CBN sprays on waterstones

[Leo Barr]

I have just been reading that when sharpening hard steels on water stones for example Choseras once there is a build up of slurry / mud it is possible to add a drop of CBN spray to help the stone cut more easily and possible skip some of the transition stones.
Has anyone tried this? Ken mentioned this it sounds very interesting.

[Allgonquin]

I give up. What is CBN spray?

[wickededge]

I give up. What is CBN spray?

Cubic Boron Nitride. Very hard, but not quite as hard as diamond.

-Clay

[wickededge]

I have just been reading that when sharpening hard steels on water stones for example Choseras once there is a build up of slurry / mud it is possible to add a drop of CBN spray to help the stone cut more easily and possible skip some of the transition stones.
Has anyone tried this? Ken mentioned this it sounds very interesting.

I know Ken is very excited by this technique though I haven’t tested it myself. I’ll give it a go tomorrow and let you know how I fare. Is there a combo you’d like me to try?

-Clay

[Phil Pasteur]

Ken likes to find different uses for his sprays. He has been adding them to different media for a long time and likes the results.

My concern would be, in adding them to the Chosera stones, would you cause contamination that would not easily be removed. Meaning it would not wash off with the mud/slurry and I may have to lap the stones to get them back to where they were originally. I have lots of different media to use the sprays on, and I do. I am not ready to do this with my Chosera Stones. They have a character of their own, and I like it for what it is.

I will, however, be interested to see what Clay finds when he tries the method. Always ready to learn new tricks… but this one might mean buying a second set of Choseras… not quite ready to do that.

One has to remember that Ken has what is basically an unlimited supply of different types of waterstones to play with… I don’t!

[Leo Barr]

I have only read about it Ken gives the impression that by using them on the stones that it is possible to skip some of the stones through a progression it sounds very interesting it would save time and possible yield better results .
I wonder about the dosage and how long such an dosage would last ; would it do several knives and as Philip brings up would it harm the stones although unfamiliar as I am with these sprays I would not imagine that they would damage the stone rather supercharge them.
Perhaps the lower grit stones say the 600 would be a place to start since I imagine it would improve the ability of the stone negating the need for the lowest grit . So maybe 600-2K-10K for a starter or something similar.
Thanks Clay

[Leo Barr]

found a video of Ken’s ! Okay he is doing a razor so maybe try it on the 10k Chosera on one of your test razors

[Phil Pasteur]

I have only read about it Ken gives the impression that by using them on the stones that it is possible to skip some of the stones through a progression it sounds very interesting it would save time and possible yield better results .
I wonder about the dosage and how long such an dosage would last ; would it do several knives and as Philip brings up would it harm the stones although unfamiliar as I am with these sprays I would not imagine that they would damage the stone rather supercharge them.
Perhaps the lower grit stones say the 600 would be a place to start since I imagine it would improve the ability of the stone negating the need for the lowest grit . So maybe 600-2K-10K for a starter or something similar.
Thanks Clay

You haven’t mentioned what grit of the CBN to add to what grit of water stone. I have some 30 and 45 micron CBN. Neither of these would be suitable for anything above the 400 Chosera… of course that would depend on which way you were trying to “stretch” the stones effective range.

So, what grit CBN on which grit of Chosera, to accomplish WHAT?

Just let me say once more the way I feel about the Chosera stones. People generally love the Chosera stones for what they are. The combination of the specific type of abrasive and the binder leads to a specific level of feedback and a dependable scratch pattern. The progression is such that the next grit up nicely removes scratches from the previous stone and refines the edge to a very specific level. All of this while providing marvelous feedback. The progression was finely engineered to do what is does, and it does it well.

I am just not sure that introducing another abrasive to the mix will improve anything. Change things, well of course, but improve the process… likely not.

I often use the diamonds, then 600, 1000 Choseras then the 2K Aotoshi (for polish) then strop a bit and call it good. Trying to figure out where in the order and what grit of CBN would help this progression out. Just not getting it.

