Machining the Cylinders

The raw castings are tapered on the  flange faces, this because the pattern is split into two halves to mould and tapered to allow the two halves to come out of the sand, this is called draw, because of this there is no flat surface to clamp down for machining, this is where experience plays a part AI never can. an aluminium billet is clamped to the mill bed and two location pockets are bored larger than the finished bores, so that further down the line we can bore finished size through without hitting the pocket. next two plugs are made with the location size on the bottom and a size that will snugly fit into a raw casting on the other, now when we clamp down we have to shim and pack the tapered edges until the bore in the top of the casting is dead above the locations in the bottom, turn over and repeat and after several goes the flanges become parallel and the bores run true, then the first roughing bore,,, ports look fantastic, these castings are much better than the originals and I am very please so far.