The two associated solid model printouts show a 1/16"-radius 
semicircular hole carved into the as-cast wall of a manganese 
bronze fitting.  I am seeking suggestions as to how to make 
this hole.  So far, ideas include (1) filling the cavity with 
low-melting alloy like CerroBend and drilling, (2) making a 
hardened drill guide that reaches up inside the cavity from 
the bottom and essentially forms the other half of the hole 
and keeps the drill from wandering out into the cavity, or 
(3) sinker EDM.