Asymmetry – The REAL DEAL

Find deals on amazon
Advertise with us
Kitchen Knife Forums

Help Support Kitchen Knife Forums:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
I thought of another example that might help clear this matter up some.

Let's this time use a honesuki (a double beveled 90/10 ground knife) as our test mule. We'll use a right handed version here for our discussion.

So this is a knife that's a bit thicker than a gyuto is and much more asymmetrically ground.

Here's a picture of the right side of the knife....




Here's a picture of the left side of the knife....




You should note that the edge bevel on the right side of the knife is significantly taller in height than the bevel is on the left side, in fact the left side edge bevel is almost difficult to see at all.

This is a good example of how you can not use the same angle when sharpening both sides of the knife and that's true for both free handing and using a guided device.

If you're free handing the spine will have to be further away from the stone on the right side of the knife then when compared with the left side but only by a small amount. This is to adjust for the thicker blade.

If using a guided device (like the Edge Pro) it is easy to see (in use) how you must change the angle of the stone arm. What happens is say we choose the left side (the side with the very small bevel) to sharpen first. We lay the knife down onto the flat table and then adjust the stone arm to hit this edge bevel correctly, making about a 1-2mm bevel at the very cutting edge. When we flip the knife over to the right side (the side with the large bevel) we immediately see that the stone is hitting above the edge bevel on the right side. Why? Because the knife is nearly flat on one side and has a large wide bevel on the other side - it's asymmetrical.



Now let's take a single bevel (a 100/0 ground) knife like a yangiba and sharpen this both using freehand and a guided device and what do we have happen? We see the very same things as we do with the honesuki (90/10) knife except the issue of having to use different angles is even greater enhanced for us to note and have to deal with.

Is there anyone who thinks that you can use the same angle on an Edge Pro (or even freehanding) for both sides of a yanagiba (by using the grind more on one side than the other method or the counting strokes method) and have it come out OK? I seriously doubt that I'll find someone who can show me this to be the case. Why? Because I know that I have to sharpen at least a 15deg bevel angle on the right side and then switch to 0 deg the left side. Why? because the knife is asymmetrical - FACT!

The very same principle/practice is true for all Japanese knives because they are all asymmetric, the amount of change that we make (or not) is dependent mostly on the amount of asymmetry of a particular style of blade as well as the blade's thickness. We can, but should not, ignore these simple facts if we want to properly sharpen our Japanese knives.
 
Thank you! This example just helped my head a lot. Makes perfect sense that I would have to adjust the arm's angle on the Edge Pro every time I flip the blade to accommodate asymmetry. It is starting to really come together for me now.
 
I think the best way of explaining why some people don't like guided devices for sharpening around these forums is pretty simple. A guided device does nothing more other than provide a sharp edge. If you want your knife to cut great than you definitely need to free hand IMO. So if all you care about is slicing paper with no effort take a guided device, if you care about cutting all sorts off stuff with ease then go the hard way and learn how to free hand.

As Dave mentioned there are no absolutes in sharpening, always adjust and adapt to make a knife work for YOU.
 
Thanks for this thread Dave. May save some of us from going down an a path of
sharpening/cutting frustration :eek2:
 
##{}{%, this is longer, better thought through and more complicated than most of final papers I am reading right now... And I really only want reasonably sharp knives. Makes me want to reconsider pull-through gizmos again... ;) I still don't see the appeal in sharpening, sometimes it seems way over my small brain's capacity...

Stefan
 
So am I correct in saying that when a knife is described as being "90/10 right hand ground" that it means that the cutting edge is 90% offset to the right side? Like if you had a number line (1-2-3-4-5-6-7-8-9-10) that represented the total width of the spine of the knife, the cutting edge is sitting on the 9th place holder?
 
This might explain why my Fujiwara FKH Gyuto can shave armchair and glide through printer paper just fine, but wedges like it has superglue on the sides of it when I go to cut carrots/potatoes. Just when I thought I was getting the hang of sharpening, good old Dave brings be back to square 1.
 
adletson said:
So am I correct in saying that when a knife is described as being "90/10 right hand ground" that it means that the cutting edge is 90% offset to the right side? Like if you had a number line (1-2-3-4-5-6-7-8-9-10) that represented the total width of the spine of the knife, the cutting edge is sitting on the 9th place holder?
Click to expand...
yup
 
El Pescador said:
yup
Click to expand...

Really? With the spine up, edge down, tip facing away from you, the bevel is farther on the right side than on the left side? This doesn't make sense to me considering that on a right-handed single beveled knife, the edge will be at 0.
 
