Decking the surface of the block was next. Visibly, a thick layer of rust had accumulated on the surface and had to be removed. During the automated probing of the surfaces, our lowest deck height came in at 9.0084 inches. Each pass on the CNC removed about 0.004 inch of material, until the surface was as smooth as glass. All in all, our factory block was milled to 9.007 inches.