sharpening the tip of a knife

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MowgFace

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All great tips above.

I could also recommend picking up a Masahiro Carbon Gyuto from Amazon for ~50 bucks and use that as your knife work guinea pig.

Wanna try rounding your choil? Masahiro! Thinning? Masahiro! Re-tip? Masahiro! Western to WA conversion? Masahiro!

A lot of my early sharpening was on crappy cheap steel, and while it provided some reps and experience, wasnt 100% translatable to quality steel. While i think the Masahiro is softer, in the 58-59 range I think its darn close to what you could expect from harder Japanese knives.

I dont have any experience with the Fujitora Molybdenum line, sometimes called Fuji Narihara (Made by Tojiro Parent Co) but $34 for a 240 gyuto to sacrifice to science ain't too bad.
 

noj

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All great tips above.

I could also recommend picking up a Masahiro Carbon Gyuto from Amazon for ~50 bucks and use that as your knife work guinea pig.

Wanna try rounding your choil? Masahiro! Thinning? Masahiro! Re-tip? Masahiro! Western to WA conversion? Masahiro!

A lot of my early sharpening was on crappy cheap steel, and while it provided some reps and experience, wasnt 100% translatable to quality steel. While i think the Masahiro is softer, in the 58-59 range I think its darn close to what you could expect from harder Japanese knives.

I dont have any experience with the Fujitora Molybdenum line, sometimes called Fuji Narihara (Made by Tojiro Parent Co) but $34 for a 240 gyuto to sacrifice to science ain't too bad.
I'll consider your suggestions, thanks. My current "practice" knife is an old Sabatier chef's knife. I bought this brand new when I was about 18. Post your estimates of my age elsewhere;-) The steel is very soft. I can get a burr by looking at it, and bends pretty easy side-to side. 20220811_135541[1].jpg
 

HumbleHomeCook

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It may just be the light and/or this may be what kicked off your inquiry, but in that picture, the belly looks like you've indeed been too flat.
 

noj

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It may just be the light and/or this may be what kicked off your inquiry, but in that picture, the belly looks like you've indeed been too flat.
It's a bad photo. I tried to capture the edge, but all I got was light glare (and adjacent lit-up pixels). Actually, I originally had the handle too high, and almost no rotation. After adjusting my technique, it looked pretty good (checked using a magic marker). With the marker removed, I haven't ground away all the evidence. I'll do that either over time, or if I have nothing better to do;-)
 

Benuser

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There's a lot of variety in tips amongst vintage Sabs, from Sheffield-like spear points to much more obtuse ones, with a late upswing, which seems the most common. From the point of view on the photo I find it hard to see. It looks like it's in the first category.
 

Desert Rat

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I know lots of people deburr with edge leading strokes, I do.

I'm not criticizing this guy in the video or anyone that takes edge leading strokes like this.
But for me the tips or point of my knifes improved when I learned to stop on the stone rather than flick the tip off of the stone.
 

Benuser

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I know lots of people deburr with edge leading strokes, I do.

I'm not criticizing this guy in the video or anyone that takes edge leading strokes like this.
But for me the tips or point of my knifes improved when I learned to stop on the stone rather than flick the tip off of the stone.

Quite sure the tip will end far too high. And the heel section is being neglected.
 

noj

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There's a lot of variety in tips amongst vintage Sabs, from Sheffield-like spear points to much more obtuse ones, with a late upswing, which seems the most common. From the point of view on the photo I find it hard to see. It looks like it's in the first category.
It's also due to years of use and abuse;-) The tip was well rounded over from the years I didn't pay much attention to sharpening skills. Anyhow, I recently removed about 1/2 inch off the tip, re-ground the profile and then primary bevel (both near the tip) so it was evenly thin behind the edge, and decided it was a great time to learn how to do the tips better. I think I made the knife more pointy than it was as new.
 

noj

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Quite sure the tip will end far too high. And the heel section is being neglected.
From my picture, or the video?

I can tell you my photo is awful. Between the glare distortions, multiple bright lights (and shadows in reflections between), I don't even recognize what that's a picture of;-)
 

sansho

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what i've been doing lately is rotating the whole knife in-plane and keeping the tangent of the bevel's curve at the same position. slower, but i feel like i've been getting more consistent results.
 
