PDA

View Full Version : Overgrind Into The Edge



Dave Martell
04-24-2012, 01:26 AM
I just stumbled upon an old picture that I shot of a brand new knife that came in for sharpening years ago. I began sharpening the knife but a problem quickly arose that got worse and worse. I think this image clearly shows the irreparable condition of a blade overgrind....


http://img.photobucket.com/albums/v438/dmart/P1010051.jpg

Andrew H
04-24-2012, 01:29 AM
Nice picture, thanks!

Dave Martell
04-24-2012, 01:38 AM
I forgot to mention that this was one of the first knives that I got burnt on trying to fix the overgrind. Yeah there's nothing like buying someone a new knife all because someone else screwed the pooch.
:angry2:

GlassEye
04-24-2012, 01:38 AM
Thanks for the image and explanation. My CCK looks like this in a few spots, it is getting annoying.

Dave Martell
04-24-2012, 01:40 AM
Thanks for the image and explanation. My CCK looks like this in a few spots, it is getting annoying.


You might get lucky and see it disappear as you sharpen over time. I say that because CCK's have hammer marks near the edge more so than overgrinds. Still though, an errant hammer blow can show the same irreparable condition too, you never know.

Don Nguyen
04-24-2012, 02:15 AM
Is there any way to check for this? How much does it affect the performance?

memorael
04-24-2012, 03:07 AM
Hey Dave, in order to "fix" this couldn't you just thin the knife a lot? in the case of the knife being a mono steel? That is however totally changing the knife but its the only thing that comes to mind in order to "fix" it.

l r harner
04-24-2012, 09:57 AM
wqas ging to say i woudl jsut grind it thinner till it was again even

Lefty
04-24-2012, 11:04 AM
Or shorten the blade, from edge to spine, until you're past the overgrind. In the case of the CCK, the blade height would allow this more readily, of course.

Dave Martell
04-24-2012, 11:18 AM
I tried the thinning method here because it looked straight forward but as I approached the edge bevel the hole opened up huge and the edge started to disappear thus I got screwed. On the surface that method seems like the way to go but 9 out of 10 times it doesn't work unless you can figure out a way to keep the belt from touching the overground section while doing the thinning to the rest of the knife. I realize that this is hard to accept but when you see it first hand it can't be denied.

Lefty
04-24-2012, 11:25 AM
Makes sense to me, Dave. :D

mikemac
04-24-2012, 11:35 AM
...And the CCK is a $40 +/- mass produced rustic blade from a developing nation....rational expectations and all.



You might get lucky and see it disappear as you sharpen over time. I say that because CCK's have hammer marks near the edge more so than overgrinds. Still though, an errant hammer blow can show the same irreparable condition too, you never know.

memorael
04-24-2012, 11:42 AM
O I get it, its hard to grind everything except the hole... damn hope I don't get a lemon ever.

Sarge
04-24-2012, 11:56 AM
For you Dave it probably isn't worth the time and effort but if at home someone were to thin by hand on stones, wouldn't it be possible to avoid creating a massive hole?

heirkb
04-24-2012, 11:58 AM
For you Dave it probably isn't worth the time and effort but if at home someone were to thin by hand on stones, wouldn't it be possible to avoid creating a massive hole?

That's what I was wondering. Thinning on something like a diamond plate perhaps.

Dave Martell
04-24-2012, 12:02 PM
For you Dave it probably isn't worth the time and effort but if at home someone were to thin by hand on stones, wouldn't it be possible to avoid creating a massive hole?


That's possible, I'll never say never

TB_London
04-24-2012, 01:24 PM
I keep thinking about this, for simplicity assuming a 50/50 grind and a 50/50 edge, if the hole doesn't go past the centre of the thickness of the blade, would you still be able to have an unaffected edge, other than it being thinner behind that part? I thought the problems came when the hole crossed the centre of the blade and interfered with the edge.

Eamon Burke
04-24-2012, 01:41 PM
I keep thinking about this, for simplicity assuming a 50/50 grind and a 50/50 edge, if the hole doesn't go past the centre of the thickness of the blade, would you still be able to have an unaffected edge, other than it being thinner behind that part? I thought the problems came when the hole crossed the centre of the blade and interfered with the edge.

If it does that, your knife is SOL forever.

You can sharpen a knife like this, but it's tedious, and the bevel will always look wavy at the shoulder and it will be weaker there because it's thinner. Plus if you put it on a honing rod, your hole pops right back up.

StephanFowler
04-24-2012, 03:18 PM
I keep thinking about this, for simplicity assuming a 50/50 grind and a 50/50 edge, if the hole doesn't go past the centre of the thickness of the blade, would you still be able to have an unaffected edge, other than it being thinner behind that part? I thought the problems came when the hole crossed the centre of the blade and interfered with the edge.

The problem is moreso that when you sharpen the knife normally you will end up with an area of the blade that doesn't contact the board, and without correction it will just get worse and worse

TB_London
04-24-2012, 04:51 PM
it will be weaker there because it's thinner.
Agreed, but if the remediation is thinning the blade to a uniform thinness, the weakness shouldn't be a concern-or you'd be weakening the whole edge?

I'm trying to see why the edge won't make board contact if the steel that actually forms the edge is still present. So long as you are using stones that won't follow the hole and make it deeper, in the way that a belt will, in my head you should still be able to get even board contact, the same ad if you thinned away the steel to remove the overgrind. Unless the overgrind has removed your 'edge forming steel'

Eamon Burke
04-24-2012, 05:33 PM
So long as you are using stones that won't follow the hole and make it deeper, in the way that a belt will, in my head you should still be able to get even board contact, the same ad if you thinned away the steel to remove the overgrind. Unless the overgrind has removed your 'edge forming steel'


That would be true if your sharpening technique is solid, your stones are dead flat, and abrasives are larger than the overgrind. This means use of a honing rod, aggressive strops, even the wear and tear of normal use will just make the hole show right back up. It will be a constant source of frustration. Also, the burr you will build up trying to get down to that edge will be a honker, and then you use it and it chips out/wears down, and then you have the hole again and have to grind off the entire blade to meet it again.

