KILLING THE EDGE

R

Robert Ptacek

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Oct 8, 2013
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I've noticed in many sharpening videos they run the edge against the stone to flatten the edge before sharpening.I don't do this regularly but am wondering is it absolutely necessary?
 
No, I think for some of the videos it's to then show how easily/well/effectively they can resharpen the edge. Basically to show they're not starting with an already sharp edge.
 
In some circumstances, it can be useful. If, in the use of the knife, you notice the edge seems weak & unstable, that can be an indicator of damaged steel near the edge. It might be from heat damage, as happens with brand new blades from factory edge finishing or deburring. Or, if it's a well-used kitchen knife that's been 'steeled' frequently for edge upkeep, the steel at the apex becomes weakened & brittle from too much work-hardening (bending back & forth on the kitchen steel). In circumstances like that, it's necessary to take that weakened steel off the edge before resharpening. And lightly drawing the edge across the stone, veritically, is the quickest way to do that. In more extreme fashion, if a 'steeled' edge becomes excessively recurved from all that steeling - and they do, eventually - the same method can be used to grind the recurve out of the edge and get it straight again. But that's where a lot more grinding would have to be done.

But, if you've been using the knife and you already know it's been working pretty well and doesn't seem weak at the apex, you don't necessarily need to do this every time you resharpen.
 
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Dragging the edge across the stone would help remove fatigued steel as mentioned above. If plateau sharpening, the flat edge will produce a glint which you would reference. When the glint is gone you know you are close to apexing and can proceed to micro beveling.
 
I did this with my work knives, my preference was a smooth polished edge.
Doing this helps get rid of micro cracks.
 
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