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 Post subject: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 6:16 pm 

Joined: Mon Mar 17, 2014 5:56 pm
Posts: 16
So, I have had this device for about a year and like it a lot. My principal knives are a Kikiuchi clad 240 gyuto and a Misono UX10 270. I prefer the profile of the Kikiuchi but believe that the Misono, with it's thinner overall blade from spine to edge, can get sharper and stay sharp longer. But that is neither here nor there.

What I have been doing thus far is the same for both knives. I thin at 10 degrees with the diamond 140. Well, at any rate, I thin at the lowest (black dot) setting. Without the angle cube I suppose I cannot be really sure that is 10. After thinning (which I do rarely, twice a year at most), I sharpen at 15 degrees (red dot), equal bevel on both sides. I do this around once a month.

The boys at Korin insist that this is not ideal for the Misono. (They hold the Kikiuchi in contempt.) They say it should be "70/30", which of course refers not to degrees but to percentages of the total bevel. So, if I have this correctly, on a right-handed knife, the "left" side of the blade will have the “70” bevel, while the right side will have the 30. I used to try to achieve this freehand and did OK, but I notice far better results just doing 50/50—or 15/15—with the Edge Pro, so I stopped. But I am wondering if I am doing the right thing.

I have looked through this forum for the answer to this question and either not found it or found it and not understood it.

1) Should I just soldier on with 50/50-15/15? I can get the knives plenty sharp this way, but I am always interested in sharper. They still tended to “wedge” a little bit and split rather than cut through (say) a large carrot at the very bottom.

2) If there is a better way, how to achieve it? I’ve read some who say, different angels on each side, others who say, use the same angle, just grind the left side more. But how much more and how do you know?

3) One thread said it was the RIGHT side that took the steeper bevel—but either he was talking about a left-handed knife or else my understanding is all wrong. Again, for a right-handed person, the side with the steep or “70” bevel will be the LEFT side of the blade when the knife is held perpendicular to the board and the tip is facing forward, correct?

I am not hopelessly ignorant, but not all that conversant either, so any help will be appreciated.

Thanks.


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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 6:41 pm 
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Manton - normally an edge labeled with 70/30 asymmetry means that the right side of the blade (as you hold the knife on the board) has the 70 and the left side has the 30. If both sides are sharpened at the same angle, then the right side bevel will be about twice as large as the left side and the actual apex of the edge will be moved a bit to the left side of the blade versus right in the middle as in a perfect "V". It would be a total pain to sharpen each side at a different angle on the EP. I would just keep the same angle and then sharpen the right side a little more than the left. If you're currently doing 50/50 and want to try this, then start w/just a bit more on the right versus left for a 60/40, then next time you do a full sharpening, do a 70/30. If you experience any steering issues while cutting taller products with your new, more asymmetric edge, then go back to what worked for you w/no steering.

The theory is that a more asymmetric edge can exhibit more apparent sharpness, sometimes at the expense of edge robustness. Some asymmetric edges are used to match the grind geometry of the blade itself. This is sometimes the case if, for example, the left side of the blade is ground flatter and with less convexing than the right side. If I have this relationship wrong, someone please correct me :-).

My other thought is if you're experiencing wedging issues, you might need to thin at an angle lower than 10 degrees. I would try to go as low as possible on the EP. I've even used the bottom of the EP (I'm assuming Apex model here), where the rod goes into the plastic as my "drill stop collar" and use that to adjust for the stone thickness. You can get pretty low that way. I had to cut off one of the arms on the tightening nut to get that low on my particular EP Apex.

I don't hold Kikuichi's in contempt - they make some VERY nice knives, that are used by people here that really know their stuff ;-).


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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 7:01 pm 

Joined: Mon Mar 17, 2014 5:56 pm
Posts: 16
I am thinking of a Japanese traditional single-bevel knife. The left side is flat (actually slightly hollow), the right side has the angle. So, wouldn't it be the same way with a Western-style knife? Left side much steeper/flatter, right side angled?

Check this out from Korin:

http://korin.com/site/PDFs/knifesharpen ... RXaTlk0zVg

P. 3 shows the geomery of a single-bevel knife, presumably if it's right-handed, the eye is looking from the heel foward; that is, the perspective is that the heel is closest to the eye and the tip points away. Go to page 4, and you see a similar view of a 70/30 Western-style knife.


