Tried two methods to match the tip of my Usuba's base with the tip, how do you think?

[ag36]

As many of you maybe already aware, square knives tip wore much quicker than the rest of the knive since they are tapered to balance the weight.

There's two methods that I know, one is to thin the base to make the edge closer to the Ura, another one is to slant the entire Shinogi towards the tip.

I used my honyaki white 3 Usuba daily at home(I am not a chef) for a few years and the entire edge has slanted to the tip due to wear.

Finally I decided to raise the Shinogi to compensate this and move the edge slightly to the left,
which means I have to thin the entire cutting edge to repivot at the tip without making the base too thin.



The upper radius of the base is not fully blended in yet because I didn't want to touch my newly sharpened edge this time(I finished it with Asagi after Iyo, shaves paper without cutting it through).

How to you think about the result?

I wasn't able to move the entire Shinogi in one go because how much hardened steel I have to to remove by hand with 240 grit ceramic as PVD diamod like atoma will leave deep marks.

Do you think it's practical to do this without power tools? How would you have handled this?

Also I did this myself because I have diffucluty trusting shops in the London to take care of my knive because all they do is overpriced damascus and overpriced fancy grips.

Am I being overly cautious on this matter?

 

[refcast]

If it were me, I just try to keep the shinogi consistent and even. If I wear down the knife near the tip, that means I need to use the heel more, or that would be the profile shape I use the most. So I would just raise the shinogi slightly near the tip. A super flat usuba is mainly a katsuramuki tool anyhow. Plus -- the knife will still wear down with sharpening. It's kinda like soles of shoes
They wear down with how they are used. Usuba are the most prone to wavy shinogi, and the hardest to wide bevel sharpen evenly . . Hopefully the blade face is ground evenly

About the result -- I personally would only try to work on the shinogi in a consistent manner, easier to blend the wide bevels together, but you can do you.

I have used a cerax 320 for it -- just keep it flattened for wide bevel work. Softer stones are better for honyaki, compared to diamond. I've thinned 5 honyaki, and owned 2 honyaki usuba.

But, uh, really, if you have a picture in your mind of the knife in a certain geometry or shape, then I guess go for it. There's some videos on YouTube of Japanese makers in Sakai grinding usuba

 

[ag36]

If it were me, I just try to keep the shinogi consistent and even. If I wear down the knife near the tip, that means I need to use the heel more, or that would be the profile shape I use the most. So I would just raise the shinogi slightly near the tip. A super flat usuba is mainly a katsuramuki tool anyhow. Plus -- the knife will still wear down with sharpening. It's kinda like soles of shoes
They wear down with how they are used

About the result -- I personally would only try to work on the shinogi in a consistent manner, easier to blend the wide bevels together, but you can do you.

I have used a cerax 320 for it -- just keep it flattened for wide bevel work. Softer stones are better for honyaki, compared to diamond. I've thinned 5 honyaki, and owned 2 honyaki usuba.

But, uh, really, if you have a picture in your mind of the knife in a certain geometry or shape, then I guess go for it. There's some videos on YouTube of Japanese makers in Sakai grinding usuba

Thanks for the input!

I use usuba for almost every thing except hard vegetables like pupkin or swedes or meat, so it get the most wear in my collection.

The issue is, once the tip became too thin, therefore entire knife have to be tilted foward like this figure on the suisin website(２００７年８月期「直刃の難しさ！」).

When I tried rise the entire shinogi like you've mentinoed the tip broke away like a burr because of the tapering at the tip, which means the edge will tilt if you try to raise shinogi and keep the shinogi flat and keep the same thickness.

This is what I am trying to do, hasn't got there yet.


My naniwa kagayaki 220 and 400 works well with honyaki but 800 and above seems to clog often and 220 wears fairly quick, do you think cerax might do better?

 

[refcast]

Ah so you're trying to have the same angle wide bevel through the whole knife. @Kippington had a whole thread on that.

My go to were the cerax 320 and cerax 1000, though the cerax 1000 is a bit too hard and any stray particles from lower grit could gouge. . . But it's not the biggest problem.

