| 摘要 |
A thread swaging screw of polygonal cross-section having a number of turns on a straight shank portion and at least one sizing turn between the shank portion and the tapered work entering end portion of the screw. The sizing turn inwardly of the pitch radii has the same cross-section and flank angle as the turns on the shank portion and the sizing turn in a region outwardly of the pitch radii has a flank angle slightly less than the flank angle o f the turns in the shank portion and crest radii at the lobes which are greater than the crest radii at the lobes of the shank turn to compensate for the contraction of the dedendum portion of the internal threads swaged in the workpiece. A method of forming the screw is disclosed in which the threads are rolled on the straight blank of polygonal cross-section utilizing contoured thread rolling dies for rolling a tapered thread on the work entering end portion of the screw and with one or more thread grooves of the dies modified in the region adjacent the ooutlet end of the dies to form a sizing turn on the screw intermediate the work entering portion and the main shank portion. |
