Extension bar for blast furnace tap hole drill

摘要

An improved extension bar for a drill rod assembly on a blast furnace tap hole drill having an increased diameter sufficient to occupy a significant portion of tap hole drilled so as to minimize the volume of blast furnace hot metal that can emerge from the blast furnace before the striking bas assembly can be removed, and having a protective sleeve portion at the rearward end thereof to shield and protect the interface between the drill rod and extension bar to prevent such interface from being exposed the hot metal and thereby avoid the possibility that they could become welded together.