spool roundness spool and bore leakage bore geometry spool geometry spool straightness honing accuracy precision honing single pass honing multi pass honing centre joint rotary joint rotary coupling spool replacement monoblock directional control valves excessive torquing or unequal torquing sectional valves hydraulic valve leakage viscosity index poppet type valves hydraulic valve leakage due to oil temperature spool bore clearance geometrical accuracy of poppet and poppet seat par straightness tolerance for spool bore form error circularity cylindricity
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