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View Full Version : How to even out the contact patch?



MWhtrader
10-23-2011, 02:02 AM
So I was chopping some stuff, and noticed some parts of it arent detaching from the food, so I added a slight draw to the chops so they would come out clean.

Anyways, after I was done, I put the blade against a flat edge and saw some light leaking through, which mean the the contact patch isnt entirely even.

I thought about sharpening that section more than the other but that might not solve my problem as I may not have the control to even it out like that . or maybe I should grind hte edge to even, then sharpen the edge back up ?

It would be great if someone can help. oh and btw the knife is a hiromoto gyuto

JohnnyChance
10-23-2011, 03:09 AM
The latter. Grind the edge even, then sharpen it. Put it on your coarsest grit stone or plate, perpendicular to the stone, like as if it was a cutting surface. Run it back and forth until you are satisfied with out flat it is, then restore the edge bevels. It shouldn't take too much.

slowtyper
10-23-2011, 03:51 AM
I've done that to flatten my usuba. Be careful, do it slowly because it can eat a lot of steel in a hurry doing it like that

dmccurtis
10-23-2011, 04:01 AM
If it's your first time doing so, grind at 45 rather than 90. You'll remove steel less quickly, and it will be faster to restore the edge when you're done.

tk59
10-23-2011, 10:47 AM
If it's your first time doing so, grind at 45 rather than 90. You'll remove steel less quickly, and it will be faster to restore the edge when you're done. And if the "hole" isn't too deep, you don't have to use a super coarse stone. The thin metal near the edge really gets chewed up that way. For minor fixes, I sometimes will use the side of a 1k stone, for example.

Eamon Burke
10-23-2011, 11:19 AM
Btw, that is called a hole in the edge.

tk59
10-23-2011, 11:54 AM
Btw, that is called a hole in the edge.Is that a technical term?

Eamon Burke
10-23-2011, 12:08 PM
Yep, and it isn't synonymous with an overgrind, because it can be caused by just sharpening too much in one area, which is easy to fix. An overground face bevel is bad news, and also can cause a hole in the edge.

Benuser
10-23-2011, 12:52 PM
Please verify if enough clad has been removed, as it might come very near to the edge, especially on the back side.

Greg the Yeti
10-23-2011, 02:13 PM
Anyways, after I was done, I put the blade against a flat edge and saw some light leaking through, which mean the the contact patch isnt entirely even.
the knife is a hiromoto gyuto

Hi, it sounds as if your knife is an un-usual Gyuto in that it sounds as if your knife is ground with a bevel only on one side? If your Gyuto is like this then it is like a Yanagiba which is made with a concave hollow on the 'Flat Side'. This is there for a purpose, and helps to reduce the amount that the food sticks to the blade.

I seriously hope that you have not followed the advice given elsewhere to your post as you will have wrecked your expensive knife! I know from experience as I did the same to a cheap Yanagiba before I knew what that hollow was for.

For further info see the page
http://zknives.com/knives/articles/knifeedgetypes.shtml#SG

In order to leave the concave hollow on the 'Flat Side' you must not grind it on any kind of flat stone! You will need to sharpen only on the bevelled side, then only remove the burr that this causes on the 'Flat Side'.

To do that my recommendation would be to lightly use a small narrow piece of wood with very fine abrasive paper glued to it (or a very narrow fine stone if you happen to have it). Follow the 'flat' near the edge and you will remove the burr without removing the hollow.

I hope I've been in time!:eek2:

JohnnyChance
10-23-2011, 02:20 PM
He has a hollow in his cutting edge, not on the face of the blade.

Benuser
10-23-2011, 03:25 PM
Hi, it sounds as if your knife is an un-usual Gyuto in that it sounds as if your knife is ground with a bevel only on one side? If your Gyuto is like this then it is like a Yanagiba which is made with a concave hollow on the 'Flat Side'. This is there for a purpose, and helps to reduce the amount that the food sticks to the blade.

I seriously hope that you have not followed the advice given elsewhere to your post as you will have wrecked your expensive knife! I know from experience as I did the same to a cheap Yanagiba before I knew what that hollow was for.

For further info see the page
http://zknives.com/knives/articles/knifeedgetypes.shtml#SG

In order to leave the concave hollow on the 'Flat Side' you must not grind it on any kind of flat stone! You will need to sharpen only on the bevelled side, then only remove the burr that this causes on the 'Flat Side'.

To do that my recommendation would be to lightly use a small narrow piece of wood with very fine abrasive paper glued to it (or a very narrow fine stone if you happen to have it). Follow the 'flat' near the edge and you will remove the burr without removing the hollow.

I hope I've been in time!:eek2:

I'm sorry I have to disagree. There's nothing unusual about the Hiromoto, excepted the clad.
It has nothing in common with a single bevelled.
Front side is convex with a large bevel ending at some 12 degree, back side almost flat with a small 15 degree bevel. Just make sure you remove some clad in order to free the core steel. Compare it to a pencil you sharpen where you have to remove enough wood.

Eamon Burke
10-23-2011, 03:55 PM
Hi, it sounds as if your knife is an un-usual Gyuto in that it sounds as if your knife is ground with a bevel only on one side? If your Gyuto is like this then it is like a Yanagiba which is made with a concave hollow on the 'Flat Side'. This is there for a purpose, and helps to reduce the amount that the food sticks to the blade.

