PDA

View Full Version : How do you test a new edge?



Zwiefel
07-22-2012, 12:36 AM
I'm in the beginner stage of learning how to use synthetic stones to sharpen my knives. I've had them for about 3 years now but only had a need to use them about 5-6 times. The resulting edges have been acceptable for me, but I'm quite sure I'm still leaving something on the table with what the steel can handle.

What technique(s) do you use to test your edge after you sharpen it? I don't like to use food unless I'm then going to eat it, so I can't always choose that as my time to sharpen doesn't always co-incide.

I have always used a sheet of paper, like this:

http://www.youtube.com/watch?v=4PUhr2rcEyc&feature=g-upl

I can usually feel the way the blade slices through the page pretty well, and look at the quality of the cuts on the pieces.

What is your approach, and why?

K-Fed
07-22-2012, 12:48 AM
News paper shredding and arm hair topping usually. Then at work in the kitchen doing its intended jobs.

cwrightthruya
07-22-2012, 12:59 AM
I usually try and cut what the knife was intended for, but I definitely understand about not wanting to waste food.

With regards to the paper test, I have heard 2 separate theories. The first is if you can push cut at least 1 inch away from the holding point at several places along the edge then it is a good edge. To me this does not make sense as it's too much like the HHT for a straight razor, which does not provide a good view of sharpness on the whole blade. The other I have seen and commonly used is a paper slice method. If you can slice a piece of paper in strip sections as thin as the paper itself along the entire length of the blade, then it is generally a good to great edge. I have never had a "failure" of an edge that passed this test, although I am sure now that I have said it....it will happen.

Zwiefel
07-22-2012, 01:08 AM
Thank you for your response.


To me this does not make sense as it's too much like the HHT for a straight razor, which does not provide a good view of sharpness on the whole blade.

Please excuse my ignorance...."the HHT"? What is HHT?

Do you end up with bare sections on your arm? :wink:

I've not been able to get one sharp enough to cut hair....always wondered if that was even real.

GlassEye
07-22-2012, 01:25 AM
Please excuse my ignorance...."the HHT"? What is HHT?

Do you end up with bare sections on your arm?
HHT= Hanging Hair Test

That is how you can spot a Knife Knut, bald patches all over their arms, or legs as I am running out of arm hair.

Benuser
07-22-2012, 01:26 AM
I use very fine cigarette paper, and listen.

markenki
07-22-2012, 01:26 AM
http://www.youtube.com/watch?v=REMQE_KSsRo

cwrightthruya
07-22-2012, 01:38 AM
I use very fine cigarette paper, and listen.

Phonebook paper also works excellently, and is not nearly as expensive. They throw a new one on my door every month, and I don't even have a home phone!

wsfarrell
07-22-2012, 01:41 AM
I use very fine cigarette paper, and listen.

+1 on "listen." I think if you use the same paper every time (whatever it is), you'll notice that cuts get quieter and quieter as your sharpening improves.

cwrightthruya
07-22-2012, 01:53 AM
The problem with shredding paper is that it is hopefully nothing like the food you should be cutting with your kitchen knife, unless you are a college student :). Depending on what you are sharpening, gyuto vs deba vs yanagi, the edge that you need to put on each blade that gives its intended best performance is completely different. If you get a super "quiet" edge from a gyuto when shredding paper, this will more than likely be a great push cutting edge, but might not have the best performance when cutting tomatoes with tough skin. So definitely learn to gauge what you need regardless of the test used.

hambone.johnson
07-22-2012, 02:33 AM
not for nothing. but its all about a "toothy edge" for me. i do the old school heel to tip rub with my thumb. i need the edge to grab at my skin and pull. a little paper run, and as long as the paper cut is smooth and doesnt leave the paper edge fuzzy im good to go. im a simple kinda guy tho

Bryan
07-22-2012, 06:27 AM
+1 if I stop sharpening on a 5k stone my knives are great with food and fall through tomatoes. If I strop and polish, I get an edge that cuts through paper silently and silkily but is not so good with food.. is there a better way?

Eamon Burke
07-22-2012, 10:46 AM
I cut a carrot and a tomato with it. Then I rub it on my arm, look at it, maybe bend it a little bit with my fingernail. If I'm really curious I'll slam it on the cutting board a few times and then do it again.

Zwiefel
07-22-2012, 05:10 PM
I cut a carrot and a tomato with it.

That part I understand....


Then I rub it on my arm, look at it, maybe bend it a little bit with my fingernail. If I'm really curious I'll slam it on the cutting board a few times and then do it again.

this part confuses me. "bend it a little?" "Slam it on the cutting board?"

