What you need to do is to find the expansion Coefficient of expansion of everything that you`re going to use and make sure that the brass or aluminum never gets to be smaller than the glass. If you figure on the glass at about 5x10^6/deg.C (the crown) and aluminum at about1.23x10^5/deg.F or brass at 9x10^6/deg.F.
Brass has a bit better expansion coefficient and you should probably consider rolling a cylinder and welding it together or making a casting if you find the cost of a solid block of the stuff to be a bit high.
The temp you should use as a lower end for static temp should be about a -50C temp at which there should be about .0005"-.001" clearance between the glass and the metal at a minimum.
When measuring the cell, don`t forget to let it cool from the lathe or mill operation. It`s easy to change the temp of a piece of metal by as much as 100F real fast - that`s about a thousandth of an inch right there!