Straight hole drilling machines for coal mines

Enhancing down-the-hole air hammer capacity in directional drilling

“…A promising approach to straight-line hole-making is rotarypercussion drilling using down-the-hole air hammer drills. As compared with the other techniques, this method allows minimum pressing force between the drill head and the hole bottom, as well as low speed and minor torque transmitted to the drilling assembly, which enables minimized distortion of hole trajectory and ensures straight-line drilling [5].…”