Testing grit rating of a JNAT?

[mainaman]

My 330mate Ohiro Suita works fine as a finisher. It isn't as fine as my Karasu from MMJP, but it's finer than my Karasu rubbing stone from Maxim and my Konyama Razor Hone from Dicks, and almost as fine as my Asagi Tomo Nagura from Chef Knives To Go (I think that's where I got it). That's just grit though. The shape is odd (about 5x5 or so... The part I USE is like 4x3"), and it needed lapping when I got it, but it is almost as easy to use as my Konyama Razor Hone (which is damned easy to use).

Of course this isn't a Random stone. It was sold individually, rated at 5++++ grit, and noted as an excellent stone for final finish on Razors. It was also quite affordable thanks to it being such a weird size and shape.

I still prefer my MMJP Stone, because it is finer (pretty ridiculously fine in actuality), but the 330mate suita is still a nice finisher.


Now my RANDOM stone ($25 "Razor Size" 330mate eBay listing), isn't a great finisher. It's a bit too coarse. It's a very very fast mid-range hone. If you're spending $25 and expecting a great Razor finishing Jnat shipped from Japan (meaning the seller is probably getting ~$10 for the stone), then I want to live in such a world. It gets used occasionally, but I actually prefer coticules for that range of honing, so it's mostly retired.

Great, now here is the counter example,
I too got a 5++++ stone that was not one of the random e-bay stones and was also listed as a razor hone but it is nothing more than a prepolisher. Mr. Nakaoka does not test the stones on razors to be sure they are good finishers, so it is very much a hit and miss no matter what he tells you.

 

[Joe Edson]

My 330mate Sword Stone from eBay was nothing more than a pre-polisher for the methods I tried. It degraded a coticule edge on the couple times I've used it.

Granted, I didn't give it much chance.

On my second attempt with my Oozuku Asagi from maxim on a Japanese Coral razor from JimR I got impressive results to say the least. One of the best edges I've put on a razor.

Definitely was worth it to me to get the peace of mind and pay a little more for an excellent quality stone.

Edit: Oh my eBay stone was rated 5+++ and I included in the auction checkout that I wanted something for razors.

 

[professorchaos]

Back to the OPs question ...

... If you have a hard stone and raise a slurry with another hone (I use a little DMT), the slurry will break down as you hone. Thus the edge gets much more refined than if you were using the hone with water only.

Which is to say that a Japanese natural hone's effective "grit," for lack of a better word, depends on how you use the hone.

 

[Stapelfeld]

Back to the OPs question ...

... If you have a hard stone and raise a slurry with another hone (I use a little DMT), the slurry will break down as you hone. Thus the edge gets much more refined than if you were using the hone with water only.

Which is to say that a Japanese natural hone's effective "grit," for lack of a better word, depends on how you use the hone.

Is this true 100% of the time? For example I have a Tsushima stone. The seller says it’s between 3,000 grit and 6,000 grit. Before someone says anything both the seller and myself know that the grit system is not the same for synthetics and natural whetstones, in this case a jnat. However, how can I get the best “highest grit” polishing from my Tsushima, by making a slurry and working it down or by water only and doing more laps?

 

[SliceOfLife]

Crazy thing is seeing how much money I spent 15 years ago on Jnats that I got rid of 5-10 years ago.

That Asagi Slurry stone though... She's still here.


Can't answer your question. I don't put too much stock into Slurry breakdown on Jnats... I kind of saw it when using Nagura, but I suspect that has more to do with the slurry getting more base stone material and less Nagura material over time than any real abrasive particle breakdown.

But there are guys here who actually use Tsushima, so they can hopefully answer.


I will say, I've never gotten more refinement from slurry on any stone of any type vs on water. I'd expect it would occur with very slow slates (for instance if you buy a paving slate and cut it into a hone) because it helps the abrasion keep up with edge wear by having more free/exposed abrasive particles... but on actual good hones? Not something I've ever seen.

 

[Steve56]

how can I get the best “highest grit” polishing from my Tsushima, by making a slurry and working it down or by water only and doing more laps?

I’d start with light slurry, work that down, then rinse everything off and use clear water to finish with. You could just use clear water only, but a little slurry speeds the process up.

 

[JPO]

I used my Tsushima Nagura benchstone today. My stone feels a little dry when I dilute the slurry to clear wather. It's also not doing anything good for the edge.
I get the best results if I finish with slurry.
I have only tried this stone, so yours might be different.
I also tried 600 grit diamond plate slurry. There was not a big difference. So, it might work well to speed up the process.
I always lap these stones before I use them, so instead of flushing down the slurry it might add something if you follow up with some base stone slurry.

 

[Stapelfeld]

I used my Tsushima Nagura benchstone today. My stone feels a little dry when I dilute the slurry to clear wather. It's also not doing anything good for the edge.
I get the best results if I finish with slurry.
I have only tried this stone, so yours might be different.
I also tried 600 grit diamond plate slurry. There was not a big difference. So, it might work well to speed up the process.
I always lap these stones before I use them, so instead of flushing down the slurry it might add something if you follow up with some base stone slurry.

We might have similar stones. Mine also feels dry on the razor with water only. With slurry it feels like it helps it glide better across the surface of the bench stone. Last night I went from the 1.5k bevel setter into the Tsushima with the slurry from the lapping (I also lap before every hone even if it’s just a little) I did work with the slurry but felt the edge get better as the slurry got diluted down. I learned that once my razor starts to feel sticky to the stone it’s better to stop.

