Thickness behind the edge

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krx927

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What do you say about the thickness behind the edge of my 210mm Akifusa gyuto?

Until now I was sharpening it on EdgePro and I have noticed quite some shoulder developing. As I recently switched to free hand I said I will try to thin it a bit. After that I was checking the thickness behind the edge and to me it still looks a bit thick. At least the majority of shoulder is gone now.

What do you say experts?

IMG_5594_crop_zpsqemgt4mv.jpg


IMG_5595_crop_zpssmyyw8dt.jpg
 
needs some thinning still...not the best pic, but this is a 240 Gesshin Kagero. I've thinned it a little bit, but it was much thinner than yours out of the box.

20150304_194006_zpspwnezrsq.jpg
 
I have a couple of knives that are are almost that thick that I like quite a bit. If you are happy with how it cuts for now take some time using it so you get to know the changes you are making to it. It can certainly get much thinner if you want to put in the time.

image.jpg
 
Sometimes long thinning sessions can be a PITA. If I were you I would just thin 20 minutes or so every time you sharpen. If you pay close attention, you'll be able to feel and see the differences in your cuts gradually overtime. Either way, if your thinning technique is decent enough keep putting in the work, the blade could cut better for sure.
 
The stage at which you want to stop thinning is up to you as the owner/user to answer, but that's hard to know if you've never done it before.

A great idea for your first thinning attempt is to get a cheap knife made from an easily grindable soft steel with a similar blade geometry to your Akifusa and try thinning that out first. Every so often during the process you can take a break and use the knife for food prep, feeling out how the behavior of the knife changes over time. Sure, it won't be exactly the same as when you start your proper attempt on your Akifusa, but you'll learn a hell of a lot in a much shorter time frame.

Also on a cheap knife it is safe to get really carried away and go overboard too. I did just this to see how a knife will handle past its 'optimal' thinness and into the realm of the anorexic laser. :biggrin:

3kkdMUn.jpg
 
Thanks for the answers. I had a feeling it is not yet thin enough.

Like you are mentioning it is pretty hard to judge if you have never done it before ;)

On the other hand, yesterday when I sharpened it, for the first time I was able to get a knife to hair whittling sharpness. I was really happy seeing that hair being cut in two :)

Can I ask you one other question about thinning: when I was checking Jon's thinning video he was doing it on a knife with pronounced secondary bevel, saying that thinning should be done only on this bevel. With a knife like this it is pretty easy to define the thinning area and hold correct angle. Unfortunately majority of my knives (Akifusa included) do not have a clear secondary bevel. In my thinning attempts I was holding such angle that I remove material approx. 1cm from edge:

Thinning_zpsmrrewy33.jpg


Should I also remove material higher up the blade using more flat angle when I grind?

In any case I will now use it a bit to see how it performs and will attempt thinning at some other time.
 
Kippington said:
The stage at which you want to stop thinning is up to you as the owner/user to answer, but that's hard to know if you've never done it before.

A great idea for your first thinning attempt is to get a cheap knife made from an easily grindable soft steel with a similar blade geometry to your Akifusa and try thinning that out first. Every so often during the process you can take a break and use the knife for food prep, feeling out how the behavior of the knife changes over time. Sure, it won't be exactly the same as when you start your proper attempt on your Akifusa, but you'll learn a hell of a lot in a much shorter time frame.

Also on a cheap knife it is safe to get really carried away and go overboard too. I did just this to see how a knife will handle past its 'optimal' thinness and into the realm of the anorexic laser. :biggrin:

3kkdMUn.jpg
Click to expand...

Kippington - that's a sweet looking grind. What's the knife?
 
Kippington said:
The stage at which you want to stop thinning is up to you as the owner/user to answer, but that's hard to know if you've never done it before.

A great idea for your first thinning attempt is to get a cheap knife made from an easily grindable soft steel with a similar blade geometry to your Akifusa and try thinning that out first. Every so often during the process you can take a break and use the knife for food prep, feeling out how the behavior of the knife changes over time. Sure, it won't be exactly the same as when you start your proper attempt on your Akifusa, but you'll learn a hell of a lot in a much shorter time frame.

Also on a cheap knife it is safe to get really carried away and go overboard too. I did just this to see how a knife will handle past its 'optimal' thinness and into the realm of the anorexic laser. :biggrin:

3kkdMUn.jpg
Click to expand...