Okay. So essentially when we sharpen a knife that is asymmetrical, we are replicating the edge that was ground into the knife by the maker of the knife? Clayton's illustration shows that an asymmetric grind can be produced by:
1. Grinding less on the "10 ground" side of the knife than on the "90 ground" side of the knife or
2. Sharpening at a more obtuse angel on the "90 ground" side and a more acute angle on the "10 ground" side.
So the maker can achieve the "90/10" edge (or the edge at the 9th place holder) by either method he prefers and it is our job to find which method is used and replicate. Am I right?
 
adletson said:
Okay. So essentially when we sharpen a knife that is asymmetrical, we are replicating the edge that was ground into the knife by the maker of the knife?
Click to expand...

Maybe. You can use the maker's edge bevel IF you believe that it replicates the asymmetry of the blade and then once you do this you find that the knife cuts straight. There is no rule to follow here.


adletson said:
Clayton's illustration shows that an asymmetric grind can be produced by:
1. Grinding less on the "10 ground" side of the knife than on the "90 ground" side of the knife or
2. Sharpening at a more obtuse angel on the "90 ground" side and a more acute angle on the "10 ground" side.
So the maker can achieve the "90/10" edge (or the edge at the 9th place holder) by either method he prefers and it is our job to find which method is used and replicate. Am I right?
Click to expand...


Wrong. I see gaps in both directions that if followed will lead you down the wrong path. You need to evaluate each and every knife and each and every edge bevel and adjust as necessary - this is the only correct answer.
 
I acutally have a Hiromoto AS and I thinned it down a little, the sides are still assymetric, less than in new knife though.

I sharpen edge 50/50, and do little convexing - maybe 4 or 5 angles togehter.

I can promise this knife cuts twice as good now as when it was new.

I sharpen left side of knife with left hand, its possible that my angle is different, but I think they are both pretty similar.
I read once on JCK that Hiromoto has two altering angles and the difference was 3 degrees between sides!! Good joke
I will never get to that kind of skill ever. No point trying.
 
heirkb said:
Really? With the spine up, edge down, tip facing away from you, the bevel is farther on the right side than on the left side? This doesn't make sense to me considering that on a right-handed single beveled knife, the edge will be at 0.
Click to expand...

do you mean higher up the blade?
 
A few questions:

1. When a knife is asymmetric, is it asymmetric from the spine down or just at the bevels? Or reworded, is it ground at dfferent angles the entire width of the blade from the spine down or is it just the bevel that is ground asymmetrically?

2. While I can see that the generalizing I made in my previous post is at fault, is the basic premise not correct? That in order to get an asymmetric result, you have to do different things to the two sides of the blade, either to grind less at the same angle as the matching side or to grind at a different angle than the matching side?

3. Continuing with my number line picture (1-2-3-4-5-6-7-8-9-10), on a "90/10 right hand ground" asymmetric knife, with the spine up, edge down, tip facing away from you, would the knife edge be at 2 or 9?
 
Dave Martell said:
If you want to play it safe (while freehanding) a new knife with less than clear factory bevels then I'd suggest starting on the right side (if it's a righty knife) and once I've figured out the appropriate angle for this side I'd flip the knife over to the left side and sharpen at the same angle. If you've done things correctly then these edge bevels should match up to the blade asymmetry pretty closely. If you've got it wrong you might not notice straight away, it might take a few more sharpening sessions for the blade to start twisting while cutting and if that happens you then adjust by grinding more on one side or the other.
Click to expand...

So I have a few other questions here. What do you do to figure out the angle on that first side? I realize that practice is big, but I don't even know where to start, lol. You get the angle, flip the knife, and sharpen till burr? That will itself lead to asymmetric bevels (bigger on the right)?

And if you feel the blade twisting...let's say it twists towards the left while cutting on a right handed knife. The post above says you adjust by grinding more on one side or the other. So what side would you be grinding more on/making angle adjustments on if the knife steers a bit too much? That is, what type of improper sharpening does the steering suggest?
 
heirkb said:
So I have a few other questions here. What do you do to figure out the angle on that first side? I realize that practice is big, but I don't even know where to start, lol. You get the angle, flip the knife, and sharpen till burr? That will itself lead to asymmetric bevels (bigger on the right)?

And if you feel the blade twisting...let's say it twists towards the left while cutting on a right handed knife. The post above says you adjust by grinding more on one side or the other. So what side would you be grinding more on/making angle adjustments on if the knife steers a bit too much? That is, what type of improper sharpening does the steering suggest?
Click to expand...

If you are right handed and the knife pulls toward your left hand when cutting you can either: grind more on the left hand side to even it up and bring it closer to 50/50. Or you can relax your grip some and not try to make the knife go somewhere but rather let the edge do the cutting for you. Either way you'll find that steering decreases
 
Originally Posted by adletson

So am I correct in saying that when a knife is described as being "90/10 right hand ground" that it means that the cutting edge is 90% offset to the right side? Like if you had a number line (1-2-3-4-5-6-7-8-9-10) that represented the total width of the spine of the knife, the cutting edge is sitting on the 9th place holder?
yup

I think its the opposite???

