Thread: Shoobie Doobie Asagi

Originally Posted by Lesslemming

That is a tough one. I´d like to think of the 1-5-system as an inter-japanese-natural system only.
The system works fine as long as you compare japanese naturals to one another.
Once you apply the system to other stones, or even synthetics things become screwed up.


Now my Naniwa Superstone 10k is a moderately soft stone.
Harder than the Supersotne 8k, softer than any shaptons.
Herein I understand hardness as the resistance to scratching and the toughness of lapping.

Usually the Superstones lapp very easy.

Now the peoples hone is one tough bumm to lapp.
It took me hours to lapp mine. It seems I got a hard one... (wait, this sounds stupid)

The Chinese hone is extremely dense and quite hard, when honing on it I feel nothing but glass.
No feedback or anything. That makes me think of it as being hard.
If it really is hard, I do not know.

Now the Superstone 10k feels very smooth and even a little velvety on the razor.
This makes me instantly wanna say: soft.

My Nakayama Maruka/Maruichi Kiita gives me a similar feeling, velvety smooth.
But raising slurry on it is quite hard. So this makes me think of hard and soft at the same time?!

What I want to say is, what we feel when honing and what we think of as hardness
is not necessary the same thing. How am I supposed to rate what is hard and what is not?

Because japanese naturals are somewhat similar to one another (same binder, if you want)
you can quite easily compare these to one another.

The hardest one I have being the Shoubudani. It feels very hard to the touch, and very dense. Knocking on it gives me the feeling of knocking on something very hard.
Raising a slurry with a hard tomonagura is quite a task. It takes some time and it releases only
very little slurry. With water only the Shoubudani seems not to release any particles,
since I understand that these would diminish the previous polish and make it either scratchy or hazy. Now my Nakayama Kiita does not release slurry fast, either. But with water only
I get a tiny and light scratch on the bevel every now and then, when honing for a long time (lets say 50-100 laps).
I think of this as being a result of released particles.
This and the velvety smooth feel make me believe that my Nakayama Kiita is a bit softer than my Shoubudani.
I would say Shoubudani Asagi lv5, Nakayama Kiita lv4+
Remember, my Nakayama is still very hard. But I came to realize there are higher RPMs out there, so I had to adjust my rating.
B/c if my hard Nakayama would be lv5 already, what would my Shoubudani be? And what would an Ohzuku be??

My Oohira is an extremely quick cutter, you can see swarf on it quickly,
when used with water only for sharpening my kitchen knives.
The stone instantly produces a hazy finish, which I believe is due to the release of particles.
So I would rate this one at lv4.

My Suita is yet quicker and releases slurry easily. I would give it a lv3+


Coming back to comparison between non j-nats and j-nats:
I cannot gouge or scratch any of my naturals (j-nats or Chinese) with my larger knives,
while sharpening free hand. I cannot do this with my shaptons, too.
But the Naniwas I can cut easily if I am not carefull

Does this come near the answer to your question?

Thanks for the detailed post. Based on what you are saying , I would
guess the Chinese hone to be harder than your Nakayama kiita and Oohira,
but slightly softer than your Shoubu. Would you agree?

Sharpman

Unfortunately I can not agree. This is because there is no real consens of how hardness of a stone is defined and how it is measured.
And of course we do not know how hardness effects the performance of a stone (there only is a consens of how hardness is rated for j-nats).

But what I can say is this:
of all my stones I want the Chinese to be the last that ever needs thorough lapping
(giving the fact that neither my Nakayama, nor my Shoubudani have been really in the need for lapping,
although I have lapped my Nakayama a bit and would say it was easier than lapping my Chinese)

Where are you going with this, why the comparison of the hardness of the Chinese (mine, anyway) to that of Japanese?

Originally Posted by Lesslemming

Unfortunately I can not agree. This is because there is no real consens of how hardness of a stone is defined and how it is measured.
And of course we do not know how hardness effects the performance of a stone (there only is a consens of how hardness is rated for j-nats).

