Again, a cutting tool that removes material will tear the material. High and low, mountain range like surface that only a microscope could see. Burnish that surface is much like running the cutting tool backward. It lays the surface to a much more consistant plane. Because this is a soft material and press fit into a bore, the insde diameter closes up a bit. Burnishng brings all bushings to same size I.D. and finish regardless how much variance is in the block bores or in the bushings O.D.
