NSK DIAMOND STONES

[KenjiF]

I have a few hard diamond stones (naniwa 400 and venev 80/150) and I can see the utility for polishing. I am thinking about investing in a few NSK stones and wanted to see what grits and lines and hardnesses you all find most useful. My current thinking is that the coarser grit ones will be the most useful where you want the bevel setting to be the most accurate and to save time flattening and wearing through multiple stones. Do people find the higher grits useful? I was thinking about starting it a 400, 600 and 1k. Any recs?

 

[ethompson]

I’d be surprised if anyone who posts here frequently has more experience than I do with these at this point. Owned a full set for a few months and have had most of the variations. Used enough to have required flattening multiple times and to have made noticeable wear in the coarser ones.

They’re good, maybe great stones, but not a magic wand. Compared to really good synthetic stones, there isn’t a huge difference in performance in most instances. I think they really shine in two specific cases.

First is precision coarse bevel work. The sub 1k stones are no faster than the fastest synthetic stones (a debado 180 will be faster than nsk200 in my experience) but they release far less slurry and offer greater wear resistance than traditional synths. This can give you more precise transitions without running the risk of wearing away KU or making a fuzzy shinogi. There are synths that are as precise, there are synths that are as fast if not faster, but firm diamond stones are the best bet in terms of balancing the two for polishing. The other is managing hardened steel / especially honyaki. Scratch clean up is definitely easier with these and I find the speed favorable and predicable.

I have a full set 200-6k and would say they’re a luxury rather than necessity. I like them a lot, I’ll replace them when I wear them out, but I’m not confident they’re objectively worth the premium compared to good synthetics especially above 800-1k grit.

What I’ve had
• 200 hakuto
• 200 kyokuha
• 400s hakuto
• 400 kyokuha
• 800 hakuto
• 800 kyokuha
• 1.5k hakuto
• 3ks hakuto
• 3k hakuto
• 6k hakuto
• middle fine Oboro

I think at 200 you want soft, 400-1.5k I’d lean towards std hakuto in 1 hardness, 3k+ the s softness might be good and above 6k I’d maybe start exploring the 2 hardness hakuto.

Happy to answer other questions too if you have specifics.

 

[Up_dog128]

If you are only talking about setting edge bevels, then perhaps 400 would suit you fine.
I do a fair amount of wide bevel thinning and polishing these days, so consider that when reading my reply. I find 400 grit to be too slow for thinning and flattening or creating wide bevels; you would def want the 200 for this, imo. Or something even more aggressive, tbh. Even though I own the coarser venevs, I still find myself using my SG120 or 220 sometimes when I really need to hog off material, as they are just faster, more aggressive stones.
I also wouldn't find much utility in having both a 600 and a 400. Personally, I would find it more useful to have a 200, 600 and 1k or 200, 400 and 1k. And I do find the mid-grits useful, to continue with the accuracy you mentioned as I move up thru the progression. The only higher grit diamonds I own are the much less expensive diamond plates, although I've been thinking lately of trying to trade one my low grit Venevs for something finer.

This might also be useful info to you that I got from Josh at Tosho:
"Based on memory and experience the Shapton (glass) stones will cut faster but they are not nearly as consistent and require flattening substantially more frequently. So in essence you'll save money and time using the NSK." Regarding the Hakuto and Kyokuha lines "They are entirely different lines of stones. If you solely want to do surface work (thinning and polishing) then the Hakuto are a better choice. If you would also like to do edge work the Kyokuha are a more all-round stone.
An additional note, if you do intend to purchase NSK stones you will need to purchase an NSK flattening implement, whether it be the puck or the corresponding and correct grit for the stone.
This is because NSK stones will destroy any other flattening implement you use on them."

 

[KenjiF]

Thanks, @ethompson! Exactly what I was looking for. Sounds like you recommend the newer Hakuto series? I think ill start sub 1k and maybe explore others later on then. I'll trade a slightly slower cutting performance if it means less time removing the scratches with the next stone unless I'm tackling something that needs aggressive work. I probably do 2-3 hours polishing a week atm so get thick ones?

@Up_dog128 Right now if I'm thinning I am using a Debado 180 followed by the 150 Venev and I agree that the 180 debado is faster than the 150 Venev.

I think I saw Milan 'dressing' his diamond stones with a coarse synth mud to speed it up in one of his videos. I've tried sic on my Naniwa diamond 400 and it definitely speeds it up but will dish it significantly faster.

 

[ReiHamono]

One thing to consider is that if you’re having to flatten your stone that certainly slows down the process, so the overall process is not faster if you have to flatten the stone as you work.

Also, if the stone is soft and causes errors that you have to go back and fix, again it’s not faster, it’s actually slower.

When reviewing, it’s highly important that you recognize the whole process in its entirety.

