Cold Rolling

Cold rolling is the prestressing of the thread roots of the drill collar joint and results in a more durable connection. A
hydraulic ram forces a roller into the thread root and follows the root down the thread sprial. The roller has the same
contour as the thread root and the pressure between the roller and the root compresses the metal in the thread root. This
compression of the fibers in the thread root results in a stronger connection that can withstand bending stresses longer
without fatigue damage.