My Hypothesis on Stropping and Burr Removal

Edge-Leading vs. Edge-Trailing on Stones:
When finishing on a stone my goal is always to have as clean an apex as possible prior to stropping. Ideally it would also be as refined as possible for that level of cleanliness. Herein lies the debate of edge leading vs. edge trailing strokes. First, both types of stroke will form a burr. However, the very light edge leading strokes will to some extent remove the burr that was created on the previous pass; whereas edge trailing will tend to build up and draw out a burr.

Further there is a difference between edge trailing and leading in terms of apex width. As a general rule, the smallest attainable apex width for an abrasive particle is 10x smaller than the particle diameter itself. For example, a 2 micron rated stone can leave a 2/10 = 0.2 micron apex width. That effect is achieved using edge trailing strokes only because edge leading rams the edge with particles that cause micro chipping at the apex. This increases the apex width by about 50%. Using the same 2 micron stone, the apex width would then be 2/10*1.5 = 0.3 micron apex width.

For these reasons I personally prefer to use a combination of alternating and extremely "light passes" (less than the weight of the knife). From my experience, it gives the best of both worlds.


Fatigued Steel Zone:
The mechanism for steel removal by an abrasive particle is such that is "grabs" or catches onto the steel with a cutting facet and causes a tiny chunk of steel to either 1)tear away or 2)break away. Regardless of tearing vs. breaking there is a zone of fatigued steel that remains. That zone is generated in between the removed chunk of steel and what remains on the edge during the abrasion process. Part of that zone is carried off with the removed steel but some remains on the edge needing to be cleaned up and minimized.

My theory is that smaller particles leave a smaller fatigued zone. This leads me to the conclusion that finer abrasives are going to be favorable for a finished edge. Of course without sacrificing bite in the edge which seems very doable from my sharpenings that do not compromise too much on the bite I'm used to.


Progression (um = micron):
1) Venev 1200F (2-3micron diamonds)
2) 4um CBN on leather strop (same angle as stone)
3) 1um Diamond on balsa strop (same angle as stone)
4) 0.5um CBN on balsa strop (1 degree higher)

Apex Width (reference above progression):
1) 0.2-0.3 microns edge trailing (0.3-0.45 microns edge leading)
2) 0.4um
3) 0.1um
4) 0.05um

Goal of Abrasive (reference above progression):
1) Establish a refined but clean apex
2) Reduce apex width to a consistent size. Clean up burr bits and micro chips
3) Reduce apex width and fatigued steel zone from previous strop.
4) Deroot the remaining bits of burr and minimize fatigued steel zone further