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Re: Antenna research

>Trivia question for tool-types:
>I remember that in the Ag Engineering machine shop, they had some two-
>piece dies to make holes through sheet metal.  You drilled a small 
>hole for a bolt connecting the two pieces, which were round cup-
>spaned dies.  The smaller fit inside the cavity of the other, and had 
>cutting edges.  The basic technique was to drill a small hole 
>through the metal for the bolt, connect the dies with the bolt, then 
>tighten the bolt, and the smaller die but thru the sheet metal while 
>being braced against the larger die on the opposite side of the 
>metal.  No warping, no slipping.
>ASCII art attempt:           __________
>                             |        |   Large die
>                             |        |   
>                              |______|     Small die
>Anyone know what those dies are called??????  Maybe I should call dad 
>and see what's happenin'......cheers.

These are called Knockouts, or Knockout punches.  Industrial electricians
use them routinely to make holes for conduit in breaker boxes, etc.  A well
equipped tool shop ought to have 'em.  You may find them at local electrical
supply houses, too.

BTW, if you can find a set to borrow, make sure they're sharp, as they can
misbehave and leave jagged edges if dull or burred.