Also, to fix it properly, you'd need to abrade the ENTIRE knife evenly, or else you'd end up creating a new grind problem somewhere on the knife.

One of the reasons to buy a really good quality hand made knife is that there ARE guys making knives without any sort of overgrind at all--and they are a BREEZE to sharpen. Makes life a lot easier.

You aren't wrong, it's just that the management of such an issue is so frustrating it's like having a car that is permanently misaligned.

Lefty
04-24-2012, 05:51 PM
If you ask me, the only real way to solve this problem is by taking the blade, treating it as a sheet of (whatever type of steel), creating a new profile that is higher up the blade than the hole reaches, and starting anew. Essentially, taking a gyuto and making a short suji, or a cleaver and making a nakiri.

Andrew H
04-24-2012, 05:59 PM
If you ask me, the only real way to solve this problem is by taking the blade, treating it as a sheet of (whatever type of steel), creating a new profile that is higher up the blade than the hole reaches, and starting anew. Essentially, taking a gyuto and making a short suji, or a cleaver and making a nakiri.

The amount of work required to do that kind of change would be huge.

Lefty
04-24-2012, 06:23 PM
Nothing a tile saw with a good blade/water-cooled angle grinder and a bench sander can't handle. :)

Andrew H
04-24-2012, 06:30 PM
Nothing a tile saw with a good blade/water-cooled angle grinder and a bench sander can't handle. :)

And quite a bit of skill to make anything more than a knife shaped object.

Lefty
04-24-2012, 06:39 PM
Very true! Haha

EdipisReks
04-24-2012, 07:32 PM
One of the reasons to buy a really good quality hand made knife is that there ARE guys making knives without any sort of overgrind at all--and they are a BREEZE to sharpen. Makes life a lot easier.

i've now handled three Shigefusas, and none have this issue, so i think you are right. ;)

stevenStefano
04-24-2012, 07:44 PM
I've only ever seen this on one of my knives and it is near the heel anyway so it doesn't bother me too much to be honest

TB_London
04-24-2012, 08:09 PM
Sorry if I'm coming across as argumentative, I'm just trying to get my head around it as it seems in practicality over grinds cause more issues than I can attribute conceptually. Plus I'm so used to writing technical reports my writing style can be a bit to the point.


This means use of a honing rod, ........, will just make the hole show right back up.

As the honing rod is running along the bevel which is flat, I would have thought it wouldn't follow the hole, as it is in the blade face?


Also, the burr you will build up trying to get down to that edge will be a honker
I don't follow why I'd make a bigger burr, conceptually if I sharpen as normal I'd still hit the edge all along in the same way as if the over grind wasn't there. The bevel won't look even, but it will be.


I think I'll make up some mock blades out of wood tomorrow and try to help explain my rationale. They may make the issues stand out clearer as well

Cheers for the answers so far, guess I've been lucky in that over grinds haven't really been an issue on any of my knives yet.

Dave Martell
04-24-2012, 08:27 PM
Here's some more fun overgrind pictures to take a look at. This was a new knife that the customer used but NEVER sharpened. This is the Moritaka Effect! :lol2:

To be fair to Moritaka this was a long time ago and it is the worst one I've ever seen. Still though, it does show the typical Moritaka effect that they still do today, although they do it on a much smaller & harder to see scale than this.

SpikeC
04-24-2012, 08:47 PM
No biggie, you just use the part that touches the board! Or use it in hand......

Eamon Burke
04-24-2012, 08:48 PM
Oh :censored:, that knife is totally.






Tb, I had the same idea! Wood blades it is.

ifor
04-24-2012, 11:07 PM
Anyone know what I can do with this Moritaka?

http://i232.photobucket.com/albums/ee113/iformorris/IMAG0349.jpg

http://i232.photobucket.com/albums/ee113/iformorris/IMAG0351.jpg

SpikeC
04-24-2012, 11:18 PM
Grind the crap out of it?

jm2hill
04-24-2012, 11:41 PM
Grind the crap out of it?

+1 get a DMT and head to work.

crap chip there.

ifor
04-24-2012, 11:55 PM
I hate this knife.
I love my Misono UX10 though.

Sarge
04-25-2012, 12:42 AM
I would say a gentler technique as well as a more obtuse angle.:tease:

No seriously though you'll just have to grind that bad boy out. That is a bummer. I had a Moritaka never had an problems other than the ridiculously over-reactive cladding. Sucks to see that happen to a knife

Crothcipt
04-25-2012, 01:52 AM
ya and put a micro bevil on the finished product. The chipping will go away.

It wasn't a big problem until the second pic.

ifor
04-25-2012, 02:36 AM
I am not sure how the chip got there, I am pretty sure someone tried to sharpen it with one of those cheap sharpeners though. At least that would account for the chipped edge, but no one will fess up to the big chip.

stevenStefano
04-25-2012, 06:50 PM
I have a knife with a similar overgrind to Dave's original post and it is kinda funny because for a while I was a little pissed off because I thought I had undersharpened the heel because it was lower than the area just after it, but at least now I know it wasn't my fault

Chef Niloc
04-26-2012, 04:40 AM
No biggie, you just use the part that touches the board! Or use it in hand......

Everyone just needs to stop cuting on hard flat boards, cut on a stack if old newspaper or some wet towls.

In the 1st pic Dave was the blade bent at all? It kind of looks like you would get that kind of overgrinde if the edge wasn't straght?