Stroke Direction

[Leo Barr]

Do you think that say if you allow a small amount of convexing to occur that the blade has a chance of retaining albeit slightly inferior sharpness for longer than a total “V” profile ?
I suppose a great part of that answer would depend upon the use of the blade and once again the quality of the steel so I guess there is always going to be two answers one to pass the ultimate sharpness test and the second to retain a serious level of sharpness.
These sharpness tests will certainly help the WE owners no end but there will be so much more testing to do to answer all the questions of how to sharpen for a purpose .
Food preparation requires various forms of sharpness from a toothy edge , a strong edge through to a razor type of edge and identifying what edge is best suited is not always that clear when we are sharpening for someone else. It seems the more we dig the more complicated the answer becomes.

[Jamey Howard]

I wondered how long it would be before convex fans started piping up in defence of a rounded edge 🙂

[wickededge]

Interesting Clay, but not unexpected I guess.
Did you do any tests with the sharpness tester to see if the changes in the HHT correlate to anything measureable with that device?

I just ran the numbers from the sharpness machine and found a pretty nice correlation:

Blade stropped 2° below the sharpening angle required an average of 186g to rupture the tape and consistently scored HHT5 .

Blade stropped at the sharpening angle required an average of 204g to rupture the tape and consistently scored HHT4 with an occasional HHT5.

I think there is a way to test the durability of the edge with the two different techniques using the sharpness tester. I’ll need to set up a second blade so I can do side by side comparisons, one stropped at angle and one stropped below. With a high number of sharpness tests in the same place on each blade, I should be able to see the loss in apex point sharpness over time. I can also degrade the edges at the same rate by keeping the same load on each and moving the blades along their y-axis. Repeated motion under load should degrade the edge measurably and I can then perform the sharpness test again along with the hanging hair test to see which blade, if any, held up better.

-Clay

[Mark76]

Clay, very interesting results! It would be interesting if you could do a sharpness test as well before you do any stropping. In that way we can see what the effect of a little bit of stropping is.

I assume you are using a leather strop? I’m also interested in what a harder material, like balsa or glass-mounted nano-cloth would do.

Molecule Polishing: my blog about sharpening with the Wicked Edge

[cbwx34]

Some Faith Restored! 🙂

I’ll post a whole write up soon, but for now I’ll leave the following: I took a blade up through 10k Chosera and then on to the .25um kangaroo strops. At 10k it wasn’t really popping hairs in the hanging hair test, but after the roo strops, it was consistently returning values of HH4 and HH5 (reference here). From there, I took it to the sharpness tester and got great results: 34% less force than with the 100# plates.

How did you solve this (or did I overlook the answer)?

I was about to start to sharpen knives on cinder blocks haha

😆 😆 😆

[Josh]

There seems to be done theories out there and much debate about stropping. I believe it would be beneficial to research this more…

Namely:

1. repeated stropping for maintaining weakens the edge because you are bending the metal back and forth. Edge retention then goes down with each subsequent stropping as the metal gets weaker. But how does this affect a fresh edge that is stropped after lowering the angle 2 dps?
2. strops are worse than stones because they: cut slow, load up and become ineffective, and fresh abrasive is never released
3. “If stropping improves sharpness then your honing failed to produce a good edge.”

If you’re game Clay (I know you’re busy) , or any of you guys that have a testing jig, I would like to experiment start looking into what place /roll strops are most effective at and how they affect the edge, in a positive or negative way.

References :

http://www.cliffstamp.com/knives/forum/read.php?7,6571
http://www3.telus.net/BrentBeach/Sharpen/Stropping.html

[wickededge]

Hey Josh,

Thanks for posting these links. There is some interesting discussion in Cliff Stamp’s thread and he definitely gets great results with his methods. One thing that jumps out at me is that the kind of stropping and the types of abrasive compounds discussed in Cliff’s thread are very different from the way stropping is accomplished on the Wicked Edge. Brent Beach’s article suggests something similar in that he recommends using a jig and clearly asserts that a quality graded compound is needed for good results. That said, both bring up some great questions that I think we can test pretty easily. The sharpness testing machine may be of some use though the kind of edge wear it tests for is very specific and doesn’t necessarily translate well for some kinds of daily use. It might be instructive to try and design an experiment that allows us to cut everyday materials while limiting the variance in force and technique as much as possible. One example to test edge retention of stropped vs. non-stropped blades is to sharpen two identical blades at the same angle and to the same level of finish e.g. 1000#. One of the blades should then be stropped (stropping angle and grit can be varied to test different combinations). The blades should then be used to cut same-length strips from the same batch of cardboard until they fail to cut cleanly. Once the blades start snagging on the cardboard, we could consider them to have reached failure. Counting the number of cuts until failure for each blade will tell us which had better real world edge retention. The cardboard should be held up by hand, not laid on a cutting surface so that pressure differences between cuts are minimized.

-Clay

[wickededge]

One thing that this thread, with all the observations of all the different contributors, highlights for me is that there are very many knife sharpening strategies, even within a single platform like the Wicked Edge. Different strategies create results that are optimized to specific tasks or goals. In mapping out a sharpening strategy for a given knife, it’s important to consider a few factors:

How are you planning to use the knife? Which angle, finish etc… will give you the best performance?
How often do you want/need to touch up the edge?
Which is more important to you, extreme sharpness or edge retention (not necessarily mutually exclusive)?
What role does aesthetics play for you in the sharpening of this knife?

The decision of whether or not to strop, which grits and substrates you’ll employ and with which techniques should be driven by the answers to these questions.

-Clay

[Ken Buzbee]

1. repeated stropping for maintaining weakens the edge because you are bending the metal back and forth. Edge retention then goes down with each subsequent stropping as the metal gets weaker. But how does this affect a fresh edge that is stropped after lowering the angle 2 dps?
2. strops are worse than stones because they: cut slow, load up and become ineffective, and fresh abrasive is never released
3. “If stropping improves sharpness then your honing failed to produce a good edge.”

I agree with these points, Josh. They reflect my experience. To that end I very rarely ever strop a blade these days.

Clay raises some great points in that the angle, finish, steel (did he mention steel?) and use are all factors here.

Most recently I’ve backed off going for that ultimately refined edge on my EDC knives. Primarily these are S30V or VG10. I tend to take them to 24°-26° inclusive and used to take them through the μ ceramics. These days I’m stopping at the 1200 Atomas and have been very happy with that edge… for a longer period. They “feel” just as sharp and they slice a bit better.

Now, on my most recent acquisition, a Super Blue Nakiri I’ll go well into the Chosera/Superstone line to either 8k or 12K (haven’t decided my preference there yet) as it tends to be mostly push cut. I might try stropping that one at some point, we’ll see.

Ken

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