# thinning questions (yet another thread)



## noj (Dec 4, 2022)

I have been reading a lot on this forum, and some of Jon’s (JKI) videos on thinning, and have some questions and observations. I only wish to discuss double bevel knives here. I have some, but limited experience thinning, and want to learn more before jumping to something more expensive, preferably before they need major thinning. A couple may need major thinning, mentioned below. I don’t have, or plan to have any motorized equipment. I am interested in maintenance thinning. Despite collectability, all knives will be put to work in the kitchen, and have to work well;-)

A. The first topic is about measurements and cutting observations.

A.1 Thickness behind edge (or 1 mm back)

I own a good micrometer. I don’t think I am capable of measuring the thickness behind the edge (or 1 mm behind) with any accuracy; there’s simply too much guesswork for me. That said, if I sharpen around 15 degrees, it turns out if your bevel is 1 mm deep, it’s 0.5 mm wide (and just behind the edge). That seems a lot more than some have recommended, and a 1 mm bevel doesn’t seem excessive after a handful of sharpenings.

A.2 Measurements (5 and 10 mm back), and knives that do and don’t cut well

First, I understand different knife makers, or styles, will have different geometries, and there’s no one right answer. I own a Konosuke FM I like a lot. I have two others that don’t cut well. One is a Mizuno which came new very thick and convex, and I haven’t sharpened it much. The other is a 15 year old famous maker (not going to mention here) I got used, I haven’t sharpened, and also a convex grind. Measurements (in mm) at midpoint follow:

Konosuke FM 0.6 1.0
Mizuno 1.2 1.7
15 year old 1.0 1.4

B. Recommendations for help thinning

I don’t think I am capable of thinning the two thick ones above. A lot of work, and too valuable to me to get wrong. Any suggestions? I would want someone that won’t change the makers character and geometry too much (like someone that doesn’t do convex bevels).

C. Maintenance thinning

C.1 Convex grinds
Jon’s (JKI) has a video on thinning wide bevel, but very little on thinning convex grinds. Any good threads or suggestions? I am having a hard time understanding how to comfortably and accurately maintaining a 5 degree angle, if that is an example of what’s required. There’s no obvious feedback like what one might get with a shinogi. I am looking for a lot of detail. Plus pitfalls I don't need to experience first hand;-)

C.2 Blade anomalies
I know there will be some. Low spots, high spots, etc. I am looking for the most common, and what to do with them. My guess is anything that gets to the cutting edge needs to be "fixed", less sure about the thinning area, and some are cosmetic (or will go away as the thinning progresses).

Thanks in advance, suggestions on this forum are always great!


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## tostadas (Dec 4, 2022)

noj said:


> A.1 Thickness behind edge (or 1 mm back)
> 
> I own a good micrometer. I don’t think I am capable of measuring the thickness behind the edge (or 1 mm behind) with any accuracy; there’s simply too much guesswork for me. That said, if I sharpen around 15 degrees, it turns out if your bevel is 1 mm deep, it’s 0.5 mm wide (and just behind the edge). That seems a lot more than some have recommended, and a 1 mm bevel doesn’t seem excessive after a handful of sharpenings.


This assumes that the blade thickness gets down to 0.0mm at the very tip, which is not the case. In reality, the thinnest part of the knife (at 0mm) still has measurable thickness when sharpened. Too thin and the steel will literally fall apart. 

Here are some measurements I posted in a separate thread that may be helpful to you.





Some experts' opinion for choil shot analysis, please


[TLDR]: Please take a look at the choil shots and tell me if I'm right in the assumption that the two gyutos are thicker behind the edge which changes their cutting feel. Hi guys, I wonder why two new knives I got don't exactly perform as I was expecting. Please note that this is not a...




www.kitchenknifeforums.com


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## noj (Dec 4, 2022)

tostadas said:


> This assumes that the blade thickness gets down to 0.0mm at the very tip, which is not the case. In reality, the thinnest part of the knife (at 0mm) still has measurable thickness when sharpened. Too thin and the steel will literally fall apart.
> 
> Here are some measurements I posted in a separate thread that may be helpful to you.
> 
> ...


I don't know how to get a measurement at 1 mm. It would be pure guesswork, I don't know or can't see whether it's .75 mm or 1.5 mm with a tool that had a 5 mm surface.

My calculation assumes the final bevel is 1 mm deep, and has a 15 degree angle. Yes, a tiny fraction may be rounded due to some natural convex-ing, but I don't imagine it affects the calculation.

 |\ <----- 14 deg
| \
| \
| \
+-----+
------> picture hard to draw with this editor, hope u can figure it out

The vertical line is the depth 1 mm. The horizontal ( +----+) is thickness behind edge (divided by 2) t2.
tan (14 deg) = t2/1 = t2 = .25, so thickness behind edge is 0.5. This is what was called "Distance behind edge at midpoint" in the referenced thread. This is the case anywhere the edge is ground flat. Obviously, this assumes your edge grind is at least 1 mm deep.

I don't understand the reference to the very tip.


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## HumbleHomeCook (Dec 4, 2022)

So, understand this is coming from someone with a fair bit but still limited experience and who is function-over-form oriented...

I don't measure. Maybe I should just to get a real understanding of measurements correlating to my experience but I don't and doubt I ever will.

I think a lot of people would be amazed how much of a difference even just mild easing and smoothing of the edge bevel shoulders can make. That's where I think everyone should start, just smoothing things up a little.

I just go and let the knife tell me how it's going. I've yet to work on a blade that didn't have variation along the length to at least some degree. That gets revealed pretty quick on a higher grit stone and can help guide you. This is especially true if you want to focus on aesthetics.

Anyway, I'm a big believer in the old adage that you can always take away, but you can never put back on so my thinning is generally slow and takes place over time and multiple sessions. Do a little, sharpen everything up and use it for a while.

How do I like it? Adjust and repeat.

I'm also not really great at closely replicating the maker's original grind. I mean, that can be pretty challenging with flat stones anyway. Sure, you can add in convexity and such but you're only ever gonna get so close. I do know there are folks on the forum that are very good at targeting and accomplishing very specific profile outcomes but I'm not one of them.

In other words, my advice is to not stress the technicals too much and let feel and experience guide you.


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## HumbleHomeCook (Dec 4, 2022)

Also, when I started getting more serious about exploring thinning, I immediately became a mono carbon or wrought-clad fan.


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## tostadas (Dec 4, 2022)

By "tip" i meant to say "edge." The thickness at the very edge is never going to be 0, but at the very least probably around 0.1mm

Here's a sketch based on actual measurements of one of my blades (the red line). As you can see, the thickness at 0 is not 0.0, actually closer to 0.2mm. In any case, the actual distance, whether it's 0.75mm, 1.5mm behind the edge is not that significant. What you will know is that it's thinner than the thickness @5mm, and thicker than @0mm. Essentially what I'm trying to get at is the thinnest point behind the edge that you can reasonably measure. Digital calipers with a small measuring surface are a more helpful tool here. But I think if you try to get the smallest non-zero measurement with your tool, it should be kinda close.


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## noj (Dec 4, 2022)

tostadas said:


> By "tip" i meant to say "edge." The thickness at the very edge is never going to be 0, but at the very least probably around 0.1mm
> 
> Here's a sketch based on actual measurements of one of my blades (the red line). As you can see, the thickness at 0 is not 0.0, actually closer to 0.2mm. In any case, the actual distance, whether it's 0.75mm, 1.5mm behind the edge is not that significant. What you will know is that it's thinner than the thickness @5mm, and thicker than @0mm. Essentially what I'm trying to get at is the thinnest point behind the edge that you can reasonably measure. Digital calipers with a small measuring surface are a more helpful tool here. But I think if you try to get the smallest non-zero measurement with your tool, it should be kinda close.
> View attachment 212299


I am afraid to measure anything like that for fear of breaking off a piece of metal. I only have a micrometer.

