Method of verifying the quality of a press-fit operation

Abstract

A system for verifying the quality of a pressing operation of a press-fit part onto a receiving portion of a receiving assembly. The system is applicable to the installation of a bearing cup onto a shaft, or a valve seat into a cylinder head. A probe measures a predetermined dimension of the press-fit part to establish a first measurement value. In the case of a valve seat installed a receiving pocket of a cylinder head, a measuring probe is inserted into the receiving pocket of the cylinder head to measure its depth. The depth is recorded as a second measurement value. The valve seat is then pressed into the pocket, and the residual depth is measured to determine the distance between the outermost surface of the pressed in valve seat and the outer surface of the receiving pocket. A computation compares the depth of the pocket against the thickness of the valve seat to determine a difference which is then compared to the residual depth. During pressing, the hydraulic pressing force is maintained while an impulse force, similar to a hammer blow, is applied to the valve seats to ensure proper seating. The use of a hammer blow obviates the need for excessive hydraulic forces which may damage cylinder head castings. Also, the hydraulic pressing force is monitored over a predetermined distance of insertion of the press-fit part to determine the quality of the interference fit between the press-fit part and the receiving portion of the receiving assembly.