Thread: Harshness and Final Bevel Shape

Originally Posted by JimmyHAD

Edit, Kevin, I had to work to find part 2 here but glad I did. The natural edge looks 'better' to me at 3,000x. I wonder how the one will hold up as opposed to the other ?

(as long as we're talking about controversial stuff here anyhow)
That picture sure looks like visual confirmation of razor teeth...

Originally Posted by HNSB

(as long as we're talking about controversial stuff here anyhow)
That picture sure looks like visual confirmation of razor teeth...

As I learned a long time ago.... when I limit myself to 30k magnification my honing improves dramatically.

Originally Posted by JimmyHAD

I know no more than you on the woodworking but the synthetic stones that we use to hone our razors, Shaptons, Nortons, Naniwas etcetera are made for woodworkers. We have adapted them to our pursuit and since steel is basically steel they work well..... IMO.

What makes me suspicious is the fact that they have a grit rating for the nat stone.

Originally Posted by HNSB

(as long as we're talking about controversial stuff here anyhow)
That picture sure looks like visual confirmation of razor teeth...

I think they could be called teeth but not as typically described as a direct result of scratches continuing to the edge

Originally Posted by HNSB

(as long as we're talking about controversial stuff here anyhow)
That picture sure looks like visual confirmation of razor teeth...

Or just the jaggedness left from the steel fin tearing away from the edge.

Verhoeven has shots at 3,000x taken from all angles (each side and head-on), and it's apparent that what looks like "teeth" at low resolution are either remnants of a burr (visible from the other side or from an oblique angle), or places where the steel has broken away from impact with an abrasive particle (viewed head-on and at a higher resolution it's as toothlike as the cliffs of Dover).

The idea behind "teeth" as described by the old textbooks and here on this forum was that the grooves of the abrasive would leave sawlike teeth in the steel as they ran off the bevel. Seemed logical enough, the high ridges between the grooves sure seemed like they should jut out past the low spots between the grooves, and sure enough you can see "teeth" in the steel from our low-powered loupes and microscopes. It's just that they don't appear to exist when viewed with a really good microscope, what we see as "teeth" are really glints off the burrs that appear larger than they really are because of the way our eyes and CCDs handle bright spots - the "teeth" caused by the honing marks are simply mirages. At the edge, the high ridges and low furrows left by the abrasives tend to break off semi-randomly, depending on the underlying grain structure of the steel and what sort of swarf hit that part of the edge on its path down the stone. The traditional theory of teeth only seems to hold up at very coarse grit (< 1000).


BTW, what's with the grooves running parallel to the edge on the shapton blade? That looks like the blade was steeled at some recent point, which explains the odd "torn" look to the edge (Verhoeven's photos of steeled blades show the same appearance of parallel grooves and torn edge).

Originally Posted by mainaman

Are the stones used for woodworking tools the same as the stones used for razors? I am not convinced that a chisel needs to be finished on a razor quality stone to do its job properly, may be I am wrong

It depends; so the answer is sometimes yes sometimes no. Most of the time an 8k edge is all one needs. Sometimes even a 5 or 1k is enough.

If you use the natural surface of the wood without any sort of protective finish, as in traditional architecture of Japan you want that to be very smooth. Not only does it create a natural shine, it weathers far better that say a 320(++++) grit sanded surface (or more coarsely planned)

As well using soft wood requires a much more refined edge than what is typically required for hard wood.

Originally Posted by kevint

It depends; so the answer is sometimes yes sometimes no. Most of the time an 8k edge is all one needs. Sometimes even a 5 or 1k is enough.

If you use the natural surface of the wood without any sort of protective finish, as in traditional architecture of Japan you want that to be very smooth. Not only does it create a natural shine, it weathers far better that say a 320(++++) grit sanded surface (or more coarsely planned)

As well using soft wood requires a much more refined edge than what is typically required for hard wood.

Thanks,

I am not sure what type of finsih is needed for a chisel/ plane to get the best of it in the most demanding situation. There are fine finishers such as what we use for razors , and then there are medium finishers, which are finer than 10k (I have one of those) but nowhere near a quality Asagi. In that blog there is no mention of what type of stone has been used, I wish they were more specific, because their statement is pretty bold.

[QUOTE=Kingfish;557693]My last word on this just to restate, microbevels were not even the main point of the post. Very few people can create a perfectly flat bevel on a flat hone even if they wanted to. Here are some reasons why:
1. Slurries pile up in front of blade, create convex shape.
2. Nervous system and skeletal system do not move in perfect lines, meaning that sometimes there is more pressure on the hone than others causing flex in blade, create convex shape.
3. Softer stones by their very nature give and release abrasives quickly, create convex shape.
4. Small imperfections on the surface of the hone contact leading edge first making it wear faster than behind, create convex shape.

If all the above factors are not valid, then my knowledge of sharpening is very flawed.(it could be)

I think you came up with an interesting thought experiment. Without being able to really, really see what is happening we can only use the "face factor" to deduce what has happened.
I think the bevel is important in two regards. If we consider the bevel to be the "back edge" and have sharpened flat or even "Kingfish flat" per your descriptions above, the finish surface of the bevel continues to the very edge. It is not the polish of the bevel that gives us a smooth feel it is that polish continuing out to edge.
Of course we could by a number of means ruin the continuity/ straight line of the edge as we near completion. The bevel would remain fully polished but the edge would feel harsh, prickly. (It has "set" like saw teeth as tint chips do not seem to be enough to make harshness)
The other important factor is the slope. With equal edge dimension the more acute angle encounters less resistance, requires less force and so feels sharper. By various means we could impart an obviously convexed bevel profile which would require us to raise angle of approach, or in the extreme actually create a "dull" feel whether or not the edge dimension is optimal.

my statements are certainly elementary, may not be needed to compliment your understanding, but what other factors could come into play when considering the bevel

Originally Posted by kevint

I think they could be called teeth but not as typically described as a direct result of scratches continuing to the edge

Ah. I misunderstood what was meant by "teeth". By that definition, I guess those pictures are definitive proof that teeth do not exist.

Originally Posted by mainaman

Thanks,

I am not sure what type of finsih is needed for a chisel/ plane to get the best of it in the most demanding situation. There are fine finishers such as what we use for razors , and then there are medium finishers, which are finer than 10k (I have one of those) but nowhere near a quality Asagi. In that blog there is no mention of what type of stone has been used, I wish they were more specific, because their statement is pretty bold.

By boldness I asume you mean the grit. That it was stated to be around 12k or HStanley reporting that nat abrasive tops out at such a low figure. One of those perhaps.

You can follow or add to some more discussion of the blog at japansestoolsdotcom forum.

Personally I am happy when i can improve the edge given by my coticule. That happens off my suita and again from asagi. I dont have synthetics of sure grit to know whether i can tell the difference between 12, 16, 30k. But I have nats that may (or maybe not) in that range.
I think I know) that a hard stone like an Escher or Asagi give a super smooth edge. Whether this is a result of very minimal slurrying or an ultimate fine grit rating I am unsure. I have seen Escher's rated at 12k on the conservative end. Asagi sometimes nearer 45k than 30. But I think it entirely possible if we could find an asagi singular grit it may well measure 10-16k shapton particle size-which is not the important thing.
In the end what we get depends a great deal on the razor. Ultimately I accept the fact that I dont know what finish is needed to get the best of it in the most demanding situation, even though i go on and on. I am my own biggest variable, so I do what I can, hoping for better than last time.