JNats and Other Natural Stones

[ken hatch]

While natural stones have been around much longer than synthetic stones they are not as easy to classify and to understand. The other thread on the forum about Ark stones sent me to the shop this afternoon to check a couple of things out. I like natural stones for honing and polishing and will normally use man made stones to grind. For grinding the most important thing is speed with less importance for the scratch pattern as long as it isn't too deep or inconsistent. For honing and polishing speed is pretty far down the list, what is important is the scratch pattern. How deep, how steep, and how random the scratches left by the stone are the three things that determine the quality of the cutting edge.

Synthetic stones are easy, a 5,000 or 10,000 grit stone is, within reason, pretty much like any other stone of the same grit. So the sharpening process is easy to figure out, a 1000 grit to grind, a 5000 grit to hone and a 8000/10000 to polish and it makes little never mind what make of stones you use. Heresy I know, one of the reasons civil wars are so ugly is because they are fought over such small differences.

With natural stones grit has no meaning. Sometimes you will see a grit range assigned to a stone but what that is telling you is the stone may give a finish similar to a synthetic stone of that grit range. The only real test is to take metal to stone and see what it does.

With Ark stones specific gravity can be a good starting point, the higher the specific gravity the finer the stone will usually cut. With JNats hardness can be a clue but so many things can affect the quality of the finish the only way to know if a stone is a soul mate is to use it. The reason for that is in the structure of a JNat. A synthetic stone is made of sized grit particles that break free during the sharpening process and while they will break down some they remain more or less square particles. A JNat cutting particles are flake like and while they do not change much in size in the slurry they do get thinner and because they are flake like the scratch pattern is smoother.

This is just my opinion with nothing to back it up but one of the reasons synthetic stones give such a shinny surface is because of their sharp sided scratches. With JNats some of the most prized stones leave a Kasumi or cloudy surface. In fact my favorite JNat finishing stone isn't very hard but it makes slurry very easily and leaves a beautiful Kasumi finish and edges that last a long time.

ken

[Jim Koepke]

On one of my visits to Hida Tools while living in the SF Bay Area they had some JNats for sale on display. Most were comparable in size to a foot ball. The prices were comparable to a down payment on a small car.

jtk

[ken hatch]

On one of my visits to Hida Tools while living in the SF Bay Area they had some JNats for sale on display. Most were comparable in size to a foot ball. The prices were comparable to a down payment on a small car.

jtk

Jim,

Large stones and collector grade stones can be expensive. If you are willing to work with smaller and/or irregular stones the cost isn't too bad. In their defense, even the smaller and irregular stones sure are pretty .

ken

[Jim Koepke]

Jim,

Large stones and collector grade stones can be expensive. If you are willing to work with smaller and/or irregular stones the cost isn't too bad. In their defense, even the smaller and irregular stones sure are pretty .

ken

In my situation it would have to be a dissatisfaction with my current stones or a case of the hots for a sharper edge before another stone is purchased.

Before that happens my intention is to purchase some of the micron sheets from Lee Valley to see if having an edge that can shave hair is really better if it can get into competition in a hanging hair test.

jtk

[Rob Luter]

In my situation it would have to be a dissatisfaction with my current stones or a case of the hots for a sharper edge before another stone is purchased.

Before that happens my intention is to purchase some of the micron sheets from Lee Valley to see if having an edge that can shave hair is really better if it can get into competition in a hanging hair test.

jtk

I can vouch for the abrasive films. Not sexy, not pretty, but they flat out work. I have them mounted on glass blocks that are mounted on MDF. They cost less than a down payment on a used car. What’s not to like?

(I’d still like a nice Jnat, but I’m saving for retirement.)

C4F59DE8-DAEF-4F08-87E8-DC8F20978F95.jpg

[ken hatch]

Rob and Jim,

I need to order a couple of the micron sheets to see what the scratches and the scratch pattern looks like. I know diamond plates leave terrible scratches but I see these are not diamond but standard industrial abrasives. I'll give 'em a go, I don't think they will change my mind about polishing with a natural stone but as my dear sweet mamma would say "you never know till you try it".

Rob,

Money is over rated

ken

[Jim Koepke]

Money is over rated

It may be over rated but it sure is nice to have a bank account full of it.

jtk

[Tom M King]

If you're talking about the diamond lapping films, any scratches you see will have been left by the surface they were on before being used on the film.

