دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: the motion a bit makes when it does not rotate around its centre but instead drills with a spiral motion. It usually occurs to a bit drilling in a soft or medium soft formation when the driller does not apply enough weight or does not rotate the bit fast enough. A whirling bit drills an overgauge hole (a hole larger than the diameter of the bit) and causes the bit to wear abnormally.