Mejiro Nagura Won't Slurry Flat Against the Awasedo...OK to Slurry at an Angle?

[rhgg2]

So do you basically use the chamfered edge or edges as the nagura, and the rest of the stone as a giant handle?

Also now wondering if I could cut off a normal nagura-sized chunk and just turn the rest into a koppa:

 

[JPO]

So do you basically use the chamfered edge or edges as the nagura, and the rest of the stone as a giant handle?

Also now wondering if I could cut off a normal nagura-sized chunk and just turn the rest into a koppa:

View attachment 1726886

So do you basically use the chamfered edge or edges as the nagura, and the rest of the stone as a giant handle?

Yes. If you are using it flat you can generate enough suction force to crack the stone if there are lines in the stone.
I would just cut off a piece, and create a smaller nagura.

 

[H Brad Boonshaft]

If you want to keep the stone and use as a Kopa, I would preserve the long edge and cut off the other side where there is already a crack or inclusion line. It will cut easily with a regular hack saw.

Straighten and round the longer straight edge to use for honing, smooth and round off all sides and edge of the new nagura.

But first I would try the stone as a Nagura, it may bet that other nagura, tomo or Mikawa will work better with your base stone and all the extra work is moot. Just because they look similar does not mean they will produce the “best” edges for you. They are all natural stones…

Or as said just round off all the corners and use as it. As a nagura use the side/corner without Kawa and round off all the corners to prevent kawa flaking when making slurry.

 

[Gamma]

I have a related question. The Ozuku koppa I recently got from Maksim came with a tomo nagura which is itself koppa-sized (images pre-lapping)

Koppa is an uneven shape, not really a size. Most people associate the term with hand held size stones but a big stone that is not rectangular is still a koppa.

Seems like a nice problem to have, but at the moment it is too flat to be very usable as a slurry stone. It's doable, but it takes forever to get anywhere, separating the stones is a bit hairy, and even when done successfully heaps of the slurry ends up on the slurry stone.

it's really more about surface area and flatness than it is about flatness alone. To separate, slide one stone sideways and/or spin the stone to get it to move. Do not pull up or on an angle. When a smaller nagura 'sticks' it is usually easy to slide off. Larger stones are always harder to move around and sometimes they 'lock' so it is to be avoided.

I'd rather not cut it up if I can avoid it, so I guess I need to round it somewhat. With a small stone it's pretty obvious what rounding would mean, but I don't know how to scale this up. The nagura is 130 x 90 mm. I'm thinking if I took down like a 20mm border at each edge to a gentle but pronounced curve that might do it. Just enough that I can roll the stone a bit. But maybe I need to bring it in more than that as it's still going to be a pretty big flat area in the middle. Any advice?

If you are going to use a larger heavier stone as a Nagura, whatever part you want to make slurry with should have a larger radius than you would make for a smaller stone. The idea is that you want to use more surface area, not less. A greater bearing surface will help prevent uneven wear on the base stone, deep gouging, etc. With a smaller piece of stone it is easier to use an edge with a tighter radius. The entire surface should be smooth and clear, without porous lines in the working zone.

Do not put a lot of work into it until you have proven that the nagura stone is worth the effort. You'll need many honings to be sure of that. Then, if it proves itself, clean up all of those edges. Cutting your Nagura stone is a gamble, It may want to fissure. You have one area where there is a line leading from a notch. I would try to cut on that line. I would use the piece that comes off as a Nagura if it isn't jacked up inside. Sometimes there are rust/inclusion veins running through the stone and you really do want clear stone without odd particulate in it.

To get a good curve out of an edge on that nagura stone, start with a 45° chamfer on one edge until it yields clean stone throughout. Make the chamfer 3/8" wide, or wider. I would probably go for wider. Then roll the hard lines out so it's a smooth curve.
Tidy up the whole piece, smooth all exterior lines. Then seal all edges with nail polish.

 

[lightfoot]

A nice way to prepare your large slurry stone would be to get a nice rectangular piece of plexiglass and cut it square.

Next stack two adhesive felt pads at all four corners and put one single pad in the dead center. Now you just lay a piece of sandpaper on the other side and use this is a kind of convex lapping plate. You can use this for preparing smaller Nagura as well.

