Hammer bit for percussive drilling - is positioned on taper mandrel by screwed thread and cone with thread disengaged when tool is in use (NO 31.10.77)

摘要

The hammer bit is used for percussive drilling and has a cylindrical body with several cemented carbide cutting tips (13). It is held on a taper mandrel by an initial threaded portion and an internal cone (20) matching the taper. Holes through both form cutting fluid passages (17, 18). The cone in the drill body has a straight extension, having two screw threads (21) of rounded profile dividing it in half (22, 23). The mandrel has a corresponding extension, with similar threads at the end. When screwed into the bit, these threads pass through those in the drill bit, being disengaged when the tool is in use.