What is the maximum tolerance for a DIY Machine ?!

[Muzzer]

That's a wordy response (can't be bothered to quote it) that appears to make some sense on the face of it until you scratch a micron below the surface and twig that there are some rather big dimensions missing.

Unless you regulate the temperature of the table, frame and ballscrews, the coefficient of expansion becomes a significant issue. So if (like me) you have worked with suppliers that genuinely have 1um machines, you will see measures to address it. The machines have extensive heating and cooling circuits running continually and they are housed in air conditioned rooms. They are set up very painstakingly by experts who know what they are doing.

Similarly, a machine that won't deflect by more than a total of +/- 0.5um under load ("within 1um") would require a truly impressive level of rigidity. To demonstrate willy waving levels of accuracy outside of the pub, you need to machine a part under realistic conditions and measure the results - over several samples, ideally in several locations.

I doubt if any of us could even set up a machine to anything like the required level of accuracy before we even set up the work.

For an insight into what you need to get to the micron level, here's a mate of mine describing some of the issues. About half way in he's discussing 1um machines:


My big Japanese machine was originally designed and manufactured as a proper CNC machine with HSK bearings and ballscrews with a published achievable overall accuracy of 10um. Having said that, you'd need to allow for wear and adjust it carefully to get anywhere near that. I may achieve perhaps 25um on a good day and be happy enough with it. I'm not making watch or optical parts on it.

What could you possibly make that requires 1um tolerances? But above all - how would you measure them?