My argument though is about the thickness 1 mm back from the edge. The part I assume is zero is the final edge itself, which would be pretty un-sharp at 0.2 mm. I think your diagram doesn't include this final edge, but I could be wrong. My diagram was only of the very final edge, and not including the main bevel being thinned. I am not sure your diagram is depicting this, as the very last bit to the left should abruptly change from 5 degrees (or whatever) to 15 degrees (or whatever). My argument was only discussing that very last bit to the left, and based on my observation/guess that bevels are probably 1 mm wide after a few sharpenings.


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## tostadas (Dec 4, 2022)

noj said:


> I am afraid to measure anything like that for fear of breaking off a piece of metal. I only have a micrometer.
> 
> My argument though is about the thickness 1 mm back from the edge. The part I assume is zero is the final edge itself, which would be pretty un-sharp at 0.2 mm. I think your diagram doesn't include this final edge, but I could be wrong. My diagram was only of the very final edge, and not including the main bevel being thinned. I am not sure your diagram is depicting this, as the very last bit to the left should abruptly change from 5 degrees (or whatever) to 15 degrees (or whatever). My argument was only discussing that very last bit to the left, and based on my observation/guess that bevels are probably 1 mm wide after a few sharpenings.


It includes the final edge. It would be less than 0.2, but not by a lot, and certainly not 0.

edit: and clarification, the 0.2 was actually measured @1mm, so yea you can assume it kinda narrows down a bit to the edge. If you do the trig and assume a 12deg angle, that puts the thickness of the very edge approx 0.16mm


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## noj (Dec 4, 2022)

Sorry, I don't get it


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## tostadas (Dec 4, 2022)

noj said:


> Sorry, I don't get it


Just get one of these. Then no math needed.

iGaging IP54 Electronic Digital Caliper 0-6" Display Inch/Metric/Fractions Stainless Steel Body https://a.co/d/hdglITK


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## noj (Dec 4, 2022)

Better than a micrometer? I still have little confidence I could hit 1 mm back with much accuracy. My measurements at 5 and 10 mm may be enough to look at my other questions.


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## tostadas (Dec 4, 2022)

noj said:


> Better than a micrometer? I still have little confidence I could hit 1 mm back with much accuracy. My measurements at 5 and 10 mm may be enough to look at my other questions.


Yes, because you said that you are unable to get closer than 5mm accuracy with your micrometer that has a 5mm surface.

I think it's important to know what the edge is like on your blade before recommending some sort of thinning. But if you're looking for a general recommendation, the numbers in my table are how I categorize thickness behind the edge. So you can thin a bit, check your work, test some cuts, and maybe compare.

If the measurements you list for your thick knives are actually correct at 5mm and 10mm, they're incredibly thick. And any sort of thinning by definition will alter geometry. If you're concerned about that, then reach out to a professional, like Jon, and see if they're accepting work.

Jon has a video on hamaguri grinds. You might want to check that one out.

And I dont think you need to worry about low spots or anything at this point until you get to actual thinning and figure out what you're after. The high/low spots are more related to aesthetics than performance.


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## noj (Dec 4, 2022)

Here's the math with your geometry though. The acute angle is say 14 degrees. The middle vertical line is a model of your final edge. For sake of calculation, if the bevel edge is 0.1 mm, then it's (middle vertical line) is 0.05 mm. There is 1 mm of ground final edge at 14 degrees. The additional distance to zero (if there was metal there) is x. Half the width at 1 mm behind the edge is y.

x = .05/tan(14) = 0.2
y = (1 + 0.2 ) * tan(14) = 0.3

This yields a width 1 mm behind the edge of 0.6. 

The same calculation with a bevel edge of 0.2mm yields a width 1 mm back of 0.7.

The answer without the model of the bunted edge was 0.5.

So I acknowledge the interesting idea, but doesn't yield dramatically different results.


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## noj (Dec 4, 2022)

tostadas said:


> Yes, because you said that you are unable to get closer than 5mm accuracy with your micrometer that has a 5mm surface.
> 
> I think it's important to know what the edge is like on your blade before recommending some sort of thinning. But if you're looking for a general recommendation, the numbers in my table are how I categorize thickness behind the edge. So you can thin a bit, check your work, test some cuts, and maybe compare.
> 
> ...


Sorry what I said wasn't clear. What I was trying to say was the measuring heads of the micrometer are a 5 mm disks. The instrument is graded in 1 mil (1/1000 inch) or 0.0254 mm. The problem is my guessing where exactly 1 mm is by visual guesswork, imperfect kinesthetics, and not taking a piece out of my knife;-)

Oh, and thanks much for the rest of the comments. I think the measurements are pretty accurate. Those are easy when the instrument head is a 5 mm disk. I welcome a thinner geometry, I just didn't want someone to grind a convex blade dead flat.

I think those extra-thick ones are beyond me, but I'd still like to learn how to maintain my others. They are newer, and working fine, so I am in no hurry. I'd just like to get good at it before they need major work.


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## noj (Dec 4, 2022)

My micrometer. The black material on the ends of the disk are electrical tape I used to prevent scratches. Yes, I subtracted the extra width from the calculations, and re-checked that there was no measurable deformation (of the tape) at the end.


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## M1k3 (Dec 4, 2022)

HumbleHomeCook said:


> So, understand this is coming from someone with a fair bit but still limited experience and who is function-over-form oriented...
> 
> I don't measure. Maybe I should just to get a real understanding of measurements correlating to my experience but I don't and doubt I ever will.
> 
> ...


An example of taking care of those bevel shoulders.


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## noj (Dec 4, 2022)

M1k3 said:


> An example of taking care of those bevel shoulders.


A picture worth 1000 words, thanks!

On a convex grind, is that done with just finger pressure, or do you maintain some very low angle?


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## Nemo (Dec 4, 2022)

No need to measure. If your edge bevel is 1mm wide, thin until it is a hairs breadth thick.

You can even thin until you feel a burr "zero grind". Then put a new (and super narrow) 15 degree edge bevel on it.


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## M1k3 (Dec 4, 2022)

noj said:


> A picture worth 1000 words, thanks!
> 
> On a convex grind, is that done with just finger pressure, or do you maintain some very low angle?


I tried to barely lift the knife, while also placing my fingers near the edge. Where you put pressure makes a big difference in where you grind.


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## noj (Dec 4, 2022)

Nemo said:


> No need to measure. If your edge bevel is 1mm wide, thin until it is a hairs breadth thick.
> 
> You can even thin until you feel a burr "zero grind". Then put a new (and super narrow) 15 degree edge bevel on it.


I guess that is where I was sort of headed. If it's 1 mm, then just behind the bevel it's somewhere between 0.5 and 0.6 (0.7) mm, as long as the assumptions behind my calculations hold. How to tell if the edge is 1 mm not clear, again guessing, and hard to measure.


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## mengwong (Dec 4, 2022)

This is where a microscope complements the micrometer: here are mm rules at a certain magnification, and the edge at the same magnification.


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## mengwong (Dec 4, 2022)

Nemo said:


> You can even thin until you feel a burr "zero grind". Then put a new (and super narrow) 15 degree edge bevel on it.


When I read Tutorial on how to thin european knives I thought, that’s clever, setting the edge bevel _before_ the bulk of the thinning makes it less likely to run into deformation difficulties vs setting the edge bevel against a zero grind. In practice I do the latter, as you wrote


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## Nemo (Dec 5, 2022)

mengwong said:


> When I read Tutorial on how to thin european knives I thought, that’s clever, setting the edge bevel _before_ the bulk of the thinning makes it less likely to run into deformation difficulties vs setting the edge bevel against a zero grind. In practice I do the latter, as you wrote


I tend to go to a zero grind, then add a new edge bevel.

