**1. Introduction**

The cylinder block of the main pump is an important part of the hydraulic system and generates high-pressure hydraulic fluid through relative motion with pistons. At this time, there may occur a seizure problem [1] in which the surface of each component is adhered. And the problem may become a serious problem leading to the shutdown of the entire machine. Therefore, in order to prevent this shutdown, the cylinder block may be fabricated by copper or the copper bushing may be pressed into the cylinder block. Among these two methods, manufacturers mainly use the method of pressing the copper bushing into the cylinder block to reduce the production cost. However, if the proper rate of shrink fit can not be found when pressing the copper bushing, it may lead to disconnection of the bushing or breakage of the cylinder block in the use environment of the machine, resulting in the shutdown of the entire machine, such as seizure. Therefore, in this study, the method of setting the rate of shrink fit analytically was confirmed, and the durability assessment method and the process of the cylinder block considering the residual stress generated after the pressing copper bushing were constructed.
