single bevel sharpening

[noj]

I have a new-ish single bevel knife, and a question on sharpening.

The knife, as new, was ground so badly, I sent it off for professional help. They did a good job of fixing the major problem: the entire flat section had a significant frown. It may have had other issues, but it was hard to tell with the frown. The knife came back with the frown gone, and nice flat surfaces (no concave spots).

The knife cut ok, but felt like it wasn't thin behind the edge. I lived with it, until it needed sharpening.

The issue at hand is the bevel between the lamination line and edge. When I place pressure very near the edge, there is no obvious angle I can feel. If I continue to grind in that manner, it's taking what seems like forever to remove the old "micro-bevel" (it looked like a macro-bevel to me). In fact, I can't really get to the edge without rotating the blade, which of course would make matters worse.

When I look at that surface in the knife, I see increasing convexity as I (visually) approach the edge. The last 2 millimeters are highly curved. The lamination line is about 6-8 mm from the edge. I would have expected most of the convexity to be near the lamination line, where the bevels are smoothed together. I am writing to confirm my expectations, and to inquire how I can make the blade better. I am not going to make complaints against the professional sharpener.

I am not sure how to proceed. Is the hamaguri geometry I described expected, or should be preserved? It doesn't match my understanding.

I was thinking of using a coarser stone to grind the entire bevel flat to the edge.
Perhaps I can get roughly the right angle on the bevel from lamination line to edge by just adjusting pressure afterward.

Please comment on my idea, or suggest a better approach.

Thanks in advance!

 

[M1k3]

Any pictures?

 

[noj]

Any pictures?

Just uploaded

 

[adam92]

You will find the answer how to sharpen single bevel knife from Jon video. It is very useful.

 

[noj]

In case it helps understanding where I am coming from, much of what I know about single bevel sharpening comes from Jon at JKI. But thanks for the tip. It doesn't help with my questions though. If you compare my questions to Jon's videos, it's the difference between the geometry of my knife, and what is in the videos that is at the heart of my problem.

 

[Greasylake]

If you wanted to thin the knife, you would need to move the shinogi up by doing shinogi sharpening like Jon does in the video, but I think you might notice an improvement by just grinding down some of the convexity and essentially thinning just behind the edge. You'll need a coarse stone for that, or it'll take forever. If it were my knife I would probably put it on a coarse stone until I ground down that big edge bevel and put my own edge on it, then see how it cuts before moving the shinogi. You are right that the convexity should be where the bevels are blended, convexity towards the edge is usually from not keeping a consistent angle (ask me how I know )

 

[noj]

[snip]

Thanks for the reply. That gives me more confidence I am on the right track.

The whole blade geometry wasn't my doing. Not so far anyhow!

Regardless of where the convexity (and dang macro-bevel) came from, it sure makes knife sharpening a chore. I spent an hour on a 1000 grit to reduce the "micro-bevel" thickness by half. Add to that no feedback on the angle (from lamination line to edge), and I wasn't having fun.

I'll carefully read any other feedback, but if not, will try your approach, if I understand it. I think the only way to remove the convexity near the edge is to first grind the wide bevel dead flat (from shinogi to edge). After that, re-grind a secondary (larger) angle from lamination line to edge. Can that be done by just applying finger pressure near the edge? Setting that bevel consistently by hand, just a few degrees higher, would be a challenge.

 

[adam92]

Hope to see your result soon.

 

[noj]

Any stone recommendation for the course stone? The only one I have (under 400 grit) is quite soft. It works great for thinning convex double bevels. I am not sure I trust it for setting a flat surface.

 

[Greasylake]

Shapton glass 500 is what I use

 

[M1k3]

Norton Crystolon Medium
Norton India Medium
King 300
Shapton Pro or Glass 120

 

[ian]

I'll carefully read any other feedback, but if not, will try your approach, if I understand it. I think the only way to remove the convexity near the edge is to first grind the wide bevel dead flat (from shinogi to edge). After that, re-grind a secondary (larger) angle from lamination line to edge. Can that be done by just applying finger pressure near the edge? Setting that bevel consistently by hand, just a few degrees higher, would be a challenge.

This all sounds good. Finger pressure is the way to go here. Don't try to set and hold a steeper angle. I suppose if you want to end up with more convexity, you could do most of your thinning with finger pressure near the edge.

 

[noj]

This all sounds good. Finger pressure is the way to go here. Don't try to set and hold a steeper angle. I suppose if you want to end up with more convexity, you could do most of your thinning with finger pressure near the edge.

