In a recent post, Sharpening with the King 1k/6k combination stone, I showed one example of burr removal, folding the burr and removing it (at the sharpening angle). In this post, I demonstrate two other techniques for burr removal; stropping and high-angle-passes.
As discussed in What is a burr? part 1 and What is a burr? part 2, There is no unique definition of a knife burr. In general, the term refers to excess, unwanted metal beyond the “ideal” apex; however, the “wanted” metal will depend on how the blade is used and what material is being cut. To aid in demonstrating the length scales and geometries involved, several examples were chosen.
In the first two examples, the starting point was a blade honed to the Shapton 16k, ending with 20 edge-trailing passes. This produces a near-perfect triangle with a small foil-burr at the apex.
In the first example, the apex is micro-convexed by stropping, removing the foil burr plus approximately 7 microns of blade height. The increase in near-apex angle from approximately 16 to 26 degrees (inclusive) significantly improves the durability of the blade. This blade easily shaves, but has minimal draw-cutting aggression, due to the uniformity of the apex.
In the second example, the blade was given three passes (per side, alternating) on a DMT EF (1200 grit) diamond hone at an angle of 20 degrees. Although minimal force was applied, only sufficient to hold contact, the pressure was extremely high due to the small contact area. Pressure is force/area, and the contact area is only that of the micro-bevel. As a result of this high pressure, there is obvious plastic deformation of the apex.
The above example was performed with a simple carbon steel straight razor. The following are examples from a ZDP-189 pocket knife (Spyderco Manbug).
In comparing the two knife edges, above, the results are as expected. The stropped edge easily shaves and push-cuts paper, but has no draw-cutting aggression and does not pass the 3-finger slide test. The broken-burr edge draw-cuts aggressively and easily passes the 3-finger test, but does not shave or push-cut paper.