Burr Free Sharpening Technique

[SteveG]

For me the term "burr-free sharpening" is a little bit misleading especially in discussion how it differs from "burr based sharpening". In my thinking more suitable term would be "burr minimization sharpening approach".
 
In my understanding burr is formed as a result of plastic flow after each cutting operation, regardless if edge-leading or edge-trailing technique was used.
 
In machining the burr formed during edge-leading cutting direction is called entrance burr while the burr formed during edge-trailing is called exit burr. Exit burr height is usually greater than the entrance burr.
 
Jan

Jan,
You are correct.  I think the term burr-free is used instead is because a burr is not purposely formed, or the goal of sharpening, and it's need for burr removal.  In the case a burr is formed, a micro-bevel is used to remove it, and since that is one of the normal final steps of burr-free sharpening (in the Cliff Stamp method), it isn't necessarily thought of as a separate step. Although for maximum edge sharpness, it is micro-beveling for micro-burr removal is used, then the knife is sharpened at the original angle again to remove the micro-bevel.

Jasonstone, thanks for your explanation!

My understanding how the burr is formed is shown in the attached sketch.

One might think that changing the direction of sharpening from edge-trailing to edge-leading will fully eliminate the burr, but strictly speaking it is not the case, because both burs were formed in a slightly different way. (I consider guided sharpening where the bevel angles are exactly the same for both sharpening directions. Results of free-hand sharpening, where the bevel angles are not exactly the same, may be different.)


 
Jan

In my interpretation of what Cliff is saying, *optimal* sharpening stops the moment the edge is apexed, thus not allowing for burr formation.  I can't argue whether this is true or not, though I can say that I've tried it - unsuccessfully.  Cliff's argument for edge-leading vs edge-trailing is that edge-leading moves damaged metal away from the apex, instead of into it.  His arguments seem to me to be more from the standpoint of edge-retention than achievable sharpness, and from optimal rather than practical sharpening, though his methods seem to work for him - wished they worked like that for me.

SteveG,
That is an excellent explanation.  Could you tell me how Cliff's technique didn't work for you?  This is what I am trying to figure out.  Thank you.

The shaping step seems to be ok for me, so I get to the point where there's no visible light reflected from the edge, and I'm going to apply one or two high-angle passes to micro-bevel and form the apex.  First pass, still dull.  Next pass, still dull.  Keeps on going "still dull" until I can feel a burr - IOW, I'm either not going far enough, or too far, at which point I'm back to the strop just as I would have been if I did my more normal burr-based sharpening, but now that I have a microbevel the stropping is a little harder to get right.

Keep in mind that I don't have much experience at freehand sharpening, and it's likely my high-angle passes are too inconsistent to use this method well, so you'll probably have better results than I get.  Also note that I didn't/don't include back-bevelling (the step where, after adding the microbevel, you resharpen at the original angle to remove the microbevel) in the progression - I might be missing the point, but don't see that it adds any value and just gives me more opportunity to ruin the edge.

So, with all of that said, I can get to slicing phone book paper with the grain, and sometimes across the grain, with this method, but not push-cutting across the grain, which is kinda my threshold for sharp.