A rotary tool used in drilling oil or gas wells in which the bit is rotated by a turbine motor inside the well. The principal difference between rotary and turbo drilling lies in the manner that power is applied to the rotating bit or cutting tool. In the rotary method, the bit is attached to a drill pipe, which is rotated through power supplied on the surface. In the turbodrill method, power is generated at the bottom of the hole by means of a mud-operated turbine.