Rounding the edge, or is it really refined?

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Jan 9, 2014
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I'm currently trying out nanocloth strops designed for the EP from CKTG combined with 1u and 0.5u CBN spray. I don't know whether to be impressed or feel like I :jerkit: a bunch of $$ away.

I've tried these on a Delica in VG-10 and a Leatherman Skeletool blade in 154CM. On both of these knives, after I finish with both the 2k and 3k tapes, I check sharpness with phonebook paper slicing paying attention to ease of slice plus sound. I'll take for example the Leatherman blade, when I finish on the 3k tapes I finished with light alternating pull strokes to try and eliminate any burr, and the knife was one of the sharpest I've ever done according to the phonebook paper test. Usually in my experience, only a pretty sharp knife will slice phonebook paper from the top of the page whereas you mostly see people in videos slice from the side of the page. On a less sharp edge, slicing from the top of the page results in mostly vertical tears in the page. Anyway, this edge would slice from the top with no effort, would wave cut with no effort and I was thoroughly pleased with it, plus there was virtually no sound when slicing, just that low pitched sound you get when it's laser sharp, not the high pitched sound of a burr and paper tearing.

On to the 1u and 0.5u:

With these final two, I only do light, alternating pull strokes, heel to tip. After both of these, the edge feels super smooth like glass when I do the 3 finger test, but will no longer slice phonebook paper like it did off the 3k tapes, and does more tearing when trying to wave cut. When trying to slice from the top of the page, the edge mainly slides across the paper and won't catch. And it definitely slides across glossier magazine paper. It's like I have to get the blade at a very exact angle for it to slice cleanly. Is this a result from the edge having less tooth at 0.5u than 3u resulting in the edge not being able to catch into the paper as easily? That doesn't make any sense to me, not when cutting paper. Or am I rounding the edge somehow? I understand the CBN is aggressive, but I use a drill stop collar and have checked the angles on these strops also, and they're dead on where they're supposed to be. Comparing the sound of slicing phonebook paper, it's just louder than it should be to me, and there's too much hang up in slicing and the edge sliding on the paper like the edge has a huge burr or is rounded, and it's starting to become frustrating. Comparing the slicing of these to a Para 2 I have microed at 20* with Sharpmaker UF rods and finished up with a Knivesplus strop, the Para 2 edge doesn't feel near as smooth, and not as polished, but slices like crazy at most any angle.

I was comparing the finished Delica to a new, out of the box Endura that may be one of the sharpest out of box knives I've ever owned. The factory Endura will slice and push cut and wave cut like the paper's not there. It's so good that I want to use it for awhile before putting my edge on it. On phonebook paper, the Endura just flat out blew the Delica out of the water, and the Leatherman blade too for that matter. So again, after the longwinded story, the strops seem to yield a pretty good polish and a glass smooth edge where rubbing the thumb across results in little bite. I've heard nothing but rave reviews about the CBN and the nano, but don't know really what to think. I'm interested to hear anyone's thoughts.
 
Sounds to me like you're rounding the edge. High polished edges should still bite during a three finger or thumb test, and should have no problems slicing or push cutting phone book paper.

ETA: The bite usually feels different though.
 
If the apex is truly crisp and not rounded, regardless of edge finish, it should still cut like a laser. In fact, at high refinement/polish, it'll do so very, very quietly, practically falling through paper under it's own weight. More so as the edge angle becomes more acute. As mentioned, the 'bite' feels entirely different, and may not be felt at all. Be careful in casual handling of edges like these; might not know you're being cut, until you see blood. Nice thing is, a cut from a very high-finished edge is very clean & smooth, and heals quickly. Not hard to see why a surgeon would prefer an edge like this. ;)


David
 
My angles are spot on, and my technique seems good...light, alternating pull strokes. What am I missing here?

I thought at first that some of the slop that exists when mounting these strops in the pivot arm could be the culprit, because these strops are not on a typical blank like the blanks for the tapes where 2 aluminum plates are bonded together. The nano strops are one single piece of aluminum with the nano bonded on one side so it can be tricky getting them to tighten properly in the pivot arm. They would go in and out of the arm much easier IMO if the nano was mounted on a typical tape blank. However, I checked the angles and they were in fact spot on.
 
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The slipping/sliding cutting performance in paper still suggests rounding of the apex. Considering other variables, like the different mounts, if anything is moving too much during the stroke, or if the nanocloth is doing anything to make it bunch/roll around the apex during the stroke, that could potentially round off the apex. I haven't used nanocloth, and so I don't have a feel for how much 'give' there is with it, under some pressure. If there is any give/conformability, I'd suspect that first; I'd lighten pressure even further to test for this. If it came down to it, I might even try a different substrate, like simple paper (thinner is better, firmly affixed to the backing), with your compound and see if it produces a different result.

Another thought is a somewhat less than complete apex in prior stages, with a thin & sharp burr doing most of the cutting there, giving misleading impressions about the edge's sharpness. Following with stropping, if that burr is removed in doing so, the underlying geometry of the apex may be a problem. I might test for that by scrubbing some hardwood, cross-grain, against the edge off the tapes. See if that removes any burr, then see how the edge cuts the paper after doing that (and before attempting anything with the nanocloth). If a sharp burr was doing most of the cutting, atop an apex that maybe isn't perfectly crisp, the cutting performance would likely fall off quick after removing the burr. If so, I'd go back to honing with prior grits, making absolutely sure a burr is formed and verified from BOTH sides of the edge, then go very, very gently about removing it with the tapes and/or nanocloth strops.


