The idea is to not figure the required thickness to great precision, but to actually make the thing a good deal thicker than minimum thickness. In the 6-8" diameter range .060 inches is more than enough thickness and the extra will allow for some heat sinking as the outer spherical chamber gets extremely hot!
.060 inch wall thickness will allow for easy machining without warping or crushing a thinner shell during tooling.
The above thickness is that which is commonly formed in the extruded hemispheres sold by companies like Braun (See the source lists compiled by the perfesser for the URL.) I would suggest using only stainless steel hemispheres for vacuum fusor chambers.
Richard Hull
Created on Friday, February 23, 2001 5:10 PM EDT by Richard Hull