Abstract: A drilling machine includes a boom assembly which has two straight parallel longitudinal beams of extruded steel, each of a section defining straight parallel inwardly and outwardly facing ways, a drilling head in a carriage and rollers guiding said carriage for linear movement of said drilling head parallel to said inwardly facing ways, two straight parallel longitudinal boom extension members and rollers guiding said boom extension members in said outwardly facing ways, and cross members linking said boom extension members to form a frame, plate braces linking said beams in longitudinally spaced planes perpendicular to the axes of the beams, said plate braces being apertured to provide clearance for assembly and normal movement of said carriage, said drilling head, and drill tubes passing through said drilling head, and further longitudinal members linking said plate braces to form a cradle of the boom assembly, said cradle having brackets for pivotally supporting the boom assembly on a base.