David
 
No the nano might bunch maybe a mm or so at the very end of the blanks, nothing severe. The part actually contacting the edge is nice and flat. In regards to forming a burr, I check the edge thoroughly from both sides at each grit, and I take care to remove as much as possible before progressing in grit by doing light, alternating strokes until no burr can be detected. I prefer to have the least amount of burr possible before moving up in grit.

The leatherman blade was finished with a 20* microbevel with the EP and apexing on both sides was easy and no issue. As far as gently removing it with the tapes and strops, that's precisely what I do. I don't do much of the sawing motions I see a lot of people do with the tapes. I will do both sides evenly with light pressure and end up with light, alternating pull strokes. This usually ends up with a very sharp edge off the 2k and 3k tapes. And on other knives I've done, this is where I'd finish on my Knivesplus strop block for an even sharper edge. It's the nanocloth strops that are throwing me off, and I'm basically using gravity as pressure and a pull stroke. One stroke per side, alternating.

If I could figure out a good way to hold it, I might try stropping with these freehand to see what happens.
 
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Well theres a couple factors here.

15k and 30k is kind of a "dead spot" for feeling an edge , its not toothy , it just feels smooth , but is not yet refined enough to feel sticky# Cutting performance in this area is not something im terribly familiar with as I typically take my knives #I#much#/I# higher in terms of refinement# But it should definitely be cleanly slicing paper here#

While I don't think your rounding your edge , it is possible# There could be enough play in the EPA to minutely change something enough to round an edge off# Not likely , but possible# Why don't you try knocking the angle down 1/10 of a degree and see what happens#

Nanocloth has virtually no give at all# It just wont deform its too thin , and the bare cloth alone has zero affect on an edge#

Some possibilities to ponder

-Fine Burr: CBN on Nanocloth is extremely aggressive and can leave a burr quickly , alternate sides frequently and maybe finish up on some bare leather#

-Play/Rounding : Inspect your EPA to see how much play is occurring , even the slack in the guide rod/pivot could do it if theres enough

-Toothines vs Smoothness: The EP films and stones leave a very toothy polished edge , the CBN will start making things quite a bit smoother with less bite at this level #go a little further and all the sudden the knife gets "sticky" and becomes a real performer#

-Consider investing a decent scope like the Veho so you can better trouble shoot whats going on , well beyond what we can make out with a loupe at this level of refinement#


 
No the nano might bunch maybe a mm or so at the very end of the blanks, nothing severe. The part actually contacting the edge is nice and flat. In regards to forming a burr, I check the edge thoroughly from both sides at each grit, and I take care to remove as much as possible before progressing in grit by doing light, alternating strokes until no burr can be detected. I prefer to have the least amount of burr possible before moving up in grit.

The leatherman blade was finished with a 20* microbevel with the EP and apexing on both sides was easy and no issue. As far as gently removing it with the tapes and strops, that's precisely what I do. I don't do much of the sawing motions I see a lot of people do with the tapes. I will do both sides evenly with light pressure and end up with light, alternating pull strokes. This usually ends up with a very sharp edge off the 2k and 3k tapes. And on other knives I've done, this is where I'd finish on my Knivesplus strop block for an even sharper edge. It's the nanocloth strops that are throwing me off, and I'm basically using gravity as pressure and a pull stroke. One stroke per side, alternating.

If I could figure out a good way to hold it, I might try stropping with these freehand to see what happens.


I'd go back to the original edge angle setting, ignore the microbevel shift. Sounds like there is a bit of rounding going on, you might be able to pick it up by not accounting for your microbevel, or not using one in the first place and let the nanocloth apply a slight microbevel. Next step is to apply even less pressure than gravity. The cloth is guaranteed to not impart any of its own abrasive or burnishing qualities - if its a fabric, even a non woven one, there is likely some give to account for. The stuff is a bit pricey, I don't think I'd want to use a Sharpie on it, so that's out...

Martin
 
Ok, I think I was able to work everything out. For the Leatherman blade, I took the strop and set it up so I was able to freehand. After less than a minute of freehand stropping, the blade was noticeably sharper. I set the EP back up for the Delica and tried again. This time I used a technique where I would go to heel to tip and then another stroke tip to heel alternating sides. I've heard of a similar technique before where you take the scratches in both directions when finishing up at higher grits to "chop up the burr" and supposedly make it easier to remove. How valid that claim is, I don't know, but in the case of the Delica, it seemed to work and the edge ended up nice and sharp. I set the EP up for the Leatherman and tried the same technique, and it definitely didn't get any less sharp than when I had freehanded. So who knows if the technique actually worked or not, but something worked I guess, and both edges got pretty dang sharp in the end.
 
i dont know if alternating directions works but i know that at any grit i want to finish with the "scratch pattern" oriented where i slice. for my kitchen knives i've observed that it made a difference in the bite even at a 10k SS plus 0,5 mic stropping. try finishing from tip to heel, maybe it wont change anything but its worth trying.
 
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