Abstract: The guide bushing of a blast hole drill is resiliently mounted to dampen lateral vibrations of the drill string. The mounting arrangement comprises four pads symmetrically placed about the bushing and restrained against all but radial movement. Each pad includes a radially inner bearing section that bears against the exterior of the bushing, an outer backing section that is radially movable with respect to the bearing section, and a resilient cushion between the two sections. A four-lobed cam ring surrounds and faces the backing sections and is rotated to simultaneously load all the cushions to a selected degree. In the preferred embodiment, the mounting components are in an enclosed housing that defines guide channels for the pad and that can easily be fitted into the deck of a machine.

Abstract: A system for use in the make-up or break-out of drill stem members of earth boring machines having a hydraulically operated power swivel to rotate the drill stem and hydraulic cylinders to raise and lower the swivel. A first, variable volume pump supplies fluid to the hydraulic cylinder through a four-way valve. A servo pump controller, connected with this valve and operable by variable resistors, establishes the linear make-up and break-out speeds for the power swivel. A second, variable volume and reversible pump supplies fluid to the power swivel means. A second servo pump controller, connected with the second pump and operable by variable resistors, establishes selected linear rotational travel speeds for the power swivel. Make-up torque is controlled by an electrical solenoid activated pressure compensator connected with the second pump, and linear speed is similarly controlled.