Composite thread coupling for reinforced pipe

Abstract From the Canadian patent

A joint for fiberglass pipes is provided wherein mating female and male threads are ground or scribed into the ends of the pipes to be joined. At least one of the ground threaded, surface has a paste thread contact molded onto it so that the root or base of the paste thread is below the crest of the ground thread. Upon mating of the coupled pipe ends the paste thread, surface provides a smooth finish and a relatively low consistent, engagement and disengagement torque. The overlapped projections of the ground male and female threads provide for mechanical interlock and correspondingly enhanced tensile strength in the joint.