Leo, if Clay does this experiment, what grit of CBN do you want him to use on what grit of Chosera stone. What would you like him to compare it to determine whether a specific goal was achieved.
So, would the comparison be the 600 with 10 micron CBN versus using the 600 and then the 1K??

Want 30 micron CBN added to the 600 chosera… for what, faster scratch removal? Or maybe something like 10 micron, to see if the 1K chosera can be skipped?

For the 2K, 10 Micron or maybe 4 micron ? What do you want to do here?

10K maybe 0.5 micron CBN for a finer finish. At this level it is had to imagine that you want to add anything more coarse than the approximately 1.7 micron grit of the stone.

Just thinking, if you want to know if there is an improvement, you would need to start with a goal in mind, and design the test that would determine whether you might get what you are looking for. What you have mentioned so far does not do that.

My big concern, of course, is does adding anything to the mix have a long term effect on the stones. AND, is any perceived “improvement” worth that risk. These are Water stones. I think there is a real possibility that any CNB abrasive added could very well penetrate into the pores of the stone and change it permanently, or at least until is was lapped sufficiently to remove the contamination.

[Leo Barr]

Philip since both you & Clay have infinitely more experience of both the Choseras & the CBN I reiterate my original question-”
I have just been reading that when sharpening hard steels on water stones for example Choseras once there is a build up of slurry / mud it is possible to add a drop of CBN spray to help the stone cut more easily and possible skip some of the transition stones.
Has anyone tried this? Ken mentioned this it sounds very interesting.”
Here is Kens say on it.

This is a technique I’ve been using for quite some time now, so I thought I’d share some information about this technique.

First I’ll talk about using it on synthetic waterstones, then natural stones.

Of course the first question is – ‘Why would you do this?’

Well, more and more we are hearing about pocket knives and now kitchen knives using more and more abrasion resistant steels. And additionally ‘mules’ or fixed blade knives that are just blanks without handles or sheaths. Now we are also seeing production or semi production knives incorporating these abrasion resistant steels.

Most of these steels have an ever increasing amount of vanadium carbides in their steel formulations, including steels from Crucible metals and Böhler Edelstahl as well as other steels from Hitachi like ZDP-189 that are also pretty abrasion resistant but achieve it with very high Carbon and Chromium contents. Indeed some steels like CPM rex 121 are approximately 10% vanadium and 3.4 % carbon. While steels of this type are offering better edge retention, sharpening them has become more and more problematic.

So up until now, synthetic waterstones are often used. Mostly the abrasives in waterstones are aluminum oxide and occasionally silicon carbide. Some time ago, Shapton responded to this issue by trying to reformulate their waterstones into an additional series called Glasstones. These were specifically oriented towards use with D-2 steel. The formulation had a higher abrasive content of Aluminum oxide and a slightly higher wear rate so the particles released more quickly, producing a denser slurry.

But now we run into a basic problem. The Mohs hardness scale rates abrasives (and other substances) in terms of hardness from talc (softest) to diamond (hardest, rated at 10.0).

On this scale, compounds like Aluminum oxide, silicon carbide, chromium oxide and even Boron carbide (BC) are not as hard as Vanadium Carbide. The two abrasives harder than vanadium carbide are Cubic Boron Nitride (CBN) and diamonds. This is an extremely important concept to understand this discussion. For natural stones, which are complex abrasive mixtures of varying hardnesses and shapes the abrasives in natural stones are even softer than Aluminum oxide. It is this softness that allows natural stones to react differently to steels of varying hardness, producing the beautiful effects you see on polished swords and kasumi knife finishes with different scratch patterns on soft cladding and hard core steel. But we are getting ahead of ourselves and will get back to natural stones later.

Now when you have carbides harder than the surrounding steel matrix, the softer abrasives grind away on the surrounding matrix until the carbides are no longer supported and fall out from lack of support. I like to use the analogy of a chocolate chip cookie with the carbides being the chips and the surrounding steel being the dough. So when the dough gets worn away the chips fall out.

