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: In a mining machine which incorporates cylindrical cutting bits having conically shaped heads and located in sockets of bit holders, the cutting bits are retained within the sockets by split tubular spring sleeves. The split spring sleeves are located on the shanks of the bits and resiliently engage the inner surface of the sockets thereby securing the bit in the mount. The bit is free to rotate and the sleeve interposed between the socket and the bit prevents wear on those parts of the bit and mount.