Idk, the cerax wear pretty fast but you want them to wear quickly -- honyaki on a hard stone sucks, I've done that a couple times.

Also consider just microbeveling the tip and to no longer sharpen the tip close to the edge. That should help solve it. Usuba are really extreme geometry knives and I get scared using really thin sharpened ones.

 

[ag36]

Thanks! Need to look for the thread you've mentioned(hopefully I can find it)

I think I'll try the cerax 320, look like they're slightly thicker than the kagayaki.

Me too, exactly like you've said, honyaki on hard stone absolute sucks.

I tried two hard stones by naniwa and king and they both didn't work well with my honyaki even using a soft stone as nagura.

I usuall put a round bevel at the tip and hope it won't chip although it still chips occasionally, and microbevel for the rest of the edge too.

I think usuba is a bit of a "consumable" in this context, sometimes it chips by "look it wrong".

 

[refcast]

Yeah my Sakai made honyaki usuba was too thin and sold it -- it was only good for katsuramuki and no board work. My takagi usuba was thicker behind the edge and tough.

Stones I've tried:
Shapton glass 500
King 300
King 800
Gesshin 400
Sigma 400
Fsk / BBB vitrified diamond 400
Shapton pro 120
Gesshin 220
Shapton pro 1000
Suehiro debado coarse I forget which

The cerax 320 is still my favorite for speed and control. The pink brick stones I don't quite like as much but they're faster.. sometimes. They can refuse to self slurry sometimes or leak water too much ... I have been meaning to seal mine. Yeah I've tried nagura and even loose grit powder on hard stones and it dishes the stone but not abrades the knife.

I've owned like 10 usuba so far? Something like that, wide bevel sharpened all of them. Finnicky knives.

 

[ag36]

Thanks for the list!

I find shellac to be the best for sealing a stone, it worked wonderfully my on my natural stones.

Shellac penetrates the surface extremely well and made the self slurry much more controlled and less likely to chip too.

I almost tried the powders too but I was afraid of chipping the edge off.

I currently have 5 honyaki usuba and 2 clad, I think there's a charm of usuba, no matter how finicky they're, it's somehow addictive.

 

[Qapla']

A super flat usuba is mainly a katsuramuki tool anyhow.

I was under the impression that usuba's were supposed to be mostly flat? (Though I've seen exceptions.)

 

[ethompson]

Ususba are super tricky to keep the lines clean. The square shape and straight lines seem deceptively simple, when in reality they have a pretty complex geometry when done well (which is actually fairly uncommon in my experience) and it takes diligent effort to maintain that geometry over time. The bevel angle actually changes fairly dramatically to account for taper as you move from heel to tip. I'll see if I can find the 3d model I made that had harsh facets rather than blended convexity as it helped visualize the angle changes.

And I'll think through what the answer is for your blade. Am I correct that your goal is to bring the edge profile back in line with the spine?

 

[ethompson]

With any knife with distal taper, maintaining an even height shinogi as measured perpendicular to the edge requires a changing angle from heel to tip. The angle change can be quite severe, often being twice as acute at the tip as it would be at the heel.

This demo usuba (shown without ura or tang for simplicity sake) is 170mm in edge length tapering from 4mm over the heel to just under 2mm above the tip. The shinogi is an even height and a the hira is a simple plane with no convexity or concavity.

To keep the shinogi and edge in line with the spine, you need to account for these different angle as you sharpen. If you're a machine you could sharpen with precise facets as seen in the image below. One facet would run the full length of the shinogi and terminate at the tip edge corner. The other would run the full length of the edge and terminate at the heel shinogi corner. You’d have a sharp ridge like an extra shinogi between them. For what its worth, I’ve actually seen an usuba sharpened like this, it was wild to behold and a testament to the skill of the sharpener.

Obviously, this type of precision is unnatural and you don’t want a sharp edge in your kireha. So what you really want to shoot for is something like this. Here there is one set angle under the shinogi and another along the edge. This will give you a consistent angle with which to work the shinogi evenly, linearly pushing it up in tandem with the edge as you go. At the edge, you will likewise have consistent convexity into the apex which is great for strength and will also allow you to control abrasion / wear more readily as you sharpen. In between you see the same two facets mentioned above that show the changing overall kireha angle heel to tip. In practice, rather than hard angles, you want them to all blend together into one compound convex surface.