Now if your abrasive is harder than the chips now you are grinding away the dough AND the chips.

This produces a different KIND of edge. The chips stay in place but are formed in such a way as to be part of the geometry of the refined surface. More carbides remain to maintain the edge geometry which is also more precisely formed.

So now we come to the interesting part. What if we made a mixture of softer abrasive – to grind away the cookie dough and harder abrasive to help grind through the harder carbides. It would require less of the more costly harder abrasive. And it turns out the harder abrasive would have a secondary effect of grinding the softer abrasive too, releasing a denser slurry of soft abrasive PLUS the harder abrasive.

Now we have accomplished the effect of a denser abrasive content in the stone PLUS adding the CBN harder abrasive.

Ok so far this is theory. Let’s get practical. What grit of CBN should we use and how much and how should it be formulated? BTW this discussion also applies to diamonds too.

So we need to think of CBN not as just a strop ingredient but as an ingredient added to a stone slurry. So I would suggest from practical experience that for synthetic stones you MATCH the grit size of the CBN with the grit size of the stone. So here’s a helpful table. I go past 30k for a reason when talking about natural stones.

1 micron = 16k grit
1/2 micron = 32 or 30k grit
.25 micron = 64k grit
.125 micron = 128k
.1 micron = 160k
.050 micron = 320k
.025 micron = 640k

Going in the other direction:
2 microns = 8k grit
3 microns = 6k
4 microns = 4k
6 microns = 3k
8 microns = 2k
16 microns = 1k
30 microns = 500
45 microns = 320
60 microns = 250
80 microns = ~ 220
90 microns = 180
120 microns = 120

So if we have a 1k GlassStone, you would pair this with a 15 micron CBN spray. Yes you can vary a bit either way and the numbers are not overly precise here. A 4k stone would use a 4 micron spray and so forth.

From a practical standpoint, you really don’t have to stick to Glassstones for this. The Shapton Pro stone works quite nicely for this application. For this application of using the stones on abrasion resistant steels, the slight difference in grit density and softness between the GS and Pro series is almost irrelevant compared to the effects the CBN produces. Indeed the Nubatama stones work quite well as well, producing some very interesting results. So for instance a 1200 Nubatama Bamboo will still be a soft muddy stone but will’cut’ abrasion resistant steels more quickly. A 2k Nubatama Bamboo will still produce high contrast kasumi finishes. Actually the technique works quite well on any number of stones.

I highly recommend you try this technique. Now lets talk about natural stones.

The abrasives in naturals are more complex and, by and large, softer than synthetic abrasives. As you use a natural stone, the abrasive particles break down further, producing an ever finer particle and a finer and finer abrasive slurry.

Adding CBN to the slurry ENHANCES the breakdown rate, producing an even finer finish at a more rapid rate. It also produces a more dense slurry, acting as a liquid nagura, perhaps more accurately a liquid tomonagura. This is particularly nice with very hard polishing stones. Now with natural stones I do like to produce a natural stone finish so I don’t want the CBN effect to be predominant, so I PURPOSELY select a CBN particle size significantly smaller than the natural stone particles. So for a polishing stone like an Ozuku Asagi or Nakayama Asagi, I might select an eighth micron or tenth micron CBN. You can even go down as fine as 0.025 poly and still get a very good effect. For natural stones that have pores (for example various suita like some Hakka and Shinden Suita stones) this small particle size keeps the pores of the stone from getting a large particle ‘stuck’ in the stone. Another secondary effect is that steels that don’t play that well with naturals suddenly become candidates for natural stone use! Enter a new age of applications for NATURAL STONES! This gets very interesting.

This use of CBN on naturals extends to middle and low grit naturals where I tend to match grit sizes like I would with synthetics.