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The way I always explain this is as follows.

Take the knife and set it on its edge like you would when you cut something. Now rock the knife, and going from heel to tip. Now take the knife, and angle it like you would when sharpening, and do the same rocking motion.

That's what you should be doing when sharpening the tip. Raising, or lowering the spine shouldn't really be happening ideally. Unless you are purposely changing the angle you are sharpening at going from heel to spine.

I usually describe what I just said in person so I can give a visual example of rocking the knife. I hope what I mean is coming through.
 

Delat

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From my picture, or the video?

I can tell you my photo is awful. Between the glare distortions, multiple bright lights (and shadows in reflections between), I don't even recognize what that's a picture of;-)

The video - if you watch carefully you’ll notice the heel spends almost no time on the stone vs the rest of the edge. With both blade faces he starts the heel on the right side of the stone and immediately pulls it off to the same right side.
 

Benuser

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From my picture, or the video?

I can tell you my photo is awful. Between the glare distortions, multiple bright lights (and shadows in reflections between), I don't even recognize what that's a picture of;-)
The video.
 

Benuser

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It's also due to years of use and abuse;-) The tip was well rounded over from the years I didn't pay much attention to sharpening skills. Anyhow, I recently removed about 1/2 inch off the tip, re-ground the profile and then primary bevel (both near the tip) so it was evenly thin behind the edge, and decided it was a great time to learn how to do the tips better. I think I made the knife more pointy than it was as new.
The removed 0.5" explains a lot. Quite a drastic measure: not only because of the length loss, but as well because of the distal taper: the flimsy tip of a Sab is a characteristic feature. An overly rounded tip may not be that appealing, but still is perfectly functional.
 

natto

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what i've been doing lately is rotating the whole knife in-plane and keeping the tangent of the bevel's curve at the same position. slower, but i feel like i've been getting more consistent results.
I learned sharpening that way, and never changed. The picture was easy enough to understand to me. Like @noj showed in this post:


Here is a thought experiment, and pictures. First, as perhaps an
oversimplification, imagine your control of the knife is on just two
axis: your wrist (rotation angle along the axis of your knife handle),
and your wrist height. Of course, the human body is more complicated,
but let's focus on these because they are the primary ones involved.

Here is my model of a knife. Note the bevel angle is constant.
At any point along the curve of the "blade", the position of the
knife and handle isn't in question (assuming you want a constant
bevel angle).

View attachment 191934

Here is the position when grinding along (what would normally be) the
flatter part of the knife. Note the wrist angle and height.

View attachment 191935

Here is the position when grinding as you start getting into the curve
approaching the tip. Note the wrist angle and height. The angle is
decreased, and the height is increased. Again, by angle I mean
rotation angle along the axis of your knife handle, err paint stick;-)
The edge angle is constant (as determined by my junky plastic plate).


View attachment 191936

Still not sure? Let's push it to a (probably unrealistic) position
where the blade bends a full 90 degrees. The angle is now zero.

View attachment 191937

I conclude that under the assumption that we maintain a constant bevel
angle, and have two means of control (rotation angle along the axis
of your knife handle, and handle height), you must raise the handle
and rotate to a lower angle.

Your thread got me thinking through this lifting and rotating.

With curved tips, like on a rocking knife, rotating in a plane needs a wide sweep of the handle. Rotating and lifting should need less movement of the handle. And this wide sweep does not improve my consistency. Keeping the angle needs attention with unusual movements.

Rocking and lifting is the other way round. Without an idea, how much to rotate and lift, my attention is on the feel. I got to check it out.

Great thread, and thank you @noj.
 

noj

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I learned sharpening that way, and never changed. The picture was easy enough to understand to me. Like @noj showed in this post:




Your thread got me thinking through this lifting and rotating.

With curved tips, like on a rocking knife, rotating in a plane needs a wide sweep of the handle. Rotating and lifting should need less movement of the handle. And this wide sweep does not improve my consistency. Keeping the angle needs attention with unusual movements.

Rocking and lifting is the other way round. Without an idea, how much to rotate and lift, my attention is on the feel. I got to check it out.

