Some background if you will...... I used to work for a machine shop assigned to Texas Instruments. My job was not a machinist at all, but as an assembly tech and/or electronics tech. We were in an equipment development group and were constantly building and re-building and improving semiconductor process machines. When we were doing the assembly work, we often used the machining drawings for the various parts to aid in figuring it all out. I remember reading, almost always as I recall, the tolerances of the parts were +/-.005 I tell that only to ask what is 'usual' or 'reasonable' in a hobby shop? I know if will depend on lots of things, but what is the goal for a hobby guy with a 12" Logan and a bench top mill/drill? I remember being in the shop once, and the owner was asking a new machinist "how close can you work?" to which he replied "All the way to the chuck"