Nubatama Recommendations (Medium-to-High Grit)

C

cm_bushman

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Oct 22, 2012
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I'm a diamond sharpener at heart, but lately I've been looking into waterstones to really finish the edges on some of my knives (especially my Japanese kitchen knives) on my new Edge Pro.

I really like what I've heard about the Nubatama stones that Ken Schwartz is offering, and so was wondering if anyone had any recommendations on a few stones to try and finish an edge off of a DMT EF or EEF. I was planning on starting with the Ume Speckled 2k, since it's comperable grit to the EF, and then going up to a 5k and then an 8-10k, but I don't know which of the options to try. There are so many choices between Bamboo and Ume, medium and hard, etc., that I'm lost.

So any guidance on what ind of higher-grit options to go for with Nubatama? I'm looking for fast cutting and slow-wearing stones as possible, which shouldn't be too much of a concern with these grits anyway.
 
What do you sharpen mostly?

The Nubatama lineup is extensive and you can pick out a progression of stones to fit your specific needs. For general EP use I would go something like this.

150 bamboo , 1k speckled ume , 2k speckled ume , 5k bamboo , 10k bamboo

You can always contact Ken directly to have his take on the matter , he prefers helping customers pick out stones to suit their individual needs , part of why the Nubatama lineup is so extensive.

Typically when we move over from diamonds to waterstones one doesn't go back to diamonds to finish off. Remember that diamonds scratch much deeper than their waterstone counterparts. I would go up to your EF then drop down to the 1k speckled to start working out those diamond scratches , then progress and finish off on the waterstones. Your other option with the lineup I recommended is to start with the DMT XC or XXC (whichever you have) then to move onto the 150 bamboo. It will make short work of those diamond scratches , quickly converting them to a waterstone scratch pattern , allowing you move on with your progression without worrying about diamond scratches showing up in the 5k-10k stages.

There's also a 15k bamboo that's an excellent stone , but it is quite pricey. They are produced in a low volume and are hard to produce , and subsequently hard to cut safely for the EP.

As another alternative you could come off the 2k speckled and progress onto some Japanese Naturals. Something like a Monzen or Aono Aoto leaves a nice finish. Depending on what steels you play with of course.
 
Actually I think you've navigated through the choices quite nicely :) And I agree with what sadden has said as well. If you have any questions regarding your choices or availabliity, just contact me directly anytime. I can give you a bit more guidance if you are referring to single bevel knives, but for double bevel knives, the selection you've picked is fine.

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Ken
 
Monday I will be receiving my Ume 4k which will complete my most current set of Nubatama stones. With the Ume 4k I will be using the bamboo 150 and Ume XXHard 1k, all of which are hard but extremely fast cutting. I have a feeling it will be a difficult set of stones to surpass. Review to come.
 
Sadden said:
What do you sharpen mostly?

The Nubatama lineup is extensive and you can pick out a progression of stones to fit your specific needs. For general EP use I would go something like this.

150 bamboo , 1k speckled ume , 2k speckled ume , 5k bamboo , 10k bamboo
Click to expand...

Thanks for the solid progression, Sadden!

It will be a wash really, as far as knives and steels go. everything from Shirogami 1 to k390. I'm looking for hard stones, slow to dish because of the carbide-rich steels, and splash-and-go if possible, because my diamonds have spoiled me.

I'll probably let the diamonds do the heavy lifting and skip the 150, will it be okay to skip the 1k for now as well? I know the scratches are deeper for diamond, but the 9 micron rating puts the DMT just below JIS2000, and I've always heard it was good practice to convert scratches at the equivalent grit to avoid overlap.

Jason B. said:
Monday I will be receiving my Ume 4k which will complete my most current set of Nubatama stones. With the Ume 4k I will be using the bamboo 150 and Ume XXHard 1k, all of which are hard but extremely fast cutting. I have a feeling it will be a difficult set of stones to surpass. Review to come.
Click to expand...

