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 Post subject: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Tue May 28, 2013 8:33 am 
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This is the first of a series of videos where I start with a Customer's Moritaka Gyuto that had been very coarsely sharpened, probably with an Atoma 140 or DMT XXC or something perhaps coarser and is pretty scratched up.

In this first video I introduce the possible lineup of stones that I might use. I start with a Nubatama Ume 180 grit stone to reduce the initial scratch pattern in the next video.

Here's the introductory video.



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 Post subject: Re: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Tue May 28, 2013 8:41 am 
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... and the first video where I use the Nubatama Ume 180 grit stone for initial surface preparation prior to using the Kyushu Ohmura. The entire sequence past the 180 Nubatama is all natural stones. Note how even the 180 offers some initial contrast as opposed to other waterstones like Shaptons and Choceras. Also note how the muddiness of the stone is to advantage helping to increase abrasion rate and make for a more uniform surface preparation for the natural stones to follow.



I'll post more later (tomorrow) so you can look these over and post some questions first.

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 Post subject: Re: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Wed May 29, 2013 4:13 pm 
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So the first natural in the sequence is an Ohmura. Not a synthetic one but the real deal. It isn't as coarse as the synthetic 150 grit 'Ohmura'. In fact borrowing the name Ohmura on a synthetic stone really does little more than confuse what most people think of the real deal. That I precede using this stone with a 180 Nubatama gives you a better perspective of it's level of abrasion. And how to more ideally use this stone rather than a synthetic 150 grit stone using it's 'name' to do a clearly different task.

One of the most interesting aspects of using this stone is the level of contrast it provides.

Another particularly interesting characteristic is the continuing level of refinement you get 'working the mud'. While I was considering using the Amakusa stone shown in the initial video of this sequence, this continued refinement made this completely unnecessary. This is one of my favorite characteristics of natural stones - that you can use a single stone to start at one grit and end up with a much more refined grit at the end of the session. So while the initial grit might be in the range of just a bit over 200, the final grit acts much more like a 1k or finer finish. This is one of the reasons why the almost always asked question 'What grit is the stone?' really doesn't have a precise answer. Two people working the same stone will get two different results because of a difference in technique. And on different steels - like the core steel and the cladding - or the steel from two different knives - you get two different scratch patterns. It is nature's sense of art that you are taking advantage of in a natural stone :) Rather than fighting nature, you work in harmony with it on it's terms through your understanding of it's ways as you use the stone.


I was actually quite pleasantly surprised by this. I was further surprised by building up a bit of slurry with an Atoma 140 on the stone. You will see the mud on the stone in a second video session appended to the initial session. It does give the illusion that the mud SUDDENLY appears. It is interesting to see the color of this thicker mud, caused by the interaction of the Aogami Super carbon steel and the Ohmura mud. Now the conversion of the initial scratch pattern from a diamond scratch pattern to a synthetic stone pattern to a natural stone pattern is complete.

Next we move on from the Arato or coarse stone range, skipping the slightly finer Arato, an Amakusa, to a beautiful mid grit stone, the Tajima, to begin the process of refining the edge, both further bringing out the beauty of the knife AND to further refine the edge's cutting capability. This isn't because the Amakusa is a bad stone, just not the right one at this time in the sequence. This second aspect is often ignored on other natural stone videos on the net which just try to impress you with the overall finish of the blade. To me this is misleading as you don't have an understanding of what preceded the stone you are observing being used. The current stone could have no effect and you wouldn't know it. Or worse yet you could see a poor finish and attribute it to the stone, ignoring the fact that the stone preceding it had not been used to do it's job. A sense of the entire sequence used is quite relevant.




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 Post subject: Re: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Thu May 30, 2013 4:32 am 
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Location: San Ramon Ca.
Really good videos Ken! I enjoy them all!



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 Post subject: Re: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Thu May 30, 2013 5:56 am 
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Thank you, Pete! BTW, I live in Mountain House - near Tracy. You should see some of these stones in person and play with a few of them :)

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 Post subject: Re: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Thu May 30, 2013 6:37 am 
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Next in the sequence is the Tajima stone (Toishi). This is a mid grit stone or Nakado stone. Included in this group are stones like the Igarashi and Binsui and a couple even less well known. This is a relatively unknown stone, but as you will see, a real nice stone. Mark has some smaller ones on his site which I could cut to mount on an EP. This one in the video is a full sized one. I will use one of the small sized Tajima as a tomonagura. Note that EP sized stones work quite nicely as tomonagura for larger bench sized stones.

The one I am using is encased in this heavy burgundy wrapping as it was damaged in shipment and I used this to put it back together well enough for me to use but not to sell. It is additionally mounted to a glass plate for support. I show one with no bracing around it briefly. I have one of these at this time with a couple more on the way.

It really is a very nice pleasurable stone to work with. Not too hard - or soft. Just right. The mud generated from the tomonagura quickly darkens, indicating a rapid level of abrasion for a mid grit stone, yet it also provides a fine level of finish and excellent contrast. One of my favorite mid grit stones.

From here we will advance to the Meara, a polishing or awasedo level of finish. I'll talk more about this stone in the next video.

Here is the Tajima video:



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 Post subject: Re: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Thu May 30, 2013 8:31 pm 
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Now for the Meara stone. If you do a Google search, you won't find mention of it - or at least I can't, other than some mentions of a review of it on the CKTG forum.