But.

1) I use the existing edge bevel to inform me about how my thinning is going.

2) I avoid using anything coarser than around 500 grit as I approach a zero grind (i.e.: once the original edge bevel is very small, I move up to 500 grit so that I don't reach the edge with anything coarser than 500).


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## M1k3 (Dec 5, 2022)

Nemo said:


> I tend to go to a zero grind, then add a new edge bevel.
> 
> But.
> 
> ...


Honest question. Why would you not using anything coarser than 500 grit on the edge?


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## Nemo (Dec 5, 2022)

M1k3 said:


> Honest question. Why would you not using anything coarser than 500 grit on the edge?


I guess it's a mostly theoretical concern of wasting steel refining that edge with a 500ish coarse stone (and I guess thus thickening the edge a little and undoing some of my good thinning work) before moving to a medium and fine stone.

Edited to add: As metioned in @ian 's subsequent post (#32), removing very much metal when creating a zero grind risks mucking up the profile.


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## Choppin (Dec 5, 2022)

Nemo said:


> I tend to go to a zero grind, then add a new edge bevel.
> 
> But.
> 
> ...


I do the same. I use the existing bevel as I guide, starting with a #200-220 stone, then when it's thin like a hair or two I move up to a #500 stone. A sharpie also works well. In my case I'm thinking I'll jump to a #500 in any case to remove the #200 scratches and must not forget it also removes metal, not only polishes... so I leave a little bit of "fat" there to be ground by following stones.

Learning from mistakes I guess. More than once I did all the thinning job on the #200 and forgot about the obvious fact that following stones, even if intended only for polishing, also remove metal (specially a 300 or 500). Then I ended up with thinner edges / behind the edge than I had planned.

Another mistake learned - be careful with the tip. Usually I work on it only slightly with the #200 stone (maybe 1/10 of the effort dedicated to the other areas) and leave most of the job for the #500 stone.


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## noj (Dec 5, 2022)

Thanks *everyone* for your posts; very helpful. I haven't started with the stones, yet. 

I did try to get some 1 mm measurements. While there is a big caveat about the accuracy of 1 mm, I took several measurements to perhaps offset the issue.

__________________ 1 mm, 5 mm, 10 mm
Konosuke FM____ 0.23, 0.6, 1.0
Mizuno___________ 0.5, 1.2, 1.7
15 year old_______ ??, 1.0, 1.4

On the 15 y/o I could not get consistent measurements. I had a closer look at the edge (not ever sharpened by me), and it looks very convex as well as wide. Someone couldn't hold an angle. Anyhow, the BTE and 5 mm measurements explain why my carrots kept exploding;-) 

I might need to get a junker knife to learn on. I have an old Sab I already thinned, but it's a pain because it bends (and stays bent easily). I also like it on the thick side because it's the softest metal I have seen. I have a junker I did some work on, but it's solid stainless and heavy, and was taking forever to thin, though I think I was he**-bent on removing low spots at the time for some reason.


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## noj (Dec 5, 2022)

mengwong said:


> This is where a microscope complements the micrometer: here are mm rules at a certain magnification, and the edge at the same magnification.
> View attachment 212388
> 
> View attachment 212391



Thanks for the idea. I could use something better than a magnifying glass for other reasons too. Last I looked, there were a dizzying number of microscopes on sale. Which one are you using, or perhaps more key is what are key features for this application? I imagine focus range, magnification (not including pure digital, which I can do easily later on computer), and pixel resolution.


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## Heckel7302 (Dec 5, 2022)

If you are looking for a practice knife, I really like Forgecraft for this. 









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For measuring 1mm behind the edge, I put a mark on my calipers at 1mm. Line up the edge with the mark and consistent 1mm measurement all along the edge. 

You’ll usually get the biggest performance benefit with thinning in the area just behind the edge. I usually take it down to 0.2-0.3 at a minimum.


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## Choppin (Dec 5, 2022)

Heckel7302 said:


> If you are looking for a practice knife, I really like Forgecraft for this.
> 
> 
> 
> ...


How is the grind on Forgecrafts? Convex or wide / flat bevel?

edit: sorry, totally off-topic


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## ian (Dec 5, 2022)

tostadas said:


> By "tip" i meant to say "edge." The thickness at the very edge is never going to be 0, but at the very least probably around 0.1mm



I think if your knife is .1mm at the actual edge, it will be really dull. Idk if the following is a razor or a knife, but 1 micrometer is a thousandth of a millimeter. The image is from Definitions of Sharp and Keen Anyway, I think @noj responded accurately.


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## ian (Dec 5, 2022)

noj said:


> I own a good micrometer. I don’t think I am capable of measuring the thickness behind the edge (or 1 mm behind) with any accuracy; there’s simply too much guesswork for me. That said, if I sharpen around 15 degrees, it turns out if your bevel is 1 mm deep, it’s 0.5 mm wide (and just behind the edge). That seems a lot more than some have recommended, and a 1 mm bevel doesn’t seem excessive after a handful of sharpenings.



Yea, you should maybe view the recommendations as guidelines for what to shoot for when you have a really tiny bevel. And sometimes the recommendations people give are like razor measurements....



noj said:


> First, I understand different knife makers, or styles, will have different geometries, and there’s no one right answer. I own a Konosuke FM I like a lot. I have two others that don’t cut well. One is a Mizuno which came new very thick and convex, and I haven’t sharpened it much. The other is a 15 year old famous maker (not going to mention here) I got used, I haven’t sharpened, and also a convex grind. Measurements (in mm) at midpoint follow:
> 
> Konosuke FM 0.6 1.0
> Mizuno 1.2 1.7
> 15 year old 1.0 1.4



I aim more for Kono FM thickness when I thin. Those other ones are chonky, although if you mostly cut soft stuff and find food release / indestructibility desirable, the thicker measurements could be good.



noj said:


> I don’t think I am capable of thinning the two thick ones above. A lot of work, and too valuable to me to get wrong. Any suggestions? I would want someone that won’t change the makers character and geometry too much (like someone that doesn’t do convex bevels).



Probably any of the reputable knife stores would do a good job. E.g. JKI, Strata Portland, Carbon Knife Co. I thought there was a new fancy knife store that opened up in Chicago, but can't remember the name. Anyway, I'm sure there's someone in Chicago that could do a good job. Maybe a local can weigh in. Or you can send them to @Runner_up or @Forty Ounce. 



noj said:


> Jon’s (JKI) has a video on thinning wide bevel, but very little on thinning convex grinds. Any good threads or suggestions? I am having a hard time understanding how to comfortably and accurately maintaining a 5 degree angle, if that is an example of what’s required. There’s no obvious feedback like what one might get with a shinogi. I am looking for a lot of detail. Plus pitfalls I don't need to experience first hand;-)



Don't try to maintain a 5 degree angle. That's impossible. Do it all with finger pressure. If you keep your fingers pretty near the edge, metal will tend to be removed right under your fingers. If you move your fingers back a little, you'll remove metal there. Look frequently at the scratch pattern on the underside of the knife to verify that you're removing metal in the correct place. Don't worry about getting it perfect. 10 to 1, the convex grind wasn't perfect to begin with. Imo, it's much easier (although very time consuming) to create uniform convex geometry on stones than it is on a belt grinder anyway, which is what most of the makers are using, so as long as you pay attention you probably won't ruin anything. That said, I wouldn't practice on a $500+ knife at first.



noj said:


> I know there will be some. Low spots, high spots, etc. I am looking for the most common, and what to do with them. My guess is anything that gets to the cutting edge needs to be "fixed", less sure about the thinning area, and some are cosmetic (or will go away as the thinning progresses).