WHOA!!! HOW DOES SHE CUT?
 
Your Akifusa is a bone-splitter at the moment. A $20 pair of verniers will tell you just how thick you are. .015"/.38mm is still thick enough for a work horse, I prefer >.010" for 99% of what I do.

Speaking of thinning cheap knives, I thinned some very soft stainless to about .008" and the other day I was cutting around some ribs with it, I didn't think I made much contact with bone but there appeared 2 sizeable dimples bent into the edge.


Rick
 
krx927 said:
Thanks for the answers. I had a feeling it is not yet thin enough.

Like you are mentioning it is pretty hard to judge if you have never done it before ;)

On the other hand, yesterday when I sharpened it, for the first time I was able to get a knife to hair whittling usharpness. I was really happy seeing that hair being cut in two :)

Can I ask you one other question about thinning: when I was checking Jon's thinning video he was doing it on a knife with pronounced secondary bevel, saying that thinning should be done only on this bevel. With a knife like this it is pretty easy to define the thinning area and hold correct angle. Unfortunately majority of my knives (Akifusa included) do not have a clear secondary bevel. In my thinning attempts I was holding such angle that I remove material approx. 1cm from edge:

Thinning_zpsmrrewy33.jpg


Should I also remove material higher up the blade using more flat angle when I grind?

In any case I will now use it a bit to see how it performs and will attempt thinning at some other time.
Click to expand...

I'm guessing that the original bevels (thinning bevels) were lost by using the EP? My Kagero had very easy to feel thinning bevels--just put the knife down and it told you where to thin. I believe you're on the right track and once you establish bevels this make it much easier to continue.
 
krx927 said:
...one other question about thinning: when I was checking Jon's thinning video he was doing it on a knife with pronounced secondary bevel, saying that thinning should be done only on this bevel. With a knife like this it is pretty easy to define the thinning area and hold correct angle. Unfortunately majority of my knives (Akifusa included) do not have a clear secondary bevel. In my thinning attempts I was holding such angle that I remove material approx. 1cm from edge:

Thinning_zpsmrrewy33.jpg


Should I also remove material higher up the blade using more flat angle when I grind?

In any case I will now use it a bit to see how it performs and will attempt thinning at some other time.
Click to expand...

Yes, try a shallower angle and thin at least the lower third of the blade.
 
I use a micrometer set to 25 thousands as a starting point and adjust from there. This video says most of what you need to know.
[video=youtube;WrCo4Vg2iiI]https://www.youtube.com/watch?v=WrCo4Vg2iiI[/video]
 
After some EP use blades become thicker behind the edge. Great edges, poor cutters. Not easy to correct at once. That's how I understand Rick's suggestion to thin up to a third of the blade's width. When properly sharpening from the beginning on, you should be all right when you start behind the bevel. I would suggest the lowest angle you can perform for the relief bevel.
 
Please be aware that after heavy thinning the edge may require a slight correction. With less steel behind the edge a higher sharpening angle may be necessary for edge stability.
 
Benuser said:
Please be aware that after heavy thinning the edge may require a slight correction. With less steel behind the edge a higher sharpening angle may be necessary for edge stability.
Click to expand...

I wouldn't think you'd need to use a higher angle. The stability of the edge itself, what's in front of where the primary bevel begins that is, is really not affected by what's behind it. If you took the thinning down to .001", it would be that .001" thickness causing the instability, not the primary bevel.

It should be understood that if your edge was 10deg inclusive there would be no need to thin behind that edge at all, unless you're going through a large gourd, which is unlikely what you'd use that edge for. I believe that is [true] single-bevel knife territory like usuba's. But at 20deg inclusive+ where we typically sharpen that is where I feel the thinning becomes noticeable.


Rick
 
rick alen said:
I wouldn't think you'd need to use a higher angle. The stability of the edge itself, what's in front of where the primary bevel begins that is, is really not affected by what's behind it. If you took the thinning down to .001", it would be that .001" thickness causing the instability, not the primary bevel.

