[quote quote=“jendeindustries” post=5130][quote quote=“jendeindustries” post=5120]Here’s where we begin to search deeper into the rabbit hole 
Before I define “Robustness”, it would be better to answer about the smoothness of an edge and its impact on durability.
As with all things sharpening, it depends. Smoothness is only one of several factors that will determine the outcome to whether or not a smoother edge lasts longer. Geometry plays one of the largest roles, as well as the steel characteristics.
That’s all I can say for now - I will be back in a few hours to further answer![/quote]
OK - I’m back
Smoothness has two roles. The first, is when one sharpens for perfection. When removing all previous scratches at each level, the edge of the edge will ultimately become thinner and thinner while the “teeth” from the scratches become smaller and smaller (or less deep). This makes the edge feel smooth, as in approaching a shave-ready edge. Let’s call this a “true X grit edge”. For example, when sharpening for perfection up to 8K, this would be a “true 8K edge” because most/all of the scratches are 8K or 2 micron in size. That would also determine the the thinness/thickness of the edge of the edge at a given angle.
However, as the edge of the edge becomes thinner as the tip approaches the theoretical 0 width at the apex of the triangle, the steel and geometry characteristics kick in. Softer steel will roll with more ease, as will more acute geometry, giving the perception that the edge has been lost. While the edge of the edge of a “true higher grit” edge will be more fragile due to its thinness, rolling may not necessarily ruin the edge. Straight razors, for example, are easily refreshed/straightened out with a few ultra light passes on a strop. The trick with more refinement is to reinforce the geometry with microbevels and/or convexing to get them to be more sturdy. Then you run into the problem of having your edge geometry too obtuse for the task, which leads us to role #2.
The second role of smoothness is literally “polishing the grooves”, and would be the definition of a “more robust” edge in my mind. In this manner of sharpening, the idea is that the edge is shaped with coarser grits, and then those coarse grit scratches are then polished with the paste, slurry or mud - which is a mixture of loosened abrasive, binder and metal, but without the intention of establishing a “true” higher grit edge. For example, at 1K, the edge of the edge is theoretically ~16 microns thick. This is too thick for comfortable face shaving, which needs an 8K or ~2 microns thick edge to cut hairs without pulling. The 1K edge is a decent working edge because it is thick enough to withstand more of a beating without rolling (+ proper geometry and steel). If you polish the grooves of a 1K edge, you can push cut, and shave arm hair, but under the scope, you still have a very toothy 1K-ish edge. We have seen this with the 1K WEPS edge followed by the 1K WEPS diamond PASTE.
So if you’re still with me… Here’s how we can put some of it together in a VERY general statement.
WEPS Diamonds are “true” grit.
Shapton Pro stones are “true” grit.
Chosera stones create ~90% "true grit with about ~10% polishing of the grooves.
Naniwa Super Stones are about 90% polishing the grooves and 10% true grit.
With understanding the general “philosophies” of the stones, you can now begin to pick and choose series/stones based on what you intend to do and how you want you finished edge.
So a more robust edge could be a 1K edge stropped with some 0.5 micron paste or spray.
A better slicing edge would be step by step or small leaps up to 5K or more.
And everything in between![/quote]
Hey Tom…
I’m puzzled by some of what you say. I’ve seen you mention before that the thickness of the edge is based on the stone grit. If you look at some of Clay’s recent microscope pics… and also the pictures in Verhoeven’s study… http://www.bushcraftuk.com/downloads/pdf/knifeshexps.pdf … this doesn’t seem to be the case. For example, an edge sharpened on a 1000g Truhone wheel is 1m thick (p. 9), while you seem to indicate it has to be 16m thick. There are other examples throughout the paper. I do agree that a thinner edge is possible at finer grits (which the paper also supports), but maybe not to the level you describe? The edge doesn’t have to be as thick as the stone rating… it does “cut thru to the other side” (which I think is your reason that it should be this way)… but the result of this is why the edge is more jagged at higher grits… not necessarily thicker (at least not the thickness of the actual grit level). More of a “side view” vs. a “straight down view” way of looking.
Part of what makes an edge cut better is reducing this jaggedness… which is why honing a coarse edge will make it cut better. You can actually make a coarse edge cut better by making a 90 deg. pass over a fine stone (Harrelson Stanley from Shapton talked about this in a sharpening session I attended, and mentions it in one of his videos). Of course the tradeoff is you make the edge thicker, so a coarse edge cut across an 8K stone wouldn’t be as sharp as an edge sharpened to an 8K finish.
The other part that I wonder about, is that a fine edge is weaker, and has to be “reinforced” or made “more sturdy”. The perception is that a finer edge “dulls quicker”… but the argument could also be made that it merely “dulls down to the level of the refined coarse edge”… and will then dull at the same rate. In other words, an edge that is shaving sharp will, to the user, dull faster than an edge that would never shave to begin with, because the perception is less obvious. Also, while you mentioned convex edges more in passing… most are “stronger” simply because they’re sharpened at a much higher angle than a flat bevel. Obviously, a thinner profile is weaker than a thicker one, but it’s not as related to the finish level that you describe? Also, a finer edge will be more influenced by any burr or wire edge that remains, that wouldn’t be as noticed on a coarse edge. To put it another way… yes an 8K edge at 20 deg. may last longer than at 15 deg., but so will a 1K edge. (Both will cut better at 15 deg. though). This also helps answer the question of what angle to sharpen at.
It is obvious that an 8K edge will shave or cut better than a 1K edge… no doubt about that. Maybe, (and perhaps BassLakeDan’s testing machine will show… especially if it could be combined with some actual measurements of the edge) there is higher level of sharpness achieved across a smaller width of edge? In other words, maybe it’s possible that a .5m edge cuts 50x better than a .8m edge? (Just throwing numbers in as an example). So, while there’s not necessarily as great a change as you describe… even the smaller change results in a more obvious result? This combined with reducing the jaggedness of the coarser grit, is why it will cut better. Just food for thought.
