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

[algebro]

Hey all,

I'm learning JNats following @Gamma 's excellent guide on his website and while Botan and Tenjyou were no problem at all, I'm having a bit of trouble at the Mejiro stage.

I've found that the nagura won't make a slurry when rubbed flat against the base stone no matter how long or hard I try. The only way I can get a reasonable amount of slurry is to tilt the nagura a bit so that I'm making contact with a smaller part of the stone at a steeper angle.

Is there any drawback to doing this? I was a bit concerned about uneven wear or the lacquer sealant possibly getting into the slurry but I'm not sure if those are actually problems.

Thanks!

 

[Herrenberg]

Have you tried soaking the nagura?

 

[Steve56]

Also try ‘de-glazing’ it, run it across a worn 320 DMT/400-1200 Atoma. Some of the modern Mikawa shiro nagura are very hard.

 

[algebro]

Have you tried soaking the nagura?

I have not--is that recommended? I was under the impression these stones would absorb water and split, which was why people seal them with cashew lacquer

 

[Steve56]

I have not--is that recommended? I was under the impression these stones would absorb water and split, which was why people seal them with cashew lacquer

This is completely wrong for shiro nagura.

Shiro nagura are not layered stones, so the Japanese do not seal them. They get nasty over the years if you buy used lots of them lol. I do minimally lacquer mine, just to keep them clean and to keep them from abrading and drying my skin.

Tsushima black nagura will split and is typically lacquered and or reinforced with lacquered mulberry paper (washi). But not shiro (white) nagura.

 

[musicman980]

Morio Sakamoto, the owner of the Asano stamps, recommends soaking harder nagura for 5-10 minutes prior to use. They are chalky stones though, so I wouldn't be surprised if a prolonged soak turned a Mikawa nagura into mush.

I've tilted my harder nagura on their edges for slurrying without issue though, just watch your pressure.

 

[Matt O]

I thought soaking nagura was crazy until one of our friends recommended it…I tried it…loved it…and do it every time I use them now!

 

[Steve56]

A couple of things to keep in mind.

If the nagura is absorbing water it will stick to the stone. If it sticks to the stone, there’s a really good chance that it will tip, especially if the nagura is tall. If it tips it will scratch or gouge the hone. If it scratches the hone, you just put large particles into the slurry, rinse, wash, and repeat without the gouging.

If either the hone or the nagura are absorbing water, they’ll stick and this is a bad thing.

I don’t think that Mikawa will turn to mush, but maybe Gifu/Gujyo might? IDK, not enough experience with those shiro nagura yet, they’re pot luck to find. Fine Tools in Germany lists some Gujyo, but I have not tried them because of the US shipping cost. I do have other Gujyo.

 

[Dagabose]

Hey all,

I'm learning JNats following @Gamma 's excellent guide on his website and while Botan and Tenjyou were no problem at all, I'm having a bit of trouble at the Mejiro stage.

I've found that the nagura won't make a slurry when rubbed flat against the base stone no matter how long or hard I try. The only way I can get a reasonable amount of slurry is to tilt the nagura a bit so that I'm making contact with a smaller part of the stone at a steeper angle.

Is there any drawback to doing this? I was a bit concerned about uneven wear or the lacquer sealant possibly getting into the slurry but I'm not sure if those are actually problems.

Thanks!

This is how I use all my nagura. I’m no expert, but I’ve never had any issues.

I have a slight bevel on all of mine. I just tilt it and make slurry.

 

[Gamma]

The usual approach is to lap the working surface of the nagura so it is slightly rounded.
It is possible to tip the Nagura to get slurry, but having more surface area to work with distributes the pressure more evenly.
Lap the lacquer back away from the working surface.
You can soak Mikawa nagura, but if you leave them in too long they can turn to mush, split, or crumble.
No need to submerge them, just enough water to cover the working surface.

 

[algebro]

Thanks for the suggestions everyone, I've already learned a lot in this thread.

The usual approach is to lap the working surface of the nagura so it is slightly rounded.