If you’re not having to flatten, or go back and fix mistakes from soft stones, then certainly that subtracts from the overall time of the process.

Also, consider that NSK hakuto stones leave a very consistent and easily recognizable scratch pattern to identify any issues with the bevel. Most “soft” stones are not going to do that.

Also, we can not compare the 180 debado with the 200 hakuto, the grit is not the same and 180 debado is highly inconsistent so you must find a “soft” one that’s soft through the entire stone. A lot of them are just very hard stones or soft in certain parts of the stone, making them absolutely inconsistent.

Finally, if you want faster than the 200 hakuto, try the CGSW 90 grit diamond stone.

 

[ethompson]

@KenjiF I’d recommend the thick ones for sure. More economical in the long haul. If you do enough polishing to have consumed a coarse traditional stone you’ll definitely eventually use up multiple mm of an NSK. For 200 I may prefer the kyokuha as it’s the softest and easiest to keep conditioned and cutting well. 400 is still fast enough to clean everything up ultra precisely. Definitely Hakuto 1 or 1s for 400-1.5k in my opinion.

You also need a way to dress them. An atoma will make things worse and destroy your atoma. Maybe the nanohone stuff would work. NSK sells theirs. I just use coarse sic and glass and it works great.

 

[Rangen]

One of the strange side effects of owning a supersteel razor (CPM-M4) is that you can actually be tempted into buying the 10K NSK. So I have one, in the highest hardness. It works well on the razor, and also visually validates my experience that diamond stones will make occasional rogue scratches, considerably deeper than the usual. For that reason, I am surprised anyone wants diamond stones for polishing at all.

My main point is: I have the NSK 10K, and am willing to perform experiments if anyone wants to know what is like, since I imagine that few will be buying it.

Oh, and don't use CPM-M4 in your razors. The edge chips too easily.

 

[ethompson]

Interesting! After surface conditioning I actually haven’t had any issues with rouge particles on my NSK stuff that I couldn’t attribute to grit contaminant from storage.

 

[Rangen]

Interesting! After surface conditioning I actually haven’t had any issues with rouge particles on my NSK stuff that I couldn’t attribute to grit contaminant from storage.

Well, we're observing in different worlds. What I'm talking about is based on razor bevel observations under a microscope for grits no lower than 1K. Those rogue scratches are highly consequential on a razor, because if you don't get them out, you wind up with a little chip out of the edge, for each scratch, when you hoped to see a clean and consistent edge after your finisher. So you tend to notice every rogue scratch, and the pattern produced by every kind of stone.

 

[ethompson]

Well, we're observing in different worlds. What I'm talking about is based on razor bevel observations under a microscope for grits no lower than 1K. Those rogue scratches are highly consequential on a razor, because if you don't get them out, you wind up with a little chip out of the edge, for each scratch, when you hoped to see a clean and consistent edge after your finisher. So you tend to notice every rogue scratch, and the pattern produced by every kind of stone.

Fair enough! Razor guys are for sure a different breed

 

[KenjiF]

Is Tosho the only supplier for the stones? Looks like I’m going to have to wait for a restock…

 

[KenjiF]

I tried to make a deal with myself that I won’t buy a honyaki until all my San mai knives have flawless bevels and polishes but nice to know I’ll be set up for those too @ethompson

 

[ethompson]

Is Tosho the only supplier for the stones? Looks like I’m going to have to wait for a restock…

Tosho is your best bet

 

[Hassanbensober]

Is Tosho the only supplier for the stones? Looks like I’m going to have to wait for a restock…

https://www.japaneseknifeimports.co...nes/products/diamond-300a-stone-and-flattener

 

[M1k3]

I think @milangravier might rival @ethompson for diamond stone experience

 

[ethompson]

I think @milangravier might rival @ethompson for diamond stone experience

Definitely exceeds me in experience at with the coarse stuff and blows me away with skill at all levels. Not sure he’s gotten the full kit all the way up to mid grits and finer though. Which proves they aren’t necessary for nice polishing!

 

[milangravier]

Hey,
I got NSK Hakuto 200, hakuto 400s, Hakuto 800 and 200 flattening plate for about 5 months. Same period I bought the 80 + 150 Venev (and could try 240, 400, 800 from a friend).
NSK are great stones for people who want to sharpen and shape their knives, wide bevels knives mostly. They cut very well, they go on cutting for a very long time. They tend to dish a little fast for my idea of perfection but it is manageable.
200 is really a great stone : I think my best flat stone in that coarse range, better than Venev (because faster, softer and keep cutting), better than Debado (which is close in speed but will dish far faster). I really like the work that stone is doing, even if I would be glad that NSK make a 150 or a 100 grit.
400s : is a bit too soft for a cladded knife, it will abrase very quickly (maybe my fastest 400) but will also make mud with iron super fast and you'll dish the stone pretty quickly, that one I think is better for honyaki. (I will buy a 400 normal, someday). I use it with a lot of water on clad knives.
800 is a great stone too. Feel hard and glassy if you use it with too much water but is great with little bit of slurry. You can have a very clean bevel after it.
200 flattening plate: is good without being awesome : it is fast to flatten other stones but it is dishing a little too and you don't want a flattening plate to dish or move at all. I have to flatten it about 4 times or more in 5 months.

