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Here are a few pics. The first is from the ZKnives blog. The closest to the Fujiwara is going to be the 4th one from the left.



Here's a smaller picture, but it's more like the actual geometry of the knife you're talking about.

Please excuse my crappy Paint job.



Ration can be confusing; it has nothing really to do with angles but rather how much of the cutting edge is on each side of the centerline of a line that bisects the knife vertically.. In my crummy pic there's a red line dividing the blade into two halves, left and right. 70/30 just means that 70% of the bevel is on one side of the line and 30% is on the other. The little yellow mark is meant to show the angle of each side. Now note that depending on the other dimensions of the blade, each side could have the same angle, or each a different one. But angle isn't really related to ratio. I hope I'm stating this clearly. You can change either angle a bit but maintain the ratio so long as you adjust the thickness of the blade.

 

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Let me try to expand and clarify a bit:

Originally Posted by butzy

I'm about to buy a carbon steel knife with a double bevel 70/30.

I've also seen a couple of drawings (posted by BDL amongst others) of a double bevel and I wonder if these are actually the same things.

Double bevel knives are the kind you typically see. It means both sides of the blade are sharpened. Single bevels have only one side sharpened. The simplest example I can give you is a wood chisel. In fact, single bevels are often called Chisel Grinds. The 70/30 part is telling you the ratio of the left bevel to the right (or vice versa).

I'm not sure if I am describing this right, but the double bevel according to the pictures looks like the knife has 2 even angles.

The 70/30 double bevel sounds more like the edge of the knife is asymetrically sharpened (like the cutting part of the knife is slightly off-set to one side.

Sorry if this sounds clumsy, I'm lacking the vocabulary to describe it properly...

You're pretty close. They are ground unevenly, with more on one side than the other.

With the 70/30 bevel, what are the angles to sharpen at for a Japanese carbon knife (the Fujiwara KFH)

15 degree on one side and 10 on the other side or so?

Maybe. They could be 10 and 15. Or 15 and 15. Or 5 and 25. The actual angles aren't really relevant, just the ratio of one to the other. In practical terms they'll be somewhat related as is dictated by geometry.

Or am I totally wrong here?

Nope, you have the gist of it. /img/vbsmilies/smilies/smile.gif
 

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Nice pics!  Better detail than anything I could find.
 

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A cardboard angle gauge can really help- use it if you like it. Sometimes I use a special device (aka "The Gizmo") like a Pana-Vise to hold the stone at an angle so I can simply sharpen horizontally. Some people cut a block of wood for this; for example, you can make a wedge with a 15 degree angle and that's about ideal for many kitchen knives. I also use an Edge Pro Professional model with a ton of custom stones. And sometimes I find it enjoyable to sharpen freehand on stones, especially if I just have one or two to do and don't want to drag out all the stuff. Plus I have some nice stones that aren't available for the EP. Everyone has different methods but I really like soft stones because you can really feel the difference when a knife is digging in (too steep), skating over the top (too shallow) or biting right on the edge. Soft stones refine your technique IMO.

You make one excellent point, Butzy- sometimes there is no real bevel to follow. If a knife's edge is very worn you'll often just have to pick and arbitrary angle and have at it. I do this all the time.

Lastly, don't get discouraged if it takes awhile to learn. In my case using many different techniques and tools really helped as they all reinforced each other. Years of freehand sharpening really helped my technique on the Edge Pro, and being able to watch a burr being created stroke by stroke on the EP helped me achieve a higher level of understanding of the actual process of sharpening. And both were helpful in making the leap to powered gear like my belt sander. One nice thing is that nowadays there's a lot of good info out there; you might want to check out Dave Martell's videos on YouTube. Mark Richmond has several sharpening videos geared for novice sharpeners on his site, ChefKnivesToGo.
 
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