Understanding a burr

[grepper]

As far as sharpness testing goes, we should all get one of these.  Then we could all agree on a standard:
http://www.catra.org/pages/products/kniveslevel1/st.htm

This would be cool for $100.00:
http://www.catra.org//pages/products/kniveslevel1/lkep.htm

One of my favorite tests is paper towel.  Not the stiff brown stuff in gas station bathrooms, that's too easy, but Bounty or some other good quality white, absorbent rolls they sell for home/kitchen use.

Pull the edge just tight enough that it does not collapse and without any more pressure than the weight of the knife gently saw back and forth against the edge.  You are looking for clean cut without any tearing or hair fibers hanging from the edges of the cut.

Some of these paper towels are extremely fibrous, and require a very sharp edge to cut. cleanly.

Try it from both the ends and sides of the towel.  Anyone who has done the standard "paper" test knows that paper fiber is generally directional, and may cut easily in one direction but almost impossible in the other.

[mike40]

Yes Mark, I will have to tell the wife I need both of these instruments to test the sharpness produced by my newly acquired and very expensive Tormek. I wonder if it could measure her trajectory as she goes through the roof?

[grepper]

That's funny Mike. 

My wish list:

Handy Tabletop Scanning Elecctron Microscope  ($15K - 30K)
CATRA Sharpness tester  (Very Epensive)
CATRA laser goniometer ($100.00)

Hmmm...

[grepper]

I kicked up a fine burr on a knife @ 320 grit, and then wiped my finger on the back of the knife toward the edge and over the burr which unrolled it and pushed it up so that it stood up on the edge of the knife.  Some tiny flakes of it left sparkles on my finger.

The burr is very, very thin.  It waved in the breeze of only the lightest puff of air.  Even though it was so thin, as you can see most it did not wipe off, but just stood up on the edge.  Interesting that it is more malleable than you might expect.

Here's what it looked like:

[Herman Trivilino]

Amazing photograph, Mark.

[mike40]

Cool photo Mark. The first time I've seen a burr so clearly. I sure can't see them with my old eyes.