Quote:
Originally Posted by Stefan Buda
I made the diameter of the hub 0.05mm smaller than the hole in the mirror, at 20 degrees C. That should be good enough up to at least 80 degrees ambient. You can double check the math and let me know if I made a mistake - the diameter is 73mm and the alloy is 6061. I also have an O-ring on the hub to stop the mirror coming loose when the temperature drops. The amount of compression on the O-rings is based on nothing more than educated guesswork and it can be adjusted later, if needed. I made the axial gap also 0.05, a bit more than it is needed because the front flange is conical rather than spherical, so it does not conform very well to the front of the mirror.
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Thanks for the explanation Stefan. Makes sense. I now realise precision machining and knowing exactly how much play you have goes a long way with potential thermal issues down the road. Packing with cork is a bandaid.