دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a bit placed on a special device called a hole opener that serves to guide the device into an already existing hole that is to be opened (made larger in diameter). The pilot bit merely guides. or pilots. the cutters on the hole opener into the existing hole so that the hole-opening cutters can enlarge the hole to the desired size.

n: the complex bit that made up the bottom center of enlarging bit extends a small bit