| 摘要 |
PURPOSE:To improve the pressure resistant strength and extend the life of the forming tooth profile, in a metallic die for forming rack tooth profile, by forming the forming tooth profile in one body in such a way that the tooth crest and the pressing surface of dies form a nearly same plane. CONSTITUTION:Variable ratio type tooth profiles 11 for forming rack teeth projecting from the central part of the pressing surface 10a of a die 10 is formed and, at the same time, a reinforcing wall face 12 having a nearly mountain-like shape united with the forming tooth profile 11 in one body is formed so as to support both end parts of the forming tooth profiles 11. Moreover, they are constituted so that the tooth crest 11a of the forming tooth profile 11 and the upper surface of the reinforcing wall part 12 form a nearly same plane. Furthermore, all the forming tooth profiles 11 and reinforcing wall part 12 are formed by electric discharge machining and a very narrow air vent hole 13 is installed into each bottom land 11b of the forming tooth profiles 11. Therefore, breakage of the forming tooth profile can be prevented. |
