Fixing a “wavy” edge

[cjallen]

I am looking for advice on how to fix the edge on this Hinoura. There are multiple spots where the edge makes contact with the board, resulting in no real flat spot. I made the first cuts with the knife, going through carrot and onion, and it was not really noticeable but I will need to touch up the edge so I would try to fix this issue as well.

Current stones: Diamond plate 140; Arato-kun 220; Shapton ceramic 320, 1000, 5000; Naniwa pro 600, 3000

My thoughts are grinding down areas 3 and 1. I think that would give me a nice flat spot between 2 and 3 that seems consistent with other knives I have. I like the height of the heel but feel like it dips quite a bit - I don’t think it would lose too much. Area 1 is the start of the curve so by evening that out could exect the curve to start back towards area 2? Just thinking out loud but curious to hear others’ thoughts.

Thanks.

 

[Mr Kooby Shemayrew]

For me….

I would start with re-profiling the edge on a piece of concrete, large brick, or cinder block. 90 deg straight up and down. Back and forth until the profile is fixed. Then I would do the same but with 45 deg angles of both sides to start recutting the bevel. Check the profile again. Sometimes you need to go back to 90 deg again.

Once the profile is fixed and a 45 deg starter bevel is cut then you can work on thinning and recutting the proper bevel with a coarse whetstone. Prior to this point there is no reason to use up a good whetstone when a $1 brick will work.

 

[Lurkernomore]

That can be fixed at 220 grit and 45 degrees without much trouble. It will take ten minutes I’d say. The subsequent thinning is gonna be more work but I’d start at 220 again. Depending on how thin it is right now you may even get away without thinning and can just use the thicker secondary bevel as is for a while before putting a full honbazuke on the thing.

 

[cjallen]

For me….

I would start with re-profiling the edge on a piece of concrete, large brick, or cinder block. 90 deg straight up and down. Back and forth until the profile is fixed. Then I would do the same but with 45 deg angles of both sides to start recutting the bevel. Check the profile again. Sometimes you need to go back to 90 deg again.

Once the profile is fixed and a 45 deg starter bevel is cut then you can work on thinning and recutting the proper bevel with a coarse whetstone. Prior to this point there is no reason to use up a good whetstone when a $1 brick will work.

Do you run the whole profile along the brick or just the problem area?

 

[cjallen]

That can be fixed at 220 grit and 45 degrees without much trouble. It will take ten minutes I’d say. The subsequent thinning is gonna be more work but I’d start at 220 again. Depending on how thin it is right now you may even get away without thinning and can just use the thicker secondary bevel as is for a while before putting a full honbazuke on the thing.

Here is a choil shot. I am unfamiliar with honbazuke so I’ll have to look it up.

 

[cotedupy]

Do you run the whole profile along the brick or just the problem area?

I'd be tempted to focus just on the sections between '1' and '3', ignoring the small bit at the very heel. You could do it all the way to the heel if you wanted, but in practical usage terms there's not much point. You definitely don't need to touch the part of the blade where it begins to turn upwards toward the tip (i.e. to the left of '1' in your pic).

FWIW - I would approach this in pretty much the same way as @Mr Kooby Shemayrew. Re-profile that section by 'breadknifing' it on the diamond plate, with the blade at 90 degs (perpendicular). You can skip the 45 deg stage if you want and move straight to thinning, but if you haven't done this kind of thing before then the 45 degree part might be helpful, and it's not going to add much on in terms of how long the whole thing takes. Do the thinning on the 220.

(You don't have to do it by breadknifing initially though, what @Lurkernomore said would work too. But breadknifing on a 140 diamond plate is going to remove the metal more quickly than 45 degs on a 220 whetstone, not just because of the abrasive, but also because you can apply more pressure. Breadknifing is also very good for getting the profile exactly how you want it to be initially, and then you do the thinning to match it, and apex. It's quite a precise method, and easy to execute).

 

[Mr Kooby Shemayrew]

Do you run the whole profile along the brick or just the problem area?

If you want to change the whole profile, you can. I would just stick to the problem area myself.