Just to make sure I'm understanding, would you do this by rubbing the nagura on a DMT at an angle all around the edges? Or do you mean something like using your hands and a sheet of w/d? Usually when I think of "lapping" I'm used to that meaning making sure it's flat, but in this case it sounds like we want it to make a face convex.

 

[Dagabose]

Thanks for the suggestions everyone, I've already learned a lot in this thread.

Just to make sure I'm understanding, would you do this by rubbing the nagura on a DMT at an angle all around the edges? Or do you mean something like using your hands and a sheet of w/d? Usually when I think of "lapping" I'm used to that meaning making sure it's flat, but in this case it sounds like we want it to make a face convex.

Here is a picture of one of mine. This was already done when I purchased it. It came from a very reputable and experienced person. I hope it helps. I have others I can take pictures of if you need more examples.

 

[H Brad Boonshaft]

“Just to make sure I'm understanding, would you do this by rubbing the nagura on a DMT at an angle all around the edges? Or do you mean something like using your hands and a sheet of w/d? Usually when I think of "lapping" I'm used to that meaning making sure it's flat, but in this case it sounds like we want it to make a face convex.”

Yes, dome and smooth the nagura stone face, mine are much more domed than Dagabose’s, so that I am using more of the corner of the nagura in a bit of a rolling action.

I used a 140-grit diamond plate to shape, but any diamond plate or Wet & Dry will work. I refine/smooth with 400 and 600 plates.

You do not want sharp corners or facets, where the nagura will contact the stone, they can chip and leave large grit in your slurry.

You do want some flatish surfaces, because in addition to making slurry you want to use the nagura to flatten and smooth the base stone. Doming the nagura will also prevent stiction.

I do soak, dip in bowl of clean water, tomo and Mikawa for better slurry. I do not seal any of my nagura, there is no need.

You want to experiment with the amount and thickness of your slurry for best performance with your base stone. I rarely use “thick” slurry and find it easier to add slurry or make new slurry as needed.

Do not fall into the grit trap of stamped nagura, they are natural stones and can/will perform differently with each base stone. Mikawa are not grit rated, though there is/are some generalities in stamped nagura. There is some contention by users which grade is finer. Finishing ability is more in the hands of the honer and in the synergy of slurry from both stones.

 

[algebro]

Great, thank you. BTW, here are a couple pictures of the working surface in case that helps. If it looks "domed enough" to you all then I may just proceed with soaking first.

 

[Dagabose]

Great, thank you. BTW, here are a couple pictures of the working surface in case that helps. If it looks "domed enough" to you all then I may just proceed with soaking first.

View attachment 1723086View attachment 1723087

I would get some sandpaper or flattening plate and lightly remove the lacquer on the rounded edge area. I’m not sure how lacquer would impact and edge if it’s mixed in with the slurry. I would lean on one of the veterans here to help us with that question. Definitely would be a fun experiment.

 

[JPO]

If the nagura is not generating slurry fast enough, it might help if you start off with a minimal amount of water on the stone. You can add more water afterwards when you get some slurry on the stone.
In some cases the nagura and the base stone is not a good match. I have a hard Mejiro that needs a really hard base stone to work well. On some softer jnats I just use a tomo nagura.

 

[Gamma]

Just to make sure I'm understanding, would you do this by rubbing the nagura on a DMT at an angle all around the edges? Or do you mean something like using your hands and a sheet of w/d? Usually when I think of "lapping" I'm used to that meaning making sure it's flat, but in this case it sounds like we want it to make a face convex.

Don't overthink it...

"The usual approach is to lap the working surface of the nagura so it is slightly rounded."

Yes, rounded.
Whatever process you want to use to round off the working surface is going to work just fine.

When I need to, I usually roll the Nagura around on a diamond plate. But I have used w/d also.

 

[algebro]

Don't overthink it...

Don't underestimate my ability to ruin expensive shaving equipment

I'll try the DMT, thanks!

 

[rhgg2]

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)

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.

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?

 

[JPO]

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)

View attachment 1726736

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.

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?

I would just chamfer and round off one, or two edges.
This is some of my relatively large naguras.