I have read (from your post on CKTG, it seems) that the Bamboo 5k is a soaker, and pretty soft to boot. I was looking at the Ume 4k as an alternative, and I'm awaiting the review. Is the 10k Bamboo harder, or should I look at something else for hard, splash-and-go performance?
 
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"I have read (from your post on CKTG, it seems) that the Bamboo 5k is a soaker, and pretty soft to boot. "


[video=youtube_share;wNbOSpViFl0]http://youtu.be/wNbOSpViFl0[/video]


Here's a video of the 5k Bamboo that gives you my perspective on this interesting stone. You can also find videos for nearly all of the Nubatama stones on youtube simply by typing a google search for :

'youtube kenneths123 Nubatama 5000' or whatever grit number you like and narrowing it down from there.

For example
'youtube kenneths123 Nubatama 4000' for both the ume and bamboo 4k stones or
'youtube kenneths123 Nubatama ume 4000' to narrow your choices a bit more

'youtube kenneths123 Nubatama 10000' will also likewise help you to review that stone.

---
Ken
 
Thanks Ken, that was a real "Duh" moment for me there! I have watched a few of the videos and it seems the 5k is indeed a bit soft, but the 10k is pretty much splash-and-go and harder as well, that's good news! Now I just need to nail down the (maybe 1k), 2k, and 4-6k options for my EP!

So I've read the speckled 2k is harder than the "Olive Brick of Joy", and so I'm guessing it will be a better option for the harder steels, is this the case? The video on the Speckled 1k was very positive, aside from the slight soak period.
 
Bushman,

Yeah it's a soft stone and not too much different from most every other run of the mill stone. I have not used any past 5k so I can't comment on them.
 
Bushman,

In the comments associated with the video:

"I begin 'touching up the Blazen. The stone is a hard stone. It is hard like a 5k Shapton, but with more feedback. There is no danger of cutting into the stone because of its hardness. It is MUCH harder than say a 5k Chocera . We do get a fine metal swarf pretty quickly. The finish produced is shiny / mirror. Very slow water absorption. It is also comparable to the hard to extra hard Nubatama Ume 1k speckled stones in terms of stone hardness. Unlike the Shaptons, you do get some mud buildup giving a denser slurry. The metal swarf component of the slurry is microscopic in size. I continue sharpening as the edge becomes increasingly sharp. "

I don't find this stone a soft stone. You will get different impressions from different users, as you do with any stones out there.

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Ken
 
The 5k bamboo is nowhere near a Shapton or Chosera in hardness. No danger of cutting into the stone? That's BS. I sharpened about 10,000 knives last year with the bamboo 5k, wore more than half of it out doing so, it's no harder than a Arashiyama 6k or ice bear 4k. It might have a similar feel to a Shapton but that's about where the similarities stop.
 
Jason, the 5k Chocera is a significantly softer stone than EITHER of these other two stones. And among the Choceras it is the softest one of that series. I will RESPECTFULLY disagree with your assessment and just say that in MY hands, cutting into the Nubatama 5k or Shapton 5k is not something that will happen. On a bad day I have cut into a Chocera 5k. Of the three, the Shapton 5k is hardest, followed closely by the Nubatama 5k and the Chocera 5k much softer than either of them. IF you got 10k knives out of the 5k Bamboo, I'd RESPECTFULLY suggest you might be contradicting yourself.

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Ken
 
"So I've read the speckled 2k is harder than the "Olive Brick of Joy", and so I'm guessing it will be a better option for the harder steels, is this the case? "

Not necessarily. So the hardness of a stone isn't directly correlated with how well it works on harder steels. Even the term harder steels is unclear - HRC or Rockwell hardness and abrasion resistance are two different issues and not to be considered as one.

You are correct in that the Olive brick (2k Ume) is a softer stone than the Ume speckled. The olive brick is therefore more suited to situations requiring less precise geometry - convex surfaces, irregular surfaces found on the blade roads of single bevel Japanese knives or just personal preference for a softer stone.