Be aware that flat, back and forth pulls will tend to flatten any belly or curve. Personally I prefer flat belly knives so for me this is easy. If you prefer a curved belly then it is best to rock the knife a bit when making these strokes.

 

[Corradobrit1]

, ignoring the small bit at the very heel.

Sage advice. I prefer a little lift in the region to prevent the corner digging into or bouncing off the board.

 

[cjallen]

If you want to change the whole profile, you can. I would just stick to the problem area myself.

Be aware that flat, back and forth pulls will tend to flatten any belly or curve. Personally I prefer flat belly knives so for me this is easy. If you prefer a curved belly then it is best to rock the knife a bit when making these strokes.

Thanks, this example has a pretty generous flat space compared to another Hinoura I have. Sanjo profiles are usually pretty flat, right? Might be nice to have two options to play with.

This version

Nashiji Version. I've used this a few times and have really enjoyed it. I might try to get here eventually with the new one.

 

[Mr Kooby Shemayrew]

Thanks, this example has a pretty generous flat space compared to another Hinoura I have. Sanjo profiles are usually pretty flat, right? Might be nice to have two options to play with.

This versionView attachment 281936

Nashiji Version. I've used this a few times and have really enjoyed it. I might try to get here eventually with the new one.
View attachment 281937

Everyone is different. I like very long flat belly knives. My custom knife is a cross between a nakiri and a gyuto. Basically a long nakiri with a k-tip and just a light rounding of the cutting edge by the tip for rock chopping.
A high-level Pro chef that I sharpen knives for only likes curved bellies, and he is astronomically above my kitchen-cooking skills.

 

[cjallen]

Thank you all for your input. I spent some time running the edge along my Diamond 140 to re-profile the the edge and I think it is at a good place for now. It still has a nice flat spot but now can rock in a smooth motion. I also took @Corradobrit1 suggestion and lifted the heel a bit. Now onto thinning and sharpening.

Before

After

New choil

When thinning, should I focus on the left side seen here to even out the geometry a bit?

 

[deltaplex]

I wouldn't attempt to even it out. It's an asymmetric grind, biased for RH users, and it's meant to be:

I'd continue to follow the existing geometry unless there's noticeable steering in taller, denser, product. If it is steering, I'd start with adjusting the edge bevels angles to attempt to compensate for it, before I started adjusting the primary bevel geometry.

 

[cjallen]

I wouldn't attempt to even it out. It's an asymmetric grind, biased for RH users, and it's meant to be:
View attachment 282348
I'd continue to follow the existing geometry unless there's noticeable steering in taller, denser, product. If it is steering, I'd start with adjusting the edge bevels angles to attempt to compensate for it, before I started adjusting the primary bevel geometry.

Thanks for the explanation. I thought that the way the geometry is now it would have been LH bias, guess I got it mixed up. I'm right handed anyway so that is some relief. I haven't had to thin a knife before so I'll have to search around beforehand for some resources.

 

[mengwong]

Experience report: this 150mm kaku bocho from Nakamura Hamono arrived a few days ago with a similar wavy edge. Yay, we get to do honbazuke!
https://knifejapan.com/nakamura-hamono-kaku-bocho-150mm/

After less than 5 minutes with SG220 zero grind then "up a bit" for deburring at about 20dps, reprofiled

Thinned and resurfaced slightly with SG500, edge refined with SG1000 at 10–15dps and done! Obviously there’s room for improvement but we’ll deal with that at the next sharpening.

I decided to round the front corner for rock-chopping and I have to say it was amazing how fast the steel melted away on the 220.

 

[nutmeg]

Thank you all for your input. I spent some time running the edge along my Diamond 140 to re-profile the the edge and I think it is at a good place for now. It still has a nice flat spot but now can rock in a smooth motion. I also took @Corradobrit1 suggestion and lifted the heel a bit. Now onto thinning and sharpening.

Before
View attachment 282338

AfterView attachment 282339

New choil
View attachment 282340

When thinning, should I focus on the left side seen here to even out the geometry a bit?

it seems like you got better results indeed!

Generally, sculpting a kind of micro bevel will slowly do the trick, keeping in mind how the blade should look like. A perfect geometry may give you some goosebumps.