Roll threader manufacturing process control for miniature fasteners

Threads on bolts and other fasteners are formed accomplished by rolling a smooth blank between a pair of linear dies at room temperature. The current method to control the transverse dimensions of the bolts during thread rolling fails to provide the needed tolerances for bolts with nominal dimensions of 1.0 mm or less. Towards addressing the shortcomings of the currently used roll threading manufacturing process, a mechanism to actively control the transverse dimension of the bolts is presented along with the corresponding control methodology. The proposed manufacturing process has been designed and, with its control methodology, has also been implemented on a roll threader. Comparison of bolts produced using the old system of dies and the newly developed methodology is presented using photographs taken using an optical microscope and a scanning electron microscope. These photographs clearly indicate the advantage of the newly implemented manufacturing process control system. With the new proposed system, the thread surface has clearly been improved and lateral tolerances less than five microns have been achieved on 1.0 mm diameter bolts.