FORMATION METHOD FOR RECEIVER HOLE ROTATABLY RETAINING VARIABLE VANE IN EXHAUST GUIDE ASSEMBLY OF VGS TYPE TURBOCHARGER

摘要

PROBLEM TO BE SOLVED: To provide a new formation method highly precisely providing the bore dimension and inner surface roughness of a receiver hole of a turbine frame rotatably retaining a variable vane without any cutting in a VGS(Variable Geometry System) type turbocharger. SOLUTION: This formation method for the receiver hole 25 is characterized in that a prepared hole 25b further smaller than a prepared hole 25a is opened before opening the prepared hole 25a having a dimension of the diameter or less in its completion state by fine blanking, and when the receiver hole 25 is finished, a steel ball having an almost equal diameter of the receiver hole 25 in its completion state is press-fitted in the prepared hole 25a so as to provide the desired precision of the hole diameter and the surface roughness of the hole inner surface.