Homebrew PCBs

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