A hydraulic component is judged by fit accuracy and internal leakage. Cross-drilled passages in the valve body, the cylinder bore and the piston rod surface are the three critical features.
Cast iron and aluminium valve bodies with many intersecting bores that must register accurately. A horizontal machining centre with a rotary table machines all four faces in one setup, holding bore position within ±0.02 mm.
A 45# or 40Cr piston rod with a hard-chrome finish. Turning is followed by cylindrical grinding to Ra0.4 and then chrome plating and polishing, holding straightness to 0.1 mm per metre.
An aluminium pump body whose gear cavity and end faces govern volumetric efficiency. The cavity is bored and the end face milled on a machining centre, holding face flatness to 0.01 mm.
