Knife Edge Miyabi 7000D

On my Miyabi 7000 D Gyuto I have sharpened this down to a 12K Naniwa Green stone Superstone. I really like this stone for the final stage just before I strop. Usually I don't go down below a 1K stone, with a 3K in between as this knife is pretty fairly new and this is only home use. But here is the problem:

1. After sharpening, deburing, etc I have a nice razor sharp edge. Pretty much the same as all my knives including the 7000MCD. Although at this time I don't have the MCD or I would likely be using this. After the 3K stone usually the knife is more than ready to go, but I like that mirror finish

Where the problem seems to be is after cutting for a few short time (home use) that I seem to loose the edge, or at least I think I am. My technique is more slicing than dicing/shopping, and I am fairly easy on my blades, but by the time I get say 3 veggies in if I cut a tomato it is simply not just sliding through. Same thing with some peppers, and various others. If I clean, give a light strop its all back to the original edge, and sometimes just a slight cleaning and wiping fixes this also.

2. On close look I can't see any chipping, edge loss, etc, so I am a bit baffled on this. None of my cheaper carbon blades even seem to have this problem so I am a bit stumped on what is going on and what to address.

I should add that I tend to wipe clean the blade often with both a damp and dry cloth, and often I use a slight drop of water down the edge to help with slicing.

p.s. Please excuse my chopping sentence structure as I just woke and coffee is barely effecting me and I believe I am feeling some of yesterdays hill climbing on the bike taking over, and feeling a bit underwhelmed by this knife.

Guten Morgen

Guten morgen mein Freund ! Es ist abend here in Australia .
Miyabi 7000d uses vg-10 steel , IMHO it has a better heat treatment than some other mass production knives. With my vg-10 knives I had , highest grit stone I have used was 3000 on my Hattori FH suji. Especially for a Gyuto I would prefer little toothy edge around 2-4 k , i am not sure if that blade can maintain 12k edge on it

Sounds like a wire edge to me, but let someone with more experience confirm my observation.

I've got a 600 D, also made of VG10, and usually take it up to a 10K Chosera. No issues at all. The blade really likes that 10K finish, and the mirror finish sure looks great. But saying that, I do microbevels. Just a few stropping moves on the 10K at a 30-40 deg angle does wonders to edge retention.

Arrg, Typed out a reply then it logged me out. *sigh*

Anyways what I said is it is VG-10.
Even if I only go to a 3K stone similar results. I should also mention I never took the blade down to a more aggressive angle or anything, and not sure it could take it, considering the issue.

I do agree it is harder than many VG10 knives I have tried in the past and to the best of my eyes and glasses, magnification I can not see a wire edge. If a wire edge comes up on a straight razor I can see that so I am not sure if it is the same. I do micro bevel also.

DerSnap said:

On my Miyabi 7000 D Gyuto I have sharpened this down to a 12K Naniwa Green stone Superstone. I really like this stone for the final stage just before I strop. Usually I don't go down below a 1K stone, with a 3K in between as this knife is pretty fairly new and this is only home use. But here is the problem:

1. After sharpening, deburing, etc I have a nice razor sharp edge. Pretty much the same as all my knives including the 7000MCD. Although at this time I don't have the MCD or I would likely be using this. After the 3K stone usually the knife is more than ready to go, but I like that mirror finish

Where the problem seems to be is after cutting for a few short time (home use) that I seem to loose the edge, or at least I think I am. My technique is more slicing than dicing/shopping, and I am fairly easy on my blades, but by the time I get say 3 veggies in if I cut a tomato it is simply not just sliding through. Same thing with some peppers, and various others. If I clean, give a light strop its all back to the original edge, and sometimes just a slight cleaning and wiping fixes this also.

Guten Morgen

Click to expand...

try...

a) after the 1000 grit jump to your 12K. shouldnt take too many strokes , I reckon not more than 10 per side to get the desired mirror shine and that shld do it

b)after 1000 grit, same priciple as above.. once you get the change of color/ shine for that particular stone ... and off , progress to the next higher grit as desired.

once you over polish with a higher grit stone.. you sort of remove the striations of the previous grit. Bigger striations takes longer time to wear off

have fun,,,,
d

Your cutting board may be destroying a highly refined edge like that.

