US Patent 7516636 Roller tool for forming grooves in pipes

A device for forming a circumferential groove in a pipe is disclosed. The pipe has an inner and an outer surface. The device has a first roller tool, which engages the outer surface of the pipe, and a second roller tool, which engages the inner surface of the pipe. The roller tools are arranged opposite to one another and are rotated relative to the pipe while being forced toward each other, thereby cooperating to form the groove. To prevent excessive thinning of the pipe wall, the roller tools are offset from each other along their axes of rotation. The midpoint of facing circumferential surfaces on each roller tool serves as a measuring point for the relative offset.