US Patent 9506336 Method and apparatus for drilling subterranean borehole

A method of drilling a subterranean bore hole comprising a) pumping a drilling fluid down a drill string, the drill string having a drill bit at an end thereof, b) rotating the drill string about its longitudinal axis to that the bit forms bore hole in the ground, the method further comprising the steps of: c) changing the rate of pumping of the drilling fluid into the drill string in response to a change in the speed of rotation of the drill string, and/or changing the speed of rotation of the drill string in response to a change in the rate of pumping of the drilling fluid into the drill string.