It is a polishing stone or awesedo as opposed to a nakado or mid-grit stone. The 'ara' part of Meara, pronounced MEH' ar a, refers to the term 'coarse' like arato refers to coarse stones, or the coarsest of the Nubatama stones is the ARAte, meaning coarse cloth.

This stone is really not that coarse - even for a polishing stone, so the name really underrates the stone's capabilities. It is probably one of the more versatile stones I've used. In particular it seems to work quite nicely on a WIDE variety of steel types - certainly carbon steels like white and blue steels, but, oddly enough, on these high vanadium content Vanadium steels like the CPM type steels and other powdered metal steels like M390. In fact I haven't yet run into one it didn't like. I'm sure I will but it hasn't happened yet.

It's not a muddy stone like an aoto, but it does generate mud, much like other polishing stones. A fairly hard stone. It fits nicely here in this sequence with a significant overlap with the next finer stone in this series I'm using on the Moritaka knife, the Yaginoshima Asagi. These two work well together. As an aside, I might mention that you just don't see the amount of burr formation with most naturals, probably because of how the mud is used on naturals vs synthetics. The edge it produces has a most interesting combination of toothiness and refinement, making it more than suitable for many tasks in a kitchen. Additionally because of it's hardness, it will work well on straight razors to prepare an edge for a final polish. I have mine out on my bench and use it quite a bit.

It has a somewhat different shape than many stones, a bit shorter but a good bit wider. I find it very comfortable to sharpen on and really like this size.

I do have a few available so contact me at ksskss at earthlink.net if you are interested in one. It is a heavy stone and one that will last you for a very long time because of it's slow wear rate.

I plan on making this stone available for the EP too.




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 Post subject: Re: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Fri May 31, 2013 3:39 am 
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The next stone I use in this sequence is the Yaginoshima asagi, easily one of my most popular polishing stones - and for good reason. Not as hard as the Ozuku, Nakayama or some other mines' asagis, it is just right in hardness for knife edges, yet still hard enough and slow wearing enough to use for straight razor honing. Given the proper preparation with preceding stones not to leave large scratches, this stone produces a very nice kasumi finish. It is an easier stone to use to accomplish this task than stones harder than this.

While the Yaginoshima Asagi can certainly be used without a tomonagura, it certainly can be used with one as well. In this video I demonstrate the use of the tomonagura, making a pure Yaginoshima Asagi stone slurry before beginning to sharpen the knife. This allows one to start with a finer slurry and a 'cushion' of slurry between the blade and the stone. Thus we are starting at a finer finish than we would on the stone alone. I do this because the preceding stone, the Meara has already elevated the level of refinement past just the lowest level of refinement the Yaginoshima Asagi is capable of producing. [Hope this makes sense. If not please ask.] Please note that the use of a tomonagura or stone of the same composition as the main stone produces a mud finer than the sort of mud generated by the use of a diamond plate. Earlier I specifically used an Atoma 140 for generating mud on the Kyushu Ohmura because I WANTED a coarse mud. Here I wanted to begin with a fine mud withuniformly ground stone particles of a single type. This is not to say that you can't cautiously try muds from a different slurry stone. So for instance I have used a Yaginoshima nagura stone on a Meara with good results too and other combinations. Perhaps this is a topic to go into in some depth for another discussion.

Now when we begin to sharpen / polish the knife, the slurry density is high so the abrasion rate for the stone is high as well and the slurry goes from a white cloud color to a 'stormy' cloud color fairly quickly. The final result with this stone is quite pleasing aesthetically and functionally.

The final level of refinement is quite nice from the Yaginoshima Asagi, but for this video sequence, I'm going to go a bit more refined, using a Shinden suita, sometimes referred to as the 'Queen' of suitas. These have unfortunately become quite rare. I have a few, but seriously doubt that I will be seeing many more of these in the future. Sigh :(

Here's the video of the Moritaka being further refined using the Yaginoshima Asagi:



I also have a limited supply of these for the EdgePro.

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 Post subject: Re: Moritaka Gyuto Japanese Natural Stone Sharpening
PostPosted: Fri May 31, 2013 7:38 am 
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The final natural stone used in this video sequence - and the final edge that the customer will receive is produced using a Shinden Suita. This beautiful stone is a layered stone as is common to see in suita vs tomae stones. It has a construction much like a piece of puff pastry. The color of the stone is prized as it makes it easier to see the fine metal swarf produced in this final step of refining an edge.

This stone is quite hard. It is also not very porous at all. A drop of water will sit on the stone's surface for some time and very little water is required to add to the slurry during the course of sharpening to replace water absorbed into the stone. Mostly water loss is evaporative. It would be appropriate to use a tomonagura with this stone, however in this session I simply use patience and elbo grease to generate the slurry.

IMO this stone would also be an excellent razor stone. It is often stated that suita (which often have 'su' or pores) are not suitable for this use, however if not used with coarser nagura stones but rather with either finer tomonagura or similar stones - or even extremely fine diamond or cbn so fine it doesn't lodge in the su, or simply with nothing at all, these work quite nicely for honing razors. Or for final refinement of knife edges. These stones are also quite popular for fine woodworking tools.

In this instance the final edge produced was nice enough to where I felt no further refinement was needed.




I hope this sequence of videos has been of use in helping to begin to understand the pleasure of using natural stones and to see an example of their capabilities when used in a full (near) all natural sequence of Japanese waterstones.


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