www.thedriller.com/articles/88224-reverse-circulation-drill-pipe
Reverse Circulation Drill Pipe
April 1, 2011

Holte Manufacturing Inc. offers Reverse Circulation Drill Pipe. Threaded on both ends, this pipe features precision-machined and carborized joints. Holte’s drill pipe design allows the center tube to increase strength and rigidity: Prior to welding the outer pipe to the joints, the inner pipe is torqued into the machined joint, creating additional strength.
Holte Manufacturing Inc., Card No. 111