Low/high spots that don't hit the edge are only an aesthetic problem, in that they make it hard to polish the knife evenly on bench stones. They will minimally impact performance, and may actually improve food release a bit. If you actually have a hole in the edge, then yea, you should thin/reprofile until the profile is fixed.


----

In general, @HumbleHomeCook's relaxed approach is good advice. I definitely found target measurements reassuring when I was starting out, though. Aiming for < .7mmish and < 1.2mm at the 5mm and 10mm mark will probably give you something that'll separate food reasonably well, and you can decide how to tweak them from there. Nowadays I never measure though. Btw, the nail flex test is an easy way to test thinness near the edge. If you want a thin edge that'll scream through produce, just take the blade and press the side of the edge on one of your fingernails. If the metal slightly bends at the contact point (you'll see that light reflects differently there), it's thin enough.

Maybe one additional recommendation: when thinning make sure not to f up the profile. The biggest mistakes I've made thinning have always been while thinning down to a zero grind, and then continuing to thin further. For instance, when you're working on the edge and thinning at the same time, the steel can bend from the pressure near the edge, effectively making you thin near the edge at something like a 0 degree angle, so that you end up creating part of the edge that's like aluminum foil. If you don't notice that you're doing that, you can end up with a couple mm of foil, which then breaks off, ruining your profile. I think it's a better idea in general to separating thinning and messing with the profile as much as possible. Try not to be creating a burr when you're thinning.



Choppin said:


> How is the grind on Forgecrafts? Convex or wide / flat bevel?
> 
> edit: sorry, totally off-topic



I think they're pretty flat on the blade road, but someone who owns an unmodified one can correct me.


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## Heckel7302 (Dec 5, 2022)

Choppin said:


> How is the grind on Forgecrafts? Convex or wide / flat bevel?
> 
> edit: sorry, totally off-topic


Pretty flat (at least after I thinned it), sort of a western wide bevel. Here is the choil on mine.


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## Heckel7302 (Dec 5, 2022)

ian said:


> I thought there was a new fancy knife store that opened up in Chicago, but can't remember the name.



Northside Cutlery






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## M1k3 (Dec 5, 2022)

Choppin said:


> How is the grind on Forgecrafts? Convex or wide / flat bevel?
> 
> edit: sorry, totally off-topic


Flat. Almost to flat.


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## noj (Dec 5, 2022)

I will catch up on all your generous comments in just a bit. I had an idea that seemed worth another bit of measuring and math. I got curious about how thin was in fact possible at 5 and 10 mm. Assuming you don't make it concave, the best case (for total thinness, not a good knife) is a V grind. I did the measurements somewhere in the upper middle, but well away from any heavy taper at the handle.
[SNIP] removed incorrect math, see below


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## ian (Dec 5, 2022)

noj said:


> _________________spine, height, 5 mm**, at 10 mm**
> Konosuke FM___ 2.2 mm, 47 mm, 0.5 mm, 1.0 mm
> Mizuno__________ 2.9 mm, 40 mm, 0.7 mm, 1.4 mm
> 15 year old______ 3.1 mm, 47 mm, 0.6 mm, 1.3 mm



What are these? Like you're saying what the measurements would be with the given spine width/height if you had a V grind? Those measurements seem a little large, no? I'd expect a full V grind to give you measurements that were like half of those. At least, naively, if I imagine a knife as a triangular wedge with base of length 47 and height 2.2, and look at the triangle with the same apex angle where the base is 5, the height should scale by the same ratio as the base, so since 47/5 is a bit less than 10, you should get something a bit bigger than 2.2/10=.22 mm for the 5mm cross section. Maybe I'm confused about something. Anyway, remember to use a microbevel! Otherwise your V ground Kono FM will have an apex angle of 2.8 degrees.


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## noj (Dec 5, 2022)

ian said:


> What are these? Like you're saying what the measurements would be with the given spine width/height if you had a V grind? Those measurements seem a little large, no? I'd expect a full V grind to give you measurements that were like half of those. At least, naively, if I imagine a knife as a triangular wedge with base of length 47 and height 2.2, and look at the triangle with the same apex angle where the base is 5, the height should scale by the same ratio as the base, so since 47/5 is a bit less than 10, you should get something a bit bigger than 2.2/10=.22 mm for the 5mm cross section. Maybe I'm confused about something. Anyway, remember to use a microbevel! Otherwise your V ground Kono FM will have an apex angle of 2.8 degrees.


Math done badly in my head, give me a sec;-)


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## noj (Dec 5, 2022)

noj said:


> Math done badly in my head, give me a sec;-)


I wasn't proposing doing a V grind at all. I was just curious how far from that it was. Corrected math below. Clearly, a lot of metal can be removed before getting close to the V-grind. I like the Konosuke the way it is! Thanks for the catch.

_________________spine, height, 5 mm**, at 10 mm**
Konosuke FM___ 2.2 mm, 47 mm, 0.24 mm, 0.48 mm
Mizuno__________ 2.9 mm, 40 mm, 0.36 mm, 0.7 mm
15 year old______ 3.1 mm, 47 mm, 0.33 mm, 0.7 mm


47/1.1 = 5/(t5/2) -> t5 = 0.24 (or about .22 as you said), and t10 = 0.48
40/1.45 = 5/(t5/2) -> t5 = 0.36 and t10 = 0.7
47/1.55 = 5/(t5/2) -> t5 = 0.33 and t10 = 0.7

** with V grind <-------------!!


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## Nemo (Dec 5, 2022)

ian said:


> Maybe one additional recommendation: when thinning make sure not to f up the profile. The biggest mistakes I've made thinning have always been while thinning down to a zero grind, and then continuing to thin further. For instance, when you're working on the edge and thinning at the same time, the steel can bend from the pressure near the edge, effectively making you thin near the edge at something like a 0 degree angle, so that you end up creating part of the edge that's like aluminum foil. If you don't notice that you're doing that, you can end up with a couple mm of foil, which then breaks off, ruining your profile. I think it's a better idea in general to separating thinning and messing with the profile as much as possible. Try not to be creating a burr when you're thinning.


This is important.

Creating a zero grind on a coarse stone will also risk mucking up the profile.

Maybe a good idea to stop just before this until you get a feel for it.


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## tostadas (Dec 5, 2022)

noj said:


> I wasn't proposing doing a V grind at all. I was just curious how far from that it was. Corrected math below. Clearly, a lot of metal can be removed before getting close to the V-grind. I like the Konosuke the way it is! Thanks for the catch.
> 
> _________________spine, height, 5 mm**, at 10 mm**
> Konosuke FM___ 2.2 mm, 47 mm, 0.24 mm, 0.48 mm
> ...


Just based on personal experience, the thinnest I've seen an edge at 5mm that's still able to hold is around 0.45mm. And that's really nail flexing already. If you go below that, very good chance your edge turns to foil and fails. Depends on the type steel and it's heat treatment for how thin you can get it. But if you get to that point, you will know.


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## noj (Dec 5, 2022)

tostadas said:


> Just based on personal experience, the thinnest I've seen an edge at 5mm that's still able to hold is around 0.45mm. And that's really nail flexing already. If you go below that, very good chance your edge turns to foil and fails. Depends on the type steel and it's heat treatment for how thin you can get it. But if you get to that point, you will know.


I have no intent to get that low, I was just curious what to compare various numbers against, though perhaps not that useful. Something in the ballpark of the Konosuke would suit my needs in terms of profile I like.


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## noj (Dec 5, 2022)

Heckel7302 said:


> If you are looking for a practice knife, I really like Forgecraft for this.
> 
> 
> 
> ...


Looks like the same maker is shown in the example above by @M1k3. Thanks, I'll have a look.


