CORE ROD FOR FORMING DYNAMIC PRESSURE GROOVE OF SINTERED BEARING

摘要

PROBLEM TO BE SOLVED: To smoothly remove a core rod from a bearing material and securely form a dynamic pressure groove on the material which has no or less spring- back amount. SOLUTION: The core rod 20A having the groove 21 and a convex projection 22 side by side on its outer circumferential surface is inserted into the cylindrical bearing material 15. A compression of the bearing material 15 in a die opening 5a results in a pressure bonding of the material 15 to the core rod 20A. The bearing surface 11a and the groove 12 are transfered on to the inner circumferential surface of the bearing material 15. The bearing material 15 is released from a die 5, and the core rod 20A is removed from the bearing material 15. The depth of the groove 21 is set to be larger than the amount of radius direction spring-back exhibited by the bearing surface 11a when the outer circumferential surface of the bearing material 15 is released from die 5. The top end corner 22a and the bottom corner 22b of the convex projection 22 are set on an arc-like crosssection.