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Need some input. Next items up include lapping the guide and starting the cylinder. First question:How smooth does the crosshead guide need to be? It is not a cylinder and has no compression. It is well oiled and just has a sliding part. Do I need to make it mirror flat and smooth? Something less?
Question 2; where do I start on the cylinder and what order to I follow to keep it all square?
IMHO the critical thing is that the cylinder bore will clean up. I would try and ensure this is so by using inside and outside calipers and finding the area of least wall thickness. Then add to this a machining allowance of say 0.010"min. 3/4" - 0.010" (or whatever machining allowance you can get, bigger is better), is where the cylinder centreline will be. Now plug the cylinder with a piece of wood to which each end has a piece of shim brass attached and mark off and "pop" the centres.Using these centres, set up the casting in the mill so they are horizontal and the steam chest face and the cylinder base are as close as possible to right angles then machine the two areas of the base to clean up. You now have a datum face from which the rest of the machining can be carried out.Best RegardsBob