"bill a" wrote in message
. com...
the post from DanG is correct, but one caution is that thin section
castings sometimes
can have chill spots, which are very hard. If you have a hole that is
particulary difficult, and the
drillbit dulls, chill iron is probably the culprit. If that hole
location is a must, you may need to use
a carbide bit, slower rpms, and some lubricant.

A masonry carbide bit, or something special?