| 摘要 |
PURPOSE:To obtain a flat surface at high productivity and low cost by forming shallow unevenness on the back of a dial using a die that has unevenness. CONSTITUTION:Unevenness of sandy pattern is formed on the upper surface of an upper die 4 and the sandy pattern is transferred to the back of a dial 3 by pressing the dial with an upper die 1. Unevenness of sandy pattern is formed by plastic deformation of the back 3 of the dial and the surface is worked by graining, sand blasting etc. By making stress of both sides of the dial which is made convex to the face side by residual stress nearly equal, warping of the dial can be corrected. As a compressive force is not required so much in case of a plane, warping can be corrected without any considerable change of the sizes of the center hole and the outer diameter. |