Do be aware that even if you start going forward on the diamond lapping film, and it seems to be working okay, the edge will quickly become so sharp that it cuts right down through the film. After slicing up my first ones, I try to remember to only go backwards.

The other films LV sells have much tougher backs. I use them for polishing things like hydraulic rams, and mating surfaces for seals, since the backing is tough enough to use as if you were shining a shoe. The diamond lapping film backing won't do that.

If you thought the polish was good from a fine synthetic stone like a Sigma 13K, it only gets brighter on the diamond lapping film, as well as sharper. If your finest stone is as fine as that 13k, you only need the .5, and .1 micron diamond lapping films. I'm not sure where you would start with another finish water stone.

Since so few strokes are needed on the diamond lapping film, it can last for a very long time. As much sharpening as I do, I think I still get over a year out of them. I usually forget, and slice them up before they're worn out.

I have a friend coming back from Japan that is supposed to be bringing me a fine JNat to play with. I'm anxious to see what it will do, but have little patience for building slurries. My waterstones go under running water, and go to work.

[ken hatch]

Tom,

A couple of things about your new JNat. If it is a very good stone the odds are you will be disappointed it the "shine". Some of the most prized JNats leave a "cloudy" finish. I don't want to get too far out over my skis here because I do not have the equipment to confirm what I believe. But I have seen images made by others that support it, one set posted yesterday #15 on the What is the Finest Ark Stone thread posted by Warren Mickey shows a razor polished by an Ark Translucent and one polished by a Shapton 15000. Of the two I expect the Shapton will shine like a newborn's bottom while the Ark will be slightly dull but of the two the Ark Translucent will have the longer lasting edge. A couple of years before David Savage died he posted on his blog about the difference between cutters sharpened with JNats vs. synthetic water stones. He also published high magnification photos of the cutters and while the synthetic sharpened cutter had more shine the JNet cutter had a smoother cutting edge. I believe the difference comes from the shape of the cutting particles and the shape of the scratches left behind. Synthetic grit tends to be squarish where JNet's grit is more flake like also when you work the slurry it tends to flatten the flakes causing the JNet flake like scratches to be more rounded and not reflect light as well as the sharper edges of the synthetic scratches. One other thing about JNats there is nothing magical about them but each stone is different and there is usually a learning curve to get the most out of your stone, don't give it one go and throw it in a box. Take the time to learn the stone and you will be rewarded.

Of course I could be full of it and free free to point it out if I am.

ken

[Rob Luter]

Rob and Jim,

I need to order a couple of the micron sheets to see what the scratches and the scratch pattern looks like. I know diamond plates leave terrible scratches but I see these are not diamond but standard industrial abrasives. I'll give 'em a go, I don't think they will change my mind about polishing with a natural stone but as my dear sweet mamma would say "you never know till you try it".

ken

I think you'll be favorably impressed. I work the grits from the coarse to the fine with just a few strokes on each. The result is a mirror finish.

Rob,

Money is over rated

ken

I agree. I just want to live a simple life. Make stuff, eat regularly and live indoors.

[Tom M King]

Tom,

A couple of things about your new JNat. If it is a very good stone the odds are you will be disappointed it the "shine". Some of the most prized JNats leave a "cloudy" finish. I don't want to get too far out over my skis here because I do not have the equipment to confirm what I believe. But I have seen images made by others that support it, one set posted yesterday #15 on the What is the Finest Ark Stone thread posted by Warren Mickey shows a razor polished by an Ark Translucent and one polished by a Shapton 15000. Of the two I expect the Shapton will shine like a newborn's bottom while the Ark will be slightly dull but of the two the Ark Translucent will have the longer lasting edge. A couple of years before David Savage died he posted on his blog about the difference between cutters sharpened with JNats vs. synthetic water stones. He also published high magnification photos of the cutters and while the synthetic sharpened cutter had more shine the JNet cutter had a smoother cutting edge. I believe the difference comes from the shape of the cutting particles and the shape of the scratches left behind. Synthetic grit tends to be squarish where JNet's grit is more flake like also when you work the slurry it tends to flatten the flakes causing the JNet flake like scratches to be more rounded and not reflect light as well as the sharper edges of the synthetic scratches. One other thing about JNats there is nothing magical about them but each stone is different and there is usually a learning curve to get the most out of your stone, don't give it one go and throw it in a box. Take the time to learn the stone and you will be rewarded.