Its a bamboo type board?

I am pretty light on the board and don't really do much if any rocking type cuts.

Bamboo is pretty hard stuff. Might be fine for thicker knives but if you're messing with sub 15 degree bevels, the board might be rolling your edge prematurely. I'f couse I'm just conjecting, but when i shifted from my Pro Teak boards to a cherry/walnut end grain, my edges lasted a lot longer. There even synthetic materials out there that are even more gentle than wood.

DerSnap said:

Its a bamboo type board?

I am pretty light on the board and don't really do much if any rocking type cuts.

Click to expand...

I agree w/ flyingpigg, that few # of cuts and i can't think it's anything but a wire edge...just to be clear is the finisher 12000 or 1200? If actually 12000 then it is likely just way too refined. I need coffee...

chinacats said:

I agree w/ flyingpigg, that few # of cuts and i can't think it's anything but a wire edge...just to be clear is the finisher 12000 or 1200? If actually 12000 then it is likely just way too refined. I need coffee...

Click to expand...

12000 not 1200.
Like I said funny as my cheaper knives never have problems with this stone, and more aggressive angles. I used them to practice before.

Mucho Bocho said:

Bamboo is pretty hard stuff. Might be fine for thicker knives but if you're messing with sub 15 degree bevels, the board might be rolling your edge prematurely. I'f couse I'm just conjecting, but when i shifted from my Pro Teak boards to a cherry/walnut end grain, my edges lasted a lot longer. There even synthetic materials out there that are even more gentle than wood.

Click to expand...

That's very good to know! I use a ProTeak myself that I've sanded and condition regularly -- is it really that hard on the edges? I don't do a lot of heavy-handed chopping, personally -- I usually do push or pull cuts.

So I did some deeper looking into this on my day off yesterday.

To the best of how close I could look, and magnify I could see not rolling or wire edge. I did this because I noticed what looked like some micro-chipping but that ended up being just some slight water markings against the shine of the mirror polish. I would have been shocked if there was chipping, and relieved there wasn't any.

Slicing away I came to an interesting observation. If I cut say some tomato's then I notice it not slipping through I can just give it a slight run under water, and wipe the blade again. The strange part is I tend to wipe and clean pretty often just because of my carbon blade habit. I am ruling out the board for now also because of this finding. Anyone think this knife could just be overly sensitive to build up?

OH also I made a mistake I am not using 12K stone but rather a 10K Green Super. I think I said 12K originally, but I doubt 10vs 12K is any different?

Cheers,
shamus

10k is simply too high for a vg gyuto. The 10k superstone you speak of is favored for it's high polish abilities with single bevel carbons. The superstone series in general is very soft, creating very fine and polished edges. Your lack of ability to cut a tomato is from the lack of toothiness. Maybe check out a different stone, from a different series, in the 4-6k range. You can still polish on the 10k, but drop back down to the new stone for a few passes to give you that lasting toothy edge.

An over-polished edge should still push-cut paper, right? That would be a good test for the OP to conduct. Slippery on tomato + push cuts paper easily = over-polished.

perneto said:

An over-polished edge should still push-cut paper, right? That would be a good test for the OP to conduct. Slippery on tomato + push cuts paper easily = over-polished.

Click to expand...

Cuts paper easy, Cuts red guy easy at first.
I will experiment with 6K also I have that and 3K also.

Either some of the burr is hanging around, or you're over-polishing. You can bet it's the latter, but the former does this as well. You can get a nice mirrored look with a 6k (or so), and it'll have enough tooth to cut food properly. Out of curiosity, are you stropping with any compound? If you are a stropping addict (sounds like you're a razor guy), switching from chrom-ox to diamond will give a more aggressive edge, as well. I basically won't shave with a diamond loaded stropped edge, because it doesn't glide the same.

Also, just for fun, I'm going to add this: I bet you finish your sharpening with either a heel to tip strop, or full heel to tip pull or ten over the stones. If you're a slicer, this will make the edge feel less impressive; Try going tip to heel.

