Rolling flat die for manufacturing a screw with groove for self-locking

A rolling flat die operable on a blank to produce a threaded element having self-locking threads comprising a flat die moveable in a linear forward direction to engage said blank and form said self-locking threads on said blank, said flat die having a forward section and a rear section, said forward section having a first plurality of first thread-forming parts parallel to one another, each of said first thread-forming parts having a first outer crest end and a first inner root end, said first outer crest ends being spaced from one another by a first die pitch, said first outer crest ends being spaced from said first inner root ends by a first die depth, said rear section having a plurality of second thread-forming parts parallel to one another and parallel to said first thread-forming parts, each of said second thread-forming parts having a second outer crest end and a second inner root end, said second outer crest ends being spaced from one another by a second die pitch, said second outer crest ends being spaced from said second inner root ends by a second die depth, said second die pitch being twice said first die pitch, said second die depth being greater than said first die depth, whereby said forward section of said flat die is operable to form a helical first groove in said blank with said first groove having a first groove pitch and a first groove depth corresponding respectively to said first die pitch and said first die depth, said rear section of said flat die being operable to superimpose a second deeper groove over alternate first grooves such that said second deeper groove defines the flanks of a thread with said second deeper groove having a second groove pitch which is twice that of said first groove pitch and with the outer crest ends of said thread having a self-locking center groove defined by said first groove.