Non orbicular screw, rolling process manner null of rolling dies and non orbicular screw for non orbicular screw

摘要

PURPOSE:To manufacture a non-circle screw by thread rolling process with a simple dies shape by preparing a screw whose diameter at its top and sectional shape at its top are substantially constant around an axis center, and synchronizing measurement varying period from the center to a bottom which is small at expansion parts and large at run off parts to that from the center to the top. CONSTITUTION:Radius measurement r1 from a center O to a thread top 16 of a screw thread 12 is varied by 120 degrees, while expansion parts 18 and roll off parts 20 are alternately formed. Diameter measurement from the thread top 16 passing through the center O is substantially constant, while sectional shape taken along each part in the direction of the center O is substantially constant. Radius measurement r2 from the center O to a bottom 14 is set smaller at the expansion parts 18, and larger at the run off parts 20, by varying synchronously to the varying period of the radious measurement r1. The height from the bottom 14 to the top 16 of the thread screw 12 is relatively high, while the height at the run off part 20 is relatively low. A screw with high accuracy is manufactured by thread rolling process with a low cost, by using a screw member whose sectional area is circle and thread rolling dies which are easily manufactured through cutting process.