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View Full Version : Why is this happening - sharpening ?



Ruso
07-30-2013, 11:23 PM
I was sharpening my petty and I got relatively nice and sharp edge. While I was doing the paper test I notices that at one point the knife gets stuck little bit, nothing much, but I decided to look under the pocket microscope. Here is the result - pics below. The knife was finished on 8K Imanishi stone with microbevel (the reflective part in last pic is the micro-bevel). This irregular pattern is about 1cm (0.4 inch) long. Other part of the bevel is smooth.
Does anybody knows what is this? And if it's "bad" how to avoid it in future?

Pics of the same spot more or less with diff lighting:

http://i.imgur.com/fbNQll2l.jpg (http://imgur.com/fbNQll2)

http://i.imgur.com/bk5nli2l.jpg (http://imgur.com/bk5nli2)

http://i.imgur.com/trnelATl.jpg (http://imgur.com/trnelAT)

tripleq
07-30-2013, 11:28 PM
Sorry I can't really tell much by the pics but have you considered it might be pieces of a wire edge still hanging around?

Dave Martell
07-30-2013, 11:31 PM
Two guess from me....

1. Edge damage that you didn't remove.

2. Burr or wire edge

Crothcipt
07-30-2013, 11:42 PM
Mini chips, you didn't see b4 and missed while sharpening. I hate it when I do that.

I would try to de burr just incase.

Ruso
07-30-2013, 11:44 PM
I would be surprised if it would be edge damage, still can be though. I did not see any visible chips (even small ones) and I went 2K-5K-8K-strop on balsa raising feelable burr on 2 and 5K stones.
As for the burr/wire edge that's more possible. I did not feel any with my fingers, it does not mean it is not there. What would be the best procedure to remove/avoid it? I usually strop on finishing stone and then naked leather or balsa.

Sorry for the quality of the pics; but I cant get any better - microscope is cheap and mobile phone camera not the best either :(

tripleq
07-30-2013, 11:57 PM
Some wire edges are extremely hard to remove. There are a bunch of options such as cutting into wood or cork. I personally find that stropping on felt is more effective at removing tough wire edges than leather.

tk59
07-31-2013, 01:04 AM
That looks pretty clearly to be chipping. Try it again. Make sure you get a burr and if you see the same damage, let us know. That said, if you really believe it's a burr, you can easily tell by flipping the burr to the side and inspecting the reflection. If the burr doesn't flip to the side, it's not really a burr. It's just a bad sharpening job.

DevinT
07-31-2013, 01:10 AM
What knife is it? What steel is the knife made out of?

Hoss

mkriggen
07-31-2013, 01:55 AM
Another thought is what angle (about) are you sharpening at? If you're sharpening at a real shallow angle you may be creating an edge that is too thin for the steel to handle. Had this same problem on my white #2 paring knife (micro-bevel didn't help). I raised the angle on the primary bevel just slightly (a degree or so) and the problem went away. Hope this helps.

Be well,
Mikey

JBroida
07-31-2013, 02:01 AM
i get the sense people seem to think that microbevels are a fix-it-all solution. I just want to say they are not. They arent really burr removal tools (though they do help remove burrs), and they arent always the best idea for every knife. They are a very good idea on some knives and in some situations.

chinacats
07-31-2013, 02:23 AM
i get the sense people seem to think that microbevels are a fix-it-all solution. I just want to say they are not. They arent really burr removal tools (though they do help remove burrs), and they arent always the best idea for every knife. They are a very good idea on some knives and in some situations.

Jon, could you please elaborate on "some knives and in some situations." Thin gyuto that gets banged on a board quite a bit I would think may apply?

kartman35
07-31-2013, 02:26 AM
Ok so I'm not any kind of expert, but to me, the most likely answer is those chips were there before the sharpening. I figure the fact that the OP only started with a 2k stone is a huge factor here.

Did you inspect that edge with the microscope prior to sharpening and after the 2k stone? My guess is that that the chips were there prior to sharpening, and the 2k raised a nice perceptible burr along the whole edge, but without removing the microchips that were there first. It takes me forever to get rid of any kind of chips with my Bester 1k and it raises a burr LONG before any chips are gone.

