| 摘要 |
Joints for coupling the box and pin ends of drill rods and casings, particularly for the mineral exploration industry, have single start, helical tapered threads extending axially intermediate cylinder sections. The threads have frustoconical crests and roots with the taper being about 0.75 to 1.6 degrees. The threads are of a pitch of about 2.5 to 4.5 threads/inch, have negative pressure flank angles of about 7.5 to 15 degrees relative to a perpendicular to drill string central axis and clearance flanks of an angle of at least 45 degrees to aid in maintaining the joint in a coupled condition, even under overload, and facilitate joint make up. Also, the box and pin have shoulders tapered at about 5 to 10 degrees. Additionally, the pin crests have an interference fit with the box roots while the box crests are radially spaced from the pin roots to provide a rigid joint while leaving a space for debris and pressurized lubricant. |
