Any tank that will withstand 14.7PSI positive pressure(@ sea level) (29.4 PSI absolute)will withstand a vacuum attainable by any compressor you CNC chaps will be using.
I was going to buy a vacuum device for changing my engine oil but they were a bit pricy for a plastic tank and a bit of a hand pump so i modified(or should i say hacked) a 5Ltr pressure sprayer that stood up well on a dry run however when i tried using it on the car the hot oil weakened the plastic and it did collapse, the pucker units are obviously made from a different type of plastic and they have internally moulded rings as per a submarine pressure hull. buddy down the road gave me a small butane tank and i will be converting that shortly. all i am trying to say is if you are using a pressure vessel for vacuum storage you should be fine.
Regards
Mike