I find it easiest to think about the geometry in terms of facets - I'm actually in favor of making soft facets sometimes when reshaping a blade. You'll find naturally things blend together well, and if they don't the angle separation is usually subtle enough to blend together intentionally. Maintaining this type of geometry rather than trying to force a single plane on the usuba kireha will allow for even wear across the life of the knife.

Now lets look at two very extreme examples of what will happen if you don’t apply a complex grind to the bevel and try and coerce the blade into a perfectly planer kireha.This first example I’ve kept the heel height and shinogi height fixed - the perspective is a bit wack, but the spine to shinogi height is the same at the heel and tip. But “sharpened” away until the angle of the kireha at the heel and tip are even. As you can see the kireha height at the tip is now much, much shorter.

The second example I’ve done the opposite. The shinogi and overall height at the tip has been held constant and I’ve “sharpened” away at the heel until the kireha angle matches what is naturally found at the tip. The shinogi has been pushed up to accommodate to such an extent that the kireha blows through the hira and hits the spine.

These examples are extremes, obviously, but they're useful for diagnosing uneven wear and its cause.

In reality we are always dealing with grind we are felt and humans aren’t CNC machines. Hiras aren’t perfectly uniform planes, they’re usually concave, but occasionally convex too. You have to manipulate your surfaces based on existing shape to approximate the ideal.

 

[refcast]

@Qapla'

The edges on usuba are often made flat yes. . . And often come with recurves too from some Sakai makers. . . Depends how good they are at that stuff. A lot of edo usuba seem to have more belly and tip curve. Most used usuba I've seen don't keep a super precise flatness to their edge profile. I haven't read an interview in Japanese yet about edge profile correctness of how flat things should be. . . As always I imagine it's user preference, like different gyuto profiles

 

[Heckel7302]

With any knife with distal taper, maintaining an even height shinogi as measured perpendicular to the edge requires a changing angle from heel to tip. The angle change can be quite severe, often being twice as acute at the tip as it would be at the heel.

This demo usuba (shown without ura or tang for simplicity sake) is 170mm in edge length tapering from 4mm over the heel to just under 2mm above the tip. The shinogi is an even height and a the hira is a simple plane with no convexity or concavity.
View attachment 292257
To keep the shinogi and edge in line with the spine, you need to account for these different angle as you sharpen. If you're a machine you could sharpen with two sharp facets as seen in the image below. One facet would run the full length of the shinogi and terminate precisely at the tip edge corner. The other would run the full length of the edge and terminate at the heel shinogi corner. You’d have a sharp ridge like an extra shinogi between them. For what its worth, I’ve actually seen an usuba sharpened like this, it was wild to behold and a testament to the skill of the sharpener.
View attachment 292258
Obviously, this type of precision is unnatural and you don’t want a sharp edge in your kireha. So what you really want to shoot for is something like this. Here there is one angle under the shinogi and another along the edge. This will give you a consistent angle with which to work the shinogi evenly and linearly pushing it up in tandem with the edge as you go. At the edge, you will likewise have consistent convexity into the apex with is great for strength but will also allow you to control abrasion and wear more readily as you sharpen. In between you see the two facets mentioned above that show the changing overall kireha angle heel to tip. Rather than hard angles, you want them to all blend together into one compound convex surface.
View attachment 292264
I find it easiest to think about the geometry in terms of facets - I'm actually in favor of making soft facets sometimes when reshaping a blade. You'll find naturally things blend together well, and if they don't the angle separation is usually subtle enough to blend together intentionally. Maintaining this type of geometry rather than trying to force a single plane on the usuba kireha will allow for even wear across the life of the knife.

