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tk59
05-23-2011, 04:00 PM
I generally use pretty fine edges so they get dull quicker but they seem to respond better to frequent stropping than coarser edges. On the occasion that I actually do compare edge retention, I'm basically talking about how fast a highly refined edge loses that feeling of ultimate sharpness which is generally pretty quick. If I was looking to see how long I could cut onions without smashing them, my impression would likely be totally different and the geometry of the blade/edge would start to take over. I'm wondering what everyone else is evaluating when determining edge retention.

Michael Rader
05-23-2011, 04:17 PM
In my opinion, Bill Burke's knives have one of the best blades for edge-retention with his triple quenched 52100. I believe that Chef Niloc did a review of one of Bill's knives recently, and made comment on that so maybe he can chime in here again and compare a bit how he judged that. One test I am aware of is the cutting of rope on a digital scale. They cut until it requires too much (of a pre-determined) pressure. Maybe one knife cuts 165 - 1" ropes at 20lbs pressure while some other knife cuts only 51 at that pressure.
-M

Marko Tsourkan
05-23-2011, 04:24 PM
...
One test I am aware of is the cutting of rope on a digital scale. They cut until it requires too much (of a pre-determined) pressure. Maybe one knife cuts 165 - 1" ropes at 20lbs pressure while some other knife cuts only 51 at that pressure.
-M

That is the test that I would like to do and I think it is a perfect test to compare performance of different knives in approximately same hardness range and sharpened to the same level. Moreover, since ropes vary in their composition, it's good to buy a lot of one kind and keep using the same rope when comparison with previous tests is important.

M

Cadillac J
05-23-2011, 05:08 PM
Really good point TK, and as a home cook and avid sharpener, I share similar views as you regarding retention.

There is just this point where I feel my edge needs to be invigorated with stropping or a polishing stone as I crave that freshness, but if left alone I know that it would still cut for a long time(which it pained me to test previously), and would be considered very sharp thereafter by many other people. Once again, I think it comes down to what you consider to be sharp and your preference of how you want your knife to feel when cutting.

I will strop a fresh edge after only two(sometimes just one) cutting session to preserve that feeling on the initial cut, even though the edge doesn't really need it at all. Why are we so damn crazy?

Larrin
05-23-2011, 05:48 PM
In my opinion, Bill Burke's knives have one of the best blades for edge-retention with his triple quenched 52100. I believe that Chef Niloc did a review of one of Bill's knives recently, and made comment on that so maybe he can chime in here again and compare a bit how he judged that. One test I am aware of is the cutting of rope on a digital scale. They cut until it requires too much (of a pre-determined) pressure. Maybe one knife cuts 165 - 1" ropes at 20lbs pressure while some other knife cuts only 51 at that pressure.
-M
I thought Colin reported the DT ITK output the Burke. I can't find it though.

Lefty
05-23-2011, 06:59 PM
What would you know about the itk? ;) Jk!
For the rope test, is the rope laid across a cutting board or tethered at both ends, in mid air? If it's the latter, wouldn't length of rope even play a part in how much force is needed to cut through it?

stevenStefano
05-23-2011, 07:32 PM
The way I test if the knife is sharp enough is to cut a tomato in half and put it on a chopping board cut side down. I then try and cut through the skin, and depending on how much pressure is needed, I know how sharp it is. When I do it my Masamoto always does it a little better than all my VG10 knives

Larrin
05-23-2011, 08:38 PM
What would you know about the itk? ;) Jk!
For the rope test, is the rope laid across a cutting board or tethered at both ends, in mid air? If it's the latter, wouldn't length of rope even play a part in how much force is needed to cut through it?
The rope weight is relatively insignificant, especially since the stopping point is difficult to pinpoint, and the weight of the rope should be about the same across the test. Anyway, as long as the test is the same each time the results should be comparable. However, due to differences in rope and each tester the rope test is difficult to compare from multiple people. Another problem with the test is that thinner knives do much better. In part this is because the thinner knife requires less to begin with, and for another the thin knife cuts better when dull. This demonstrates the superiority of thin knives in many situations, but can be misleading when comparing different steels, heat treatments, or knives made for different or very specific applications. One more problem is that rope isn't necessarily a realistic test for knives that will ultimately be cutting meat and vegetables.

Lefty
05-23-2011, 10:11 PM
Great point Larrin!
Thin would be a huge advantage in a test like this, which really makes testing steel types head to head difficult.
One steel might be better than another at a more obtuse angle/ thicker blade, while the opposite could be true for another. Not to mention, different steels respond differently to toothier finishes, etc.
I think steel type alone is less Important than the knife as a whole. In other words, we should really worry about which knife we all prefer and find has good attributes in our hands.

