To provide a screw part with a cut portion for removing painting formed simultaneously with a screw thread by thread rolling, and a manufacturing method therefor.
A shaft part 5 of a screw part raw material formed in series of a head part 3 engaging with a fastening tool is thread-rolled by a thread rolling dies having a crest shaped projecting strip crossing a projecting strip for forming the screw thread on the thread rolling surface, and thereby the screw thread 4 is formed on the shaft part 5 and the cut portion 11 for removing painting is formed near tip of the screw thread 4 in the crossing direction of the screw thread 4. Root diameter of the cut portion 11 is larger than inner diameter of a female screw to be screwed, and thereby lowering of screw thread shearing strength is prevented and accordingly the screw thread 4 on which the cut portion 11 is formed is used as a normal screw thread 4.
|JP08267166||ROLL FORMING METHOD FOR SHAFTLIKE METALLIC PARTS|
|JP63174747||THREAD ROLLING METHOD|
|WO/2004/110669||FORM ROLLING METHOD FOR WORM AND FORM ROLLING DIE FOR THE METHOD|