You could do the same thing as the aluminum tanks but instead of threading
the bolt down you could thread the bolt up from inside the tank and locktite
them as to give you studs from the outside of the tank. I understand the
tank is thin but the threading would only have to hold the bolt in place
from underneath while you put a nut on. Pop rivets would most likely leak.
Can you buy a plastic flange and cover from maybe Ronco-Plastics? Don't put
aluminum in there if you don't have to.
Phil

"NT" wrote in message
...
I want to cut access ports into the top of 2 s/s water tanks. I did
this a while ago on my alum diesel tanks and it was easy to put covers
back on the cutouts - the alum is 1/4" thick and takes a 1/4" fine
thread easily with bolts every 2 inches and a 1/8" neoprene rubber
gasket. The s/s is thinner and won't hold a bolt. I'm thinking of
using s/s pop rivets to hold a 1/4" alum collar with 1/4" fine
threaded holes in the collar around the cutouts in the s/s tanks - and
using 1/4" alum plate covers again. Or I could use s/s plates held in
with alum pop rivets and drill them out when I want to gain access
again in another 5 or 10 years. The tanks are 25 years old and have
not had access before - but we're very careful what we put in them -
so this is not a frequent event.

Any other good options?