Abstract: A drilling apparatus of the type having a drilling mast and a transfer arm mounted at a first axis adjacent the mast to move between a lower position near ground level and an upper position aligned with the mast is provided with a reaction point anchor fixed with respect to the drilling mast and spaced from the first axis. A fixed length link is pivotably mounted to the transfer arm at a second axis, spaced from the first axis, and a first single stage cylinder is pivotably mounted at one end to the distal end of the link and at the other end to the transfer arm. A second single stage hydraulic cylinder is pivotably mounted at one end to the distal end of the link and at the other end to the reaction point.

Abstract: A self centering clamp for down-hole tubulars includes first and second opposed clamping members guided along a clamping axis by first and second guide channels defined by a frame. Each clamping member defines a hydraulic cylinder in which is disposed a piston which is rigidly mounted to the frame. A rack is coupled to move with each of the clamping members. These racks are interconnected via a pinion gear which meshes with both racks so that the two clamping members move in a counterdirectional manner and remain equidistant from a central point on the clamping axis. In this way the clamp centers down-hole tubulars of various diameters about the same line, perpendicular to the clamping axis.