My reasoning tells me that the offset is to the left as the right side has a higher bevel.. meaning that it has been sharpened at a lower angle. IF the the Left side is sharpened at Zero.. it is a single bevel. Since the left bevel is so small, it would mean that it it sharpened between 10 to 15degrees.. thus form the top of spine position it is anywhere between NO 2 or 3 as per your example

I suppose there should be a sharpening angle on the left side that makes it dead center of the spine. IF the total angle left and right is say 40 degrees.. close to the german sharpening way but with teh thinner bevel on the right side.. a thinner blade on the edge..

Just my thoughts...

rgds
 
This is how i understand it :

grinds.png


The right is the right side of a knife when you hold it in the hand. I think that Dave talks about picture 3.


Please corect me if i am wrong :sad0:
 
What I don't understand is why making the asymmetry on the bevel match the asymmetry on the blade face reduces steering. Say you have a 90/10 right hand bias blade face. Why would a 90/10 bevel steer less than a 50/50?
 
This is a subject that is very difficult to elucidate without massive amounts of diagrams & illustrations, or just sharpening and re-sharpening and extensively using different knives.

I am considering tackling this topic. But in the mean time, if you trust me at all, Dave is right.
 
I want to understand just about the same thing. Massive lot of diagrams for me, please
 
At the risk of appearing very stupid, in what way would using a magic marker along the edge work/not work here?
 
Assuming the knife was not altered from the appropriate bevels given by the maker, it would work just fine. As always.

If you screwed it up first, the marker trick won't guide you through repairing it.
 
I have been dwelling and debating with this with myself for quite some time now. I get the whole thing that if you sharpen , say a knife that comes from a manufacture that is 70/30 , and sharpen to a almost 50/50 edge it will be just fine. The knives Im talking about are western style Gyutou's .

Im left handed and I have used knives set up for right hand use with little to no ill effect. Just the occasional blade feeling like its cutting towards the food as apposed to away from the food, depending on the product being cut. My question is are these knives ground throughout the entire blade from edge to spine with one side flat and one side sort of half a clam shell. For example HAMAGURI (convex) edge. If this is the case how would effect a knife for a person who is left handed and wants to set his edge's wider on the left side and less on the right side of the blade.

Especially if the user is a pro cook/chef who can reduce his knives entire profile from sharpening by many inches over say a period of 2 years of use. Will the knife still work once you start getting up into the blade. Hope this makes sense. Diagram below kind of show what im trying to explain.

topimg04.gif
 
Specific examples that some may know - just to get a little more clear on this.

So a KS: This knife is flat on the left side and convex on the right. In this case a large low/medium bevel on the right and low angle debur on the left is the best scenario? This puts the edge in position 2, let's say.

So a Shig: This knife is concave just below the spine, then flat, then convex on maybe the last 3/8". It appears to be more or less the same geometry on both sides. The best routine for this knife is likely a 50/50 equal?

Is this consistent with what Dave is explaining?

s.
 
I learned all my sharpening one on one wt. Japan trained Sushi Chefs.All freehand on the stones,double & triple blended bevels on Gyuto.Yanagi,deba,usuba,hollow ground single bevels,Cleavers I always use 50/50.Gyuto mostly assem,even turned a few into single bevels.

When I first saw Dave Martels DVD I learned why what I was doing worked.What he calls thinning behind the edge is the same as the blended bevels I've put on my carbon masamoto's many yrs.

This is how I learned assym. bevels,wt fingerpads press edge of blade till it bites a little into the stone,check your spine thats your edge contact angle if you want to blend lower the spine just a hair & work it till you get a burr.Flip the blade over & do the same thing.With a assem. blade when you press edge into stone the spine will be higher on cutting side & lower on backside.You do have to worry about degrees of angles just pay attention to the edge contact on stone & always keep a steady spine while sharpening.

Sound too simple?Well alot of it is some simple tricks as Dave said there is alot of diff. info. on sharpening,I have found Japan styles to be the best it's never failed me all these yrs.Since I first learned it 30 yrs ago Ive never had to use a dull knife,of coarse I only use carbons.Much of it is good tips & practice.The feel for the flow of steel on stone.
 
Thanks Dave, Eamon and everyone else who had contributed to this thread. I have read, & re-read it, made notes and drawings and today put it into practice and was amazed, I've never got results like this before, I have an edge pro collecting dust but was reluctant to sell it off because I could not get consistent results free handing. I thinks it's time to move it on and make room for some new stones:)
 
You must log in or register to reply here.

Latest posts

Back
Top