I seriously hope that you have not followed the advice given elsewhere to your post as you will have wrecked your expensive knife! I know from experience as I did the same to a cheap Yanagiba before I knew what that hollow was for.

For further info see the page
http://zknives.com/knives/articles/knifeedgetypes.shtml#SG

In order to leave the concave hollow on the 'Flat Side' you must not grind it on any kind of flat stone! You will need to sharpen only on the bevelled side, then only remove the burr that this causes on the 'Flat Side'.

To do that my recommendation would be to lightly use a small narrow piece of wood with very fine abrasive paper glued to it (or a very narrow fine stone if you happen to have it). Follow the 'flat' near the edge and you will remove the burr without removing the hollow.

I hope I've been in time!:eek2:

Hiromoto Gyutos, like most gyutos, are not traditional Japanese single-bevel knives. There is no concave ura on a Hiromoto gyuto.

What he has is a hole in the edge. It is caused by either the faces being ground improperly(not at all likely from a Hiromoto, though remotely possible), or from being steeled/honed/sharpened in that one spot too much or too agressively.



And you can totally deburr and manage the ura on a kata-ha grind(which is NOT what the OP has) with a stone--that is how they are designed, and how they have been maintained for hundreds of years.

MWhtrader
10-23-2011, 07:06 PM
its the standard double bevel gyuto. I am not sure if its my sharpening or it it came like that, the contact patch on the first bit is pretty small (like 2 to 3 inches) due to the belly, but I always had problems chopping with this knife. its likely hte came like that.

and its not a huge hole, maybe like 2 to 3 post-it's high, barely a sliver but enough to show up when I chop.

thanks everyone ! I got my stones soaking should be able to report back tonight. I am assuming this is what I do if I want to flatten the profile a little too?

UglyJoe
10-23-2011, 07:27 PM
its the standard double bevel gyuto. I am not sure if its my sharpening or it it came like that, the contact patch on the first bit is pretty small (like 2 to 3 inches) due to the belly, but I always had problems chopping with this knife. its likely hte came like that.

and its not a huge hole, maybe like 2 to 3 post-it's high, barely a sliver but enough to show up when I chop.

thanks everyone ! I got my stones soaking should be able to report back tonight. I am assuming this is what I do if I want to flatten the profile a little too?

Yes and no. It will work to flatten the profile, but the problem will be that you flatten the profile by raising the edge at the heel. This will result in that part of the edge (or just above the edge) being thicker relative to the rest of the knife, and will make the knife perform poorly in this are. If you are going to do this you will probably need to thin a lot behind the edge in the heel to get things to perform well. Not a bad knife to practice this on, though!

EdipisReks
10-23-2011, 07:44 PM
Hi, it sounds as if your knife is an un-usual Gyuto in that it sounds as if your knife is ground with a bevel only on one side? If your Gyuto is like this then it is like a Yanagiba which is made with a concave hollow on the 'Flat Side'. This is there for a purpose, and helps to reduce the amount that the food sticks to the blade.

I seriously hope that you have not followed the advice given elsewhere to your post as you will have wrecked your expensive knife! I know from experience as I did the same to a cheap Yanagiba before I knew what that hollow was for.

For further info see the page
http://zknives.com/knives/articles/knifeedgetypes.shtml#SG

In order to leave the concave hollow on the 'Flat Side' you must not grind it on any kind of flat stone! You will need to sharpen only on the bevelled side, then only remove the burr that this causes on the 'Flat Side'.

To do that my recommendation would be to lightly use a small narrow piece of wood with very fine abrasive paper glued to it (or a very narrow fine stone if you happen to have it). Follow the 'flat' near the edge and you will remove the burr without removing the hollow.

I hope I've been in time!:eek2:

no.

UglyJoe
10-23-2011, 08:08 PM
no.

HAH. QFT!

Eamon Burke
10-23-2011, 09:47 PM
Make sure your stones are flat!

Greg the Yeti
10-24-2011, 05:05 AM
Hi, my first post seems to have caused a rumpus!
I'm glad my post contained that small but important word 'IF'
It just goes to show how language that is not very precise can be easily misunderstood.
The original post talked about a gap in the 'Contact Patch', which is not very precise. However he also seemed to be talking about the food sticking to the knife. Hence my alarm and thinking that he was talking about the contact area between food and kife, not the contact 'line' between knife and chopping board.
Yes I knew that a Gyuto normally has a double bevel, but apparently not always. All three that I have are the normal double bevel type.

Benuser
10-24-2011, 07:31 AM
Nothing to worry about. Most readers are quite familiar with Hiromotos I guess.

Eamon Burke
10-24-2011, 08:32 AM
Hi, my first post seems to have caused a rumpus!
I'm glad my post contained that small but important word 'IF'
It just goes to show how language that is not very precise can be easily misunderstood.
The original post talked about a gap in the 'Contact Patch', which is not very precise. However he also seemed to be talking about the food sticking to the knife. Hence my alarm and thinking that he was talking about the contact area between food and kife, not the contact 'line' between knife and chopping board.
Yes I knew that a Gyuto normally has a double bevel, but apparently not always. All three that I have are the normal double bevel type.

It's cool, Greg. Rarely is any offense meant around here. We're just trying to root out the correct information is all.