Poor Quality Steel and Sharpening

This is a great example of both sharpening problems and low quality steel. This photo is of the back of a curved leather paring knife. It is a bit difficult to see in the photo, but the darker, shiny area below the cutting edge has been highly polished. Unfortunately, our unnamed client,  let us call him Mr. B, neglected one of the first principals– feeling the burr. Once you feel a burr on a cutting edge, it means that the two planes (bevel and back of the knife) have gone past the point where they meet. As William Blake says in the Proverbs of Hell, “You never know what is enough unless you know more than enough.” The burr lets us know we have sharpened the edge more than enough, and can proceed to the next grit. A great deal of time was spent creating a polished area , that will not affect the cutting ability at all, and be instantly removed once someone attempts to regrind the knife.

The knife edge was dropped, and on the left side of the blade there are some chips, and on the right side you can see bent metal. What does this tell us? That the steel was improperly hardened. Any steel that is hard enough to pare leather (at least Rc 55 or so) should be brittle and chip if damaged, not bend like on the right side of the photo.

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