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3) In the DIY CNC world we should look at our forefathers efforts. People like Whitworth and others hand built ( and this was with files and saws for many parts not mechanised tools) their first machines which allowed them with care and skill to build better machines. These machines with care and skill ,,,, result in better etc etc

I totally agree. To really understand accuracy at the highest level, Foundations of Mechanical Accuracy is the book to read: Publications at Moore Tool: Precision Machining Technology, Precision Tools