Modeling transverse motions of a drill bit for process understanding

A model for drill bit transverse motions is proposed that identifies process conditions affecting hole quality and helps in the interpretation of drilling signal patterns produced during the hole-making process. A two-dimensional model of a drill rotating in a hole with clearance is presented. The simulation results, drilling force signal patterns, and hole geometry were found to be in close agreement. Drill rotation speed, drill stiffness, structural damping, drill hole clearance, and amplitude modulation of the forces acting on the drill appear to have a significant effect on drill bit transverse motions and on hole quality.