Of course I could be full of it and free free to point it out if I am.

ken

Yes, I understand that. I don't care a thing about the shine. I only care about the working edge. I've seen those high magnification photos, but will reserve any facts based on them, one way, or the other. It will be interesting to sharpen two identical planes with each, and see, in my hands, if there is any difference in longevity of edge under work. I don't expect there will be. I'm not biased one way, or the other to start with, so believe that will make a difference. I'm not big on theory, but on producing work.

I have a lot of experience using both Arkansas stones, and different water stones. The sharper edge wins. You mentioned Shapton's, but I don't currently own any of them. Being a feel sharpener, they are second up from the bottom of my list of preferences, only being above diamond stones.

As far as taking the time to learn the stone, someone will be paying me if I'm working. I won't burn their money for nothing. If it takes minutes to get one to work, I probably won't use it more than once.

It will be a while until the opportunity comes up for me to make a fair test. I will be doing other things than woodworking for a while. Knowing that a plane sharpened on the system I've been using will work for half a day planing Cypress, I'm anxious to see how much longer one sharpened on a JNat will last. My nationality will play no part in the results.

[JohnM Martin]

I'm just getting into natural stones - Arkansas/Washita to be more specific. So far, I'm still in the learning stage but am getting good results from a couple of new stones. I recently bought a Soft and a Black from Dan's and I really like them. I really like the tactile feedback from the natural stones (especially the black) when freehand sharpening. It is a little hard to explain but it just seems more solid, a little easier to find the bevel, etc... The shine is definitely different. I see the mirror polish from waterstones and more of a hazy/cloudy finish coming off of the Black Arkansas. I added an labeled vintage (what I believe to be a) Washita stone to the lineup this week and it might soon split time with the soft arkansas. I still have a lot to learn with these stones, but I'm enjoying them.

[Dave Zellers]

I'm just getting into natural stones - Arkansas/Washita to be more specific. So far, I'm still in the learning stage but am getting good results from a couple of new stones. I recently bought a Soft and a Black from Dan's and I really like them. I really like the tactile feedback from the natural stones (especially the black) when freehand sharpening.

That's what I have- a soft and a black from Dan's. Absolutely love them. Regarding tactile feedback, pulling a knife across my soft Arkansas feels real and makes sense. Pulling a knife across my black Arkansas feels like honing on a cloud. But there is no better way to slowly erase a wire edge.

[Andrew Pitonyak]

If you're talking about the diamond lapping films, any scratches you see will have been left by the surface they were on before being used on the film.

Do be aware that even if you start going forward on the diamond lapping film, and it seems to be working okay, the edge will quickly become so sharp that it cuts right down through the film. After slicing up my first ones, I try to remember to only go backwards.

The other films LV sells have much tougher backs. I use them for polishing things like hydraulic rams, and mating surfaces for seals, since the backing is tough enough to use as if you were shining a shoe. The diamond lapping film backing won't do that.

If you thought the polish was good from a fine synthetic stone like a Sigma 13K, it only gets brighter on the diamond lapping film, as well as sharper. If your finest stone is as fine as that 13k, you only need the .5, and .1 micron diamond lapping films. I'm not sure where you would start with another finish water stone.

Since so few strokes are needed on the diamond lapping film, it can last for a very long time. As much sharpening as I do, I think I still get over a year out of them. I usually forget, and slice them up before they're worn out.

I have a friend coming back from Japan that is supposed to be bringing me a fine JNat to play with. I'm anxious to see what it will do, but have little patience for building slurries. My waterstones go under running water, and go to work.

So I popped on over to the Lee Valley site and took a look:

https://www.leevalley.com/en-us/shop...d-lapping-film

So you can buy one sheet of each 15, 3, .5, and .1 for $28. Or, you can buy them one at a time for $6.30, $6.30, $9.10, and $9.10 respectively.

[Jim Koepke]

So I popped on over to the Lee Valley site and took a look:

https://www.leevalley.com/en-us/shop...d-lapping-film

So you can buy one sheet of each 15, 3, .5, and .1 for $28. Or, you can buy them one at a time for $6.30, $6.30, $9.10, and $9.10 respectively.

Those are tempting. My Norton 8000 stone is usually listed at 3µ. So maybe one of these days temptation will get me to spring for a few 0.5µ & 0.1µ sheets, just for fun and experimentation.

jtk