| 摘要 |
PURPOSE:To improve accuracy and stabilize quality by, when planing both surfaces of a thick plate, the side wall part of the concave side of the thick plate is bound while opening the side wall part of the opposite side to the concave part for absorbing excess thickness of a material. CONSTITUTION:The side wall part 4A on the side of a concave surface 3 of an electrode 4 in a shape of an elliptical thick plate is bound by a planing tool 21 while the side wall part 4A on the opposite side to the side of the concave surface 3 is opened. Accordingly, when the electrode 4 in the shape of an elliptical thick plate by the planing tools 20 and 21, the concave surface 3 and the side wall part 4A are bound by the tool 21, while a flow 22A of the materials on the side of the concave surface 3 flows in the direction of the lower hole 5 for keeping the expansion of the concave surface 3. Further, the flow 22B of the materials of the surface 4 on the opposite side to the concave surface 3 flows in the direction of the opened excess absorbing part 23 for positively absorbing the excess thickness. In this way, the expansion of the concave surface 3 is checked while absorbing, the excess thickness of the material not only in the lower hole 5 but also in the excess thickness absorbing part 23 thus being able to obtain an electrode for an electron gun where a highly accurate concave part and the smooth upper and down surfaces are maintained. |
