Andy LaTorre wrote of the difficulties of partial-punched materials and
the problems they cause.

Having a hand in manufacturing for the last 6 years, I have had a
chance to closely inspect punches that are used to make Numerical
Control (NC) machine data paper strips used to write out NC machine
programs, then to read them in at the machine. They still use these
paper tapes today because you can expose them to big magnetic fields
found in machine shops, heat, splash oil on them, and they're still
good to read .. unlike floppy disks.

Anyway, I looked closely at the punch. The punch itself was cup-shaped,
kind of like a melon scooper, but not quite. I was told it was shaped
this way such that when the paper or mylar tape was perforated, the
punch's shape caused the punching to bow a bit, and just as the last
bit of material is cut through the scrap dot of paper is bent into a
little cupped spring so that when cut completely though, it throws
itself away from the punch when it reshapes itself into a flat disk
again - like the way you bend a deck of cards moments before you play
"52 pick-up" ;).

- K a r l   B.  E l l i s o n
  Ashland, Massachusetts, U.S.A.
  KBEllison@aol.com
  http://members.aol.com/kbellison/kbe.html