drilling

[don dougan <dondougan@zzzzzzzz>]

Bill (and Simon too),

As Simon says, using a ordinary twist drill is great if you want a really
clean hole in marble, and stepping the hole sizes up sequentially saves
wear-and-tear on the drill motor, as well as keeping the stress to the
workpiece to a minimum.
When I need very small clean holes (less than 1/4") I usually use twist
drill bits in a geared drill that I can adjust down to speeds of only 50
or 60 rpm.

Another type of drill bit that will give a larger, but also an extremely
clean, hole with almost no chipping or spalling is a carbide-tipped glass
drilling bit in a regular rotary action drill (no hammer).  The glass
drilling bits have the big advantage that the hole on the exit-hole side
will be almost as clean as the entry-side.  If the exit-hole side has to
as perfect as the entry-side, then when the point of the glass drill-bit
is about halfway through the exit surface, pull it out, flip the
workpiece over, and drill the final little bit down into what was the
exit-hole.  Low rpm's will help here too.

Good Carving to You;
Don

http://www.dondougan.homestead.com/indexdd.html