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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 7:10 pm 

Joined: Mon Mar 17, 2014 5:56 pm
Posts: 16
It's like they are trying to confuse me. This video seems to say the opposite:

http://www.youtube.com/watch?v=JCYI7lk3eKY

So, I am standing at my cutting board. I have the knife in my right hand. The blade is perpendicular to the board, edge pointing toward the floor, spine toward the ceiling. Tip is pointed forward, away from my body. I do not know which is "inner" or "outer," front or back. I know that when using a yanagi or deba or what have you, the flat side is always facing left. Hence, I conclude that an asymetric edge on a Western gyuto should be similar: flatter and steeper (larger) on the left, more angled and shorter on the right. Which is what the Korin diagram shows.

But the vid seems to say the opposite.


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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 7:19 pm 
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Manton - not necessarily the case on a double bevel knife, Western or Japanese. Some are ground 50/50 so each blade face has about the same amount of convexing, ie. a similar shape. Some are ground somewhat asymmetric as I indicated before. Whether the left or right side is ground flatter and where and how the convexing is ground varies from maker to maker and from knife to knife sometimes. This is quite different from a true single bevel knife which you are describing.

Good examples that are ground 50/50 on the blade sides that I can mention w/certainty are the Masakage Yuki, Shimo, and Koishi, and Richmond Artifex. I believe the Konosuke HD, HH lines are also 50/50 ground. I'm not talking about edge bevels here, though those are often ground 50/50 on these knives as well.

Melampus posts choil photos occasionally. Look for one of my choil shots here: masakage-yuki-210-gyuoto-larger-pics-t2122.html. This is a good example of a nice, 50/50 grind geometry.

To add - most single bevel knives are designed for right handers, with the primary bevel on the right side and hollow ground (Urasuki) on the left. Left-handed single bevel knives would be just the opposite, although they are much less common and are often special orders.


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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 7:21 pm 
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Joined: Mon May 27, 2013 6:39 pm
Posts: 258
You need to stop listening to what Korin says. This is the same place that uses coins to measure "angles" their tutorials are garbage imo.

You have something thats working for you now. You can stick with it and persue higher levels of edge refinement. Thin the knife more. Or try changing the grind.by keeping the angles the same and sharpening one side more than the other.

Doing asymetrical edges on the ep is no big deal. The amount that the apex will be off center is going to be minute at best. Fractions of a millimeter. Hardly enough to negatively affect the performance of a knife.



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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 7:28 pm 

Joined: Mon Mar 17, 2014 5:56 pm
Posts: 16
The only thing that worried me was reading here that the Misono is manufactured to asymetric and I thought, maybe I have screwed it up? It does cut well and get sharp. I mean, it won't simply fall through an onion without pressure. But it can cleanly cut a paper towel with little effort.

Overall I am happy I am just wondering if I could do better if my technique were better.

FWIW, I have the Choseras but I intend to get Shaptopns.


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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 8:04 pm 
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+1 on Sadden's comments. If you're happy with the Misono and it's not steering on you, then just work on technique/refinement to make that edge just a little bit better each time you sharpen it. How do you maintain between full on sharpening sessions?


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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 8:14 pm 

Joined: Mon Mar 17, 2014 5:56 pm
Posts: 16
I use the Mac ceramic steel on it a lot. I love that thing. Works very well.

I go back and forth between the two knives. Each has its virtues and problems. I wish the Misono were 240 rather than 270 and the profile is inferior. However, it seems to get sharper and stay sharp longer. Also the handle is better. And the blade is overall thinner so it wedges/splits food less.

The Kikiuchi has a perfect profile. It's a bit stiffer, which can be good for hard veg. But it's thicker, which causes more splitting. The handle is too small. I can't get it quite as sharp and it dulls faster.

BTW, I am not sure what you meant by getting it even thinner. I have the arm (Apex) at the very lowest level, I don't know how to make it go any lower. It's in contact with the base so there's nowhere to go.

I may get an angle cube because at this point I actually don't know what angle I'm sharpening at, beyond the dots on the Edge Pro rod.


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 Post subject: Re: 70/30 Sharpening with Edge Pro?
PostPosted: Mon Mar 17, 2014 8:22 pm 
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Joined: Tue Feb 05, 2013 6:00 pm
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Sounds like you're going as low as possible already on the EP for thinning. The Angle Cube is a nice device for determining accurate angles and also for repeating those angles on subsequent sharpening sessions.

What model is your Kikuichi?


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