What is more closely correlated with working with harder steels is the abrasive type and the abrasive density. So either a soft OR hard stone with a low percentage of abrasive will be less aggressive and an abrasive harder than the carbides in the steel at the same concentration as a softer abrasive will cut more rapidly.

Hope that explanation is of use in helping you select stones for your use.

A softer stone will present a newer surface with fresher abrasives as it wears more quickly than a harder stone - so, for instance, the softer Shapton GlassStones abrade more rapidly than the Pro series at the expense of wearing more quickly. This allows a higher grit density in the slurry of fresher abrasive particles. This is not to say GlassStones are soft - just less hard compared to their Pro series counterparts. The older Shapton stones like the M5 series stones were BOTH softer AND had lower percentage of abrasives with the net result of being a slower stone. Similarly, the Naniwa Superstones vs the Choceras have a lower grit density (and tend to be softer) with the net result that they cut slower than the Choceras. This relates overall to these two series with some exceptions. So the 12k superstone is one of the hardest among the superstones and the 5k Chocera is one of the softest of the Choceras, even moreso than the 12k Superstone. The 10k Superstone is notoriously soft and extremely easy to cut on edge leading strokes. The 3k Chocera is one of the hardest Choceras.

Not only have I been sharpening with these stone for years, in many instances since they were first introduced in this country (eg Choceras and glassstones and of course Nubatamas) but I cut and shape them too, so I do have a pretty intimate knowledge of the subject, if I might be so bold to state this fact.

As THE representative for Nubatama stones, I will also state that Nubatama stones are NOT recommended to be permanently soaked, so if you do so and get different results like stones becoming softer than what I have demonstrated, this should be considered in the results you report and may account for some disparities in results reported. Shapton stones and Choceras are also not recommended to be permasoakers either and demonstrate negative changes in their performance too.

---
Ken
 
I don't claim much skill at all with waterstones, but I think I understand sharpening in general quite well and I get good results with most of the various types of stones, plates, and belts that I have used. So this is from the perspective of someone who is still new to waterstones, but not new to the process.

I have the Nubatama Bamboo 150, Ume 1k speckled, and Bamboo 5000; the last one being the point of contention here. About half of the dozen or so times I've used the 5k, I've gouged it. Not a big gouge; hardly visible actually. But enough to make me cringe when I happens and curse myself for poor technique. I really think it's more about my technique than anything else. I've noticed that if I float water on top of the stone, as I thought was correct, that I actually lose tactile feedback and tend to have my angle vary a lot more than it should. I'm going to start trying to use that stone almost dry. Soaked briefly, but without a puddle of standing water on top.

I now have to admit that for a short time I kept all three stones soaking all day. I think I left them in a tub of clean water for 5 to 7 days, and then decided it wasn't necessary and I didn't like the idea. That's been several months now, and they sit in an open plastic container inside an air conditioned house. But Ken's comments above make me think that I may have damaged my 5k stone by it's week vacation in the water. Should I lap it with a diamond plate and remove a 1/4" of stone? Or just keep using it and try it more dry than wet as I outlined above?

I'm not sure I'm helping the OP here, but these are my experiences and my challenges with these new (to me ) tools.

Thanks,

Brian.
 
Brian, I don't think you've damaged your stones. Gouging is always a cringe-worthy event. You definitely don't want to use a Chocera 5k :) You probably wouldn't gouge the 5k Pro stone as that is one of the harder pro stones. So I'm curious - from memory did you find the 5k - or the other Nubatama stones - softer during their week long submersion than you find them to be now?

I wouldn't lap that much off of the stone(s) or really do any lapping more than maintaining flatness, but continue using it, soaking it enough to keep the top of the stone wet for the duration of the sharpening session by supplementing the water on the stone as needed. Gentle drying after use and not permasoaking and you should be fine.

In general - not just for this stone, try to maintain more precise control on your edge leading strokes with less pressure and slower more deliberate precise strokes. For extremely soft stones (like Nubatama 1200, Superstone 10000 and even the 5k Chocera) just use edge trailing strokes until you gain more confidence. You are most likely to gouge a stone when you have exceeded the bevel angle of the knife with an angle even more obtuse and continue to push forward. Even if you would have succeeded in this stroke in the sense of not gouging the stone, exceeding the ideal bevel angle would cause excessive rounding of your edge.