But what I can say is this:
of all my stones I want the Chinese to be the last that ever needs thorough lapping
(giving the fact that neither my Nakayama, nor my Shoubudani have been really in the need for lapping,
although I have lapped my Nakayama a bit and would say it was easier than lapping my Chinese)

Where are you going with this, why the comparison of the hardness of the Chinese (mine, anyway) to that of Japanese?

Well I have the naniwa 8k stone and that one is too soft for me. My
plane blade gouges in the stone(freehand honing). That's why I asked
about the hardness of your 10k in comparison to the other stones and
especially to the asagi.

I also have an interest in buying the people's hone, since it is cheap and
many feel it is very fine, hard, good quality. So the hardness of that stone
compared to the shoubu was interesting for me as well.

Another thing I found interesting was that I read in another topic that the
people's hone(one particular) was about Lv3 which I found a bit weird since
many people say it is so hard to lap and also soaking won't help as the water
cannot penetrate it.

Maybe you can check hardness by rubbing the natural stones together and
see what colour slurry is produced. The softer stone(AFAIK) will create the
slurry more, whereas the harder stone will produce less slurry.

Just found this interesting information on hardness:
ROCK HARDNESS CLASSIFICATION - MOHS SCALE

Sharpman

Originally Posted by SharpMan

Well I have the naniwa 8k stone and that one is too soft for me. My
plane blade gouges in the stone(freehand honing). That's why I asked
about the hardness of your 10k in comparison to the other stones and
especially to the asagi.

I also have an interest in buying the people's hone, since it is cheap and
many feel it is very fine, hard, good quality. So the hardness of that stone
compared to the shoubu was interesting for me as well.

Another thing I found interesting was that I read in another topic that the
people's hone(one particular) was about Lv3 which I found a bit weird since
many people say it is so hard to lap and also soaking won't help as the water
cannot penetrate it.

Maybe you can check hardness by rubbing the natural stones together and
see what colour slurry is produced. The softer stone(AFAIK) will create the
slurry more, whereas the harder stone will produce less slurry.

Just found this interesting information on hardness:
ROCK HARDNESS CLASSIFICATION - MOHS SCALE

Sharpman

Are you sharpening western planes or Japanese?
As far as hardness one can't compare Jnat to C12k, coticule Escher or anything else but another Jnat, it is like comparing apples to oranges.
Your proposal of test by rubbing two stones will not work unless the slurries are different color because how will you be able to tell which slurry you are looking at? A more sensitive test will be to make a very light scratch on each stone and see which one will smooth faster, that stone will be the softer one.

Originally Posted by mainaman

Are you sharpening western planes or Japanese?
As far as hardness one can't compare Jnat to C12k, coticule Escher or anything else but another Jnat, it is like comparing apples to oranges.
Your proposal of test by rubbing two stones will not work unless the slurries are different color because how will you be able to tell which slurry you are looking at? A more sensitive test will be to make a very light scratch on each stone and see which one will smooth faster, that stone will be the softer one.

Stefan, I sharpen both japanese and western plane blades.

Why can't one compare the hardness of a coticule or C12k to a Jnat. Hardness
is hardness AFAIK.

Makes sense about the colour of the slurry, indeed if both stones have the same colour,
it will be very difficult to see.

I like your scratch test. What about rubbing two stones together when completely dry?
Wouldn't the softer stone get a rougher surface?

Do you think calculating the density has any relevance? For example one stone
is 20cm by by 5cm by 5cm and weighs 1000grams. So the stone is 500 cm3 volume.
Weight per cm3:
1000/500=2grams

the other stone is .........
.............
1.9grams per cm3. So this stone is softer than the above. Could this work?

Sharpman
1000/480

Originally Posted by SharpMan

Stefan, I sharpen both japanese and western plane blades.

Why can't one compare the hardness of a coticule or C12k to a Jnat. Hardness
is hardness AFAIK.

the binders are different so no it is not the same. The absolute way to test is to measure the hardness of the grit particles.