Not sure I understand what you mean...I get very nervous when hearing "slam" and my knife being associated with each other! :nunchucks:

Zwiefel
07-22-2012, 05:17 PM
Several of you have described different kinds of edges...some being suited better for some tasks than others. I had never considered that before.

I'm familiar with convex, asymetrical, compound, hollow, etc. edge types (intellectually anyway), but you seem to be describing something beyond that..."toothy" for example.

can you describe both how you acheive such edges and why one would choose one type over another?

Do you have several knives with different edge types for different tasks? or are you just shifting you average based on your typical task?

Seriously, you guys never cease to amaze me with the depth of knowledge + thought about this stuff.

Citizen Snips
07-22-2012, 05:40 PM
i cut stuff

i do not think that paper tests or hair tests show everything. they give you just a small piece of what you are looking for. if you are sharpening a straight razor, then shaving arm hair = cutting stuff. if not, it doesn't really give you an accurate test

there are different knives i like with different edges. for me, cutting paper only finds where the edge is not as good and gives me an idea where i need to work if it has to go back to the stones.

i do agree that cutting a carrot and tomato give you the best idea how well your edge suits the tasks you want for it.

i got used to sharpening every day or two and that will give you a chance to see how good your edge is, but more importantly, how your edge retention is. putting an edge on a knife that will shave paper is only part of the battle, getting it to cut paper after 1 week of hard use is when you know you are getting better

trial and error

cwrightthruya
07-22-2012, 05:46 PM
Ok, I'll give it a shot. I have a tendency to get lost in my own words though, so please forgive me. Think about the edge of your knife being like a saw blade. You can't cut large pieces of lumber very efficiently with a hack saw (small teeth), but you can cut big pieces of lumber with a carpenters saw (large teeth). This is exactly the same principle, but on a much smaller scale. The lower the grit you sharpen to, the large the "teeth" are going to be, making it easier to slice into whatever you are cutting. The downside is that at some point the knife will not feel very sharp, and a knife with too large a "teeth" is not going to do well for certain tasks like preparing sashimi. The other side of the spectrum is that the higher grit you sharpen too, the smaller the "teeth" will be. This is great for fine/delicate tasks, or even to shave hair. But, when you are trying to cut something with tough skin, for instance a tomato, then the small "teeth" sort of slide along the skin instead of grab into it.

cwrightthruya
07-22-2012, 05:49 PM
Oh, and yes to the other questions. Most of us have multiple knives, all with different edges depending on the knife's intended task.

chinacats
07-22-2012, 09:32 PM
I'll add that what Eamon said about slamming the knife on the board a few times is the easiest/quickest way for me to be sure there is not a wire edge...not sure what he meant by bending the edge with his fingernail...

Eamon Burke
07-22-2012, 09:32 PM
this part confuses me. "bend it a little?" "Slam it on the cutting board?"

Not sure I understand what you mean...I get very nervous when hearing "slam" and my knife being associated with each other! :nunchucks:


When I bend the edge, it is to see how the steel flexes. Not as much to do with the edge quality as the angle and design of the knife, and somewhat the heat treat--on Japanese single bevels, where the angles kind of work themselves out naturally, I like to check to see how flexible the steel is once the edge is put on, because I didn't pick the angle, the knife did. I need to know if I should adjust it, and sometimes it will tell me something about the steel.

I don't slam YOUR knife. Only mine. It's just a way of testing for edge failure. Basically, if I sharpened a knife with worthwhile steel(I.E. good heat treat cutlery steel) and slamming it like a hammer on my end grain cutting board renders it useless, then either I screwed up bigtime or I am no longer friends with that knife. Your edge should put up with some serious abuse, and whacking a knife on wood, scraping the edge to see if it will roll, and sometimes even batoning bolts is par for the course when stress testing knives/steels/edges. I don't do this every time(or often, really), but it is something I do when testing something totally new, like when I started sharpening on belts, when I make a knife with a totally new-to-me heat treat, when I get a new knife that I own. Honestly, you will be happier with your tools knowing that they can be put through some serious trashing and come out on top.




can you describe both how you acheive such edges and why one would choose one type over another?

Just did a video on this.
Basically, toothy edges are achieved by either stopping at a low grit, or skipping a lot of grits, like going from 5,000 straight to 15,000.

http://www.youtube.com/watch?v=lqsbO1w8rXE




Do you have several knives with different edge types for different tasks? or are you just shifting you average based on your typical task?


I think professionals in high-demand environments should have different knives for different types of tasks, sharpened appropriately. If I'm cutting 50lbs or carrots into sticks, or 80lbs of chicken breast, I want a knife that is going to excel at that task. One of the benefits of learning to sharpen as a professional is the ability to adjust your tools as you will be needing them to do different things. At home, I shoot for a happy medium.

