The drilling of a hole In the skull

The act of making a surgical opening in a living skull. This act was sometimes performed because of the belief that it would allow evil spirits to leave the body.

The process of boring/drilling a hole in the center of a mirror for the purpose of making a pierced-mirror design, like a Cassegranian. Back to top of glossary Back to top of glossary Back to top of glossary

Machining whereby the centre of a bar is removed to produce a hollow bar, tube or cylinder.