Effect of helix angle on forming of trapezoidal threaded shaft rolled in cross wedge rolling

Taking the spatial relationship between the die cavity and the deformation zone of the part into account, the expression of the helix angle for die was deduced and the trajectory curve of helix angle was drawn by using the relationship between instantaneous screw rolling radius and pitch. The thread rolling tests under two helix angles conditions were done with H630 wedge cross roller, the parts were accurately measured by using the coordinate measuring instrument, and the characteristics of the teeth heights and pitch were analyzed. The results show that under fixed value helix angle condition, the maximum tooth height relative error and pitch error are respectively 6.88% and 3.50%, and the obvious spiral marks appear on the end of the rolled part. At the variable helix angle derived in the paper condition, the tooth height relative error and pitch relative error are 2.51% and 1.42%, respectively, and the threads are full and has good uniformity. The higher quality threads are obtained using the solving methods of helix angle provided in the paper, and the method provides theoretical basis for precisely forming of threaded shaft in cross wedge rolling. © 2017, Central South University Press. All right reserved.