Abstract: To reduce the wear of surfaces of anti-friction devices or bearings, the surfaces are diamonded, e.g. by being provided with diamonds or by being the surfaces of diamond-containing concretions, and are lapped before use, substantially no further wear occuring after the surfaces have been lapped.

Abstract: Apparatus for interchanging the central portion of a drill tool with a core barrel is disclosed. The interchange is effectuated without the need for raising the drilling tool with the drive turbine. Both the core barrel and the central portion of drilling tube have barrel tubes associated therewith and a seating associated with a receiver tube rotating with the tool holds the barrel tube in a vertical position. The end of the core barrel is spaced from the inside end of the barrel of the drilling tool to avoid friction and facilitate the cutting of the core.