دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a roller cone bit that is specially designed for air or gas drilling. It is very similar to a regular bit, but features screens over the bearings to protect them from clogging with cuttings and thicker hardfacing on the shirttail to protect them from abrasive, high-velocity air or gas drilling fluid.

n: the part of a drilling bit on which the cone is anchored. Shirt-tails extend below the threaded pin of the bit and are usually rounded on bottom, thus acquiring the name.