Now lets look at two very extreme examples of what will happen if you don’t apply a complex grind to the bevel and try and coerce the blade into a perfectly planer kireha.This first example I’ve kept the heel height and shinogi height fixed - the perspective is a bit wack, but the spine to shinogi height is the same at the heel and tip. But “sharpened” away until the angle of the kireha at the heel and tip are even. As you can see the kireha height at the tip is now much, much shorter.
View attachment 292265
The second example I’ve done the opposite. The shinogi and overall height at the tip has been held constant and I’ve “sharpened” away at the heel until the kireha angle matches what is naturally found at the tip. The shinogi has been pushed up to accommodate to such an extent that the kireha blows through the hira and hits the spine.
View attachment 292266
These examples are extremes, obviously, but they're useful for diagnosing uneven wear and its cause.

In reality we are always dealing with grind we are felt and humans aren’t CNC machines. Hiras aren’t perfectly uniform planes, they’re usually concave, but occasionally convex too. You have to manipulate your surfaces based on existing shape to approximate the ideal.

Such a good explanation.

 

[simona]

A similar explanation but with yanagiba's the principles are the same



He has a small group of excellent videos around this subject.

 

[ag36]

With any knife with distal taper, maintaining an even height shinogi as measured perpendicular to the edge requires a changing angle from heel to tip. The angle change can be quite severe, often being twice as acute at the tip as it would be at the heel.

This demo usuba (shown without ura or tang for simplicity sake) is 170mm in edge length tapering from 4mm over the heel to just under 2mm above the tip. The shinogi is an even height and a the hira is a simple plane with no convexity or concavity.
View attachment 292257
To keep the shinogi and edge in line with the spine, you need to account for these different angle as you sharpen. If you're a machine you could sharpen with two sharp facets as seen in the image below. One facet would run the full length of the shinogi and terminate precisely at the tip edge corner. The other would run the full length of the edge and terminate at the heel shinogi corner. You’d have a sharp ridge like an extra shinogi between them. For what its worth, I’ve actually seen an usuba sharpened like this, it was wild to behold and a testament to the skill of the sharpener.
View attachment 292258
Obviously, this type of precision is unnatural and you don’t want a sharp edge in your kireha. So what you really want to shoot for is something like this. Here there is one angle under the shinogi and another along the edge. This will give you a consistent angle with which to work the shinogi evenly and linearly pushing it up in tandem with the edge as you go. At the edge, you will likewise have consistent convexity into the apex with is great for strength but will also allow you to control abrasion and wear more readily as you sharpen. In between you see the two facets mentioned above that show the changing overall kireha angle heel to tip. Rather than hard angles, you want them to all blend together into one compound convex surface.
View attachment 292264
I find it easiest to think about the geometry in terms of facets - I'm actually in favor of making soft facets sometimes when reshaping a blade. You'll find naturally things blend together well, and if they don't the angle separation is usually subtle enough to blend together intentionally. Maintaining this type of geometry rather than trying to force a single plane on the usuba kireha will allow for even wear across the life of the knife.

Now lets look at two very extreme examples of what will happen if you don’t apply a complex grind to the bevel and try and coerce the blade into a perfectly planer kireha.This first example I’ve kept the heel height and shinogi height fixed - the perspective is a bit wack, but the spine to shinogi height is the same at the heel and tip. But “sharpened” away until the angle of the kireha at the heel and tip are even. As you can see the kireha height at the tip is now much, much shorter.
View attachment 292265
The second example I’ve done the opposite. The shinogi and overall height at the tip has been held constant and I’ve “sharpened” away at the heel until the kireha angle matches what is naturally found at the tip. The shinogi has been pushed up to accommodate to such an extent that the kireha blows through the hira and hits the spine.
View attachment 292266
These examples are extremes, obviously, but they're useful for diagnosing uneven wear and its cause.

In reality we are always dealing with grind we are felt and humans aren’t CNC machines. Hiras aren’t perfectly uniform planes, they’re usually concave, but occasionally convex too. You have to manipulate your surfaces based on existing shape to approximate the ideal.

Thank you so much for the CAD and the detailed explanation, they cleared all my doubts now.

I think the current knive I am thinning is closer to the extreme example no.1 now and it's moving towards no.2,
if only I had seen your graph first I would done it similar to your first two graphs assuming I had enough thickness left at the base of the edge.