When I mentioned finger pressure near the edge, I was proposing using it to promote the (larger angle) bevel between lamination line and edge. I have no clue how else to do it. Ideally, it (bevel between lamination line and edge) would not be convex. I suspect there will be a little convexity because it's done by hand (with imperfect skills). It would be akin to the method used to sharpen a single bevel if it didn't have this issue.

 

[noj]

Here's the result after an hour on 400 grit stone. Looks like I need to get one with coarser grit.

 

[noj]

Sadly, the convexity toward the edge isn't uniform. It's worse near the heel, as can be seen from the black marker. The left hand side of photo is nearest the heel. I know I didn't put it there because I can still see the micro-bevel.

 

[Pie]

I say get a coarser stone sooner rather than later - the more strokes, the more time, the more chances to get lulled into the wrong angle and bung the whole thing up. (Also ask me how I know )

To my entirely untrained eye it looks like you may have a ways to go to get the heel part flat. One thing to note is if you want the whole thing proper flat, you will need to take care in removing steel evenly along the full length of the blade, as to avoid waviness of the bevel.

Last thing is I’ve found my fingers quite poor at applying pressure to just the core steel. My solution is to use my fingernails to apply pressure as close to the edge as possible. It works quite well, but can leave marks in the steel. Keep this in mind re: what your ura looks like after all of this.

Man, good luck, and I mean it with no sarcasm whatsoever. I’ve never gone this far on a single bevel before, and it looks terrifying.

 

[noj]

I say get a coarser stone sooner rather than later - the more strokes, the more time, the more chances to get lulled into the wrong angle and bung the whole thing up. (Also ask me how I know )

To my entirely untrained eye it looks like you may have a ways to go to get the heel part flat. One thing to note is if you want the whole the proper flat, you will need to take care in removing steel evenly along the full length of the blade, as to avoid waviness of the bevel.

Last thing is I’ve found my fingers quite poor at applying pressure to just the core steel. My solution is to use my fingernails to apply pressure as close to the edge as possible. It works quite well, but can leave marks in the steel. Keep this in mind re: what your ura looks like after all of this.

Man, good luck, and I mean it with no sarcasm whatsoever. I’ve never gone this far on a single bevel before, and it looks terrifying.

If you think this looks bad, here's what the edge looked like from the knife maker. I didn't grind it enough to change the geometry. I marked the edge with magic marker, and started it on a 1000 grit stone to see what I was dealing with. I gave up, and sent it in for professional repairs. The topics discussed here are all after that repair.

Edge as brand new:

 

[noj]

A sideways question I have been asking myself, should I just get a different knife?

I am sure I can learn something from the process of fixing it. I enjoy learning more about sharpening, maintenance, technique (use).

That said, I am not a knife maker, and there's more injury risk.

It would make one of the world's most expensive garden tools though.

 

[adam92]

A sideways question I have been asking myself, should I just get a different knife?

I am sure I can learn something from the process of fixing it. I enjoy learning more about sharpening, maintenance, technique (use).

That said, I am not a knife maker, and there's more injury risk.

It would make one of the world's most expensive garden tools though.

I don't think you need a different knife, just need a coarse stone to save your time, I'm using Naniwa pink brick 220 grit for setting bevel/ fixing chips, SG 220 work fine as well.

 

[Pie]

A sideways question I have been asking myself, should I just get a different knife?

I am sure I can learn something from the process of fixing it. I enjoy learning more about sharpening, maintenance, technique (use).

That said, I am not a knife maker, and there's more injury risk.

It would make one of the world's most expensive garden tools though.

For use? Maybe. For learning? This is a pretty good opportunity.. provided you enjoy putting in the time, I suppose. It’s already started as a project knife tho.

 

[stringer]

A sideways question I have been asking myself, should I just get a different knife?

I am sure I can learn something from the process of fixing it. I enjoy learning more about sharpening, maintenance, technique (use).

That said, I am not a knife maker, and there's more injury risk.

It would make one of the world's most expensive garden tools though.

If you enjoy learning about this stuff then keep working on it. Get another one to check and compare your work after you've had a chance to make it your own in a few months or a year. You can't break it completely by just continuing to work on it with stones. Be patient. Be kind to yourself. No one is born a knife sharpener or knife maker. It takes time. Have fun. Keep asking lots of questions.

 

[ian]

When I mentioned finger pressure near the edge, I was proposing using it to promote the (larger angle) bevel between lamination line and edge. I have no clue how else to do it. Ideally, it (bevel between lamination line and edge) would not be convex. I suspect there will be a little convexity because it's done by hand (with imperfect skills). It would be akin to the method used to sharpen a single bevel if it didn't have this issue.