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## M1k3 (Dec 5, 2022)

noj said:


> Looks like the same maker is shown in the example above by @M1k3. Thanks, I'll have a look.


Yes it is.


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## Heckel7302 (Dec 5, 2022)

noj said:


> Looks like the same maker is shown in the example above by @M1k3. Thanks, I'll have a look.


I know it is, I sold it to him!  Or at least I assume it’s the Forgie I sold to him.


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## Heckel7302 (Dec 5, 2022)

M1k3 said:


> Flat. Almost to flat.


At least yours is because I thinned it flat. Though, if memory serves it was pretty flat to begin with.


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## noj (Dec 6, 2022)

ian said:


> I think if your knife is .1mm at the actual edge, it will be really dull. Idk if the following is a razor or a knife, but 1 micrometer is a thousandth of a millimeter. The image is from Definitions of Sharp and Keen Anyway, I think @noj responded accurately.


This is what I was trying to model with my original calculation (zero edge width). Keep in mind, what I was trying to estimate was the width behind the edge by inspection (vs caliper). Re-calculating with a "fat" edge was actually interesting, since the answer (for behind the edge width) is about the same, just a little larger. Unless I discover otherwise, my best estimate is width behind the edge is about 1/2 the width of the bevel. That assumes about a 15 degree, and reasonably flat final bevel. No warrantee for wobbly wrists.


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## noj (Dec 6, 2022)

ian said:


> Yea, you should maybe view the recommendations as guidelines for what to shoot for when you have a really tiny bevel. And sometimes the recommendations people give are like razor measurements....
> 
> 
> 
> ...


Thanks, lots of good info. The knife stores you mentioned are not accepting new work. Strata says they take mail-in, but when I called last, they said they didn't, and in any case it says they aren't doing complex stuff. Following up on other leads, but no luck yet.

I am glad it's a finger pressure method. I can't maintain a 5 degree angle either.

I did make yet another attempt on my full stainless beater. I used a 120 grit Shapton Pro and magic marker, and worked one side only. Well, the knife has about 5 low spots going to the edge, or pretty close. After an hour's work, it's still too thick, from the midpoint to heel, for the stone to get near the edge (maybe 1+ mm sharpie worth). I am guessing I need to change the geometry so as to be able to hit metal, based on finger pressure, from edge to 5+ mm above.

Perhaps a property of cheap stainless, but it started to polish vs abrade. I kept refreshing my Shapton on a silicon carbide plate (it's an 15" x 15" kiln shelf). The stone felt deglazed to my fingertips. Maybe the stainless is hardening due to deformation? I have to imagine a lot of hours/days of work. I mean practice;-) My only other low grit stones are a fast-dishing JKI 220, and a Shapton Pro 320.

Maybe I need a full carbon, or carbon clad? Forgecraft on ebay can get expensive for a practice knife. The ones in better condition were $100+. There are cheap Old Hickory ones. 

I'll keep your other recommendations in mind as I proceed.


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## Heckel7302 (Dec 6, 2022)

noj said:


> Thanks, lots of good info. The knife stores you mentioned are not accepting new work. Strata says they take mail-in, but when I called last, they said they didn't, and in any case it says they aren't doing complex stuff. Following up on other leads, but no luck yet.
> 
> I am glad it's a finger pressure method. I can't maintain a 5 degree angle either.
> 
> ...


You could try Ryan Swanson at District Cutlery. I think he is taking thinning work. 

That Forgecraft I linked I bet won't go for much more than the opening bid price. It looks in fine condition. Close to original profile is what you are looking for in vintage knives. A little rust is not a problem, cleans up easy. They are also just great knives. I used mine last night to make dinner, inspired by this thread. Reminded me how much I like it. 

That said, Old Hickory or Dexter (especially the 49A10H) will be fine for practice too. Vintage knives are exactly how I learned to thin and polish knives before taking the bevels of fancy Japanese knives to stones.


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## noj (Dec 6, 2022)

I'm getting myself a Forgecraft. Good practice, and I can whack a pumpkin with it later.


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## noj (Dec 8, 2022)

A couple more questions before I get my hands on the Forgecraft.

Do you generally do thinning all along the edge length?

Does it matter where you start (tip/heel/tbd)?

This may be harder to answer, but how should I be gauging the amount of metal removal along the edge (from tip to heel). I can imagine starting by rounding the shoulders to get a uniform and thin (or near zero) edge grind. I can imagine addressing what is going on above the edge (like 5 mm 10 mm) after, if needed.

If I need to do more than round shoulders, any guidance as to how to proceed? I understand the endgame is some combination of getting close to whatever measurements are desired, and ultimately does it work in the kitchen. I just don't yet have a clear method in my head about what to focus on.

I have seen blades that have an almost constant thickness 5 mm behind the edge. My Konosuke leans in this direction. Others are distinctly thinner towards the tip. I am guessing, just stick to the existing profile, at least until I get better at this.

Any additional details or corrections welcome.


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## Choppin (Dec 8, 2022)

noj said:


> A couple more questions before I get my hands on the Forgecraft.
> 
> Do you generally do thinning all along the edge length?
> 
> ...


I'm not the most experienced sharpener here, but a couple of things I learned in the process...

The most important IMO is asking where exactly can you thin to improve the knife's performance. Try it on some carrots and see how it performs. Do they crack right at the beginning of the cut, or near the end (when the edge is closer to the board)? The former might indicate it's thick BTE; the later could be an issue with the shoulders. Does it wedge / crack along the whole blade? It's usually better near the tip (so you thin less there). Like @stringer said - go slow, thin a bit here, test it on food, thin a bit there, test again...

I would be careful with the tip (the last 5cm or so). In my experience it needs much less thinning (about 1/10 of the effort or so) compared to the rest of the blade. That varies a lot from knife to knife of course. But I have overthinned more than one tip and ended up losing a few mm (in length and height). You usually only notice when it's too late.

Usually I start by smoothing the shoulders and thinning BTE. Lay the bevels flat on the stone and apply pressure near the edge. You'll end up thinning the whole bevel but focusing on the BTE area. Then tilt the knife a bit (so the spine is a bit closer to the stone), so you are hitting exactly at the shoulders, and then work there a bit. Thinning BTE - easing shoulders - moving shoulders up...


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## Heckel7302 (Dec 8, 2022)

noj said:


> A couple more questions before I get my hands on the Forgecraft.
> 
> Do you generally do thinning all along the edge length?
> 
> ...


Speaking to Forgecraft specificially (I've done two of them, so not an expert, but I've been there), they are made from flat stock, no distal taper, so the blade road has a pretty even thickness from heel to tip. 

It's probably going to need refinishing on the whole bevel. You can work it the way you would a wide bevel knife. Grind along the top of the bevel at the shinogi. Work up there will mostly be to even things out and take off any rust/piting. Then work with pressure close to the edge. You can introduce some convexivity here, or keep the bevels flat, up to you. You can lift the spine a degree or two to get more convexivity, or not. Work each side evenly.

Not sure what stones you'll be using, but in general this process is slow. Metal doesn't just fly off when thinning, it takes a long time.

When you are happy with the progress and want to make it look nice you can move up in grit on stones to remove the deeper scratches then move to wet/dry sandpaper to shine the bevels up. These are purported to be made of 1095 steel, one reason why they are so well regarded. It would be possible to get them looking good with stones alone, but I certainly didn't have the patience for that. Sandpaper makes it much easier.

For the faces, they can be cleaned up on (flat) stones, then sandpaper. I like to put the paper on a flat surface. It helps to keep things crisp. Some sanding of the handle may be required also. If so then again with the paper on a flat surface for sanding the sides of the scales as it keeps things even. Otherwise its pretty easy to grind more wood than the pins.


