Mechanical power to the bit / corehead
This article describes the various ways of transmitting mechanical power to the bit by rotation. There must be sufficient HHP at the bit to keep the cutters or diamonds clean, and that an increase in mechanical power, applied to the bit with minimum vibration, will increase penetration rate.
Mechanical power is the product of torque and speed. For a given bit, once the threshold WOB necessary to make the bit teeth or cutters start to dig in has been overcome, then for a given WOB increasing the rotational speed will . . .