As the other replier mentioned, that won't work. What would work is to mill a knife edge into both the end plate and the can and use off-the-shelf copper Confl

As the other replier mentioned, that won't work. What would work is to mill a knife edge into both the end plate and the can and use off-the-shelf copper Conflat ("CF") gaskets, which are available in a large number of standard sizes. You'd have to work out a way to hold a vacuum in the can while you're tightening the flange though