Fri Jul 19, 2013 3:52 pm
I'm fascinated by single beveled knives and particularly with sharpening them, even though I have absolutely no need for them nor do I ever get them to sharpen. I purchase them just to be comfortable with sharpening them, it's a learning experience. If I only sharpenened customers traditional Japanese Knives I would be open for business twice a year.
I had a chef pick up a Deba for me at a market in Vancouver, again for the purpose of sharpening it and looking cool because I have a Deba. I was disappointed in the knife, while it does indeed look cool to those uneducated in knives (my friends) it is also a cheap Deba. The spine is not thick like a true deba so it is the perfect knife for me, I can sharpen to my hearts delight and if it fell apart I am only out 30 dollars.
I decided to flatten the Blade Path (or Blade Road) for the purpose of seeing how long it would take and if I could do it by hand. I painted the blade road with a sharpie and tried sharpening it on a 1K stone, just to see how flat the blade road was. Either I have extremely good sharpies or the BR was brutally uneven because I hardly touched the sharpie.
It took 2.5 hours on the Atoma 140, 150 Bamboo and Shapton Glass 500 to get it to the point where just a couple of swipes would completely remove the sharpie marks. So I patted myself on the back and then went to work actually sharpening it.
I wasn't aiming at producing a Kasumi finish, I was going for a mirror finish, its a cheap mono steel blade, I was practicing and having fun.
I found it easy to sharpen, the burr that can came off of it was easily the most pronounced burr I have ever seen, a piece of wire actually fell off that I had to pick up off the stone. After that, things started getting exciting.
At the end of the day, when I put the knife back in the box ready to bring out to show my uneducated friends how cool I was because I had a fish cutting knife that I'll never use, I was astonished by the edge. This cheap little Deba was sharper than any 200 dollar Shun or MAC I have.
Kind of exciting really and I could not help but wonder if I actually did have a "real" Deba, what type of edge it would take and hold. I finished this one with a 6K Arishyama but to be honest, it was already sharper than most knives I have seen after the 1k Ume.
I also wonder now why one would actually flatten the Blade Road on a Yanagiba for example, if it is slightly convex and made purposely like that, is it not detrimental to flatten it all out? I think this is where the softer stones, the Nubatama and natural stones come into play, they fill those little hollow spots in the Blade Road and create a uniform pattern without disrupting the actual grind of the knife. However, after repeated sharpening the Blade Road would likely be fairly flat unless you rocked the blade a little to maintain the original grind.
Just rambling here folks.
A Usuba is next.
Fri Jul 19, 2013 4:08 pm
Most, if not all, traditional single bevel knives are ground on a large diameter wheel giving the blade road a concave grind. After which they are typically finish sharpened on a flat stone. This can, and does in some knives, flatten the entire blade road. To what extent depends on the knife, the maker, etc. If it's an inexpensive knife, in my experience at least, not all of the concavity is removed from the maker/factory. Therefore, when you do (if you do) flatten the blade road you end up with something like you started with. The more expensive knives are either completely flattened, or close to it or......they are given a hamaguri (convex) edge:
If you get one with a convex grind (hamaguri) and you flatten it, then yes, you're defeating the purpose the maker had for giving the knife that grind.
The benefits/cons of such convex edges is beyond my use and knowledge base though. I know enough, but only from listening/reading, that hamaguri is supposed to release food better I believe.
Fri Jul 19, 2013 5:35 pm
The above linked video shows the process that a single bevel knife goes through to reach a finished product. Of the about 10 different lines of traditional knives we carry including a custom @ $2300 none are concave or convex, most do have a microbevel though.
As for sharpening a single bevel knife, a microbevel or slight raise in angle when sharpening the hard core metal is needed so they don't fail in use. A deba knife is also sharpened with several different angles including a backside microbevel near the heel of the blade. As shown in this video http://www.youtube.com/watch?v=vg9b_fZDrN8
Fri Jul 19, 2013 6:02 pm
Some time ago, picked up a Doi yanagi and the first thing I did was put it on the stones. The blade road wasn't flat and definitely wasn't even. It wasn't a cheap knife so I was a little surprised, but since it was my first single bevel, I was up for the challenge of making the edge my own =)
I probably spent a good few hours on a 600 grit stone working out some of the high spots on the blade road, but some unevenness is still there. I figured I'd work it out over subsequent sharpenings.
I've tried a variety of soft stones in an attempt to get an even aesthetic finish on the blade road, but the low spots make it a virtually impossible to do with flat stones. I've resorted to doing the best I can with the flat stones, then finishing the blade road with some fingerstones.
Fri Jul 19, 2013 8:39 pm
I don't doubt that it took hours to flatten yours, even on an Atoma 140. I'm at the point of avoiding single-bevel knives whenever possible after dealing with big edge chips in a couple older single-bevel knives, as well as one that was mis-sharpened when the local sharpener apparently handed the business over to someone else. Amazing how fast a belt sander can ruin a great knife. Several days of arm exercise and fingertip abrasions, I mainly now know I can screw them up pretty quickly on the Atoma as well.
I've got the Kanishige 180 mm deba in white #3 and I also found that the blade road was slightly concave. I did touch it up, but I'm not making any attempts to intentionally flatten it. Working on the edge has definitely improved the sharpness, but a pretty road will just have to wait until it happens on its own.
Ken has told me that the magic of a single-bevel knife is that the sharp shinogi line allows what you are cutting to come cleanly off the knife's surface at that point. Round it and the magic goes away.
Sat Jul 20, 2013 1:41 am
Jason, thanks for the links, I had seen the first video several times, love that one. I hadn't seen the second one though, it's excellent. I can see the need for the backside microbevel near the heel as that is portion of the blade that is put to the test the most.
Really cool videos thanks for taking the time to find them and send the link.
Vinhster, I plan on doing the same with some finger stones that Ken sent me.
Thanks for the replies fellas.
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