دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a special mill that has a heavy tubular extension below it called a pilot or stinger. The pilot, smaller in diameter than the mill, is designed to go inside drill pipe or tubing that is lost in the hole. It guides the mill to the top of the pipe and centres it, thus preventing the mill from by-passing the pipe. Also called a piloted mill.

n: a kinds of special made milling tool.

a step-diameter mill that makes a pilot hole then enlarges it with the upper diameter.