Screw rolling machine for inner thread

A screw rolling device of an internal screw thread includes rollers the outer surfaces of which are provided with annular screw thread cogs; the quantities of the rollers are 2 to 5 pieces; the groupof rollers is uniformly arranged on the same circle of a roller seat; each roller consists of a cone and a cylinder; the middle part of the group of rollers is provided with a central annular gear axis meshed with each roller. The invention can lead each roller to obtain the coaxial locating for realizing screw rolling; besides, the invention also bears coaxial force and radical force when the roller group works and particularly leads the radical force of the roller with the largest load to be balanced and neutralized on the central annular gear axis, thus not only compacting the structure ofthe device, but also optimizing the stressed situation for the transmission of the device. The screw rolling device of the internal screw thread can be used for the screw rolling process for the internal screw thread of a crud