Sharpness Testing is a little discussed subject, oddly enough, here on this forum. I thought I would copy over a post or two where that subject has come up. Also it is a way of introducing the website that contains information about a "hobby project" sharpness tester that you can build yourself.


WayneReimer wrote:
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This is a clear demonstration that the long relied on "fingertip test" is not worth much. .. I'll keep everyone posted on how it stands up


I think what you might be saying is that testing a knife for sharpness in a reliable way can tell you a lot.. there is valuable information to be gained in assessing your sharpening methods when you start asking How Sharp Is It, and you are able to find the real and reliable answers to that question. If you are interested in blade testing on the hobby level you might want to drop by : www.howsharpisit.com/


wickededge wrote:
BLD - I'm about halfway through reading the new site. It looks terrific. Thank you for sharing with with everyone here. I can't wait to build one and add it to the testing I'm doing.


Well, Clay there are two ways to skin the cat, as you know. One is to do actual mechanical tests on the blade like CATRA and "the Jig hobby project".. the other way is to do what you are up to with the 800x scope, that is, just *look* at the apex and see what you can see.. actually your way has a lot to recommend it.

Of course the whole subject (of sharpness testing) can be argued/ explained/ discussed on and on/ for many days and many pages in a forum, and we certainly do not want to get near that right now, but one thing that your optical system can *not* do is return to you numbers, except for the reference scale nano-meters numbers. If you have a mechanical tester that returns numbers then you can get output like this from our latest excel spread number crunchers. Who knows if they mean anything, but they are sure fun to look at: www.howsharpisit.com/Elmax_ZT0560_Map.pdf

Quite interesting. I also checked out pretty much all of the site.
I think that the two, maybe three ideas need to be tied closely together.
If we can correlate specific sharpening progressions to a repeatable measurement, then actually see what is going on with the photomicrographs,and making adjustments on what we "SEE" ...then retesting with some repeatable quantitative numbers...

Heck, this could bring the whole sharpening business from the realm of art, into that of real science !!


I think I will build one of these things...

Phil

BTW, one thing... though hardly infallible, I can really with 90 + % determine when something will push cut or tree top hair by feeling the edge. I can feel a wire edge that can't be reliably seen at 100X. I don't think that after as many samples as I have tested in lots of years (50+) of sharpening...that I am delusional.
But I am an engineer. Quantifying things is what I live by...