the crew member who handles the upper end of the drill string as it is being hoisted out of or lowered into the hole. He is also responsible for the circulating machinery and the conditioning of the drilling fluid. Found on http://www.encyclo.co.uk/visitor-contributions.php
the crew member who handles the upper end of the drill string as it is being hoisted out of or lowered into the hole. He is also responsible for the circulating machinery and the conditioning of the drilling fluid.