Thank you for sharing your observations.

---
Ken
 
ksskss said:
So I'm curious - from memory did you find the 5k - or the other Nubatama stones - softer during their week long submersion than you find them to be now?
Click to expand...

As you say, this will be from a memory that is a number of months old now. Maybe 6 months? I remember the Bamboo 150 holding water better after. Duh. :) The Ume 1k seemed essentially unaffected. But it is a really nice feeling stone anyway. It's hard to describe the combination of it being hard enough to not gouge, smooth enough to be pleasant, yet abrasive enough to remove metal fairly quickly. The Bamboo 5k was softer afterwards I think. But that could be something I made up in my head. I certainly didn't have any experience that definitively pointed to softening. That was just my feeling and I could easily have observation bias. <shrug>

Thanks for the opinion that my stone is probably ok. I'll try using it again with less water and MORE concentration. That stone reminds me of one time when I was shooting pistols with a friend. I used his custom built 1911 to shoot some steel and hit 4 in a row making that satisfying "Ting!" of the steel getting knocked down each time. After the 4th one, I thought "this gun is almost self aiming. Awesome!". Then I stopped trying so hard and fired again. I missed 2 of the next 3 targets!! The gun doesn't shoot itself. When I didn't do my job, it didn't work as well.

I think the 5k is probably a great stone and I'm just not trying hard enough. When I first got it, I got some really nice edges from it on a Richmond Gyuto and my Spyderco Tenacious. Since then I've had worse results and I can only think that initially I was concentrating harder on doing a good job because I had never used waterstones before. We shall see what I can make this stone do. :)

Brian.
 
You can gouge a hard stone like the 30k if your going fast and catch it wrong (particulairly around the tip).

Jason permasoaks many (possibly all?) Of his stones because he sharpens all day every day and does not want to subject them to rapid wet/dry cycles. This is fair reasoning for his uses. Ken has a massive (literally thousands) collection of stones. When he buys a stone he doesnt just buy one or two , he buys twenty. Uses them takes notes and then cuts and sells them , or sells them whole. For this reason he does not permasoak his stones , as this is the less risky way for him to store stones that may not be used for several months.

So Ken in your professional opinion can permasoaking a stone (such as the 5k being discussed here) change the characteristics of a stone (or some stones) enough to see perceiveable differences to the average user? Some stones would be more susceptable to this than others i would suspect.

I have some soft naturals that i doubt will live to sharpen 100 knives , let alone 1000 or even 10000. Even my 1k pro wont live long enough to see 10,000 knives.
 
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Well since I personally don't permasoak, I can just give you the colllective experience of my customers both with Nubatama stones and waterstones in general. Some stones, notably the Choceras have a reputation of developing a fine checkering pattern from permasoaking - like a dried lake bed. I personally have not had this occur. You hear this more often on the 10k but this may just be anectdotal. So this or actual cracking is a permanent change. I also don't recommend soaking porous natural stones especially soft muddy stones like aotos and polishing stones simply don't need to be soaked since they are so slow to absorb water anyhow. You just maintain water levels on the stones surface being used. It is not recommended that you permasoak Shaptons - pro or glass either and I believe (don't know) this may cause permanent changes. If I find out otherwise, I'll update this statement.

In some instances longer soaking makes the stone softer - more mushy, especially the outer portion of the stone. This may or may not be transient. I guess you could say this mushyness is a function of the stone saturation at the moment of it's use. So for instance Beston stones like the 500 pretty much require permasoaking to be soft enough to work effectively. With short or no soaking I just find them noisy but slow working for their level of grit.

I'm not really going into other issues here like too rapidly drying stones with heat, sunlight or extreme hot or cold temperature changes, all of which can have harmful effects on many types of stones.

