Wire edge that won't go away

[t1mpani]

That is precisely the technique that Murray Carter suggests in his video. Personally, this is one of the things were I deviate from Mr. Carter's technique. I had some burrs that I simply couldn't get rid off this way but that yielded with Jeff Clarks technique (raising the angle).

Oh really? Well, he probably came up with it first--and here I'd felt so clever. It hasn't failed to work for me yet, but sure as I say that I will now come up against the invincible wire edge.

 

[yuzuha]

Try a BG-42 blade that got burned at the factory while sharpening... grinding past that down into the good metal was the only time I got so frustrated that I just went AAAGGGGHHH and tried to slice the end off my stone with it (and much to my amazement, it worked). Now, the thing still wants to make tin-foil, but the wood block trick or the lengthwise stroke usually suffices.

 

[Cliff Stamp]

Well, that is exactly what I am thinking and one of the reasons why I am using a trailing stroke on very soft stones.

It doesn't seem to be supported experimentally though if you look at the high magnification shots by Lee or Verhoeven. There is though always the question of user technique in sharpening though. J.J. claimed (still does) that lubricant degrades sharpness and edge retention. Since this isn't published research we don't have the ability to request the actual data, but I find it hard to believe that he just made it all up. The problem with a lot of it is method. Did he for example check with people who can achieve high sharpness with lubricants and check their sharpness against his, or just do both himself? I for example don't do as well sharpening convex edge freehand on stones by moving the blade, instead I prefer to move the stone. I don't believe this method is inherently superior in general, it is just better suited to me.

-Cliff

 

[yuzuha]

It has to be more than non-zero though, it has to be enough to resist the counter force of the cutting abrasive. Consider if this was the case and the slurry which rode over the bevel does act to cut off the burr, or at least minimize it. Would it also not be the case that it would induce a similar grinding action directly against the edge itself and be blunting the blade and prevent sharpening?

-Cliff

Why yes... it does... it abrades the edge and the burr hanging off it. It doesn't square off the edge though since grains are free to ride up over or get sucked under the edge. Conjecture on my part, but this edge abrasion probably also chews off fatigued metal and helps expose fresh good steel on the edge. The degree to which it blunts the edge is probably proportional to the grain size and viscosity, though the grit is also being crushed smaller and smaller, but the abraded edge will still be sharper than the edge from a previous stone (ever looked at shovels that have been used on gravel or small sharp sand? The sand shovel gets sharpened a lot more... actually, I've known construction types that have sharpened their shovels by rotating them out to shovel sand for concrete for a while).

 

[Cliff Stamp]

Why yes... it does... it abrades the edge and the burr hanging off it. It doesn't square off the edge though since grains are free to ride up over or get sucked under the edge.

Yes however the same principle will prevent significant abrasion above the edge to a greater extent because a direct collision with the edge involves a much greater collisional force than a glancing blow above the edge and thus the abrasion against the edge would be more not less.

I've known construction types that have sharpened their shovels by rotating them out to shovel sand for concrete for a while).

This is different for a few reasons, primarily shovels don't have primary grinds so if you abrade the sides and the edge directly, the edge still gets more acute and will cut better. However if you try this on tapered profiles they will get duller because as the edge is impacted it thickens the taper far more than the sides reduce it. If you keep your shovel sharp by grinding an actual edge on it you won't sharpen it by shoveling sand or stone, I used to file mine on breaks and at lunchtime. File it down to sharp and then run the file lightly along the edge to give a bit of a flat for shoveling stone, leave it sharp for cutting sods.

-Cliff

 

[HoB]

All the "pictures" that we can come up here are conjecture to some degree. I think to really resolve this, we would video tape sharpening under a microscope, but my view is similar to Yuzuha's. I would think that a burr will trap more abrasive underneath than a clean edge. Its like having sand in your shoe vs dragging your toe through lose sand on the beach. I don't think the edge degradation to the edge, plowing into the mud is that big, but I think it is there and I think that Verhoevens images show it. It is just a matter of how you interpret them and what you are looking for and of course a matter of experimental technique. I think the problem is not nearly as pronounced on hard hones because the mud is well separated from the hone while on the really soft stones, the mud can imbed much more in the hone, so you have a layer that is half mud half hone. But if you look at Verhoevens images, you can notice that the edge leading images show some "dents" in the edge that the trailing edge images do not show. On the other hand, the trailing edge image shows more "fuzzyness" (kind of like a saw tooth pattern) than the leading edge pictures. Verhoevens interpretation is that debris is carried to the edge, but personally I think this is more due to the fact that the leading edge runs into the mud and the "fuzzyness" gets abraded.

But as I said, I don't think there is enough experimental evidence to know for sure and I thing either way of looking at it is resonable. As I said, I think we can know only for sure once we see some video that actually shows the abrasion process.

 

[HoB]

Oh really? Well, he probably came up with it first--and here I'd felt so clever. It hasn't failed to work for me yet, but sure as I say that I will now come up against the invincible wire edge.

Hey, there is such a think as independent co-discovery. You shouldn't feel any less clever, just because Murray Carter is using the same technique, rather they opposite I would say. After all they say: "great minds think alike" .

 

[Cliff Stamp]

I would think that a burr will trap more abrasive underneath than a clean edge.

The burr folds over immediately on the stone, almost as soon as the stroke starts, it will either be cut off or just fold over to the other side. I have had more success lately on problematic burrs by using very short strokes along with the usual clean hones and minimal pressure and elevated angles. Now maybe when it is in the process of folding over from the underside to the top this is impaired by the mud, but once it has folded I don't see how mechanically it could be abraded significantly for reasons noted.

In regards to pictures, I think they are interesting and worthwhile for various reasons, but they are not the actual way to measure the performance of the sharpening. This is done by actually measuring the sharpness and edge retention directly. One of the problems with pictures is that often the individual is assuming that a particular structure is superior without any data to support it. Now once you have established that the sharpness and edge retention is superior you can attempt to correlate this to a visual inspection.

I think a lot of interesting ideas have been proposed here it would be worth some experimenting. I have to do some work with fine edges with the M16's. I have been delaying it mainly as they are so annoying to sharpen because they burr persistantly, I should try it with 1200 dmt dry/water and fine waterstone mud/clean and see which way is the least frustrating.

-Cliff

 

[t1mpani]

Hey, there is such a think as independent co-discovery. You shouldn't feel any less clever, just because Murray Carter is using the same technique, rather they opposite I would say. After all they say: "great minds think alike" .

Well, that is certainly another way to think of it. Since it's Monday, I'll choose the great mind thinking myself---helps with facing the upcoming week.