To kick off this thread, I polished the sample down to .25um with the kangaroo strops. The plan here is to develop a clean baseline from which to the lay in the scratches from a specific stone or strop so that we can isolate the scratches of that abrasive and not worry that we're seeing leftover scratches from a previous abrasive. I didn't go for total perfection in the polish since it's time consuming enough that doing it for each and every grit we have available would be prohibitive. At this level, we have a clean enough slate that it will work very well for our purposes. I've imaged the blade at 200x, 800x and 2000x. The bevel is slightly curved since I was working from a blade that already had a micro-bevel. The shoulder of this edge is at 20 degrees and the edge is at 25 degrees. To study the different abrasives, I'll work at 25 degrees so that we have a smooth shoulder to compare against and should be able to see the entire mirco-bevel in the field of view. Here are the images:

200x:


800x


2000x

Hi Clay,

Wow! I'm fascinated by these photos.

In particular, I'm quite curious about what look like comets in your photos.... Dark spots with tails on them. I marked some on one of your photos:



Any idea what these are?

Sincerely,
--Lagrangian

I see these a lot when I go to a higher polish. I think they are either inclusions getting pulled free or little pockets in the metal. Because there is a tail, I speculate that they are inclusions that dig a little furrow as they're ripped out and pushed along the bevel toward the edge.

AnthonyYan wrote:

wickededge wrote:


Wow.... pretty interesting. Would be neat to get an idea of how big those inclusions are, especially the ones that tear out, and their relative size to grit ratings.

I wonder what the inclusions are actually made of. Are they carbides, or slag impurities? Maybe someday, we can track down an metallurgist and ask.


btw, have you ever considered doing a metallographic etch of metal for your microscope samples? Hmm... maybe not a good idea after all, since some of those chemicals are pretty toxic...

Sincerely,
--Lagrangian

This should be good Clay!
I can't wait to see how the different grits look over the baseline finish.

I can't see why you would want to do any etching in this test series. I do understand why it is done in certain situations (detecting grain size and shape, inclusions, etc.), but I would think that it could possibly mask some of the results that you are trying to capture. I would guess that we should get great information about the scratch patterns without any etching.


Phil

Hi PhilipPasteur,

Oh, I didn't mean specifically for this test. Possibly a bad idea to etch for these tests, since we're interested in how the abrasive affects the surface, and don't want that confused with how the etching could affect it.

I was wondering etching might be useful in other ways. Maybe? Not sure.

Sincerely,
--Lagrangian

AnthonyYan wrote:


I know there's occassional discussions about "carbide tearout" in sharpening. Maybe a reason?