Sat Mar 02, 2013 12:06 am
So yes the fronbt bevel is initially ground on a large wheel and concave. You can reduce this concavity by continuing to grind the 'blade road - not perpendicular to the stone but at an angle hitting only the two high ends of the concavity reducing the depth of the concavity - ultimately to a flat surface. In practice cheaper knives are more random and better ones make this front bevel flat - somewhat.
Now you can make the edge of the knife convex - whether or not the overall blade road is concave or not - or leave it a flat grind. So for instance on a kamasori or Japanese razor both the front and back are concave but the two edge of the edge portions are flat ground, meeting in a v grind.
So this brings up the interesting topic of mud.
If you have a very hard stone - like the Shapton Pro or GlassStones and the front bevel isn't dead flat, you get exactly what you are describing - missed spots irregular finish.
If you have a soft muddy stone, the mud 'fills in' these irregularities and you get an even finish. The Nubatama 1200 stone is precisely designed to accomplish this. For Natural stones, using softer Aoto stones - for example Monzen aoto or even soft Kouzaki Aoto accomplishes this quite nicely. A binsui won't work so well. A Tajima works beautifully! For polishing stones a hard stone like an Ozuku Asagi will work very poorly and you need a softer high grit stone like a Hakka Tomae. The Hakka Tomae is highly prized for this application. Another example of a high grit stone of moderate softness is the 15k Bamboo. Of course if you are going to the trouble to get a cosmetically nice finish, you may as well go for an appropriately high contrast kasumi type finish too using natural stones or Nubatama stones for single bevel knives.
Mon Mar 04, 2013 11:17 am
As always, very informative answer and I think I have the picture now.....all coming together.
Even though I don't get a lot of these to sharpen, I do need the right stone to achieve that even finish. Even if I get one.....it has to be right.
The Nubatama 1200 would be my choice and this leads me to the next question:
Let's assume that in my line of stones I had a 1200 Nubatama (the Blade Road Beautifier) but I want a 6K edge, I could do the Blade Road and edge with my current line up of stones, finish on the 6k Arashiyama but then go back over the Blade Road with the Nubatama 1200 to get that uniform finish it is capable of.
Mon Mar 04, 2013 2:35 pm
....or get some natural stones.
Mon Mar 04, 2013 2:47 pm
This is the beauty of the knife sharpening journey, I know that someday I will get some natural stones and this is something I look forward to daily. It may be 2 years away but it will happen.
I have never even seen one to be honest, I will be like a little kid Christmas morning when I get one.
(gees I was like the other day just picking up some Bar Keepers Friend)
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