A milling system has been invented for milling an opening in a tubular in a tubular string in a wellbore extending down from a surface of the earth, the milling system, in one aspect, has a whipstock connected to an anchor assembly and a mill apparatus releasably connected to the whipstock, the mill apparatus having auto fill apparatus therein. A mill has been invented with a mill body with a top end and a bottom end, a flow bore through the mill body, and an auto fill apparatus in the flow bore. A valve assembly has been invented for selectively controlling fluid flow through a hollow tubular in a string of hollow tubulars in a wellbore extending from a surface of the earth into the earth, the valve assembly in one aspect having positions limited to at rest, circulate, and anchor set positions so that a fluid pressure indicating at the surface indicates only either a pressured up position for anchor setting or a pressured up position for fluid circulation. A milling system has been invented with apparatus for releasably containing an isolated charge of fluid. A float valve for use in wellbore operations has been invented with a valve member having a vent hole for releasing fluid pressure build up beneath the valve member. A fill sub has been invented which uses such a float valve.

A milling system has been invented for milling an opening in a tubular in a tubular string in a wellbore extending down from a surface of the earth, the milling system, in one aspect, has a whipstock connected to an anchor assembly and a mill apparatus releasably connected to the whipstock, the mill apparatus having auto fill apparatus therein. A mill has been invented with a mill body with a top end and a bottom end, a flow bore through the mill body, and an auto fill apparatus in the flow bore. A valve assembly has been invented for selectively controlling fluid flow through a hollow tubular in a string of hollow tubulars in a wellbore extending from a surface of the earth into the earth, the valve assembly in one aspect having positions limited to at rest, circulate, and anchor set positions so that a fluid pressure indicating at the surface indicates only either a pressured up position for anchor setting or a pressured up position for fluid circulation. A milling system has been invented with apparatus for releasably containing an isolated charge of fluid. A float valve for use in wellbore operations has been invented with a valve member having a vent hole for releasing fluid pressure build up beneath the valve member. A fill sub has been invented which uses such a float valve.