So jumping from a 240 grit edge to a 3k stone will give you a finish looking like a 3k edge, but a poor one indeed.
Ken, in context I was replying to a comment where Sadden noted that failure to eliminate apex scratches would cause issues with polishing, and I agreeed and noted an example of how that could be compounded by current stones. I was not describing a sharpening method which was claimed to be ideal, or even advocated for general use.
However if I was for some reason limited to a 240X and 3000K SPS-II stone it is easily possible to form the edge without this issue and I have described it in detail on the T0.1M forum with the 50X shots. The process is :
-hone to dry on the 240X and stop at the point of light reflection being eliminated
-the edge thickness is just under 20 microns at this point
-hone with the 3000X SPS starting with a saturated stone and honing to dry
There is no need for magnification at any stage in the sharpening, for reasons noted. I did this experiment for many reasons, one of them was to see if I could 2-stone like Carter but over a wider range of applications and the 240X is much more capable of removal of damage than the 1000 King he uses, but it then requires more work to clean up. Thus the technique to hone-to-dry which allows greater speed of material removal and a finer edge finish than the 1000/6000 combination he uses.
As a side note, if the steel is very prone to burr formation and especially if it is very easy to grind it may be necessary to put a burr minimization step in between and this can be done with either stone depending on how severe the problem is produced. Of course the SPS stones are not special in this regard, any two stones can be used in the same combination and it works on any steel, not just the easy to grind ones, I have done it all the way up to 121REX at 70 HRC and I have done it with non-specialized stones. Though of course nicer stones make it easier and if you can afford them there is no reason not to use them aside from some self imposed challenge.
ken123 wrote:This is a particularly abrasion resistant steel (high vanadium carbide content) and cutting this steel with a stone with softer abrasives does little more than wear a stone down, producing an inconsistent bevel angle in the process of dishing the stone.
In regards to the Bester 700X, I took the 121 REX down from ~0.010" to full zero with no visible hollow in the Bester. The wear in the stone induced an edge curvature of ~1 dps in the primary bevel. Of course the stone was used in a staggered pattern. As for its use, I had not used the Bester on a high carbide steel and wanted to explore at that carbide level it was outperformed by the more costly SPS-II series stones and as well to compare the grinding times as a function of abrasive and the longer the pass count the more accurate the comparison.
Had I just wanted to do it in the shortest time I would have power sharpened it with coolant, but again, this wasn't about the fastest sharpening time.
ken123 wrote:What you are describing 'academically' is referred to in statistics as 'covariance'.
I am not talking about covariance which is the correlation between variables.
I am talking about bias as in measurement bias, any influence which shifts the sample statistics away from the population. A burr is just the extent to which the edge is formed less than ideal and is therefore biased because of various influenced from the true value (perfect apex). I have also been using the exact same definition for 20 years.
Again if you don't like it no issues, use whatever term you want.
ken123 wrote:So in the first micrograph, there is more than a simple burr present. There is significant edge damage too.
The damaged steel has long been removed, what you are seeing is the fatigued steel which was under the original damaged edge not being able to form properly as it is over strained. To be clear that always happens on some level, the exact same thing will happen on any edge, you just have to go to higher magnification shots to see it. Now to be really clear we are talking about traditional sharpening, it is possible to sharpen and form edges on a atomic level which are perfect of course.
ken123 wrote:Here removal of the damaged edge is best achieved with ...
As before, I have stated my position and the physics behind it, it is also very easy to see if you file sharpen as the same thing will happen but you can then see the burr visually and what happens if you just alternate sides compared to cutting it off. As noted, I rarely do 90 cuts after the initial destressing, in fact since I don't burr sharpen I rarely have to remove a burr at all.
As for the micro-bevel, when Clark first proposed his method a number of people made the same objection, however the bevel which is formed at the 1-2 passes which are needed to remove that burr is so small it isn't even seen under 50X magnification, it can not even be detected under very fine measurements of sharpness.
ken123 wrote:You are simply causing a clogged stone and reducing the stone's efficiency.
Yes, because at that stage the maximum rate of cutting ability is no longer what is desired.
Ken, just to state the obvious, not everyone has a wide range of stones, this data might not be of interest to you, fine, it is of interest to me and because of this and other experiments I can do things like this easily :http://www.youtube.com/watch?v=5At3NtNKHFA
That is the edge right off of a 24 grit stone, which readily cuts fine papers, shaves, and does other high sharpness work and it is achieved with techniques such as described in the above and on a knife which has far less than ideal steel and thermal processing.
Again, this might not be of interest to you, fine, please realize that lots of people can not afford high end stones, or a wide collection and some people are even interested on how to field sharpen on very non-ideal abrasives.
The ability to take a knife from completely dull with the edge cut off to formed to shaving sharp in ~two minutes with no sharpie, no magnification, with a very coarse stone (and as well I did the same thing with an ordinary red brick) is again of interest to a lot of people.
And yes, I also sharpen with regular hones in more traditional methods and I have natural and synthetic stones of all makes and models and power equipment and have used high end jigged systems as well.