Orient the plate with the corners in a north/south, east/west direction as shown.

In no time at all you will have a nice dome shape to your stone.

 

[H Brad Boonshaft]

You lost me…

Or just round the edges with a diamond plate or 220 glued to a glass 12X3 tile.

Round the edges so sharp corners or kawa will not flake off, there will also not be any stiction if you use the rounded corners as opposed to a flat face.

You really do not need a lot of slurry.

Alex Gilmore had a great video on smoothing and shaping nagura, but I cannot find it. Perhaps Alex will chime in.

 

[lightfoot]

You lost me…

Or just round the edges with a diamond plate or 220 glued to a glass 12X3 tile.

Round the edges so sharp corners or kawa will not flake off, there will also not be any stiction if you use the rounded corners as opposed to a flat face.

You really do not need a lot of slurry.

Alex Gilmore had a great video on smoothing and shaping nagura, but I cannot find it. Perhaps Alex will chime in.

Yeah you don’t need something like this for smaller in Nagura but for rounding over the surface of larger stones this little contraption is extremely expeditious.

 

[Christian1212]

Cut it into multiple slurry stones. Keep 1 for yourself then try and trade the others for different slurry stones to play with. Big tomos are nice but there is definitely a point where it is too big. I think my ideal tomo size would be 3 inches long to cover the stone but only 1 inch or so wide/thick, so 3x1x1. But there are a bunch of fun sizes and shapes

 

[Gamma]

A nice way to prepare your large slurry stone would be to.....

Just lap a chamfer into the stone's edge with a diamond plate and then round it off with that same plate.

Seriously, I have prepped several hundreds of all types of Nagura this way.

You don't really even need a diamond plate, it can be done with flat piece of wood and some w/d paper. In Japan, miners would sometimes use a small hatchet to shape Mikawa Nagura.

 

[lightfoot]

Just lap a chamfer into the stone's edge with a diamond plate and then round it off with that same plate.

Seriously, I have prepped several hundreds of all types of Nagura this way.

You don't really even need a diamond plate, it can be done with flat piece of wood and some w/d paper. In Japan, miners would sometimes use a small hatchet to shape Mikawa Nagura.

Yeah I roll my smaller Nagura on a D-plate in all directions. Doesn’t take long to get a good dome shaped profile.

Just thought my cheap convex plate was a quick way to do odd shaped larger stones that aren’t really practical to use as a hone.

I have a rather large and extremely soft Nagura that you could almost use as a hone but it’s just a little beyond what would make sense.

If I could cut a good square or rectangle out of it I would just roll it on a plate end to end, side to side, & corner to corner.

We always have a bunch of those felt pads in our “fix it quick” bin so the plexi-plate was a fast project.

 

[Gamma]

No need to complicate a very simple process.
Large or small stones will be rounded off easily with a diamond plate or w/d on a hard surface.

 

[rhgg2]

Ok, tidied up the edges and made a big chamfer on the edge with no kawa. Used 120 wd on the back of an atoma plate, then 240 wd to finish. Sealed with wet look paving sealer. Using the working edge it now actually rubs against the base stone rather than gliding over it. Seem okay?

 

[H Brad Boonshaft]

Here are the 2 Alex Gilmore videos on making/shaping tomo nagura.

And how to groove them so you can raise slurry on larger flat stones without creating stiction.

I radius a corner to about that of a Quarter so stiction is not an issue and I can vary the slurry, alternately abrading from the face or the layered end grain.

On a lager flat tomo you can also make the stone convex by lightly grinding the edges and using the stone in a rocking motion so the whole flat face is not making contact with the base stone face. If it gets stuck, slide it off an edge as opposed to trying to lift it from the base stone.

How to shape and prepare a Tomonagura

Shaping of a 2 x 2 inch stone to be used as a tomonagura

 

[Gamma]

Ok, tidied up the edges and made a big chamfer on the edge with no kawa. Used 120 wd on the back of an atoma plate, then 240 wd to finish. Sealed with wet look paving sealer. Using the working edge it now actually rubs against the base stone rather than gliding over it. Seem okay?

