PDA

View Full Version : assymetric grind or assymetric knife?



gic
02-23-2013, 09:38 PM
is there any obvious way to tell if a knife with say a 80/20, 70/30 or 60/40 grind has simply been sharpened asymmetrically or was actually forged/stamped asymmetrically. In the former case one could make it symmetric without any loss, in the later not so much. i'm thinking of my carbonext for example, Masahiro MV-H or Tojiro DP...

TIA

Dave Martell
02-23-2013, 09:48 PM
I have yet to see a Japanese knife whose blade is anything but asymmetric so IMO it's pretty easy to tell which ones are asymmetric because that's all of them.

Benuser
02-23-2013, 09:59 PM
All Japanese I've seen - and, by the way, most French - are more or less asymmetric, one side more or less flat, another one more or less convex, and have a more or less off centered axis. A really symmetric blade would wedge as no other. You may put a symmetric edge on an asymmetric blade, but sooner or later you will experience crazy steering or wedging. If the blade is very thin it's not all that obvious.

Mike9
02-24-2013, 12:50 AM
My Hiromoto and Yoshihiro gyutos are both convex on the right side and pretty much flat on the left. Any decent straight edge will tell you.

stevenStefano
02-24-2013, 03:35 PM
Simple way is to look at the knife from the choil. Like everyone says, basically all of them are asymmetric, which sucks if you're a lefty

panda
02-25-2013, 02:31 AM
im not all too fond of asymmetric bevels, is it bad to sharpen an asymmetrically ground knife to a 50/50 bevel? if so, why?

James
02-25-2013, 02:35 AM
im not all too fond of asymmetric bevels, is it bad to sharpen an asymmetrically ground knife to a 50/50 bevel? if so, why?

Dave wrote an AWESOME thread about this. It's definitely worth a read.

http://www.kitchenknifeforums.com/showthread.php/5656-Asymmetry-%E2%80%93-The-REAL-DEAL

gic
02-25-2013, 07:03 AM
So this obviously leads to a question: is a lefty knife forged differently or just badly resharpened.....

andur
02-25-2013, 07:06 AM
My Katsushige Anryu santoku and petty are both as symmetric as I can tell. I've not seen an asymmetric santoku yet... or have I been missing something?

gic
02-25-2013, 07:06 AM
I think one exception might be macs. I'm looking at my Mac Pro MT-80 down the choi and it looks awfully symmetric to me.

stevenStefano
02-25-2013, 07:07 AM
A lefty knife is ground with the more convex side (say the 70) on the left and the flatter part (30) on the right

andur
02-25-2013, 07:36 AM
Ok I've now spent 15minutes staring at my knife bevels and trying to guesstimate their angles. Either with or without magnification I can only conclude I couldn't say the sharpening angles of the knives I didn't sharpen myself. I'll know them after I've sharpened them but on a given knife it's pretty hard for me to say.

http://cdn.cheftalk.com/3/34/34539d37_MACProedge.JPG
This mac choil seems to be just an asymmetric grind but the rest of the blade seems symmetric. I mean if someone would want to change the dominant hand for this knife it looks like it could be done with a bit of grinding.

Benuser
02-25-2013, 09:05 AM
Ok I've now spent 15minutes staring at my knife bevels and trying to guesstimate their angles. Either with or without magnification I can only conclude I couldn't say the sharpening angles of the knives I didn't sharpen myself. I'll know them after I've sharpened them but on a given knife it's pretty hard for me to say.

http://cdn.cheftalk.com/3/34/34539d37_MACProedge.JPG
This mac choil seems to be just an asymmetric grind but the rest of the blade seems symmetric. I mean if someone would want to change the dominant hand for this knife it looks like it could be done with a bit of grinding.

Very nice pic. To me it's quite obvious the left face - the right in the picture - is flat, and the other side is convex. Put a ruler against it: it will touch the entire left face. Do it on the other one: it will only touch the area near the spine.

