swirling

For the low rock-breaking efficiency at borehole centre of the current drill bit, this paper presents a new bit with swirling bottom-hole model (swirling-cutting bit) and analyses its kinematics and rock-breaking features. Using the cylindrical coordinate, the bit revolution and cone rotation motion behaviour are analysed. With the position and velocities equations establishment of cutting element, the contact section between different cutting elements ring and rock are given, including the velocities distribution results on the section. With the numerical calculation and experimental test, the results show that the elements on maximum elements ring pass through the borehole centre, and broke the rock with compression and cutting effect. With the start point at the bottom-hole and end point at the borehole wall, the contact force of element acting on rock contains effect of 'digging' from the inside out and from the bottom up. The conclusions provide reference for improving the bit rock-breaking efficiency, cutting element distribution and bit structure optimisation. Pang, X. (2015) 'Kinematic and rock-breaking characteristics of new drill bit with swirling bottom-hole model', Int.