Magnesia based stones are particularly subject to cracking or that dried riverbed type of checkering with prolonged soaking. For this reason I most strongly do not recommend permasoaking the 4k and 6k Nubatama Ume series stones. Again I have not personally seen the problem but have been strongly warned that it can occur.

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Ken
 
So Ken, for my uses, (both hard and wear resistant steels, sorry for the ambiguity), do you think I should just go with the Shaptons? Would they be faster/slower wearing in the long run over the Speckled 2k and the 4k Ume? Do you think the Nubatamas' finish is something to be valued by the entry-level enthusiast?

Or do you think that going all diamond on the EP would be the simpler/more efficent option? I could go from the EF plate to strops in 6, 3, and 1 micron, followed by your sub-micron CBN sprays if I ever got the gumption to go that low. That method bears the added bonus of never worrying about stone wear or dishing. Any downsides to this for the hobbist sharpener (2-3 sharpenings a week with a re-profile ~1-2 times a month)?
 
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CM,

It would be an interesting race. Clearly one advantage for the Nubatamas is simply size - they are thicker. The Shapton Pro stones average 17 mm thick. The Glassstones are half glass - the stone portion is about 7 mm thick and slightly faster wearing than the pro stones in general. So on longevity the Pro stones are longer lasting than the GS for the same grit.

The Nubatamas are anywhere from 25 mm (inch) thick to 30 mm to 50 mm thick - so as much as over 7 times thicker comparing say a 150 Nubatama Bamboo to a 120 GlassStone.

Just as a general rule, coarser stones wear faster for any series of stones so it is best to compare wear rates for a given grit.

So the 2k Black (actually more of an dark olive green) will wear faster than the 2k speckled but it is a thicker stone and the 2k Bamboo is not quite as hard as the 2k speckled stone but is more specialized. For your purposes, I'd suggest the 2k Speckled. Since it will generate more mud than a 2k Pro stone, it will wear slightly faster and probably cut slightly quicker than the 2k Pro. The 5k Pro stone should wear slower than either the 4k, 5k or 6k Nubatama stones, ume or pro but they are thicker.

At some point I would suggest that stone wear should not be your overriding criteria. All of these stones will last you for many years of sharpening unless you are sharpening a bunch of knives every day. I mean when's the last time you sharpened 10,000 knives? A slow wearing stone that you don't enjoy using will wear even slower because it will be the stone you don't use :) I find I prefer a bit more feedback in a stone. I find the 5k pro gives very little feedback. This was one of the first stones I owned among Japanese synthetic stones. I'm not saying I think it is a bad stone at all, but for most instances, I go for the 5k Nubatama over the other 4k and 6k Nubatamas or my 4k or 6k Glassstone or 5k pro stone because I enjoy using the stone and the results I get with it. If I am following it with a Japanese Natural stone, now it isn't even a contest - the 5k Nubatama wins hands down among all of these choices as it best preserves a Kasumi finish as well as working well with a wide range of steels too.

So now we have covered choices for harder steels pretty much. For abrasion resistant steels, I like diamond plates especially at the low end. The 140 Atoma is outstanding in this regard. It cuts fast but leaves deep scratches and stays flat. You can continue to refine the edge with finer diamond plates or convert it to a stone finish at 150 grit. Even for abrasion resistant steels diamond plates should be done in smaller jumps 140 400 600 1200. If you have to skip one, skip the 600. So from there you can go to CBN loaded strops and skip stones entirely or even start lower. So you can go as low as 80 microns in CBN which is coarse enough to follow a 220 grit belt for instance on a grinder. I have people who do this routinely on belt grinders. If you want to go into detail on a suggested sequence for using CBN, just contact me for details as I think I've already stuck a lot of info in this post and it can get confusing. There is yet another possibility of using CBN ON the sharpening stones for the abrasion resistant steels and otherwise using the stones as is for everything else. So for instance, putting a 4 micron CBN emulsion on a 4k stone (any of them) will supercharge it for dealing with S90v type steels.

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Ken
 
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