Dave Martell
02-25-2013, 01:13 PM
So this obviously leads to a question: is a lefty knife forged differently or just badly resharpened.....


Lefties are made lefty - not just sharpened that way

Dave Martell
02-25-2013, 01:16 PM
I think one exception might be macs. I'm looking at my Mac Pro MT-80 down the choi and it looks awfully symmetric to me.


MACs, Globals, Shuns (etc) aren't what I consider true Japanese knives, they're more like made in Japan for the west. These knives are the exceptions, they'll be found to be symmetric.....sometimes. I never include these knives in this discussion and I should have made that clear.

Dave Martell
02-25-2013, 01:18 PM
Ok I've now spent 15minutes staring at my knife bevels and trying to guesstimate their angles. Either with or without magnification I can only conclude I couldn't say the sharpening angles of the knives I didn't sharpen myself. I'll know them after I've sharpened them but on a given knife it's pretty hard for me to say.

http://cdn.cheftalk.com/3/34/34539d37_MACProedge.JPG
This mac choil seems to be just an asymmetric grind but the rest of the blade seems symmetric. I mean if someone would want to change the dominant hand for this knife it looks like it could be done with a bit of grinding.


This knife is right handed asymmetric. Don't look at the edge - look at the blade.

mhlee
02-25-2013, 01:26 PM
A really symmetric blade would wedge as no other. You may put a symmetric edge on an asymmetric blade, but sooner or later you will experience crazy steering or wedging.

Can you name some examples?

Zwiefel
02-25-2013, 02:19 PM
This knife is right handed asymmetric. Don't look at the edge - look at the blade.

I wish I could see what you are seeing...I understand this conceptually, but I have yet to figure out how to look at a knife to see this.

andur
02-25-2013, 02:36 PM
I agree with Zwiefel on this. Also I should add it's a random mac knife pic from the web, not a knife I have at the moment. I drew some lines over the blade in Paint and it does seem to be fairly symmetric in my eyes. Given a lot of these knives are hand forged and hand ground I'd be very suprised if they could grind some 0.1mm differences to the edges by eyeballing/experience. I'd think they just grind it semi flat on both sides and then carefully sharpen the asymmetric edge?

ThEoRy
02-25-2013, 02:41 PM
Ok I've now spent 15minutes staring at my knife bevels and trying to guesstimate their angles. Either with or without magnification I can only conclude I couldn't say the sharpening angles of the knives I didn't sharpen myself. I'll know them after I've sharpened them but on a given knife it's pretty hard for me to say.

http://cdn.cheftalk.com/3/34/34539d37_MACProedge.JPG
This mac choil seems to be just an asymmetric grind but the rest of the blade seems symmetric. I mean if someone would want to change the dominant hand for this knife it looks like it could be done with a bit of grinding.

I just took a piece of paper and held it up to the screen and I can tell you the left side of the knife (not the picture) is basically flat while the right of the knife has some curve.

EdipisReks
02-25-2013, 02:43 PM
I wish I could see what you are seeing...I understand this conceptually, but I have yet to figure out how to look at a knife to see this.

the line on the right (which is the left face of the blade) is basically straight up and down (flat.) see how the line on the left (which is the right face of the blade) is at an angle, in relation to the other line?

Chefdog
02-25-2013, 02:44 PM
I wish I could see what you are seeing...I understand this conceptually, but I have yet to figure out how to look at a knife to see this.

Try this:

Put the edge down on the board and look from behind at the choil, making sure the left side (assuming a rh knife) is completely perpendicular to the board. Now check out the right side o the blade. It should be easy to see that the right face of the blade IS NOT also perpendicular, but is angling outward as it goes up from the edge to the spine.

Alternatively: Lay the left face down on a flat surface with the edge facing to your right (handle towards you). Now take a look at the incline of as you go from edge to spine, it'll look like the worlds tiniest bike ramp.

