In this regard ballizing may be the only means of producing exact size holes which can have no corner break and must also be burr free. Mated holes having slight elbow or s-bends can be finished in one pass and interrupted areas such as cross holes recesses do not create problems. Nor does ballizing throw burrs or chips into them as could occur if the piece were broached reamed or honed. The method applies to metallic materials, and they should have homogenous structure. If there are hard spots in castings, ballizing will not be carried out uniformly, any of the ferrous, non ferrous or stainless screw stocks can be processed with good results. Parts can also be ballized after case hardening or plating up to but not including the hard chromium level. The work piece should not be harder than 45 RC. Ball should have more hardness than work piece.