Must be something in the air! I'm in the midst of this very same project,
but I'm using old steel carbon dioxide cylinders.
My understanding is that aluminum is very bad for use with an abrasive
chop saw. Apparently it can load up in the blade, cause it to overheat,
and explode. There was a thread about it over on rec.crafts.metalworking
not long ago, the consensus seemed to be that a power mitre saw (as in one
used for wood work) is a better and safer tool to use. A web page I saw
about the "cylinder-to-bell conversion" had the author using a
reciprocating saw (i.e. a Sawzall) to cut the ends off; when I posted
asking for suggestions, I was told everything ranging from plasma cutters
to abrasive cutoff discs as a viable option.
You can often get old cylinders for free from welding supply stores, but it
can take a bit of hunting around. Many are reluctant to give them to you
because they aren't convinced you aren't going to do something bad with a
bottle that has their name stamped on it. I think if you can convince them
of your intentions, however, they're much more relaxed and willing.
If what I have read about the dangers of aluminum in an abrasive chop saw
are correct, then I'd be scared to death to try cutting through a 1" wall
thickness tank since that'd be a total material thickness of 2" at points,
if not wider when cutting through curved sections. There's images posted
of successful cuts done to that thickness using a hand held circular saw
in the metalworking.com drop box, so I'm willing to bet the mitre saw
trick would work. For my cylinders, I'm thinking about constructing a
cylinder holder with wheels that allows the cylinder to be spun with a
motor. Then I'd use a lathe parting tool fixed to the base of the
"cylinder spinner" to cleanly slice the end of the cylinder off. A cheap
single purpose lathe, essentially. Failing that, well, I've been trying
to justify the purchase of a plasma cutter....
Use a standard skil saw with a 7 1/4 inch carbide tipped aluminum cutting
blade. You can even cut it with a wood cutting blade as long as you have
around thirty plus teeth.
Lay out a line around the tank with a felt marker. Set your blade
depth shallow around one inch maximum.
Face shield and gloves are wise. Secure your tank so that it doesn't
rotate. You should be able to cut at least a quarter around before having
I wish I could find some for free. I want to melt the aluminum and cast
with it. They can crush it, smash it, cut a hole it or anything else
they want to do. Give me names and addresses. I'll pickup or pay to ship.
Have you schmoozed your local welding supply shops yet? Although
admittedly, you'll likely have no luck finding aluminum tanks from a
welding shop. Just steel ones. Welding shops (at least the ones around
here) have to pay to have the old cylinders hauled off, so many of them
happily give them away for free because they save money that way. The
smaller, independent shops are usually the most interested in that kind of
savings. Just make sure to try to actually buy some stuff from them now
and again... they're much more willing if they know you're a regular
As for aluminum tanks, I'd think your best bet would be schmoozing the
scuba shops, maybe even posting ads in them and leaving word with the shop
owners that you'll pay people for tanks that have failed visual or hydro.
I'd say check with paintball stores too, but those guys don't bother to
safety check their gear and wouldn't retire a bottle unless it had a crack
large enough to leak gas. Either way, pounding the pavement and making
your face known is the best bet. Leaving a printed up ad at the store
(most stores have a bulletin board for stuff like that) or better yet,
getting the owner to leave your contact info next to the filling station,
would eventually generate a few hits.
Also, what about posting a message now and again to a Usenet scuba group?
Maybe to some web-based boards as well? If you're paying for the tank and
for shipping, I bet you'd get plenty of interested people before too long.