I like your scratch test. What about rubbing two stones together when completely dry?
Wouldn't the softer stone get a rougher surface?

try and see if it will work but I feel wet will be better

Do you think calculating the density has any relevance? For example one stone
is 20cm by by 5cm by 5cm and weighs 1000grams. So the stone is 500 cm3 volume.
Weight per cm3:
1000/500=2grams


the other stone is .........
.............
1.9grams per cm3. So this stone is softer than the above. Could this work?

Sharpman
1000/480

The hardness also is determined by how compact the stone is, the very hard ones are also very very fine because they are more compressed than the others. So if you have two identical size stones(of the same type J-nar , C12k etc.) the finer one will also be heavier.

As far as planes there are two things to consider, aesthetics and practicality.
Japanese planes are two metal construction, soft iron and hard steel. When you use a Jnat to sharpen if you care about good finish on the soft iron you need a stone that is not going to scratch but at the same time is hard enough to provide flat bevel. Typical plane stone will be lvl 4.5, but if you want a very good stone you need lvl 5 or more which will be very expensive. Such hard stone will also be good for razor so if you are looking for multi-functional stone that will work for your tools and razors you need to prepare to spend money.

The reason your SS does not work well on your planes is it is too soft, you need harder synthetic such as GS or Shapton Pro ( I hear the Pros are very hard but could be wrong). If you want to go the natural stone way, you have a few choices, Arkansas stones are great stones for tools , or you can go for coticule, or you can go for one mid level prepolisher and in any of the cases one very hard finisher. Another finsher option would be a CF.

Hi Sharpman,

Why can't one compare the hardness of a coticule or C12k to a Jnat. Hardness
is hardness AFAIK.

that´s where you´re off track. When you say hardness is hardness, then what is hardness?
I have a bit of a metallurgical and material science background and can tell you it is not that simple.
Hardness is not clearly defined and cannot be measured directly. Especially when you take into consideration that a sharpening stone is a mixture
of several compounds withvery different hardness.
There are several ways of telling a value for hardness like HRC, Vickers (indention), Mohs (scratching) etc.
and all of these values are incomparable.
That´s because they are committed to a specific cause

So technically we have to make our own system of telling what is hardness for our cause.
Now that I know where you going at, I can help you with that.
Our cause is now freehandsharpening and we want to test if a stone can withstand the
indention or cutting of a badly angled blade (ie. will it get gouged?).

Of all my Sharpening stones I have to be most carefull with my naniwas when freehandsharpening.
There is no way you gouge a Shapton, or an Asagi, or a Nakayama.
My Oohira is far beyond that as well. And never in live will the Chinese hone be cut into!

For this purpose (resistance to gouge) I would rate these the following:

Naniwas: 2-3 (gouge easily, but resist wear) [Naniwa 5k: 2; Naniwa 8k: 2,5; Naniwa 10k 3]
Shaptons: 4-5 (resistant)
Any natural I had so far: 5 (100% resistant) *

When I speak of density I do not necessarily speak of specific gravity, but of the closeness of the particles.
Again there is a difference in makro and micro scales.
In micro scales the atoms and molecules of a substanze have a specific distance to each other which closely relates to the specific gravity we can measure.

But a sharpening stone may consist of grains of matter. In each grain, the particles are packed according to their natural specific gravity.
But if the grain itself has a distance to it, then the Volume is increased.
Let me explain with polystyrene, the substance Styrofoam is made of.

What weighs more, 1 m³ (Volume) of Water, or 1 m³ (Volume) of Styrofoam?
Of course we know the answer, it´s water.

Water has a specific gravity of around 980 kg/m³. 1 m³ Water weighs in at around 1.000 kg.
Styrofoam is made entirely out of polystyrene which has a specific gravity of 1050 kg/m3.
So 1 m³ polystyrene weighs more than 1m³ water! How is that possible?

The polystyrene gets foamed, air or gas is trapped between little grains of polystyrene.
The volume is increased but the mass stays nearly constant.

So the corrected density of Styrofoam is 20 kg/m³, 1 m³ will weigh in at about 20kg.

Apply this to a sharpening stone.
There are grains, and when I speak of density of a stone I speak of how closely these grains are packed


*but remember:
Natural stones do vary. I do not know of a sginle someone who gouged his chinese 12k, though