Abstract: Coupling structure to connect sections of a compound drill stem. The drill stem has concentric passages, one connected to a fluid source to provide fluid in an area being drilled and another connected to a vacuum source to carry off the fluid and accompanying cuttings from the drilling area. In the preferred embodiment, the coupling structure includes a housing with a prismatic surface that telescopically cooperates with a similarly shaped surface of at least one of the drill stem sections to effectively transmit torque through the compound stem.

Abstract: A drill assembly comprising a tool bit of the type including a slot at one end for receiving a cutting element. A positioning clip removably disposed in the slot and having a cutting element engagement structure for maintaining the position of the cutting element within the retainer clip, and drill body engagement structure for locating and maintaining the position of the clip within the slot of the tool bit.