Stefan Trethan wrote:
> That's similar to what i think....
>
> BUT if it works that way, why the hell do they ever get dull in first
> place?
> (ok, ok i know i shouldn't cut copper wire)
> Shouldn't cutting any material then sharpen them?
>
Well think about them from the front. You have the two blades
meeting, the edges coming together from the diagonal corners, and a
piece of paper between them. The paper wears just the edge as it slices
through, soon as it is cut it seperates and has no strength. Sandpaper
as it's cut will also be gouging out along the short face sharpening the
edge. Open the scissors up, and try sandpaper then paper along the edge
face to sharpen by hand, which takes longer? :)
Aluminum is softer than steel, but there is still relative wear from
friction, and aluminum is much tougher than paper. The part just ahead
of the cut keeps the part just behind the cut together, if it wears the
edge face a bit more than it wears the edge corner then it'll sharpen
the scissors. Everything that you cut should either dull or sharpen the
scissors, and it's an indicator of the relative wear of the corners and
faces.
Very similar to use of more complex machine tools. An expert
machinist's tools rarely need sharpening. If you balance all of the
variables well, you can actually sharpen the bits with the material
being cut as they're used so that they stay sharp.
Alan