Effect of oxidation on sharpness

[grepper]

Thanks Mr. KG.  Very interesting.

Ooops!  Look how easy it is (thanks to me ) to take a great thread in a new, unrelated direction.  

I know there is interest here on the Exchange about microscopes, so maybe we should start a new thread! 

I would like to comment further, and here about your experiences with scopes, but let's move this to a new thread.  I don't have time to do it this evening (1:24am here), but I'll start a new thread tomorrow.  Or, if you wish, you can start one and I'll join you there.

[KnifeGrinders]

Sure.
Your home microscope - like/dislike
http://www.bessex.com/forum/showthread.php?tid=232

[KnifeGrinders]

To be absolutely honest, I didn't take that wire edge quest out of curiosity.
I wish I had - before my sharpening service got the first reject.

A customer returned his S30V Sebenza that I thought I had put a perfect edge on, because from hair-splitting it turned to blunt in less than 10 cuts. He cut some food on a plate, and this little stress turned the edge unusable.
The wire burr image you see above is of his Sebenza that I took in a desperate attempt to understand WTF was going on.

On a straight razor this wire burr just breaks and falls off as you start shaving, however with modern CPM steels it just bends and stays there.
To make things worse, an unsophisticated customer cannot strop it away himself, because S30V is already at the limit of the Cromium Oxide strops, for anything harder you need diamonds or CBN.
The tiny wire along the apex turns into a huge problem with the high-end blades.
And when high-end knives make a good part of your sharpening business, it threats the business.

I had been looking for an indicator of the wire burr without taking every blade under microscope, till I found out this 20 BESS threshold.
Nowadays I will not return the customer his sharpened classy knife until retest it in 10 hours after sharpening and see a score differing by less than 20 BESS.

The near esoteric revelations by Mike's sharpness tester explain the unseen that otherwise would have eluded sharpeners' comprehension.

[Bobbo]

Perhaps this will help Knifegrinders. Just finished testing three knives that have been in my knife black for three weeks unused since sharpening. I checked my book and all were duller by 30 - 40 Bess score. Stropped with sharp pad and all came right back to original sharpness.