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## noj (Dec 8, 2022)

It seemed line Ian was suggesting finger pressure alone to adjust the location of metal removal, vs lifting spine, if I read that right. Or at least, one can't accurately hold a low angle, but maybe a little inaccuracy helps with the convexity. I have tried this a little (on a different knife), but don't have any conclusions, other than it doesn't seem like I have much control lifting the spine by guesswork.

For stones, I have a shapton pro 120, this one glazes over fast. I have a JKI 220 soft soaker, dishes fast. Finally, a shapton pro 320.

I have a Naniwa Chosera 400, but that's probably way too fine for gross metal removal.


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## Heckel7302 (Dec 8, 2022)

noj said:


> It seemed line Ian was suggesting finger pressure alone to adjust the location of metal removal, vs lifting spine, if I read that right. Or at least, one can't accurately hold a low angle, but maybe a little inaccuracy helps with the convexity. I have tried this a little (on a different knife), but don't have any conclusions, other than it doesn't seem like I have much control lifting the spine by guesswork.
> 
> For stones, I have a shapton pro 120, this one glazes over fast. I have a JKI 220 soft soaker, dishes fast. Finally, a shapton pro 320.
> 
> I have a Naniwa Chosera 400, but that's probably way too fine for gross metal removal.


Certainly the SP120 will be fastest, but the scratches are deep. I would probably start with the JKI 220 and see how it goes. Try to use all the stone to avoid excessive dishing. I try to make a conscious effort to NOT use the middle of the stone. Especially when thinning.

Yes, where you are putting pressure is where the metal will come off. My suggestion of lifting the spine, it's almost not lifting at all, more using the guiding hand to exert pressure toward the bevel and away from the spine.

Really, I think you just have to put steel to stone and figure it out through trial and error. Like sharpening its hard to put it all into words and there are a million different ways of attacking it. Experiment and find what works best for you and the knife you are working on. In the end the first go at it might not be perfect, but you'll learn a lot, and you aren't going to ruin the knife. 

This whole discussion is making me want to thin my Forgie a little more.


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## mengwong (Dec 8, 2022)

noj said:


> Last I looked, there were a dizzying number of microscopes on sale. Which one are you using, or perhaps more key is what are key features for this application? I imagine focus range, magnification (not including pure digital, which I can do easily later on computer), and pixel resolution.


Money no object: something from Dino-Lite. Probably want to talk to an informed dealer sales rep because the range is truly dizzying.

Slumming it: any of these China-made 720p-claiming-to-be-4K will disappoint you in expected, familiar ways. This is what I have.





This old video shows the difference between a cheap scope and a Dino-Lite. Skip forward to about the 7 or 8 minute mark.



And here’s a scope thread from a different forum. Microscope Test aka the Scope Showdown! – Wicked Edge Precision Knife Sharpener


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## noj (Dec 8, 2022)

mengwong said:


> Money no object: something from Dino-Lite. Probably want to talk to an informed dealer sales rep because the range is truly dizzying.
> 
> Slumming it: any of these China-made 720p-claiming-to-be-4K will disappoint you in expected, familiar ways. This is what I have.
> 
> ...



Thanks!


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## noj (Dec 8, 2022)

Well, a different (from the auction one) went for sale without a high price tag, so I snagged it.

I spent an hour in the on my 120 just cleaning up the bevel to see what I am dealing with. My 120 is slow, and seems to almost polish. I did a quick magic marker for the sake of photo. There are some low spots, but doesn't look too bad. The high spot right at the heel is annoying, but will go away eventually I hope. The other side has somewhat different issues, and seems similar in scope.

Pictures of one side below.


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## Heckel7302 (Dec 8, 2022)

noj said:


> Well, a different (from the auction one) went for sale without a high price tag, so I snagged it.
> 
> I spent an hour in the on my 120 just cleaning up the bevel to see what I am dealing with. My 120 is slow, and seems to almost polish. I did a quick magic marker for the sake of photo. There are some low spots, but doesn't look too bad. The high spot right at the heel is annoying, but will go away eventually I hope. The other side has somewhat different issues, and seems similar in scope.
> 
> ...


Nice. If it interests you, here is a good thread on some of the history on Forgecraft knives. The stamps changed a bit over the years they were made, you might be able to get a better idea of date on it.






History on Forgecraft knives; please educate me


I have a sudden interest in forgecraft knives and would like to know more about their history. I can remember them from when I was a kid. I think that they may have been sold at K-Mart and other retailers in the '70's. If I were a bettin' man I'd say they were made in Japan. The simplicity of...




www.kitchenknifeforums.com


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## Delat (Dec 9, 2022)

noj said:


> Well, a different (from the auction one) went for sale without a high price tag, so I snagged it.
> 
> I spent an hour in the on my 120 just cleaning up the bevel to see what I am dealing with. My 120 is slow, and seems to almost polish.



I’m definitely no expert, but IME when a low grit stone starts to polish it means it’s loaded up and needs cleaning. Sadly very frequent with low grit stones and why you see so many threads about low grit stones that don’t clog which usually end up with a recommendation for sandpaper.

My first go at thinning got tired of cleaning my loaded SG220, switched to an India and loaded that up, then said screw it and bought sandpaper. Next time I try thinning I need to pick up a kasfly.


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## noj (Dec 9, 2022)

Delat said:


> I’m definitely no expert, but IME when a low grit stone starts to polish it means it’s loaded up and needs cleaning. Sadly very frequent with low grit stones and why you see so many threads about low grit stones that don’t clog which usually end up with a recommendation for sandpaper.
> 
> My first go at thinning got tired of cleaning my loaded SG220, switched to an India and loaded that up, then said screw it and bought sandpaper. Next time I try thinning I need to pick up a kasfly.


For sure, it was loaded up. I made decent progress using a JKI 220 soaker. I must be getting better using the whole stone, because after and hour it hardly needed flattening. Then again, I haven't used it for quite some time, so maybe I learned something. I did grab the shapton 120 to at least clean off the embedded swarf and bevel the edges of the 220. Wow, that sure made a difference on the 120; it's rough with sparkly crystals again!


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## HumbleHomeCook (Dec 9, 2022)

Norton Crystolons can work well here.


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## stringer (Dec 9, 2022)

HumbleHomeCook said:


> Norton Crystolons can work well here.


One way to prevent loading is to add loose SiC grit while sharpening on a vitrified SiC stone. This will melt steel and your stone won't clog. But the scratches will be more like canals. But your knife will get thinner quick.


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## noj (Dec 9, 2022)

Thanks for the stone suggestions everyone. I seem to be making progress, but I will keep those in mind if needed.

Pondering my next steps, inputs welcome. I have the surfaces free of the worst stuff (3h work into it), but still have a low spot going to the edge. It's particularly annoying, near the center of the blade. I also found a few high/low spots on the edge vertically, so gently breadknife-d it so it was sharpen-able and I could see what the edge looks like. Sure enough, I had to breadknife more to get to metal in the low spot. The side profile is now decent. I can see the edge narrowing at the low spot, and a gentle ripple on the right side using light reflections. Pondering if I should thin that whole bevel flatter, maybe add some convexity, or something else. I am right handed, if it matters.


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## tostadas (Dec 9, 2022)

noj said:


> Thanks for the stone suggestions everyone. I seem to be making progress, but I will keep those in mind if needed.
> 
> Pondering my next steps, inputs welcome. I have the surfaces free of the worst stuff (3h work into it), but still have a low spot going to the edge. It's particularly annoying, near the center of the blade. I also found a few high/low spots on the edge vertically, so gently breadknife-d it so it was sharpen-able and I could see what the edge looks like. Sure enough, I had to breadknife more to get to metal in the low spot. The side profile is now decent. I can see the edge narrowing at the low spot, and a gentle ripple on the right side using light reflections. Pondering if I should thin that whole bevel flatter, maybe add some convexity, or something else. I am right handed, if it matters.



