Trepanning

Trepanning is a deep hole drilling process. It is typically used on larger diameter bars. The drilling process leaves a core. The solid core may then be used on other orders.  The most basic trepanning process creates a hole through the entire length of a bar or plate. Other methods keep the hole from going all the way through the material, creating what is called a blind hole. In many cases trepanning is a first stage process which is usually then followed by honing for finish, or then moved onto further machining.