And, oh yeah - stop at 6k....

Lefty said:

Also, just for fun, I'm going to add this: I bet you finish your sharpening with either a heel to tip strop, or full heel to tip pull or ten over the stones. If you're a slicer, this will make the edge feel less impressive; Try going tip to heel.

And, oh yeah - stop at 6k....

Click to expand...

Tom, never thought of this! Thanks I'll have to give it a try myself just to see the difference--I don't believe I've ever seen that mentioned.

Cheers

@lefty: Ya a razor guy I have different strops but usually I am not a big fan of paste(s). I do use them on occasion though.

We will see what happens at 6K. I will say I find this a bit disheartening as I can take a 80 Euro Carbon Japanese knife, hell a 20 euro one and hold an edge better with a higher stone polish. But I am here to listen and learn and try and figure this one out.

DerSnap said:

@lefty: Ya a razor guy I have different strops but usually I am not a big fan of paste(s). I do use them on occasion though.

We will see what happens at 6K. I will say I find this a bit disheartening as I can take a 80 Euro Carbon Japanese knife, hell a 20 euro one and hold an edge better with a higher stone polish. But I am here to listen and learn and try and figure this one out.

Click to expand...

If you can do that with cheap carbon leads me back into believing you may be suffering a wire on this knife.

It could be wire edge, but I can't see it with my glasses on, but I maybe a better magnification.
On a Straight razor its not too hard to see a wire edge, but I have not had one in over 20 years. But hey, first time for everything right?

I don't know if I mentioned when I use the very fine stones I am only honing lightly on them. "If" this is the problem then how come stoping is not the same issue?

Sorry if I ask a lot of questions, but that is the way I learn.

Cheers, I think its time to crash.

Guten Nacht Alles!

I understand stropping can tear away at any residual burr, whereas fine stones will just add to it.
Have you considered micro-bevels? http://www.youtube.com/watch?v=xwnFrjiAA_8&feature=c4-overview-vl&list=PLEBF55079F53216AB

So woke up this morning to a nice sunny kitchen. Fresh eyes also.
Looked a bit closer and I am pretty sure there could be a slight wire edge. It is pretty hard to see, but I suspect its there. I do micro bevel so its right at that edge of my eye focus.

I also noticed on the left side of the blade which is at a slightly different angle do to the design that it is also just a touch thick in spots.
Absolutely no chips or anything though.

Also I suppose the reason it is harder to see on a knife over a straight razor is just the very thin thin thin edge a razor has.
Man I must be getting old as 10 years ago I could see those details easily.....

DerSnap said:

Man I must be getting old as 10 years ago I could see those details easily.....

Click to expand...

Welcome to the club!

On a side note why didn't Miyabi ever make a 240mm in the 7000 MCD line. I have to say although I don't have that knife here anymore since I left Canada I really liked it. Can't recall any of these issues. Perhaps it was they eye site though

perneto said:

I understand stropping can tear away at any residual burr, whereas fine stones will just add to it.

Click to expand...

With good technique fine stones will abrade residual burr, and with poor technique stropping may add a lot of new burr.

That's interesting, could you give us more details about good and bad technique?

Your very general statement:

perneto said:

I understand stropping can tear away at any residual burr, whereas fine stones will just add to it.

Click to expand...

In general, fine stones may or may not add burrs, just as strops, by the way. If you apply a very light pressure, your motion is strictly along the edge -- not edge leading nor trailing -- and the angle perhaps a very little higher, you may very well clean up the edge on your finest stone without creating any new burr. Verify with your nail going along the edge.
Now about the other part of your statement: as far as I'm capable of understanding it correctly, I sure do believe stropping may remove burr remainings. But done improperly, e.g. at an inadequate angle or with too much pressure, may under circumstances round an edge, create a wire edge or even a full burr.
So it isn't so much about the medium, it's more about the technique adapted to the specific medium.

your motion is strictly along the edge -- not edge leading nor trailing --

Click to expand...

What kind of motion do u refer to? Strictly perpendicular to the to the stone in a straight line?

It's along the edge. I don't want to flip the burr anymore is this final stage. Don't try this on leather, you would damage it.