I did not test the other grits. I would be interested to try the 1500, not sure about the 3k, 6k as a synthetic stone can do the job I need I would say, but I'll be happy to try them. After nsk 800, I use Naniwa pro/chosera 1k. You can go finer directly like I think the naniwa pro 3k could erase the nsk correctly but I prefer a tight progression.
Two issues with diamond stones in general, so with NSK too :
1. they burnish your bevel. which should be an advantage! well it is, you can really see your scratch pattern and see if you erased your previous grits, compared to synthetics it is much better ! BUT ! One issue I got often is that because they burnish they tend to hide high spots. Because they are so abrasive and contact with the blade is great, you don't feel that your bevel got a part which is too convex, where there is too much material, and when you switch to a synthetic you realise that this part is super burnishing and you won't be able to get an even finish if you let it like that.
2. they are expensives so you hesitate to flatten them. Yes, they are very expensive and they are not that thick material. So for very precise work where you would like a super flat surface, they are not ideal as you gonna put a lot of the material to the bin (to the sink) if you flatten them often. With Synthetics like Naniwa pro, I feel it is much more a peace of mind to flatten them, given their price and thickness, so when I need a really flat surface, I prefer synthetics. I will flatten the naniwa 400, use it for 2 minutes, flatten it, use it for 2 minutes etc. I can't do that with NSK, it would be too painful

 

[KenjiF]

Hey,
I got NSK Hakuto 200, hakuto 400s, Hakuto 800 and 200 flattening plate for about 5 months. Same period I bought the 80 + 150 Venev (and could try 240, 400, 800 from a friend).
NSK are great stones for people who want to sharpen and shape their knives, wide bevels knives mostly. They cut very well, they go on cutting for a very long time. They tend to dish a little fast for my idea of perfection but it is manageable.
200 is really a great stone : I think my best flat stone in that coarse range, better than Venev (because faster, softer and keep cutting), better than Debado (which is close in speed but will dish far faster). I really like the work that stone is doing, even if I would be glad that NSK make a 150 or a 100 grit.
400s : is a bit too soft for a cladded knife, it will abrase very quickly (maybe my fastest 400) but will also make mud with iron super fast and you'll dish the stone pretty quickly, that one I think is better for honyaki. (I will buy a 400 normal, someday). I use it with a lot of water on clad knives.
800 is a great stone too. Feel hard and glassy if you use it with too much water but is great with little bit of slurry. You can have a very clean bevel after it.
200 flattening plate: is good without being awesome : it is fast to flatten other stones but it is dishing a little too and you don't want a flattening plate to dish or move at all. I have to flatten it about 4 times or more in 5 months.

I did not test the other grits. I would be interested to try the 1500, not sure about the 3k, 6k as a synthetic stone can do the job I need I would say, but I'll be happy to try them. After nsk 800, I use Naniwa pro/chosera 1k. You can go finer directly like I think the naniwa pro 3k could erase the nsk correctly but I prefer a tight progression.
Two issues with diamond stones in general, so with NSK too :
1. they burnish your bevel. which should be an advantage! well it is, you can really see your scratch pattern and see if you erased your previous grits, compared to synthetics it is much better ! BUT ! One issue I got often is that because they burnish they tend to hide high spots. Because they are so abrasive and contact with the blade is great, you don't feel that your bevel got a part which is too convex, where there is too much material, and when you switch to a synthetic you realise that this part is super burnishing and you won't be able to get an even finish if you let it like that.
2. they are expensives so you hesitate to flatten them. Yes, they are very expensive and they are not that thick material. So for very precise work where you would like a super flat surface, they are not ideal as you gonna put a lot of the material to the bin (to the sink) if you flatten them often. With Synthetics like Naniwa pro, I feel it is much more a peace of mind to flatten them, given their price and thickness, so when I need a really flat surface, I prefer synthetics. I will flatten the naniwa 400, use it for 2 minutes, flatten it, use it for 2 minutes etc. I can't do that with NSK, it would be too painful

Thanks Milan! That’s interesting that the burnish hides the high spots I hadn’t thought of that. I like to switch between fast soft stones and hard burnishing stones in my progression now so I can easily see the lows when I switch stone. Maybe if I get the NSK 200 use chosera 400 and back to NSK 800 that will be a good progression for me… until I can afford all the stones!! Your videos
on the coarse stones are great and what inspired this search for them!

 

[ReiHamono]

Switching soft hard may be the best way and may keep speed the highest