Yea, that’s what I was saying. Usually with hamaguri sharpening you end up with the wide bevel divided into two flat-ish bevels of roughly equal size that are blended where they meet. You create the two angles by varying the placement of your finger pressure. I was just mentioning that since currently it’s quite thick behind the edge, if you want to save some effort and end up with more convexity (ie a bigger difference between the angles of those two bevels) than you usually get with hamaguri sharpening, you can thin while mostly keeping your finger pressure on the lower half of the wide bevel. If you do this, you may end up with more convexity than is typical on a single bevel, but if you don’t end up liking that you can of course keep going and flatten it.

 

[noj]

Yea, that’s what I was saying. Usually with hamaguri sharpening you end up with the wide bevel divided into two flat-ish bevels of roughly equal size that are blended where they meet. You create the two angles by varying the placement of your finger pressure. I was just mentioning that since currently it’s quite thick behind the edge, if you want to save some effort and end up with more convexity (ie a bigger difference between the angles of those two bevels) than you usually get with hamaguri sharpening, you can thin while mostly keeping your finger pressure on the lower half of the wide bevel. If you do this, you may end up with more convexity than is typical on a single bevel, but if you don’t end up liking that you can of course keep going and flatten it.

I started down this path, albeit with a stone of too high grit. The problem I had was that the convexity (curvature) accelerated as you approach the edge, and most of it in the last 2 mm. If you apply finger pressure near the edge, there is no flat spot (natural angle) for reference. In fact there's air right underneath the edge. OK, stone slurry, not air;-) With no angle reference, I don't think I can do a good job by hand. So, I think I am stuck having to flatten it.

 

[noj]

Thanks for the encouragement. I'll get a course stone, and see what I can do.

It may have been answered before, but I want to be sure I understand your ideas. Assume I flatten the entire bevel (shinogi line to edge). Should I set a second bevel from the lamination line to edge? If yes, how?

I think everyone said just finger pressure near the edge. Just checking my understanding. My guess is that procedure will tend to create a gentle convexity, simply because it's done by hand. Would it be best to create that second bevel by grinding it there with my course stone, or sort of let it evolve with normal sharpening.

Thanks in advance.

 

[psfred]

Good thing I happened to take a peek at this thread. I'm fixing a yanagiba at the moment that had a rough secondary bevel on it when I got it (not an expensive knife or I'd have sent it back) that I proceeded to make very much worse by attempting to use my belt sander to remove the bulk of the excess bevel to get close enough to the edge. Big mistake, it was at the wrong angle and grabbed, so I've been grinding away off and on for a year and a half to fix it.

I'm using a King Deluxe 300, and having to "sharpen" the stone fairly often, the knife is very hard single steel and I have a huge amount to remove to fix my screw-up. What really speeds things up is some 60 grit silicon carbide loose grit on the stone and a minute or two of grinding with a piece of sandstone I'm flattening to use with straight razors and chisels. Once the 60 grit stops rolling freely I grind on the knife for a while keeping the slurry on the stone as long as I can -- it cuts VERY fast. Also keeps the 300 flat and cutting well. Don't do this if the 60 grit will reach the actual edge, as noted below.

I'll try to take a pic tonight, I'm approaching the edge after six or seven hours of grinding, total, on that 300 grit stone. The ura is in rough shape, but still deep enough I think I can get the edge properly sharp, it wasn't very deep or well executed, but then, again, this isn't an expensive knife. Cost enough I don't want to toss it, but not that high.

My advice, for what it's worth, is to grind on the coarse stone until you are near to where you want the secondary bevel to start, the switch to a finer stone (600 grit maybe) and approach but do not grind into the edge, when you are very close switch to a 1000 or 1200 grit stone and finish as per usual. The reason I suggest this plan of action is to avoid deep scratches at the actual edge. Coarse stone scratches at the edge are almost invariably accompanied by micro-cracks, and the very hard steel there will polish up nicely on the finer stones without removing them completely. In use the edge will chip easily as those cracks grow with stress. Takes longer, but I suspect the edge will last longer. Something I learned from honing straight razors, or at least trying to hone them. Diamond "stones" are the very worst at this, as the particles are very angular and make deep, V-bottom scratches.

For the actual geometry, probably pressure mid bevel until you switch to a finer stone, then edge pressure to get the slight convexity you want. That's what I will be doing when I get that far, still have way too much hard steel to grind off at the moment to worry about the edge profile yet, gotta get the gouges out first.