What matters is how it feels, not so much how it looks.
It does look fine, but how it feels is what matters.
You can judge the feel when using it. Should be smooth, but there should be a friction that allows slurry to form.
But no grinding feeling.

I would strongly advise against cutting grooves in your Tomo...

What that does is weaken the stone, and create more edges that can deteriorate into chips that are problematic in the slurry.
It's a completely unnecessary and possibly problematic complication.

Your rounded surface is the typical approach. It prevents glazing and eliminates the possibility of creating a vacuum that can cause the stones to get stuck. It also perpetuates itself through use so you really should only have to do it once.

That's one of my older Tomos.... one long side and one short side have been rolled so I can make slurry with a broad sweeping motion or use the short end for a more focused approach.
That's all that needs to be done. This is the common traditional approach.

 

[Steve56]

You really do not need a lot of slurry.

Yepper.

 

[Gamma]

Ha - I am just realizing that there are two different posters with similar nagura issues in this thread.

So, @algebro was the OP with the Mikawa nagura question, and then @rhgg2 has the big Tomo.

They are similar situations, but different enough too... identical mechanics needed for both tho...

The idea is to be able to slurry freely, without putting too much pressure on the stones.
You may need, or want to use a lot of slurry, or not, depending on what you want to do and how you like to work. You always do need enough slurry to provide a completely even refinement. Some Tomo get better results when a bit more slurry is generated, others less. With Mikawa Nagura, well - Botan slurry I might use more than I do Koma, but it can get complicated because I might do several sessions, split sessions, a double gainer, or whatever.. so I might wind up using more Koma slurry actually.

Remember, 'a lot of slurry' does not refer to 'thick slurry'.

But no matter how much slurry needs to be made, the idea is to not use much pressure to get there.
The curve allow you to glide into the slurry development, as opposed to grinding.

@algebro
The pic of your MIkawa nagura looked like it was 'started off', and if it slurries ok then it's fine. If not, maybe round it off more. It's not a visual thing, it's a practical thing. The curve has to work, sometimes the curve needs to have a wider radius, other times not. Only the user will know for sure. Don't cut into it, seriously, it's just not a good idea. Been there, done that, seen the light. Rounding off the bottom is the way to go.

@rhgg2
my previous post was in reference to your Tomo pix.

Here's a few more pix of a couple other Nagura from the magic box...
You can see the curve on this Kiita Tomo is uneven. Still works well like that though.

This large Uchi, maybe 450 g or so, has a tight radius for it's size but the stone slurries easily so I didn't need to make a bigger curve.

This Mejiro has a weird curve that is nearly flat in the middle. It started off like the one in @algebro 's pic but has since taken on it's own shape with use.

That's it... that's all that is needed, not a lot of work really. Don't need templates or fancy directions, and don't need to be 'perfect'.
All that is needed, is to get a curve in the stone that allows it to roll into the task. That's is. Simple stuff.
KISS - keep it super simple....

 

[rhgg2]

Thanks! I realised as soon as I started using it that there is no point in fussing over the minutiae because using immediately changes the shape of the curve. Also that: with a 650g nagura you really don't need to add any pressure of your own; and that I should probably roll it slightly while using to stop any sharp corners from developing that might chip off.

 

[JPO]

Sometimes it helps to start generating slurry on a stone with a minimal amount of water. The water acts as a lubricant. As the stone and nagura starts to release slurry you just add some water.
On other stones and/or nagura combinations it really doesn't matter if you start with a soaked stone.
I have a midrange lv 3.5 stone. This is more suitable for knifes, and was sold as a knife grade stone. This stone actually cuts faster with a minimal amount of water, and just some light slurry. Adding too much water makes the stone almost ineffective with razor honing pressure. However, when used with knifes it matters less as you can compensate by using more pressure.
Every stone has a learning curve, and the nagura use needs to be adjusted slightly to get the best performance out of them.
As everyone does not have the luxury of having a large collection of naguras, we need to maximise the potential of what we have. A good vendor might find a good match for you.

 

[Gamma]

with a 650g nagura you really don't need to add any pressure of your own; and that I should probably roll it slightly while using to stop any sharp corners from developing that might chip off.

Yes.