Sarge
07-23-2012, 12:26 AM
Toothy and polished also relates to the stone used as well. (maybe you covered this in the video haven't watched it yet) The natural stone I'm using creates wonderful edges that I can easily slice up a dozen tomatoes for burgers or sandwiches and then still smoothly portion fish.

The paper test is nice to tell me how even the edge is the thumb nail test lets me know I've gotten sufficient bite to the edge. Food tells me that I wasn't deceived by my first 2 tests and my wires are gone. If I have a wire I run into trouble inside of an hours worth of heavy prep. No wires means I can go thru a day and half heavy prep or 2 days of normal to light prep.

Bryan
07-23-2012, 03:39 AM
Eamon, Many thanks for the video, extremely helpful.

Zwiefel
07-23-2012, 10:31 AM
I don't slam YOUR knife.

Yeah, I was trying to be humorous...didn't do a good job I guess :)

Eamon Burke
07-23-2012, 11:00 AM
Eh, so was I. I have that quality.

Zwiefel
07-23-2012, 12:38 PM
Just did a video on this.
Basically, toothy edges are achieved by either stopping at a low grit, or skipping a lot of grits, like going from 5,000 straight to 15,000.

http://www.youtube.com/watch?v=lqsbO1w8rXE


Very instructive video, thank you! I subscribed to your YouTube channel and will start going through those...thank you in advance for that!

In terms of creating these two kinds of edges (I think of it as a continuum from one to the other), what if I want a toothier edge? could I create that by grinding on a 10k stone, then taking it back to a 1k or 3k stone for a small number of strokes? Would that be a good compromise? Is there some specific benefit/detriment that noobs like me wouldn't expect?

Also, would it be sensible to strive for a more polished edge on one section of the edge and more tooth edge on another section?

Eamon Burke
07-23-2012, 01:25 PM
I wouldn't advise putting different grit edges on different parts of the knife, because there is a chance you might overwork one part and not the other, causing yourself grief.

This is really the interesting part of sharpening. My favorite all rounder edge is a 5k stone straight to a loaded strop(1micron or less). Also, natural stones do provide a very strange kind of edge, and I am just starting to creep down that rabbit hole myself.

I wouldn't generally suggest dropping grits, like 10k down to 1k, but rather skip grits, like 1k up to 10k with no in between. Basically, you won't take out the finish of the stone before it, just refine the teeth a little. Though I have on more than one occasion taken a freshly sharpened edge at work, and hit it with a 1200 grit ceramic rod, effectively grinding in a new, lower grit finish because I needed it--but once you do that, there is no easy quick way to bring it back up to a higher grit.

Zwiefel
07-23-2012, 07:35 PM
I wouldn't advise putting different grit edges on different parts of the knife, because there is a chance you might overwork one part and not the other, causing yourself grief.


I thought it was a pretty wild idea, but I've been surprised by "actually alot of people do that" type responses enough in life that I will keep asking :biggrin:


This is really the interesting part of sharpening. My favorite all rounder edge is a 5k stone straight to a loaded strop(1micron or less). Also, natural stones do provide a very strange kind of edge, and I am just starting to creep down that rabbit hole myself.

I wouldn't generally suggest dropping grits, like 10k down to 1k, but rather skip grits, like 1k up to 10k with no in between. Basically, you won't take out the finish of the stone before it, just refine the teeth a little. Though I have on more than one occasion taken a freshly sharpened edge at work, and hit it with a 1200 grit ceramic rod, effectively grinding in a new, lower grit finish because I needed it--but once you do that, there is no easy quick way to bring it back up to a higher grit.

So you are a fan of the ceramic rods? I thought these were generally for people who don't do their own sharpening?

Very interesting. Thanks for responding again!

Eamon Burke
07-23-2012, 09:02 PM
You just gotta get a good one. There are smooth glass rods too

Cutty Sharp
07-23-2012, 09:32 PM
Thank you for your response....Do you end up with bare sections on your arm? :wink: I've not been able to get one sharp enough to cut hair....always wondered if that was even real.

HHT= Hanging Hair Test - That is how you can spot a Knife Knut, bald patches all over their arms, or legs as I am running out of arm hair.

hahaha - Thought this was very funny, and true! :laughat: Actually, my wife keeps complaining about this. First, she cringes at the sight of knife-on-flesh. Then she sighs at the bald spots - which to me are a source of pride and a well-honed edge.

I'm trying to imagine a convention of knife knuts with scrappy bald patches all over their bodies. Another thought is, does having more body hair give you an advantage as a sharpener? The Japanese don't have too much, though usually more than other East Asians.