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Such as an oval liner inside the segment barrel, or the manufacturing material still hovering in simple die steel quenching, the high speed steel quenching, its wear-resisting performance is limited; or only rely on manual processing on the old conventional common machine: to grind two parallel holes by an internal grinder, that the center distance error is too large; to grind elliptic outside arc by common cylindrical grinder, that not only both arc size cannot guarantee, but also cannot finish the correct size between the cylindrical surface and the flat surface..., the result is the size tolerance, the form and position tolerances cannot up to standard... .
