... fastener 1,Name:Black steel hex screw;black hex screw;steel hex screw 2,For the similar hex screw,what can we do ?(1), ... Ability for the material of this kind of hex screw ... Grinding and polishing,etc,except mirror finish (3),Ability for the tolerance Roundess0.002mmCylindricity0.003mmRoughnessRa0.32Straightness0.01/200mm 3,How ...