Okay I'll try to get some better pictures of it. In that one section the metal is smeared across those scratches, filling in the valley. It may be easier to show if I start with a slightly rougher surface. Stuff to work on...

Here are a couple more images of a knife edge at 2000x. In order to make a fair comparison, it's essential to capture the same features in each image and at high magnification, it's hard to find your way back to a tiny feature after you've removed the sample. What I did to solve the problem was to make a nick in the blade. A laser or engraving machine would have been great, but I had to make do with what I had - another sharp knife! After creating the nick, I sharpened the knife with the 400# diamond plates because I wanted fairly deep grooves with tall ridges. I completed 20 strokes per side, perpendicular to the edge. I then made one stroke parallel to the edge. I knew I'd be able to find the edge of the nick in the microscope and then all I had to do was locate a unique intersection of scratches:



I removed the sample and cleaned it well, the completed 5 strokes per side with firm pressure using .75um CBN on cow leather. I had not trouble locating the same intersection again and getting another picture:



It's hard to believe that only 5 strokes makes such a huge difference. I originally did my testing with quite a few strokes and found to my chagrin that I'd obliterated almost all the scratches from the stone.

I decided to repeat the process with the 100# diamond plates:

I'm going to try again with the 50# diamond plates because I want to see if the metal is actual being moved, not just abraded. I'll go with coarser strops as well so we can see the abrasion from those clearly.

Wow, that's great! These photographs show very well what how burnishing works!

Same experiment, this time with the 50# diamond plates. Again, only 5 strokes with the strops.

Would be really cool, Clay, if you could compare the burnishing (and abrasion) caused by the .75 CBN (which seems huge) to that caused by plain strops and by strops loaded with a WE paste.

mark76 wrote:


Hopefully I can do that today. I'm testing some arms from our machine shop and have to give feedback, so that will have to come first...

So, does this mean that when stropping and the edge seems to "dull" a bit, we're not necessarily "rounding" the edge, but rather pushing metal up on top of it?

cbwx34 wrote:


That is a really good question! It's conceivable that we are pushing metal up behind the edge, but I'm not sure how much we're really talking about. I'd like to do some good cross section studies and find out.