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Removing chips from a single bevel knife

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cotedupy

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Is there a preferred method for this? They are very small (probably actually not chips and actually caused by slight rust pitting). I assume I can just sharpen them out in the manner I'd normally sharpen a single-bevel knife? Or is it better to focus more on one side than the other...? TY!
 

mise_en_place

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Do not mess with the ura (backside of a traditional Japanese single-bevel). There are many people vastly more qualified to help you with this question, but be careful to not abrade too much material off of the back.

Following the geometry of the blade-road on the front of the knife shouldn't cause any trouble.
 

M1k3

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Remove metal from the edge and the spine in equal amounts. Keeping the ura centered.
 

Luftmensch

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There are many people vastly more qualified to help you with this question
👆

😬 So not me... There are quite a few good videos out there.

I assume I can just sharpen them out in the manner I'd normally sharpen a single-bevel knife?
Major pitting can be a major PITA. Since your chips are small... you should be able to proceed as normal.
 

Luftmensch

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Hmmm....

So... Looking at the knife. I would describe that as major pitting! Hard to say without more detail. Even with that much damage, it can be fun to restore them and a good way to practice.

I doubt you had intentions to restore the knife to 'like-new' condition? But forgive me if I am stating the obvious, without a water wheel, it will be very very labour intensive to completely restore that ura. Not impossible... but you would have to grind down the very hard steel on the ura manually. It is effectively like working on a honyaki without the benefit of either power tools or bench stones. To operate on the concave (urasuki), think finger stones but instead of a polish, you are actually trying to remove material. Punishing work!

The best bet would be to go with a restoration that respects the yanagiba's past ;) Make an assessment on how much material you need to take off the primary bevel to get it looking clean... or go with a slightly more rustic look.

Major pitting can be a major PITA.
The reason I said this is not only related to the above (hard work). The more subtle reason is the way it potentially affects cutting. The uraoshi, the flat boarder around the urasuki, can be any size. It tends to get thicker with heavy use. With good maintenance and a well ground blade, the goal is a nice and even, thin uraoshi. At the edge, the cross-section of steel is only fractions of a millimetre thick. Pitting, as you have discovered, even when shallow, can break through the material and present itself as chips on the edge.

I reckon you have several options:
  • Complete resto (madman)
  • Complete resto of the front, cleaned up but rustic back
  • Cleaned up but rustic front and back
I would recommend starting with the last option and deciding if you want to progress to the second option. For instance will the knife look weird with a pristine front and a rustic back?

See how deep the pitting is, but you might find yourself in a situation where it is really difficult to remove the pitting on the uraoshi completely. Start by removing the pitting on the primary bevel. Only aim for removing it at the cutting edge at this stage (not further up the blade road). But be mindful of following the blade geometry. Raising the angle at the cutting edge further ruins the knife! Removing pitting on the blade-road/primary bevel will cause the uraoshi at the cutting edge to become thinner. If you think about a right-angle triangle, you are lowing the hypotenuse (primary bevel), this means the sides (uraoshi) become narrower. To even out the aesthetics, you can make the uraoshi at the edge fatter again so it matches the uraoshi at the spine. Do this by applying more pressure on the cutting edge when working on the back. Once you have done this, see where you are at. You may have a completely clean cutting edge (hopefully). You may find when the uraoshi is a nice even boarder, there is still pitting on the cutting edge (only from the back side) causing chips.

At this point you can choose to live with it... or you can see if you can remove the pitting by removing it from the back. Again, apply more pressure at the cutting edge when honing the back. Now the reverse will happen. The uraoshi at the edge will become fatter than the uraoshi at the spine. Again, see where you are at. Now you can even out the uraoshi at the edge by bringing down the primary bevel again.

Perhaps try a few cycles of front-back-front....etc. See where you are at. Hopefully can get to a situation where you are exposing fresh steel at the cutting edge and are moving the pitting on the uraoshi away from the cutting edge and towards the urasuki. If you are lucky you will be able to do this without significantly growing the uraoshi at the spine (a portion of which may be the softer cladding material).

Suppose you get a nice clean edge. Then evaluate how much you want to remove on the face of the blade. Will restoring this completely look odd with the state of the back??? You decide :)

Thats how I would approach the problem anyway... See how you go!
 
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cotedupy

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Thank you very much for this @Luftmensch !

I'd be inclined to agree with pretty much everything there. Perhaps the photos make the pitting look a little worse than it is, but there are certainly bits on both sides that are effectively going to be impossible to get out. Once I've got a good edge (fingers crossed), I'm going to give it one more round of sanding and a sharpen and leave like that. As you say - I could always come back to it later.

I've done a bit more just now and was actually working exactly as you said - on the bevel mostly, lightly evening the uraoshi, seeing what it was like and then starting again. It's slow and delicate work, but I am getting somewhere I think.

Also as I think I said in the other post - the bevel doesn't really exist as such any more, it's pretty rounded out, the ura side seems to have had less work done on it previously. I'm trying to sharpen along with where it would have been, but it's not desperately even, so we'll see how it ends up... I'll be more than happy if it turns out just to be a decent general slicing knife!

Thank you again for the insights, as you can tell it's not something I've ever done before on a single-bevel knife, so much appreciated.

[Edit - And I certainly seem to be getting somewhere now given how cleanly it's just sliced into the top of my finger 😬 ]
 
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