It should be understood that if your edge was 10deg inclusive there would be no need to thin behind that edge at all, unless you're going through a large gourd, which is unlikely what you'd use that edge for. I believe that is [true] single-bevel knife territory like usuba's. But at 20deg inclusive+ where we typically sharpen that is where I feel the thinning becomes noticeable.
Click to expand...

I completely agree with this comment.

Mangelwurzel said:
Kippington - that's a sweet looking grind. What's the knife?
Click to expand...
420layersofdank said:
WHOA!!! HOW DOES SHE CUT?
Click to expand...

It's a re-profiled Richmond GT Artifex 210mm Wa-Gyuto, which I wouldn't suggest anyone buy unless they wanted something to experiment on.
Although, in her current state she cuts very nicely indeed! :biggrin:

PeJwWqh.jpg

boBmWbU.jpg


Sorry for slight thread derail.
 
I often wonder why people feel compelled to "thin the edge"? I often wonder if people know what they are doing?
 
:) you should see the number of knives that come to me after supposed thinning that look like battle axes
 
Salty dog said:
I often wonder why people feel compelled to "thin the edge"? I often wonder if people know what they are doing?
Click to expand...

That's a new expression to me! My first impression is that thinning the edge = sharpening.

So, what are people trying to (misguidedly) achieve when they attempt to ' thin the edge'?
 
It's not so much what they're trying to do, which carefully removing metal behind the edge to improve cutting performance. I've seen some knives that were pretty trashed from over aggressive or uneven attempts to do this without much regard to the original profile or actual goal in mind.
 
To salty and JBroida, I think I may have been totally misunderstood, and by the two people I look up to the most on this forum as well.

What I've tried to say in my previous posts is that the knife I've pictured has been an experiment; a cheap knife I didn't like that I sacrificed for a gain in skill and understanding. Much like how a bladesmith might test different heat treats on the same steel till destruction, I wanted to test how a blade would behave past it's 'ideal' thickness, and how that would translate into the kitchen.
It's been a great learning tool for me, hopefully bringing me one step closer to the level of your collective knowledge (this I don't actually know), and I was only suggesting to the OP to consider doing the same.

Or maybe I'm misunderstanding the situation myself - the last few posts have been very vague, and I've also had a pretty rough day at work (four steaks sent back tonight, all apparently undercooked).
 
Caution by Jon and Xoomg has gotten my attention. Originally, I thought..how can I thin a knife when I hardly feel or see the bevel. Then, I gave myself the opportunity
to practice on a Henckel...which wowed me. I still don't know if I was lucky or instinctively had a feel. Probably, something along the lines that one can't mess up an overly
thick behind the edge knife. Next, I thinned a nakiri that had a wonky grind. Again, when the knife is one down to begin with, I guess it's less likely that I can mess up.

In my head, I have had the assumption that the following precautions keep me in bounds: take pictures, study them, do a little ans re-examine...along the way use a sharpie and use a caliper.

As I upgrade my knives, time to not let some positive experiences go to my head. Then again, these are knives that I hope I only thin within the narrow definition of sharpening.
And, if I want to get aggressive time to revisit Jon's videos.
 
Kippington said:
To salty and JBroida, I think I may have been totally misunderstood, and by the two people I look up to the most on this forum as well.

What I've tried to say in my previous posts is that the knife I've pictured has been an experiment; a cheap knife I didn't like that I sacrificed for a gain in skill and understanding. Much like how a bladesmith might test different heat treats on the same steel till destruction, I wanted to test how a blade would behave past it's 'ideal' thickness, and how that would translate into the kitchen.
It's been a great learning tool for me, hopefully bringing me one step closer to the level of your collective knowledge (this I don't actually know), and I was only suggesting to the OP to consider doing the same.

Or maybe I'm misunderstanding the situation myself - the last few posts have been very vague, and I've also had a pretty rough day at work (four steaks sent back tonight, all apparently undercooked).
Click to expand...

my response was more to salty... i have a lot of people who send in knives for sharpening and they will say something like, "i've thinned this knife really well, so it just needs an edge put on it." Then, i look at the knife, and its thicker behind the edge than the first picture in this thread. Some people misunderstand thinning as simply knocking off the shoulders of a bevel. Or others than only thin about 1-2 mm above the edge, which has almost no impact on the thickness in the middle of the blade.

Anyways, my comment was not in response to anything you said, so no misunderstanding there.
 
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