Thread Rolling of Antiloosening Bolt Fastenings Based on Double-Screw Mechanism

Abstract

The purpose of this study is to establish the thread rolling process of the bolt fastenings based on the double-screw mechanism. Two-roller die plunge feeding is employed as the rolling method due to its high processing precision. The roller dies used in this experiments have special grooves whose shape is almost a reverse projection of the double-screw thread. The pitch ratio of the course and fine threads of the double-screw bolts is set to be 2:1. The double-screw bolts can be rolled precisely in the same process as the single-screw bolts using these dies. The deformation behavior of the workpiece during rolling is examined and the formed material fills the grooves of the dies in each cross section very smoothly. The rolled double-screw bolts completely pass the very severe vibration loosening test based on NAS3354. The fatigue tensile strength of the rolled double-screw bolts is increased twofold that of the cutting double-screw bolts.