 

[noj]

[snip]

Thanks for the detailed write up, and especially the advice on course scratches near the edge. The problem though is I have it flat to the point where the secondary bevel should start. Because of the heavy convexity in the last 2 mm, I have no reference to set the secondary bevel. See photo above. If I place my fingers near the edge, there is no natural angle (no flatness whatsoever) to grind at. I know I don't have the skills to hold a 2 degree angle (or whatever the difference would be between the bevels) by hand. I tried that first. I think I have to grind it dead flat out to nearly the edge first. Other ideas welcome though.

I'm going to start with a Shapton Pro 120, and see how that works. I might try your trick with the silicon carbide grit if I have issues.

This knife was awful from the day it arrived. Neither the vendor or knife maker would accept a return, or even "re-sharpen" it.

 

[ian]

Thanks for the detailed write up, and especially the advice on course scratches near the edge. The problem though is I have it flat to the point where the secondary bevel should start. Because of the heavy convexity in the last 2 mm, I have no reference to set the secondary bevel. See photo above. If I place my fingers near the edge, there is no natural angle (no flatness whatsoever) to grind at. I know I don't have the skills to hold a 2 degree angle (or whatever the difference would be between the bevels) by hand. I tried that first. I think I have to grind it dead flat out to nearly the edge first. Other ideas welcome though.

I'm going to start with a Shapton Pro 120, and see how that works. I might try your trick with the silicon carbide grit if I have issues.

This knife was awful from the day it arrived. Neither the vendor or knife maker would accept a return, or even "re-sharpen" it.

If you want to try something other than grinding a dead flat, rest it flat on the wide bevel, and then put your finger pressure as low down as you can without making the knife wobble. Steel will be abraded more quickly under your fingers, so you’ll eventually create some convexity. You could even keep pushing your fingers down lower when it seems like you can hold the angle without a wobble.

All this will be easier on a coarse stone, though. With a faster stone, you’ll be able to cut in a much more uniform bevel, since you won’t have to hold the same angle for a billion strokes.

 

[psfred]

I sympathize. Mine was barely usable out of the box, and after I screwed it up there wasn't any possibility of returning it even if the vendor would have taken a return. Profile was fine though, just a marked bevel at the edge which should not be there.

I could be wrong, but I was under the impression that a yanagiba should not have a secondary bevel of any size, just the convexity provided by pressure just behind the edge while sharpening, with the rest of the very wide bevel dead flat. In other words, if you can feel or see it, it's too big.

That would mean more grinding for you, and a ton more for me!

 

[noj]

I sympathize. Mine was barely usable out of the box, and after I screwed it up there wasn't any possibility of returning it even if the vendor would have taken a return. Profile was fine though, just a marked bevel at the edge which should not be there.

I could be wrong, but I was under the impression that a yanagiba should not have a secondary bevel of any size, just the convexity provided by pressure just behind the edge while sharpening, with the rest of the very wide bevel dead flat. In other words, if you can feel or see it, it's too big.

That would mean more grinding for you, and a ton more for me!

I'll let folks with more experience than me answer the question about what the bevel is supposed to be.

What I was hoping for in a secondary bevel is a reference angle for sharpening the edge (and getting a burr) by finger pressure and placement near the edge. Specifically, only by finger placement, and not using a forced rotation from the wrist. If it helps making a better contrast between hagane and jigane, all the better.

 

[SilverSwarfer]

I once had a seriously damaged yanagiba, and subsequently had opportunity to have it repaired professionally. The work was well done and I was able to repurpose the knife. However, I found myself in a similar situation as OP: I was dissatisfied with the new bevel profile. There was a hamaguri arc from shinogi to koba but the new setup was much thicker behind the edge and the microbevel was just obtuse beyond what I think/find to be useful.

The particular subject knife is honyaki and really pretty difficult to grind (this may be why the repaired condition ended up 'too thick'). My approach has been to chip away at the thinning and most importantly: raising of the shinogi line. If I can offer any advice it is to be patient and parse out your work over many sessions. Stop whenever you get fatigued or frustrated. Inspect your work often and use a sharpie if the scratch pattern is difficult to read.

Even if you end up less happy with the product of your work, you will definitely learn from the experience and develop your technique. IMO it's important to build enough skill to be able to raise your shinogi evenly and follow its original curve.

Sadly, the convexity toward the edge isn't uniform. It's worse near the heel, as can be seen from the black marker. The left hand side of photo is nearest the heel. I know I didn't put it there because I can still see the micro-bevel.

Some folks build a little extra convexity/thickness near the heel as a feature to fortify that region for tougher tasks that might cause chipping. Maybe the sharpener intended this?