Abstract: A heavy duty, mobile drilling machine is disclosed based on a track type vehicle having a rotatable turntable, an operator station and other vehicle machinery being arranged along opposite sides of the turntable to form a central open channel, a boom being pivotably connected to the turntable and arranged in the channel, the boom being of a telescoping type having an extendable and retractable portion forming a chamber for receiving water or other ballast, a drill implement being mounted on a forward end of the extendable boom portion by relative transverse pivots with respective motors or jacks providing for 360.degree. adjustment of the drill implement, the telescoping nature of the boom and the other controls for the drilling implement, boom and turntable permitting use of the drilling implement in a wide variety of operating positions.