| 摘要 |
PURPOSE:To manufacture a flat coil which is increased in thickness of bore in simple steps by opening a reference hole for knocking press at a steel plate, punching by knocking press a slit and pressing to reduce the thickness of the plate. CONSTITUTION:A flat plate 18 of steel having the prescribed thickness is prepared, and a reference hole 20 for knocking press is opened at the plate 18. After slits 21 are punched by knocking press at the plate, the plate is annealed at 500 deg.C for 1hr. Then, the plate 18 having inner diameter D1 of the slits is pressed to sequentially reduce the thickness toward the outer periphery. Subsequently, coil strands are fored by punching the plate, thereby manufacturing a flat coil. |