 

[Stapelfeld]

I’d start with light slurry, work that down, then rinse everything off and use clear water to finish with. You could just use clear water only, but a little slurry speeds the process up.

Thank you Steve I will try that. So far I’ve been using the heavy slurry left by my atoms 400 and I lap vigorously so it’s a heavy slurry. I will rinse some of that and use a milkier slurry instead of a heavy one and see if that gives me better results.

 

[JPO]

If you have a relative new atoma 400, I think it might be a little to harsh on the edge.
I used a worn dmt diasharp fine. I still got better results off a asano nagura. Most of the slurry seemed to com from the base stone.

 

[Steve56]

Generally speaking, you don’t need a lot of slurry on decent JNats. Maybe watery skim milk slurry on a midgrit, but with finishers I usually use just enough slurry to see. On a finisher, I can see the edge through the slurry on the first few strokes.

 

[Stapelfeld]

Generally speaking, you don’t need a lot of slurry on decent JNats. Maybe watery skim milk slurry on a midgrit, but with finishers I usually use just enough slurry to see. On a finisher, I can see the edge through the slurry on the first few strokes.

Alrighty! I’m sold, there is a saying that sometimes less is more and I will try that out on my jnats. Cheers!

 

[JPO]

Alrighty! I’m sold, there is a saying that sometimes less is more and I will try that out on my jnats. Cheers!

It will also depend on the speed of the base stone and the amount of work you are doing. If you use it after an 8k as a finisher you don't need much, and you might also benefit from a surface that is not freshly lapped. It might help to smooth out the surface first.
If you are doing more work, you might need more slurry.
The slurry density might be as important.

 

[rhgg2]

I am still a beginner but from my observations:

The slurry breakdown is good and bad, it allows you to refine your edge further but it means the honing is time sensitive. If you get to the end and realise you've been missing the toe you are in trouble because the slurry is now too fine to fix it properly.

You need enough slurry so the blade's refinement matches the fineness of the slurry as it breaks down. More slurry of the same density will break down slower, so you have more time if more work is needed, but you have to hone longer.

Thicker slurry, of the same amount, will also do more work, but may take the edge backwards. I'm not sure but my impression is that the speed of breakdown is similar to a thinner slurry, so you hone for the same amount of time.

I generally go for the thinnest slurry that seems to be doing something, and adjust the quantity until I feel like it gets to "finished".

 

[Gamma]

Is this true 100% of the time?

Yes. An edge is a sum of the parts and the quality of that edge relies on the skill of the user . Just buying a $5000 Jnat does not mean you get a $5000 edge automatically.

For example I have a Tsushima stone. The seller says it’s between 3,000 grit and 6,000 grit.

That's the general spot people view that stone in. Typically, TBN were woodworkers stones, affectionately called Ocean Blue, and used for sharpening tools to about what a synthetic stone of that grit would deliver. They were not considered to be finishing stones and not relied on for sharpening fine edges.

Before someone says anything both the seller and myself know that the grit system is not the same for synthetics and natural whetstones,

The measuring system for 'grit' with synths can be done many ways and different numbers can result. The numbers on the box a stone comes in is not absolute. One brand's 3000x stone might be similar to another brand's 5000x stone and a 3rd brand's 1500x stone. Natural stones do not have the same sort of makeup or abrasive and really do not have 'grit'. So it's not that there is a difference in grit systems, it's just apples and oranges and only synths have a 'grit system'.

in this case a jnat. However, how can I get the best “highest grit” polishing from my Tsushima, by making a slurry and working it down or by water only and doing more laps?

Depends on where the edge is before you start on the TBN. Typically, I find "particle break down' or 'working it down' is not a thing with these stones. Dilutions can help bridge the gap slowly. Slurry is used more as a bridge to get refinement from a coarser stone up to a well prepped, very smooth and extremely flat TBN's working surface.

 

[Stapelfeld]

Yes. An edge is a sum of the parts and the quality of that edge relies on the skill of the user . Just buying a $5000 Jnat does not mean you get a $5000 edge automatically.

That's the general spot people view that stone in. Typically, TBN were woodworkers stones, affectionately called Ocean Blue, and used for sharpening tools to about what a synthetic stone of that grit would deliver. They were not considered to be finishing stones and not relied on for sharpening fine edges.

The measuring system for 'grit' with synths can be done many ways and different numbers can result. The numbers on the box a stone comes in is not absolute. One brand's 3000x stone might be similar to another brand's 5000x stone and a 3rd brand's 1500x stone. Natural stones do not have the same sort of makeup or abrasive and really do not have 'grit'. So it's not that there is a difference in grit systems, it's just apples and oranges and only synths have a 'grit system'.

Depends on where the edge is before you start on the TBN. Typically, I find "particle break down' or 'working it down' is not a thing with these stones. Dilutions can help bridge the gap slowly. Slurry is used more as a bridge to get refinement from a coarser stone up to a well prepped, very smooth and extremely flat TBN's working surface.

Thank you Keith for this detailed answer to many of my questions! I have kept working on the TBN for practice with a cheap gold monkey and feel more comfortable with it but still far away from mastering it. I recently did a jump from the TBN to coticule and it gave me a smooth shavable edge, not super keen like a synthetic 12k but on the other hand they are two different stones and you can't expect the same outcome from them. Thank you again for the detailed answer. Kind regards from Puerto Rico