MadMel
05-24-2011, 12:04 AM
For me, edge retention = how long I can get away without sharpening on a stone and still go through 6 cases of tomatoes without juicing them.

tk59
05-24-2011, 01:14 AM
For me, edge retention = how long I can get away without sharpening on a stone and still go through 6 cases of tomatoes without juicing them. I understand that but what are you doing to the tomatoes? Small dice or slices or chunks? This can lead to a lot of variation in the number of cuts/board strikes per tomato. How big is a case? Do you steel/strop/rod your knife intermittently? I hope you understand, I have a hard time really getting a feeling for what you (and other pros) mean when you make statements like this.

JohnnyChance
05-24-2011, 01:35 AM
Im not really sure. It is very hard to describe, and of course very subjective. Everyone has a different idea of sharp, therefore everyone is going to have a different idea of dull. I don't sharpen nearly as much as it sounds like some pros here do. I usually sharpen once a week, rotating through out that week between about 3 knives, but my knives would probably still be called sharp by my coworkers. I usually do not feel the need to strop or touch up the edge on my Mac black ceramic hone.

I like cutting paper while sharpening. It helps me find dull sections or remaining burrs. So I would say I would consider a knife dull when I could not cut paper after trying to bring the edge back with strops or a ceramic rod. If I can't do that, then it is time to go back to the stones.

MadMel
05-24-2011, 01:54 AM
I understand that but what are you doing to the tomatoes? Small dice or slices or chunks? This can lead to a lot of variation in the number of cuts/board strikes per tomato. How big is a case? Do you steel/strop/rod your knife intermittently? I hope you understand, I have a hard time really getting a feeling for what you (and other pros) mean when you make statements like this.

Lol. Ok to be more exact, those are Roma tomatoes, skin on, total of 6 kilos, seeded and diced. I steel before I begin cutting, if my knife was previously used. If it was a fresh edge, I'd just get on with it. I do not steel/strop/rod intermittently unless I start getting tomato juice, and that would mean it has to go to the stone soon. And if it is of any importance, I do not rock cut, and my chopping board is plastic.

NO ChoP!
05-24-2011, 12:00 PM
I dont think anyone in a real pro setting is pulling out a tomato or a piece of paper to test their knifes sharpness. Isn't it just a feeling? When I use a knife on the protein station on a weekend night (going in perfectly sharp), after slicing proteins including grilled hanger steaks, blackened duck breasts, coffee crusted pork tenderloin and pan seared airline chicken breasts, all night I can "feel" the meat pull and tear a little. As soon as I have time, I'll strop on mid grit stone to refresh a toothy edge. As far as blades used to do vegetable prep (tomatoes, etc...), I use a much more refined edge and will strop on diamond loaded leather frequently.

I break out the stones every Monday, (not always for the same knives, and often for others knives as well).

With certain knives what CaddyJ said is right on. My Masamoto, Takeda and Kono HD will keep an "adequate" edge much longer than say, my CCK cleaver or certain stainlesses, which starts sharp and just gets dull fast.

I think once you experience a good quality knife with a perfectly keen edge, you have expectations, and are no longer happy with "adequate'.

Lefty
05-24-2011, 12:04 PM
I think once you experience a good quality knife with a perfectly keen edge, you have expectations, and are no longer happy with "adequate'.

That sums it up nicely.

Avishar
05-24-2011, 12:46 PM
The psychological effect of marginal/relative sensitivity also is at play here! If you take a hair splitting edge and it tapers down to a paper cutting push cut edge, it will feel as if it has dulled more than a coarsely sharpened, toothy Wusthof that is relatively close to a dull (by most of our standards) edge: think of a knife that is sharpened to a 2 going to a 1 vs a knife sharpened to a 9 going to a 5.

Given this, when my knives fail to do the task they are intended to do in a manner that is comfortable for me I think it no longer retains its edge. For example if my Western Deba fails to cleanly split a stack of white corn tortillas with minimal downward force, or begins to tear through bacon instead of slicing it, then I will take it to the stones. If my Honesuki no longer glides through the chicken along the ribcage and exhibits tears, I feel its edge is no longer retained, and thus it is time to resharpen. Like most things in life, I find that its good to use common sense and judge case by case, avoiding a universal rule!

MadMel
05-25-2011, 12:45 AM
Like most things in life, I find that its good to use common sense and judge case by case, avoiding a universal rule!

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