-double reply again, but...

My two main reservations w.r.t. JNats are the likelihood of serious marital strife (hiding the invoices only gets you so far), and the fact that I like to play with weird steels. I have a whole lot of PM-V11, which is basically PM-D2 but with more Chromium. My only current set of Japanese chisels are HAP40 (basically PM-M4 HSS). My pigstickers are D2 (no PM). It goes on in that vein.

Basically I have a heap of tools that won't play all that well with natural Silicate abrasives. Heck, some of them don't even work all that well on Sigma Select IIs, though diamond paste/film works with everything so that's become my "final line of defense".

For the most part, while they can be a bit pricier than synthetics they are generally not crazy unless you start going after rarity and looks, if you want a big brick Nakayama kiita, then you are going to spend a small fortune, but that is unnecessary on the whole. Most users wouldn't use collector grade stones and collector grade is where you start to spend crazy amounts.

When I got into this I thought that plain high carbon steels were very boring and so I didn't pursue them initially. After some time I realized that the two (plain HC steel and Natural stones) make a great combination, they're enjoyable to work with and they surprised me in terms of durability in medium hardwoods. So, while they dont have much appeal in terms of awesomeness, they do in terms of work enjoyment. What further surprised me were the stones ability to cut blue steel 1, 2 & Togo Kou.

[Mike Holbrook]

I recently watched a David Wearver YouTube video on sharpening mediums. David's point seemed to be for day to day sharpening there is not a particular advantage between: man made Japanese waterstones, natural Japanese Waterstones, US natural sharpening stones, US man made sharpening stones. I believe the implication was that any advantages occurred at the extreme end of polishing\refining which was not a significant reason to incorporate the usually more expensive stones into day to day work.

I know that the Japanese tend to favor natural Japanese stones for sharpening some of their better high carbon steels. I am not sure, even reading Odate's book on Japanese tools, whether or not these preferences are because of preference for traditional methods or because there is some actual improvement in finish or speed of the work? Odate even seems to dance around whether or not natural/traditional stones work better/faster than man made......stones. Maybe I am missing something?

It seems to me that the very fine stones typically cost much more money but arguably produce slight improvements that may be destroyed the first time the sharpened tool strikes wood. It seems to me to be more logical to spend money on coarser/less expensive abrasives, particularly those that remove more metal faster, in order to maximize ones return on ones investment. For some reason, which I do not seem to understand, many people spend the majority of their funds in what seems to me to be an ill advised attempt to get the ultimate fine stones. The logic seems to be that a very fine stone will produce a very sharp blade which seems to me to be exactly ass backwards. The skill of the person doing the sharpening and the techniques they use to establish bevels/microbevels seems to produce superior results when it comes to getting things sharp. A person with a lesser skill set, IMHO, will just get slowed down/frustrated by a large assortment of slower working abrasives. Although I understand many of the posters here know exactly how to milk theses stones for their full worth...

I certainly do not mean to imply that Brian is pushing people to expensive very fine stones. I know he is discussing a wide range of stones and a successful methodology. I am just concerned that some may walk away from this discussion with the belief that there are magic stones that will all of a sudden make their tools "sharp as razors".

[Patrick Chase]

I recently watched a David Wearver YouTube video on sharpening mediums. David's point seemed to be for day to day sharpening there is not a particular advantage between: man made Japanese waterstones, natural Japanese Waterstones, US natural sharpening stones, US man made sharpening stones. I believe the implication was that any advantages occurred at the extreme end of polishing\refining which was not a significant reason to incorporate the usually more expensive stones into day to day work.

As with almost all woodworking advice, you have to carefully consider the context to determine if it will be valid for you. In this case the big variable is what steel[s] the person providing the advice sharpens. IIRC David mostly uses HCS these days, and what you say is reasonably valid for his usage. I have a bunch of tools made of more "exotic" steels, and no Silicon-Oxide-based medium (natural waterstone, arkansas, etc) is effective with those. The abrasive particles themselves are simply too weak/soft for such metals.

[Brian Holcombe]

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.

[Patrick Chase]

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.

Brian brings up a very good implicit point here: Average hardness is not the problem. SiOx can sharpen low-alloy HC steels up to the mid Rc60s without any problem.

The real issue is uniformity of hardness. Medium-alloy steels like A2 and higher-alloy ones like D2 form carbides as part of their grain structure, and those carbides are well up into the Rc70s. A soft abrasive like SiOx can't abrade the carbides directly, but instead slowly abrades the metal around them until they fall out, leading to both slow honing and edges that are dull/chipped from the start.

The combination of carbides and softer metal in a high-alloy steel can (very) conceptually be thought of as a microscopically laminated blade - the ultra-hard carbides provide abrasion resistance, while the softer metal around them provides toughness.