Sounds like good progress. Put a quick edge on the knife, test it and see what you think.


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## noj (Dec 9, 2022)

tostadas said:


> Sounds like good progress. Put a quick edge on the knife, test it and see what you think.


... heads back to kitchen .. ;-)


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## Delat (Dec 9, 2022)

Since math doesn’t lie, you got me curious enough to measure the length of some edge bevels. I’ve been calling my measurements at the base of the edge bevel 1mm out of convenience. Looks like my edge bevel lengths actually vary from .25mm to .6mm or thereabouts. 

Those yield a BTE thickness of .1 to .2 (I sharpen at 30 degrees inclusive). So yup, looks like many of us have been using the “1mm” reference as freehand notation for “immediately BTE”. Hollow-ground knives might be an exception though.


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## noj (Dec 11, 2022)

noj said:


> ... heads back to kitchen .. ;-)


Still way too many and bad low spots going to the edge. Going back to deal with that.

It's about 0.8 mm at 5 mm back. That measurement hasn't changed despite all the hours of grinding, though I can see the low spots shrinking. There's a bit more convexity than I want right near the edge. I felt it from the beginning as I moved my finger pressure. I guess the next step would be to back off a little from edge when applying pressure, and erase the low spots starting up high, and working towards the edge. 

As an aside, this has been the worst part of dealing with various (all?) knives. I would enjoy the knife maintenance more with a better starting point done by someone with better equipment and experience.

That Shapton 120 that was cleaned up is officially on my almost useless list. From the get go, it doesn't cut metal. Almost useless, because it's a good stone flattener for course grit stones.


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## noj (Dec 13, 2022)

Looking for more help. I have been spending an hour or two per day, and still have convex spots going to edge, and areas of excess thickness. My stones seem to do nothing. I ground off 1/4" of my JKI 220. My Shapton 120 is useless. I tried a cheap hardware store SiC (so-called course grit). I tried using the SiC to clean up the Shapton 120, and a mix of the SiC and Shapton slurry on the 120. I tried a diamond stone for a bit, and made a little (very little) progress. The joints in my fingers are painful from all the pressure. I can't measure any change in thickness at 5 mm. I don't know if I need vitrified SiC, I don't think Norton stones are, and I don't want to deal with oil. I spent an hour searching, and vitrified SiC aren't common, and most don't say what the grit size is. Can, or do I need loose SiC grit for Norton stones, or maybe to clean my Shapton 120, and what grit?


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## tostadas (Dec 13, 2022)

Have you tried sandpaper? 3m pro grade (the purple one at home depot) works well for fast metal removal. Get some 80,120,220 grits and put them on something flat (I put them on an atoma block) . I can get about 3 passes per side of the knife before the paper starts slowing down. Then toss it and use a new piece. If you really want to go fast, get the value packs of the lower grits and replace often.


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## noj (Dec 13, 2022)

tostadas said:


> Have you tried sandpaper? 3m pro grade (the purple one at home depot) works well for fast metal removal. Get some 80,120,220 grits and put them on something flat (I put them on an atoma block) . I can get about 3 passes per side of the knife before the paper starts slowing down. Then toss it and use a new piece. If you really want to go fast, get the value packs of the lower grits and replace often.


I haven't been to the hardware store yet; I'll give it a shot.


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## Nemo (Dec 13, 2022)

Using sandpaper has its downsides--

1) Feedback is pretty ordinary (not such a problem if you are thinning as long as you stop before reaching the edge).
2) Coarse grits feel terrible (this also applies to most very coarse stones, I guess).
3) The initial bite degrades after a dozen or so passes. It then seems to perform as a higher grit. On the upside, it will to an extent, refine its own scratch pattern. You can get around this by starting at a coarser than the grit you want to continue with. It will continue to remove metal at a slower rate for a couple of hundred passes. Overall, I find myself changing the paper no more often than flattening or refinishing a very coarse stone.
4) It can be difficult to hold it still enough to use with a lot of force. You could make a jig to hold it easily enough. Or buy a bespoke one. I use the Kasfly which is BY FAR my most used thinning and chip repair stone.
5) You can only use edge trailing strokes for sharpening the edge (thinning is OK until you reach a zero grind) unless your jig stretches the paper taught (as the kasfly does).


Sandpaper also has some significant benefits:
1) Choose your own grit.
2) It’s cheap and readily available.
3) 80 grit removes metal fairly fast. It's not magic, though. I spent several hours on 80 grit thinning a 12mm chip out of a friend's Kurosaki Shizuku.
4) Never needs flattening.

Overall, I find the benefits of sandpaper outweigh the problems below around 500 grit, at least in comparisonto a very coarse stone. Not that I have tried every super coarse stone out there but I have read a lot of reviews and opinions about the commonly avalable ones. The one very coarse stone that I am interested to try is the Debado 180 or 200.


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## noj (Dec 13, 2022)

Nemo said:


> 5) You can only use edge leading strokes for sharpening the edge (thinning is OK until you reach a zero grind) unless your jig stretches the paper taught (as the kasfly does).


Why only edge leading? I would have thought it dicey doing edge leading for sharpening the edge. At the moment I wasn't planning on using sandpaper for edge sharpening.


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## Nemo (Dec 13, 2022)

noj said:


> Why only edge leading? I would have thought it dicey doing edge leading for sharpening the edge. At the moment I wasn't planning on using sandpaper for edge sharpening.


Yeah, I meant to say edge trailing. I have edited the relevant post.


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## mengwong (Dec 13, 2022)

I was hoping that options for thinning could include a horizontal wet grinding wheel, but my hopes were dashed—


osakajoe said:


> The horizontal wheels are mostly for finishing the final edge or Koba. Not really designed for grinding away material. Some of the hobby cheap small horizontal machines like the Naniwa come with changeable stones. You can get a #400 grit stone for that machine but again not made to do the rough stock removal, just fixing edges and thinking behind the edge with the rough stones.


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## Infrared (Dec 14, 2022)

You can definitely thin with a horizontal grinding wheel. An hour or two of work on a stone can be achieved in 5 minutes on the wheel. And that's with the 1000 grit.


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## osakajoe (Dec 14, 2022)

mengwong said:


> I was hoping that options for thinning could include a horizontal wet grinding wheel, but my hopes were dashed—




There was a typo, thinking -> thinning 
So the rougher horizontal stones can do a small amount of thinning behind the edge.


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## noj (Dec 27, 2022)

I'll post some photos with my modest camera later. I removed all the deep groves from somebody's course belt sander, the bird's beak tip, most of the concave spots and bumps, a bit of frown, and general thinning. Breadknife thrice, albeit gently. At midpoint it's about .2-.25 mm behind edge, 0.8-0.85 mm at 5 mm, and 1.4 mm at 10 mm. I had a hard time getting it to zero edge, which was all for the best because of discovering more oddities as I went. I've sharpened it three times, and grinding chip-like stuff out of the edge bevel. Seems OK now, not as good as my regular knives .. yet.


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## noj (Dec 27, 2022)

I forgot to mention there's a bit of a bend to the whole blade left to fix. I see it, and think I can feel it on the stones. The rounded heel wasn't my addition. I polished it enough for you to see the convexity, nothing fancy.


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## Heckel7302 (Dec 27, 2022)

Unlocking that old Forgie’s true potential. Great work!


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## noj (Jan 5, 2023)

A couple questions ..

1. Any additional hints about thinning focused on the edge bevel shoulder? 
2. Similarly, if different from above, focused primarily in the 5 mm from the edge to produce a (near) zero grind?