Its always a good idea to inspect the edge prior to sharpening with some kind of loupe, and then if there are any chips to be removed, make sure they're gone before progressing to finer grits.

Matus
07-31-2013, 02:46 AM
Well, I am not all too experienced, but if - as you said - this is a minor issue that you will likely not really notice in actual use, just use the knife as normally and when the next sharpening session will be due check the blade with your microscope before and after sharpening - maybe you will find similar micro chipping (if that's what this is) in more than just one place.

Rjgogue
07-31-2013, 02:46 AM
Jbroida,

What would you recommend on a Suisin Inox Honyaki Wa-Gyuto 240mm?? I have that knife due in the mail any day now and would greatly appreciate your advice on the optimal edge setup. And if I could take just a lil more of your time, would you recommend a microbevel on a Nenox Gyuto sharpened at an 80/20. These knives are used in a professional kitchen and never on plastic boards. Thank you in advance!

-Ray

mkriggen
07-31-2013, 03:20 AM
Jbroida,

What would you recommend on a Suisin Inox Honyaki Wa-Gyuto 240mm?? I have that knife due in the mail any day now and would greatly appreciate your advice on the optimal edge setup. And if I could take just a lil more of your time, would you recommend a microbevel on a Nenox Gyuto sharpened at an 80/20. These knives are used in a professional kitchen and never on plastic boards. Thank you in advance!

-Ray

:threadjacked:

JBroida
07-31-2013, 03:21 AM
ray, shoot me an e-mail or give me a call and we can let this thread get back to what it was

keithsaltydog
07-31-2013, 06:28 AM
Chiharu Sugai,Jon Broida,Dave Martell,Murray Carter all do as far as I know use the tech. of thinning behind the edge at a more shallow angle & then kick in a final bevel at a higher angle.There are diff. terms for basically the same thing I call it back bevel and final bevel.

The advantage as I think is not only gives the edge more durability,but also forms a more convex edge(two blended bevels)that is better than a machine ground wedge bevel that is found on many knives.From a Katana sword,Bone cleavers to a petty knife convex edges simply work.

If my thinking is too simple I am certainly open to other opinions on the matter:)

Ruso
07-31-2013, 10:28 AM
Thanks all for the ideas. I see that the common idea tend to be not removed chips. Yes i did not examine the blade with microscope so I will follow the advice to pay closer attention next time on this knife.

What knife is it? What steel is the knife made out of?

Hoss
This is Sakai Takayuki Grand Chef Petty in AEB-L



Another thought is what angle (about) are you sharpening at?
I would say about 10 degree per side. 50/50 grind.

JBroida, in this particular case I did not create microbevel to remove burr. Actually the blade was noticeable burr free once I decided to do it. The reason I decided to create one, was purely experimental to see how the knife behaves. And because based on your video it makes the edge more "stable" :D

stereo.pete
07-31-2013, 11:08 AM
10 degrees is crazy low if I understand you correctly.

Ruso
07-31-2013, 11:20 AM
Well may be 12. I do not have any angle measurement tool except old protractor form school days. But from my perception it was efficiently several degrees lower then 15 degree.

tk59
07-31-2013, 12:43 PM
10 degrees is crazy low if I understand you correctly.In my experience, most high end kitchen knife steels will produce a clean edge at 20 deg included angle. The issue is that edge may not hold during use for a variety of reasons.

tk59
07-31-2013, 12:46 PM
Another thought is what angle (about) are you sharpening at? If you're sharpening at a real shallow angle you may be creating an edge that is too thin for the steel to handle. Had this same problem on my white #2 paring knife (micro-bevel didn't help). I raised the angle on the primary bevel just slightly (a degree or so) and the problem went away. Hope this helps.

Be well,
MikeyIt doesn't make sense that a microbevel didn't help but adding a degree to your included angle did. Can you elaborate on how you produced the edge that didn't take the micro?

Dave Jacobson
07-31-2013, 02:11 PM
It could be that the martensite grain size in that area is not as small due to heat treating methods or it could of been overheated in that area causing the grain structure to grow.

panda
07-31-2013, 02:13 PM
the grand cheff line is ground 80/20, you should sharpen asymmetrically by the way. that knife doesnt have very good retention to begin with, youre better off not using a microbevel instead use frequent strop and ceramic honing rod.

mkriggen
07-31-2013, 02:29 PM
It doesn't make sense that a microbevel didn't help but adding a degree to your included angle did. Can you elaborate on how you produced the edge that didn't take the micro?

