Eastburn wrote in message ...
I've seen soft Al used - very thin sheet. It doesn't blow through.

Martin

Just in case anyone's curious (totally bored would help) this box is roughly an 8" cube of 14ga mild steel , welded
and with only 5 sides . The top/lid is a bit heavier steel , and I used some 16ga Cu for the gasket. It's joint/rim is 3/8" square
steel
stock brazed to the inside , drilled and tapped 8-32 size in 25 places. Not much of a contact area so the gasket needed to be
stronger than the kaowool , alumina/silica fiber I got, or maybe even the rubber/nitrile I originally got a couple years ago.
I'm really glad someone mentioned using soft metal for the gasket.

Brazing the rim joint in went ok, except for the minor setback of the whole box changing shape from being torched. A brief
pause and puzzled look was followed quickly by a mischievous grin and then a few careful (oh yes!) slams of the box on the floor,
and then a few more to adjust it back the other direction, then a few well placed bashes with the BFH , then a hogging out of the
holes in the gasket and the lid, and ............ THEN those holes all lined up with the holes in the box rim again. Ready to go.

Given that wrapping in aluminum foil alone worked well enough last time I had to do this, the addition of enclosing the Al wrapped
bundle in the box could end up working very well, maybe better than the customer deserves ,lol. Maybe the box all by itself will
do the trick...........

DS