I ask because I find it difficult to use finger pressure (and modest twisting) to get what I want. One problem is it's so very slow. I have used the recommended sandpaper (80*120 grit), and shapton 120. I can go for about an hour before my fingers hurt, or get slippery because of the embedded iron swarf. Even doing this daily for a week makes for seemingly slow progress. I'd rather not go courser because of the work to remove the scratches, and edge damage. As it stands, I am pretty sure I need to use finer paper/stone because I can see the remains of the edge bevel, but it's generating a burr. I suspect the grit is about as large as the remaining metal "gap" at the edge. If all this is "normal" let me know.

3. I made a knife straightener with a 2x4 and circular saw. I clamped the 2x4 to a rigid table. It holds the blade well, and is stable. With this knife, I wasn't able to perform any straightening. Unless I put by body weight into the force, it simply acted as a spring. I am reluctant to add more force because I am afraid of loosing control, and suddenly over bending or breaking. I'll probably just live with it the way it is. Thoughts?


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## noj (Jan 8, 2023)

I think I figured out the thinning issues. I just needed finer sandpaper (or stone) when there isn't much metal to remove.

I am seeing some peculiar behavior with the Forgecraft steel. My early attempts to sharpen it at ~14 degrees (per side) yielded an edge you could easily deflect and damage with a fingernail. This is not a wire edge, nor the wide bevel defecting. I ran the back of my fingernail along the entire flat(ish) section of the blade, and saw the edge bevel deflect and spring back. The wide bevel remained in place; it's not that thin. I re-sharpened it a couple times with the same result. I used a steeper angle, which helps, though maybe it needs some convex(ing) (or a micro-bevel).

After seeing the edge deflection, and difficulty straightening, I wonder if the metal is somehow close to a "spring steel".


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## The_Real_Self (Jan 8, 2023)

noj said:


> Still way too many and bad low spots going to the edge. Going back to deal with that.
> 
> It's about 0.8 mm at 5 mm back. That measurement hasn't changed despite all the hours of grinding, though I can see the low spots shrinking. There's a bit more convexity than I want right near the edge. I felt it from the beginning as I moved my finger pressure. I guess the next step would be to back off a little from edge when applying pressure, and erase the low spots starting up high, and working towards the edge.
> 
> ...



I can virtually guarantee you that Shapton 120 is heavily glazed as a freshly lapped and properly conditioned chunk of 120 grit abrasive should cut like an absolute demon. I mean to such a degree where if you do this to a Crystolon and use heavy force the steel comes off in chips that look like strips.

The Shapton's are known to have a very strong bond so they don't recondition themselves by spending grit rapidly. You would need something roughly 3x as course as the stone you're trying to condition in order to get the proper effect. The means you need the 24 grit Naniwa flattening stone from MTC.









Naniwa Sharpening Stone Fixer


Shop Japanese knives, knife sharpening stones, Japanese tableware, kitchenware, restaurant supplies and equipments, take out containers, sushi and ramen supplies




mtckitchen.com





On a budget you could also go with the Baryonix Manticore. I've used this in the past on my Sigma 120 and it works well enough but 24 grit would be a lot better from my experience.









BYXCO "Manticore" Bench Stone







www.baryonyxknife.com


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## noj (Jan 8, 2023)

The_Real_Self said:


> I can virtually guarantee you that Shapton 120 is heavily glazed as a freshly lapped and properly conditioned chunk of 120 grit abrasive should cut like an absolute demon. I mean to such a degree where if you do this to a Crystolon and use heavy force the steel comes off in chips that look like strips.
> 
> The Shapton's are known to have a very strong bond so they don't recondition themselves by spending grit rapidly. You would need something roughly 3x as course as the stone you're trying to condition in order to get the proper effect. The means you need the 24 grit Naniwa flattening stone from MTC.
> 
> ...


For sure it was glazed. I just didn't like that it took 5 minutes to glaze, and about the same time to clean. But now I have my concrete block.


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## The_Real_Self (Jan 8, 2023)

noj said:


> For sure it was glazed. I just didn't like that it took 5 minutes to glaze, and about the same time to clean. But now I have my concrete block.



I wouldn't expect a concrete block to be the best choice here as it probably won't leave as aggressive cutting surface on the stone. I do expect it's much better than it was but likely still not ideal. If it's glazing very rapidly then my initial thought is that you are using a steel that is too hard/wear resistant and it's not biting the steel well and/or you are using very light force. 

By grinding simpler/softer steels on smaller contact surfaces you can often keep a stone cutting or refresh the surface without lapping. Simply increasing the force applied will also have a similar effect of increasing grinding pressure to release abrasive. That said, I don't feel that 5 minutes is necessarily unacceptable if it got a lot of work done and you can recondition/lap easily.


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## noj (Jan 8, 2023)

The_Real_Self said:


> I wouldn't expect a concrete block to be the best choice here as it probably won't leave as aggressive cutting surface on the stone. I do expect it's much better than it was but likely still not ideal. If it's glazing very rapidly then my initial thought is that you are using a steel that is too hard/wear resistant and it's not biting the steel well and/or you are using very light force.
> 
> By grinding simpler/softer steels on smaller contact surfaces you can often keep a stone cutting or refresh the surface without lapping. Simply increasing the force applied will also have a similar effect of increasing grinding pressure to release abrasive. That said, I don't feel that 5 minutes is necessarily unacceptable if it got a lot of work done and you can recondition/lap easily.


All work was thinning/fixing soft iron (and whatever blue/white core was involved), plus the Forgecraft. Tried once on stainless, but wasn't different. Pressure didn't help. It was more like 5 minutes until it started polishing, and in the mean time wasn't even producing swarf. The only time I have seen it do anything was after the concrete. I have tried a couple silicon carbide products, however not the ones you and other mentioned, to no avail. I'd be more inclined to try a better course stone, or just use sandpaper.


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## The_Real_Self (Jan 8, 2023)

Were you trying to thin the entire bevel of trying to add new bevels to create a multifaceted bevel similar to convex? Trying to plane down an entire wide bevel without convex or concave will equal very low grinding contact pressures even as force increases. You really need a softer stone for this sort of thing, I'd bet that stone would be incredibly happy to remove damage from a narrow edge bevel in short order without excessive wear.


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## noj (Jan 8, 2023)

The_Real_Self said:


> Were you trying to thin the entire bevel of trying to add new bevels to create a multifaceted bevel similar to convex? Trying to plane down an entire wide bevel without convex or concave will equal very low grinding contact pressures even as force increases. You really need a softer stone for this sort of thing, I'd bet that stone would be incredibly happy to remove damage from a narrow edge bevel in short order without excessive wear.


As I mentioned above, the work involved several operations. I removed all the deep groves from somebody's course belt sander, a bird's beak tip, several concave spots and bumps, a bit of frown, and widened the shinogi near the tip. After that, I did thinning using finger pressure to focus on the 5 mm nearest the edge, and blended that in to make it convex. I have tried to use this stone for similar operations on other knives, and it never worked well. It was so bad, I didn't use it much. I spent most of my time on a JKI 220. It's very soft, but removed metal so slowly, I used up maybe 1/4 inch of it, and looked for something else. Sandpaper got me going again, mostly. I must have spent 10 hours using the 80 grit sandpaper. The Shapton 120 does make a decent flattening stone for some course stones.


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## noj (Monday at 4:00 PM)

The_Real_Self said:


> Were you trying to thin the entire bevel of trying to add new bevels to create a multifaceted bevel similar to convex? Trying to plane down an entire wide bevel without convex or concave will equal very low grinding contact pressures even as force increases. You really need a softer stone for this sort of thing, I'd bet that stone would be incredibly happy to remove damage from a narrow edge bevel in short order without excessive wear.


In case it wasn't clear, and sounded grumpy, I was disappointed in the stone, not your helpful replies!


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