Great thread, and thank you @noj.
You're welcome;-)

A first step (for the way I think about things) was to understand the physics and geometry. The next step (for the way I think about things) is technique and results. That incudes both the (less than theoretical) horizontal rotation around the point of contact, moving point of contact, human ergonomics, and individual preferences. I think I have a good start on a method; I'll have to see what I can do with it.
---------------- self-quote ---------------
"Once you realize that in order to maintain a constant angle, there is one and only one position (excluding of course a theoretical 360 degree horizontal rotation around the point of contact), you have an answer. How you do [it] physically, or explain it may be more complicated, but the geometry is now clear."
 

noj

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The removed 0.5" explains a lot. Quite a drastic measure: not only because of the length loss, but as well because of the distal taper: the flimsy tip of a Sab is a characteristic feature. An overly rounded tip may not be that appealing, but still is perfectly functional.
Drastic, I know, but one of the fun things about getting some new knives can be getting permission to go and fix your old one(s). I have already done a lot of work on that old Sabatier, but that's a story for another day.
 

noj

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I tried the two basic methods described here. Specifically, lifting/rotating vs sweeping (for lack of better name). I seem to get good results with both. My confidence improved a lot when I could get fast feedback on an inexpensive knife. I used by old Sab. It only too a couple strokes, and I could watch the tip go from too-much-rotation to spot-on (after I reduced rotation, and raised the handle to compensate). The hard part is getting the intuition or muscle memory about the balance between the two (lifting/rotating). I'll have to play around more with the sweeping method; it's just a little harder to know what aspect(s) to correct if it doesn't come out right. Anyhow, I'll keep playing with my poor old Sab when I have time.
 

Benuser

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Tried that on an old Sabatier chef's knife. The metal is so soft that I had to use 25+ degrees per side to get something (almost) stable, and easily bends side to side anywhere near the tip. Thanks for the idea though.
If it is a carbon steel one I guess it has to do with steel fatigued by excessive steeling or overheating by sharpening on a dry grinding wheel which was very common in the old days. Have one that only took an edge after removing something like 10mm of width. If you aren't familiar with the feeling on the stones you will notice it can't be deburred. A carbon Sab should easily take a 25 or 30° inclusive edge. Not advisable, but perfectly possible.
 

noj

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It's a carbon steel one. I got it brand new around 1980. It has never been sharpened on anything but a stone, or heated in anything but hot water from a faucet when rinsing it. The steel is very very soft. A 30 degree inclusive will go dull, and edge visibly missing spots after cutting one onion (just a random example). I wasn't rock-chopping, and I use either a soft wood board or Hasegawa FSR. I deburr with leading edge strokes are a slightly higher angle, and I have checked using cork and wood (not every time I sharpen of course) that I got rid of it. None of my other knives do this, so I doubt it's technique.

Just double checked, so a bit of a correction. My "angle guide" I use for it is 21 degrees, so that's 42 inclusive. The "guide" is just a home made piece of wood for reference. I don't have the muscle memory for angles like that, and the feedback from the metal is mostly nonexistent.
 
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Benuser

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It's a carbon steel one. I got it brand new around 1980. It has never been sharpened on anything but a stone, or heated in anything but hot water from a faucet when rinsing it. The steel is very very soft. A 30 degree inclusive will go dull, and edge visibly missing spots after cutting one onion (just a random example). I wasn't rock-chopping, and I use either a soft wood board or Hasegawa FSR. I deburr with leading edge strokes are a slightly higher angle, and I have checked using cork and wood (not every time I sharpen of course) that I got rid of it. None of my other knives do this, so I doubt it's technique.

Just double checked, so a bit of a correction. My "angle guide" I use for it is 21 degrees, so that's 42 inclusive. The "guide" is just a home made piece of wood for reference. I don't have the muscle memory for angles like that, and the feedback from the metal is mostly nonexistent.
I know the modern ones are even softer than the vintages, but this is extreme. Which brand?
 

noj

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On the handle, almost worn away, it looks like four stars and an elephant, and below that "Sabatier". Anything marked on the blade is gone. I don't think this is one of those fake Sabatier's (my parents had one, unfortunately).

The thing is very hard to sharpen, or at least you have to use very good technique. One little wobble, and the whole edge goes missing.
 

noj

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I don't recall details about purchase. I was working a summer job in a restaurant, and got one of what they had, and I liked using (or thought I did).
 
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