Deba grind question

[Brock Cutlery]

At 17 seconds in this video you can see the back hollow grind on this Deba. How do they achieve this hollow grind at the tip without taking it through the top and edge?

[video=youtube;6u067nzvEYE]https://www.youtube.com/watch?v=6u067nzvEYE[/video]

 

[StuNY]

You either need a large wheel (36-48") or a radiused platen. I just finished my first Deba like this with my own radiused platen. You start by making a "groove" with the wheel down the middle of the back of the blade, stopping before the tip, then just keep working it out toward the top and bottom edge without breaking through freehand style. Takes a little practice but my first one came out acceptable to me... for now : )

 

[Brock Cutlery]

You either need a large wheel (36-48") or a radiused platen. I just finished my first Deba like this with my own radiused platen. You start by making a "groove" with the wheel down the middle of the back of the blade, stopping before the tip, then just keep working it out toward the top and bottom edge without breaking through freehand style. Takes a little practice but my first one came out acceptable to me... for now : )

That kind of precision just seems amazing to me at this stage in the game. Hats off to you if you can pull that off. One day...
I have the 36 radiused platen. Would that work for this Deba grind?

Do you have pictures of yours?

 

[John Katt]

You can use any size wheel you like for that grind 1" to 40" the trick is dont go so deep that you notch the blade, which will look like waves when staring down the sharp edge

 

[Brock Cutlery]

You can use any size wheel you like for that grind 1" to 40" the trick is dont go so deep that you notch the blade, which will look like waves when staring down the sharp edge

So theoretically I could use my 14 inch wheel and just float around inside the margins?

 

[John Katt]

I would make that grind by marking the flat edge with my depth gauge at .005 and then never going thinner at the edge, the bigger the wheel the higher you can take that grind without breaking through the back

 

[John Katt]

Think about it like this, if you ground a hunter and left the primary edge at .016 and then split the knife in half, you would have two knives like the one in the video with no change to the hunter profile

 

[Brock Cutlery]

Think about it like this, if you ground a hunter and left the primary edge at .016 and then split the knife in half, you would have two knives like the one in the video with no change to the hunter profile

I'm not sure that this pic helps me unless you are describing the single bevel?

But I do see on the back side grind in the video they stayed much further away from the tip than they did the top or bottom edge on the hollow grind.
I guess I can begin to see how that could be done on a wheel. Amazing the intricate work that goes on behind a good knife.

Until I started wanting to make knives, and started studying them I had no idea what delineated a quality knife from a cheap one, except for the general appearance of quality or lack thereof. My eye is undergoing some serious training now and I see things I never would have noticed prior.
It's pretty cool!

 

[John Katt]

I'm not sure that this pic helps me unless you are describing the single bevel?

yes, if you split any hollow ground knife in half you will have 2 single bevel knives with no change to the original profile

 

[Brock Cutlery]

yes, if you split any hollow ground knife in half you will have 2 single bevel knives with no change to the original profile

Cool John. I get what you are saying. This Deba has a single bevel on the "front" and a very shallow hollow grind on the "Back"
But that back hollow grind doesn't go all the way to any edge. It's just to hollow out the middle area of the blade.
It's that shallow hollow grind on the back that has be baffled and a bit amazed.
It is sharpened on the back by laying the knife blade flat on the back on the stone and gently removing very little material.

 

[John Katt]

Cool John. I get what you are saying. This Deba has a single bevel on the "front" and a very shallow hollow grind on the "Back"

I've looked at theses knives briefly in the past and assumed the back is completely flat and the front has either a chisel grind or a hollow grind, so after reading every thing I could find on them after joining this discussion I have found that to be true

Here is a video of how to sharpen one, the only thing done to the back/flat side is to remove the burr https://www.youtube.com/watch?v=Qp458vSIdWU

 

[JMJones]

That kind of precision just seems amazing to me at this stage in the game. Hats off to you if you can pull that off. One day...
I have the 36 radiused platen. Would that work for this Deba grind?

Do you have pictures of yours?

While that method may work it is far more difficult than actually needed. The entire back can be ground hollow from edge to edge with a large wheel or a radius platen. Then the back is laid flat on a stone or regular platten and ground until just the top bottom and tip are all on the same plane. Due to the nature of the hollow ground the middle will be deeper than the edges so this method is simple easier and repeatable.

 

[Stacy E. Apelt - Bladesmith]

As to making the urasuki ( hollow grind back) use whatever method works for you. I have previously posted several ways to do it with a standard 8-10" wheel.
One of Nathan's curved platens makes it a pretty simple task nowadays.

There is a trick to getting the look that the OP was asking about.......Make it completely hollow, then make the perimeter flat area.

First, do the hollow grind until all the back of the blade is hollowed. Once there are no flats on it, clean up this hollow grind to 400 grit or more. When that is done, place the back on a surface plate with a sheet of 220 grit paper taped down. Work the blade in figure eight strokes until you get a flat edge that goes all the way around. I usually make one about 1/4" wide. Water stones, or the flat platen work too, with some skill and practice.