Hope this makes it easier to see what everyone is saying. Essentially the knife is a wedge, but one side (left) is completely vertical and the other (right) is at an outward sloping angle.

The blade is shaped like this, THEN, they grind in the actual cutting bevels according to the proportional asymmetry of the whole blade.

andur
02-25-2013, 02:48 PM
As I understand the grind should be based on the use of the blade. Is there a nice diagram with pictures and explanations of different knife grinds? It would be a great help to decide how to best sharpen/grind the blade to a certain function.

Zwiefel
02-25-2013, 03:02 PM
OK, took ThEoRy's advice and used a sheet of paper as a straightedge. Definitely able to see a subtle curve on the LHS of the photo vs the RHS. If I just stare at the choil and squint just so, I can see that it's more of a right-triangle than an isosceles...but I'm not able to convince myself that I'm not seeing what I expect to see (confirmation bias). Not yet anyway. I was pretty pleased with myself that I immediately noticed the bevels were asymmetric!

Would you all agree that, if properly created + maintained, asymmetric bevel should indicate an asymmetrical grind? That was the primary think I think I learned from Dave's thread on asymmetry.

Thanks to ThEoRy, EdipisReks, and ChefDog for the pointers.

Benuser
02-25-2013, 03:10 PM
Can you name some examples?
I wrote, a really symmetric blade would wedge as no other. Please note this is hypothetic. Symmetric in this context was meant to describe a blade where both faces were equally flat or convex.
No serious brand makes such blade, as they would wedge as a wig, encountering friction at exactly the same height on both sides.
One used to find those blades on markets.
By the way, Michael, I don't believe you were asking for examples of wedging after a 50/50 edge had be put on a strongly asymmetric blade, weren't you? The archives are full of wedging issues after EdgePRO abuse.

mhlee
02-25-2013, 04:02 PM
I wrote, a really symmetric blade would wedge as no other. Please note this is hypothetic. Symmetric in this context was meant to describe a blade where both faces were equally flat or convex.
No serious brand makes such blade, as they would wedge as a wig, encountering friction at exactly the same height on both sides.
One used to find those blades on markets.
By the way, Michael, I don't believe you were asking for examples of wedging after a 50/50 edge had be put on a strongly asymmetric blade, weren't you? The archives are full of wedging issues after EdgePRO abuse.

No. I wasn't asking for examples about a 50/50 edge on a strongly asymmetric blade. I was asking about a 50/50 grind - flat or convex - because I'm curious about this.

IIRC, the two knives that I've owned that had the least amount of wedging were the ones that were closest to 50/50 convex ground on both sides. But, I'm going to look into this to verify this.

Thanks.

Benuser
02-25-2013, 04:21 PM
No. I wasn't asking for examples about a 50/50 edge on a strongly asymmetric blade. I was asking about a 50/50 grind - flat or convex - because I'm curious about this.

IIRC, the two knives that I've owned that had the least amount of wedging were the ones that were closest to 50/50 convex ground on both sides. But, I'm going to look into this to verify this.

Thanks.

With European blades it's common to find both faces being convexed, but into a different degree. Even than, you will see that one face is convexed only at its lower part, while the other's convexity starts from the spine on.

chinacats
02-25-2013, 08:48 PM
Easiest way for me to see the face shape (convexity...) is to lay a flat edge (ruler, pencil, paper) against the blade (spine to edge) and see the contact points, on J-blade almost always full contact on left side and only partial on right.

CompE
02-26-2013, 03:57 PM
It's funny that this topic should pop up because I was just thinking about posting a question about my most recent knife, a Takeda Banno Funayuki. All of my japanese knives are asymmetric, but this one has a very symmetric bevel and edge. Maybe the shop that I bought it from decided to sharpen it? With the Kurouchi finish I can't really lay a straight edge on it to check the faces, but the entire geometry seems pretty symmetric as well. Is it just mine?