I lost the original convex from bad habits,
after using the knife with a large secondary bevel for a few years.

When the bevel worn off I forgot what the knife used to look,
I set new bevel angle exact to one of my other usuba without checking how much thickness I have left at the heel and tip to avoid bulging the belly and more correction followed and mistakes were made.

I think I'll try to blend the shinogi with a compound convex to the shinogi to balance it on my next sharpening like your second graph.

@Qapla'

The edges on usuba are often made flat yes. . . And often come with recurves too from some Sakai makers. . . Depends how good they are at that stuff. A lot of edo usuba seem to have more belly and tip curve. Most used usuba I've seen don't keep a super precise flatness to their edge profile. I haven't read an interview in Japanese yet about edge profile correctness of how flat things should be. . . As always I imagine it's user preference, like different gyuto profiles

I think that's exact case because the second hand unused Nenohi blue 2 kama-usuba is a smooth convex and the Masakuni usuba(steel type unkown) is flat.
Jikko blue 2 honyaki I bought new is two part blended convex like your 2nd graph and Akitada didn't have a honbatsuke option.



I think it's a bit like Shobu(正夫) vs Yanagiba but never fully formalised.

A similar explanation but with yanagiba's the principles are the same



He has a small group of excellent videos around this subject.

Nice video with clear and straight to point explanation! Great drawing skill too.

The principle is the same although it seem to be much more extreme on Usuba, maybe Soba-kiri too.

 

[simona]

I must say it's a brain squeeze! I bought a cheap-as-chips kamagata usuba to have something to try, and it took me exactly 2 hours to mess it up! The bevel is sort of flat, the cutting edge is no where near straight
It will take some time....

 

[ag36]

I must say it's a brain squeeze! I bought a cheap-as-chips kamagata usuba to have something to try, and it took me exactly 2 hours to mess it up! The bevel is sort of flat, the cutting edge is no where near straight
It will take some time....

That's also what happend to my first Usuba(also my frist single bevel).

The one I am currently working on(the one in the first post) was the first honyaki I've bought(Akitada white 3).

 

[simona]

Another take on the same theme -

 

[Lurkernomore]

If your edge crumpled away while trying to raise the shinogi your finger placement was off. You were too close to the edge.
I feel like everything is getting theorized way too much. If you move your fingers from the edge to the shinogi gradually while sharpening the whole hamaguri angle blending thing happens naturally.

 

[ag36]

If your edge crumpled away while trying to raise the shinogi your finger placement was off. You were too close to the edge.
I feel like everything is getting theorized way too much. If you move your fingers from the edge to the shinogi gradually while sharpening the whole hamaguri angle blending thing happens naturally.

I only touched shinogi after the tip became too thin, as you've said there is no way edge would come off if someone is working on the shinogi.

I had to theorise it because the knife was not in good shape after using it with a secondary bevel and non-ideal sharping habits for few years, otherwise following the original shape is usually the best way to do it.

If the knife was in good condition there is no need to do this.

 

[bsfsu]

A similar explanation but with yanagiba's the principles are the same



He has a small group of excellent videos around this subject.

I like this guy's vids too! He has some good information about Japanese knives.

 

[ag36]

I thinned the belly and hira a little more and straightened the edge.

Ura is slightly warping as the omote is being thinned but not enough to be a problem.

My experience so far,
White 3 can be sharpened thinner than clad and distort less, however have less carbide so the edge won't be microscopic saw.

White 3 don't bite whetstone as nicely as white 2 or 1 but the burr are not as hard to remove as Blue steel.

Durability wise, White 3 Honyaki wears slower than White 2 clad but faster than Blue 2 clad.
The edge is less likely to chip than White 2 Honyaki, roughly same as Blue 2 Honyaki but dulls quicker.

It chips like white more than blue, small chips rather than a big wide one, remains fairly sharp after the burr chips.

I've read that White 3 Honyaki is no longer being made due to rising cost,
as white 3 Honyaki were made as the budget option for a more apparent Hamon.

(Comparisons were made with Oil quenched Honyaki as I don't have experience with water quenched ones to compare with.)