It even extends to other natural stones. Arkansas stones (use a 4 micron particle), Chinese 12k stone and even stones that are not abrasive by themselves which now yield natural stone finishes.

This is a broad overview of the topic. You can also use these hybrid slurries on strops, etc as a dry technique to produce very interesting results in a variety of applications.

Finally a word of caution. CBN and other abrasives come in various preparations. I have CBN in several formulations – deionized water, water based gel suspensions for coarser grits, water soluble emulsions, and pastes that are oil rather than water based. There are various other preparations on the market. DO NOT USE ANYTHING BUT WATER SOLUBLE FORMULATIONS ON WATERSTONES. You will ruin your waterstones. So, excluding my paste formulations, all of the other formulations are fine to use on your stones. I would not recommend CRO on your stones – a real messy idea.

This is but an introduction and I welcome questions both on the ideas I presented and expanding the topic even further.

Here’s one recent example of this technique being used:

http://www.knifeforums.com/forums/s…

Good luck on your abrasion resistant steels! This technique will be quite helpful to users struggling to put edges on their new blades using conventional stones alone.

[Phil Pasteur]

found a video of Ken’s ! Okay he is doing a razor so maybe try it on the 10k Chosera on one of your test razors

That video is not Ken’s… at least not Ken Schwartz… of whom I was speaking.
Though I bet the idea came from him.

Also he was “enhancing a JNAT… Japanese natural stone.. as he said, to bridge the gap between the synthetic 8K and the natural stone. The bevel finish result is definitely interesting.

[Josh]

Wow… I heard cliff stamp mention this but didn’t know how true it was… I will be following with interest!

[Leo Barr]

I have not been saying this is wrong or right merely proposing discussion .
I could open it further to say what about using it on ceramics ?
My apologies for the incorrect labelling of the vid.
The text above in my last post is cut and pasted from Ken on knife forums.
We are dealing with news steels more and more and with that evolves sharpening strategies and I reiterate I proposed it as a question on the forum for those if any who have either tried it or feel there isa viable reason to try it .
I recall Ben Dale saying that in his opinion we should only use diamond stones on ceramics since the steel is softer than diamonds they dislodge from there medium and get stuck in the steel rendering a diamond sharpener useless after fifty or sixty uses and yet DMT | Atoma | & WE use them to name but a few brands .
So sharpening evolves along with the materials been sharpened

[Josh]

this video is the one I was referring to… seems to have the same experience. note that around 11:20 he shows a stone that he tried an m4 blade and a 10v blade on. You can see where the stone did abrade the 10v but did not the m4.

[wickededge]

One thing about Ken’s perspective is that it’s entirely based on waterstones and their ability to abrade these harder, more abrasion resistant metals. I’ve sharpened a lot of REX 121, ZDP-189 and various Hitachi steels with little more effort than our regular fare of 3xxV series steels, D2, CPM154, ATS-34 etc… I was really surprised to discover how quickly the diamond plates plowed through the REX 121 and other steels. So with our diamond plates in the mix, the metal removal portion of sharpening isn’t an issue. The question then would seem to be whether adding the harder abrasives to the waterstones in the polishing phase would speed the process of scratch removal. I’d be inclined to start around 2k or so and use like size CBN or diamond particles to see if there was a noticeable benefit.

-Clay

[Phil Pasteur]

Leo,
Don’t mind me… just thinking out loud… though I guess my writing style can be direct.
After reading what Clay said, and Kens entire post, the concept does make some sense.
Ken, as usual, makes a very convincing argument for his case.

Until I know more, I would still hate to do this on my only set of Chosera stones.

The part about the synthetics removing metal around the hard carbides certainly might be a concern where those carbides are in high concentration. This could be true even during the polishing phase.

That being said, I have recently sharpened some K390 and S110V and over time a bunch of ZDP 189. Not Rex 121, but high vanadium content just the same. It takes longer to polish, but at the levels that I can test or see, there have been no problems at the edge in only using synthetic water stones for these..

[Author]

Posts