| 摘要 |
<p>A drill collar (10) including a thick wall cylindrical member (12) having diametrically enlarged opposite end portions (14) and (16) is provided and includes further intermediate length longitudinally spaced diametrically enlarged portions (18). Each diametrically enlarged portion includes a diametrically enlarged wear band (30) extending thereabout formed by a welded build-up of hard metal thereon subsequently machined to include a cylindrical outer surface concentric with the center axis of the drill collar. The wear bands provide narrow wear surfaces which serve to reduce friction and maintain other outer surfaces of the collar spaced from contact with the opposing surfaces of an associated well bore.</p> |