Only guessing here, but this is what I think happened. I originally sharpened the knife (Masakage Yuki 75mm petty) to about 10deg (20deg inc). This produced an edge that was too thin for the steel too handle and it actually started chipping while sharpening it. Adding a 20deg microbevel didn't help as the edge was still too thin to support it. When I backed off the primary angle a little bit the edge stabilized, stopped chipping, and took the microbevel just fine. Haven't had a problem since. Again, the analysis is my best guess, but the results are reality.

Ruso
07-31-2013, 06:40 PM
the grand cheff line is ground 80/20, you should sharpen asymmetrically by the way. that knife doesnt have very good retention to begin with, youre better off not using a microbevel instead use frequent strop and ceramic honing rod.

Interesting that you mention it. The page where I got the petty says that the grind is 50/50, when I received the knife the grin was about 80/20 as you are saying. I used it with uneven grind for some time, but I did not like it. I had to cut thing on slight angle, it was not too convincing for me. Now once I regrind it 50/50 - I like it much more.

Again, thanks all for pitching in on the ideas and info.

JBroida
07-31-2013, 07:18 PM
Only guessing here, but this is what I think happened. I originally sharpened the knife (Masakage Yuki 75mm petty) to about 10deg (20deg inc). This produced an edge that was too thin for the steel too handle and it actually started chipping while sharpening it. Adding a 20deg microbevel didn't help as the edge was still too thin to support it. When I backed off the primary angle a little bit the edge stabilized, stopped chipping, and took the microbevel just fine. Haven't had a problem since. Again, the analysis is my best guess, but the results are reality.

FWIW, i've sharpened a masakage yuki at 10 degrees and less without trouble... my guess is that something is going on with your technique that is causing this. Hard to know exactly what without seeing you sharpen, but the knife is capable of being sharpened in that way (though it may not be the idea edge for it)

mkriggen
07-31-2013, 07:30 PM
FWIW, i've sharpened a masakage yuki at 10 degrees and less without trouble... my guess is that something is going on with your technique that is causing this. Hard to know exactly what without seeing you sharpen, but the knife is capable of being sharpened in that way (though it may not be the idea edge for it)

:butbutbut:problem with my technique? No way!, I've been doing this for almost 6months, I'm sure I got it all figured out by now:rofl2:. Oh yeah, I'm sure my technique had a major effect, but backing off still worked for me until I get better at it:spin chair:

JBroida
07-31-2013, 07:54 PM
yeah... i wasnt trying to sound like a dick... just pointing out that it is possible to do that without chipping.

K-Fed
07-31-2013, 08:23 PM
If it makes you feel better, I don't usually have any sharpening troubles, but I struggled with the one grand cheff gyuto that I sharpened. The problem I was having looked almost identical to yours and to be honest I don't know that I ever found a solution. Serious wire edge troubles. I'm thinking bum heat treat as the steel felt gummy on the stones. Didn't like it at all.

mkriggen
07-31-2013, 10:31 PM
yeah... i wasnt trying to sound like a dick... just pointing out that it is possible to do that without chipping.

No problems Bro, didn't think you were. I just thought it was funny, and very true. I was just laughing at myself, not trying to be snippy or defensive.
:peace:

Be Well,
Mikey

Dave Martell
07-31-2013, 11:01 PM
So it appears like two issues here...

1. You damaged the edge. Maybe too shallow of an angle or whatever.

2. You didn't fix the damage when sharpening.


So you need to discover what caused the damage, how to not have it happen again, and how to fix it now that it has happened.

memorael
08-01-2013, 12:33 AM
I would be willing to pop some cash into the bin that you sharpened this knife before with some heavy low grit stone like a DMT XXC or something similar. When you apply to much pressure you create micro fissures which dont appear right away but are there, then after a few sharpening touch ups you end up with these cracks. Just re sharpen using lighter pressure on the low grit stone and or rework the edge using something that isnīt to aggressive. Sorry to drop the comment so late in the chat.:thumbsup: