The macroscopic and microcosmic fracture surface investigation showed that the crack start at the chamfer edge of a locating hole and the patterns of fracture surface were compound with stress corrosion and fatigue.

Alignment of the drill and the center of PCB standard hole in PCB location hole drilling machine is the key,which determines processing precision of the whole system.

According some molds repair need location by location hole,because time cost long that adjust location hole location in CNC machine,and location accuracy is low.

Method of machining pin holes of headstock;