US Patent 7347459 Coupling for drilling-with-casing operations

A modified API Buttress threaded casing connection is disclosed for use in drilling oil and gas wells in lieu of using conventional drill pipe. The coupling threads only are multiple tapered yet can be mated with standard API Buttress pin threads having a single taper. The coupling is also shortened to permit abutment of the mating pins at the center of the coupling and can be further enhanced with an integral, sacrificial wear sleeve on one end of the coupling.